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AFM Studies of Salt Concentration Effects on the (110) Surface Structure of Tetragonal Lysozyme CrystalsPrevious high resolution AFM studies of the (110) surface of tetragonal chicken egg white lysozyme crystals had shown that only one of two possible molecular surfaces is present, those constituting the completed 43 helices. These suggested that the crystal growth process was by the solution-phase assembly of the growth units, which then attach to the surface. However, the best fit for the imaged surfaces, vs. those predicted based upon the bulk crystallographic coordinates, were obtained when the packing about the 43 helices was "tightened up", while maintaining the underlying crystallographic unit cell spacing. This results in a widening of the gap between adjacent helices, and the top- most layer(s) may no longer be in contact. We postulated that the tightened packing about the helices is a result of the high salt concentrations in the bulk solution, used to crystallize the protein, driving hydrophobic interactions. Once the crystal surface is sufficiently buried by subsequent growth layers the ratio of salt to protein molecules decreases and the helices relax to their bulk crystallographic coordinates. The crystal surface helix structure is thus a reflection of the solution structure, and the tightness of the packing about the 43 helices would be a function of the bulk salt concentration. AFM images of the (110) surface of tetragonal lysozyme crystals grown under low (2%) and high (5%) NaCl concentrations reveal differences in the packing about the 43 helices consistent with the above proposal.
Document ID
20030062032
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Pusey, Marc Lee
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Gorti, Sridhar
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Forsythe, Elizabeth
(Universities Space Research Association Huntsville, AL, United States)
Konnert, John
(Naval Research Lab. Washington, DC, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2002
Subject Category
General
Meeting Information
Meeting: Biophysical Society Meeting 2003
Location: San Antonio, TX
Country: United States
Start Date: March 1, 2003
End Date: March 5, 2003
Sponsors: Biophysical Society
Distribution Limits
Public
Copyright
Other

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