Photochemical release of ATP from "caged ATP" studied by time-resolved infrared spectroscopy

Article abstract of DOI:10.1021/ja00146a015

Rapid scan Fourier transform infrared (FTIR) spectroscopy and time-resolved single wavelength infrared (IR) spectroscopy have been used to follow the photochemical release of adenosine 5′-triphosphate (ATP) from P³-(1-(2-nitrophenyl)ethyl) adenosine 5′-triphosphate (caged ATP). Vibrational difference spectra for the formation first of the aci-nitro anion intermediate and subsequently of ATP and the byproduct(s) were obtained by rapid scan FTIR spectroscopy in the millisecond-to-second time domain. Vibrational modes of the phosphate groups of ATP and caged ATP in the range 1250-900 cm^-1 could be assigned on the basis of triple and single ¹⁸O labeling in caged ATP at the terminal phosphate group and at the bridging oxygen between the terminal phosphate and the 1-(2-nitrophenyl)ethyl group, respectively. The rapid formation and subsequent decay of the aci-nitro anion intermediate were monitored by single-wavelength time-resolved IR spectroscopy at 1251 cm^-1 (predominantly a PO₂^- mode of caged ATP and the aci-nitro intermediate). The appearance of the free γ-phosphate group of ATP was monitored at 1119 cm^-1 (POs^2- mode of ATP). Decay of the aci-nitro anion intermediate and formation of ATP were well fitted by single exponentials to give a mean rate constant of 218 ± 33 s^-1 at pH 7 and 22 °C.