Computational design of a thermolabile uracil-DNA glycosylase of Escherichia coli.

Polymerase chain reaction (PCR) is a powerful tool to diagnose infectious diseases. Uracil DNA glycosylase (UDG) is broadly used to remove carryover contamination in PCR. However, UDG can contribute to false negative results when not inactivated completely, leading to DNA degradation during the amplification step. In this study, we designed novel thermolabile UDG derivatives by supercomputing molecular dynamic simulations and residual network analysis. Based on enzyme activity analysis, thermolability, thermal stability, and biochemical experiments of Escherichia coli-derived UDG and 22 derivatives, we uncovered that the UDG D43A mutant eliminated the false negative problem, demonstrated high efficiency, and offered great benefit for use in PCR diagnosis. We further obtained structural and thermodynamic insights into the role of the D43A mutation, including perturbed protein structure near D43; weakened pairwise interactions of D43 with K42, N46, and R80; and decreased melting temperature and native fraction of the UDG D43A mutant compared with wild-type UDG.

Persistent smoking after a cardiovascular event: A nationwide retrospective study in Korea.

Smoking is a major risk factor of cardiovascular disease (CVD) such as stroke and ischemic heart disease. Prior studies have observed people continued smoking even after being diagnosed with CVD. However, population-level data regarding smoking behavior changes among people who are diagnosed with CVD are still lacking. From the National Health Insurance sample cohort database, we identified 1,700 patients diagnosed as having CVD between 2003 and 2012, and underwent the national health screening examination in the year before and after the CVD event. We found that 486 (28.6%) were smokers before the CVD event. Among them, 240 (49.4%) continued to smoke despite the diagnosis. We observed that a higher smoking amount and longer smoking duration before the diagnosis were associated with persistent smoking. Our finding that approximately 50% of smokers continue smoking even after CVD events supports the need for an assessment of patients' smoking statuses during follow-up after a CVD event and for health-care providers to offer the appropriate smoking cessation interventions to those who continue smoking.