Experimental Quantum Chemistry: A Hammett-inspired Fingerprinting of Substituent Effects.

The quantum mechanically calculable Q descriptor is shown to be a potent quantifier of chemical reactivity in complex molecules - it shows a strong correlation to experimentally derived field effects in non-aromatic substrates and Hammett σ and σ parameters. Models for predicting substituent effects from Q are presented and applied, including on the elusive pentazolyl substituent. The presented approach enables fast computational estimation of substituent effects, and, in extension, medium-throughput screening of molecules and compound design.

Properties of the Ames Salmonella mutants lodged in the gastrointestinal tract of gnotobiotic rats.

An association of the histidine auxotroph of Salmonella typhimurium (strain TA1538) within the gastrointestinal tract of otherwise germ-free Sprague-Dawley rats is maintained during observations for up to 7 months. The bacteria exceed concentrations of 10(7)/g in the forestomach and exceed concentrations of 10(8)/g in the lower bowel and feces. When carcinogens are ingested, the number of revertants in the feces increases.