35 results on '"Hampp N"'
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2. Single- and two-photon absorption induced photocleavage of dimeric coumarin linkers: Therapeutic versus passive photocleavage in ophthalmologic applications
- Author
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Kim, H.-C., Härtner, S., and Hampp, N.
- Published
- 2008
- Full Text
- View/download PDF
3. Kinetic optimization of bacteriorhodopsin films for holographic interferometry
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Seitz, A. and Hampp, N.
- Subjects
Bacteriorhodopsin -- Research ,Holographic interferometry -- Materials ,Excited state chemistry -- Research ,Chemicals, plastics and rubber industries - Abstract
A proton-diffusion-limited, two-state model (PDL2 model) for bacteriorhodopsin is introduced that allows modeling mathematically the optical excitation and thermal relaxation processes for both high and low humidities in bacteriorhodopsin films. Kinetically optimized bacteriorhodopsin films yield a more-than-30-fold improvement of sensitivity in holographic interferometry compared to dry bacteriorhodopsin films.
- Published
- 2000
4. Diverse Applications of Nanomedicine
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Pelaz B., Alexiou C., Alvarez-Puebla R., Alves F., Andrews A., Ashraf S., Balogh L., Ballerini L., Bestetti A., Brendel C., Bosi S., Carril M., Chan W., Chen C., Chen X., Cheng Z., Cui D., Du J., Dullin C., Escudero A., Feliu N., Gao M., George M., Gogotsi Y., Grünweller A., Gu Z., Halas N., Hampp N., Hartmann R., Hersam M., Hunziker P., Jian J., Jiang X., Jungebluth P., Kadhiresan P., Kataoka K., Khademhosseini A., Kopeček J., Kotov N., Krug H., Lee D., Lehr C., Leong K., Liang X., Ling Lim M., Liz-Marzán L., Ma X., Macchiarini P., Meng H., Möhwald H., Mulvaney P., Nel A., Nie S., Nordlander P., Okano T., Oliveira J., Park T., Penner R., Prato M., Puntes V., Rotello V., Samarakoon A., Schaak R., Shen Y., Sjöqvist S., Skirtach A., Soliman M., Stevens M., Sung H., Tang B., Tietze R., Udugama B., VanEpps J., Weil T., and Weiss P.
- Abstract
© 2017 American Chemical Society.The design and use of materials in the nanoscale size range for addressing medical and health-related issues continues to receive increasing interest. Research in nanomedicine spans a multitude of areas, including drug delivery, vaccine development, antibacterial, diagnosis and imaging tools, wearable devices, implants, high-throughput screening platforms, etc. using biological, nonbiological, biomimetic, or hybrid materials. Many of these developments are starting to be translated into viable clinical products. Here, we provide an overview of recent developments in nanomedicine and highlight the current challenges and upcoming opportunities for the field and translation to the clinic.
- Published
- 2017
5. Diverse Applications of Nanomedicine
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Alvarez-Puebla, R.A., Pelaz, B., Alexiou, C., Alves, F., Andrews, A.M., Ashraf, S., Balogh, L.P., Ballerini, L., Bestetti, A., Brendel, C., Bosi, S., Carril, M., Chan, W.C.W., Chen, C., Chen, X., Cheng, Z., Cui, D., Du, J., Dullin, C., Escudero, A., Feliu, N., Gao, M., George, M., Gogotsi, Y., Grünweller, A., Gu, Z., Halas, N.J., Hampp, N., Hartmann, R.K., Hersam, M.C., Hunziker, P., Grupo de Plasmonica y Ultradetección, Química Física i Inorgànica, and Universitat Rovira i Virgili
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Chemistry ,Biomimetics ,Nanomedicina ,Biological implants ,1936-0851 ,Hybrid materials ,Química ,Biomimètica - Abstract
The design and use of materials in the nanoscale size range for addressing medical and health-related issues continues to receive increasing interest. Research in nanomedicine spans a multitude of areas, including drug delivery, vaccine development, antibacterial, diagnosis and imaging tools, wearable devices, implants, high-throughput screening platforms, etc. using biological, nonbiological, biomimetic, or hybrid materials. Many of these developments are starting to be translated into viable clinical products. Here, we provide an overview of recent developments in nanomedicine and highlight the current challenges and upcoming opportunities for the field and translation to the clinic.
- Published
- 2017
- Full Text
- View/download PDF
6. Basic Physicochemical Properties of Polyethylene Glycol Coated Gold Nanoparticles that Determine Their Interaction with Cells
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Del Pino P., Yang F., Pelaz B., Zhang Q., Kantner K., Hartmann R., Martinez De Baroja N., Gallego M., Möller M., Manshian B.B., Soenen S.J., Riedel R., Hampp N., and Parak W.J.
- Abstract
A homologous nanoparticle library was synthesized in which gold nanoparticles were coated with polyethylene glycol, whereby the diameter of the gold cores, as well as the thickness of the shell of polyethylene glycol, was varied. Basic physicochemical parameters of this two-dimensional nanoparticle library, such as size, ?-potential, hydrophilicity, elasticity, and catalytic activity,were determined. Cell uptake of selected nanoparticles with equal size yet varying thickness of the polymer shell and their effect on basic structural and functional cell parameters was determined. Data indicates that thinner, more hydrophilic coatings, combined with the partial functionalization with quaternary ammonium cations, result in a more efficient uptake, which relates to significant effects on structural and functional cell parameters. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
- Published
- 2016
7. Photoinduzierte Wirkstoff- und Farbstofffreisetzung aus hydrophilen Polymeren
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Busch, Annegret Philippine and Hampp, N. (Prof. Dr.)
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ddc:540 ,Chemie ,Hydrophile Polymere ,Polymere, Wirkstofffreisetzung ,Zwei-Photonen-Absorption ,Polymeres , drug delivery ,PCO ,Grauer Star ,Chemistry and allied sciences - Abstract
Katarakt (Grauer Star) ist eine Erkrankung, die durch eine Dysfunktion des Metabolismus im Auge hervorgerufen wird und in Folge dessen zu einer Trübung der Linse führt [1, 2]. Über 20 Millionen Menschen haben durch diese Erkrankung ihre Sehkraft verloren [3, 4]. Die wesentlichste Behandlungsmethode umfasst die operative Entfernung der natürlichen Linse, die so genannte Extrakapsuläre Katarakt Extraktion (ECCE) und die darauffolgende Implantation einer polymeren Intraokularlinse (IOL) [5, 6]. Die am häufigsten vorkommende Komplikation, die in den ersten 3 bis 5 Jahren auftritt und bei 50 % der Patienten beobachtet wird, ist das erneute Eintrüben der IOL, welches als sekundärer Katarakt (Nachstar, oder Posterior Capsule Opacification, PCO) bezeichnet wird [7–10]. Die einzige Behandlungsmethode ist die invasive chirurgische Laserkapsulotomie, bei der der Kapselsack thermisch irreversibel zerstört wird [11]. Die Pathogenese der PCO ist darauf zurückzuführen, dass bei der ECCE Linsenepithelzellen im hinteren Kapselsack verbleiben und durch den Eingriff stark proliferierendes Narbengewebe zurückbleibt [12, 13], was zu einer Eintrübung der polymeren Linse führen kann. Diese Arbeit fokussiert sich auf die Entwicklung polymer basierter Drug-Delivery-Systeme, die auf Basis eines photoinduzierten Stimulus aktiviert werden und infolge dessen den Wirkstoff freisetzen. Der verwendete Wirkstoff, ist bereits