ABSTRACT

The parameters that describe a 31P nuclear magnetic resonance (NMR) resonance are its chemical shift, scalar coupling constant(s), and T2 and T1 relaxation times. These are dependent upon the chemical structure of the phosphorus-containing compound. In order to understand the effects of protein binding upon the chemical shift of a phosphorus nucleus, one must have some appreciation of what factors determine the chemical shift. 31P spin-spin coupling constants arise from a through-bond interaction between the 31P nucleus and another nucleus, usually a proton or another 31P nucleus. The binding of a phosphorus-containing compound with a protein will almost always result in a decrease in the T2 (spin-spin) relaxation time of the 31P nucleus. This is seen as an increase in resonance linewidth for the protein-bound 31P resonance relative to that of the compound free in solution. A major contribution of 31P NMR in the area of protein-phosphorus interactions is in relation to the mobility of the 31P nucleus in the bound complex.