%0 Journal Article %A Voets, Ilja K. %A Cruz, Willemberg A. %A Moitzi, Christian %A Lindner, Peter %A P. G. Arêas, Elizabeth %A Schurtenberger, Peter %D 2010 %T DMSO-Induced Denaturation of Hen Egg White Lysozyme %U https://acs.figshare.com/articles/journal_contribution/DMSO_Induced_Denaturation_of_Hen_Egg_White_Lysozyme/2729419 %R 10.1021/jp103515b.s001 %2 https://acs.figshare.com/ndownloader/files/4405414 %K DMSO volume fractions %K DMSO volume fraction %K Hen Egg White LysozymeWe report %K apolar side groups %K φ DMSO %X We report on the size, shape, structure, and interactions of lysozyme in the ternary system lysozyme/DMSO/water at low protein concentrations. Three structural regimes have been identified, which we term the “folded” (0 < φDMSO < 0.7), “unfolded” (0.7 ≤ φDMSO < 0.9), and “partially collapsed” (0.9 ≤ φDMSO < 1.0) regime. Lysozyme resides in a folded conformation with an average radius of gyration of 1.3 ± 0.1 nm for φDMSO < 0.7 and unfolds (average Rg of 2.4 ± 0.1 nm) above φDMSO > 0.7. This drastic change in the protein’s size coincides with a loss of the characteristic tertiary structure. It is preceded by a compaction of the local environment of the tryptophan residues and accompanied by a large increase in the protein’s overall flexibility. In terms of secondary structure, there is a gradual loss of α-helix and concomitant increase of β-sheet structural elements toward φDMSO = 0.7, while an increase in φDMSO at even higher DMSO volume fractions reduces the presence of both α-helix and β-sheet secondary structural elements. Protein−protein interactions remain overall repulsive for all values of φDMSO. An attempt is made to relate these structural changes to the three most important physical mechanisms that underlie them: the DMSO/water microstructure is strongly dependent on the DMSO volume fraction, DMSO acts as a strong H-bond acceptor, and DMSO is a bad solvent for the protein backbone and a number of relatively polar side groups, but a good solvent for relatively apolar side groups, such as tryptophan. %I ACS Publications