Evaluation of the energetic contribution of interhelical Coulombic interactions for coiled coil helix orientation specificity.

Coiled coils are formed by two or more alpha-helices that align in a parallel or an antiparallel relative orientation. The factors that determine a preference for a given relative helix orientation are incompletely understood. The helix orientation preference for the designed coiled coil, Acid-a1-Base-a1, was measured previously. This model system therefore provides a means for the experimental determination of the energetic contribution of a variety of interactions to helix orientation specificity. The antiparallel preference for Acid-a1-Base-a1 is imparted by a single buried polar interaction. Interhelical Coulombic interactions between residues at the e and g positions have been proposed to influence helix orientation preference. In the Acid-a1-Base-a1 heterodimer, potentially attractive Coulombic interactions are expected in both orientations. To determine the energetic consequences of Coulombic interactions for helix orientation preference, we have positioned a single charged residue in each peptide such that exclusively favorable interhelical Coulombic interactions can occur only in the parallel orientation. In contrast, two potentially repulsive interactions are expected in the antiparallel orientation. Because the buried polar interaction can occur only in the antiparallel orientation, interhelical Coulombic interactions favor the parallel orientation and the potential to form a buried polar interaction favors the antiparallel orientation. We find no clear preference for an antiparallel orientation in the resulting heterodimer, Acid-Ke-Base-Eg, suggesting that interhelical Coulombic interactions and a buried polar interaction are of approximately equal importance for helix orientation specificity. Stability measurements indicate that maintenance of all favorable electrostatic interactions and/or avoidance of two potentially repulsive interactions contributes approximately 2.1 kcal/mol to helix orientation preference.

Gingival effects of prescription medications among adult dental patients.

The relationship between self-reported medication use (exposure to one or more drugs with anticipated gingival effect--antidepressants, diuretics, antihypertensives, hormones) and four measures of gingival conditions (plaque index, gingival index, calculus index, maximum CPITN score) was examined among 594 patients in 35 dental practices in two North Carolina counties. Patients with long-term medication use were compared to patients without long-term use on four measures of gingival condition. When controlling for sex and age within age group, medication use was a significant predictor (P less than 0.05) for elevated gingival and plaque index scores among the white less than 65 group. For the white 65+ group (N = 90), medication use was not a significant predictor for any index score.

PIP: Researchers analyzed 2 sets of data, 1 year apart, on 653 adult dental patients from 35 general practices in 2 counties in North Carolina to examine the association between self reported medication use and 4 measures of gingivitis. They were only concerned about drugs that possible had a gingival effect--diuretics, antidepressants, oral contraceptive and other hormones, and antihypertensives. Only 33% of the 65 year old sample were males basically because 22 female used hormones while no males used hormones. For patients 65 years old, after the researchers controlled for sex and age, medication significantly affected the plaque index and gingival inflammation index scores (p.05). On the other hand, medication did not have an periodontal effects on patients 65 years old. Specifically the adjusted mean score for the plaque index was .38 for those taking medications compared to .29 for those not taking medications. In fact, in preliminary analyses, antidepressant use significantly increased plaque among those 65 years old. The researchers suggested that antidepressants may actually identify people who are not motivated to practice good oral hygiene. The adjusted mean score for gingival inflammation stood at .58 and .47 respectively. Nevertheless the differences in index scores between drug effect categories were slight. Further virtually ever model exhibited larger adjusted score differences by age and gender within age groups. Therefore the researchers concluded tat medication affects the gingiva rather infrequently in adult, ambulatory, regular dental patients regardless of age.