The Varian (now Agilent) 400 MHz instrument (MR400) was acquired in 2011 to enhance our research capabilities by running NMR of pharmaceutical compounds (small molecules) and smaller size peptides containing 10-15 amino acid residues. This 400 MHz NMR spectrometer is equipped with OneNMR probe. The OneNMR probe is simultaneously optimized for both high- and low-band frequencies to deliver advantages of both highly sensitive 1H and 13C NMR detection in one. This probe is also equipped with Z-gradient for gradient shimming and for efficient water/solvent suppression using gradient pulses. The OneNMR probe is fitted with automatic tuning and matching for 1H, 13C, 31P, 15N, and 19F. The automatic tuning and matching computer controls nucleus selection as well as tuning and matching for every sample for optimum automation. Fully automated shimming is implemented in this spectrometer and users need not spend time on shimming. However, users are encouraged to get trained to optimize their shimming and calibrate their own hard 90° pulses for any special experiments. For all NMR studies, pulse lengths and RF power level settings are being calibrated and updated periodically in the probe file. The 2H lock sensitivity of the OneNMR probe is enhanced to provide a more stable LOCK, superior line-shape and fast gradient shimming. The short 90° pulse width that it produces is ideal for experiments requiring excitation or decoupling over a wide spectral window (for example 13C or 19F NMR).
This instrument is being used continuously by at least more than 50 users on an average every year-round the clock.
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Most commonly used experiments on MR400 to characterize small molecules: Homonuclear (1H) and heteronuclear 1D (1H, 13C, 31P, 15N, and 19F) such as 1H, DOSY, 13C-DEPT, APT, 31P, 15N, 19F; and 2D NMR experiments such as COSY, DQF-COSY, NOESY, ROESY, TOCSY, HSQC, HMBC, INADEQUATE, and diffusion ordered spectroscopy.
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Sensitivity specifications: The probe sensitivity for 1H is 400:1; 13C is 180:1; 15N is 21:1 and 19F is 550:1.
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NMR software used: VNMR 4.2