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The NMR spectroscopy technique is employed to analyze the direct interaction taking place between amphotericin B (AmB) and ergosterol in lipid bilayers. The results prove the existence of a direct intermolecular interaction between the two components in the bilayers.

Four branched n-alkane samples were synthesized with the same carbon number of the main chain, n=35, to which the methyl, butyl, hexyl, and butyl phenyl groups were respectively attached at the middle, and also the corresponding linear homologue of C35. Findings revealed that main chains of branched alkane molecules are not folded, irrespective of length and chemical structure of branches.

The results on the methyl-branched alkane M39 with n=39, obtained from SEM, DSC, X-ray diffraction, Raman scattering, IR absorption measurements and computer simulation, are presented. These results show two crystalline structures, proposed for M39 appear

Detailedcrystal structure analysis has been carried out for fourcrystalline forms (I, I′, II, and high-temperature phase, HT)of uniaxially oriented specimens from a novel polyethylene-like polymer,−[(CH2)20–CHBr]n– on the basis of the 2-dimensional X-ray diffractionpatterns and polarized FTIR spectral data. This polymer has Br atomsplaced regularly on each and every 21st backbone carbon. The preciseBr placement along the polyethylene backbone allows drastically differentchain conformation and chain packing modes between the group of formsI and I′ and the group of form II and HT phase. In forms Iand I′, the molecule is fully extended adopting a planar all-transzigzag conformation with layers of Br atoms normalto the chain axis. Conformational disorder and mismatch in relativeheight of Br atom between the neighboring chains distinguish formI from form I′. In forms II and HT phase, the molecular chainsbend at the Br substitutional point and take a large zigzag form consistingof long methylene segmental arms. The molecular bends are caused bythe generation of nonplanar gaucheconformers atthe C–C bonds adjacent to the CHBr groups, while the CH2segments maintain the all-transconformation.The major difference between form II and HT is conformational disorderwithin the methylene runs. Heating at T< 65 °Cunder unrestrained condition causes an irreversible transition fromform I′ to form I, and form I transforms irreversibly to formII in a narrow temperature range of 65–66 °C. The highertemperature heating induces the reversible and apparently continuoustransition of form II to the HT phase. On the other hand, the tensilestretching at room temperature causes the irreversible transitionof forms I and II to the form I′. [ABSTRACT FROM AUTHOR]

The simultaneous measurement of Fouriertransform infrared (FTIR)transmission spectra and 2-dimensional wide-angle X-ray diffraction(WAXD) and small-angle X-ray scattering (SAXS) patterns has been performedsuccessfully to investigate the hierarchical structure changes occurringin the stress-induced phase transition phenomenon of uniaxially orientedpoly(tetramethylene terephthalate) film. The molar fraction of theβ-crystal form, evaluated from the IR and WAXD data analyses,increased steeply in the plateru region of the stress–straincurve as already known well. The 2D SAXS data have revealed the remarkableand reversible change in the stacked lamellar structure just afterthe α-to-β phase transition was completed, where the tiltingangle of the stacked lamellae measured from the draw axis of the orientedsample became zero, and the lamellar thickness increased due to theinclusion of amorphous region located in the boundary part of thecrystalline lamellae. In parallel, the X-ray reflection spots in awider diffraction angle region became diffuse in the observed WAXDpattern of the β form, indicating the packing disorder of themechanically stressed chains. In this way, the simultaneous combinationof the 3 different types of equipments has allowed us to deduce thedetailed structural change from the various levels: the stress-inducedα–β transition was found to occur not only withthe remarkable changes in the molecular chain conformation and chainpacking mode in the crystal lattice, but also with the large and reversiblechange in the lamellar stacking structure. The stress-induced changesin lamellar thickness and long period were simulated using a mechanicalmodel with these hierarchical structure changes taken into account,giving relatively good reproduction of the observed data. [ABSTRACT FROM AUTHOR]

