Biomedical subjects

J Steensgaard

Publications and source records attributed to J Steensgaard.

35 records · Page 2Linked to original sources

PubMed1977

The properties of immune complex-forming systems. A new theoretical approach.

A new mathematical model for antigen-antibody interactions has been developed. The new model is based on the assumption that the formation of complexes between a bivalent antibody and a multivalent antigen is determined thermodynamically by the concentrations and valences of antigen as well as antibody, together with one association constant which is common to all mutual interactions. Formulae have been derived for calculation of the distributions of compositionally different antigen-antibody complexes either from knowledge of equilibrium concentrations of free antigen and antibody, or from knowledge of total amounts of antigen and antibody in the system. A computer program for these calculation is described. The model is found to yield precise predictions of the formation of soluble immune complexes, as studied by zonal centrifugation. It is found through use of the model that 'complex formation' as such differs in binding characteristics from adsorption, especially for high concentrations of antigens and antibodies. 'Complex formation' implies that association constants estimated through a Sips plot method will vary with antibody concentration, and that certain curvatures of the lines in a Sips plot reflect inherent properties of complex-forming systems.

Antigen-Antibody Complex↗

PubMed1975

The effects of overloading in density-gradient centrifugation.

The effects of overloading of the sample zone in density gradient centrifugation have been studied by use of a three-component shelf-lavered sample in which the total protein concentration was increased by addition of different amounts of albumin. It is found that overloading of the gradient gives rise to particle movements which are not predictable from the Svedberg equation. The two typical effects of overloading are dislocation of the zone mass centres and changes in the zone shapes. It is found that the magnitude of the calculated sedimentation coefficients increases nearly linearly with increasing sample load. The changes in zone shapes are found to depend on the specific load and two different patterns may be distinguished. The zone of the sample component which causes the overloading is defined as primarily overloaded and the others as secondarily overloaded. In primarily overloaded zones the original Gaussian shape is lost, while in secondarily overloaded zones the Gaussian zone shape is maintained, although a zone broadening is seen. Extreme high loads are found to be able to divide single zones. As a whole these experiments show that evidence for a non-overloaded set of experimental conditions must be provided, when density gradient centrifugation is used for determination of sedimentation coefficients. For preparative gradient centrifugations the power of resolution will decrease with increasing sample load. A simple method to detect overloading in density gradient centrifugations is described.

Animals↗

PubMed1975

Properties and immunochemical reactivities of carboxy-modified human serum albumin.

Seven carboxy modified and four amino modified derivatives of human serum albumin have been prepared and studied by optical rotatory dispersion measurements, gel filtration, immunoelectrophoresis, immunodiffusion and by use of an ammonium sulphate technique. It is found that carboxy groups are of major importance for the maintenance of the structure and function of human serum albumin, and that carboxy modification has a much more profound effect than amino modification has to the same relative extent.

Ammonium Sulfate↗

PubMed1975

Computer simulation of immunochemical interactions.

A computer model for simulation of the interactions between a macromolecular antigen and its corresponding IgG has been developed. The model takes all possible immune complexes into account, and it calculates the most probable immune complex distribution patterns on the basis of basic thermodynamic principles from the valences and initial concentrations of antigen and antibody, respectively, together with an association constant assumed to be common to all mutual interactions. In antigen excess small antigen-rich complexes are predicted. At or near equivalence a rich variety of relatively small complexes is predicted, while in antibody excess complexes of the type AgAbn are found to be the most probable. By further assuming that the precipitate consists of antibody excess complexes, a precipitin curve can be calculated. The agreement between calculated results and experimentally obtained data is found to be good. It is of special interest that this theory implies that the outcome of immunochemical interactions depend equally well on the concentrations of antigen and of antibody.

Animals↗

PubMed1974