SIMPLE METHOD FOR SAMPLE TEMPERATURE CALIBRATION IN A 500 MHZ NMR SPECTROMETER USEFUL FOR PROTEIN STUDIES

The melting point of several poly (ethylene glycols) (PEGs) was used t o calibrate the temperature above ambient with the separation of the h ydroxyl and methylene peaks of ethylene glycol (EG) on a 500 MHz nucle ar magnetic resonance (NMR) spectrometer. The calibration is almost id entical to a calibration of the EG sample on a 90 MHz NMR spectrometer using a thermocouple. The equation accurately predicts the thermal de naturation midpoint of the protein, hen egg white lysozyme. It is conc luded that in the absence of a small magnet, the calibration of an EG sample using the melting points of PEGs provides a sample temperature calibration, for larger superconducting magnets, useful for protein st ability studies.