Although amphotericin B (AmB) is thought to exert its antifungal activity by forming transmembrane ion-permeable self-assemblies together with ergosterol, no previous study has directly proven AmB-ergosterol interaction. To establish the interaction, we measured 2H NMR using deuterium-labeled sterols and AmB. The 2H NMR spectra of deuterated ergosterol in palmitoyloleoylphosphatidylcholine (POPC) bilayers showed that fast axial diffusion of erogosterol was almost completely inhibited by the coexistence of AmB. Conversely, cholesterol mobility in POPC membrane was essentially unchanged with or without AmB. These results unequivocally demonstrate that ergosterol has significant interaction with AmB in POPC bilayers. In addition, we examined the mobility of AmB using deuterium-labeled AmB, and found that, although AmB is almost immobilized in sterol-free and cholesterol-containing POPC membranes, a certain ratio of AmB molecules acquires mobility in the presence of ergosterol. The similar mobility of AmB and ergosterol in POPC bilayers confirmed the idea of the direct intermolecular interaction between ergosterol and AmB. [ABSTRACT FROM AUTHOR]

Neurodegenerative diseases are usually characterized by plaques made of well-ordered aggregates of distinct amyloid proteins. Dissociating these very stable amyloid plaques is a critical clinical issue. In this study, we present a joint mid-infrared free electron laser experiment/nonequilibrium molecular dynamics simulation to understand the dissociation process of a representative example GNNQQNY fibril. By tuning the laser frequency to the amide I band of the fibril, the resonance takes place and dissociation is occurred. With the calculated and observed wide-angle X-ray scattering profiles and secondary structures before and after laser irradiation being identical, we can propose a dissociation mechanism with high confidence from our simulations. We find that dissociation starts in the core of the fibrils by fragmenting the intermolecular hydrogen bonds and separating the peptides and then propagates to the fibril extremities leading to the formation of unstructured expanded oligomers. We suggest that this should be a generic mechanism of the laser-induced dissociation of amyloid fibrils.

The proteasome is a large multisubunit complex that plays a crucial role in the removal of damaged or selective ubiquitinated proteins, thereby allowing quality control of cellular proteins and restricted regulation of diverse cellular signaling in eukaryotic cells. Proteasome-dependent protein degradation is involved in almost all aspects of plant growth and responses to environmental stresses including pathogen resistance. Although the molecular mechanism for specifying targets by ubiquitin ligases is well understood, the detailed characterization of the plant proteasome complex remains unclear. One of the most important features of the plant proteasome is that most subunits are encoded by duplicate genes, suggesting the highly heterogeneous composition of this proteasome. Here, we performed affinity purification and a combination of 2-dimensional electrophoresis and mass spectrometry, which identified the detailed composition of paralogous and modified proteins. Moreover, these proteomics approaches revealed that specific subunit composition and proteasome peptidase activity were affected by pathogen-derived MAMPs, flg22 treatment. Interestingly, flg22 treatment did not alter mRNA expression levels of the peptidase genes PBA, PBB1/2, PBE1/2, and total proteasome levels remained unchanged by flg22 as well. These results demonstrate the finely tuned mechanism that regulates proteasome function via putative post-translational modifications in response to environmental stress in plants.

