The metallic-like electrical conductivity of Geobacter sulfurreducens pili has been documented with multiple lines of experimental evidence, but there is only a rudimentary understanding of the structural features which contribute to this novel mode of biological electron transport. In order to determine if it was feasible for the pilin monomers of G. sulfurreducens to assemble into a conductive filament, theoretical energy-minimized models of Geobacter pili were constructed with a previously described approach, in which pilin monomers are assembled using randomized structural parameters and distance constraints. The lowest energy models from a specific group of predicted structures lacked a central channel, in contrast to previously existing pili models. In half of the no-channel models the three N-terminal aromatic residues of the pilin monomer are arranged in a potentially electrically conductive geometry, sufficiently close to account for the experimentally observed metallic like conductivity of the pili that has been attributed to overlapping pi-pi orbitals of aromatic amino acids. These atomic resolution models capable of explaining the observed conductive properties of Geobacter pili are a valuable tool to guide further investigation of the metallic-like conductivity of the pili, their role in biogeochemical cycling, and applications in bioenergy and bioelectronics.

BackgroundLimited studies are available to investigate the prevalence of preoperative venous thromboembolism (VTE) in elderly patients with femoral neck fractures. Our primary aim was to determine the incidences of VTE and its risk or protective factors in such patient population. The secondary objective was to evaluate the need of therapeutic anticoagulation for isolated calf muscular venous thrombosis (ICMVT) prior to femoral neck fracture surgery.MethodsThis is a retrospective case-control study, including 301 femoral neck fracture patients who were admitted to our institution between January 2014 and March 2017. Bilateral Doppler ultrasonography was performed in each of the patients as a preoperative VTE screening. The event rate of VTE was calculated, and significant risk or protective factors were determined by using a multivariate logistic regression model. Patients with ICMVT were divided into anticoagulation and no anticoagulation groups to assess the efficacy and safety of preoperative therapeutic anticoagulation. Intraoperative blood loss, drainage volume, blood transfusion, perioperative hemoglobin change, and rate of thrombosis extension were compared between the two groups.ResultsThe overall preoperative incidence of VTE in patients with femoral neck fracture was 18.9% (57/301), in which deep vein thrombosis (DVT) was 18.9% and pulmonary embolism (PE) was 1%. Among the DVT cases, 77.2% (44/57) were ICMVTs. Multiple fractures (odds ratio [OR] = 9.418; 95% confidence interval [CI] = 2.537 to 34.96), coexisting movement disorder (OR = 3.862; 95% CI = 1.658 to 8.993), bed rest for more than 7 days (OR = 2.082; 95% CI = 1.011 to 4.284) as well as elevated levels of D-dimer (OR = 1.019; 95% CI = 1.002 to 1.037) and fibrinogen (OR = 1.345; 95% CI = 1.008 to 1.796) led to an increase in the risk of VTE, while the recent use of antiplatelet drug (OR = 0.424; 95% CI = 0.181 to 0.995) and prophylactic anticoagulation (OR = 0.503; 95% CI = 0.263 to 0.959) decreased the risk of VTE. For the 39 patients with ICMVT undergoing femoral neck fracture surgery, there were no significant differences in the rate of thrombosis extension between anticoagulation and no anticoagulation groups, but significantly decreased postoperative hemoglobin was observed in the anticoagulation group.ConclusionOur findings showed a high prevalence of preoperative VTE in elderly patients with femoral neck fracture, with risk factors identified. We found that the most detected VTE were ICMVTs. Our study suggested that a direct surgery without preoperative use of therapeutic anticoagulation for ICMVT would not reduce the risk of thrombus extension, and the therapeutic use of anticoagulation may worsen postoperative anemia.

The coronavirus disease 2019 (COVID-19) pandemic caused by SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) has become a global public health emergency. G-quadruplex, one of the non-canonical secondary structures, has shown potential antiviral values. However, little is known about the G-quadruplexes of the emerging SARS-CoV-2. Herein, we characterized the potential G-quadruplexes in both positive and negative-sense viral strands. The identified potential G-quadruplexes exhibited similar features to the G-quadruplexes detected in the human transcriptome. Within some bat- and pangolin-related betacoronaviruses, the G-tracts rather than the loops were under heightened selective constraints. We also found that the amino acid sequence similar to SUD (SARS-unique domain) was retained in SARS-CoV-2 but depleted in some other coronaviruses that can infect humans. Further analysis revealed that the amino acid residues related to the binding affinity of G-quadruplexes were conserved among 16,466 SARS-CoV-2 samples. Moreover, the dimer of the SUD-homology structure in SARS-CoV-2 displayed similar electrostatic potential patterns to the SUD dimer from SARS. Considering the potential value of G-quadruplexes to serve as targets in antiviral strategy, our fundamental research could provide new insights for the SARS-CoV-2 drug discovery.