Influence of liposome charge and composition on their interaction with human blood serum proteins |
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Authors: | Trinidad Hernández-Caselles José Villalaín Juan C Gómez-Fernández |
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Institution: | (1) Department of Physiology MCV Station, Medical College of Virginia, Virginia Commonwealth University, Box 551, 23298-0551 Richmond, Viginia, USA;(2) Department of Pharmacology & Toxicology MCV Station, Medical College of Virginia, Virginia Commonwealth University, Box 551, 23298-0551 Richmond, Viginia, USA |
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Abstract: | The roles of sulfhydryl and disulfide groups in the specific binding of synthetic cannabinoid CP-55,940 to the cannabinoid receptor in membrane preparations from the rat cerebral cortex have been examined. Various sulfhydryl blocking reagents including p-chloromercuribenzoic acid (p-CMB), N-ethylmaleimide (NEM), o-iodosobenzoic acid (o-ISB), and methyl methanethiosulfonate (MMTS) inhibited the specific binding of 3H]CP-55,940 to the cannabinoid receptor in a dose-dependent manner. About 80–95% inhibition was obtained at a 0.1 mM concentration of these reagents. Scatchard analysis of saturation experiments indicates that most of these sulfhydryl modifying reagents reduce both the binding affinity (Kd) and capacity (Bmax). On the other hand, DL-dithiothreitol (DTT), a disulfide reducing agent, also irreversibly inhibited the specific binding of 3H]CP-55,940 to the receptor and about 50% inhibition was obtained at a 5 mM concentration. Furthermore, 5mM DTT was abelt to dissociate 50% of the bound ligand from the ligand-receptor complex. The marked inhibition of 3H]CP-55,940 binding by sulfhydryl reagents suggests that at least one free sulfhydryl group is essential to the binding of the ligand to the receptor. In addition, the inhibition of the binding by DTT implies that besides free sulfhydryl group(s), the integrity of a disulfide bridge is also important for 3H]CP-55,940 binding to the cannabinoid receptor. |
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Keywords: | sulfhydryl group disulfide group cannabinoid receptor rat cerebral cortex |
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