Various new nucleosides bearing one or two lipophilic groups at the 2′-position have been synthesized. The lipophilic substituents were attached to a 2′-hydroxy, 2′-amino, or 2′-thio function. These lipophilic nucleosidesanchor in large unilamellar POPC vesicles serving as phospholipidmembrane models. The insertion of these molecules into the membranes was investigated by NMR techniques. For comparison
insights into their roles, we aimed to develop functionalized SSEA glycan analogs via chemical synthesis. Herein, we report a convergent synthetic approach for SSEA-3 and SSEA-4 analogs using readily available versatile building blocks. A key step, namely the stereoselective glycosylation of a common tetrasaccharide acceptor, was successfully achieved using a 4-O-Bn Gal donor for SSEA-3 and a Neu-Gal
Neutron Reflection from Hexadecyltrimethylammonium Bromide Adsorbed at the Air/Liquid Interface: The Variation of the Hydrocarbon Chain Distribution with Surface Concentration
作者:J. R. Lu、M. Hromadova、E. A. Simister、R. K. Thomas、J. Penfold
DOI:10.1021/j100095a037
日期:1994.11
We have determined the structure of a monolayer of hexadecyltrimethylammonium bromide adsorbed at the air/water interface at its critical micelle concentration (9.2 x 10(-4) M) and at two lower concentrations using neutron specular reflection. We have used isotopic labeling to determine the relative positions of chains, heads, and solvent, and more detailed labeling to determine the distributions of C-6 chain fragments at either end of the alkyl chains. The use of the more detailed labeling scheme has allowed us to make a quantitative estimate of the contribution of surface roughness to the structure of the layer at the three concentrations, to show that the alkyl chains are, on average, strongly tilted away from the surface normal but that the part of the alkyl chain next to the head group is less tilted. The different tilt angle distributions for the two ends of the hydrocarbon chain also indicate that there are gauche defects in the chain.
Inter- and Intramolecular Temperature-Dependent Vibrational Perturbations of Alkanethiol Self-Assembled Monolayers
by several wavenumbers to higher frequencies as the hydrogenated adsorbates are increasingly diluted in a matrix of fully deuterated C16, showing that all bands are subject to intermolecular couplings. The analysis of the behavior of the C−Hstretching bands suggests that the temperature dependence of the vibrational frequencies associated with the methylene stretching modes is principally due to intermolecular
已在 25-300 K 条件下探索了吸附在 Au(111) 织构表面上的辛硫醇、十二烷硫醇和十六烷硫醇(分别为 C8、C12 和 C16)单分子层的红外光谱。C-H 拉伸模式通常会移动几个波数到较低的频率,并且随着温度的降低强度增加多达 75%,这提供了这些拉伸模式与低能量振动模式耦合等效应的证据。相反,对于低于 300 K 的所有温度,随着氢化吸附物在完全氘化 C16 的基质中越来越稀释,完全氢化的 C16 的 C-H 带的位置移动了几个波数到更高的频率,表明所有带都受到到分子间耦合。