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Conformational isomerism

About: Conformational isomerism is a research topic. Over the lifetime, 11563 publications have been published within this topic receiving 199312 citations.


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Journal ArticleDOI
TL;DR: In this article, a conformational analysis of 7-acetoxy-6-(2,3-dibromopropyl)-4,8-dimethylcoumarin molecule (abbreviated as 7ADDC) was performed by using ab initio Hartree-Fock (HF) method with 3-21G as the basis set to find the most stable form of 7ADdc.

206 citations

Journal ArticleDOI
TL;DR: Five conformers are distinguished among the large number of possible states of the conformational dynamic ensemble: BSA1,8‐ANS, BSA2,6‐ANS', BSAfree, B SAbis‐ans, and BSAunfolded among theLarge number of state-based ligand interactions and the relative population of each distinguishable conformer depends on the type and concentration of ligand and the temperature of the system.
Abstract: The interaction between ligands and proteins usually induces changes in protein thermal stability with modifications in the midpoint denaturation temperature, enthalpy of unfolding, and heat capacity. These modifications are due to the coupling of unfolding with binding equilibrium. Furthermore, they can be attained by changes in protein structure and conformational flexibility induced by ligand interaction. To study these effects we have used bovine serum albumin (BSA) interacting with three different anilinonaphthalene sulfonate derivatives (ANS). These ligands have different effects on protein stability, conformation, and dynamics. Protein stability was studied by differential scanning calorimetry and fluorescence spectroscopy, whereas conformational changes were detected by circular dichroism and infrared spectroscopy including kinetics of hydrogen/deuterium exchange. The order of calorimetric midpoint of denaturation was: 1,8-ANS-BSA > 2,6-ANS-BSA > free BSA >> (nondetected) bis-ANS-BSA. Both 1,8-ANS and 2,6-ANS did not substantially modify the secondary structure of BSA, whereas bis-ANS induced a distorted α-helix conformation with an increase of disordered structure. Protein flexibility followed the order: 1,8-ANS-BSA < 2,6-ANS-BSA < free BSA << bis-ANS-BSA, indicating a clear correlation between stability and conformational flexibility. The structure induced by an excess of bis-ANS to BSA is compatible with a molten globule-like state. Within the context of the binding landscape model, we have distinguished five conformers (identified by subscript): BSA1,8-ANS, BSA2,6-ANS, BSAfree, BSAbis-ANS, and BSAunfolded among the large number of possible states of the conformational dynamic ensemble. The relative population of each distinguishable conformer depends on the type and concentration of ligand and the temperature of the system.

205 citations

Journal ArticleDOI
TL;DR: In this paper, the stereochemical behavior of N -acyl and N -aroylhydrazones of aromatic aldehydes, of pyruvates and of acetone, in polar and less polar solvents, has been studied by HPLC and by NMR techniques.

203 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that the OH group in the unmodified phenol unit is permeable through the calix[4]arene ring, and several conformational isomers become equivalent after the oxygen-through-the-annulus rotation of the HO group and the number of possible homologs is reduced to 13.

202 citations

Journal ArticleDOI
TL;DR: Detailed analyses of the solid-state Möbius structures of compounds 2b, 2c, and 2f showed that singly twisted structures are achieved without serious strain and that cyclic pi-conjugation is well-preserved, as needed for exhibiting strong diatropic ring currents.
Abstract: meso-Aryl-substituted [28]hexaphyrins(1.1.1.1.1.1) have been examined by 1H, 13C, and 19F NMR spectroscopies, UV−vis absorption spectroscopy, magnetic circular dichroism spectroscopy, and single-crystal X-ray diffraction analysis. All of these data consistently indicate that [28]hexaphyrins(1.1.1.1.1.1) in solution at 25 °C exist largely as an equilibrium among several rapidly interconverting twisted Mobius conformations with distinct aromaticities, with a small contribution from a planar rectangular conformation with antiaromatic character at slightly higher energy. In the solid state, [28]hexaphyrins(1.1.1.1.1.1) take either planar or Mobius-twisted conformations, depending upon the meso-aryl substituents and crystallization conditions, indicating a small energy difference between the two conformers. Importantly, when the temperature is decreased to −100 °C in THF, these rapid interconversions among Mobius conformations are frozen, allowing the detection of a single [28]hexaphyrin(1.1.1.1.1.1) species h...

200 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023303
2022618
2021217
2020219
2019228
2018268