Hyperpolarized long-lived states in solution NMR: three-spin case study in low field

J Magn Reson. 2008 Sep;194(1):46-57. doi: 10.1016/j.jmr.2008.05.027. Epub 2008 Jun 4.

Abstract

Recent work has shown that singlet states in two-spin systems can possess lifetimes exceeding the T(1) relaxation time, provided that the system is kept under conditions that minimize the effects of the chemical shift Hamiltonian (for instance under low magnetic field or RF irradiation). Similar observations have been made in hyperpolarized states of multi-spin systems prepared via parahydrogen-induced polarization (PHIP). However, lifetime prolongation mechanisms in multi-spin systems are still under investigation. Here we present experimental observations of a long-lived state in a three-spin system prepared by PHIP and stored at low field. The observed lifetime of the long-lived state is 144s, about twice as long as the longest T(1) measured in the system at high field. The results are analyzed using a recently proposed theory of lifetime prolongation in multi-spin systems in low field. It is shown that quantum mechanical selection rules governing intramolecular dipolar relaxation in low field account for the enhanced lifetime and spectral features of this state.

MeSH terms

  • Algorithms*
  • Computer Simulation
  • Electromagnetic Fields
  • Hydrogen / analysis*
  • Hydrogen / chemistry*
  • Magnetic Resonance Spectroscopy / methods*
  • Models, Chemical*
  • Solutions
  • Spin Labels

Substances

  • Solutions
  • Spin Labels
  • Hydrogen