Effect of a contaminating competitive ligand on ligand-hinding curves inverse protein concentration dependence

ATP-dependent Ca uptake by rat myometrium plasma membrane fraction occurs only in the presence of magnesium. Studies of the membrane protein-concentration dependence of the ATP-dependent Ca uptake showed that at 33 micrograms protein/ml the uptake increased linearly with time up to 2 min and deviated from linearity at longer times. Studies of the Ca2+ concentration dependence of initial Ca-uptake velocity (reaction time 2 min) of the uptake reaction showed that 1) ATP-dependent Ca uptake increased with increasing Ca2+ concentration from 0.1 to 1 microM, and a further increase in Ca2+ concentration above 1 microM did not enhance the uptake further and 2) the Ca-uptake dependence on Ca2+ concentration was nonhyperbolic with a Hill coefficient of 1.3–1.7 and half saturation occurring at 0.4–0.5 microM Ca2+. These data suggest that the ATP-dependent Ca movement by rat myometrium plasma membranes may play a very important role in smooth muscle relaxation. Physiological implications of the nonhyperbolic kinetics are also discussed.

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Contamination by a competitive ligand as an explanation for the inverse dependence of haba binding parameters upon the protein concentration

Biochemical Pharmacology ◽

10.1016/0006-2952(89)90118-4 ◽

1989 ◽

Vol 38 (20) ◽

pp. 3485-3490 ◽

Cited By ~ 6

Author(s):

J.Boiden Pedersen ◽

Susanne Møller Pedersen ◽

W.Edward Lindup

Keyword(s):

Protein Concentration ◽

Binding Parameters ◽

Competitive Ligand

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Characteristic Changes in the Density and Shear Viscosity of Human Blood Plasma with Varying Protein Concentration

Ukrainian Journal of Physics ◽

10.15407/ujpe65.2.151 ◽

2020 ◽

Vol 65 (2) ◽

pp. 151 ◽

Cited By ~ 3

Author(s):

N. P. Malomuzh ◽

L. A. Bulavin ◽

V. Ya. Gotsulskyi ◽

A. A. Guslisty

Keyword(s):

Aqueous Solution ◽

Blood Plasma ◽

Concentration Dependence ◽

Shear Viscosity ◽

Human Blood ◽

Protein Concentration ◽

Structural Transformations ◽

Blood Substitutes ◽

Human Blood Plasma ◽

Initial Value

The density and shear viscosity of human blood plasma and their dependence on the concentration of proteins (albumin, y-globulin, fibrinogen, etc.) entering the natural blood composition have been studied. The biomaterial concentration is varied by diluting the blood plasma with the isotonic aqueous solution. It is shown that a decrease in the biomaterial concentration down to 0.91 of its initial value leads to a drastic change in the plasma density and to a change in the character of the concentration dependence of the shear viscosity of blood plasma. A hypothesis is put forward that the observed changes in the density and shear viscosity result from the structural transformations induced by oligomerization processes; first of all, by the albumin dimerization. A conclusion is drawn that the introduced blood substitutes should not exceed 10% of the blood mass; otherwise, structural transformations of a biomaterial in blood plasma can be provoked.

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