durch entsprechende Anwendung zur Behandlung der PCO etabliert [14–18], wobei innovativ das Drug-Delivery- System 5-Fluoruracil (5-FU) als zytotoxisch wirksames Agens enthält. Hierfür bildet 5-FU durch die [2+2]-Cycloadditionsreaktion nach Woodward-Hoffmann mit einen entsprechend Linker Kreuzdimere oder Homodimere, die an das Polymerrückgrat kovalent gebunden werden können. Dabei wird das Dimer durch photoinduzierte Bestrahlung über eine [2+2]-Cycloreversionsreaktion vom Linker gespalten und durch Diffusion aus der polymeren Matrix freigesetzt. Die [2+2]-Cycloreversionsreaktion kann entweder durch einen Ein-Photon- Absorptionsprozess (SPA) unterhalb von 300 nm, oder durch einen Zwei-Photonen- Prozess (TPA) oberhalb von 300 nm induziert werden. In dieser Arbeit werden Lichtquellen verwendet, die bei 266 nm (SPA) und Licht im Bereich von 532 nm (TPA) emittieren. In früheren Arbeiten wurde Coumarin als Linker-Molekül verwendet [13, 19]. Dieses besitzt hervorragende photochemische Eigenschaften, ist aber gegenüber Hydrolysereaktionen instabil, was wiederum die Reinigung der Kreuzdimere erschwert [20]. Aufgrund dessen wurden als alternative Linker-Strukturen Chalkon, H5FU (Heptanoyl- 5-Fluoruracil), BCA (4-methyl-2-oxo-2H-Benzo[h]chromen-8-yl acetat) verwendet. Sechs wesentliche Aspekte bezüglich der Drug-Delivery-Systeme werden in dieser Arbeit untersucht und vorgestellt: 1. Die Etablierung der Synthese der Kreuz- und Homodimere. 2. Charakterisierung der SPA- und TPA-induzierten Spaltungsreaktionen. 3. Etablierung eines polymeren Systems, welches mit einem Kreuz- oder Homodimer funktionalisiert wird und zusätzlich nach DIN ISO Norm mit einem UV-Absorber copolymerisiert wird. 4. Charakterisierung der Freisetzungskinetik des Wirkstoffs aus dem Polymer. 5. Untersuchung der Licht- und thermischen Stabilität der Polymere. 6. Validierung der Reproduzierbarkeit der photoinduzierten Wirkstofffreisetzung aus dem Polymer. Die Entwicklung von fluoreszierenden Arzneiformen wird schon seit Längerem erfolgreich angewendet, um es z.B. für bildgebende Methoden zu nutzen oder Freisetzungsprofile aus einem Drug-Release-System besser darzustellen, bzw. mögliche physiologische Diffusionsprozesse oder Erkrankungen besser untersuchen zu können [21, 22]. In dieser Arbeit wird ein fluoreszierendes Polymersystem vorgestellt, welches basierend auf der Vorschrift der Synthese des Chalkon-H5FU (CFKD)-Polymers erzeugt wurde [23]. Als Linker wurde Chalkon und BCA (8-acetoxy-4- methyl-2H-Benzo[h]chromen- 2-on) als fluoreszierender Farbstoff verwendet. Wie bei dem CFKD-Polymer wurde die Freisetzung des Fluoreszenzfarbstoffs durch Ein- Photon-Absorptions- oder Zwei-Photonen-Absorptions-Prozesse induziert. Um ein Profil von dem Diffusionsprozess zu erhalten, wurde die Wirkstoffdiffusion aus dem Polymer nach einer Laser-getriggerten Aktivierung in situ visuell festgehalten. Neben der [2+2]-Cycloaddition nach Woodward-Hoffmann entstehen bei der photochemisch induzierten Synthese mit dem Rayonet-Reaktor Oxetane zwischen 5-FU und dem Photosensibilisator Benzophenon durch eine [2+2]-Cycloaddition nach Paternò-Büchi. Diese wurden eingehend untersucht und die SPA-induzierte Spaltungsreaktion analysiert. Da 5-FU ein zytotoxisch wirkendes Agens ist [24], wurde ein Wirkstoff gewählt, der aufgrund seines Molekülgerüsts durch photoinduzierte [2+2]-Cycloaddition einen Cyclobutanring mit einem Linker ausbildet und zum anderen bereits bei der Behandlung der PCO erprobt wurde. Hierfür wurde Tranilast verwendet und erfolgreich ein Kreuzdimer mit dem Linker-Molekül Coumarin via Cycloadditionsreaktion erzeugt.
- Published
- 2015
8. BR-D96N光致变色动力学光谱及中间态
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Hampp N.
- Subjects
General Medicine ,General Chemistry - Published
- 2002
9. Thermal [2 + 2] Cycloreversion of a Cyclobutane Moiety via a Biradical Reaction
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Liese, J., primary and Hampp, N., additional
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- 2011
- Full Text
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10. Poly(methylene blue)-modified thick-film gold electrodes for the electrocatalytic oxidation of NADH and their application in glucose biosensors
- Author
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Silber, A, primary, Hampp, N, additional, and Schuhmann, W, additional
- Published
- 1996
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11. Functional dyes from nature: Potentials for technical applications
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Hampp, N., primary and Silber, A., additional
- Published
- 1996
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12. Photochemical conversion of the O-intermediate to 9-cis-retinal-containing products in bacteriorhodopsin films
- Author
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Popp, A., primary, Wolperdinger, M., additional, Hampp, N., additional, Brüchle, C., additional, and Oesterhelt, D., additional
- Published
- 1993
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13. The cDNA clone for strictosidine synthase from Rauvolfia serpentinaDNA sequence determination and expression in Escherichia coli
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Kutchan, T.M., Hampp, N., Lottspeich, F., Beyreuther, K., and Zenk, M.H.
- Abstract
The cDNA clone for strictosidine synthase, the enzyme which catalyzes the stereospecific condensation of tryptamine with secologanin to form the key intermediate in indole alkaloid biosynthesis, strictosidine, has been identified with a synthetic oligodeoxynucleotide hybridization probe in a λgt11 cDNA library of cultured cells of Rauvolfia serpentina. The DNA has been sequenced, revealing an open reading frame of 1032 base pairs encoding 344 amino acids. The sequence of 60 nucleotides in the 5′-flanking region has been determined by primer extension analysis. The encoded protein has been expressed in E. coliDH5 as detected by immunoblotting of protein extracts with antibodies raised against the native enzyme.
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- 1988
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14. The cDNA clone for strictosidine synthase from Rauvolfia serpentina DNA sequence determination and expression in Escherichia coli
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Kutchan, T.M., primary, Hampp, N., additional, Lottspeich, F., additional, Beyreuther, K., additional, and Zenk, M.H., additional
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- 1988
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15. Sandwich enzyme membranes for amperometric multi-biosensor applications: improvement of linearity and reduction of chemical cross-talk
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Popp, J., Silber, A., Bräuchle, C., and Hampp, N.
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- 1995
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16. Comparison of potentiometric enzyme sensors for urea and penicillin-G: differential thick-film sensors versus classical electrodes
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Eppelsheim, C., Aubeck, R., and Hampp, N.
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- 1995
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17. Laser kontrollierte Zykloaddition und Reversion von Kreuzdimeren
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Behrendt, Philipp and Hampp, N. (Prof. Dr.)
