Proteins in vacuo: a molecular dynamics study of the unfolding behavior of highly charged disulfide-bond-intact lysozyme subjected to a temperature pulse.
Molecular dynamics simulations were used to interpret a variety of experimental data on highly charged disulfide-bond-intact lysozyme in vacuo. The simulation approach involved submitting a model of the protein [Reimann, Velázquez, and Tapia, J. Phys. Chem. B 102, 9344 (1998)] in a given charge state to a 3-ns-long heat pulse (usually at 500 K) followed by cooling or relaxation for 1 ns back to room temperature (293 K). This treatment yielded a charge threshold around Q(0)=8+ for obtaining significant unfolding, as indicated by an enhancement in collision cross section and conformer length. The collision cross sections and lengths theoretically obtained, along with the threshold charge state for initiating unfolding, were compatible with experimental results on lysozyme in vacuo. The unfolded, highly elongated conformations obtained for Q> or = 9+ displayed a significant level of non-native beta-sheet content which appeared to be additionally stabilized by charge self-solvation.
Reimann
C T
CT
Division of Ion Physics, Department of Materials Science, Uppsala University, Box 534, S-751 21 Uppsala, Sweden. curt.reimann@analykem.lu.se
Velázquez
I
I
Bittner
M
M
Tapia
O
O
D000818:Animals; D002642:Chick Embryo / Q000201:enzymology; D003198:Computer Simulation; D004220:Disulfides / Q000737:chemistry*; D006358:Hot Temperature; D006860:Hydrogen Bonding; D008956:Models, Chemical; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry*; D011487:Protein Conformation; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D012996:Solutions
D004220:Disulfides; D012996:Solutions; C421864:hen egg lysozyme; D009113:Muramidase