Primary users of the 500 MHz who are associated with RCMI program are Profs. Mahesh Lakshman, Ranajeet Ghose, Ruth Stark and Barbara Zajc. These investigators are involved in research in chemistry with an emphasis on the structure of biological molecules related to cell function and disease. At present, the Unity Inova 500 NMR spectrometer console has only one full band radio frequency channel (U+ Direct Synthesis type). The second radiofrequency channel is 1H only (U+ HI' type). Because of this the use of the spectrometer is limited to only to a few NMR pulse techniques. In order to improve its utility, the console needs to be upgraded to two U+ Direct Synthesis Full Band or to a console that can handle two high band and two low band channels. At the present configuration, no double resonance experiments involving two high band frequencies (e.g. 1H and 19F) or triple resonance experiments can be performed. The requested upgrade for the 500 NMR spectrometer involves integration to two high band channels and an additional low band channel with a waveform generator. This will handle an inverse probe that is capable of performing triple resonance (1H-13C-19F) experiments as well as two-dimensional 19F-1H correlation experiments. Inverse probes offer impressive 1H sensitivity for inverse detected experiments and have the capabilities for decoupling over the broadband frequency range. The inner coil is tuned to 1H or tunable from 1H - 19F (depending on probe model), and outer coil is tunable over the frequency range 15N - 31P. Because of this, the sensitivity of 1H NMR is enhanced by a factor of 2 in a one-dimensional experiment. The sensitivity gained in two-dimensional 1H-13C HMQC and 1H-13C HSQC experiments, compared to a normal HETCOR experiment, can be up to 8 times greater. HMQC and HSQC experiments are extremely useful for structure determination of bio-molecules and organic compounds. The gain sensitivity will reduce research time and expenses needed to synthesize the organic metabolites and the DNA adducts. To install a third channel an additional de-coupler has to be incorporated. This requires the integration of the following hardware to the current 500-UI console. These include a 20-600 MHz RF transmitter module, a 300 W (12-200 MHz) broadband linear amplifier module, a 150 W (200-245 MHz) broadband linear amplifier module and a 50 W 1H/19F linear amplifier module. The upgrade also includes a waveform generator card. The availability of waveform generator in the console will help in many ways. First, it can generate a variety of shaped pulses for selective decoupling/excitation, and for suppression of multiple solvent peaks. The shaped pulses have added advantages due to their selectivity and less stringent power requirements. For multiple solvent suppression experiments, only the first-channel is used to apply one pulse, which simultaneously has an effect at several positions in the spectrum. Standard spectrometers are equipped with 2 channels. Therefore multiple offset solvent suppression is useful for suppressing more than 2 frequencies and for suppressing two-frequencies while using the second channel for an X nucleus e.g. 13C decoupling. Effective solvent suppression is needed in two-dimensional NOESY experiments using WET-NOESY and WG-NOESY on proteins and oligo-nucleotide adducts. Water suppression by presaturation method leads to drastic reduction in the signal intensities of the resonances of exchangeable protons, viz. imino, amino and amide, due to chemical exchange with water. These experiments are vital for the determination secondary structures of oligo-nucleotide duplexes. The determination of secondary structures of biomolecules is based on extraction of distance constraints from NMR data and restrained molecular dynamics followed by energy minimization. The proposed upgrade of the current NMR spectrometer will enhance and diversify its utility to research groups associated with the RCMI. Budget: Upgrade of the 500 MHz NMR Spectrometer, $184,645.
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