Partial NMR assignments for uniformly (C-13, N-15)-enriched BPTI in the solid state

We demonstrate that high-resolution multidimensional solid state NMR method s can be used to correlate many backbone and side chain chemical shifts for hydrated micro-crystalline U-C-13,N-15 Basic Pancreatic Trypsin Inhibitor (BPTI), using a field strength of 800 MHz for protons, magic angle sample s pinning rates of 20 kHz and proton decoupling field strengths of 140 kHz. R esults from two homonuclear transfer methods, radio frequency driven dipola r recoupling and spin diffusion, were compared. Typical C-13 peak line widt hs are 0.5 ppm, resulting in C alpha-C beta and C alpha-CO regions that exh ibit many resolved peaks. Two-dimensional carbon-carbon correlation spectra of BPTI have sufficient resolution to identify and correlate many of the s pin systems associated with the amino acids. As a result, we have been able to assign a large number of the spin systems in this protein. The agreemen t between shifts measured in the solid state and those in solution is typic ally very good, although some shifts near the ion binding sites differ by a t least 1.5 ppm. These studies were conducted with approximately 0.2 to 0.4 mu mol of enriched material; the sensitivity of this method is apparently adequate for other biological systems as well.