Algebraic disturbances and their consequences in rotating channel flow transition

It is now established that subcritical mechanisms play a crucial role in the transition to turbulence of non-rotating plane shear flows. The role of these mechanisms in rotating channel flow is examined here in the linear and nonlinear stages. Distinct patterns of behaviour are found: the transient growth leading to nonlinearity at low rotation rates $Ro$, a highly chaotic intermediate $Ro$ regime, a localised weak chaos at higher $Ro$, and complete stabilization of transient disturbances at very high $Ro$. At very low $Ro$, the transient growth amplitudes are close to those for non-rotating flow, but Coriolis forces already assert themselves by producing distinct asymmetry about the channel centreline. Nonlinear processes are then triggered, in a streak-breakdown mode of transition. The high $Ro$ regimes do not show these signatures, here the leading eigenmode emerges as dominant in the early stages. Elongated structures plastered close to one wall are seen at higher rotation rates. Rotation is shown to reduce non-normality in the linear operator, in an indirect manifestation of Taylor--Proudman effects. Although the critical Reynolds for exponential growth of instabilities is known to vary a lot with rotation rate, we show that the energy critical Reynolds number is insensitive to rotation rate. It is hoped that these findings will motivate experimental verification, and examination of other rotating flows in this light

Sensitivity of Radical SAM Enzyme MftC to Molecular Oxygen

MftC is a radical S-adenosyl L-methionine (SAM) enzyme that catalyzes the first step in the production of mycofactocin. It is a ribosomally synthesized post-translationally modified (RiPP) redox cofactor shown to be essential for the survival of bacteria in the Mycobacterium genus in the presence of cholesterol as a carbon source and for the sequestration of ethanol. MftC catalyzes the C – terminal decarboxylation of tyrosine and the subsequent cross-linking of tyrosine to the penultimate valine on the precursor peptide MftA. The product formed out of the reaction is processed into mycofactocin in downstream processes. The bacteria in the Mycobacterium tuberculosis complex are pathogens that primarily affect mammalian lung systems and are subjected to oxygenated environments. It is also known that the bacteria in Mycobacterium species require highly aerobic conditions to survive. Radical SAM proteins require anaerobic conditions to catalyze reactions as their [4Fe-4S]2+ clusters are vulnerable to degradation by oxidation. MftC has to function when Mycobacterium species is present in oxygen rich environments such as lung tissue. Discerning the mechanism by which such an enzyme works in oxygen rich environments could provide insights into radical SAM chemistry. In order to investigate the effect of aerobic condition on the MftC reaction, here we seek to measure and demonstrate the change in efficacy of the MftC reaction after varying levels of oxygen exposure. We show that while the rate of the first part of the MftC reaction is slowed on exposure to oxygen, the second part of the reaction – the C – C cross-linking remains relatively unaffected on oxygen exposure

Occurrence, Function, and Biosynthesis of Mycofactocin

Mycofactocin is a member of the rapidly growing class of ribosomally synthesized and post-translationally modified peptide (RiPP) natural products. Although the mycofactocin biosynthetic pathway is widely distributed among Mycobacterial species, the structure, function, and biosynthesis of the pathway product remain unknown. This mini-review will discuss the current state of knowledge regarding the mycofactocin biosynthetic pathway. In particular, we focus on the architecture and distribution of the mycofactocin biosynthetic cluster, mftABCDEF, among the Actinobacteria phylum. We discuss the potential molecular and physiological role of mycofactocin. We review known biosynthetic steps involving MftA, MftB, MftC, and MftE and relate them to pyrroloquinoline quinone biosynthesis. Lastly, we propose the function of the remaining putative biosynthetic enzymes, MftD and MftF

The SARS-CoV nsp12 Polymerase Active Site Is Tuned for Large-Genome Replication

International audienceReplicating large genomes represents a challenge for RNA viruses because fast RNA synthesis is needed to escape innate immunity defenses, but faster polymerases are inherently low-fidelity enzymes. Nonetheless, the coronaviruses replicate their ≈30-kb genomes using the core polymerase structure and mechanism common to all positive-strand RNA viruses

Antineuroinflammatory Activities and Neurotoxicological Assessment of Curcumin Loaded Solid Lipid Nanoparticles on LPS-Stimulated BV-2 Microglia Cell Models

