Investigating the specificity of regulators of degradation of hydrocarbonsand hydrocarbon-based compounds using structure-activity relationships

Microbial biosensors which have genes for bioluminescence coupled to genes that control hydrocarbon degradation pathways can be used as reporters on t he specificity of regulation of those pathways. Structure-activity relation ships can be used to discover what governs that specificity, and can also b e used to separate compounds into different groups depending on mode of act ion. Published data for four different bioluminescent biosensors, reporting on toluene (two separate biosensors), isopropylbenzene, and octane, were a nalyzed to develop structure-activity relationships between biological resp onse and physical/chemical properties. Good QSARs (quantitative structure-a ctivity relationships) were developed for three out of the four biosensors, with between 88 and 100 per cent of the variance explained. Parameters fou nd to be important in controlling regulator specificity were hydrophobicity , lowest unoccupied molecular orbital energies, and molar volume. For one o f the biosensors, it was possible to show that the biological response to c hemicals tested fell into three separate classes (non-hydrocarbons, aliphat ic hydrocarbons, and aromatic hydrocarbons). A statistically significant QS AR based on hydrophobicity was developed for the fourth biosensor, but was poor in comparison to the other three (44 per cent variance explained).