Sodium versus potassium effects on the glutamic acid side-chains interaction on a heptapeptide

Equilibrium peptide conformations in solution, especially in the presence of salts, has been of interest for several decades. The fundamental interactions that determine the dominant peptide conformations in solution have been experimentally and computationally probed; however, a uni¯ed understanding has not yet emerged. In a previous study, we performed metadynamics simulations on the heptapeptide AEAAAEA in Sodium Chloride (NaCl) and Potassium Chloride (KCl) solutions at concentrations ranging from 0.5–2.0 M. Using a three-dimensional collective variable coordinate system, we computed the free energy landscapes in each saline environment as well as in pure water. We found that the presence of Naþ and Kþ ions induces some changes in the stability of the conformers that de¯ne the state space, but does not alter the overall energetics between conformers and does not favor helical conformations. We investigate here, how the presence of salts (NaCl and KCl) a®ects the glutamic–glutamic interaction and its consequences on the stability of each equilibrium conformation. We perform this study through ¯xed backbone simulations for the most populated conformations identi¯ed in our previous work: the -helix, 310-helix, -helix, the extended polyproline II (PPII) and 2.51-helix conformations. It was found that for each conformation, there exists stable substates determined by the glutamic acid side-chains distance and orientation, and that Naþ and Kþ cations (de) stabilize preferentially each conformation. It was also found that intramolecular single water mediated hydrogen bonds play a crucial role in the observed (de) stabilization of each equilibrium conformation.Fil: Asciutto, Eliana Karina. Duquesne University. Department of Chemistry and Biochemistry; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gaborek, Timothy. Duquesne University. Department of Chemistry and Biochemistry; Estados UnidosFil: Madura, Jeffry D.. Duquesne University. Department of Chemistry and Biochemistry; Estados Unido

Predictors of surgical site infection after open lower extremity revascularization

OBJECTIVE: Surgical site infection (SSI) after open lower extremity bypass (LEB) is a serious complication leading to an increased rate of graft failure, hospital readmission, and health care costs. This study sought to identify predictors of SSI after LEB for arterial occlusive disease and also potential modifiable factors to improve outcomes. METHODS: Data from a statewide cardiovascular consortium of 35 hospitals were used to obtain demographic, procedural, and hospital risk factors for patients undergoing elective or urgent open LEB between January 2012 and June 2015. Bivariate comparisons and targeted maximum likelihood estimation were used to identify independent risk factors of SSI. Adjusted odds ratios (ORs) were calculated for patient demographics, comorbidities, operative details, and hospital-level factors. RESULTS: Our study population included 3033 patients who underwent 703 femoral-femoral bypasses, 1431 femoral-popliteal bypasses, and 899 femoral-distal vessel bypasses. An SSI was diagnosed in 320 patients (10.6%) ≤30 days after the index operation. Adjusted patient and procedural predictors of SSI included renal failure currently requiring dialysis (OR, 4.35; 95% confidence interval [CI], 3.45-5.47; P \u3c .001), hypertension (OR, 4.29; 95% CI, 2.74-6.72; P \u3c .001), body mass index ≥25 kg/m2 (OR, 1.78; 95% CI, 1.23-2.57; P = .002), procedural time \u3e240 minutes (OR, 2.95; 95% CI, 1.89-4.62; P \u3c .001), and iodine-only skin preparation (OR, 1.73; 95% CI, 1.02-2.91; P = .04). Hospital factors associated with increased SSI included hospital size \u3c500 beds (OR, 2.22; 95% CI, 1.09-4.55; P = .028) and major teaching hospital (OR, 1.66; 95% CI, 1.07-2.58; P = .024). SSI resulted in increased risk of major amputation and surgical reoperation (P \u3c .01), but did not affect 30-day mortality. CONCLUSIONS: SSI after LEB is associated with an increase in rate of amputation and reoperation. Several patient, operative, and hospital-related risk factors that predict postoperative SSI were identified, suggesting that targeted improvements in perioperative care may decrease complications and improve vascular patient outcomes