Radiation damping transfer in nuclear magnetic resonance experiments via chemical exchange

Publisher Website
Google Scholar
Abstract
In nuclear magnetic resonance(NMR) experiments on samples containing biomolecules(proteins, polypeptides, and nucleic acids), chemical exchange between the biomolecular NH protons and water influences NMR measurements in many aspects, and it is necessary to know the exchange rate constants. However, because the exchanging system usually consists of weak NH signals and a strong water resonance that is undergoing radiation damping, it is difficult to quantitatively study the exchange dynamics using established methods. We suggest a new approach, called radiation damping transfer method, for studying the exchange dynamics, which takes advantage of radiation damping of water. When the radiation damping effect is transferred from water to the mobile NH protons through chemical exchange, the exchange rate constants can be quantitatively evaluated. In this paper, the Bloch equations modified by both radiation damping and chemical exchange are solved. Radiation damping transfer effects are discussed. The new method is demonstrated by an example through analysis of the inversion-recovery data that are strongly influenced by radiation damping transfer.