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本文分析了旋光性分子中的螺旋结构,由此得出结论:螺旋结构是引起旋光性的根本原因。右手螺旋一定为右旋的,左手螺旋一定为左旋的。当分子内存在螺旋结构,而这些螺旋结构的旋光性不能完全相互抵消时,这个分子一定有旋光性。从螺旋方向可以预测旋光方向,知道旋光方向以预测螺旋方向,进而预测化合物的构型。 相似文献
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在B3LYP/6-31+G**水平下的溶剂中优化得到4个残基长和5个残基长的α-螺旋. 计算得到的骨架构象与蛋白质晶体结构的统计结果符合得很好. 类似于一般的较长α-螺旋, 观察到了C-端的散开. 对很短的聚丙氨酸肽链, 从焓上看310-螺旋明显比α-螺旋稳定, 然而熵效应不利于310-螺旋结构. 螺旋N2(N-端第二个残基)位上天冬氨酸侧链的加盖(Capping)效应明显使α-螺旋相对310-螺旋更加稳定. 因而, 在同样长度下α-螺旋比310-螺旋多的统计结果能够被理解. 另外, 最短的α-螺旋的C-端倾向于以β-转角结构结束. 相似文献
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三螺旋多糖的链结构与功能研究进展 总被引:1,自引:0,他引:1
三螺旋多糖是自然界中存在的具有特殊链结构的一类生物大分子,它不仅具有较高的生物活性,而且具有特殊的分子识别能力以及其他多糖无法比拟的功能特性。本文主要概述三螺旋多糖的链结构及其构象转变,分析其变性和复性过程中分子链间的相互作用,阐明三螺旋结构形成和形态变化的科学规律。同时,综述了三螺旋多糖的链构象与其生物活性之间的构效关系,以及基于螺旋构象转变构建的多糖基功能材料的最新研究进展。 相似文献
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超分子螺旋聚合物结合了超分子聚合物制备方法简便、结构及性能可调控等优势,相比于人工合成的共价型螺旋聚合物更接近自然界螺旋生物大分子,因而在手性探针、不对称催化以及手性识别和分离等领域具有广泛的应用前景。结合多肽的手性优势、丰富的二次有序构象及其出色的自组装行为,以多肽作为结构基元经超分子组装制备具有螺旋构象的聚合物,不仅丰富了手性/螺旋聚合物的制备途径,同时为多肽材料的功能化应用提供新的广阔前景。本文综述了多肽基元之间经超分子作用诱导形成的超分子螺旋聚合物,总结了双亲性多肽以及多肽拓扑结构对超分子组装过程的影响及其对形成螺旋结构的控制,重点归纳了由多肽构筑的光、温度、pH、金属离子和酶等不同类型智能响应性的超分子螺旋聚合物。 相似文献
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螺旋结构配位聚合物在光学装置、生物模拟化学、非对称催化化学、手性识别、生物结构等多学科领域的应用,引起了人们极大的兴趣。本文综述了氮杂环配体自组装螺旋结构配位聚合物的最新进展,按照咪唑、三唑、吡啶、嘧啶及其衍生物配体分类总结了它们构建螺旋配位聚合物的结构,并简述了通过自发手性识别过程得到纯手性螺旋配位聚合物的影响因素,展望了具有螺旋链状配位聚合物的发展前景以及其开发应用潜能。 相似文献
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螺旋纳米碳纤维的制备与表征 总被引:8,自引:0,他引:8
利用氢电弧等离子体法制备了纳米铜-镍合金作为催化剂,通过乙炔的催化热解制备了对称生长的螺旋纳米碳纤维.并用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和红外(IR)对其进行表征,发现在单个纳米铜-镍合金粒子上对称生长出两根螺旋纳米碳纤维,它们的旋向相反,但是具有相同的螺旋直径、螺旋长度和碳纤维直径,而且纳米铜-镍合金粒子也有各种不同的形状.此外,这两根对称生长的螺旋纳米碳纤维之间的夹角也不同,分别为60°,90°,110°和160°.IR结果表明,螺旋纳米碳纤维分子结构中既含有不饱和的CC双键,又含有饱和的—CH2—和—CH3—基团.然而,利用氢电弧等离子体法制备的纳米铜和纳米镍作为催化剂,催化热解乙炔,得到的产物均是直线型碳纤维. 相似文献
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螺二芴富勒烯吡咯烷衍生物的合成及电化学和光限幅性能 总被引:1,自引:1,他引:0
设计合成了3种新颖的螺二芴键联富勒烯(C60/C70)吡咯烷衍生物,其结构通过IR,1HNMR,13CNMR和MALDI-TOF进行确证,其电化学性质用循环伏安法进行研究.结果表明,C70衍生物6的还原电位较C60衍生物7分别向负电势移动0.1,0.12和0.01V.同时,使用纳秒和飞秒激光分别研究了化合物6,7和8的光限幅性能,其光限幅阈值分别为15.3,23.3和13.7J/cm2,表明这些材料具有优异的光限幅性能. 相似文献
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Angel Rumbero Isabel Borreguero Jos V. Sinisterra Andrs R. Alcntara 《Tetrahedron》1999,55(52):2549-14960
Different racemic or prochiral phenyl alkane (l,n)-diols were synthesized, and their resolution was carried out by two different strategies: enzymatic transesterification with vinyl acetate, or enzymatic hydrolysis of their corresponding diacetates, in both cases catalysed by porcine pancreatic lipase (PPL). The absolute configuration of the optically enriched reaction products was determined by formation of Mosher's esters or by the use of the Benzene Sector and Benzene Chirality Rules as obtained from the Circular Dichroism spectra. 相似文献
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He J Nie A He M He X Yu Z Ye X Xing Q 《Rapid communications in mass spectrometry : RCM》2000,14(9):765-771
A series of cyclic esters, which are optically active as a consequence of their helical structures, were synthesized to investigate the relationships between their structures and their optical activities. This paper reports the electron impact fragmentation mechanisms of these six cyclic esters. Accurate mass measurements and mass analyzed ion kinetic energy spectrometry confirmed fragmentation patterns. The stability of the fragment ions has a great influence on the fragmentation pathways, but no correlation with the optical activity was found. 相似文献
