HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY OF AMINO-ACIDS, PEPTIDES AND PROTEINS .96. TEMPERATURE-INDUCED CHANGES IN THE BANDWIDTH BEHAVIOR OF PROTEINS SEPARATED WITH CATION-EXCHANGE ADSORBENTS

The band-broadening behaviour of several amino acids, peptides and pro teins separated under gradient elution conditions has been investigate d with the 'tentacle-type' LiChrospher-1000 SO3- and the PolySulphoeth yl A cation-exchange adsorbents. In particular, the dependencies of th e bandwidths of this group of biosolutes on temperature and chromatogr aphic residence time have been examined as part of our ongoing investi gations into the influences of secondary equilibrium processes mediate d by conformational interconversions of polypeptides or proteins and t he ligand structure and flexibility in high-performance anion and cati on-exchange chromatographic separations at elevated temperatures. Sign ificantly different band-broadening behaviour was evident with these t wo adsorbents with solute-, ligand- and temperature-specific effects n oted. For several of the proteins examined, bandwidth changes, charact eristic of conformational unfolding processes, occurred at higher temp eratures with the LiChrospher-1000 SO3- adsorbent than with the PolySu lphoethyl A adsorbent. However, at lower temperatures, i.e. between 4 degrees C and 25 degrees C, smaller changes in bandwidth behaviour wer e observed with the PolySulphoethyl A rather than the LiChrospher-1000 SO3- adsorbent. In addition, comparative studies with NaCl and CaCl2 as the displacing salt have revealed significantly different band-broa dening effects with these two salts when these experiments were carrie d out at the same temperature with the LiChrospher-1000 SO3- adsorbent . The origins of these effects have been discussed in terms of the mor phology of these cation-exchange systems and the possible adsorption-d esorption mechanisms that apply when proteins interact with these two high-performance ion-exchange chromatographic adsorbents.