Conformational flexibility of the protein insertase BamA in the native asymmetric bilayer elucidated with ESR spectroscopy

Compounds of the type of 2-(4'-nitrobenzoyl)methylene-3-ethylbenzothiazoline (I) and 2-bis-(p-nitrobenzoyl)methylene-3-ethylbenzothiazoline (II) were studied polarographically and by ESR spectroscopy to obtain informations about their electrochemical and follow-up reactions and their conformation. Whereas with compounds of the type I the conjugation in their molecules is preserved, with type II the coplanarity of the molecules is disturbed, which is manifested in the values of the splitting constants of the ESR spectra and a slow electron transfer between both nitrophenyl substituents. These conclusions are supported by NMR spectroscopic studies.

Download Full-text

The model rotator phase

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19880889 ◽

1988 ◽

Vol 53 (5) ◽

pp. 889-902

Author(s):

Josef Šebek

Keyword(s):

High Temperature ◽

Partition Function ◽

Conformational Flexibility ◽

Small Probability ◽

Crystalline Phases ◽

Rotator Phase

It is shown that the formation of the so-called rotator phase of alkanes (one of the high temperature crystalline phases) might be connected with a partial increase of the conformational flexibility of chains. The conformations with higher number of kinks per chain, which have been neglected till now, are shown to contribute effectively to the conformational partition function. Small probability of these states given by the Boltzmann exponent is compensated by a large number of ways in which they can be distributed along the chain. The deduced features of the rotator phase seem to be in agreement with the experimentally observed properties.

Download Full-text

Association of radical anion with alkali cations. IV. ESR study of the 4-nitrobenzophenone radical anion

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19800369 ◽

1980 ◽

Vol 45 (2) ◽

pp. 369-375 ◽

Cited By ~ 2

Author(s):

Stanislav Miertuš ◽

Ondrej Kyseľ

Keyword(s):

Hyperfine Splitting ◽

Radical Anion ◽

Esr Spectroscopy ◽

Supporting Electrolyte ◽

Esr Spectra ◽

Proton Donor ◽

Alkali Cations

The 4-nitrobenzophenone radical anion prepared by electrolysis was studied by ESR spectroscopy. On the basis of the interpretation of ESR spectra, the conformation of this system was estimated. The effect of the concentration of supporting electrolyte and of the presence of a proton-donor agent (C2H5OH) was examined. It is assumed that changes in hyperfine splitting constants are caused by association.

Download Full-text

Stability of radical anions derived from substituted 5-nitrofurans investigated by ESR spectroscopy

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19851594 ◽

1985 ◽

Vol 50 (7) ◽

pp. 1594-1601 ◽

Cited By ~ 5

Author(s):

Jiří Klíma ◽

Larisa Baumane ◽

Janis Stradinš ◽

Jiří Volke ◽

Romualds Gavars

Keyword(s):

Radical Anion ◽

High Stability ◽

Esr Spectroscopy ◽

Reaction Path ◽

Order Reaction ◽

Second Order ◽

Radical Anions ◽

Second Order Reaction ◽

Unpaired Electron Density ◽

The Stability

It has been found that the decay in dimethylformamide and dimethylformamide-water mixtures of radical anions in five of the investigated 5-nitrofurans is governed by a second-order reaction. Only the decay of the radical anion generated from 5-nitro-2-furfural III may be described by an equation including parallel first- and second-order reactions; this behaviour is evidently caused by the relatively high stability of the corresponding dianion, this being an intermediate in the reaction path. The presence of a larger conjugated system in the substituent in position 2 results in a decrease of the unpaired electron density in the nitro group and, consequently, an increase in the stability of the corresponding radical anions.

Download Full-text

The effect of cation concentration on the nitrogen splitting constant of nitroxide free radicals

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19902377 ◽

1990 ◽

Vol 55 (10) ◽

pp. 2377-2380

Author(s):

Hamza A. Hussain

Keyword(s):

Hydrogen Peroxide ◽

Hydrogen Bonding ◽

Free Radicals ◽

Esr Spectroscopy ◽

The Other ◽

Tetraethylammonium Bromide ◽

Splitting Constant ◽

The One ◽

Positively Charged ◽

Two Equilibria

Nitroxide free radicals prepared from diethylamine, piperidine and pyrrolidine by oxidation with hydrogen peroxide were studied by ESR spectroscopy. The changes in the 14N splitting constant (aN) caused by the addition of KBr or tetraethylammonium bromide were measured in dependence on the concentration of the ions. For diethylamine nitroxide and piperidine nitroxide, the results are discussed in terms of two equilibria: the one, involving the anion, is associated with a gain or loss of hydrogen bonds to the nitroxide oxygen atom, the other is associated with the formation of solvent shared units involving the cation, which results in changes in the hydrogen bonding strenght. The large increase in the aN value in the case of pyrrolidine nitroxide is explained in terms of an interaction from one side of the positively charged N atom; the increase in aN in the case of diethylamine and piperidine nitroxides is explained in terms of interactions with both sides of the positively charged N atom.

Download Full-text