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Biomedical subjects

S Rajendran

Publications and source records attributed to S Rajendran.

54 records · Page 3Linked to original sources
PubMed1993

Interaction of myo-inositol hexaphosphate (MIHP) with beta-globulin from Sesamum indicum L. Kinetics and thermodynamics.

beta-Globulin, the low molecular weight protein fraction from Sesamum indicum L., interacts with myo-inositol hexaphosphate (MIHP) maximally at pH 3.0, with concomitant precipitation up to 85 +/- 2% at an MIHP concentration of 8 x 10(-4) M. The kinetics of interaction as followed by stopped-flow spectrophotometry suggested the reaction to be of pseudo first-order, having an initial fast step followed by a relatively slow step of rate constants 1.9 x 10(-2) s-1 and 1.2 x 10(-3) s-1, respectively at 1 x 10(-4) M MIHP concentration. The analysis of the complex indicated the presence of polymer as seen in sedimentation velocity experiment. This was accompanied by conformational change of a three-fold decrease in beta-structure and also an increase in fluorescence emission intensity accompanied with a red shift from 330 to 334 nm. Stoichiometric analysis of MIHP binding suggested four independent binding sites for MIHP, with a free energy change, delta G zero = 5.1 kcal mol-1 resulting from a binding constant of 3.6 x 10(3) M-1.

Beta-Globulins↗
PubMed1993

Structural stability of beta-globulin, the low molecular weight protein fraction from sesame seed (Sesamum indicum L.) in alkaline solution.

Beta-globulin, a single polypeptide chain of molecular weight 15,000 +/- 1,000, undergoes denaturation in alkaline pH (7.0-13.0), thereby affecting the hydrodynamic properties of the protein, viz. a decrease in sedimentation coefficient from a value of 2.0s to 1.4s at pH 11.3, an increase in reduced viscosity from 0.042 dl/g to 0.158 dl/g at pH 12.6 and a decrease in partial specific volume resulting in a volume change of 6.3 +/- 1.0 ml/mole residue at pH 11.7. The perturbation of tryptophanyl residues and ionization of tyrosyl residues are preceded by alteration in conformational status of the protein. The fluorescence emission measurements indicate initial unfolding of the protein molecule which exposes the tryptophan and tyrosyl residues to the solvent. The tyrosyl phenolic group ionization is anomalous having a pKint value of 11.2. The reduced viscosity value reaches a plateau region at pH 12.5.

Hydrogen-Ion Concentration↗
PubMed1992

Association of proteins in acidic solutions--a case study with beta-globulin.

The investigation of the effect of acid pH on the structure of beta-globulin indicated several transitions as a function of pH. Upon reducing the pH from 7.0, the beta-globulin molecule underwent an expansion due to hydration up to pH 5.0, and a further increase in H+ concentration resulted in unfolding. This is a single step cooperative denaturation as indicated by the viscosity profile. At extreme acid pH values (below pH 2.0) the protein associates or folds to a different conformational motif as shown by blue shift of ultraviolet fluorescence emission maximum and decrease in reduced viscosity values by more than 30% due to an entropically driven hydrophobic interaction. The conformational analysis of beta-globulin showed a decrease up to pH 3.0, followed by an increase in the ordered structure at low pH values indicating that the low pH values stabilized this new conformation. These results are discussed in view of the molten globule structure of proteins.

Beta-Globulins↗
PubMed1991

Structural stability of lipase from wheat germ in alkaline pH.

The present investigation shows the effect of alkaline pH on the structure-function relationship of lipase from wheat germ. There is a 70% decrease in lipase activity at pH 10.0, which decreases to 93% at pH 12.0 as compared to neutral pH activity (Rajendran et al. 1990). This change is shown to be as a result of loss of alpha-helical structure with a concomitant increase in aperiodic structure. The results with fluorescence spectra and tyrosyl ionization indicate gradual exposure of aromatic side chains of tyrosine and tryptophan to the bulk solvent along with the structural changes. The enzyme is in an extended form at alkaline pH with a volume change of - 1300 ml mol as also indicated by increase in reduced viscosity to 12.5 ml g and significant decrease in sedimentation coefficient. The kinetics of the reaction points to a cooperative pseudo first-order reaction as determined by stopped-flow kinetic analysis in the ultraviolet region. The inactivation mechanism appears to follow a two-step mechanism of a fast and a slow reaction.

Chemical Phenomena↗
PubMed1991

Deafness in children--an analysis.

