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A V Starostin

Publications and source records attributed to A V Starostin.

8 recordsLinked to original sources
PubMed1999

An anion-selective analogue of the channel-forming peptide alamethicin.

The peptide alamethicin self-assembles to form helix bundle ion channels in membranes. Previous macroscopic measurements have shown that these channels are mildly cation-selective. Models indicate that a source of cation selectivity is a zone of partial negative charge toward the C-terminal end of the peptide. We synthesized an alamethicin derivative with a lysine in this zone (replacing the glutamine at position 18 in the sequence). Microscopic (single-channel) measurements demonstrate that dimeric alamethicin-lysine18 (alm-K18) forms mildly anion-selective channels under conditions where channels formed by the parent peptide are cation-selective. Long-range electrostatic interactions can explain the inversion of ion selectivity and the conductance properties of alamethicin channels.

Alamethicin↗
PubMed1999

Engineering charge selectivity in alamethicin channels.

The peptide alamethicin provides a system for engineering ion channel charge selectivity. To define alamethicin charge selectivity experimentally, we measured single-channel current-voltage relationships in KCl gradients using covalently linked peptide dimers. Two factors were found to contribute to the charge selectivity of these channels: (i) the ionic strength of the surrounding solutions; and (ii) the distribution of fixed charge on the peptide. Native alamethicin channels exhibited either cation selectivity or anion selectivity depending on which end of the channel was at the low salt side of the membrane. When the glutamine residue at position 18 in the sequence was replaced with a lysine residue, an anion-selective channel was obtained regardless of which end of the channel was at the low salt side of the membrane.

Alamethicin↗
PubMed1997

Voltage-dependent behavior of a "ball-and-chain" gramicidin channel.

The channel-forming properties of two analogs of gramicidin, gramicidin-ethylenediamine (gram-EDA), and gramicidin-N,N-dimethylethylenediamine (gram-DMEDA) were studied in planar lipid bilayers, using protons as the permeant ion. These peptides have positively charged amino groups tethered to their C-terminal ends via a linker containing a carbamate group. Gram-DMEDA has two extra methyl groups attached to the terminal amino group, making it a bulkier derivative. The carbamate groups undergo thermal cis-trans isomerization on the 10-100-ms time scale. The conductance behavior of gram-EDA is found to be markedly voltage dependent, whereas the behavior of gram-DMEDA is not. In addition, voltage affects the cis-trans ratios of the carbamate groups of gram-EDA, but not those of gram-DMEDA. A model is proposed to account for these observations, in which voltage can promote the binding of the terminal amino group of gram-EDA to the pore in a "ball-and-chain" fashion. The bulkiness of the gram-DMEDA derivative prevents this binding.

Amino Acid Sequence↗
PubMed1997

[Hemocarboperfusion in the treatment of patients with an opiate abstinence syndrome].

The authors analyze of the results of applying hemocarboperfusion in treatment of opiate addiction. All the patients were treated in the Belorussian center of sorption methods of detoxication and plasmapheresis. It is shown that 4-5 procedures of hemocarboperfusion in combination with infusion and drug therapy allow to correct of withdrawal mental and somatic disorders.

Adolescent↗
PubMedDate not supplied

[Rhodopsin photo-oxidation: oxygen consumption and spectrum of activity].

The coincidence of action spectrum of SH-groups and lipid oxidation is shown in the photoreceptor photodamaging process. Dose dependence of the process is measured in the maximum of photooxidation (380 nm). Dose of 0.1 J/cm2 is the threshold of photodamaging of photoreceptor membrane. Oxygen consumption in photooxidation of rhodopsin SH-groups and lipids are determined.

Animals↗
PubMedDate not supplied

[Retinal-sensitized photo-oxidation of rhodopsin].

Kinetics of retinal photosensitized initiation of radicals of sulfhydryl groups of cysteine and rhodopsin is investigated by spin trapping. Photooxidation of both systems is the result of free radical mechanism. Photooxidation of SH-groups proceeds both with singlet oxygen participation and by direct interaction of photosensitizer with the substrate. The rate constants of these reactions are measured. The rate constant with oxygen participation (K0 = 1.1 X 10(9) M-1 S-1) is higher than the one without oxygen (K = 2.5 X 10(8) M-1 S-1) correspondingly. The lifetime of retinal triplet state in photoreceptor membrane is tau = 4 X 10(-6) s.

Animals↗
PubMedDate not supplied

[Mechanism of glutathione oxidation by photosensitized retinal].

Sulphur radicals appearing in the retinal photosensitized glutathione oxidation have been recorded by spin trapping. There is no reaction in the absence of oxygen. That is why the single oxygen is supposed to take part in the reaction (IId type photosensitized reaction).

Electron Spin Resonance Spectroscopy↗