Curcumin, which is a potential antineuroinflammatory and neuroprotective compound, exhibits poor bioavailability in brain cells due to its difficulty in crossing the blood–brain barrier and its rapid metabolism during circulation, which decreases its efficacy in treating chronic neuroinflammatory diseases in the central nervous system. The bioavailability and potential of curcumin can be improved by using a nanodelivery system, which includes solid lipid nanoparticles. Curcumin-loaded solid lipid nanoparticles (SLCN) were efficiently developed to have a particle size of about 86 nm and do not exhibit any toxicity in the endothelial brain cells. Furthermore, the curcumin-loaded solid lipid nanoparticles (SLCN) were studied to assess their efficacy in BV-2 microglial cells against LPS-induced neuroinflammation. The SLCN showed a higher inhibition of nitric oxide (NO) production compared to conventional curcumin in a dose-dependent manner. Similarly, the mRNA and proinflammatory cytokine levels were also reduced in a dose-dependent manner when compared to those with free curcumin. Thus, SLCN could be a potential delivery system for curcumin to treat microglia-mediated neuroinflammation

Toothbrushes as a Source of DNA for Gender and Human Identification—A Systematic Review

Background: Few studies have reported the use of toothbrushes as a reliable source of DNA for human or gender identification. The present systematic review with the available information was conducted to answer the focus question “Is a toothbrush a reliable source of DNA for human or gender identification?”. Methods: The keyword combination “Toothbrush” and “DNA” was used to search databases including MEDLINE, Scopus, and Web of Science along with a manual search of reference lists of relevant articles. Duplicates and irrelevant articles were excluded, and the remaining articles were fully read for the final selection of articles. The risk of bias of the included studies was evaluated using the Appraisal tool for Cross-Sectional Studies (AXIS tool). Results: Of the 130 articles obtained, 122 duplicates or irrelevant articles were eliminated. Following the full-text reading of eight articles, five articles were selected based on eligibility criteria. The five studies reported that a toothbrush is a good source of DNA irrespective of the time interval. In a few studies some samples were not sufficient for complete DNA profiling due to factors such as the method of DNA extraction. Conclusion: Although a toothbrush is an excellent source of DNA for human and gender identification, future studies with a larger sample size, appropriate control group, and standardized technique of DNA extraction need to be conducted. Additionally, factors influencing the quantity and quality of DNA in toothbrushes need to be determined with standardized techniques

Is Palatal Rugae Pattern a Reliable Tool for Personal Identification following Orthodontic Treatment? A Systematic Review and Meta-Analysis

Background: To qualitatively and quantitatively review the reliability of palatal rugae as a tool for personal identification following orthodontic treatment. Methods: Cross-sectional retrospective studies assessing the accuracy of matching palatal rugae pattern pre- and post-orthodontic treatment were identified from PubMed and SCOPUS databases. The title and abstract of the articles identified in the search were screened for potential duplicates and relevancy to the topic of interest. The full text of the articles selected in the screening was analyzed using the inclusion and exclusion criteria. Quantitative analysis of the studies representing coherent data in terms of age and treatment choice was performed using RevMan software. Results: Out of 64 screened articles, only 18 articles fulfilled the eligibility criteria and were included in the systematic review. Out of these 18 articles, only 3 studies had data compatible with the quantitative analysis. Significant changes were noted in lateral first rugae in transverse bilateral direction (p = 0.02) and between second and third lateral rugae of the left side in the anteroposterior direction (p = 0.04). Despite the dimensional changes, observers in most studies were able to accurately (>90%) match the palatal rugae pre- and post-orthodontic treatment through visual observation. Conclusion: The accuracy of the visual matching, despite the significant dimensional changes, indicates that morphology could have potentially been the major matching factor. Thus, a combination of dimensional and morphological evaluation of the palatal rugae could potentially increase the accuracy of personal identification

Role of Toothbrushes as Gene Expression Profiling Tool for Oral Cancer Screening in Tobacco and Alcohol Users

Aim: The use of toothbrushes was investigated as a potential RNA source and gene expression profiling tool for oral cancer screening in tobacco and alcohol users. Methodology: A total of 20 subjects were selected on the basis of inclusion and exclusion criteria. They were divided into two groups: group I—healthy controls (n = 6); group II—individuals who consume tobacco and alcohol (n = 14). After the volunteers brushed their teeth using a soft-bristle toothbrush with ~0.5 gm of toothpaste, the toothbrushes were collected, and the gene expression of BAX, BCL2, CDK4, CKDN2A, GNB3, and TCF7L2 was assessed. Results: The gene expression of BAX decreased significantly in alcoholics and smokers (0.13867 ± 0.12014), while the gene expression of BCL2 increased in alcoholics and smokers (1.91001 ± 0.90425) in comparison with healthy controls (p = 0.0054 and p = 0.0055). Although there was increased expression of CDK4, CKDN2A, and TCF7L2 and decreased expression of GNB3 in smokers and alcoholics, the results were not significant. Conclusions: A toothbrush is a good source of RNA, and gene expression analysis can be performed using the genetic material retrieved from toothbrushes, which can aid in the early diagnosis of oral squamous cell carcinoma among tobacco and alcohol users. Further studies with a larger sample size and different durations of toothbrush use should be conducted to explore the role of toothbrushes as a noninvasive tool for disease diagnosis