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Dimer ,Zykloaddition, Zykloreversion ,Laser, cylcoaddition ,Laser, Zykloaddition ,ddc:540 ,Chemie ,Chemistry and allied sciences ,Laser, cylcoaddition, cycloreversion, dimer ,Laser, Zykloaddition, Zykloreversion, Dimer ,2013 ,Laser ,Chemistry and allied sciences -- Chemie ,Zykloreversion ,cycloreversion - Abstract
To treat cataract, the major cause for blindness, the original eye lenses are removed and artificial lenses are implanted. With this procedure, the side effect of secondary cataract has become of interest to research. The treatment thereof calls for the development of a molecular integrated and covalently bound photolinker system for the controlled release of cytostatica. To load the polymeric intraocular lens, crossdimers of the photolinker coumarin together with the antimetabolite 5-fluorouracil are synthesized. After incorporation in the lens, the specific release via cycloreversion then is best realized with a two photon process which offers high spatial resolution, and which uses visual light to pass the cornea. The backbone of this work is the light driven, intermolecular and coumarin based crossdimerization and its reversion. To achieve this goal, the options given for photoreactions, like set up, substrates, and excitation are considered and their variables are evaluated. The choice of photolinker is narrowed down and a comparison between these absorbing substrates provided by kinetic measurements. A list of possible molecule types of the non-absorbing reaction partner for the crossdimerization is given, by which a huge variety of crossdimers can be build up. The commonly used lamp based light sources such as a Rayonet reactor are compared to the novel favored laser system. The sun is also utilized to project a large scale, energetically economic process. The laser, as a new tool for molecule synthesis, exhibits improvements to cycloaddition reactions in a number of experiments. Additives like sensitizers and triplet promoters are shown to be unnecessary with this high energy illumination. The laser fueled set up is analyzed and the photon distribution, together with the photon flux, is determined to be crucial. With parameters attuned to the lifetime of the excited state, the diffusion controlled dimerization reaction can be controlled and steered towards the principal generation of crossdimer. The reversibility of the dimerization reaction caused both by heat and light is demonstrated. Thermal cleavage is used in addition to laser synthesis in the specialization towards exclusive crossdimer synthesis. Light is primarily used in the customary laser based two photon absorption for specific single and two bond cleavage. Hereby the ever more popular two photon cycloreversion is measured of individual stereoisomers. All methods, developed for the dimer generation, belong to the general concept for the extended application of photoreaction in synthesis. Additional examples in form of a sequential photoreaction and photoremovable protective groups are presented accordingly., Um Katarakt, was die häufigste Ursache für Blindheit darstellt, zu behandeln werden die ursprünglichen Augenlinsen entfernt und durch künstliche ersetzt. Wegen dieser Behandlung wurde der Nebeneffekte des sekundären Katarakts von Interesse für die Forschung. Die diesbezügliche Behandlung benötigt die Entwicklung eines kovalent gebundenen, auf molekularer Ebene integrierten und licht-gesteuerten Freisetzungssystems für Zytostatika. Für die Beladung der polymeren, interokularen Linsen werden dazu Kreuzdimere des fotoaktiven Kumarins mit dem Antimetaboliten 5-Fluoruracil synthetisiert. Nach dem Einbringen in die Linse, wird die dosierbare Freisetzung mittels Zykloreversion am besten gesteuert durch einen örtlich hochaufgelösten Zweiphotonenprozess, welcher sichtbares Licht verwendet um die Kornea zu passieren. Rückgrat dieser Dissertation ist die lichtgetriebene, intermolekulare, auf Kumarin basierende Kreuzdimerisierung und dessen Reversion. Um dieses Ziel zu erlangen wurden die Möglichkeiten an Aufbauten, Substraten und Anregungen verglichen und deren Variablen evaluiert. Die Auswahl an absorbierenden Linkern wird eingeengt und eine Vergleichbarkeit über kinetische Messungen gegeben. Eine Liste an möglichen Molekültypen, so wie der nicht absorbierenden Reaktionspartner, für die Kreuzdimerisierung wird angeführt, mit derer sich eine große Menge möglicher Kreuzdimere herstellen lässt. Die herkömmlichen lampenbasierenden Lichtquellen, wie der Rondellreaktor, werden mit dem neuen Lasersystem verglichen. Sonnenlicht wird außerdem verwendet um einen energieökonomischen Großmaßstabsansatz zu veranschaulichen. Der Laser, als ein neues Instrument für die Molekülsynthese, zeigt in einer Reihe an Experimenten Verbesserungen. Zusätze, wie Sensibilisatoren und Triplettpromotoren, zeigen sich als unnötig für solch eine hochenergetische Bestrahlung. Der lasergetriebene Aufbau wird untersucht wobei sich der Photonenfluss und Photonenverteilung als Kernpunkte heraus stellen. Mit den richtigen Parametern kann diese diffusionsabhängige Reaktion, welche zusätzlich abhängig von der Lebensdauer des angeregten Zustandes ist, kontrolliert und gesteuert werden, um vornehmlich Kreuzdimer zu produzieren. Die Umkehrbarkeit dieser Dimerisierungsreaktion wird sowohl mit Licht als auch mit Hitze demonstriert. Thermische Zersetzung wird dabei, zusätzlich zur Lasersynthese, für die Spezialisierung hingehend zur ausschließlichen Kreuzdimerisierung verwendet. Licht hingegen wird hauptsächlich in der bekannten Zweiphotonenabsorption für den selektive ein- und zweifach Bindungsbruch eingesetzt. Dabei wird die, immer beliebtere, Zweiphotonen-zykloreversion für individuelle Stereoisomere gemessen. Alle Methoden, welche für die Dimererzeugung entwickelt wurden, gehören zu dem übergeordneten Konzept zur erweiterten Anwendung lichtgetriebener Reaktionen in der Synthese. Zusätzliche Beispiele in der Form von aneinandergereihten Lichtreaktionen und lichtentfernbaren Schutzgruppen sind diesbezüglich angeführt.
- Published
- 2013
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18. Novel polymeric materials for ophthalmological implants: photo-induced change in refractive index and high refractive index materials with concomitantly UV absorbing chromophores
- Author
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Schraub, Martin and Hampp, N. (Prof. Dr.)
- Subjects
Cumarin ,Stilben , Chalkon ,Intraocularlinsen ,Grauer Star ,ddc:540 ,Photochemie ,Chemie ,intraocular lens ,Chemistry and allied sciences ,Chalkon ,Dimerisierung ,Stilben ,Polymere ,2011 ,Chemistry and allied sciences -- Chemie - Abstract
Durch die enormen Fortschritte in der Medizin steigt die durchschnittliche Lebenserwartung der Menschen kontinuierlich. Das Durchschnittsalter eines Mannes beträgt heute bereits über 75 Jahre, das einer Frau über 80 Jahre. Mit zunehmendem Alter der Bevölkerung steigt die Bedeutung von Alterskrankheiten rapide. Die Katarakt (cataracta senilis) oder der „Graue Star“ ist eine Alterskrankheit von der viele Menschen betroffen sind. Im Verlauf der Krankheit trübt sich die ansonsten klare Augenlinse. Diese Trübung steigert sich bis zum vollständigen Verlust der Sehkraft. Katarakt ist mittlerweile weltweit die häufigste Ursache für Blindheit. Die Ursachen der Entstehung von Katarakt sind nicht bis ins letzte Detail geklärt, aber es gibt Faktoren, wie z.B. hohe UV Exposition, die die Progression der Krankheit fördern. Eine medikamentöse Behandlung der Katarakt ist trotz der fortschrittlichen Medizin bis jetzt nicht realisiert. Die einzige Möglichkeit den Grauen Star zu therapieren, ist die getrübte Linse durch einen chirurgischen Eingriff zu explantieren und eine künstliche Linse zu implantieren. Diese künstlichen Linsen, sogenannte Intraokularlinsen (IOL) werden seit über 60 Jahren implantiert. Die Katarakt-Operation ist heute eine der am Menschen häufigsten durchgeführten Operationen. Es gab bis zu diesem Zeitpunkt zahlreiche Innovationen auf dem Gebiet der IOL-Herstellung, jedoch ist ein Hauptproblem der Katarakt-Chirurgie nachwievor die suboptimale Sehkraft nach der IOL-Implantation. Dieses Problem ist individuellen postoperativen Effekten geschuldet und in der Regel nicht vorhersehbar. Über 80% aller Patienten haben nach der IOL-Implantation eine Sehschärfeverlust im Bereich von ± 2 Dioptrien. Ein Hauptziel dieser Arbeit ist es, moderne Materialien für die IOL-Herstellung zu synthetisieren, mit denen es möglich ist, postoperativ und non-invasiv die Brechkraft der IOL zu ändern. Erreicht werden soll dieses Ziel durch Verwendung von photochemisch aktiven Gruppen wie Cumarinen, Stilbenen und Chalkonen. Diese Substanzklassen reagieren auf bestimmte Wellenlängen indem sie in einer [2π+2π]-Cycloaddition dimerisieren. Durch die Dimerisierung wird das konjugierte π-Elektronensystem verkürzt, dadurch wiederum ändert sich die Polarisierbarkeit des Moleküls. Weiterführende theoretische Betrachtungen zeigen, dass der Brechungsindex eines Materials von der Polarisierbarkeit abhängt. Somit ist es möglich, durch photochemische Manipulation auf mikroskopischer Ebene, makroskopisch den Brechungsindex eines Materials zu ändern. Im Rahmen dieser Arbeit wurde eine Reihe von Polymeren erfolgreich synthetisiert und photochemisch charakterisiert, mit denen es möglich ist, die Brechkraft einer IOL photochemisch um über drei Dioptrien zu ändern. Aus ausgewählten Polymeren wurden zunächst Polymerplatten hergestellt und aus diesen wiederum wurden Linsenprototypen gefertigt. Dadurch konnte gezeigt werden, dass diese neuen Materialien mit industriellen