The Investigation Of Interaction Competition Between Atp And Dipp-Ala, Boc-Ala, Or Ala By Esi-Ms/Ms And Theoretical Calculation

The interactions between ATP and N-(O,O-diisopropyl) phosphoryl-L-alanine (DIPP-Ala), N-(tert-butoxycarbonyl)-L-alanine (Boc-Ala), or L-alanine (Ala) were investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The non-covalent complexes between ATP and Boc-Ala or DIPP-Ala were observed, while the complex between ATP and Ala was not found in the mass spectra. The affinity of DIPP-Ala for ATP was confirmed to be stronger than that of Boc-Ala by competition experiment. Through molecular modeling calculations, it was found that the non-covalent complexes were stabilized by intermolecular hydrogen bonds, and the affinity sequence for ATP was DIPP-Ala Boc-Ala Ala by comparing their binding energy, -35.407 kcal/mol, -15.634 kcal/mol, -6.555 kcal/mol, respectively. The results implied that a phosphoryl group was a very important functional group to provide an interaction site between amino acids and ATP, and that N-phosphoryl amino acids can be used as a good model of protein in the studies of molecular recognition of ATP.