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At least 703 records · Page 39Linked to original sources
PubMed1983

Polarization fluorescence, spin label and ultracentrifugal studies of specific interaction of low molecular weight proteins with the Fc fragment of human immunoglobulin G.

Low mol. wt (about 2000) proteins which were found in normal human serum formed complexes with the Fc fragment of IgG. The interaction constant was not less than 10(6) l/mole. These complexes dissociated on dilution of the protein solution to below 2 microM or decreasing the pH below 6. The binding site of these proteins was located in the CH2 domains in close proximity to the carbohydrate moieties. The dissociation of IgG complexes with these proteins was accompanied by a conformational change in the Fc fragment.

Blood Proteins↗
PubMed1976

Collecting and processing records from the ultracentrifuge in "real-time" using an on-line computer.

An analytical system consisting of an analytical cantrifuge coupled 'on-line' to a computer was assembled and tested. Collection of records from up to 9 solutions was achieved through programmes which sum readings to reduce noise as well as controlling the positioning of the scanner. With this system it was found that the limit on accuracy for molecular weights at concentrations less than 0.01 g cm-3 was +/- 3% estimated from sedimentation equilibrium experiments. The same system was used to collect records for similar concentrations from velocity experiments by employing a scanning schlieren. In this case the accuracy in estimating sedimentation coefficients was similar to those found when measuring photographs. Since the collection yields detailed information about the shape of the sedimenting boundary, the centroids of the boundary were routinely computed by second moment analysis rather than relying on the position of the maximum of the schlieren peak. In the same analysis estimates of diffusion coefficients were made routinely by calculating corrected height/area ratios for each scan. These calculations were made during the real-time of the experiment, so making available molecular parameters rather than records which must be evaluated some time after stopping the experiment.

Computers, Hybrid↗
PubMed1976

Sedimentation in the ultracentrifuge and diffusion of macromolecules carrying electrical charges.

The calculation of Alexandrowicz and Daniel of the charge effect in the sedimentation of macromolecules carrying electrical charges was reformulated by introducing buoyant molecular weights and concentrations of electroneutral components only (rather than those of the ionized species) in the final equations. Some interesting limiting cases are discussed. A similar calculation was performed for the case of isothermal diffusion. It is also shown how the present discussion relates to more elaborate treatments of the sedimentation and diffusion of polyelectrolytes by the methods of irreversible thermodynamics.

Electric Conductivity↗
PubMed1991

Density determination by analytical ultracentrifugation in a rapid dynamical gradient: application to lipid and detergent aggregates containing proteins.

A rapidly developing dynamical gradient can be formed in the analytical centrifuge when a buffer solution prepared in D2O is underlayered under the same buffer solution prepared in H2O in a specially designed double sector cell. In a short time the boundary layer spreads to form the gradient. Heavy particles (S greater than or equal to 10S) will band in the gradient corresponding to their density, which can be determined accurately. To this end, the buffer may contain density adjusting additives such as sucrose. We present results with this technique for lipid vesicles, for a Ca-antagonist bound to vesicles, as well as for a lipoprotein and reconstituted regular membrane protein-lipid arrays.

Animals↗