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Category: Applied and Industrial Microbiology
High Hydrostatic Pressure Effects in the Biosphere: from Molecules to Microbiology, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555815646/9781555814236_Chap01-1.gif /docserver/preview/fulltext/10.1128/9781555815646/9781555814236_Chap01-2.gifAbstract:
This chapter aims to give an outline of the effect of high hydrostatic pressure on proteins, lipids, nucleic acids, and their interactions and provide a thermodynamic and kinetic framework to describe these effects. The pressure effects of single-component systems (e.g., a protein in solution) are then related to the viability of microorganisms under extremes of high hydrostatic pressure. A temperature increase will cause a volume expansion, and an increase in pressure will cause a reduction in volume. If, however, as in the case of water, the forces are strong, then an increase in temperature might actually decrease the volume, as is observed between 0 and 4°C, where it reaches its maximum density under ambient pressure conditions. The above-mentioned general principles become even clearer when the effect of pressure on the melting temperature (dTm/dp) of solid hydrocarbons and ice is considered. Proteins similar to the prion proteins involved in bovine spongiform encephalopathy and Creutzfeldt-Jakob’s disease also occur, for instance, in yeasts. Mapping structural features of biomolecules in the pressure-temperature plane is an important research topic for the molecular biologist to see which state of biomolecules is physiologically relevant. Mapping structural features of biomolecules in the pressure-temperature plane is an important research topic for the molecular biologist to see which state of biomolecules is physiologically relevant.
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Isokineticity profiles of the inactivation of a bacterium (Escherichia coli) and a yeast (Zygosaccharomyces bailii) as a function of a combined pressure and temperature treatment. For first-order reactions the decimal reduction time (D) is inversely proportional to the inactivation rate (k). Similar differences in stability have been observed for proteins ( 30 , 46 ). (Redrawn after references 24 and 38 .)
Pressure-temperature phase diagram of proteins. In zone IΔV and S are positive, in zone IIΔV is negative and S is positive, and in zone III both ΔV and ΔS are negative.
Highly schematic representation of the pressure-induced (top) and temperature-induced (bottom) denaturation of a protein. The circles represent water molecules. The first step of the pressure-induced denaturation is the insertion of water without much change in the conformation. For the temperature-induced denaturation the first step is a change in conformation of the protein.
Pressure-temperature phase diagram of different phospholipid bilayer systems in aqueous suspension. Single component bilayers are considered. Note the different slopes of DOPE and DOPC which are both di-cis unsaturated, compared to the mono-cis-unsatured POPC. DPPC, 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine; DMPC, 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine; DEPC, 1,2-dielaidoyl-sn-glycero-3-phosphatidylcholine; POPC, 1-palmitoyl-2-oleoylsn-glycero-3-phosphatidylcholine; DOPE, 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine; DOPC, 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine. (Adapted from reference 53 .)
ΔV associated with specific biochemical reactions (25ºC)