Kinetics and mechanism of chromium hexacarbonyl photochemistry using flash by photolysis

Chromium hexacarbonyl, Cr(CO)6, has been shown to be a very effective photochemical catalyst for many reactions, such as the 1,4- hydrogenation and 1 ,4-hydrosilation of conjugated 1 ,3-dienes resulting in the formation of a cis alkene product in greater than 99% yield. Although much research has been done on the reactions which Cr(CO)6 catalyzes, not much data exists on the reactions of photochemically created fragments of Cr(CO)6 , such as Cr(CO)6. This study focuses on the reactivity of organotransition metal intermediates with the goal of contributing to the growing database of the reactions involving the photochemistry of Cr(CO)6. Particular emphasis will be given to the kinetics and mechanism of these reactions. Experiments with Cr(CO)6 require the use of an extremely pure solvents. Since it has been found that metal carbonyls are very sensitive to such impurities as water and oxygen, solvents must be dried and degassed. This is done by refluxing the solvent over CaH2 for 12 hours under flowing purified argon, followed by a second distillation in a fractionating column. Argon is purified by passing through one 13x molecular sieves column and one Oz scavenging column to remove water, oxygen and organic impurities. The chromium hexacarbonyl solution was degassed by six freeze-pump-thaw cycles. Chromium hexacarbonyl solutions have been flashed and the subsequent thermal reaction was found to follow second order kinetics. The solution was then saturated with CO and the reaction kinetics changed to pseudo-first order. Plots of kobs vs. [CO] are linear with the slope equal to the second-order rate constant. The value of this constant was found to be 1.7 x 106 M-1 s-1, which is two times sma11er than the literature value of 3.6 x106 M-1 s-1

Female Scent Signals Enhance the Resistance of Male Mice to Influenza

Background: The scent from receptive female mice functions as a signal, which stimulates male mice to search for potential mating partners. This searching behavior is coupled with infection risk due to sniffing both scent marks as well as nasal and anogenital areas of females, which harbor bacteria and viruses. Consideration of host evolution under unavoidable parasitic pressures, including helminthes, bacteria, viruses, etc., predicts adaptations that help protect hosts against the parasites associated with mating. Methods and Findings: We propose that the perception of female signals by BALB/c male mice leads to adaptive redistribution of the immune defense directed to protection against respiratory infection risks. Our results demonstrate migration of macrophages and neutrophils to the upper airways upon exposure to female odor stimuli, which results in an increased resistance of the males to experimental influenza virus infection. This moderate leukocyte intervention had no negative effect on the aerobic performance in male mice. Conclusions: Our data provide the first demonstration of the adaptive immunological response to female odor stimul

Direct Measurement of Cardiac Na+ Channel Conformations Reveals Molecular Pathologies of Inherited Mutations.

BACKGROUND -Dysregulation of voltage-gated cardiac Na(+) channels (NaV1.5) by inherited mutations, disease-linked remodeling, and drugs causes arrhythmias. The molecular mechanisms whereby the NaV1.5 voltage-sensing domains (VSDs) are perturbed to pathologically or therapeutically modulate Na(+) current (INa) have not been specified. Our aim was to correlate INa kinetics with conformational changes within the four (DI-DIV) VSDs to define molecular mechanisms of NaV1.5 modulation. METHOD AND RESULTS -Four NaV1.5 constructs were created to track the voltage-dependent kinetics of conformational changes within each VSD, using voltage-clamp fluorometry (VCF). Each VSD displayed unique kinetics, consistent with distinct roles in determining INa. In particular, DIII-VSD deactivation kinetics were modulated by depolarizing pulses with durations in the intermediate time domain that modulates late INa. We then used the DII-VSD construct to probe the molecular pathology of two Brugada Syndrome (BrS) mutations (A735V and G752R). A735V shifted DII-VSD voltage-dependence to depolarized potentials, while G752R significantly slowed DII-VSD kinetics. Both mutations slowed INa activation, even though DII-VSD activation occurred at higher potentials (A735V) or at later times (G752R) than ionic current activation, indicating that the DII-VSD allosterically regulates the rate of INa activation and myocyte excitability. CONCLUSIONS -Our results reveal novel mechanisms whereby the NaV1.5 VSDs regulate its activation and inactivation. The ability to distinguish distinct molecular mechanisms of proximal BrS mutations demonstrates the potential of these methods to reveal how inherited mutations, post-translational modifications and anti-arrhythmic drugs alter NaV1.5 at the molecular level

