Biomaterial Database

Influence of pH on the binding of suramin to human serum albumin. 1989

E L Vansterkenburg, and J Wilting, and L H Janssen

Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Utrecht, The Netherlands.

The pH dependence of the binding of suramin to albumin has been studied by means of equilibrium dialysis and circular dichroism. Dialysis experiments have revealed that the association constants of the high and low affinity binding sites are strongly influenced by the pH. At pH 6.0 K1 = 1.4 x 10(6) M-1/n1 = 2.0 and K2 = 1.3 x 10(5) M-1/n2 = 1.0; at pH 9.2 K1 = 2.0 x 10(5) M-1/n1 = 2.0. At the high pH no low affinity sites could be demonstrated any more. The pH dependence of the induced ellipticity of the suramin-albumin complex at low molar drug-to-protein ratio r = 0.1 can be superimposed upon the neutral-to-base (N-B) transition of albumin alone. By means of the Linderstrøm-Lang equation for electrostatic interaction and a two-state model for the N-B transition of albumin, evidence is obtained of a link of the pH dependent binding behaviour of suramin to albumin and the neutral-to-base transition of albumin. The possible correlation of this link with transport processes of suramin in the body and with selective uptake of suramin in cells and parasites is discussed.

UI	MeSH Term	Description	Entries
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D002942	Circular Dichroism	A change from planar to elliptic polarization when an initially plane-polarized light wave traverses an optically active medium. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Circular Dichroism, Vibrational,Dichroism, Circular,Vibrational Circular Dichroism
D003956	Dialysis	A process of selective diffusion through a membrane. It is usually used to separate low-molecular-weight solutes which diffuse through the membrane from the colloidal and high-molecular-weight solutes which do not. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Dialyses
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D012709	Serum Albumin	A major protein in the BLOOD. It is important in maintaining the colloidal osmotic pressure and transporting large organic molecules.	Plasma Albumin,Albumin, Serum
D013498	Suramin	A polyanionic compound with an unknown mechanism of action. It is used parenterally in the treatment of African trypanosomiasis and it has been used clinically with diethylcarbamazine to kill the adult Onchocerca. (From AMA Drug Evaluations Annual, 1992, p1643) It has also been shown to have potent antineoplastic properties.	Germanin,Moranil,Naganin,Naganol,Naphuride,Suramin Sodium,Suramin, Hexasodium Salt,Suramin, Monosodium Salt,Hexasodium Salt Suramin,Monosodium Salt Suramin,Salt Suramin, Hexasodium,Salt Suramin, Monosodium,Sodium, Suramin