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Biomedical subjects

J Q Oeswein

Publications and source records attributed to J Q Oeswein.

8 recordsLinked to original sources
PubMed1991

Effect of freezing on aggregation of human growth hormone.

The effect of freezing on formation of soluble and insoluble aggregates of human growth hormone (hGH) was studied. The amount of soluble aggregates was affected very little by freezing regardless of the cooling rate. In contrast, the formation of insoluble aggregates (particulates), as determined by light scattering in the 340- to 360-nm range, was found to increase sharply with increasing cooling rates. The amount of these particulates was also dependent on the pH of the solution. Freezing hGH solutions formulated at pH 7.4 resulted in highly scattering solutions, whereas pH 7.8 formulations showed significantly less scattering. These results emphasize the importance of understanding the freezing phenomenon for protein solutions and suggest that the formation of soluble aggregates and insoluble particulates may have different mechanisms.

Freezing↗
PubMed1983

Human serum low density lipoprotein-sodium deoxycholate interaction.

The binding of sodium deoxycholate to low density lipoprotein (LDL) is a relatively fast process, as compared to the lipid displacement reaction and solubilization. The initial reaction has a bimolecular rate constant of approximately 539 M-1 S-1. In the presence of 1 mM sodium deoxycholate, below critical micelle concentration, 0.04 g of sodium deoxycholate was bound per g of LDL, resulting in an increase in particle radius from 102 to 128 +/- 0.3 A and an axial ratio of 5.6 for a prolate ellipsoid. Such increases were also observed using higher sodium deoxycholate concentrations and are apparently due to sodium deoxycholate-induced elongation or distortion of certain portions of LDL.

Chromatography, Gel↗
PubMed1983

Interaction of human serum apolipoprotein B with sodium deoxycholate.

Preparation of apolipoprotein B (Apo B)-deoxycholate (DOC) complexes by gel filtration chromatography in the presence of 20 mM DOC, pH 8.5, gave two populations of particles with 5% (peak I) and 13% (peak II) lipid remaining bound. These complexes were initially shown to be very large and elongated, with partition radii of approx. 131 +/- 0.5 A, weight average molecular weights of approx. 164 000 +/- 1 000, and an intrinsic viscosity of 80.19 +/- 2.21 ml/g. Additionally, they appeared very similar to native low-density lipoprotein on sodium dodecyl sulfate-polyacrylamide gels, giving one major band. Incubation of these samples for 10 days under nitrogen at 4 degrees C in the presence of antibiotics and protease inhibitor resulted in dissociation to many smaller subunits. Results of scanning molecular sieve chromatography and analytical ultracentrifugation showed that dissociation of these complexes was relatively slow and indicated the presence of at least two classes of components in fresh samples: one a very elongated complex with a radius directly correlated to the DOC/Apo B ratio and inversely correlated to sample aging; and another of much smaller radius which was independent of DOC/Apo B ratio but directly correlated to sample aging; indicating that these dissociated subunits interact with each other to an appreciable extent. Furthermore, these complexes were found to undergo a preferential hydration upon interaction with DOC, which may contribute to large changes in their effective specific volumes, as well as to dissociation of subunits.

Apolipoproteins↗
PubMed1981

Density and composition models for lipoproteins.

Two theoretical models for lipoprotein particle structure are proposed, based on density and composition and utilizing the Stokes' coefficient as evaluated from the Maude-Whitemore expression, using analytical ultracentrifugation. These density and composition models are compared with the Corey-Pauling-Koltun space-filling model proposed by Verdery and Nichols, and that proposed by Shen et al., which has a sharply defined boundary between the hydrophobic core and the amphipathic layer surrounding it. Results of our calculation of the percentage of total apolar lipid accommodated in the outer hydrophobic core -28, 64 and 94% for LDL, HDL2 and HDL3, respectively - suggest that there may be differences among these three lipoproteins classes in both the packing of cholesteryl ester and triglyceride as well as the conformation of apolipoproteins at the particle's surface.

Apolipoproteins↗
PubMed1979

Thermodynamic compensation process in interacting protein systems: definition of thermodynamic compensatory temperature, (Tc).

In our thermodynamic analysis of the non-linear Van't Hoff expression as applied to several self-associating systems -- specifically in the cases of bovine liver L-glutamate dehydrogenase (GDH), glucagon and S-carboxymethylated apo A-II protein from human high density lipoprotein -- we have examined the interrelationships of a number of thermodynamic temperatures as they affect the association process. We found the principal determinants of the linear thermodynamic compensation process to be delta S0(T)/delta C0p(T) = (delta T'C)/(Texp), where (delta T'C) = Texp). We have defined the unique compensatory temperature, (TC), for any interacting system, at which the contributions of enthalpy and entropy to the association process are balanced.

Animals↗
PubMed1978

Increased sodium plus potassium adenosine triphosphatase activity in erythrocyte membranes in Huntington's disease.

Dopa-decarboxylase, acetylcholinesterase, sodium plus potassium stimulated adenosine triphosphatase (Na+ + K+-ATPase), and membrane-bound protein kinase were compared in the erythrocytes of patients with Huntington's disease and normal controls. All these enzymes also exist in the basal ganglia. The Na+ +K+-ATPase level was elevated (p less than 0.05) in Huntington's disease, while no significant changes were observed in the other enzymes. This finding is consistent with the concept that Huntington's disease is associated with a general membrane abnormality.

Acetylcholinesterase↗
PubMedDate not supplied

A turbidimetric method to determine visual appearance of protein solutions.

An instrumental method to analyze protein solutions for visual appearance is described which is based on spectrophotometric comparison to reference suspensions with varying degrees of turbidity. This method provides a useful substitute for visual inspection of uniform opalescent suspensions in that it is more convenient and less time-consuming and has the potential to be more reproducible, accurate and objective. Established categories of opalescence based on European Pharmacopoeial reference suspensions were determined using turbidity measured as optical density in the 340-360 nm range. A comparison of the mean optical density of a protein sample to those of the reference suspensions allowed a more reproducible assignment of the sample's category of opalescence than that of visual inspection.

Chemistry, Physical↗