4 aminophenylarsine oxide Arsenic Arsenic carcinogenesis Arsenicals Carrier Proteins Circular dichroism Conformational studies Drug delivery systems Fluorescein-5-isothiocyanate Fluorescent Dyes Kinetics Models, Molecular Protein Binding Protein Conformation Protein Unfolding Spectrum Analysis Temperature Thioredoxin Thioredoxins arsenic arsenic binding protein article atomic absorption binding protein circular dichroism enzyme activity fluorescein isothiocyanate fluorescence fluorescent dye polyacrylamide gel electrophoresis