Studies on Interaction of Adenosine-5'-monophosphate with Cu-chlorophyllin by Means of Paramagnetic Effects on ¹H and ¹³C Relaxation Rates

Abstract

The structure of Cu-chlorophyllin (Cu-chin) denosine-5'-monophosphate (5'-AMP) complex was studied. This complex has the absorption band at 645 nm which is attributed to the complex formation. From the titration of the difference spectra of the complex, its binding number and binding constant were estimated to be about 1 and 11.3 //mot at 25° C, respectively. Because the effect of Cu-chin on T1 of water protons decreases to a quarter, it was considered that Cu-chin forms dimer at higher concentration than 1 mmol/l in solution, From the low temperature ESR spectrum of the complex which has no hyperfine splitting, it is clear that the dimer of Cu-chin does not dissociate upon addition of 5'-AMP. Cu-chin also showed remarkable paramagnetic effects on proton and carbon relaxation rates of 5'-AMP. The longitudinal (T₁) and transverse (T₂) relaxation times of Cu-chln-5'-AMP complex were determined. From the data of temperature dependence of T2, it is considered that H(1') is relaxed with dipole-dipole interaction, but H(8) and H(2) are relaxed with the scalar interaction. The T₁ values for the complex have a minimum at about 20° C and r is considered to be 1.6x 10^-9 sec at this temperature. With the minimum value of T1, the apparent distances between each proton of 5'-AMP and the electron spin were 7.1 A, 6.9 A, and 7.4 A for H(8), H(2), and H(1'), respectively, by the equation of Bloembergen. The distances between each carbon of 5'-AMP and the electron spin were also calculated (Table 2).