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O B Ptitsyn

Publications and source records attributed to O B Ptitsyn.

At least 109 records · Page 6Linked to original sources
PubMedDate not supplied

[Intramolecular mobility of a protein in a "molten globule" state. A study of carbonic anhydrase by 1H-NMR].

Spin-lattice (T1) and spin-spin (T2) relaxation times for protons of methyl and aromatic side groups of carbonic anhydrase B have been measured in three states: native (pH 7.2), molten globule (pH 3.3) and completely unfolded (pH 3.3, in the presence of 8 M urea). The changes of T1 and T2 were treated based on the assumption of two types of molecular motions: (1) isotropic "slow" motions with times approximately greater than 10(-8) s (including the rotation of a molecule as a whole) and (2) anisotropic "fast" motions with times approximately less than 10(-10) s. Experimental data show an essential increase of the scale of intramolecular mobility for the majority of side groups upon transition of the protein from the native to the molten globule state.

Carbonic Anhydrases↗
PubMedDate not supplied

[Kinetics of the renaturation of bovine alpha-lactalbumin].

Multiparametric kinetic study of bovine alpha-lactalbumin renaturation from the unfolded state has shown the existence of an intermediate which is formed within 10(-2) s with properties close to those of the molten globule. Apart from the fast kinetic phase which results in the intermediate, two slower phases were found with intrinsic times approximately 1 s and approximately 10 s. The slowest one is apparently due to proline isomerization.

Animals↗
PubMedDate not supplied

[Predicting the three-dimensional structure of alpha- and beta-interferons].

Secondary structures of leukocyte alpha 1- and alpha 2-interferons and of fibroblast beta-interferon are calculated using the molecular theory of protein secondary structures. The common secondary structure calculated for alpha- and beta-interferons is used to predict the three-dimensional structures of fragments 1-110 and 111-166 of the chains (which are supposed to be quasi-independent domains). The predicted structure of the active domain I (1-110) is an "up-and-down" tetrahelical complex (in which the second helix is shorter than the others and can be missed in alpha 1-interferon) similar to the mirror-image of myohaemoerythrin. The predicted structure of domain II (111-166) is either a three-stranded beta-sheet screened from one side by two alpha-helices or a three-helical complex (similar to that in the N-domain of papain), the first structure being better consistent with the circular dichroism data of alpha-interferon and its C-end fragment.

Animals↗
PubMedDate not supplied

[Determination of the secondary structure of proteins from their circular dichroism spectra. II. Estimation of the contribution of beta-pleated sheets].

Protein-derived basic CD spectra for alpha-helical, beta-structural, beta-bends and irregular regions of the proteins have been determined from the experimental CD spectra of five reference proteins (myoglobin, lysozyme, ribonuclease A, papain, lactate dehydrogenase) with the knowledge of the fractions of the residues in the corresponding conformation. The alpha-helical and beta-structural regions of the reference proteins have been isolated from the X-ray data using the common "rigid" criteria for all the proteins, as proposed by Finkelstein and Ptitsyn. The residues in the beta-bend have been isolated using the data of Chou and Fasman and also three assumptions formulated in the present paper. The basic CD spectra thus obtained have been used for the analysis of secondary structures of 10 proteins (5 reference and 5 additional ones). There is a good agreement between the results of the X-ray data and those obtained from the CD spectra.

Circular Dichroism↗
PubMedDate not supplied

[Determination of protein secondary structure from circular dichroism spectra. III. Protein-derived base spectra of circular dichroism for antiparallel and parallel beta-structures].

Protein-derived basic CD spectra for alpha-helix, antiparallel and parallel beta-structures, beta-bends and irregular form of proteins have been determined from the experimental CD spectra of six (myoglobin, lysozyme, ribonuclease A, papain, lactate dehydrogenase, subtilisin BPN') or seven (glyceraldehyde-3-phosphate dehydrogenase added) reference proteins and the analysis of the X-ray data. The secondary structures of thirteen proteins (seven reference and six additional ones) have been analysed using the basic CD spectra thus obtained. The data obtained have been compared with the results of the X-ray data analysis. It is shown that the accuracy of determination of the beta-structure and beta-bends contents using our basic CD spectra is about 2-3 times better than using the basic spectra reported by Chang et al. (Analyt. Biochem. 91, 13-31, 1978).

Circular Dichroism↗
PubMedDate not supplied

[Fluctuating state of the protein globule].

It has been shown that bovine and human alpha-lactalbumins and carbonic anhydrase B can be transformed under different influence into a peculiar state possessing physical characteristics intermediate between those for the native and unfolded states. In this state a protein molecule is compact and has the secondary structure similar to that of the native molecule, but does not melt cooperatively at heating, has an anomalously fast H-D exchange and a more or less symmetrical average environment of aromatic and other side groups. A model of this "intermediate" state of protein molecule is proposed, according to which the intermediate state differs from the native one mainly by the substantial increase of protein structure fluctuations and the sharp decrease of van der Waals and other specific interactions. It has been shown that the transition from the native state to this intermediate state is the phase transition of the first order. The role of the intermediate state in protein folding is discussed.

Animals↗
PubMedDate not supplied

[Protein as an edited random copolymer].

It is widely believed that the unique primary structure of a given protein is quite necessary for its folding into a certain three-dimensional structure as well as for its functioning and is a result of a directed selection in the course of biological evolution. The present paper provides arguments in favour of an alternative point of view according to which typical three-dimensional structures of globular proteins are characteristic even for random sequences of amino acid residues. Therefore it may be possible that primary structures of proteins are mainly examples of random amino acid sequences slightly edited in the course of biological evolution to impart them some additional (functional) meaning.

Amino Acid Sequence↗