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The condensation of 1-alkoxy-1,3-butadienes with optically active esters of glyoxylic acid leading to esters of 2-alkoxy-5,6-dihydro-2H-pyran-6-carboxylic acids was studied and the dependence of asymmetric induction on the following parameters examined: alkoxy group in dienes, dissymetric group in glyoxylates, solvent and the temperature of condensation. The optical yield and absolute configuration of the adducts were determined by optical rotation measurements of methyl malate obtained by degradation. The data are rationalized by postulating parallel formation of four active complexes corresponding to a transoid and cisoid conformation of the glyoxylate ester in the transition state. 相似文献
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Gwang‐Su Byun Sang Youl Kim Iwhan Cho 《Journal of polymer science. Part A, Polymer chemistry》2006,44(3):1263-1270
(?)‐(1S,2R)‐Norbornene‐2‐carboxylic acid alkyl esters (alkyl = Me, Bz, L ‐menthyl, or D ‐menthyl) were successfully prepared by the Diels–Alder reaction of cyclopentadiene with (R)‐(?)‐pantolactone‐O‐yl acrylate followed by epimerization and column chromatography. The enantiomeric excess was 99.9%. These monomers were polymerized by Pd(II)‐based catalysts, and high yields of the polymers were obtained. The methyl ester gave an optically active polymer of high optical rotation (monomer [α]D = ?24.7, polymer [α]D = ?98.5). This high rotation value of the polymer was attributed to the isotactic chain regulation of the polymer. This high rotation was not observed with methyl esters prepared by the transesterification of menthyl esters. The stereoregular polymer exhibited notable resonance peaks at 39 ppm in 13C NMR spectra. No crystallinity was observed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1263–1270, 2006 相似文献
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J. A. L. Sastre R. N. Miguel A. G. Ramos D. Galisteo 《Journal of Molecular Structure》2000,526(1-3):1-15
The molecular optical rotation of a six-membered series of cyclic compounds has been calculated with a simple method which relates the sign and magnitude of the molecular optical rotation to the geometry, conformation and absolute configuration of the studied compounds. The optimised geometry of each conformer was calculated by molecular mechanics calculations. The values obtained seem to confirm the existence of a close relationship between the value of molecular optical rotation of a compound and its geometry. 相似文献
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从(-)-(1S,2R,4S)-5,6-二亚甲基双环[2.2.1]庚-2-醇(I)和(-)-(1S,2S,4S)-5,6-二亚甲基双环[2.2.1]庚-2-醇(Ⅱ)出发,合成了它们的醚类和取代苯甲酸酯类光学纯的衍生物。通过[α]D测定和构型分析,发现它们是含有3个手性碳(C1,C2和C4)的桥环化合物,其旋光性与构型的关系均符合可极化度多级圆球不对称性模型。 相似文献
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Novel isosorbide derivative containing perfluorocarbon group,bi(perfluorooctanesulfonyl)isosorbide ester as chiral dopant in liquid crystal,was synthesized.Chemical structure was characterized by elemental analysis,FT-IR,1H NMR and 19F NMR.The optical texture of the mixture was observed by polarized optical microscopy(POM).Novel chiral dopant containing perfluorocarbon group had excellent optical activity.Its specific rotation and molar rotation were noticeable higher than those of bi(4-chloromethylbenzenecarbonic)isosorbide ester.The fluorocarbon group improved the molar rotation of chiral compound and did not affect optical rotation direction.The texture of the mixture added isosorbide derivative with fluorocarbon group showed the oily streak texture. 相似文献