共查询到20条相似文献,搜索用时 15 毫秒
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Two peptides, derived from the reactive center of ovalbumin (OVARC) and plasminogen activator inhibitor‐1 (PAIRC) respectively were chemically synthesized and investigated by circular dichroic spectroscopy. The secondary structural transformation in solution and in solid state was studied. OVARC shows a nascent helical structure in aqueous solution, and its helical content increases under acidic conditions. There is no obvious structural conversion from solution to solid state. PAIRC, however, undergoes a structural transformation from random coil in aqueous solution to a typical β‐sheet structure in the solid state. Hexafluoroisopropanol (HFIP) prompts helical structures of the two peptides in solution, but it seems to trigger the structural formation of β‐sheets in solid state. The novel structural transformation from random coil or nascent helical structure in aqueous solution to the α‐helix in HFIP and to the β‐sheet structure in solid state may reflect the conformational polymorphism of the serpin reactive centers and is implicated in the structural features of the amyloid aggregates. 相似文献
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Benjamin H. Strudwick Mark A. J. Koenis Hans J. Sanders Valentin P. Nicu Sander Woutersen Prof. Wybren Jan Buma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(54):12560-12566
Vibrational circular dichroism (VCD) studies are reported on a chiral compound in which a fullerene C60 moiety is used as an electron acceptor and local VCD amplifier for an alanine-based peptide chain. Four redox states are investigated in this study, of which three are reduced species that possess low-lying electronic states as confirmed by UV/Vis spectroelectrochemistry. VCD measurements in combination with (TD)DFT calculations are used to investigate (i) how the low-lying electronic states of the reduced species modulate the amplification of VCD signals, (ii) how this amplification depends on the distance between oscillator and amplifier, and (iii) how the spatial extent of the amplifier influences amplification. These results pave the way for further development of tailored molecular VCD amplifiers. 相似文献
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Alexander von Weber Matthias Jakob Eva Kratzer Dr. Aras Kartouzian Prof. Ueli Heiz 《Chemphyschem》2019,20(1):134-141
In this work, we present an experimental setup for the in situ and ex situ study of the optical activity of samples, which can be prepared under ultra-high vacuum (UHV) conditions by second-harmonic generation circular dichroism (SHG-CD) over a broad spectral range. The use of a racemic mixture as a qualified reference for the anisotropy factor is described and, as an example, the chiroptical properties of 1.5 μm thick (multilayers) as well as sub-monolayer thin films of the R- and S-enantiomer of 1,1′-Bi-2-naphthol (BINOL) evaporated onto BK7 substrates were investigated. 相似文献
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This Minireview is a critical survey of results accumulated during the last decade on the characterization of carbon nanotubes using a combination of electrochemical and spectroscopic methods. The article updates earlier reviews on the topic with special emphasis to recent progress in the field. 相似文献
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Alison Domzalski Liliana Margent Valeria Vigo Faizunnahar Dewan Naga Vara Kishore Pilarsetty Yujia Xu Akira Kawamura 《Molecules (Basel, Switzerland)》2021,26(19)
2,5-diketopiperazines (DKPs) are cyclic dipeptides ubiquitously found in nature. In particular, cyclo(Phe-Pro), cyclo(Leu-Pro), and cyclo(Val-Pro) are frequently detected in many microbial cultures. Each of these DKPs has four possible stereoisomers due to the presence of two chirality centers. However, absolute configurations of natural DKPs are often ambiguous due to the lack of a simple, sensitive, and reproducible method for stereochemical assignment. This is an important problem because stereochemistry is a key determinant of biological activity. Here, we report a synthetic DKP library containing all stereoisomers of cyclo(Phe-Pro), cyclo(Leu-Pro), and cyclo(Val-Pro). The library was subjected to spectroscopic characterization using mass spectrometry, NMR, and electronic circular dichroism (ECD). It turned out that ECD can clearly differentiate DKP stereoisomers. Thus, our ECD dataset can serve as a reference for unambiguous stereochemical assignment of cyclo(Phe-Pro), cyclo(Leu-Pro), and cyclo(Val-Pro) samples from natural sources. The DKP library was also subjected to a biological screening using assays for E. coli growth and biofilm formation, which revealed distinct biological effects of cyclo(D-Phe-L-Pro). 相似文献
