orals 5th Asia-Pacific NMR Symposium 2013

Singlet-State NMR in Hydrogel Systems (#97)

Kaz Nagashima 1 , Krishina Rao 1 , Guilhem Pagès 1 , S. Sendhil Velan 1 , Philip W. Kuchel 2
  1. Singapore Bioimaging Consortium, A*STAR, 11 Biopolis Way, Singapore 138667
  2. School of Molecular Bioscience, University of Sydney, Sydney, New South Wales 2006, Australia

Existence of singlet spin states in the context of NMR, i.e., a nonmagnetic eigenstate formed by a pair of coupled spin-1/2 nuclei, has been recognized since the early 1970s [1]. The unobservable magnetization had not been scrutinized until 2004, when it was reported to yield a relaxation time that was longer than a longitudinal spin relaxation time T1 [2]. The limit of quantum coherences can be overcome through cancellation of intramolecular dipolar interactions by forcing two coupled magnetic vectors to align in opposite orientations and precess at the same rate. This so-called long-lived spin state has recently been studied actively in the forefront of NMR research, with expectations for rendering novel image contrast [3] and preserving hyperpolarized magnetizations [4]. We investigated long-lived spin states of small molecules within a stretchable gel; dipolar interactions of its constituents were manually adjustable. Two kinds of singlet-forming molecules were examined: para-hydroxybenzoic acid and Ala–Gly–Gly; each of them was dissolved in a hot gelatinous fluid and the gel was solidified in a flexible silicone tubing at room temperature. The stretched tubing was fixed within a 5 mm NMR tube and observed with a standard probehead. Diffusion rate, T1, and T2 of the probe molecules did not change even when the hydrogels were stretched and the probe molecules exhibited an anisotropic alignment.

  1. R.A. Hoffman, S. Forsén, G. Gestblom, Analysis of NMR Spectra, P. Diehl, E. Fluck, R. Kosfeld, Eds, NMR Basic Principles and Progress, Vol. 5, Springer-Verlag, Berlin, 1971, pp. 142.
  2. M. Carravetta, M.H. Levitt, Phys. Rev. Lett. 2004, 92, 153003.
  3. S.J. DeVience, R.L. Walsworth, M.S. Rosen, NMR Biomed. 2013, DOI: 10.1002/nbm.2936.
  4. G. Pileio, S. Bowen, C. Lausten, M.C.D. Tayler, J.T. Hill-Cousins, L.J. Brown, R.C.D. Brown, J.H. Arderkjaer-Larsen, M.H. Levitt, J. Am. Chem. Soc. 2013, 135, 5084.