UC Riverside

Solid-state NMR (SSNMR) studies on biomolecules and organic molecular crystals are presented here. The biological part of the work is focused on improving resolution and sensitivity of SSNMR techniques for larger protein systems, while the studies on organic molecular crystals extend the application of SSNMR to determining the crystal structure of a photoreaction intermediate. First, a long-observation-window band-selective homonuclear decoupling scheme is introduced. The homonuclear decoupling technique decouples J-couplings during direct 13C acquisition between backbone alpha carbon and carbonyl carbon in U-13C-labeled proteins. The method can be directly incorporated into existing correlation methods that detect carbonyl resonances. Correlation spectroscopy examples are shown on the GB1 and the alpha-subunit of tryptophan synthase. Then, chemical shifts measured at within the beta-site of tryptophan synthase are shown, with indications of potential protonation states explained. After that, the setup of the SSNMR correlation methods are presented. 1H decoupling performance is interpreted using a spin echo experiment with varied decoupling power and magic angle spinning speeds with acquisition on 13C. After the 1H decoupling performance is mapped out, the distance measurements are performed using a perdeuterated Pf1 bacteriophage sample with exchangeable sites protonated. Effects of deuteration and radio frequency power on cross polarization are later discussed on GB1 samples at 50 kHz MAS. This part concludes the preparation of correlation methods to future applications on TS. In the second part of the thesis, NMR crystallography is used to determine the structure of the solid-state photoreaction intermediate of 9-tertbutyl anthracene. The work uses chemical shifts and chemical shift anisotropy parameters measured for microcrystalline solids to validate predicted structures from powder X-ray diffraction and computational data. The resulting structure for the photoreaction intermediate pointed to a possible mechanism for the elongation of 9-tertbutyl anthracene nanorods upon illumination. The studies within this work opens up new possibilities for the scope of the SSNMR technique.