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Antimicrobial peptides (AMPs) kill bacteria by targeting their membranes through various mechanisms involving peptide assembly, often coupled with disorder‐to‐order structural transition. However, for several AMPs, similar conformational changes in cases in which small organic compounds of both endogenous and exogenous origin have induced folded peptide conformations have recently been reported. Thus, the function of AMPs and of natural host defence peptides can be significantly affected by the local complex molecular environment in vivo; nonetheless, this area is hardly explored. To address the relevance of such interactions with regard to structure and function, we have tested the effects of the therapeutic drug suramin on the membrane activity and antibacterial efficiency of CM15, a potent hybrid AMP. The results provided insight into a dynamic system in which peptide interaction with lipid bilayers is interfered with by the competitive binding of CM15 to suramin, resulting in an equilibrium dependent on peptide‐to‐drug ratio and vesicle surface charge. In vitro bacterial tests showed that when CM15⋅suramin complex formation dominates over membrane binding, antimicrobial activity is abolished. On the basis of this case study, it is proposed that small‐molecule secondary structure regulators can modify AMP function and that this should be considered and could potentially be exploited in future development of AMP‐based antimicrobial agents.

Extracellular vesicles (EVs) are currently in scientific focus, as they have great potential to revolutionize the diagnosis and therapy of various diseases. However, numerous aspects of these species are still poorly understood, and thus, additional insight into their molecular-level properties, membrane-protein interactions, and membrane rigidity is still needed. We here demonstrate the use of red-blood-cell-derived EVs (REVs) that polarized light spectroscopy techniques, linear and circular dichroism, can provide molecular-level structural information on these systems. Flow-linear dichroism (flow-LD) measurements show that EVs can be oriented by shear force and indicate that hemoglobin molecules are associated to the lipid bilayer in freshly released REVs. During storage, this interaction ceases; this is coupled to major protein conformational changes relative to the initial state. Further on, the degree of orientation gives insight into vesicle rigidity, which decreases in time parallel to changes in protein conformation. Overall, we propose that both linear dichroism and circular dichroism spectroscopy can provide simple, rapid, yet efficient ways to track changes in the membrane-protein interactions of EV components at the molecular level, which may also give insight into processes occurring during vesiculation.

The strength and geometry of adsorption of substituted propenoic acids on silver surface were studied by means of surface enhanced Raman spectroscopy (SERS) using silver sol. Based on their SERS behavior, two classes of phenylpropenoic acids studied were distinguished. The first class of propenoic acids (atropic acid, (E)-2,3-diphenylpropenoic acid, (E)-2-(2-methoxyphenyl)-3-phenylpropenoic acid, (E)-2,3-di-(4-methoxyphenyl)phenylpropenoic acid and (E)-2-(2-methoxyphenyl)-3-(4-fluorophenyl)propenoic acid) has shown strong charge transfer (CT) effect. We suggest bidentate carboxyl bonded species based on the SERS enhanced bands of νCOO− around 1394 cm−1 and νC―C of the ―C―COO− moiety at 951 cm−1. In these series the plane of the α-phenyl group (γCH out-of-plane vibrations at 850–700 cm−1) is almost parallel to the silver surface, while the β-phenyl group is in tilted position depending on the type and the position of substituent(s) showing strong SERS enhanced bands of νCC + βCH (in-plane mode) at 1075 cm−1, νCC (ring breathing mode, in-plane) at 1000 cm−1 and γCCC (out-of-plane mode) around 401 cm−1. The other class of propenoic acids (cinnamic acid, (E)-2-phenyl-3-(4-methoxyphenyl)propenoic acid) has shown weak electromagnetic (EM) enhancement (CC bands is enhanced in cinnamic acid). In this case no significant carboxyl enhancement was observed, so we suggest that adsorbed species lie parallel to the surface. The two types of adsorption can be related to the dissociation ability of the carboxylic group. In the first case the carboxylic H dissociates, while in the second case it does not, as indicated also by the characteristic νCO band at 1686 cm−1 in the FT-Raman spectra of methanolic solutions. Copyright © 2015 John Wiley & Sons, Ltd.

