protein nanocrystals

In order to obtain good results with biological macromolecules, sample preparation must be undertaken carefully. In order to make reliable assignments in uniformly ¹³C-¹⁵N labeled samples, the spectral resolution must be high enough to separate and assign resonances from many chemically similar labeled sites. Isotopically enriched protein samples for solid-state NMR can be prepared by direct synthesis for small peptides, or by recombinant expression in the case of larger proteins. With labeled samples, solid-state NMR can be used in methods analogous to their solution counterparts, in which most backbone and side chain ¹³C, ¹⁵N, and even ¹H resonances are correlated in multidimensional experiments as part of a structure determination. Solid-state NMR does not require the type of long-range order that is necessary for X-ray diffraction, allowing the sample preparation to be greatly simplified. Protein micro- or nanocrystals have sufficient local order to produce high-resolution solid-state NMR spectra. Relaxing the requirement for crystal quality greatly increases the number of proteins available for structure determination. In addition, smaller crystals may be more useful for chemical studies, since the ratio of surface area to volume is maximized. My research group will produce membrane proteins and their complexes and prepare nanocrystalline samples in order to extend structural and chemical analysis to interesting new systems.