Search PubMed⌕ Search

Biomedical subjects

C Jacobsen

Publications and source records attributed to C Jacobsen.

At least 109 records · Page 6Linked to original sources
PubMed1982

Determination of affinity of monoclonal antibodies against human IgG.

A method for determining the affinity and the concentration of mouse monoclonal antibodies against human IgG has been developed. The method comprises two steps. First, monoclonal antibodies are allowed to combine with radioiodinated human IgG. Secondly, mouse monoclonal IgG with and without complexed IgG is precipitated with rabbit IgG against mouse IgG. As the antigen is divalent complexes of varying composition are formed in this system leading to deviations from linearity in plots obtained in commonly employed analytical systems. The theoretical background of these systems has been studied by computer stimulation, and a concentration effect on the formation of immune complexes were demonstrated. The affinities (in terms of the association constants (of 6 monoclonal antibodies were estimated and found to be in the range from 2 X 10(6) M-1 to 5 X 10(8) M-1.

Animals↗
PubMed1982

Theoretical and ultracentrifugal analysis of immune complex formation between monoclonal antibodies and human IgG.

Immune complex formation of four different mouse monoclonal antibodies against human IgG has been studied using analytical zonal centrifugation. A theoretical model has been used to depict thermodynamic ideal immune complex formation of monoclonal antibodies. It was found that the four monoclonal antibodies differed very much with respect to immune complex formation with human IgG. One of the monoclonal antibodies formed immune complexes in agreement with the theoretical model. Another was strongly related thereto. A third monoclonal antibody formed only a single complex and might exhibit a positive co-operativity between its two sites. A fourth formed as excess of a possibly cyclic complex. Thus monoclonal antibodies differ substantially with respect to physical properties adding a new aspect to the problems of antibody heterogeneity. It is moreover found that analytical zonal centrifugation can be used to estimate the number of antigenic determinants and antibody-binding sites thereby assuring whether or not a particular IgG monoclonal antibody has two binding sites.

Antibodies, Monoclonal↗
PubMed1980

Solubility properties of IgG immune complexes. Comparison between the effects of low molecular weight solvents and polyethylene glycols.

A systematic study of the influence of organic solvents on the interaction between human IgG and rabbit anti-human IgG IgG++ has been conducted, using difference turbidity and sucrose gradient centrifugation methods. It was found that very small alcohols like methanol and ethanol increased the turbidity signal, whereas larger alcohols (propanol, isopropanol, propanediol and ethylene glycol) had no influence on the signal. Sucrose, dioxane, dimethylformamide and dimethylsulphoxide decreased the difference turbidity signal. Sucrose gradient centrifugation did not show any influence. Polyethylene glycols were investigated with regard to molecular weights as well as concentrations. In contrast to the low molecular weight solvents, polyethylene glycols with molecular weights from 600 up to 20,000 gave a clearly expressed increase in the development of turbidity as well as in the size of the final turbidity signal. By sucrose gradient centrifugation, it was found that polyethylene glycols of molecular weights from 1000 to 10,000 had a profound effect on the solubility of immune complexes. The influence depended on the molecular weight as well as on the concentration. By use of [14C]-labelled polyethylene glycol it was found that polyethylene glycols did not form stable complexes with immune complexes. Furthermore, it was found that the zoning phenomenon was retained in the presence of small concentrations of polyethylene glycols, but higher concentrations of polyethylene glycols caused even antigen-excess complexes to show turbidity.

Alcohols↗
PubMed1979

Dansylation of human serum albumin in the study of the primary binding sites of bilirubin and L-tryptophan.

Binding of bilirubin and of L-tryptophan to dansylated albumins was investigated. Dansylation of less than one lysine residue per molecule of albumin did not affect the bilirubin binding, but decreased the L-tryptophan binding, indicating that dansylation had taken place in or near the l-tryptophan-binding site. Native albumin and albumin-bilirubin 1:1 complex showed the same affinity for L-tryptophan. The results indicate that, although L-tryptophan and bilirubin are bound in the same region, perhaps in a common cavity of the albumin molecule, such a cavity is sufficiently large to contain both ligands.

Bilirubin↗
PubMed1979

A new gradient former and a simplified procedure for zonal centrifugation of immune complexes.

A new gradient former for production of optimized sucrose gradients for B-XIV zonal rotors is described. Optimized gradients are gradients with an initial shelf to provide capacity and a shape that ensures isokinetic sedimentation conditions. By exhaustive computer calculations it has been found that optimized gradients can be produced by a very simple two-compartment gradient former. The design is given. Moreover, graphs for choice of gradient strength and run duration for preparative and analytical runs of samples containing soluble immune complexes are calculated. The new gradient former allows the use of a very simple procedure for zonal centrifugation.

Antigen-Antibody Complex↗
PubMed1979

On the composition of IgG anti-IgG immune complexes.

The formation of different immune complexes of IgG was followed in a system comprising human IgG as antigen and rabbit IgG directed against the Fc portion of human IgG as antibody. Soluble IgG complexes were analyzed by analytical zonal centrifugation. In antigen excess, 16S complexes predominated. 16S complexes are oligomers of IgG, mainly trimers and tetramers. In decreasing antigen excess larger and larger complexes were formed. It was, however, found consistently that oligomers were always formed in the largest amounts. The largest complexes detectable by this method consisted of about twenty IgG molecules. The solubility of different complexes in polyethylene glycol was also studied. Low concentrations of polyethylene glycol preferentially precipitate large complexes. Four and six per cent polyethylene glycol precipitated all types of IgG complexes although not completely. Polyethylene glycol was seemingly not bound directly to soluble immune complexes, but caued otherwise soluble complexes to precipitate by an indirect mechanism.