Methoden bearbeitbar sind. Das zweite Ziel dieser Arbeit war die Erforschung von hochbrechenden Materialien, das heißt mit einem Brechungsindex größer als n = 1,60, für den Einsatz als Material für phake Intraokularlinsen. Phake Intraokularlinsen (PIOL) sind sehr dünne Linsen, im Fachjargon auch als Kontaktlinse für „in das Auge“ bekannt. Da diese Linsen sehr dünn sind, ist ein hoher Brechungsindex essentiell, da sonst keine optische Wirkung erreicht werden würde. Zudem sollten Materialien im Rahmen dieser Forschung als Besonderheit gleichzeitig UV absorbierend sein, ohne einen zusätzlichen UV-Absorber zu verwenden. Es wurden zwei Derivate des Cumarins synthetisiert, aus denen methacrylat-basierte Polymere mit einem Brechungsindex von n = 1,61 hergestellt wurden. UV/Vis spektroskopische Messungen zeigten, dass diese Cumarinderivate im Bereich eines typischen UV-Absorbers absorbieren. Photochemische Untersuchungen zeigten, dass diese Cumarinderivate im Gegensatz zu den in Arbeitspaket eins synthetisierten Cumarinderivaten nicht photochemisch dimerisieren und somit der Brechungsindex nicht variiert werden kann., Over the past decades medicine evolved continuously, which can clearly be seen in the rising average of life expectancy. But as the population gets older and older the number of old-age diseases increases. Cataract (cataracta senilis) is such an old-age disease and worldwide the number one reason for blindness. Cataract is a tanning of the natural lens severely affecting vision. Up to date explanation of the natural eye lens and its replacement by a polymeric intraocular lens (IOL) is the only way to treat cataract. After implantation of an IOL most of the patients do not achieve optimum vision. Reasons for this suboptimal result are individual effects e.g. wound healing. These effects are not fully predictable. Most of the patients have to wear viewing aids. Approximately 80% of all patients are in a range of ± 1 diopter around the optimum vision. Our aim is to supply polymers which enable post-operative tuning of the refractive properties of the implanted IOL made of these new polymers in order to compensate for all remaining imperfections. These polymers are based on a poly methacrylate backbone and incorporate coumarin, stilbene and chalcone derivatives as side groups which can undergo a [2π+2π] - dimerization reaction. Through dimerization the conjugated π-electron system is decreased. As a direct consequence the molecules polarizability and relative permittivity are also affected. A closer look at the theory of velocity of light shows the direct relation of the refractive index n and the molecules relative permittivity. In the presented work various polymers containing coumarins, stilbenes and chalcones were successfully synthesized and photo chemically characterized. These polymers show significant changes in refractive index upon irradiation of up to 3 diopters. Selected polymers were used to manufacture polymeric plates which were processed to prototypes. These prototypes could be machined by standard operating procedures used in the industry. The second working package was to investigate new polymeric materials for high refractive index materials used for phacic intraocular lenses (PIOL). PIOL´s are used as an additional support in ophthalmic surgery. PIOL´s are very thin (0.1 mm in thickness) and have to be highly refractive. The desired refractive index should be bigger than n = 1.60. As a specialty the polymer should simultaneously absorb in the UV region and act as an UV absorber without adding one. Two coumarin derivatives were therefore successfully synthesized. Methacrylate based polymers with these new coumarin derivatives showed refractive indices of n = 1.61. Furthermore these molecules absorb in the UV region enabling them to act as an UV absorber. In contradiction to previously synthesized polymers containing coumarin in the side chain of the polymer these molecules do not dimerize under irradiation.
- Published
- 2013
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- View/download PDF
19. Aufbau nanoskopischer Hybridstrukturen am Beispiel von MrgA und Purpurmembran
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Schönafinger, Andreas and Hampp, N. (Prof. Dr.)
- Subjects
Purplemembrane ,Nano hybrid ,ddc:540 ,Chemie ,Chemistry and allied sciences ,Chemistry and allied sciences -- Chemie ,Purpurmembran ,MrgA ,2008 - Abstract
Biological compounds display a rich variety of features which have implications for technical applications, such as catalysis and selective high affinity. The utility of biological compounds as building blocks for device fabrication, however, is severely hampered by two general restrictions: Firstly, biomolecules tend to lose their native biological integrity and function in other than near-physiological conditions, and they usually have poor long term stabilities. Secondly, many of the well estabished state-of-the-art techniques for building up nanostructured surfaces, such as methods used in silicon wafer based semiconductor fabrication, are not suited for the procession of biological building blocks. In order to tie in with these techniques new assembly strategies have to be implemented, such as bottom-up and templated self-assembly strategies. In this work, techniques to overcome these problems were elaborated in the context of two biological model substances: MrgA and purple membranes. Firstly, the dodecameric iron storage protein MrgA was used to develop methods for generating nanostructured surfaces. By a three-step procedure (adsorption from an incubation solution, rinsing to remove excess salt and protein, and drying), dry monolayers of MrgA on various solid substrates were constructed, and their morphologies were analyzed by means of AFM. Hexagonal, two-dimensional crystalline monolayers on hydrophilic surfaces were obtained upon adsorption under aqueous conditions at low supersaturation. It was found that the formation of such two-dimensional crystals is heavily dependent on the pH and the salinity of the incubation solution as well as on the surface properties. The correlation of surface coverage with substrate charge, ionic strength, and pH indicated the dominance of electrostatic effects in adsorption – due to the competing interactions of intermolecular repulsion and protein-substrate attraction. In this work, it is shown that adsorption of MrgA leading to the formation of two-dimensional crystals is favoured under conditions close to the isoelectric point of the biomolecule. These results were used to further develop techniques for the guided self-assembly of MrgA nanostructures. To this end, substrates which are nanostructured in regard of their affinities to the protein were generated on template-stripped gold by micro-contact printing of functionalized thiols. Taking advantage of the fine-tunable affinity and a phenomenon usually regarded as an undesired artifact in micro-contact printing, the edge-dominant ink transfer, the surface-templated self-assembly of MrgA in nanometer patterns was achieved. In addition, the protein-shell was removed by pyrolysis in a low pressure oxygen plasma. After this procedure, the metaloxide cores of the holo-protein were found to remain at the location where the proteins had originally been adsorbed on the surface. Therefore, the system developed in this work fulfils all requirements for being a useful tool for structured nanoparticle deposition. Both the discovered novel adsorption morphologies on non-structured substrates and the guided self-assembly of protein nanostructures, represent promising starting points for further scientific studies, such as solid-supported co-crystallization with DNA, and developments aiming at technological applications like the mesostructured deposition of MrgA-caged nanoparticles. Secondly, a method for improving the stability of biological compounds far beyond the limits of natural conditions was developed based on purple membrane as a model substance. Generally, embedding such targets in solid host material increases the stability and the range of possible applications. In medicine and biotechnology, there is a great interest in such composite hybrid materials in form of micro- or nanosized particles. In this work, a biomimetic approach for the encapsulation of biomolecules with silica is presented. It was inspired by the remarkable biomineralisation performed by some eucaryotic algae, the so-called diatoms. In the method elaborated here, two generic techniques were combined: In a first step, the surface of the biomolecule was modified via polyelectrolyte layer adsorption. It was shown that the polyamines used in the first step allow for the surface-templated mineralization of silicic acid and silica nano-particles on the modified surface in the second step of preparation. Both preparative steps were optimized towards mild conditions as required by many biomolecules. Application of this method to the model substance purple membrane resulted in a defined hybrid material with a nano-scale protective encapsulating silica shell. It was demonstrated that while the purple membrane retains its biological function, it is also shielded from otherwise detrimental solvents or molecules of low molecular weight. The method presented here not only allows for the production of significant amounts of encapsuled material, but it was furthermore shown to be adaptable to a variety of substances, such as single-walled carbon nanotubes and polymer microparticles – emphasizing the wide range of application for this method., Aufbau nanoskopischer Hybridstrukturen am Beispiel von MrgA und Purpurmembran.