This study was conducted at the Government Deaf and Dumb School, Thanjavur to ascertain the possible etiological factors. The social outlook of the parents of these children was analysed. Boys were more often affected (60.2%). Consanguinity was observed in 65.4% parents; 23.1% had one or more affected sibling and 14.1% had affected relatives. Parents detected the hearing disability in their children between 3-6 months of age in about 79% cases. Syphilis and chickenpox were the common antenatal associated infections. Streptomycin, chloroquine and abortificients were used during early pregnancy. Eight were preterm and 9 were asphyxiated at birth. A total of 11.5% had purulent ear discharge, and 2 had ear injury. Parents were committed to help the children to be self dependent.

Abortifacient Agents↗
PubMed1990

Effect of pH in the acidic region on the structural integrity of lipase from wheat germ.

To understand the structure-function relationship of the enzyme lipase the effect of acid pH on the activity of lipase has been followed using a number of physico-chemical techniques. Lipase from wheat/germ has S20,w value of 2.2 S and a molecular weight of 42,000 +/- 1,000. The enzyme has an intrinsic viscosity of 4.72 ml/g indicating it to be elongated in shape. With decrease in pH below 7.0 microenvironmental changes occur in the neighborhood of active site accompanied by minor conformational changes without any gross change in the hydrodynamic properties of the protein, as monitored with ultraviolet difference spectra, fluorescence spectra, viscosity and circular dichroism. The kinetics of the inactivation process has been established as consisting of a fast step and a slow step with a k value of 73/sec and 7.2/sec respectively. At extreme acid pH the enzyme reaggregates to a polymer arising out of hydrophobic interaction and the polymer has no activity.

Hydrogen-Ion Concentration↗
PubMed1988

Association-dissociation and denaturation-renaturation of high-molecular-weight protein: carmin from safflower seed (Carthamus tinctorius L.) in alkaline solution.

The effect of alkaline pH on the association, dissociation, and denaturation of carmin, the high-molecular-weight protein from safflower seed was investigated in the pH range 7-12, using various biophysical techniques. The results indicate that the multimeric protein carmin dissociates at pH 8.0 where denaturation has not set in. The association-dissociation of the protein can be represented schematically as 11S in equilibrium 7S in equilibrium 4S----2S. Above pH 10, the protein undergoes simultaneous dissociation and denaturation. The denaturation process appears to be complete at approximately pH 12.5. The protein undergoes conformational change and covalent modifications and cleavage during the denaturation process. A reversibility study shows that the process of dissociation is reversible to a large extent, whereas denaturation appears to be irreversible. These results are discussed in terms of association-dissociation, denaturation and alkaline-catalyzed covalent modifications and cleavage of seed proteins.

Hydrogen-Ion Concentration↗
PubMed1986

Population movement and malaria persistence in Rameswaram Island.

The role of population movement on the persistent transmission of malaria in Rameswaram Island was studied. Majority of the inhabitants of the island are fishermen, who engage in perennial fishing. They move from one coastal place to the other for fishing and stay in temporary camps depending on season and fish availability. Such seasonal fishing camps attract fishermen from the mainland coastal villages also. The parasitological and entomological studies carried out in these places reveal that some of the camps are highly vulnerable to the movement of individuals with malaria infection and highly receptive. Rameswaram being a holy place, receives pilgrims from all over India and Nepal. Plasmodium falciparum cases recorded from the pilgrims of North India indicate the danger of the possible introduction of chloroquine-resistant parasite in the island. Also, a large number of passengers in transit from various countries, many of which are at risk of malaria transmission, stay in the island before or after visiting Sri Lanka. Such population movements being a continuous and regular feature are significant and result in failures in the operational programmes.

Anopheles↗
PubMed1978

Dialysis, depression and antidepressants.

The treatment of depression occurring in patients undergoing chronic renal dialysis is discussed. This study was conducted on a Dialysis Unit where 10 Travenol dialyzers of the recycling single by-pass type are used to maintain a total of 22 patients. Imipramine in the usual dosage range and schedule was used when an antidepressant was indicated.

Adjustment Disorders↗
PubMedDate not supplied

Bifid pancreas. An unusual anomaly associated with acute pancreatitis.

Pancreatic divisum and the ectopic pancreas are well-known anatomic anomalies. However, the bifid pancreatic duct is less common and is still poorly understood. The present case report examines this anatomic variant. We observed a bifid pancreatic duct in an elderly man with abdominal pain and an elevated level of serum amylase. An endoscopic papillotomy resulted in clinical improvement.

Acute Disease↗