Kinetics of membrane binding and dissociation of 5-fluorouracil by pulsed-field-gradient 19F NMR

The kinetics of membrane binding and dissociation of an anticancer drug, 5-fluorouracil (5FU) is quantified by high resolution NMR with the pulsed-field-gradient technique. The 19F NMR signal of 5FU is analyzed at 293–313 K by the solution of Bloch equation with exchange terms. The rate constants of 5FU binding and dissociation are 0.2 and 4.1 s−1 at 303 K. The 5FU motion in the vertical direction to the membrane surface is restricted as compared with the lateral diffusion, judging from the activation energy (57 kJ/mol) larger than the lateral diffusion in membrane (26 kJ/mol [E. Okamura, N. Yoshii, J. Chem. Phys. 129 (2008) 215102]).