Calculation of the infrared spectra of proteins.

The CHARMM22 force field with associated partial charges is used to calculate the infrared spectra of a number of small proteins and some larger biothreat proteins. The calculated high-frequency region, from about 2,500 to 3,500 cm(-1), is dominated by stretching modes of hydrogen bonded to other atoms, and is very similar in all proteins. There is a peak at 3,430 cm(-1) whose intensity is predicted by these calculations to be a direct measure of arginine content.

Calculated infrared spectra of nerve agents and simulants.

Since organophosphorus nerve agents are among the most toxic known chemical warfare agents, it is desirable to have a way to distinguish between one and another. Infrared spectroscopy is a common tool for identifying molecules. Given the difficulty in handling these chemicals, calculated IR spectra can be useful.