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Biomedical subjects

M Kumbar

Publications and source records attributed to M Kumbar.

16 recordsLinked to original sources
PubMed1977

An interpretation of small-angle light-scattering patterns of human cornea.

Small-angle light-scattering patterns of human cornea in I. and I modes were compared to theoretical scattering patterns generated in the computer on the basis of a cornea model. This model is a nonrandom assembly of optically anistropic rods. The best match of theoretical and experimental patterns yielded the following parameters describing the ultrastructure of human cornea: length of the rod (fiber)=12 mu; angle between optic and geometric axis of the rod=60 degrees; most probable orientation of the rod=150 degree; the width of the distribution function of rod orientation (omega0)=2.5; intrinsic birefringence of the rod=7 X 10(-6); form birefringence=1.3 X 10(-5).

Birefringence↗
PubMed1976

Quantum chemical studies on drug action V: Involvement of structure-activity, quantum chemical, and hydrophobicity factors in thrombocyte uptake of 5-hydroxytryptamine.

Inhibition of the uptake of 5-hydroxytryptamine (serotonin) in the thrombocyte by various tryptamine derivatives was investigated. The activity depended on the nature and position of the substituent. This activity was correlated with the total orbital energy and hydrophobicity factors. Other quantum parameters, such as the highest occupied molecular orbital energy and the lowest empty molecular orbital energy, failed to correlate. The possible involvement of two receptor sites that are sterically and electronically dissimilar is postulated because compounds fell into two distinct groups. The hydrophobicity factor was important in only one group of compounds, while the electronic factor was important in both.

Animals↗
PubMed1976

Investigation of the effect of the solvent medium on the conformational behavior of phenylethylamines by empirical method.

The effect of dielectric constant (solvent medium) on the conformational behavior of six phenylethylamines has been investigated using the empirical method. Various physical properties, such as rotamer population, dipolemoment, optical anisotropy, and depolarization ratios are examined. The effective intramolecular dielectric constant has been varied from 1.0 (vacuum) to 80.0 (highly polar medium). It is shown that all these properties truly depend on the magnitude of the dielectric constant (nature of the solvent medium), but the effect is more pronounced when the dielectric constant is less than about 30.0. In addition, the effect of various groups has been assessed by using the above-mentioned properties. In general, allthe six compounds studied here possess three energy minima corresponding to one trans and two gauche forms. These energy minima have shifted only once when the dielectric constant is increased from 1.0 to 5.0. Thus, it is concluded that the nature of the solvent medium is critical in assessing percent population, ionic character, and polarizability of the molecule but not in describing the energy minima.

Electrochemistry↗
PubMed1975

Preferred conformations of serotonin in relation to receptor sites.

Using an empirical method, three preferred conformations for serotonin have been predicted. These three conformations corresponding to one extended form (phi equal to 80 degrees, psi equal to 180 degrees), and two folded forms (phi equals to 280 degrees, and psi equals to 100 degrees, phi equals to 100 degrees psi equals to 290 degrees). The calculated intramolecular distances in both forms agree with those obtained by the X-ray crystallography of various indoleamines. Furthermore, the dual receptor binding activity of serotonin has been explained in terms of extended and folded conformations.

Amines↗
PubMed1975

Effect of aromatic molecules on the aggregation of C-phycocyanin. Quantum chemical calculations on phycocyanobilin and phycoerythrobilin.

The energies of the highest occupied and lowest empty molecular orbitals were calculated for the chromophore groups of the proteins phycocyanin and phycoerythrin. These tetrapyrrole groups on the algal proteins are shown to provide them with the potential of ating as efficient electron donors and acceptors. In addition, the pi electron charges and bond orders were also computed.

Chemical Phenomena↗