On Interpretation of Spectra of Photochemically Induced Circular Dichroism of Semiconductor Nanocrystals

Optics and Spectroscopy - We propose an approach to the analysis and interpretation of spectra of photoinduced circular dichroism (PICD) of semiconductor nanocrystals, in particular, quantum dots,...     

Magnetic Circular Dichroism Spectra of p-Disubstituted Benzenes Possessing Both Electron-Donating and Accepting Groups

Abstract

The magnetic circular dichroism (MCD) and absorption spectra of some p-disubstituted benzenes possessing both electron-donating and accepting groups were measured. The electronic spectra of the above compounds are characterized by the appearance of two absorption bands, one of which appears at 25000–40000 cm^?1 region with large intensity, and another at 40000–50000 cm^?1 region with rather small intensity. These absorption bands, especially the latter one, have been investigated by means of the MCD spectra and molecular orbital calculations based on the Pariser-Parr-Pople method.     

Magnetic Circular Dichroism Study of Analogues of the DNA Binding Ligands Netropsin and Distamycin A

UV absorption and MCD data of a complete series of netropsin-like oligopeptides containing between one and five N-methyl-pyrrole residues are reported. The presence of three MCD bands in the region between 220 and 350 nm can be related to the resonance of the peptide groups with the methylpyrrole systems of the oligopeptides. The longest wavelength absorption bands of all netropsin-like compounds investigated are ascribed to two electronic transitions of the resonance methypyrrole-carboxamide units. - Complex formation with DNA affects these MCD bands and hence modifies the transitions. This is explained by hypercon-jugation in the chromophoric system as a result of specific hydrogen bonding of peptide groups with dA·dT pairs of double stranded DNA.     

Photochemically Induced Circular Dichroism of Semiconductor Nanocrystals

Optics and Spectroscopy - Here, we report an investigation of optical activity which was photochemically induced by illumination of QRs and DiRs with circularly polarized light; the photo-induced...     

圆二色光谱及其在药物研究方面的应用

对圆二色光谱技术在手性化合物分析中的应用进展进行综述,简单介绍了圆二色光谱的原理和特点,着重阐述了圆二色光谱在药物研究领域中的应用,初步探讨了HPLC-CD联用在该领域的应用.     

Interaction of Imidacloprid with Hemoglobin by Fluorescence and Circular Dichroism

Imidacloprid belongs to a major new class of insecticides, called neonicotinoids, which are accounting for 11–15% of the total insecticide market. The binding characteristics of insecticide imidacloprid with hemoglobin (Hb) have been studied by employing different spectroscopic techniques. The results proved the formation of complex between imidacloprid and Hb. Hydrophobic interaction and hydrogen bond dominated in the association reaction. Hydrophobic probe 8-anilino-1-naphthalenesulfonic acid (ANS) competitive experiments indicated that the binding of imidacloprid to Hb primarily took place in hydrophobic regions. The distance between Hb donor and acceptor imidacloprid was 4.88 nm as derived from Förster’s theory. Alternations of Hb secondary structure in the presence of imidacloprid were confirmed by synchronous fluorescence, circular dichroism (CD) and three-dimensional fluorescence spectra. This study enriches our understanding of toxic effect of imidacloprid to the physiologically important protein Hb.     

Third International Synchrotron Radiation Circular Dichroism Spectroscopy Meeting

The International Synchrotron Radiation Circular Dichroism (SRCD) Spectroscopy Meeting was held at the Physikzentrum, Bad Honnef, Germany on May 17–20, 2015, as the 590^th WE-Heraeus-Seminar. It was the third in the series of SRCD Workshops, following the first one held at the Daresbury Synchrotron (UK) in 2001, and the second at the Beijing Synchrotron Radiation Facility (BSRF) and the Institute of High Energy Physics (IHEP) in 2009. SRCD2015 was organized by Dr. Jochen Bürck, Prof. Anne Ulrich, and Dr. Dirk Windisch (all of Institute of Biological Interfaces (IBG-2), Karlsruhe Institute of Technology, Germany) and Prof. Bonnie Ann Wallace (Birkbeck College, University of London, UK). It was aimed at both synchrotron CD beamline scientists and scientific users of the beamlines, and included participants from 14 countries. For the first time, representatives of all operational SRCD beamlines worldwide were present at the same meeting, and scientists developing two new SRCD beamlines also participated.     

Magnetic Circular Dichroism Studies XLVII. Cyclobutanones and Acyclic Ketones

The magnetic circular dichroism spectra of some substituted cyclobutanones and acyclic ketones are presented. The magneto-optical B-values are shown to depend upon the number of α-alkyl substituents which lie out of the plane of the carbonyl chromophore, and upon the molecular symmetries.     

Two- and Three-Photon Linear Circular Dichroism in Semiconductors of Cubic Symmetry

Russian Physics Journal - The linear-circular dichroism of two- and three-photon absorption of light in semiconductors of hole conductivity with cubic symmetry is theoretically investigated. The...     

