ポリ(リボウリジル酸)とMn²⁺の相互作用の核磁気緩和による研究

抄録

T_1s of protons of poly(ribouridylic acid) (poly(U)) were reduced by an addition of Mn²⁺. This phenomenon is considered to be caused by the dipole-dipole interaction between the proton and the electron spin of Mn²⁺. T₁ minima were obtained from the temperature dependence of T₁ of the complex, and the apparent distances between Mn²⁺ and the protons of poly(U) wer e estimated by substituting 1.59×10^-9 s of which value is estimated from the relation that τ^c equals ω_I^-1. But if Mn²⁺ is assumed to bind to N(3), these estimated distances are longer than those which are estimated from Mn²⁺-proton distances presumed from the Dreiding model by the Bloembergen equation. The reason for this result is considered that a part of Mn²⁺ which binds to phosphate group chelates to N(3). It was found that O.28 of Mn2+binds to N(3) from the ratio of T₁ estimated from the Dreiding model to T₁ observed.
τ^c of Mn²⁺-poly(U) complex at each temperature was eatimated from the: ratio of T₁ at each temperature to T₁ minimum. The comparison of these values with the τ^c of poly(U), which is obtained in the absence of Mn²⁺, indicates that the motion of poly(U) becomes slower in the presence of Mn²⁺ than in the absence of Mn²⁺.