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Biomedical subjects

A Sadana

Publications and source records attributed to A Sadana.

11 recordsLinked to original sources
PubMed1992

Binding kinetics of antigen by immobilized antibody: influence of reaction order and external diffusional limitations.

The influence of reaction order and external mass transfer limitations on the binding kinetics of antigen in solution to antibody covalently or non-covalently attached to a cylindrical fiber-optic biosensor is presented. Both single-step and dual-step binding of antigen to antibody is considered. The rate of attachment of antigen to antibody is linear for all reaction orders in the time frame (100 min) considered. The rate of attainment of saturation levels of antigen in solution close to the surface is very rapid (within 20 min). An increase in the presence of mass transfer (denoted by a Damkohler number increase) decreases the saturation level of the antigen close to the surface, and the rate of antigen attachment to the antibody covalently or non-covalently bound on the surface for one-half, one, one and a half, and second-order reaction. As intuitively expected, an increase in the initial antigen concentration in solution increases the saturation level of the antigen close to the surface, and the rate of antigen attachment to the antibody covalently bound on the surface for all the reaction orders considered. Non-dimensional plots presented in the analysis help extend the analysis to different antigen-antibody systems. A decrease in the external diffusional limitations has an effect of decreasing the effect of reaction order on the saturation levels of antigen close to the surface and the rate of attachment of the antigen in solution to the antibody on the surface.

Antigen-Antibody Reactions↗
PubMed1992

Inactivation of proteins and other biological macromolecules during chromatographic methods of bioseparation.

The denaturation of proteins and other biological macromolecules such as gentamycin, mRNAs, and long-chain fatty acids during their separation by different chromatographic techniques is analyzed. Non-conventional techniques such as centrifugal partition chromatography are also examined. Particular attention is paid to the denaturing mechanisms prevalent under processing conditions, and how denaturation may perhaps be alleviated under laboratory conditions or during scale-up. The available mechanistic studies shed physical insights into the conformational behavior of proteins on chromatographic columns. Mechanistic studies of other biological macromolecule separation on columns is rare. Numbers for both recovery and purity of the biological product are presented wherever available. Scale-up studies are rare, nevertheless, those that are presented together do provide significant and valuable information, and may be generalized to other systems with caution.

Animals↗
PubMed1991

Bioseparation using affinity techniques.

Bioseparation of proteins from dilute solutions using different novel affinity procedures is reviewed. Emphasis is also placed on the quality of the product separated. Whenever possible, physical insights into the separation procedure are provided, besides indicating suitable directions where appropriate further research may be carried out. The procedures analyzed are different affinity chromatographic techniques, affinity separation using liquid perfluorocarbon supports, water soluble nonionic surfactants for affinity bioseparations, affinity cross-flow filtration, bioaffinity separation using reversed micelles, affinity precipitation and dual-functional affinity protein purification.

Cellulose↗
PubMed1990

Stability index for enzymes deactivating by different mechanisms.

A quantitative procedure for estimating changes in enzyme stability upon chemical modification is presented. Stability index for different deactivation mechanisms is presented and applied to different enzyme deactivations. The stability index provides a convenient method of estimating changes in enzyme stability upon chemical modification.

AMP Deaminase↗
PubMed1990

Protein/enzyme inactivation during different chromatographic methods of separation.

Protein denaturations encountered during the different types of chromatographic separations are presented. The analysis of different protein denaturations presented along with the causes of such denaturations provides a judicious framework to compare protein denaturations encountered by such separation techniques. Especially of interest are those studies which compare the mass recovery of proteins and the retention of activity by different chromatographic techniques. Reversed-phase chromatography is presented even though it is utilized nowadays only for specialized cases such as separation of small peptides. It appears that relatively mild interactions that are encountered generally in hydrocarbon-interaction chromatography are favorable to the preservation of the native (active) protein state. The few available mechanistic studies presented provide judicious physical insights into protein conformational behavior on chromatographic columns.

Animals↗
PubMed1988

Vasculitis in Reiter's syndrome.

A patient is described with both Reiter's syndrome and cutaneous vasculitis characterised by livedo reticularis. The development of the Reiter's syndrome immediately preceded the onset of vasculitis. It is suggested that Reiter's syndrome is a previously unrecognised potential cause of vasculitis in which infection may initiate the vasculitic reaction.

Adult↗
PubMed1985

A mathematical analysis of aging influences on enzyme deactivation/activation kinetics. Examples of the influence of regional brain development and drugs in rats.

A series-type enzyme deactivation/activation model involving active enzyme states is utilized to theoretically quantify the influence of regional brain development and drugs on enzyme activity levels in rats. Continuous hexachlorobenzene administration with, or without, phenobarbitone pretreatment has different effects on the deactivation/activation kinetics of porphyrinogen carboxylase, delta-aminolaevulinate synthase and delta-aminolaevulinate dehydratase. The deactivation/activation kinetics exhibited by pyruvate dehydrogenase, citrate synthase, and D-3-hydroxybutyrate dehydrogenase during the development of the medulla oblongata, mid-brain, striatum, and hypothalamus sections exhibit similarities as well as discrepancies. These are identified and made more quantitative.

5-Aminolevulinate Synthetase↗
PubMed1985

A mathematical analysis of the influence of aging on enzyme deactivation kinetics.

A series-type enzyme deactivation model is utilized to examine and to quantify the influence of aging on the deactivation kinetics of various enzymes. The effect of in vivo aging as well as the influence of "dwell time" on the deactivation kinetics of enzymes from organisms and cells of different age is examined. The influence of chemical modifiers on the deactivation kinetics of enzymes from cells of different age is elucidated. Attempts have been made to suggest and provide reasonable explanations for the structure-function relations for aging-influenced enzymes.

Aging↗
PubMedDate not supplied

Interfacial protein adsorption and inactivation.

Protein inactivations at liquid-liquid, gas-liquid, and liquid-solid interfaces are presented. Wherever possible the mechanisms of protein inactivation, the extent of inactivation, and means by which this inactivation may be minimized are presented. Emphasis is placed on the 'quality' or the heterogeneity of the protein absorbed at the different types of interfaces. The analysis of the adsorption of proteins at different types of interfaces presented together provides novel physical insights into protein interactions at interfaces. The influence of protein adsorption at interfaces on bioseparations is analyzed by discussing examples on two-phase separations, fermentation systems, membrane separation systems, and chromatographic separations. Valuable knowledge gained during protein adsorption for biomedical applications may be applied with caution to bioseparation systems wherever appropriate. Future theoretical and experimental analysis on protein adsorption in bioseparation systems should pay more attention to the 'quality' of the protein adsorbed at the interface.

Adsorption↗