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At least 1,207 records · Page 67Linked to original sources
PubMed1978

The distribution and lipid composition of ultracentrifugally separated lipoproteins of young and old rat plasma.

The lipoproteins of young and old Wistar rats differ markedly in distribution and chemical composition. The major differences are: (1) the presence of high levels of free and esterified cholesterol, triglycerides and free fatty acids in the lipoproteins of old rat plasma when lipids are analyzed/100 ml of plasma. However, the ratio of total cholesterol to protein mass indicates the presence of comparable cholesterol pools in all lipoprotein fractions of young and old rats excepting the d 1.063--1.21 fraction where a higher cholesterol pool in old rats is indicated. (2) The amount of sphingomyelin increases in lipoprotein fractions of old rat plasma thereby actually decreasing the lecithin/sphingomyelin ratio in these plasma fractions. (2) Unsaturated fatty acids predominate in young rat plasma lipoproteins, and saturated fatty acids predominate in old rat lipoprotein fractions. The ratio of polyunsaturated (linoleic, linolenic, arachidonic) to saturated (palmitic, stearic) fatty acids in young rat sera was 0.89 and in old rat sera, 0.55.

Aging↗
PubMedDate not supplied

Removal of SDS from proteins for immunochemical analyses: a simple method utilizing ultracentrifugation in sucrose density gradients containing non-ionic detergent.

A simple method for removal of SDS from proteins is described. SDS-treated proteins are centrifuged through sucrose density gradients containing Triton X-100. Proteins possessing sedimentation coefficients of > 4 S separate from the bulk of SDS, which remains at the top of the sucrose gradients. Quantitative immunoelectrophoretic analyses of SDS-treated human serum proteins and human erythrocyte membrane proteins indicate that the majority of the proteins tested is subsequently precipitable with specific antisera. Initial membrane solubilization with SDS can thus be followed up by a fractionation step that will yield many proteins in a state immediately suitable for bioimmunochemical analyses.

Blood Proteins↗
PubMed1987

Buoyant density and molecular weight calculations on an Apple II microcomputer from equilibrium banding experiment on analytical ultracentrifuge.

Buoyant density is one of the non-destructive measurements of viruses, nucleic acids etc. which help in characterizing these entities in terms of their chemical composition and physical conformation. In recent years equilibrium sedimentation in CsCl buoyant density gradient has been proved to be a powerful tool for genome characterization. The method enables one to obtain information such as the absolute and the relative buoyant density of the material and its molecular weight. This communication describes a program in BASIC which calculates these parameters from the raw data obtained directly from the experiment. The program is fully interactive, user-oriented, and written keeping in view biologists and biochemists as the main users. The program has a built-in option to calculate either the absolute or the relative buoyant density and the molecular weight.

Algorithms↗
PubMed2004

Solution structure determination of monomeric human IgA2 by X-ray and neutron scattering, analytical ultracentrifugation and constrained modelling: a comparison with monomeric human IgA1.

Immunoglobulin A (IgA), the most abundant human immunoglobulin, mediates immune protection at mucosal surfaces as well as in plasma. It exists as two subclasses IgA1 and IgA2, and IgA2 is found in at least two allotypic forms, IgA2m(1) or IgA2m(2). Compared to IgA1, IgA2 has a much shorter hinge region, which joins the two Fab and one Fc fragments. In order to assess its solution structure, monomeric recombinant IgA2m(1) was studied by X-ray and neutron scattering. Its Guinier X-ray radius of gyration R(G) is 5.18 nm and its neutron R(G) is 5.03 nm, both of which are significantly smaller than those for monomeric IgA1 at 6.1-6.2 nm. The distance distribution function P(r)for IgA2m(1) showed a broad peak with a subpeak and gave a maximum dimension of 17 nm, in contrast to the P(r) curve for IgA1, which showed two distinct peaks and a maximum dimension of 21 nm. The sedimentation coefficients of IgA1 and IgA2m(1) were 6.2S and 6.4S, respectively. These data show that the solution structure of IgA2m(1) is significantly more compact than IgA1. The complete monomeric IgA2m(1) structure was modelled using molecular dynamics to generate random IgA2 hinge structures, to which homology models for the Fab and Fc fragments were connected to generate 10,000 full models. A total of 104 compact best-fit IgA2m(1) models gave good curve fits. These best-fit models were modified by linking the two Fab light chains with a disulphide bridge that is found in IgA2m(1), and subjecting these to energy refinement to optimise this linkage. The averaged solution structure of the arrangement of the Fab and Fc fragments in IgA2m(1) was found to be predominantly T-shaped and flexible, but also included Y-shaped structures. The IgA2 models show full steric access to the two FcalphaRI-binding sites at the Calpha2-Calpha3 interdomain region in the Fc fragment. Since previous scattering modelling had shown that IgA1 also possessed a flexible T-shaped solution structure, such a T-shape may be common to both IgA1 and IgA2. The final models suggest that the combination of the more compact IgA2m(1) and the more extended IgA1 structures will enable human IgA to access a broader range of antigens than either acting alone. The hinges of both IgA subclasses appear to show reduced flexibility when compared to their equivalents in IgG, and this may be important for maintaining an extended IgA structure.

Amino Acid Sequence↗
PubMed1999

Analysis of fibrous network fluid permeation data using the theory of ultracentrifugation: application to fibrin gels.

A new and alternative method for calculating the strand diameter of fibrous gel networks from fluid permeation data is developed and used to analyze and compare previous Darcy constant measurements of fibrin gels. The calculated diameters from the various sets of experimental data using this method gives for a coarse fibrin clot a strand diameter of approximately 1000 A and for a fine fibrin clot a strand diameter of 170 A.

Journal Article↗