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Biomedical subjects

Iu A Lazarev

Publications and source records attributed to Iu A Lazarev.

At least 19 recordsLinked to original sources
PubMed1982

[Structural differences in the collagens of Rana frog species with dissimilar temperature ecology. The contribution of carbohydrate components to collagen molecular thermostability].

Skin procollagens in two species groups of frogs of the genus Rana - brown frogs (4 species) and green frogs (3 species) distributed in European and Asiatic parts of the USSR have been compared. A geographic intraspecific variation in collagen characteristics (two geographic populations of the pond frog Rana nigromaculata) is revealed. Intergroup differences in the thermal denaturation of collagens established by means of methods of circular dichroism and microcalorimetry are significant. Such differences within both the groups are not so visible. With the species studied, carbohydrate components contents in procollagen vary. Interspecific differences in the procollagen thermostability correlate with the thermal ecology of frogs and seem to be associated with the availability of carbohydrates.

Animals↗
PubMedDate not supplied

[IR-spectroscopic study of cytochrome C-phospholipid lipoprotein and proteolipid model membranes].

It is shown by the methods of IR-spectroscopy and peptide hydrogen-deuterium exchange that a) considerable changes in the protein spectra occur (beta-conformation in the protein structure appears) during the interaction in water of cytochrome c molecules with lipid membranes containing negatively charged polar groups; b) further significant changes of the protein spectrum occur under the action of 1% OsO4 and heating up to n plus 95 degrees C; c) the conformational state of the pure protein in water; after the treatments of the proteolipid memebranes with 1% OsO4 and heating up to n degrees C no significant changes of protein spectrum occur, that may suggest hydrophobic interactions between the protein and lipids; d) the treatment of both pure cytichrome c and the model membranes with 1% glutaraldehyde, 30, 60% ethanol and acetone solutions in water does not reveal substantial changes in IR-spectra of the protein moiety.

Cytochrome c Group↗
PubMedDate not supplied

[Formation of a hydrate structure in the collagen-like triple helix upon hydration].

By the IR-spectroscopy method successive stages of hydrate envelope formation of the collagen-like triple-helical structure of the monodisperse synthetic polytripeptide Z-(Gly-Pro-Pro)8-OMe were studied. The multistep-type process is followed by isomorphic transitions of the triple-helical structure and by the increasing of hydrogen bond strength.

Collagen↗
PubMedDate not supplied

[Picosecond flash photolysis of Halobacterium halobium bacteriorhodopsin at room and low temperatures].

The primary stage of photoexcitation of bacteriorhodopsin from Halobacterium halobium upon the action of ultrashort (tau equal to 25 ps) laser impulse of 530 nm wavelength and of energy 2.5.10(-3) J has been studied. The primary photoproduct with a maximum of 630 nm is shown to occur in the differential spectrum in a time less than 25 ps both at room temperature (+20 degrees C) and at a low temperature (-150 degrees C).

Bacteriorhodopsins↗
PubMedDate not supplied

[Investigation of the effects of dehydration on bacterial rhodopsin by laser resonance Raman spectroscopy].

Using laser resonance Raman spectroscopy the influence of water on the structure of the chromophore centre in bacteriorhodopsin from Halobacterium halobium has been studied. The absorption band has been found to shift from 568 nm to 506 nm due to local protein changes in the chromophore centre near Schiff base bounding retinal with the lysine residue. These changes are not accompanied by the Schiff base deprotonation. Dehydration decreases essentially the reaction rate of the cis in equilibrium trans isomerization processes. In the dry state the potential barriers of the cis in equilibrium trans transition reaction turns out to be higher than that of the reverse reaction. As a result the equilibrium shifts to the cis-retinal form. Comparison of the Raman spectra of the M412 intermediate in wet and dry states of purple membranes leads to the conclusion that in water suspensions of purple membranes the chromophore state of the M412 intermediate is closer to cis- than to trans-retinal.

Bacteriorhodopsins↗
PubMedDate not supplied

[Aggregation of poly-L-proline in aqueous solution].

Infrared spectra were measured for both aqueous (D2O) solution and the solid state of form II poly-L-proline in the amide I region as a function of the temperature. The temperature range includes the region where a precipitation is known to occur. From the analysis of spectra of hydrated films and aqueous solutions at different temperatures one can see that there are some peptide C = O-groups which are bounded with water. From this study it has been concluded that poly-L-proline exists in aggregate form even at temperatures lower that required for precipitation. It is supposed that poly-L-proline forms the aggregates including at least 40--50 polypeptide chains with hexagonal packing. At heating crystallisation of such aggregates occurred and it causes precipitation of poly-L-proline II.

Kinetics↗
PubMedDate not supplied

[Modification of the retina photoreceptor membranes and temperature stability of rhodopsin].

The effect of modification of photoreceptor membranes of the bovine retina on the termodynamical parameters that characterize heat denaturation of rodopsin was studied. The highest increase of the rate constant and the corresponding maximal drop of the free energy change of heat denaturation of the pigment were obtained by using 7 M urea or 25% Triton X-100 in the presence of 5.10(-4) M EDTA. After chipping off one third of the protein from the rodopsin molecule by papain treatment a significant decrease of the slope of the Arrenius curve and a maximal decrease of entropy change compared to the parameters known for heat denaturation of the pigment in native photoreceptor membranes were found. Modification of the lipid components of the photoreceptor membranes (treatment with Triton X-100 and phospholipase C) reduced the thermostability of rodopsin. Maximal changes were obtained at Triton X-100 concentrations 0.1--1%, further concentration increas (1--25%) did not lead to significant changes. Phospholipase C treatment resulted in a decrease of free energy change and an increase of entropy change without affecting entalpy changes, accompaning the heat denaturation of rodopsin. Bivalent cations (Ca2+, Mg2+) increased the termostability of rodopsin both in photoreceptor membranes and in solutions to 25% Triton X-100.

Animals↗