research

SSNMR requires coherent integration of technical and fundamental advances. Our specific applications to hydrated protein samples require high resolution and sensitivity, optimal performance of multiple-pulse sequences and long-term instrumental stability. Therefore our contributions start with instrumentation and pulse sequence methods. We have collaborated with Varian, Inc., in order to upgrade spectrometers at UIUC. In configuring 500, 600 and 750 MHz instruments at UIUC, we thoroughly addressed both routine technical issues—such as long-term variable temperature performance, amplifier stability, magnet drift and homogeneity—as well as fundamental advances. In the latter category, among the most notable are optimal resonator designs (both variable pitch, balanced solenoids and scroll resonators (Stringer et al., J. Magn. Reson. 2005)) that have three important properties: superior B₁ homogeneity, greatly reduced dielectric sample heating and improved sensitivity for ¹H-detection experiments on protein samples. These probes have been key for applying multidimensional recoupling experiments to proteins in all our projects, but especially for quantitative dipolar (Franks et al., JACS 2006) and chemical shift lineshape (Wylie et al., JACS 2005, JPC B 2006) and sideband analysis (Wylie et al., JACS 2007), proton detection (Zhou et al., JMR 2006, JACS 2007, Angew. Chem. 2007, in press) and studies of membrane proteins at high field. (Frericks et al., J. Biomol. NMR 2006; Li et al., Biophys. J. 2006, ChemBioChem 2007; Kijac et al., unpublished). Academic laboratories and commercial vendors continue to develop this probe technology further, resulting in a range of new applications for both MAS and static SSNMR that have benefited the community as a whole.