RELATIVE STABILITIES OF BIOMOLECULES AT HIGH-TEMPERATURES AND PRESSURES

Determination of the thermodynamic properties of biomolecules at eleva ted temperatures and pressures is critical to understanding enzymatic activity and the role of hyperthermo-barophilic microbes in both indus trial and natural hydrothermal processes. Experimental data reported i n the literature indicate that amino acids and other aqueous biomolecu les become increasingly sensitive to their chemical environment with i ncreasing temperature. If this environment is not conducive to metasta ble preservation of biomolecules, they become highly reactive at high temperatures and pressures. However, increasing temperature does not t hen simply result in decomposition of biomolecules to form H2O, CO2, H -2, and/or other ''inorganic'' species, but instead they react to form additional ''organic'' and/or ''inorganic'' molecules, which may or m ay not achieve metastable equilibrium with one another under the condi tions prevailing in the system. These conditions include the chemical potentials of H-2 (and therefore O-2)(1), CO2, NH3, and H2S. If the ch emical potentials of these components are favorable, amino acids and o ther bimolecules may persist at high temperatures for periods of time well in excess of those required for regeneration of the molecules, ei ther abiotically or by hyperthermobarophilic microbes. Because irrever sible reaction of biomolecules with other aqueous species, as well as metastable equilibrium states resulting from such reactions are highly sensitive to the activities of H-2, CO2, NH3, H2S, and other species in solution. these activities must be controlled or at least monitored to achieve unambiguous results in hydrothermal experiments designed t o measure the thermodynamic properties of biomolecules as a function o f temperature and/or pressure. Such experiments are necessary to calib rate and verify equations of state, which can then be used to characte rize the thermodynamic behavior of biomolecules at elevated temperatur es and pressures. Only by quantifying this behavior can we determine o ptimal conditions for enzymatic activity and predict the degree to whi ch reactions among amino acids, polypeptides, proteins, nucleic acids, and other aqueous species are exergonic at high temperatures and pres sures. Carefully controlled hydrothermal studies of enzymes and other biomolecules produced by hyperthermobarophilic microbes as a function of temperature, pressure, and the chemical potentials of H-2, CO2, NH3 , H2S, and other components of the system should lead to development o f new avenues of medical research and a better understanding of bacter ial genetics, enzymatic catalysis, DNA replication, and many other bio chemical processes on which life depends.