On the Calculation of an X-Ray Natural Circular Dichroism Signal

The sequential derivation of an expression that describes an X-ray natural circular dichroism (XNCD) signal in the most general case is performed. The obtained expression is used as a basis to consider XNCD signals and their structural origins in copper metaborate CuB₂O₄ crystals at an incident radiation energy near the K absorption edge of copper and lanthanum–gallium silicate La₃Ga₅SiO₁₄ crystals at an incident radiation energy near the K absorption edge of gallium. It has been demonstrated that the measurements of circularly polarized X-ray absorption spectra in combination with corresponding first-principle calculations provide an efficient method for studying the contributions of crystallographically non-equivalent atoms to the X-ray optical activity of crystals.     

Recent Studies of the Circular Dichroism and Optical Rotatory Dispersion of Biopolymers

When electromagnetic radiation interacts with matter, a number of changes result both in the light and in matter. The intensity of the light at given wavelength may be reduced due to absorption; the velocity of light may change, dependent on the wavelength, upon interaction with the medium due to refractive index dispersion (scattering). If the incident light is plane polarized, a change in the plane of polarization may occur, again dependent on wavelength [optical rotatory dispersion (ORD)]. Also, the radiation may become elliptically polarized at the absorption bands; this phenomenon is termed circular dichroism (CD). While normal absorption and dispersion occur with any molecule, ORD and CD require not only polarized light but also molecular systems with built-in asymmetry or dissymmetry.     

Bulk and Surface Effects in X-Ray Magnetic Circular Dichroism of Iron Clusters

General trends in x-ray magnetic circular dichroism (XMCD) spectra of iron clusters of different sizes are theoretically investigated using the fully-relativistic spin-polarized multiple-scattering formalism. Purely geometrical effects of clustering and cluster-size effects are explored separately from effects of various scattering potentials and/or treatment of the surface barrier. We found that a high portion of non-bulk atoms makes the XMCD spectra of iron clusters to appear significantly different from bulk spectrum, even for quite large clusters. If the vacuum surrounding the cluster is taken into account, XMCD spectra of iron clusters change essentially (in comparison with clusters cut out of the bulk or with clusters embedded in a sea of free electrons).     

一对手性大环配体及其配合物的合成与圆二色光谱

以水杨醛衍生物、手性1,2-丙二胺为原料,制备了两个手性大环配体R-L（亚甲基双水杨醛缩R-1,2-丙二胺）和S-L（亚甲基双水杨醛缩S-1,2-丙二胺）,这一对手性大环配体与镍盐反应得到了两个手性双核镍配合物Ni₂（R-L）和Ni₂（S-L）;通过红外光谱、紫外光谱、元素分析对其进行了表征。此外,圆二色光谱进一步证明两个手性配体及两个双核配合物互为对映异构。     

苯丙氨酸桥联金属双卟啉的诱导圆二色光谱研究

本文报道了邻位和对位桥联苯丙氨酸锌双卟啉的合成,考查了双卟啉的分子结构对诱导圆二色性的影响。结果表明,两个卟啉环之间的π－π堆积和手性激子偶合作用是影响此类双卟啉圆二色光谱的主要因素。     

On the Conformation of Bilirubin Dimethyl Ester from Circular Dichroism Spectroscopy

Unlike the parent diacid, the dimethyl ester of (αR,α'R)-dimethylmeso-bilirubin-XIIIα exhibits only a weak bisignate circular dichroism (CD) spectrum in a wide variety of solvents. This implies a loss of conformation stabilization afforded (in the diacid) by intramolecular hydrogen bonding, and with it the loss of an allosteric effect that forces the parent acid into the P-helicity conformational enantiomer.     

BioCD-2008: Synchrotron Radiation Circular Dichroism Spectroscopy of Proteins and Other Biomolecules

A weeklong workshop focusing on circular dichroism (CD) spectroscopy using both conventional and synchrotron sources (SRCD) was presented at the National Synchrotron Light Source at Brookhaven National Laboratory from June 23–27, 2008.     

X-Ray Magnetic Circular Dichroism Measurement of Fe-Co Alloy Films Prepared by Electrodeposition

The macro- and micro-magnetic properties of Fe-Co alloy films eletrodeposited on CaAs（100） are studied by synchrotron radiation x-ray magnetic circular dichroism （XMCD） in combination with the magneto-optical Kerr effect （MOKE） measurements and magnetic force microscopy （MFM）. The orbital and spin magnetic moments of each element in the Fe-Co alloy are determined by the sum rules of XMCD. Element-specific hysteresis loops （ESHL） are obtained by recording the La MCD signals as a function of applied magnetic field. MOKE results reveal that the amorphous films are magnetically isotropic in the surface plane. The MFM image shows that the dimension of the magnetic domains is about 1-2 #m, which is much larger than that of the grains, indicating that there are intergranular correlations among these grains. Both ESHL and MOKE hysteresis loops indicate the strong ferromagnetic coupling of Fe and Co in the alloy films.