A naturally present chemical in tobacco may contribute to the onset of diabetes, cancer, aging and Alzheimer's, two scientists at The Scripps Research Institute in La Jolla have found. p The chemical, called nornicotine, "cooks" the body's proteins, triggering the same reaction that turns burned sugar brown and causes food to spoil. "Nornicotine permanently and irreversibly modifies proteins, which can affect their overall function," said Scripps biological chemist Kim D. Janda. Janda and Scripps researcher Tobin J. Dickerson have published their study in the Proceedings of the National Academy of Sciences. The paper appeared online yesterday and will be in...