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Dr. Marcin Górecki Dr. Filippo Lipparini Dr. Gianluigi Albano Dr. Tamás Jávorfi Dr. Rohanah Hussain Dr. Giuliano Siligardi Prof. Gennaro Pescitelli Prof. Lorenzo Di Bari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(4):e202103632
Solid-state ECD (ss-ECD) spectra of a model microcrystalline solid, finasteride, dispersed into a KCl pellet were recorded by using the synchrotron radiation source at the Diamond B23 beamline. Scanning a surface of 36 mm2 with a step of 0.5 mm, we measured a set of ECD imaging (ECDi) spectra very different from each other and from the ss-ECD recorded with a bench-top instrument (1 cm2 area). This is due to the anisotropic part of the ECD (ACD), which averages to zero in solution or on a large number of randomly oriented crystallites, but can otherwise be extremely large. Two-way singular value decomposition (SVD) analysis, through experimental and simulated TDDFT spectra, disclosed that the measured and theoretical principal components are in line with each other. This finding demonstrates that the observed isotropic ss-ECD spectrum is governed by the anisotropy of locally oriented crystals. It also introduces a new quality for ss-ECD measurements and opens a new future for probing and mapping chiral materials in the solid state such as active pharmaceutical ingredients (APIs). 相似文献
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火菇素的圆二色性与溶液二级结构 总被引:1,自引:0,他引:1
为了弄清火菇素蛋白的结构与功能的关系并揭示抗癌机理,使其更好地发挥临床作用,测定了火菇素的圆二色性,并用蛋白质二级结构解析程序分析了火菇素的溶液二级结构。火菇素远紫外圆二色性的研究表明,其水溶液在208nm处表现为宽大负峰,最大平均残基摩尔椭圆度[θ]~2~0~8=-6574deg·cm^2·dmol^-^1,在223nm处为肩,经二级结构解析程序计算分析,火菇素的二级结构和二硫键和芳香氨基酸对火菇素圆二色性的贡献分别为77.4%和22.6%,二级结构的组成为:α-螺旋19.7%,β-折叠和β-转角50.1%,无规卷曲和γ-转角30.2%。火菇素二级结构对pH,SDS和乙醇有一定的稳定性,在pH4.6~9.4范围内,火菇素的结构几乎不发生变化,但在碱性太强的环境中火菇素发生不可逆变性,火菇素对热变性很敏感。 相似文献
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Zi Pin ZHANG Bao Kang JIN Yu Peng TIAN Shi Jun WANG 《中国化学快报》2005,16(12):1621-1624
Mechanisms of electron transfer of carbazole (CZ) and 9-ethylcarbazole (ECZ) were studied by electrochemistry and in-situ spectroelectrochemistry. The result indicated that the electrochemical reaction mechanism of ECZ was the same as that of CZ. Both of them undergo ECE process: the initial step is removal of one electron to generate very reactive cation radical, this species then proceeded by deprotonation-coupling reaction to form the corresponding dimer, which was oxidized continuously. 相似文献
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Daniele Toffoli Marco Medves Giovanna Fronzoni Emanuele Coccia Mauro Stener Luca Sementa Alessandro Fortunelli 《Molecules (Basel, Switzerland)》2022,27(1)
We report a computational study at the time-dependent density functional theory (TDDFT) level of the chiro-optical spectra of chiral gold nanowires coupled in dimers. Our goal is to explore whether it is possible to overcome destructive interference in single nanowires that damp chiral response in these systems and to achieve intense plasmonic circular dichroism (CD) through a coupling between the nanostructures. We predict a huge enhancement of circular dichroism at the plasmon resonance when two chiral nanowires are intimately coupled in an achiral relative arrangement. Such an effect is even more pronounced when two chiral nanowires are coupled in a chiral relative arrangement. Individual component maps of rotator strength, partial contributions according to the magnetic dipole component, and induced densities allow us to fully rationalize these findings, thus opening the way to the field of plasmonic CD and its rational design. 相似文献
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Dr. Tao Wu Guojie Li Dr. Josef Kapitán Dr. Jiří Kessler Prof. Yunjie Xu Prof. Petr Bouř 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22079-22082
Previously, we and other laboratories have reported an unusual and strong Raman optical activity (ROA) induced in solvents by chiral dyes. Various theories of the phenomenon appeared, but they were not capable of explaining fully the observed ROA band signs and intensities. In this work, an analysis based both on the light scattering theory and dedicated experiments provides a more complete understanding. For example, double-cell magnetic circular dichroism and magnetic ROA experiments with copper-porphyrin complex show that the induced chirality is observed without any contact of the solvents with the complex. The results thus indicate that a combination of electronic circular dichroism (ECD) with the polarized Raman scattering is responsible for the effect. The degree of circularity of solvent vibrational bands is a principal molecular property participating in the event. The insight and the possibility to predict the chirality transfer promise future applications in spectroscopy, chemical analysis and polarized imaging. 相似文献
