Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 26: Posters II

BP 26.14: Poster

Thursday, February 28, 2008, 17:00–19:30, Poster A

Magnetic Relaxation Dispersions of Biomolecules: Effects of Field-Cycling — •Talea Köchling, Konstantin Ivanov, Sergey Korchak, Alexandra Yurkovskaya, and Hans-Martin Vieth — Institute für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany

The dynamics of biomolecules is reflected in the spin-lattice relaxation times T1 of individual nuclei. From the change of T1 at variation of the external magnetic field intramolecular mobility can be determined. Combining a field-cycling unit, which shuttles the NMR probe along the bore axis of the spectrometer cyromagnet, with high resolution NMR spectroscopy we are able to measure T1 of individual nuclei between 1 uT and 7 T. Our experiments show that such relaxation dispersion is strongly affected by scalar couplings among the spins. Spins having substantially different T1 at high field relax at low field with a common T1 due to strong coupling. Furthermore peaks or dips are seen at fields corresponding to crossings of spin levels. An adequate theoretical approach to modelling the dispersion curve and extracting motional parameters is presented and experiments on amino acids and peptides (for example, tyrosine and enkephalin) are discussed. It shows that for proper interpretation of relaxation dispersion curves scalar couplings must be taken into account as long as 1/J<T1.