Isolation, characterization and mapping of temperature-sensitive mutants of mycobacteriophage I3

Eighteen temperature-sensitive mutants of mycobacteriophage I3 have been isolated and partially characterized. All the mutants were defective in vegetative replication. Based on temperature shift experiments with the temperature sensitive mutants, the thermosensitive phase of the phage development period has been characterized for each mutant. The genes have been mapped by recombination analysis. The early, continuous and middle genes seem to cluster on the genetic ma

The Critical Role of N- and C-Terminal Contact in Protein Stability and Folding of a Family 10 Xylanase under Extreme Conditions

Stabilization strategies adopted by proteins under extreme conditions are very complex and involve various kinds of interactions. Recent studies have shown that a large proportion of proteins have their N- and C-terminal elements in close contact and suggested they play a role in protein folding and stability. However, the biological significance of this contact remains elusive.In the present study, we investigate the role of N- and C-terminal residue interaction using a family 10 xylanase (BSX) with a TIM-barrel structure that shows stability under high temperature, alkali pH, and protease and SDS treatment. Based on crystal structure, an aromatic cluster was identified that involves Phe4, Trp6 and Tyr343 holding the N- and C-terminus together; this is a unique and important feature of this protein that might be crucial for folding and stability under poly-extreme conditions. folding and activity. Alanine substitution with Phe4, Trp6 and Tyr343 drastically decreased stability under all parameters studied. Importantly, substitution of Phe4 with Trp increased stability in SDS treatment. Mass spectrometry results of limited proteolysis further demonstrated that the Arg344 residue is highly susceptible to trypsin digestion in sensitive mutants such as ΔF4, W6A and Y343A, suggesting again that disruption of the Phe4-Trp6-Tyr343 (F-W-Y) cluster destabilizes the N- and C-terminal interaction. Our results underscore the importance of N- and C-terminal contact through aromatic interactions in protein folding and stability under extreme conditions, and these results may be useful to improve the stability of other proteins under suboptimal conditions

Size dependent resonance energy transfer between semiconductor quantum dots and dye using FRET and kinetic model

In the present study, we demonstrate the size dependent resonance energy transfer from CdSe QDs (donor) to Nile Red dye (acceptor) using steady state and time-resolved spectroscopy. A strong evidence of size dependent efficient resonance energy transfer between CdSe QDs and dye molecules is observed. Using the Förster theory, the calculated energy transfer efficiencies from QD to dye are 8.4, 13.8, and 51.2% for 2.4 nm CdSe, 2.9 nm CdSe, and 3.3 nm CdSe, respectively. A stochastic model for the kinetics of energy transfer from CdSe QDs to Nile Red dye molecules has been proposed to understand the interaction between excited states of CdSe QDs with dye molecules. By analyzing time-resolved fluorescence decay curves of CdSe QDs in the absence and in the presence of Nile Red dye, the values of the rate constant (kq) for energy transfer per one dye molecule and the efficiency (ϕET) of quenching have been calculated. The estimated energy transfer rates are 0.002, 0.016, and 0.038 ns−1 for 2.4 nm CdSe, 2.9 nm CdSe, and 3.3 nm CdSe QDs, respectively, which are well matched with FRET data

Pathophysiology of thromboembolism in patients with COVID-19

Introduction and aim. A small number of critically ill patients with coronavirus disease (COVID-19) develop thromboembolism (arterial or venous), both micro- and macrovascular complications such as deep vein thrombosis, pulmonary embolism, and pulmonary arterial thrombosis. The objective of the study is to describe the pathophysiology of venous thromboembolism in patients with COVID-19. Material and methods. In this article a narrative review regarding pathophysiology of thromboembolism in patients with COVID-19. Analysis of the literature. The development of coagulopathy is a consequence of the intense inflammatory response associated with hypercoagulability, platelet activation, and endothelial dysfunction. The pathophysiology that relates pulmonary thromboembolism (PTE) with COVID-19 is associated with a hypercoagulable state. PTE is suspected in hospitalized patients presenting dyspnea, decreased oxygen requirement, hemodynamic instability, and dissociation between hemodynamic and respiratory changes. In COVID-19-associated coagulopathy, initially, patients present with elevated levels of fibrinogen and D-dimer, with minimal changes in prothrombin time and platelet count. The main risk factor for the development of pulmonary embolism is the increase in D-dimer that is associated with the development of PTE. The administration of iodine-based contrast agent to patients with COVID-19 would affect P-creatinine and renal function, where Ultrasound is viewed as cost-effective and highly portable, can be performed at the bedside. Conclusion. Acute respiratory distress syndrome severity in patients with COVID-19 can explain PTE as a consequence of an exaggerated immune response