- Published
- 2008
20. Biochemisch modifiziertes Bakteriorhodopsin als Baustein in Bio-to-Nano-Systemen
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Keller, Katja and Hampp, N. (Prof. Dr.)
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Crosslinking ,Oligonucleotide ,ddc:540 ,Chemie ,Vernetzung ,Bacteriorhodopsin ,Chemistry and allied sciences ,Chemistry and allied sciences -- Chemie ,Bakteriorhodopsin ,%22">Vernetzung ,2006 - Abstract
In der Natur gibt es vielfältige hoch interessante Phänomene, die man sich nur durch die Kombination von biologischem und technischem Wissen erklären kann. Zum Beispiel der so genannte „Lotuseffekt“, wobei es durch die Nano-Strukturierung der Oberflächen der Pflanze zu einem Selbstreinigungsprozess derselben kommt. Der Mensch hat nun begonnen, dieses vorhandene Wissen zu studieren, zu ergründen und sich letztendlich nutzbar zu machen. Daraus resultiert eine neue wissenschaftliche Fachrichtung, „Bionik“ genannt. Eine Schlüsseltechnologie bei der Anwendung der Bionik für unser tägliches Leben ist die so genannte Nanotechnologie. Dabei werden auf verschiedenste Weisen (chemisch, physikalisch, biologisch) nanoskalige Strukturen hergestellt beziehungsweise geschaffen um im Sinne der Bionik in unserem Alltag Verwendung zu finden. Das Ziel der Nanotechnologie kann als die Möglichkeit beschrieben werden, aus Molekülen Objekte zu generieren und Objekte wiederum in Moleküle zu zerlegen. Die Natur wird hierbei als Vorbild verwendet, da der Aufbau biologischer Systeme durch nanoskalige Prozesse geleitet wird, die über Jahrmillionen evolutionär optimiert wurden. In diesem System hat die Nanobiotechnologie in den letzten Jahren maßgeblich dazu beigetragen, biologisch interessante Systeme grundlegend zu verstehen und nanoskalige funktionale Einheiten kontrolliert zu generieren. Um die Nanobiotechnologie im Speziellen besser überblicken zu können, wurde innerhalb der VDI eine Einteilung in Nano-to-Bio-Systeme und Bio-to-Nano-Systeme vorgenommen, die im Detail nachfolgend Verwendung findet und erklärt wird. „Nano-to-Bio“-Systeme beschreiben nanotechnologische Verfahren und Materialien, die zur Manipulation biologischer Systeme eingesetzt werden. Im Gegensatz dazu beschreiben „Bio-to-Nano“-Systeme Prinzipien der Biologie, die, in technische Systemen übertragen, jetzt nutzbar gemacht werden. Wie gesagt ist die Nanobiotechnologie die Kernwissenschaft, um die evolutionär optimierten natürlichen Systeme für technische Anwendungen nutzbar zu machen. Auch mit Hilfe der heutigen Gentechnik ist es möglich, biologische Materialien gezielt auf die beabsichtigte technische Anwendung hin zu modifizieren. Ein solches biologisch wie technisch interessantes System mit einem hohen Grad an Anwendungspotential, in zum Beispiel der Dokumentessicherung und der Druckfarbentechnik, ist das seit nunmehr 30 Jahren bekannte Transmembranprotein Bakteriorhodopsin, das für diese Art der Anwendungen quasi als Prototyp angesehen werden kann. Das Protein zeigt mit seiner natürlichen Funktion der Photosynthese, für nano(bio)technologische Anwendungen interessante Eigenschaften. Aufgrund seiner optischen und photochemischen Eigenschaften und der Stabilität gegen chemische und physikalische Einflüsse ist Bakteriorhodopsin für den Einsatz in der optischen Informationspeicherung und -verarbeitung, der Energieumwandlung und der Optoelektronik besonders geeignet. Auch in der Sicherheitstechnik konnte gezeigt werden, dass modifiziertes Bakteriorhodopsin als farbgebendes photochromes Pigment ein großes Anwendungspotential besitzt. Im Gegensatz zu dieser Verwendung des membranintegrierten Bakteriorhodopsins in nicht „Bio-to-Nano“-Systemen, beschäftigt sich die vorliegende Arbeit mit der Untersuchung der Anwendungsmöglichkeiten des membranintegrierten Bakteriorhodopsin in Bio-to-Nano-Systemen. Die thematische „Hauptausrichtung“ liegt dabei in der Vertiefung des Konzepts der gerichteten Stapelung von Purpurmembranfragmenten zum Aufbau von zum Beispiel elektrooptischen Schalteinheiten. Die Eigenschaft des Bakteriorhodopsins, eine Photospannung über die Membran hinweg erzeugen zu können, soll mittels gerichteter Stapelung mehrerer Purpurmembranen, so genutzt werden, dass sich die erzeugte Spannung additiv erhöht. Als Konzept wird versucht mittels zweier komplementärer ssOligonucleotid-Stränge, die Purpurmembranfragmente gerichtet zu stapeln. Ein weiteres interessantes „Bio-to-Nano“-System mit entsprechendem möglichen Wachstumspotential ist das sogenannte „nanowiring“. Dabei wird ein miniaturisierter, elektronisch funktionsfähiger Schaltkreis auf DNA-Basis durch einen Selbst-assemblierungsprozess generiert. Um die notwendige elektrische Funktionalität im Schaltkreis zu erreichen, kombiniert man die gute Leitfähigkeit des Goldes mit der natürlichen Affinität von komplementären ssDNAs zueinander. Damit ist es möglich über Selbstassemblierung hoch-komplexe Strukturen von Schaltkreisen zu generieren. Aufbauend auf die bereits etablierte Möglichkeit der Gold-Bindung an PM und der Dekoration von Gold-Nanoteilchen mit bis zu 7 verschiedenen ssDNA-Strängen, soll an dieser Stelle gezeigt werden, dass es möglich ist, ssOligo an PM zu binden, das mit Gold-Nanopartikeln aktiviert ist. Das angebundene ssOligo wird anschließend mit dem entsprechenden Komplementär hybridisiert., In nature there are various highly interesting phenomena, which one can explain oneself only by the combination of biological and technical knowledge. For example „the Lotuseffekt in such a way specified “, whereby it comes by the nano-structuring of the surfaces of the plant to a self purification process the same. Humans began now to study this existing knowledge to fathom and finally make themselves usable. From this a new scientific field results, „to bionics “mentioned. A key technology with the application of the bionics for our daily life is the nano-technology in such a way specified. To find manufactured in most diverse ways (chemically, physically, biologically) nanoskalige structures and/or production over in the sense of the bionics in our everyday life use. The goal of the nano-technology can be described as the possibility of generating from molecules of objects and of dividing objects again into molecules. Nature is used here as model, since the structure of biological systems is led by nanoskalige processes, which were evolutionary optimized over millions of years. In this system the nano-biotechnology contributed in the last years considerably to understand biologically interesting systems fundamentally and to generate nanoskalige functional units controlled. In order to be able to grasp the nano-biotechnology in the special one better, within the VDI an organization into nano-raving IO systems and bio ton nano-systems was made, which finds use in the following in the detail and one explains. „Nano-ton bio “- systems describe nano-technological procedures and materials, which are used for the manipulation of biological systems. In contrast to it „bio ton nano “- systems describe principles of biology, which transfer, into technical systems, now to be made usable. As the nano-biotechnology the core science is said, in order to make the evolutionary optimized natural systems for technical applications usable. Also with the help of the today's genetic engineering it is possible to modify biological materials purposefully at intended technical application. Such biologically like technically interesting system with a high degree at application potential, in for example the document safety device and the printing ink technology, is for now 30 years the well-known Transmembranprotein Bakteriorhodopsin, which can be regarded for this kind of applications quasi as prototype. The protein shows technological applications interesting characteristics with its natural function of photosynthesis, for nano (bio). Due to its optical and photochemical characteristics and stability against chemical and physical influences Bakteriorhodopsin for the employment is particularly suitable in the optical Informationspeicherung and - processing, the energy conversion and optoelectronics. Also in the safety engineering it could be shown that modified Bakteriorhodopsin possesses a large application potential as colorgiving photo chrome pigment. Contrary to this use of the diaphragm-integrated Bakteriorhodopsins in not „bio ton nano “- systems, the available work concerns itself with the investigation of the application possibilities of the diaphragm-integrated Bakteriorhodopsin in bio ton nano-systems. The topic tables „“is appropriate for main adjustment thereby in the recess of the concept of the arranged stacking of magenta diaphragm fragments for the setting up from for example electrooptical Schalteinheiten. The characteristic of the Bakteriorhodopsins to be able to produce a photoelectric voltage over the diaphragm away is to be thus used by means of arranged stacking of several magenta diaphragms, that the produced tension additive increases. As concept tried by means of two complementary ssOligonucleotid strands to stack the magenta diaphragm fragments arranged. A further interesting „bio ton nano “- system with appropriate possible growth potential is the so-called „nanowiring “. A miniaturized, electronically functional circuit on DNA basis is generated by a self assembly process. In order to achieve necessary electrical functionality in the circuit, one combines the good conductivity of the gold with the natural affinity of complementary to each other ssDNAs. Thus it is to be generated possible over self assembly high-complex structures from circuits to. Constructing on the possibility of the gold connection at PM and the decoration of gold nano-particles with up to 7 different ssDNA strands, already established, it is to be demonstrated here that it is possible to bind ssOligo at PM which is activated with gold nano-particles. The tied up ssOligo is hybridized afterwards with the appropriate complementary.
