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This article describes a computational study on dimeric zinc porphyrin tweezer complexes with primary/secondary amines and secondary alcohols that validates the use of Optimized Potential for Liquid Simulations (OPLS‐2005) as the lead computational choice for assisting the tweezer methodology in the absolute configurational assignment of organic compounds. A supramolecular, microscale approach known...
Two novel optically active terthiophene and bithiophene monomers bearing at the C‐β position of thiophene ring an enantiomerically pure chiral alkyl group, namely 3,3″‐di[2‐((S)‐(+)‐2‐methylbutoxy)ethyl]‐2,2′:5′,2″‐terthiophene and 3,3′‐di[2‐((S)‐(+)‐2‐methylbutoxy)ethyl]‐2:2′‐bithiophene, have been synthesized and characterized. Being symmetrically substituted, their polymerization adopting simple...
Flavopiridol is a potent cyclin‐dependant kinase (CDK) inhibitor and is in clinical trials for anticancer treatment. A limiting factor in its drug development has been the high dosage required in human clinical trials. The high dosage is suggested to be necessary because of significant flavopiridol binding to human blood serum. Albumin is the major protein component of blood serum and has been suggested...
Because of the increased use of circular dichroism (CD) spectroscopy as a routine technique by nonspecialists to determine the conformational/configurational properties of biomolecules, we have decided to present here some criteria to accurately check the ordinate scale calibration of a CD spectrometer particularly in the critical low‐wavelength UV region, to understand, and correct, where possible,...
The electronic circular dichroism (CD) spectra were recorded for three diastereomeric eclipsed–staggered pairs of charge‐transfer cyclophanes with different substituents, i.e., (4Rp;12Rp)‐ and (4Sp;12Rp)‐12,15‐dimethoxy[2.2]paracyclophane‐4,7‐dicarboxylic acid derivatives (1a‐c and 2a‐c, where a, b, and c denote methyl ester, carboxylic acid, and carboxylate, respectively). The effects of altering...
The optical rotation of natural amino acids becomes more positive when the medium is changed from approximately neutral to strongly acidic (Clough–Lutz–Jirgensons (CLJ) effect). In this work, it is shown by time–dependent density functional computations that the effect can be generalized to other α–substituted chiral carboxylic acids. The physical origin of the generalized CLJ effect is similar to...
Circular dichroism (CD) has become an increasingly important tool in the study of biological molecules as it enables structural information to be obtained nondestructively on solution‐phase samples. However, sample requirements for CD are often seen as being too high with protein backbone measurements in standard cuvettes typically requiring ∼100–300 μL of 0.1 mg/ml protein. To address this issue,...
The compounds I–IV derived from α‐D‐cyclodextrin moiety by bridging and/or interconnecting with various patterns of disulfide bonds were chosen as models for the spectroscopic study of conformation of the disulfide bridge. The energy gap between the disulfide and cyclodextrin's electronic transitions allows us to investigate absorption and electronic circular dichroism spectra without disturbing spectral...
We describe herein the use of a flexible biphenyl moiety as efficient chirality probe in the assignment of the absolute configuration (AC) of aliphatic, non‐chromophoric diols. The diols are transformed in the corresponding biphenyl dioxolanes in which the biphenyl system has either a P or M torsion depending on the chirality of the diol. As the correlation between biphenyl torsion and diol AC has...
Despite that a number of experimental and theoretical investigations have been carried out to determine the structure of trialanine in water, the reported populations of polyproline II (PPII) and β‐strand conformers vary and were found to be dependent on which spectroscopic method was used. Such discrepancies are due to limitations of different spectroscopic methods used. Here, the temperature‐ and...
Chiral symmetry breaking occurs during vortex‐assisted crystallization of several simple compounds leading to a stochastically determined emergence of an enantiomeric excess of one chiral isomer. This article summarizes recent developments in studies of a similar phenomenon observed in agitated solutions of aggregating insulin, when a phase transition—precipitation of insoluble amyloid fibrils from...
Using dihydrogendisulphide (H2S2), dimethyl‐ ((CH3)2S2), and diethyldisulphide ((CH3CH2)2S2)as model molecules, theoretical ECD, VCD, and ROA spectra of nonplanar disulphides were calculated by DFT methods. Most of the calculated electronic and vibrational chiroptical features suffer an equivocal relation between calculatedsigns of ECD, VCD, or ROA and the sense of disulphide nonplanarity as noted...
The interaction between quercetin, a popular antioxidant flavonoid, and human serum albumin (HSA) is investigated and characterized by means of induced circular dichroism and saturation transfer difference NMR. These techiques demonstrate the reversible binding of quercetin to the carrier protein, which is responsible for its dissolution in aqueous medium. Competition experiments with two classical...
When catechins are found in plant extracts, they are almost always identified as catechin and/or epicatechin probably due to stereoselectivity of the enzymes involved in the biosynthesis of these substances. However, the lack of reports regarding to ent‐catechin as well as ent‐epicatechin does not necessarily mean that these compounds have not been produced. In fact, most of the previous reports used...
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