The effect of serum albumin, surfactant and their mixture on the reduction of a cobalt(III) complex by ascorbic acid

•Interactions of ascorbic acid, CTAB and a CoIII-complex have been identified by conductometric, CD and kinetic experiments.•Ascorbic acid binds with BSA and brings significant changes in the secondary and tertiary structures of the protein.•CTAB binds extensively with BSA and destroys its super coiled structure.•Interactions of ascorbic acid and CTAB with BSA influence the reduction rate of a CoIII complex by ascorbic acid.

Kinetic investigations on the reduction of CoIII-complex by a biologically active antioxidant molecule, ascorbic acid in a buffer medium of pH 9.0 have been performed using spectroscopic techniques. The reaction has been carried out in presence of a protein, bovine serum albumin (BSA), n-cetyltrimethylammonium bromide (CTAB) and their mixtures. The reaction rate changes remarkably on addition of protein. Unlike the complex, experimental results depict extensive binding of detergent and ascorbate anions with BSA. Both native and cooperative binding have been observed for CTAB–BSA interaction. But only native binding at specific binding sites have been observed for ascorbic acid–BSA interaction. The reactant molecules prefer to bind with domain I and III over II of the BSA molecules. Denaturing action of urea releases the protein bound ascorbates into bulk. The experimental findings have been further verified from the conductometric and circular dichroism studies.

Graphical abstractAscorbic acid and CTAB bind with BSA and change the reduction rate of a CoIII complex by ascorbic acid.Figure optionsDownload full-size imageDownload as PowerPoint slide