Experimental animal models of scoliosis for understanding the etiology of idiopathic scoliosis

Idiopathic scoliosis is a common disease of the musculoskeletal system, affecting 2–3% of children and adolescents worldwide. The etiology and pathogenesis of scoliotic spinal deformity have not yet been disclosed, despite numerous long-term studies. Animal modeling of scoliosis can become the basis for studying possible etiological factors and pathogenetic mechanisms of the formation of the pathology in question and the prospects for possible treatment of scoliosis in the future. To date, many different types of models of scoliotic disease have been created and studied. The purpose of this review was to analyze the literature data on animal modeling of scoliosis in order to understand the etiological factor of idiopathic scoliosis in humans. Material and methods. The review was carried out using databases of electronic information resources PubMed (MEDLINE), Scopus, eLibrary.ru. The analysis of scientific literature was carried out according to the search words: “idiopathic scoliosis”, “experimental model of scoliosis”, “animal model of scoliosis”, “mechanical models of scoliosis”, “pineal gland resection models”, “genetic models of scoliosis”. Results. The analysis of scientific literature data confirms the high importance of experimental animal models of scoliosis for the study of the etiology of idiopathic scoliosis. The review summarizes and analyzes data on the main directions of modeling scoliotic deformity: mechanical, neuroendocrine and genetic models. Conclusions. The models of scoliosis presented in the literature have been implemented with varying degrees of success and have not been able to clarify the etiology of spinal pathology, but they are a useful tool for testing interventions aimed at correcting and preventing deformity. The development of an optimal experimental model of scoliosis in animals will further overcome the existing limitations in determining the etiological factor of idiopathic scoliosis and describe the processes of disease development characteristic of humans

Defining hierarchical protein interaction networks from spectral analysis of bacterial proteomes

Cellular behaviors emerge from layers of molecular interactions: proteins interact to form complexes, pathways, and phenotypes. We show that hierarchical networks of protein interactions can be defined from the statistical pattern of proteome variation measured across thousands of diverse bacteria and that these networks reflect the emergence of complex bacterial phenotypes. Our results are validated through gene-set enrichment analysis and comparison to existing experimentally derived databases. We demonstrate the biological utility of our approach by creating a model of motility i

A phytobacterial TIR domain effector manipulates NAD\u3csup\u3e+\u3c/sup\u3e to promote virulence

The Pseudomonas syringae DC3000 type III effector HopAM1 suppresses plant immunity and contains a Toll/interleukin-1 receptor (TIR) domain homologous to immunity-related TIR domains of plant nucleotide-binding leucine-rich repeat receptors that hydrolyze nicotinamide adenine dinucleotide (NAD+) and activate immunity. In vitro and in vivo assays were conducted to determine if HopAM1 hydrolyzes NAD+ and if the activity is essential for HopAM1’s suppression of plant immunity and contribution to virulence. HPLC and LC-MS were utilized to analyze metabolites produced from NAD+ by HopAM1 in vitro and in both yeast and plants. Agrobacterium-mediated transient expression and in planta inoculation assays were performed to determine HopAM1’s intrinsic enzymatic activity and virulence contribution. HopAM1 is catalytically active and hydrolyzes NAD+ to produce nicotinamide and a novel cADPR variant (v2-cADPR). Expression of HopAM1 triggers cell death in yeast and plants dependent on the putative catalytic residue glutamic acid 191 (E191) within the TIR domain. Furthermore, HopAM1’s E191 residue is required to suppress both pattern-triggered immunity and effector-triggered immunity and promote P. syringae virulence. HopAM1 manipulates endogenous NAD+ to produce v2-cADPR and promote pathogenesis. This work suggests that HopAM1’s TIR domain possesses different catalytic specificity than other TIR domain-containing NAD+ hydrolases and that pathogens exploit this activity to sabotage NAD+ metabolism for immune suppression and virulence

