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At least 343 records · Page 19Linked to original sources
PubMed1985

[Estimation of the frequency of amino acid substitutions causing instability of the spatial structure in an overall mutation spectrum of alpha- and beta-subunits of human hemoglobin].

The influence of single amino acid substitutions on the stability of alpha- and beta-chains of human hemoglobin was investigated by the computer method. The method was based on characteristics of protein tertiary structure and physico-chemical properties of amino acids. Frequencies of unstable mutations in the total mutational spectra of alpha- and beta-subunits of human hemoglobin were analysed: instability was produced by 26% of mutations in the alpha-subunit and by 32% in the beta-subunit. These results support the idea that certain limitations exist for stability changes produced by amino acid substitutions.

Amino Acid Sequence↗
PubMedDate not supplied

[Human visual evoked potentials to spatially structured stimuli in normal subjects and early object vision deprivation].

For the analysis of plastic rearrangements in the visual system under the influence of different conditions of adaptation and early deprivation of objective vision, VEPs to checkerboard patterns with various check sizes were studied in subjects with normal vision and with amblyopia resulting from a congenital cataract. Sensitivity of P 180-230 component to the check sizes was revealed as well as a shift of its optimum toward bigger sizes following a transition from the light to the dark adaptation. In amblyopic subjects, in response to the checkerboard patterns the amplitude of P 80-120 component significantly increased, whereas that of P 180-230 decreased, with a shift of its optimum toward bigger check sizes. Informational significance of VEP waves and possible mechanisms of amblyopia are discussed.

Adolescent↗
PubMed1982

Remarks on the spatial structure of the external segment of glycophorin A.

A model of the possible structure of the N-terminal part of glycophorin A is suggested. According to this model, in isotonic salt solutions of physiologic pH the peptide chain of the extracellular segment of glycophorin A is arranged parallel to the membrane with its carbohydrate side chains orientated perpendicularly to the lipid bilayer. Decreases of the pH or of the ionic strength result in a structural remodeling of this segment, there is at the very least a partial detachment of the glycosylated peptide backbone from the membrane's lipid layer.

Chemical Phenomena↗
PubMedDate not supplied

[Primary and spatial structure of tRNA].

The recent achievements in studying of structure of tRNA are considered in the present paper. A brief analysis of the new methods for sequencing tRNA was carried out. Due to the development of these methods about 300 tRNA primary structures have been determined. Comparison of the primary tRNA structures gives us the possibility to divide them into seven classes: prokaryotic initiator tRNAs and eukaryotic initiator tRNAs; prokaryotic elongator tRNAs and eukaryotic elongator tRNAs; archaebacterial tRNAs; and mitochondrial tRNAs of lower and higher eukaryotes. Structural properties of the tRNAs of each of these classes are discussed. The second part of the paper is devoted to the three-dimensional structure of tRNA. Recent data in this field obtained by X-ray crystallographic technique as well as by high-resolution NMR and chemical modification methods are reviewed.

Animals↗
PubMedDate not supplied

[Hydratation of the rubredoxin polypeptide chain from data on the spatial structure].

The hydration water distribution around the main chain protein rubredoxin has been analysed using the crystal data at high resolution obtained earlier. The analysis was based on the consideration of all nearest neighbour atoms around the N and O atoms of peptide groups. The atoms which can form hydrogen binds were the subject of final analysis. The nitrogen atom of a peptide NH group has only one vacancy for neighbours. The oxygen atom of a peptide CO group has one, two or more neighbours, some of them are oxygen-water atoms. About 27% of NH and 53% of CO peptide groups are hydrated, that corresponds to 0.12 H2O per gram of protein. A detailed analysis shows that NH and CO groups of the main chain are hydrated according to the principle of maximum possible in situ saturation of hydrogen bonds. Thus the peptide groups incorporated in the peptide hydrogen bond network were not hydrated as a rule. Consequently, for rubredoxin a pleated sheet region, some regions for the large and small main chain loops, and Fe-containing pocket are not hydrated. A method for evaluation of the main chain hydration is proposed when the coordinates of protein atoms are available.

