An interaction of the functionalized closo-borates with albumins: The protein fluorescence quenching and calorimetry study

An interaction of the boron clusters closo -borates K 2 [B 10 H 10 ], K 2 [B 12 H 12 ] and their functionalized derivatives with serum proteins human (HSA) and bovine (BSA) albumins and immonoglobulin IgG as well as globular proteins β-lactoglobulin and lysozyme was characterized. The steady state and time resolved protein fluorescence quenching studies point on the binding of the closo -borate arylamine derivatives to serum albumins and discrimination of other proteins. The mechanism of the albumin fluorescence quenching by the closo -borate arylamine derivatives was proposed. The complex formation between albumin and the closo -borate molecules has been confirmed by isothermal titration calorimetry (ITC). The compound (K 2 [B 10 H 10 ]) and its arylamine derivative both interact with HSA, have close values of K a (1.4 and 1.2×10 3  M −1 respectively) and Gibbs energy (−17.9 and −17.5 kJ/mol respectively). However, the arylamine derivative forms complex with the higher guest/host binding ratio (4:1) comparing to the parent closo -borate (2:1).