Idiopathic scoliosis: general characteristics and analysis of etiological theories (literature review)

Idiopathic scoliosis is a severe pathology of the musculoskeletal system that affects children and adolescents all over the world. The disease occurs in approximately 0.2-0.6% of the general population, and is the largest subgroup of spinal curvature in humans (70-90% of all known scoliosis cases). In idiopathic scoliosis, a threedimensional deformation of the vertebral column is formed, leading to the formation of a rib hump, curvature of the ribs and chest, asymmetry of the pelvis and impaired development of internal organs. The main feature of the disease is the spontaneous development of deformity during the growth of the child and the tendency to progress. Scoliosis is not only an orthopedic disease, but also a ignificant cosmetic, and, consequently, a psychological and social problem. The standard of treatment for scoliotic disease remains unchanged for a long time: observation, corset treatment and surgical correction. The prognosis for the development of pathology varies depending on the degree of deformation. The corset-therapy, hospitalization, surgery and treatment of chronic back pain have a negative impact on the psychoemotional state of children and adolescents. Despite significant advances in the methods of diagnosis of deformity, improvement of surgical treatment methods and in the study of pathogenesis, the etiological factor of pathology is still unknown. The search for the causes of idiopathic scoliosis covers almost all aspects of its possible origin: genetic, environmental, hormonal, metabolic, biochemical, neurological, and others. In recent decades, relevant theories of the development of scoliosis have been formulated, but none of the theories reveals the essence of the pathological process and has no clear justification. The greatest number of supporters is the genetic theory: genetic factors play a key role in the occurrence and development of idiopathic scoliosis. Understanding the underlying factors of the disease will enable prevention, early diagnosis, and identification of the risk groups of the patients in question

A phytobacterial TIR domain effector manipulates NAD\u3csup\u3e+\u3c/sup\u3e to promote virulence

The Pseudomonas syringae DC3000 type III effector HopAM1 suppresses plant immunity and contains a Toll/interleukin-1 receptor (TIR) domain homologous to immunity-related TIR domains of plant nucleotide-binding leucine-rich repeat receptors that hydrolyze nicotinamide adenine dinucleotide (NAD+) and activate immunity. In vitro and in vivo assays were conducted to determine if HopAM1 hydrolyzes NAD+ and if the activity is essential for HopAM1’s suppression of plant immunity and contribution to virulence. HPLC and LC-MS were utilized to analyze metabolites produced from NAD+ by HopAM1 in vitro and in both yeast and plants. Agrobacterium-mediated transient expression and in planta inoculation assays were performed to determine HopAM1’s intrinsic enzymatic activity and virulence contribution. HopAM1 is catalytically active and hydrolyzes NAD+ to produce nicotinamide and a novel cADPR variant (v2-cADPR). Expression of HopAM1 triggers cell death in yeast and plants dependent on the putative catalytic residue glutamic acid 191 (E191) within the TIR domain. Furthermore, HopAM1’s E191 residue is required to suppress both pattern-triggered immunity and effector-triggered immunity and promote P. syringae virulence. HopAM1 manipulates endogenous NAD+ to produce v2-cADPR and promote pathogenesis. This work suggests that HopAM1’s TIR domain possesses different catalytic specificity than other TIR domain-containing NAD+ hydrolases and that pathogens exploit this activity to sabotage NAD+ metabolism for immune suppression and virulence