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Biomedical subjects

S Srinivasan

Publications and source records attributed to S Srinivasan.

At least 235 records · Page 13Linked to original sources
PubMed1989

Neonatal scurvy.

Explore the source record for details and available documents.

Ascorbic Acid↗
PubMed1987

Multistep modeling of protein structure: application towards refinement of tyr-tRNA synthetase.

The scope of multistep modeling (MSM) is expanding by adding a least-squares minimization step in the procedure to fit backbone reconstruction consistent with a set of C-alpha coordinates. The analytical solution of Phi and Psi angles, that fits a C-alpha x-ray coordinate is used for tyr-tRNA synthetase. Phi and Psi angles for the region where the above mentioned method fails, are obtained by minimizing the difference in C-alpha distances between the computed model and the crystal structure in a least-squares sense. We present a stepwise application of this part of MSM to the determination of the complete backbone geometry of the 321 N terminal residues of tyrosine tRNA synthetase to a root mean square deviation of 0.47 angstroms from the crystallographic C-alpha coordinates.

Computer Graphics↗
PubMed1987

Structural elements and organization of the ancestral translational machinery.

The molecular mechanisms underlying the primitive translational apparatus have been studied in light of present day protein biosynthesis. Using the structural information available from the contemporary system as a key to its function, both the structural necessities for an early adaptor and the multipoint recognition properties of such adaptors have been investigated. This was done by first critically examining the potential feasibility of right- and left-handed hairpin adaptor models. Second, a molecular model of the contemporary transpeptidation complex has been constructed in order to ascertain the structural requirements of the adaptor molecule needed for peptidyl transfer. Third, a model of the tRNATyr-tyrosyl tRNA synthetase complex including the positioning of the disordered region is proposed. This model is used to illustrate those required recognition properties of aminoacyl synthetase which lead to a perspective on the structure of the ancestor synthetase.

Amino Acyl-tRNA Synthetases↗
PubMed1987

Interaction scheme of the binding of acetylcholine receptor with cobratoxin and erabutoxin.

Snake toxins bind to the periphery of acetylcholine receptor which overlaps with the agonist site, thus inhibiting the ion channel opening mechanism. It has been proposed (Stroud and Finer-Moore, 1985) that the residues lying between Cys 130 and Cys 142 of the alpha-subunit of the acetylcholine receptor participate in the binding of toxins. A three-dimensional model of acetylcholine with cobratoxin and erabutoxin is built based on the interaction scheme proposed by Smart et al. (1984). The differences in the hydrogen bonding schemes between the two complexes are discussed. The results show the effect of the conservative substitution (Asp/Glu) at position 42 in the toxins on the binding interactions.

Animals↗
PubMed1986

Multistep modeling (MSM) of biomolecular structure application to the A-G mispair in the B-DNA environment.

A multistep modeling procedure has been evolved to study the structural changes introduced by lesions in DNA. We report here the change in the structure of regular B-DNA geometry due to the incorporation of Ganti-Aanti mispair in place of a regular G-C pair, preserving the helix continuity. The energetics of the structure so obtained is compared with the Ganti-Asyn configuration under similar constrained conditions. We present the methodology adopted and discuss the results.

Computer Graphics↗
PubMed1986

Multistep modeling of protein structure: application to bungarotoxin.

Modelling of bungarotoxin in atomic details is presented in this article. The model-building procedure utilizes the low-resolution crystal coordinates of the c-alpha atoms of bungarotoxin, sequence homology within the neurotoxin family, as well as high-resolution x-ray diffraction data of cobratoxin and erabutoxin. Our model-building procedure involves: (a) principles of comparative modelling, (b) embedding procedures of distance geometry, and (c) use of molecular mechanics for optimizing packing. The model is not only consistent with the c-alpha coordinates of crystal structure, but also agrees with solution conformational features of the triple-stranded beta sheet as observed by NOE measurements.

Bungarotoxins↗
PubMed1983

Pharmacokinetics of amdinocillin and pivamdinocillin in normal volunteers.

The pharmacokinetic parameters of amdinocillin and pivamdinocillin were studied in 12 normal volunteers. Plasma amdinocillin concentrations were determined by microbiologic assay and urine concentrations by high performance liquid chromatography. Pharmacokinetic parameters were calculated by a two-compartment open model for the intravenous infusion and by a one-compartment model with zero-order absorption for the oral doses. The mean peak serum level after the intravenous infusion of 500 mg was 39 micrograms/ml. At one and a half hours after the oral administration of 250 mg and 500 mg doses, mean peaks were 1.93 and 2.66 micrograms/ml respectively. Half-life was one hour for all doses. Maximal plasma concentration did not increase proportionally with dose. Bioavailability was 45 percent after the 250 mg dose and 38 percent after the 500 mg dose.

Administration, Oral↗
PubMed1982

Alterations of the conformation of the RNAs of alfalfa mosaic virus upon binding of a few coat protein molecules.

Structural changes in the single-stranded genome RNAs (RNAs 1, 2 and 3) and the subgenomic coat protein messenger (RNA 4) of alfalfa mosaic virus upon addition of a few coat protein molecules of the virus were investigated by measuring the fluorescent intensity of bound ethidium bromide and by circular dichroism. No effect could be observed in the case of the genome RNAs. However, in RNA 4, which is of much less complexity than the genome RNAs, a reduction of the ethidium bromide binding by 30% was found, whereas the positive molar ellipticity at 265 nm was reduced by 9% upon binding of the coat protein. Both changes point to a reduction of the ordered structure of the RNA. Since the protein is known to bind first at the 3'-terminus of RNA 4 and probably also of the genome RNAs, the conformational changes observed could be those thought to be necessary for replicase recognition in this positive-stranded RNa virus which needs the coat protein for starting an infection cycle.

Circular Dichroism↗