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- 2006
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21. Laser-Induced Au Catalyst Generation for Tailored ZnO Nanostructure Growth.
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Durbach S, Schniedermeyer L, Marx A, and Hampp N
- Abstract
ZnO nanostructures, semiconductors with attractive optical properties, are typically grown by thermal chemical vapor deposition for optimal growth control. Their growth is well investigated, but commonly results in the entire substrate being covered with identical ZnO nanostructures. At best a limited, binary growth control is achieved with masks or lithographic processes. We demonstrate nanosecond laser-induced Au catalyst generation on Si(100) wafers, resulting in controlled ZnO nanostructure growth. Scanning electron and atomic force microscopy measurements reveal the laser pulse's influence on the substrate's and catalyst's properties, e.g., nanoparticle size and distribution. The laser-induced formation of a thin SiO
2 -layer on the catalysts plays a key role in the subsequent ZnO growth mechanism. By tuning the irradiation parameters, the width, density, and morphology of ZnO nanostructures, i.e., nanorods, nanowires, and nanobelts, were controlled. Our method allows for maskless ZnO nanostructure designs locally controlled on Si-wafers.- Published
- 2023
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22. Fusion of purple membranes triggered by immobilization on carbon nanomembranes.
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Riedel R, Frese N, Yang F, Wortmann M, Dalpke R, Rhinow D, Hampp N, and Gölzhäuser A
- Abstract
A freestanding ultrathin hybrid membrane was synthesized comprising two functional layers, that is, first, a carbon nanomembrane (CNM) produced by electron irradiation-induced cross-linking of a self-assembled monolayer (SAM) of 4'-nitro-1,1'-biphenyl-4-thiol (NBPT) and second, purple membrane (PM) containing genetically modified bacteriorhodopsin (BR) carrying a C-terminal His-tag. The NBPT-CNM was further modified to carry nitrilotriacetic acid (NTA) terminal groups for the interaction with the His-tagged PMs forming a quasi-monolayer of His-tagged PM on top of the CNM-NTA. The formation of the Ni-NTA/His-tag complex leads to the unidirectional orientation of PM on the CNM substrate. Electrophoretic sedimentation was employed to optimize the surface coverage and to close gaps between the PM patches. This procedure for the immobilization of oriented dense PM facilitates the spontaneous fusion of individual PM patches, forming larger membrane areas. This is, to our knowledge, the very first procedure described to induce the oriented fusion of PM on a solid support. The resulting hybrid membrane has a potential application as a light-driven two-dimensional proton-pumping membrane, for instance, for light-driven seawater desalination as envisioned soon after the discovery of PM., (Copyright © 2021, Riedel et al.)
- Published
- 2021
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23. Substituting Coumarins for Quinolinones: Altering the Cycloreversion Potential Energy Landscape.
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Paul N, Jiang M, Bieniek N, Lustres JLP, Li Y, Wollscheid N, Buckup T, Dreuw A, Hampp N, and Motzkus M
- Abstract
The light-activated cleavage of cyclobutane-based systems via [2 + 2] cycloreversions, such as thymine and coumarin dimers, is an important but still poorly understood ultrafast photochemical reaction. Systems displaying reversible cycloreversion have found various uses in cross-linked polymers, enhancing gas adsorption affinities in inorganics, and light-activated medical therapies. We report the identification of a heterogeneous mode of cycloreversion for a rarely examined coumarin analogue system. Quinolinone monomers and dimers were probed using ultraviolet pumped, transient absorption spectroscopy and demonstrated radically different photophysical properties than coumarins. Monomers displayed enhanced intersystem crossing at almost 1:1 versus the combined nonradiative and radiative singlet decay, while the dimers underwent cycloreversion to a one excited-one ground state monomer photoproduct pair. The change in both systems was directly linked to the lactame group in the quinolinone motif. This discovery highlights the dramatic effects that small chemical changes can have on photoreaction pathways and opens up a new means to produce and develop more efficient cycloaddition-cycloreversion systems.
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- 2018
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24. Real-time, label-free monitoring of cell viability based on cell adhesion measurements with an atomic force microscope.
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Yang F, Riedel R, Del Pino P, Pelaz B, Said AH, Soliman M, Pinnapireddy SR, Feliu N, Parak WJ, Bakowsky U, and Hampp N
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- Gold chemistry, HeLa Cells, Humans, MCF-7 Cells, Cell Adhesion, Cell Survival, Metal Nanoparticles chemistry, Microscopy, Atomic Force methods
- Abstract
Background: The adhesion of cells to an oscillating cantilever sensitively influences the oscillation amplitude at a given frequency. Even early stages of cytotoxicity cause a change in the viscosity of the cell membrane and morphology, both affecting their adhesion to the cantilever. We present a generally applicable method for real-time, label free monitoring and fast-screening technique to assess early stages of cytotoxicity recorded in terms of loss of cell adhesion., Results: We present data taken from gold nanoparticles of different sizes and surface coatings as well as some reference substances like ethanol, cadmium chloride, and staurosporine. Measurements were recorded with two different cell lines, HeLa and MCF7 cells. The results obtained from gold nanoparticles confirm earlier findings and attest the easiness and effectiveness of the method., Conclusions: The reported method allows to easily adapt virtually every AFM to screen and assess toxicity of compounds in terms of cell adhesion with little modifications as long as a flow cell is available. The sensitivity of the method is good enough indicating that even single cell analysis seems possible.
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- 2017
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25. PEGylation of membrane proteins like bacteriorhodopsin as a tool to increase their stability toward ethanol.
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Busch AP, Neebe M, and Hampp N
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- Amino Acid Sequence, Bacteriorhodopsins metabolism, Dose-Response Relationship, Drug, Halobacterium salinarum cytology, Molecular Sequence Data, Protein Stability drug effects, Purple Membrane drug effects, Purple Membrane metabolism, Bacteriorhodopsins chemistry, Ethanol pharmacology, Polyethylene Glycols chemistry
- Abstract
Protection of biological compounds, for example, enzymes, viruses, or even whole cells, against degradation is very important for many applications. Embedding of such compounds into polymer matrices is a straightforward common method. However, in biotechnology and medicine there is a great interest to prepare micro- and nanosized shells around the biocomponents in order to protect them and having only a minor increase in size. The PEGylation of biological macromolecules has gained attention because degradation by proteolytic enzymes is significantly retarded and, in turn, their bioavailability is enhanced. We found that PEGylation is also a powerful tool to protect biomaterials from degradation by small organic solvent molecules, in particular, ethanol. Methoxy-polyethylene glycol (MPEG) modified BR survives exposure to significant concentrations of ethanol, up to 30%, and preserves its photochromism, whereas unmodified PM is instantaneously denatured at such concentrations. This is useful for potential technical applications of BR but is of relevance for many other applications where biomaterials and, in particular, biomembranes may be exposed to solvents.
