The influence of column residency times on the reversed-phase gradient elution behaviour of human and bovine growth hormones has been investigated using on-line photodiode array spectroscopic detection. Stationary phase induced effects on protein conformation were monitored by changes in the maxima to minima ratio of the second derivative spectrum of the eluted protein. Significant changes in the second derivative ratio of the unmodified and the fully reduced and alkylated protein were observed following long incubation times, i.e. t(dwell) > 15 min, at the stationary phase surface in the presence of 0.1% trifluoroacetic acid before elution with a 0-75% aqueous acetonitrile gradient. The application of multi-wavelength detection in the study of equilibrium unfolding of growth hormones in urea by size-exclusion chromatography was also investigated. On-line photodiode array instrumentation and derivative spectra ratioing was employed to monitor tertiary and quaternary structural changes associated with protein denaturation during a chromatographic separation. These studies clearly demonstrate the powerful detection capabilities of such instrumental approaches for the on-line evaluation of both stationary phase surface and/or mobile phase mediated changes in protein conformation. © 1988.
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