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O B Ptitsyn

Publications and source records attributed to O B Ptitsyn.

117 records · Page 7Linked to original sources
PubMedDate not supplied

[Protein globule without the unique three-dimensional structure: experimental data for alpha-lactalbumins and general model].

It has been shown that bovine and human alpha-lactalbumins under the influence of acidic pH, high temperatures or low guanidine hydrochloride concentrations are transferred into a state which is quite distinct both from the native and the completely denatured (unfolded) ones. Human alpha-lactalbumin can be transferred into this intermediate state also by removal of the bound to it Ca2+ ion. On the basis of the obtained physical characteristics of this state a model of the "intermediate" state is suggested in which a protein globule is compact, has a secondary structure, but does not possess a unique three-dimensional structure. Phase diagrams of the protein molecule states (native, intermediate and unfolded) are presented and discussed and the role of the intermediate state in protein folding is considered.

Animals↗
PubMedDate not supplied

[Compact structure of random copolymers of hydrophobic and hydrophilic amino acid residues].

Studies are made of the pH-induced intramolecular structuring of such random copolymers as glutamic acid with leucine. It is shown that these copolymers, consisting of hydrophobic and hydrophilic residues, contain large amounts of fractions capable of acquiring non-aggregating compact structures in aqueous medium. These fractions have an approximately similar amino acid composition which does not almost depend on the composition of the initial copolymers. A decrease in the degree of ionization of side groups of glutamic acid promotes a formation of helical regions in the molecules of these fractions. At a further deionization, the helical regions collapse into compact structures stabilized by hydrophobic interactions of side groups of leucine. The compactness of the obtained structures is close to that of protein globules.

Fluorescence Polarization↗
PubMedDate not supplied

[Determination of the secondary structure of proteins from their circular dichroism spectra. I. Protein reference spectra for alpha-, beta- and irregular structures].

It is shown that to obtain the protein-derived basic CD spectra for alpha-helical, beta-structural and irregular regions it is necessary to use a common criterion for isolation of secondary structures for all the reference proteins. Using the "rigid" criterion proposed by Finkelstein, Ptitsyn, Kozytsyn and the "mild" one (as proposed by Levitt and Greer) isolation of the alpha- and beta-structural regions for 5 reference proteins (myoglobin, lysozyme, ribonuclease A, papain, lactate dehydrogenase) has been carried out. Using the f alpha, f beta and f irregular thus obtained and the experimental CD spectra of these proteins, the basic CD spectra for alpha-helical, beta-structural and irregular regions in the proteins have been calculated. It is shown that the use of criterions common for all the proteins leads to good agreement between the calculated basic CD spectra for alpha-helical, beta-structural and irregular forms and the CD spectra of polylysine in the corresponding conformations. The secondary structure of the proteins studied has been analysed using the new protein-derived basic spectra and fairly good quantitative agreement with the X-ray data was achieved.

Animals↗
PubMedDate not supplied

[Molten globule unfolding by strong denaturing agents occurs by the "all or nothing" principle].

The equilibrium Gu-HCl-induced denaturation of bovine carbonic anhydrase B and beta-lactamase from Staphylococcus aureus was studied at 4 degrees C by the multiparametric approach. With the use of fast protein size-exclusion chromatography (FPLC) it has been shown that in the region of the molten globule-random coil transition the distribution function of the protein molecules on size is bimodal, i.e. the protein molecules (which are already denatured) can only in one of two conformational states. Consequently the unfolding of the molten globule can be of "all-or-none" character. This means that a protein molecule can be at least in three discrete states: the native, the molten globule and unfolded.

Animals↗
PubMedDate not supplied

[The state of unfolded globules of protein molecules is more quickly becoming a rule, rather than an exception].

A review of experimental data concerning physical properties of globular protein at mild denatured conditions shows that at the present time about 20th proteins were obtained in the "molten globule" state at mild denatured conditions (acid or basic pH, high temperature or moderate concentrations of guanidine hydrochloride or urea). This state is nearly as compact as the native state and has a well pronounced secondary structure but has no rigid tertiary structure. A possible role of the molten globule state in the processes of formation and of degradation of globular proteins are discussed.

Hot Temperature↗
PubMedDate not supplied

[Effect of a biologically active interferon fragment on the structure of the synthetic protein carrier].

A biologically active de novo protein albeferon was studied by physical techniques including CD spectroscopy in far and near ultraviolet regions and microcalorimetry. Albeferon was obtained by grafting an active octapeptide interferon fragment into a de novo protein albebetin used as a carrier. It was shown that attachment of the octapeptide into its molecule did not weaken albebetin but even slightly improved its structure and stability. The obtained results can be used for de novo protein design and improvement.

Humans↗