DMSO-Induced Denaturation of Hen Egg White Lysozyme

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 < phi(DMSO) < 0.7), ""unfolded"" (0.7 <= phi(DMSO) < 0.9), and ""partially collapsed"" (0.9 <= phi(DMSO) < 1.0) regime. Lysozyme resides in a folded conformation with an average radius of gyration of 1.3 +/- 0.1 nm for phi(DMSO) < 0.7 and unfolds (average R(g) of 2.4 +/- 0.1 nm) above phi(DMSO) > 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 alpha-helix and concomitant increase of beta-sheet structural elements toward phi(DMSO) = 0.7, while an increase in phi(DMSO) at even higher DMSO volume fractions reduces the presence of both a-helix and beta-sheet secondary structural elements. Protein-protein interactions remain overall repulsive for all values of phi(DMSO) 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.

Students Working on Telephone Poles at the New York Trade School

A group of twelve students are learning how to work on telephone poles at the New York Trade School. Black and white photograph with some minor damage to the image in the bottom left hand corner.

New York Trade School Administration [1]

A group of administrators from the New York Trade School posing in front of a building. Black and white photograph.

New York Trade School Administration [2]

A group of administrators from the New York Trade School pose in front of the school's building on East 67th Street. The photograph is black and white.

New York Trade School Administration [3]

This black and white photograph features two administrators positioned at desk.

New York Trade School Administration [4]

A New York Trade School administrator is posed for a formal photo. Black and white photograph.

New York Trade School Administration [5]

This New York Trade School administrator is posed in front of a wall plaque dedicated to the founder of the school. Photograph is black and white.

Students working in a class at the New York Trade School

A group of four students are working in a classroom at the New York Trade School while a professor looks on.

Students Working in Carpentry Shop at the New York Trade School

This black and white photograph shows students at work benches in part of the carpentry workshop at the New York Trade School. Beyond the benches two students can be seen working on framing in the rear of the classroom.

Students Working on a Model House at the New York Trade School

Students, likely studying carpentry, are shown working on the roof of a model of a house in a classroom at the New York Trade School. Black and white photograph.

Classroom at the New York Trade School

An empty classroom is shown here at the New York Trade School. This was likely a piano tuning classroom. Black and white photograph with some damage around the edges.

View of the library at the New York Trade School

This photograph shows several empty tables and a few shelves in the library at the New York Trade School. Black and white photograph.

Piano Performance at the New York Trade School

A piano player is shown performing at the New York Trade School. He is likely playing on a piano tuned or built by students in the Piano Crafts Department at the school. Black and white photograph.

View of Air Conditioning and Refrigeration classroom at the New York Trade School

This black and white photograph shows classroom space of the Air Conditioning/Refrigeration Dept. empty of students. Black and white photograph.

Students at work in the Air Conditioning and Refrigeration Department of the New York Trade School

Students in the Air Conditioning/Refrigeration Dept. of the New York Trade School are shown hard at work in the classroom. Notice the sign at the rear of the room that reads "Watch Out for Pipes on Floor." Black and white photograph.