A theoretical study on the structural and functional features of BSH Agent used in boron neutron capture therapy

The theoretical studies on B12H11SH2− (BSH), B24H22S24− (BSSB) and B12H11S2− (BS) were carried out using the density functional theory (DFT) method. The calculations supported the experimental observations that BSH may be oxidized to form dimer BSSB; the dimeric structure readily undergoes homolytic cleavage, under acidic conditions, generating a free radical BS. Atomic population analyses indicated that the redox reactions proceed through intramolecular electronic transfer. Analyses of the frontier orbitals revealed that sulfur atom is an active site of the complexes, and BS is the reactive species among BSH, BSSB, and BS. The investigation of mechanism of the reaction BS+S2(CH3)2 verified that the active BS can attack the disulfide bond of the specific protein. It seem that BS is responsible for enhancement of the content of 10B atom in the tumor for boron neutron capture therapy (BNCT).