The H-shape alkanes of various arm lengths have been synthesized successfully through the Grignard reaction. The detailed investigation of these novel compounds may allow us to widen the topological chemistry field furthermore. The molecular form and molecular packing structure in the crystal lattice have been revealed successfully on the basis of X-ray structure analysis as well as the analysis of Raman longitudinal acoustic modes (LAM) sensitive to the alkyl zigzag chain segments. The molecular conformation in the crystal lattice is deformed markedly from the originally imagined H-shape. In the cases of C3HOH to C6HOH, for example, the molecules are packed in a complicated manner and the OH···O hydrogen bonds govern the whole intermolecular interactions mainly. Since the alkyl segmental length is not very long, the conformational change is not very drastic, i.e., the small configurational entropy. Synergic effect of the hydrogen bonds and the small configurational entropy gives the higher melting point as known from the thermal data. On the other hand, in the cases of C10HOH and C12HOH, one of the long alkyl chain arms is found to be bent by 90° so that all of the alky chain segments of planar-zigzag conformation can be packed as closely as possible, and the intermolecular OH···O hydrogen bonds are also formed effectively without any mistake. As a result, the contribution of nonbonded intra- and intermolecular van der Waals interactions between the trans-zigzag alkyl chain segments become major, and the coupling of this enthalpy effect with the larger configurational entropy effect of the molecular shape results in the decrement of the melting point which approaches gradually that of longer n-alkane compound. In this way a sensitive balance between the nonbonded van der Waals interactions, the OH···O hydrogen bonds, as well as the configurational entropy effect gives the characteristic thermal behavior of the H-shape compounds. The thus-newly synthesized H-shape alkane compounds should give us new insight into the packing topology of complicated molecules, leading to the development of new functionality unexpected for normal linear alkane compounds., (© 2011 American Chemical Society)

We have reported the synthesis of dimethylformamide (DMF)-protected gold nanoclusters using a surfactant-free DMF reduction method. DMF-protected gold nanoclusters (Au NCs) are obtained without the formation of gold nanoparticles and bulk metals as byproducts using a hot injection process for the homogeneous reduction. The as-prepared DMF-protected Au NCs were a mixture of various-sized Au NCs with a cluster number of less than 20 including at least Au(8) and Au(13). The photoluminescence emission from Au(8) and Au(13) was confirmed in the photoluminescence spectra. The Au NCs are stabilized with DMF molecules through the interaction of amide groups of DMF with Au NCs. DMF-protected Au NCs in solution were found to have high thermal stability, high dispersion stability in various solvents, and high photochemical stability. The DMF-protected Au NCs dispersed well for at least a month in various solvents such as water, acid (pH 2), alkali (pH 12) and 0.5 M NaCl aqueous solution, and methanol without further surface modification. The thermal stability of DMF-protected Au NCs was approximately 150 degrees C, which was comparable to that of thiolate-protected Au NCs. The photobleaching of Au NCs in water gradually occurred under UV light irradiation (356 nm, 1.3 mW/cm(2)) because of the photoinduced oxidation of Au NCs. After 8 h irradiation, the fluorescence intensity slowly decreased to approximately 50% of the maximum and to approximately 20% after 96 h under the present condition, compared to the photobleaching of CdSe semiconductor quantum dots. We also found that the fluorescence intensity remained to be about 30% of the maximum even in the presence of concentrated 30% H(2)O(2). These findings demonstrate that the photobleaching process under the UV irradiation is effectively suppressed for DMF-protected Au NCs.

Although amphotericin B (AmB) is thought to exert its antifungal activity by forming transmembrane ion-permeable self-assemblies together with ergosterol, no previous study has directly proven AmB-ergosterol interaction. To establish the interaction, we measured (2)H NMR using deuterium-labeled sterols and AmB. The (2)H NMR spectra of deuterated ergosterol in palmitoyloleoylphosphatidylcholine (POPC) bilayers showed that fast axial diffusion of erogosterol was almost completely inhibited by the coexistence of AmB. Conversely, cholesterol mobility in POPC membrane was essentially unchanged with or without AmB. These results unequivocally demonstrate that ergosterol has significant interaction with AmB in POPC bilayers. In addition, we examined the mobility of AmB using deuterium-labeled AmB, and found that, although AmB is almost immobilized in sterol-free and cholesterol-containing POPC membranes, a certain ratio of AmB molecules acquires mobility in the presence of ergosterol. The similar mobility of AmB and ergosterol in POPC bilayers confirmed the idea of the direct intermolecular interaction between ergosterol and AmB.