Radical research. Free radicals, the chemical, not the political kind, are dangerous to cells. Produced by such diverse forces as ultraviolet radiation, X rays, and food burned on a barbecue, a hydroxyl radical, a duo of oxygen and hydrogen atoms (HO) that was once part of a water molecule (H2O), can seriously damage DNA. The damage can take several forms -- for instance, the radical can attach to one of the bases (adenine, thymine, guanine, or cytosine) that are strung together to make up the sides of the ladder-like DNA scaffold and form a bulge, or it can break one or both sides of the ladder. In most cases, damage is detected by repair proteins, setting in motion a complex repair process.

Tom Tullius, a CAS chemistry professor and chairman of the chemistry department, is interested in how DNA repair is initiated. In particular, he has focused on how a single strand break -- a single missing base and sugar on one of the two strands -- is detected. Recently, Tullius and Hong Guo, a former student of his from Johns Hopkins, who is now at Protometrix, Inc., in Guilford, Conn., have taken a significant step toward understanding this process.

They created DNA molecules bent at a specific location to provide a fixed reference point against which they could understand changes in the structure of the molecule. They then exposed the DNA to hydroxyl radicals to create a library of molecules with gaps at different places along one of the strands. They used a two-dimensional gel electrophoresis system to reveal the resulting shapes. Tullius and Guo found that a second bend was created at the site of the break, and that it was stable and bent in a specific direction relative to the reference bend. The researchers hypothesize that the bend at the site of the break may be the signal by which the cellular repair proteins recognize the problem.

This work was reported in the April 1 issue of the Proceedings of the National Academy of Science.

Couch potato brain. Overeating and lack of exercise may make men less smart, according to a recent study by Merrill Elias, a research professor in the CAS department of mathematics and statistics. The study measured the effects of obesity and high blood pressure, individually and together, on performance on standard tests of intelligence and memory.

Elias and his team found that obese men scored at least 20 percent lower on tests of cognitive functioning than did men who were not obese. Neither factor had a significant effect in women.

Furthermore, the effects of obesity and hypertension were found to be cumulative for men, resulting in lower cognitive functioning when both conditions were present.

Elias hypothesizes that the difference between men and women may be related to where fat is stored in the body -- women tend to store fat around their hips, men in the abdomen.

“People really want to maintain their cognitive functioning as they age,” says Elias. “The possibility that there are conditions that if controlled through treatment would help reduce their risk for cognitive dysfunction should be encouraging to patients and their physicians.”

The study was conducted on a cohort of 1,400 subjects who are part of the Framingham Heart Study, the landmark epidemiological study funded by the National Heart, Lung, and Blood Institute since 1948 and managed by BU since 1970. Elias defined obesity as a body mass index (BMI) of 30 or higher. (BMI is determined by dividing weight in pounds by the square of height in inches, and multiplying the result by 700. A person who is five feet tall and weighs 160 pounds would qualify as obese.) They defined high blood pressure at the national standard, which is greater than 140 over 90.

Elias’ research was reported in the February issue of the International Journal of Obesity.