Longitudinal nuclear relaxation of an ABX spin system application to a13C–13C–1H fragment with and without proton irradiation

摘要

The longitudinal relaxation and the nuclear Overhauser enhancement, relative to theAandBtransitions of an ABX spin system, are studied theoretically. A complete treatment based on density tion ofXtransitions. Assuming a doubly enriched fragment of the type O=13CA–13CB–1Hkhgr;, numerical simulations have been performed with the aim to study the effects of cross‐correlation spectral densities and motional anistropy. For the example considered, the initial slopes of carbonyl lines recovery curves yield a wealth of information. This interesting behavior arises from mixing effects produced by the observing pulse. The other data (recovery curves and NOE factors) can be, to a good approximation, interpreted in terms of generalized Solomon equations. These latter conclusions are however valid regarding the geometry of the considered fragment and, in the general case, cross‐correlation terms must be taken into account.