Gauche defects

Au surfaces yielded analogous results. Here the authors foimd gauche defects only in the second layer, while the first represented a flat lying chain [133]. 

Without 2915-2920 CH2 asymmetric stretching mode d" crystalline PE with gauche-defect [131,133,146]... 

Independent of the contact geometry, the calculations also demonstrated that the introduction of gauche defects resulted in a decrease of the bridge conductance by a factor of 10, as compared to an all-trans alkanedithiol chain (see Fig. 14b, triangles). Due to variations in the number and positions of gauche defects, as well as various contact geometries, the molecular junctions can exhibit conductance values up to two orders of magnitude below the conductance values of an all-trans conformation of the alkyl chain. 

The sequence of low conductance values L is attributed to isomers of alkanedithiols with gauche defects. This interpretation is also supported by the experimentally observed temperature dependence of L conductance values. The alteration of gauche states appears to be an activated process [244]. 

Fig. 6 Calculated inelastic electron tunneling spectra with the different stretching distances offset by 2.5 V-1. The geometries with gauche defects are marked in the right margin for stretching 4.0-7.0 A. Highlighted frequency bands are (1) top, 82 (degenerate C-S) and 130 (C-C) meV, and (2) bottom, 75 (nondegenerate C-S), 95 (rock), 165 (wag), and 365 (C-H) meV. (Reprinted with permission from [60])...

Figure 2. This figure gives a schematic illustration of various fluctuations that exist in lipid bilayers. From top to bottom (1) the increase in area and concomitant reduction in membrane thickness is strongly damped. (2) Up and down movements of the lipids are restricted to small amplitudes, i.e. much less than the tail length. (3) Interpenetration of lipids into the opposite monolayer is, in first approximation, forbidden. (4) Conformations of the lipid tails have only few gauche defects, so that the tail is only slightly curved. Reproduced from (58) with permission from the Biophysical Society...

Removal of the carboxyl group from a BS molecule leaves heneicosane (C21) which exhibits no liquid-crystalline phase, but does form two layered solid phases in which the C21 molecules are fully extended with the molecular axes normal to the layer planes [320]. In the higher temperature solid (Phase II), the molecules are hexagonally packed within and execute hindered rotations about their long axis. In the lower temperature solid (Phase I), the rotational motions are damped and the molecules are orthorhombically packed within a layer. Gauche defects in the preferred al -transoid conformations occur more frequently near layer ends than near the middle of layers... 

The time-resolved spectra from the run of C16 exposed to C12E04 (Figure 3) are quite different from those of the surfactant - free water run. The relative intensity of the end gauche and double gauche defect bands is increased, and the kink defect band bear 1300 cm 1 may be split into a multiplet. In addition, several bands between 1260 and 1200 cm 1 are enhanced, relative to the spectrum of the... 

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