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Chemical and thermal denaturation of crystalline bacterial S‐layer proteins: An atomic force microscopy study
Author(s) -
TocaHerrera José L.,
MorenoFlores Susana,
Friedmann Jacqueline,
Pum Dietmar,
Sleytr Uwe B.
Publication year - 2004
Publication title -
microscopy research and technique
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 118
eISSN - 1097-0029
pISSN - 1059-910X
DOI - 10.1002/jemt.20127
Subject(s) - chemistry , chemical engineering , thermal stability , s layer , layer (electronics) , atomic force microscopy , cell wall , silicon , denaturation (fissile materials) , biophysics , nanotechnology , materials science , biochemistry , organic chemistry , nuclear chemistry , biology , engineering , gene
Abstract Crystalline monomolecular cell surface layers, S‐layers, are one of the most common outermost cell envelope components of the prokaryotic organisms (bacteria and archaeda) that protects them from competitive habitats. Since isolated S‐protein subunits are able to re‐assemble into crystalline arrays on lipid films and solid supports making biomimetic surfaces, S‐layer technology is currently used in nanobiotechnology. An important aspect of the biomimetic surfaces built with S‐layers is their stability under extreme solvent conditions or temperature. Chemical (pH, alcohol) and physical (thermal) denaturant conditions were employed to test the stability of S‐layers. Recrystallized bacterial surface layers from Bacillus sphaericus (SbpA) on hydrophilic silicon wafers loses the crystalline structure at 80% ethanol/water mixtures, the change in structure being reversible after treating the surface with buffer solution. SbpA on silicon supports denatures at pH 3 and at 70°C, and the process is irreversible. Cross‐linking of SbpA enhances the stability for high ethanol and acidic conditions, but it does not improve thermal stability. Recrystallized SbpA on secondary cell wall polymer (SCWP), a natural environment for the protein layer, is more resistant to ethanol and pH exposure than recrystallized SbpA on hydrophilic silicon supports. Atomic force microscopy (AFM) was used to monitor the loss of stability and the changes in protein layer conformation. Microsc. Res. Tech. 65:226–234, 2004. © 2005 Wiley‐Liss, Inc.