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Biomedical subjects

B R Andersen

Publications and source records attributed to B R Andersen.

At least 91 records · Page 5Linked to original sources
PubMed1971

Streptolysin O II. Relationship of Sulfyhdryl Groups to Activity.

Streptolysin O (SO), a group A streptococcal toxin, exists in two forms, a reduced active state and an oxidized reversibly inactive state. Activity is measured by red blood cell hemolysis. SO is a labile toxin, and, with time, activity is irreversibly lost. The rate of activity loss is slowed by incubation with 0.1 m 2-mercaptoethanol or 0.01 m ethylenediaminetetraacetic acid (EDTA). The effect of EDTA can be reversed by excess MgSO(4). Reversibly oxidized SO is activated by cleavage of disulfide bonds. When the free sulfhydryl groups of the active SO are alkylated with iodoacetamide, complete and irreversible loss of activity results. Periodate (0.01 m) oxidation also causes complete loss of activity which may be due to oxidation of sulfhydryl groups. SO in the active form reacts with Fe(2+), Cu(2+), Ca(2+), and Mg(2+), causing loss of activity in various degrees depending on the ions and the concentration used. Ferric and cupric ions are most effective and cause loss of activity at concentrations on the order of 10(-4)m. The reversibly oxidized form of SO is not influenced by exposure to cupric ions (0.01 m), indicating that the reaction is only with the active form of SO, probably involving the free sulfhydryl groups. These groups may be responsible for the direct binding of the toxin to the target membrane or for the maintenance of the proper conformation for activity.

Journal Article↗
PubMed1969

Streptolysin O: sedimentation coefficient and molecular weight determinations.

The sedimentation coefficient of streptolysin O as determined by sucrose density gradient ultracentrifugation is 3.7S. An approximate molecular weight of 60,500 was calculated from the sedimentation velocity, and a similar value was obtained by Sephadex gel filtration. There was no measurable difference in the sedimentation coefficient of streptolysin O in either the active or reversibly inactive forms, indicating that there were at most only minor conformational differences between the two forms.

Centrifugation, Density Gradient↗
PubMed1966

Gamma-A cold agglutinin: importance of disulfide bonds in activity and structure.

Cleavage of disulfide bonds caused by mild reduction with mercaptoethanol produces a reversible loss of cold agglutinin activity and antigen-binding ability in a gamma-A polymer cold agglutinin. Return of agglutination and antigen-binding ability occur only in those molecules that have not been depolyimerized by reduction. Loss of activity becomes irreversible if reduction is followed immediately by alkylation.

Amides↗