Acquisition of a Solid-State NMR Ultra-fast Magic Angle Spinning Probe to Investigate Spider Silk

Acquisition of a Solid-State NMR Ultra-fast Magic Angle Spinning Probe to Investigate Spider Silk Acquisition of a Solid-State NMR Ultra-fast Magic Angle spinning Probe to Investigate Spider Silk Solid-state NMR spectroscopy is a powerful tool for studying the molecular structure and dynamics of insoluble materials. This technique does not rely on long-range order to determine structure therefore it is particularly amenable for probing disordered, amorphous and/or heterogeneous systems. One set of materials from this class that is of interest to AFOSR is silk fibers because of their exceptional toughness and numerous potential military applications. Our research group is already funded to study spider silk with magnetic resonance methods (Award FA9550-10-1-0275). This DURIP proposal seeks funding to acquire an ultra-fast magic angle spinning (MAS) probe for an existing 400 MHz NMR spectrometer in the Magnetic Resonance Research Center at Arizona State University. The very fast MAS rates (R 60 kHz) achievable with this NMR probe average the strong 1H-1H dipolar coupling present in rigid solids providing adequate resolution in the proton dimension enabling proton-detection schemes that improve sensitivity. We find that in heterogeneous solids like silks the advantage of proton-detection with ultra-fast MAS is superior compared to crystalline solids. In addition, these rapid MAS speeds extend the transverse lifetimes (T2) for other nuclei (13C/15N), improving the performance of through-bond homonuclear and heteronuclear correlation experiments. Finally, the sample volume of the ultra-fast MAS rotor is far smaller (~10 - 100 x) compared to conventional rotors dramatically decreasing the required sample size. Overall we feel that acquisition of this probe will improve the quality of the NMR data, decrease the experiment time required to acquire the data, and limit the isotope expense by reducing the required amount of material. The acquisition of this NMR probe will benefit the graduate students funded on our AFOSR project by exposing them to cutting-age solid-state NMR equipment that they can use to devise novel NMR approaches to characterize silk-based materials.