Crystallization↗
PubMedDate not supplied

[Spatial structure of DNA complex with the oligopeptide dansyl hydrazide trivaline].

The structure of complexes between double-stranded DNA and oligopeptide dansyl hydrazide trivaline was studied by linear dichroism, electron microscopy and hydrodynamical methods. The results show that the binding of the oligopeptide to DNA is a cooperative process that leads to the formation of particles significantly differing in the structure from free DNA. The linear dichroism studies were carried out in a wide range of flow-speed gradients. From the theoretical analysis of these data a conclusion can be drawn that the DNA-oligopeptide complexes possesses a higher rigidity as compared with that of free DNA. The hydrodynamical behaviour of these particles is consistent with the rigid rod-like structure of the particles with a long axis nearly parallel to the DNA helix axis in the complexes. The sedimentation patterns of the complexes suggest the existence of the fast and slow sedimenting species. The sedimentation coefficient measured for a fast sedimenting species is about 3 times higher than that of free DNA. The linear dichroism spectra obtained for the floworiented DNA-oligopeptide complexes correlate with the existence of a superhelical organization of DNA in the complex. This offers a possibility for the determining of the angle of the DNA local axis inclination with respect to the superhelix axis. On electron micrographs the DNA-oligopeptide complexes look like rod-shaped structures with the thickness of about 180 A and 80 A on the rotatory-shadowed preparations and on the uranylacetate stained preparations, respectively. The rod-shaped structures are formed by two interwound DNA molecules. The superhelix has a pitch of about 150 A with an angle of twist inclination of about 40 degrees. These values are in good agreement with the optical anisotropic data. It is suggested that the complex structure is stabilized by periodically spaced hydrophobic contacts between the dimeric oligopeptide species bound to the DNA molecules.

DNA↗
PubMedDate not supplied

[Water distribution around a protein molecule from data on spatial structure].

Water distribution was calculated using the structure data of protein rubredoxin (K. Watenlaugh et al. J. Mol. Biol., 138, 615, 1980). By this method the hydration surrounding of macromolecules was localized in the spheres of the 3,2 A radius with the error 8%. A detailed analysis of the data on water localization in the protein crystal shows that hydration water distribution consists of the associates of water molecules and does not form the "hydration shell".

Biopolymers↗
PubMed1983

[Spatial structure of a vasoactive peptide--a fibrin fragment].

Empirical energy calculations were used to determine all low-energy conformations of vasoactive pentapeptide Ala-Arg-Pro-Ala-Lys, thereby three most stable conformations were distinguished. Biological testing of conformationally restricted analogs allowed to delineate the most probable "biologically active" conformation of the molecule.

Fibrin Fibrinogen Degradation Products↗
PubMedDate not supplied

[A priori calculations of spatial structure of neurotoxin. Fragment Leu1-Cys23].

Conformational properties of a linear and cyclic Leu1-Cys23 neurotoxine fragment have been investigated. Starting from a linear array, the most favourable cyclic form with the Cys3-Cys23 disulfide bond is shown to arise from one of the low-energy extended structures. The formation of the disulfide bond does not interfere with stabilising contacts: the proximation of S-atoms to the valence distance can be effected by small changes of the labile fragment geometry. The results obtained are indicative of the strictly predetermined mechanism of the protein folding into the native conformation with the proximal Cys residues, forming a disulfide bridge. The calculated low-energy Leu1-Cys23 neurotoxine form coincides with the X-ray structure of the corresponding fragment of erabutoxine b. For the neurotoxine II homologies, neurotoxines alpha, D, 4, CM-14 and beta, optimal orientations of side chains are determined. The amino acid changes in the 1--23 fragment are shown not to disturb the backbone form established for the neurotoxine II, and thus not to change the geometry necessary for the formation of the Cys3-Cys23 bridge.

Amino Acid Sequence↗