Intralenticular water interactions with phosphates in the intact crystalline lens

Since the ATP molecule is associated with the intracellular milieu, which consists mainly of water, this study suggests an intimate intracellular association with water molecules. Intact canine crystalline lenses (n = 6) were incubated at 37 degrees C in a buffer containing a pure D2O solvent and examined by [31P]-nuclear magnetic resonance (NMR) spectroscopy. Control lenses (n = 6) from contralateral eyes were incubated in a pure H2O-based buffer. During the first 4 h of a 24-hour incubation, the D2O-incubated lens maintained its phosphorus metabolic profile, indicating that the tissue maintains its metabolic health. During this period, however, the spectral signal widths of ATP narrowed progressively. Spectral-simulation analysis of ATP alpha-, beta- and gamma-phosphate signals revealed that the gamma-phosphate signal was narrowed significantly in contrast to the alpha-phosphate signal. Such differential signal narrowing within a single NMR spectrum indicates that the principal intracellular site of water hydrogen binding to the ATP molecule is at the gamma-group phosphate.