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Biomedical subjects

A Oplatka

Publications and source records attributed to A Oplatka.

At least 55 records · Page 3Linked to original sources
PubMed1975

Dynamic affinity chromatography of heavy meromyosin subfragment-1.

Heavy meromyosin subfragment-1 and its trinitrophenylated derivative have been chromatographed on immobilized ATP, ADP and adenosine 5'-(geta, gamma-imino) triphosphate affinity chromatography columns, in the presence and in the absence of Ng-2+ or Ca-2+.ma-32-P] ATP columns. While the divalent cations had little effect on the chromatographic pattern in the case of the non-hydrolyzable ADP and adenosine 5' (beta, gamma-imino) triphosphate, they catalyzed splitting in the case of ATP and at the same time strongly increased the affinity of adsorption of the proteins. The protein-elution and the Pi-release patterns were different for the native and the modified proteins. These results have been interpreted in terms of protein binding to the various intermediates of the ATP hydrolysis reaction.

Adenosine Diphosphate↗
PubMed1975

Identical behavior of the two active sites of myosin with respect to trinitrophenylation.

Myosin and its active subfragments were trinitrophenylated under conditions in which mainly the active site(s) was modified. Proteins modified at the active site(s) could be separated by affinity chromatography on agarose-ATP columns. By two independent methods, ATPase activity measurements and analysis of elution patterns on agarose-ATP columns, it was shown that the introduction of two trinitrophenyl groups per myosin or one per heavy meromyosin subfragment 1 molecule is responsible for the remarkable change in the ATPase activities. Heavy meromyosin subfragment 1 prepared from trinitrophenylated myosin retained the original degree of trinitrophenylation per "active head." The kinetic constant of trinitrophenylation of the epsilon-amino group of lysine at the active site was found to be 2000 S-1-M-1, whereas a much smaller constant of 2.2 S-1-M-1 was obtained for the trinitrophenylation of the unessential lysyl residues of myosin. By using affinity chromatography, we could follow the formation of mono- and ditrinitrophenyl myosin. The amounts of these myosin derivatives at various extents of the reaction corresponded approximately to the calculated amounts, assuming a random and independent trinitrophenylation of the two myosin "heads." It is concluded that in each of the two heads of myosin there is one ATPase active site and these two sites behave in an identical manner with respect to trinitrophenylation.

Adenosine Triphosphatases↗
PubMed1975

Fibrin-blood platelet interaction in a contracting clot.

The interaction of fibrin and blood platelets was studied by measuring tension development in clots containing different ratios of these two components. Isometric tension attained a saturation value (MT) when plotted as a function of the concentration of either component at a constant concentration of the other. The value of MT increases linearly with the minimal platelet concentration (Ps) required in order to reach saturation at various different fibrin concentrations. A linear relationship also holds in a plot of Ps versus the logarithm of the corresponding fibrin concentration. When the cylindrical clots contracted isotonically, the velocity, normalized with respect to the momentary length, was found to be constant. This velocity decreased in an hyperbolic manner with increasing fibrin concentration at a constant concentration of blood platelets. The results are interpreted in terms of a three-dimensional network in which the blood platelets serve as contractile cross-bridges connecting fibrin fibres. Tension development is assumed to be accompanied by the reduction of the angle between fibrin fibres. An attempt was made to calculate the isometric tension developed by a platelet.

Blood Coagulation↗