Biomolecules in hydrothermal systems: Calculation of the standard molal thermodynamic properties of nucleic-acid bases, nucleosides, and nucleotides at elevated temperatures and pressures

Abstract

Calculation of the thermodynamic properties of biomolecules at high temperatures and pressures is fundamental to understanding the biogeochemistry of hydrothermal systems. Ample evidence indicates that hyperthermophilic microbes interact chemically with their mineralogical environment in these systems. Nevertheless, little is known about the thermodynamic properties of the biomolecules involved in such processes. Recent advances in theoretical biogeochemistry make it possible to calculate these properties using the limited experimental data available in the literature, together with correlation and group additivity algorithms, reference model compounds, and the revised HKF equations of state. This approach permits calculation of the standard molal thermodynamic properties of the 120 common protonated and deprotonated nucleotides and their constituent nucleic-acid bases and nucleosides as a function of temperature and pressure. The requisite equations of state parameters can be calculated from experimental standard molal heat capacities, volumes, and compressibilities reported in the literature for nucleic-acid bases and nucleosides. Because no calorimetric or densimetric data are available for the nucleotides, experimental heats of reaction taken from the literature were used together with correlation and group additivity algorithms to generate provisional values of the corresponding equations of state parameters for the nucleotides. The thermodynamic properties and revised HKF equations of state parameters generated in the present study can be used to carry out comprehensive mass transfer and Gibbs energy calculations to describe and quantify the chemical interaction of minerals and microbes in hydrothermal systems.