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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]