Utilization of various typesof multi-walled carbon nanotubes (MWCNTs) in zincrich paints (ZRPs) is presented addressing percolation and porosity related phenomena of traditional ZRPs. Hybrid paint coatings were formulated with 3.21wt% polypyrrole (PPy) deposited alumina-MWCNT inhibitor particles (PDAMIPs) and 70wt% zinc contents. Corrosion protection behavior of the hybrid coatings was investigated by electrochemical impedance spectroscopy (EIS), glow-discharge optical emission spectroscopy (GD OES), X-ray photoelectron spectroscopy (XPS), and FT-Raman spectroscopy. Immersion and salt-spray chamber tests gave evidence of improved galvanic protection and barrier nature of the hybrid coatings over the conventional ZRPs, whereas inhibited zinc corrosion and ignorable steel corrosion took place besides lower degradation of the binder. Zinc-rich hybrid paints with either high relative amount of polyelectrolyte-modified or low proportion of functionalized MWCNTsaffordedenhancedcorrosionprevention.Thisresultispartlyattributed to the nanotube volume fractions around the threshold of infinite cluster formation contributing to electrical percolation and galvanic action of the hybrids. Experimental results are discussed in a broader context on the basis of structure related findings of the PDAMIPs (described in Part I) and in the light of recent literature data. From the newly developed inhibitor particles, some of them are respected as worthy additives for application in hybrid coatings featuring high performance corrosion prevention functionality.

The field of extracellular vesicles is an exponentially growing segment of biomedical sciences. However, the problems of normalisation and quantification of extracellular vesicle samples have not been completely solved yet. Currently, extracellular vesicle samples are standardized on the basis of their protein content sometimes combined with determination of the particle number. However, even this combined approach may result in inaccuracy and overestimation of the extracellular vesicle concentration. Lipid bilayers are indispensable components of extracellular vesicles. Therefore, a lipidbased quantification, in combination with the determination of particle count and/or protein content, appears to be a straightforward and logical approach for the extracellular vesicle field. In this study we set the goal to improve the previously reported sulfo-phospho-vanillin total lipid assay. We introduced an aqueous phase liposome standard (DOPC) to replace the purified lipid standards in organic solvents (used commonly in previous studies). Furthermore, we optimized the concentration of the vanillin reagent in the assay. We found that elimination of organic solvents from the reaction mixture could abolish the background colour that interfered with the assay. Comparison of the optimised assay with a commercial lipid kit (based on the original sulfo-phospho-vanillin lipid assay) showed an increase of sensitivity by approximately one order of magnitude. Thus, here we report a quick, reliable and sensitive test that may fill an existing gap in extracellular vesicle standardisation. When using the optimised total lipid assay reported here, extracellular vesicle lipid measurements can be as easy as measuring proteins with a simple BCA test.

FT-Raman spectra of human enamel surfaces from sound, affected (with 1 cavity) and highly affected (with at least 3 cavities) tooth samples were analyzed by principal component analysis (PCA). Major differences between the unaffected and affected tooth samples seem to arise from the structural changes along the c-axis of hydroxyapatite, the chief crystalline component of human dental enamel. Based on Fisher index calculations, the most discriminative value was obtained for the intensity of the only Raman active nu 2PO43- (E-1) symmetric deformation mode at 428 cm(-1). Moreover, these changes can be observed through the whole tooth enamel surface, establishing a predisposition to caries correlated to chemical and structural composition of tooth enamel. No spectral changes regarding the CO32- substitution were detected by both nondestructive FT-Raman and FTIR (Fourier transform infrared) spectroscopy of the powdered teeth samples. Copyright (C) 2009 John Wiley & Sons, Ltd.

Some seashells of the Philippine venus species and sea coral of Pontes sp. were studied by means of FT-Raman, Fourier transform infrared spectroscopy (FTIR) and Far-FTIR spectroscopic methods. The Raman spectra show that both Porites sp. and P. venus are of aragonite-structured CaCO3. Detailed spectral analysis, however, reveals some small differences, due to differences in the crystallite size or habit and to different minor element contents. IR spectra show that Porites sp. contains also some small quantities of calcite-structured carbonates. The I…2 band (shoulder) of calcite at 875.7 cm-1 is present in the IR spectrum. The separation of the two I…2 bands (856.4 cm-1 for aragonite and 875.7 cm-1 for calcite) suggests the absence of solid solution of the two polymorphic phases of CaCO3. Spectroscopic results were confirmed also by X-ray powder diffraction measurements.