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S R Narayanan

Publications and source records attributed to S R Narayanan.

8 recordsLinked to original sources
PubMed2006

Anhydrous proton-conducting polymeric electrolytes for fuel cells.

The need to design proton-conducting electrolytes for fuel cells operating at temperatures of 120 degrees C and above has prompted the investigation of various "water-free" polymeric materials. The present study investigates the properties of "water-free" proton-conducting membranes prepared from high-molecular-weight polymeric organic amine salts. Specifically, the properties of bisulfates and dihydrogenphosphates of poly-2-vinylpyridine (P2VP), poly-4-vinylpyridine (P4VP), and polyvinylimidazoline (PVI) have been investigated over the temperature range of 25-180 degrees C. Nanocomposites of these polymeric organic amine salts and hydroxylated silica have also been investigated in this study. These polymers are found to be stable and proton-conducting at temperatures up to 200 degrees C. In all the polymer examples studied herein, the phosphates are more conducting than the bisulfates. The activation energy for ionic conduction was found to decrease with increasing temperature, and this is associated with the increased polymer mobility and ionization of the proton. This is confirmed by the high degree of motional narrowing that is observed in proton NMR experiments. The measured values of conductivity and the differences in pKa values of the polymeric organic amine and the mineral acid are clearly correlated. This observation provides the basis for the design of other water-free acid-base polymer systems with enhanced proton conductivity. The results presented here suggest that anhydrous polymer systems based on acid-base polymer salts could be combined with short-range proton conductors such as nanoparticulate silica to achieve acceptable conductivity over the entire temperature range.

Electric Power Supplies↗
PubMed1997

A quantitative circular dichroic investigation of the binding of the enantiomers of ibuprofen and naproxen to human serum albumin.

The binding constants for racemic, R and S naproxen and ibuprofen to human serum albumin have been determined by a circular dichroic technique. The ibuprofens and naproxens show no measurable extrinsic optical activity on interaction with the protein, and so the extrinsic Cotton effect shown following the diazepam-albumin interaction is used as a probe. The presence of the drugs reduce the amount of diazepam bound as shown by the interaction is used as a probe. The presence of the drugs reduce the amount of diazepam bound as shown by the reduced size of the induced ellipticity. The calculated primary binding constants show that the S form of both drugs bind to the albumin more tightly than the R form and that the racemic forms bind less tightly than either enantiomer.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1996

The effect of octanoic acid on the binding of the enantiomers of ibuprofen and naproxen to human serum albumin: a chromatographic implication.

PURPOSE: The heats of reaction between the enantiomers and racemates of ibuprofen and naproxen and human serum albumin (HSA) are to be measured with and without the addition of octanoic acid. The effects of octanoic acid on the free energies of interaction between the drugs and HSA is to be determined and compared to that estimated from theoretical equations. METHODS: The heats of reaction have been measured directly by flow microcalorimetry. RESULTS: The data showed that octanoic acid lowered the 1:1 binding constants for all the drug-HSA interactions investigated. The effect of octanoic acid was greater on the R than on the S forms of the drugs as shown by the differences in free energies of interaction in the presence and absence of octanoic acid. CONCLUSIONS: The increased free energy differences for the binding of the enantiomers of both drugs to HSA in the presence of octanoic acid is closer to the value deemed to be necessary for the separation of enantiomers by Davenkov, and shows the importance of the addition of octanoic acid to the mobile phase in the separation of these enantiomers on immobilized albumin columns.

Calorimetry↗
PubMed1992

Immobilized proteins as chromatographic supports for chiral resolution.

This review examines the role of protein-bonded chiral stationary phases (CSPs) in enantiomeric separation and investigates the performance characteristics and desired properties of protein CSPs for separation and large-scale operation. The review also discusses the ability of protein-based CSPs to examine the stereochemistry of drug metabolism processes.

Animals↗
PubMed1990

"Glutaraldehyde-P", a stable, reactive aldehyde matrix for affinity chromatography.

A high-performance affinity chromatography support based on silica has been developed for the immobilization of proteins containing primary amino groups. A hydrophilic polymer covalently bound to the silica surface minimizes nonspecific protein binding to the support while preserving high binding capacity. The Schiff base reaction involved in the coupling of a ligand to the affinity medium is rapid, allows the use of mild conditions during the coupling process, and results in a very stable linkage. Reaction parameters were studied for protein coupling to the affinity support to determine optimum binding conditions and dynamic capacity as a function of protein size. The stability of the ligand-matrix bond was determined. The performance and reproducibility of the affinity support are demonstrated by its use in the analysis of nitrophenyl sugar derivatives, purification of glycoproteins, and isolation of anti-bovine immunoglobulin G developed in rabbit.

Animals↗
PubMed1990

Affinity chromatography supports: a look at performance requirements.

Because of its high selectivity, affinity chromatography is a preferred tool in the downstream processing of high-value proteins and peptides of therapeutic interest. This review examines the affinity supports currently available, and investigates the performance characteristics and properties required of the support matrices for improved affinity-based supports for large-scale purification of biomolecules. Parameters for optimizing an affinity chromatographic process, and the advantages of affinity-based separation for scaled-up systems are highlighted.

Chromatography, Affinity↗
PubMed1988

Purification of bovine liver S-adenosylhomocysteine hydrolase by affinity chromatography on blue dextran-agarose.

S-Adenosylhomocysteine (AdoHcy) hydrolase (adenosylhomocysteinase, EC 3.3.1.1) was purified from bovine liver by conventional protein purification procedures (differential centrifugation, ammonium sulfate fractionation and DEAE-cellulose chromatography) followed by affinity chromatography on blue dextran coupled to agarose. The enzyme was eluted from the blue dextran-agarose column with adenosine and the adenosine was removed by chromatography on Sephadex G-75. The affinity chromatography step resulted in a substantial increase in total AdoHcy hydrolase activity (about 600%) suggesting either removal of some inhibitory substance or a change in the structure of the protein producing a more catalytically efficient enzyme. The isolation procedure afforded over 3400-fold purification of the enzyme, which was shown to be homogeneous by polyacrylamide gel electrophoresis. Using high pressure liquid chromatography, the nucleotide content of the freshly purified enzyme was determined to be 2 mol of nicotinamide adenine nucleotide per mol of enzyme tetramer. The ratio of the reduced to the oxidized form of the nucleotide was correlated to the activity of the enzyme preparation.

Adenosylhomocysteinase↗