The interaction of vanadyl ions with gliadin by spectrophotometric and Ph-metric methods

The interaction of vanadyl ion with gliadin has also been studied by spectrophotometric and pH-metric methods. The nature of spectra of small ligands and liquid-polymer solution provides sufficient information about ligand-polymer interaction. Here, addition of only 0.57 × 10-4 M protein solution caused on increase in absence at a particular wavelengths. The solulder as well as the maximum absorption band becomes highly flattened but remains on the same wavelengths as that of vanadyl ion alone. This shift of spectrum is a direct indication of vanadyl ions with reactive sites of protein. The results show that the λmax value for vanadyl-ion alone remains constant throughout the whole pH-range, while in case of vanadyl-protein system, it remains same upto pH 4.27 and then becomes 10nm more at pH 4.45. The change in λmax at pH 4.45 indicates binding as compared to other pH values. The sudden decrease in the value of extinction coefficient of vanadyl ion (ε) in presence of even a small amount of protein indicates involvement of carboxyl group of protein in metal-cation linkage. Continuous pHtitrations were also carried out which also indicate the interaction of vanadyl cation with anion group of gliadin.