α-chymotrypsin is a well characterised mammalian digestive enzyme that catalyses the hydrolytic cleavage of peptide bonds at the carboxyl side of aromatic residues. During the chymotrypsin-catalysed hydrolysis of N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide (Suc-AAPF-pNA; see figure 1), formation of the p-nitroaniline product can be followed spectroscopically at 410 nm while the peptide product can be monitored by FT-IR spectroscopy due to formation of a new C-terminal carboxylate group. The VERTEX 80 FT-IR spectrometer with the UltraScanTM linear air bearing scanner with True-Alignment technology is ideally suited for such kinetic studies, since at the fastest mirror velocity (320 kHz) more than 100 spectra at resolution 16 cm-1 can be collected per second.