Animals↗
PubMed1979

Measurements of precipitin reactions by difference turbidimetry: a new method.

A new method for the measurement of precipitin and flocculation reactions between antibodies and antigens has been developed. The technique, called difference turbidimetry, involves the use of tandem cuvettes providing the opportunity of using separated and unmixed antigen and antibody as blank solutions for spectrophotometric readings in the ultraviolet wavelength range. By use of this technique genuine difference turbidity spectra have been recorded for the reaction between human serum albumin and rabbit-anti-human serum albumin IgG. It was found that difference turbidimetry at low wavelengths (e.g. 280 nm) allows the construction of precipitin curves with a very clearly expressed zoning phenomenon at a sensitivity which in terms of antigen and antibody concentrations is more than twice the sensitivity of conventional procedures. It is of special interest that the zone of equivalence differs when the same reaction between an antigen and its antibody is measured by difference turbidimetry, by absorbance of washed and redissolved precipitate, and by amount of precipitated antigen.

Antigen-Antibody Reactions↗
PubMed1978

Lysine residue 240 of human serum albumin is involved in high-affinity binding of bilirubin.

Bilirubin can be coupled covalently to albumin by using water-soluble carbodi-imide as coupling reagent. The optimal specificity in the attachment of bilirubin to the high-affinity site on the albumin molecule was obtained by treating an albumin-bilirubin complex with carbodi-imide in low concentrations and for a short period. The product was reduced, carboxymethylated and digested with trypsin. By fractionation on Sephadex G-50 (superfine grade) a peptide fraction containing most of the bilirubin label was isolated. Further purification by paper chromatography gave one peptide, consisting of residues 240-258. The peptide containined a single lysine residue, 240, and had an intact disulphide bridge. The results indicate that bilirubin is bound to lysine residue 240 at its high-affinity site on human serum albumin.

Amino Acids↗
PubMed1978

On the mechanism of p-piperidyl and p-benzyl sulfamyl benzoic acids transport by renal tissue.

The uptake of cyclic analogues of probenecid by kidney cortical slices has been studied in detail, in order to obtain more information on the secretory system for these compounds. Both p-piperidyl sulfamyl benzoic acid and p-benzyl sulfamyl benzoic acid were accumulated against concentration gradient, by renal tissue under aerobic as well as anerobic conditions. PAH, phenol red and probenecid competitively inhibited the active accumulation of these compounds by kidney tissue. Aerobic uptake of probenecid analogues was stimulated by succinate and octanoate at low medium concentrations while inhibition of renal accumulation of these compounds occurred at higher concentrations. Both p-piperidyl and p-benzyl sulfamyl benzoic acids like probenecid strongly interact with kidney cortex homogenates. Binding of these cyclic analogues to various cellular constituents of homogenate was efficiently inhibited by probenecid. The binding affinity of probenecid and analogues for kidney tissue, phospholipid vesicles (liposomes) and human serum albumin increased in the order : p-piperidyl sulfamyl benzoic acid less than p-benzyl sulfamyl benzoic acid less than di-n-propyl sulfamyl benzoic acid (probenecid). By contrast to the view put forward by Beyer (1950 & 1954), the results presented in this paper established that probenecid analogues are the true substrates of renal organic anion transport system.

Biological Transport↗
PubMed1976

Covalent coupling of bilirubin to albumin.

A method for covalent coupling of bilirubin to albumin is described. Human serum albumin-bilirubin (1:1 complex) has been treated with water soluble carbodiimide in order to obtain covalent coupling of bilirubin to albumin. The reaction conditions have been varied with respect to pH, reaction time and concentration of reagent to obtain the optimal coupling. The prepared albumin-bilirubin compounds were investigated by spectrophotometry, gel filtration and gel electrophoresis to ascertain the covalent nature of the bond and to characterize the products further. Gel electrophoresis and gel filtration showed that a monomer fraction could be prepared, and this fraction was a suitable material for further studies.

Bilirubin↗
PubMed1975

Trinitrophenylation of the bilirubin binding site of human serum albumin.

Human serum albumin has been modified with 2,4,6-trinitrobenzenesulphonic acid and picryl chloride in low ratios of reagents/albumin. The derivatives have been investigated by spectrophotometry and by thin layer chromatography of the hydrolysates in order to assess the specificity of the reagents. The same reaction conditions were used to modify albumin previously complexed with bilirubin in the ratio of 1:1. The affinity of bilirubin to the modified albumins was estimated by an improved perozidase method. It is concluded that TNBS and picryl chloride react almost quantity with epsilon-amino groups of lysine on the albumin molecule. The results also suggest that at least on TNBS reactive amino group and at least one picryl chloride reactive amino group are located in or near the high-affinity bilirubin binding site.

Absorption↗
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

Spontaneous toxic nephropathy in poultry associated with ochratoxin A.

At a poultry slaughterhouse 14 birds with macroscopic renal changes were collected, and the kidneys were examined histologically and the muscular tissue was analysed for ochratoxin A residues. Out of 14 birds 5 birds had ochratoxin A residues ranging from 4.3 to 29.2 mug/kg. In 4 of these birds a toxic nephropathy was found characterised by atrophy and degeneration of proximal and distal tubules and interstitial fibrosis. The possibility of birds with ochratoxin A residues being presented for human consumption is discussed.

Animals↗