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- 2012
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26. Stability of purple membranes from Halobacterium salinarum toward surfactants: inkjet printing of a retinal protein.
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Imhof M, Pudewills J, Rhinow D, Chizhik I, and Hampp N
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- Models, Biological, Protein Stability, Eye Proteins chemistry, Halobacterium salinarum chemistry, Printing, Purple Membrane chemistry, Retina, Surface-Active Agents chemistry
- Abstract
Inkjet printing is a versatile technique widely applied in biological microarray technology. Because of its photochemical and photophysical properties, bacteriorhodopsin (BR) from Halobacterium salinarum holds promise for applications in nanotechnology, and inkjet printing would simplify the transfer of BR to suitable substrates. Surfactants are essential parts of inkjet formulations tuning viscosity, rheology, and spreading behavior of the solution. However, many surfactants destabilize the structure of proteins and often cause denaturation accompanied by a complete loss of function. Inkjet printing of membrane proteins is particularly challenging and special care must be taken in the choice of the surfactant. For BR, the situation is complicated by the fact that the structural integrity of BR depends on its native membrane environment, the so-called purple membrane (PM). PM contains 10 lipid molecules per BR monomer and is very sensitive toward surfactants. In this work, we identified surfactants suitable for inkjet formulations containing PM. Initially, we screened a variety of technically relevant surfactants for compatibility with PM using the UV-vis absorption of the retinal chromophore as a natural probe. Promising candidates were selected, and their impact on the structure of PM and BR was analyzed using UV-vis spectroscopy, CD spectroscopy, and small-angle X-ray scattering (SAXS). We identified two surfactants compatible with PM and suitable for inkjet formulations. An inkjet formulation containing PM as dye component was developed. We demonstrate that the photochromic properties of BR are maintained upon inkjet printing.
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- 2012
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27. Structural changes in bacteriorhodopsin caused by two-photon-induced photobleaching.
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Rhinow D, Imhof M, Chizhik I, Baumann RP, and Hampp N
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- Bacteriorhodopsins ultrastructure, Circular Dichroism, Crystallization, Microscopy, Atomic Force, Photons, Protein Structure, Secondary, Purple Membrane ultrastructure, Scattering, Small Angle, Spectroscopy, Fourier Transform Infrared, X-Ray Diffraction, Bacteriorhodopsins chemistry, Halobacterium salinarum chemistry, Photobleaching, Purple Membrane chemistry
- Abstract
Bacteriorhodopsin (BR) is the key protein of the halobacterial photosynthetic system. BR assembles into two-dimensional crystalline patches, the so-called purple membranes (PM), and acts as a light-driven proton pump converting light energy into the chemical energy of a proton gradient over the cell membrane. The two-photon absorption (TPA) of BR is so far not fully understood. Astonishingly high TPA cross sections have been reported, but the molecular mechanisms have not been elucidated. In this work, we address structural changes in BR and PM upon TPA, investigating its TPA photochemistry by spectroscopy, small-angle X-ray scattering, as well as electron and atomic force microscopy. We observe that TPA of BR leads to formation of an UV-absorbing N-retinyl-bacterioopsin state, which is accompanied by the loss of crystalline order in PM. FTIR and CD spectroscopy confirm that BR trimers as well as the secondary structure of the BR molecules are preserved. We demonstrate that excitation by TPA results in the photochemical reduction of the retinal Schiff base, which in turn causes a permanent asymmetric shape change of BR, similar to the one transiently observed during the photocycle-related opening and closing of the cytoplasmic proton half channel. This shape change causes PM sheets to merely roll up toward the extracellular side and causes the loss of crystallinity of PM. We present a model for the TPA photoresponse of BR, which also explains the irreversibility of the process in terms of a photochemical reduction of the Schiff base.
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- 2012
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28. A new class of purple membrane variants for the construction of highly oriented membrane assemblies on the basis of noncovalent interactions.
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Baumann RP, Busch AP, Heidel B, and Hampp N
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- Adenosine Triphosphate metabolism, Bacteriorhodopsins chemistry, Bacteriorhodopsins metabolism, Graphite chemistry, Halobacterium salinarum metabolism, Light, Protons, Purple Membrane metabolism, Purple Membrane chemistry
- Abstract
Purple membranes (PM) from Halobacterium salinarum have been discussed for several technical applications. These ideas started just several years after its discovery. The biological function of bacteriorhodopsin (BR), the only protein in PM, is the light-driven proton translocation across the membrane thereby converting light energy into chemical energy. The astonishing physicochemical robustness of this molecular assembly and the ease of its isolation triggered ideas for technical uses. All basic molecular functions of BR, that is, photochromism, photoelectrism, and proton pumping, are key elements for technical applications like optical data processing and data storage, ultrafast light detection and processing, and direct utilization of sunlight in adenosine 5'-triphospate (ATP) generation or seawater desalination. In spite of the efforts of several research groups worldwide, which confirmed the proof-of-principle for all these potential applications, only the photochromism-based applications have reached a technical level. The physical reason for this is that no fixation or orientation of the PMs is required. The situation is quite different for photoelectrism and proton pumping where the macroscopic orientation of PMs is a prerequisite. For proton pumping, in addition, the formation of artificial membranes which prevent passive proton leakage is necessary. In this manuscript, we describe a new class of PM variants with oppositely charged membrane sides which enable an almost 100% orientation on a surface, which is the key element for photoelectric applications of BR. As an example, the mutated BR, BR-E234R7, was prepared and analyzed. A nearly 100% self-orientation on mica was obtained.
- Published
- 2012
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29. Crystallinity of purple membranes comprising the chloride-pumping bacteriorhodopsin variant D85T and its modulation by pH and salinity.
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Rhinow D, Chizhik I, Baumann RP, Noll F, and Hampp N
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- Bacteriorhodopsins genetics, Chlorides chemistry, Crystallization, Freeze Fracturing, Halobacterium salinarum chemistry, Halobacterium salinarum cytology, Hydrogen-Ion Concentration, Microscopy, Atomic Force, Models, Molecular, Point Mutation, Protein Conformation, Salinity, Bacteriorhodopsins chemistry, Bacteriorhodopsins metabolism, Chlorides metabolism, Purple Membrane chemistry
- Abstract
Self-assembly of membrane proteins inside the cell membrane critically depends on specific protein-protein and protein-lipid interactions. Purple membranes (PMs) from Halobacterium salinarum comprise wild-type bacteriorhodopsin (BR) and lipids only and form a 2-D crystalline lattice of P3 symmetry in the cell membrane. It is known that removal of the retinylidene residue as well as the exchange of selected amino acids lead to a loss of crystallinity. In PMs comprising the BR variant D85T, we have observed a tunable tendency to form crystalline domains, which depends on pH-value and chloride ion concentration. BR-D85T resembles the function of the chloride pump halorhodopsin. The protonation state of amino acid residues within the binding pocket and chloride binding in the vicinity of the protonated retinal Schiff base affect the overall shape of BR-D85T molecules in the membrane, thereby changing their interactions and subsequently their tendency to form crystalline areas. The combination of small-angle X-ray scattering, atomic force microscopy, and freeze-fracture electron microscopy enables us to analyze the transitions statistically as well as on the single membrane level. PM-D85T is a model system to study membrane protein association upon substrate binding in a native environment. Furthermore, the ability to reversibly modulate the crystallinity of PMs probably will be useful for the preparation of larger artificial crystalline arrays of BR and its variants.
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- 2010
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30. Dynamics of bacteriorhodopsin in solid-supported purple membranes studied with tapping-mode atomic force microscopy.