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去甲肾上腺素电极过程的圆二色谱电化学研究 总被引:3,自引:0,他引:3
现场圆二色薄层光谱电化学研究去甲肾上腺素的电化学氧化还原过程 .研究表明去甲肾上腺素 ( pH =7.0磷酸缓冲溶液中 )在玻碳电极上经历了不可逆的电化学氧化 ,且遵从后行化学反应 (EC)机理 ,去甲肾上腺素醌和去甲肾上腺素红的再还原遵从简单电子转移 (E)机理 .由双对数法获得去甲肾上腺素电化学氧化的式电位为E10’=0 .2 0V ,电子转移系数和电子转移数之积为αn =0 .38,标准复相电极反应常数k10 =1 .2× 1 0 -4 cm·s-1.去甲肾上腺素醌和去甲肾上腺素红的电化学还原反应参数分别为E2 0’=0 .2 5V ,αn =0 .37,k2 0 =4.4× 1 0 -5 cm·s-1和E3 0’=- 0 .2 5V ,αn =0 .33,k3 0 =1 .1× 1 0 -4 cm·s-1. 相似文献
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Yasuko Ishizuka Yoshinobu Nagawa Hiroshi Nakanishi Akira Kuboyama 《Journal of inclusion phenomena and macrocyclic chemistry》1990,9(3):219-225
Two aromatic rings of a phlorizin molecule form inclusion complexes with -CD and -CD. Induced circular dichroism spectra of these complexes have been measured to estimate the orientation of the two aromatic rings in the hydrophobic space of CDs. Apparent complex formation constants have been also estimated for each complex. It is concluded that phlorizin forms a stronger inclusion complex with -CD than with -CD. 相似文献
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Hong-Li Xuan Yu-Feng Sang Prof. Liang-Jin Xu Da-Sheng Zheng Cui-Mi Shi Prof. Zhong-Ning Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(48):e202201299
Circular polarized luminescence (CPL)-active materials attract great attentions owing to their widely applications in 3D optical displays and encrypted transmission. Inspired by the strategies adopted in perovskite based CPL materials, herein, CPL-active hybrids (D)- and (L)-(tert-butyl prolinate)MnCl3 were successfully prepared by assembling chiral D/L tert-butyl prolinate with manganese (II) chloride. Single crystal structures show the as-formed hybrids possess one-dimensional (1D) structure containing linear chains of face-sharing MnCl6 octahedral surrounded by prolinate cations. The 1D Mn(II) hybrids display strong red emission peaked at 646 nm with PLQY of 67.1 % and 57.2 % for d -type and l -type, respectively, representing the highest PLQY for 1D MnII hybrids. Interestingly, the 1D Mn(II) hybrids exhibit prominent circular dichroism (CD) signals and remarkable CPL activity with the dissymmetry factor g of 6.1*10−3 and −6.3*10−3 from 550 to 800 nm for (D)- and (L)-(tert-butyl prolinate)MnCl3, respectively, owing to the existence of chiral cations. It is worthy noted the obtained g represents the highest value for non-lead organic–inorganic hybrids. 相似文献
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三波长光度法测定姬松茸中麦角甾醇含量 总被引:7,自引:0,他引:7
应用三波长光度法测定了姬松茸菌丝体中麦角甾醇的含量。先采用薄层色谱将待测正庚烷萃取液中的麦角甾醇和其它杂质分离,然后分别进行紫外扫描,确定三波长为272,282和292nm,计算出ΔA,因ΔA仅与姬松茸菌丝体中麦角甾醇含量相关而不受杂质影响,从而有效地消除了杂质紫外吸收的干扰。回归方程为:ΔA=0.00403C 0.001048,相关系数r=0.9996,麦角甾醇的浓度在0~50mg/L范围内,ΔA与浓度C之间呈良好的线性关系。本法的相对标准偏差RSD为1.2%(n=5),回收率为97.5%~102.5%。方法的精密度与准确度令人满意,所得结果与HPLC法相近,而且操作简便易行。 相似文献
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In order to control the fabrication method, the mechanism used in the formation of DNA templated nanowires is investigated through circular dichroism (CD) spectroscopy. Metallic (Au) and magnetic (Fe2O3 and CoFe2O4) nanoparticles (NP) are aligned along the DNA strand at various mass ratios. The DNA templated nanowires are compared to the structure of B‐form dsDNA through CD experiments. Absorbance and thermal melting tests are performed to verify the structural changes of DNA templated nanowires. Low concentrations of nanoparticles preserve the DNA B‐form through electrostatic interactions. Conversely, at higher concentrations of nanoparticles aligned along the DNA strand, the template is denatured. Information on the mode of nanoparticle binding and DNA helix alterations are explored for metallic and magnetic nanowires based upon the results. 相似文献
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Craig A. Parish Jian-Guo Dong William G. Bornmann Joan Chang Koji Nakanishi Nina Berova 《Tetrahedron》1998,54(52):2717-15758
The analysis of a series of seventeen vinblastine analogs by circular dichroism is described. Exciton coupling of the indole and indoline chromophores of these compounds provides a general, non-empirical method for the assignment of the C16′ configuration with the bioactive C16′-S and the inactive C16′-R analogs giving rise, respectively, to positive and negative couplets. An analysis of the non-coupled transitions of the CDs indicates that a positive Cotton effect at 305 nm, although empirical, is associated with bioactivity. Theoretical calculations of the UV and CD spectra of vinblastine diastereomers are also described. 相似文献
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本文利用红外光谱电化学循环伏吸法,对碱性体系下甲醇在Pt电极上的氧化过程的中间产物进行分析和研究。结果表明,碱性体系中,CH3OH在Pt电极上具有较好的电化学活性,存在和在酸性体系中不同的反应机理。利用现场红外差谱对氧化过程的产物进行分析,对生成的产物进行指认,并未发现毒化中间产物COL的生成。运用红外光谱电化学循环伏吸及导数伏吸法,对生成的中间体的生成过程进行分析和指认,结果表明:CH3OH的氧化中间产物为HCOO-,在碱性体系下,会继续转化为CO2,CO32-和HCO3-。 相似文献