Interaction of ectoine and hydroxyectoine with protein: fluorescence study

Abstract

Ectoine and hydroxyectoine are well known extremolytes that accumulate in halophilic and halotolerant microorganisms. They are investigated as protein stabilizers and as excipients in protein formulations and biopharmaceuticals. However, their effect is quite controversial. In this work, the influence of both extremolytes on mink growth hormone as a model protein was studied by fluorescence spectroscopy. The study revealed that the fluorescence quenching of protein tryptophan by ectoine and hydroxyectoine differs and is dependent on the pH value of solution. Moreover, the quenching mode by ectoine and hydroxyectoine was compared with a well-known quencher acrylamide. The differences in the extremolytes interaction with protein revealed by fluorescence spectroscopy could be related to their different effect as protein stabilizers under various conditions.