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Schranz M, Baumann RP, Rhinow D, and Hampp N
- Subjects
- Aluminum Silicates chemistry, Bacteriorhodopsins chemistry, Gold chemistry, Protein Multimerization, Protein Structure, Quaternary, Silicon chemistry, Static Electricity, Bacteriorhodopsins metabolism, Halobacterium salinarum cytology, Microscopy, Atomic Force, Purple Membrane chemistry, Purple Membrane metabolism
- Abstract
Purple membrane (PM) from Halobacterium salinarum, which comprises bacteriorhodopsin (BR) and lipids only, has been employed by many groups as a model system to study the structure and dynamics of membrane proteins. Although the conformational dynamics of BR within PM has been extensively analyzed with subnanometer resolution by means of diffraction experiments and spectroscopic methods, as well, structural studies of dynamical transitions within single PMs are rare. In this work, we show that tapping-mode atomic force microscopy (TM-AFM) is ideally suited to study dynamical transitions within solid-supported PMs at the nanoscale. Time-dependent AFM analysis of solid-supported PMs shows that redistribution processes take place between a crystalline core region, featuring a height of approximately 5 nm, and a highly mobile rim region (approximately 4 nm in height). Furthermore, we discuss the influence of temperature and substrate on the equilibrium. The experiments are complemented by electrostatic force microscopy (EFM) of PM on mica. Beyond their importance for many physiological processes, dynamical transitions in biological membranes, as observed in this work, are of critical importance for all methods that make use of solid-supported membrane assemblies, either analytical tools or applications.
- Published
- 2010
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31. Curvature of purple membranes comprising permanently wedge-shaped bacteriorhodopsin molecules is regulated by lipid content.
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Rhinow D and Hampp N
- Subjects
- Halobacterium salinarum metabolism, Hydrogen-Ion Concentration, Lipids analysis, Mass Spectrometry, Models, Molecular, Protein Structure, Secondary, Bacteriorhodopsins chemistry, Lipids chemistry, Purple Membrane chemistry
- Abstract
Purple membrane (PM) from Halobacterium salinarum has been studied by many groups and is commonly described as a flat 2-D crystalline membrane microdomain which contains a hexagonal crystalline lattice of bacteriorhodopsin (BR) trimers in a stoichiometric ratio of 10:1 between lipids and BR. BR is the key protein in the halobacterial photosynthetic system and acts as a light-driven proton pump. Upon absorption of a photon, BR undergoes a cyclic series of intramolecular changes, among them a transient "wedge-like" geometrical change of the protein due to a tilt in helix F, one of the seven alpha-helical domains of BR. Due to the strong coupling between the BRs in the crystalline lattice, this may affect membrane topography. In nature, only low light levels occur and the total number of BRs in the "wedge-shaped" state is negligible. For mutated PMs like PM-D85T and PM-D85N (PM-D85X, X = neutral residue), the change of the membrane topography can be triggered in a pH-dependent manner. PMs containing BR-D85X look like "cups" at certain pH values. How does nature deal with a mutated PM like PM-D96G/F171C/F219L (PM-Tri) which comprises permanently "wedge-shaped" BRs and how does this influence membrane assembly? Astonishingly, we observed that PM-Tri is flat. Obviously, the morphology of Halobacterium salinarum is highly conserved and requires flat PMs to be assembled. We found that the lipid content of PM-Tri is specifically altered to assemble a hexagonal crystalline PM-Tri lattice of flat topography.
- Published
- 2010
- Full Text
- View/download PDF
32. Polarization holographic high-density optical data storage in bacteriorhodopsin film.
- Author
-
Yao B, Ren Z, Menke N, Wang Y, Zheng Y, Lei M, Chen G, and Hampp N
- Abstract
Optical films containing the genetic variant bacteriorhodopsin BR-D96N were experimentally studied in view of their properties as media for holographic storage. Different polarization recording schemes were tested and compared. The influence of the polarization states of the recording and readout waves on the retrieved diffractive image's intensity and its signal-to-noise ratio were analyzed. The experimental results showed that, compared with the other tested polarization relations during holographic recording, the discrimination between the polarization states of diffracted and scattered light is optimized with orthogonal circular polarization of the recording beams, and thus a high signal-to-noise ratio and a high diffraction efficiency are obtained. Using a He-Ne laser (633 nm, 3 mW) for recording and readout, a spatial light modulator as a data input element, and a 2D-CCD sensor for data capture in a Fourier transform holographic setup, a storage density of 2 x 10(8) bits/cm2 was obtained on a 60 x 42 microm2 area in the BR-D96N film. The readout of encoded binary data was possible with a zero-error rate at the tested storage density.
- Published
- 2005
- Full Text
- View/download PDF
33. Analytical chemistry. Analytes ante portas.
- Author
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Hampp N
- Subjects
- Diffusion, Lipid Bilayers, Peptides chemistry, Protein Structure, Secondary, Protein Structure, Tertiary, Enzymes metabolism, Fluorescent Dyes, Fluorometry, Proteome
- Published
- 2002
- Full Text
- View/download PDF
34. Biological photochrome bacteriorhodopsin and its genetic variant Asp96 ? Asn as media for optical pattern recognition.
- Author
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Hampp N, Thoma R, Oesterhelt D, and Bräuchle C
- Abstract
The biological photochrome bacteriorhodopsin (BR) is contained within the purple membrane (PM) of Halobacterium halobium. Artificial derivatives with improved optical properties can be generated by genetic methods and isolated from mutated halobacterial strains. The use of PM films that contain wild-type BR and BR variants as real-time recording media for various holographic applications has been reported previously, and the advantages of BR variants have been demonstrated. The high reversibility (>> 10(5) record/erase cycles), the fast time scale of its photoconversions (femtoseconds to milliseconds), and the large photochromic shift ( approximately 160 nm) occurring during its photocycle make it a promising material for real-time applications. A dual-axis joint-Fourier-transform (DA-JFT) correlator is used to demonstrate the applicability of PM films in holographic pattern recognition. One major advantage of PM films in this application is their high spatial resolution of more than 5000 lines/mm. Severe restrictions on the overall performance of the DA-JFT correlator system are caused by scattered light and result in a low signal-to-noise ratio. Since PM patches typically have a diameter in the range of the visible wavelengthsthat are used for hologram recording, light scattering is an intrinsic problem of PM films. The polarization recording properties of PM films are employed to overcome this problem. More than 20-fold improvement of the signal-to-noise ratio in the DA-JFT correlator output is obtained.
- Published
- 1992
- Full Text
- View/download PDF
35. Bacteriorhodopsin wildtype and variant aspartate-96 --> aspargine as reversible holographic media.
- Author
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Hampp N, Bräuchle C, and Oesterhelt D
- Abstract
Air dried films of purple membranes (PM) from Halobacterium halobium containing the photochromic protein bacteriorhodopsin (BR) were prepared and the BR-photocycle of this material analyzed. The absorption maxima of the initial state B (lambda(max) = 570 nm) and the photochemical intermediate M (lambda(max) = 412 nm), which is the longest living intermediate in suspension (tau approximately 10 ms), were spectrally well separated. Light-induced population gratings between B and M were used for reversible holographic recording in these dry PM films. The resolution (>5,000 lines/mm) of PM films was comparable to the corresponding values of conventional photochromic recording materials. The longterm stability toward photochemical degradation of PM films is excellent (> 100.000 recording cycles). The spectral bandwidth (400-680 nm) of such films covers nearly the whole visible spectrum. Both the photochemical transition from B --> M with wavelengths in the green-red range and from M --> B with blue light were utilized for holographic recording. The latter possibility (M --> B) seems to be advantageous for several applications because the holographic grating is only formed during reconstruction. Higher reading intensities lead to higher population of the M-state and result in an increase of the fringe contrast instead of decreasing it. New possibilities for the further development of holographic media based on bacteriorhodopsin are raised by the availability of PM variants with modified optical properties. By the use of the variant BR-326, which differs from the wildtype PM by a single amino acid exchange (aspartate-96 --> asparagine), the sensitivity of PM films is increased by approximately 50% from 12 cm(2)/J to 19 cm(2)/J for recording with 568 nm. The sensitivity for recording with 413 nm (33 cm(2)/J) is not influenced by the amino acid exchange. The observed diffraction efficiency eta of PM films with BR-326 is twice that of BR-wildtype (BR-WT) films and is in the range of conventional organic photochromics ( approximately 1%). In dried films of both BR-WT and BR-326 the M-decay was shown to be at least biexponential.
- Published
- 1990
- Full Text
- View/download PDF
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