Microbial reduction of hexavalent chromium [Cr(VI)] to trivalent [Cr(III)] has been investigated as a method for bioremediation Cr(VI) contaminated environments. The produced Cr(III) is thought be insoluble Cr(OH)3; however, recent reports suggested more complex fate Cr(III). A bacterial enzyme system, using NADH the reductant, converts soluble NAD+−Cr(III) complex, and cytochrome c-mediated produces c−Cr(III) adducts. In this study, in presence cellular organic metabolites formed both...

Although several X-ray structures have been determined for the mitochondrial cytochrome (cyt) bc1 complex, none yet shows position of substrate, ubiquinol, in quinol oxidase (Qo) site. In this study, interaction molecular oxygen with reactive intermediate Qo semiquinone is used to probe It has known some time that partial turnover cyt complex presence antimycin A, a Qi site inhibitor, results accumulation at site, which can reduce O2 superoxide (O2•-). was more recently shown myxothiazol,...

The structure of the K262R genetic variant human cytochrome P450 2B6 in complex with inhibitor 4-(4-chlorophenyl)imidazole (4-CPI) has been determined using X-ray crystallography to 2.0-A resolution. Production diffraction quality crystals was enabled through a combination protein engineering, chaperone coexpression, modifications purification protocol, and use unique facial amphiphiles during crystallization. 2B6-4-CPI is virtually identical rabbit 2B4 bound same respect arrangement...

Human cytochrome P450 3A4 (CYP3A4) metabolizes a significant portion of clinically relevant drugs and often exhibits complex steady-state kinetics that can involve homotropic heterotropic cooperativity between bound ligands. In previous studies, the hydroxylation sedative midazolam (MDZ) exhibited via decrease in ratio 1′-OH-MDZ to 4-OH-MDZ at higher drug concentrations. this study, MDZ with antiepileptic carbamazepine (CBZ) characteristic decreases ratios. To unravel structural basis...

Roadway mortality increased during COVID-19, reversing a multi-decade downward trend. The Fatality Analysis Reporting System (FARS) was used to examine contributing factors pre-COVID-19 and in the COVID-19 era using five pillars of Safe framework: (1) road users; (2) vehicles; (3) roadways; (4) speed; (5) post-crash care. Two study time periods were matched control for seasonality differences (n = 1725, 1 April 2018-31 December 2019) 2010, 2020-31 2021) with three-month buffer period between...

Human cytochrome P450 (CYP) 3A4 catalyzes the oxygen-dependent metabolism of greater than 60% known drugs. CYP3A4 binds multiple ligands simultaneously, and this contributes to complex allosteric kinetic behavior. Substrates that bind enzyme change ferric spin state equilibrium heme, which can be observed by optical absorbance electron paramagnetic resonance (EPR) spectroscopy. The ligand-dependent has not been quantitatively understood for any exhibit binding. substrate testosterone (TST)...

The structurally related glutathione S-transferase isoforms GSTA1-1 and GSTA4-4 differ greatly in their relative catalytic promiscuity. is a highly promiscuous detoxification enzyme. In contrast, exhibits selectivity for congeners of the lipid peroxidation product 4-hydroxynonenal. contribution protein dynamics to promiscuity has not been studied. Therefore, hydrogen/deuterium exchange mass spectrometry (H/DX) fluorescence lifetime distribution analysis were performed with S-transferases...

Drug-drug interactions (DDIs) and associated toxicity from cardiovascular drugs represents a major problem for effective co-administration of therapeutics. A significant amount drug DDIs occurs because multiple binding to the efflux transporter P-glycoprotein (Pgp), which is particularly problematic their relatively low therapeutic indexes. The calcium channel antagonist, verapamil cardiac glycoside, digoxin, exhibit with Pgp through non-competitive inhibition digoxin transport, leads...

Recent studies have indicated that CYP3A4 exhibits non-Michaelis−Menten kinetics for numerous substrates. Both homo- and heterotropic activation been reported, kinetic models suggested multiple substrates within the active site. We provide some of first physicochemical data supporting hypothesis allosteric substrate binding Midazolam (MDZ) is metabolized by to two hydroxylated metabolites, 1'- 4-hydroxymidazolam. Incubations using purified MDZ showed both α-naphthoflavone (α-NF) testosterone...

Acetaminophen (N-acetyl-p-aminophenol, APAP) is a commonly used analgesic/antipyretic. When oxidized by P450, toxic APAP metabolite generated. Human P450 3A4 was expressed in Escherichia coli, purified, and reconstituted using artificial liposomes. Oxidation of 3A4, as detected the formation its glutathione adduct, found to exhibit negative homotropic cooperativity with Hill coefficient 0.7. In presence caffeine, observed kinetics were close classical Michaelis–Menten approaching 1. order...

Crystal structures of the xenobiotic metabolizing cytochrome P450 2B4 have demonstrated markedly different conformations in presence imidazole inhibitors or absence ligand. However, knowledge plasticity enzyme solution has remained scant. Thus, hydrogen-deuterium exchange mass spectrometry (DXMS) was utilized to probe ligand-free and complex with 4-(4-chlorophenyl)imidazole (4-CPI) 1-biphenyl-4-methyl-1H-imidazole (1-PBI). The results DXMS indicate that binding 4-CPI slowed rate over B'-...

The ARIADNE project is developing innovative optical readout technologies for two-phase liquid Argon time projection chambers (LArTPCs). Optical presents an exciting alternative to the current paradigm of charge readout. simple, scalable and cost effective. This paper first demonstration 3D TPC, using CF4 gas as a proof principle. Both cosmic rays Americium-241 alpha source have been imaged in 100 mbar CF4. A single-photon sensitive camera was developed by combining Timepix3 (TPX3) based...

Abstract Argon gas doped with 1% wavelength-shifter (CF 4 ) has been employed in an optical time projection chamber (OTPC) to image cosmic radiation. We present results obtained during the system commissioning, performed two stacked glass thick gaseous electron multipliers (THGEMs) and electron-multiplying charge coupled device (EMCCD camera) at 1 bar. Preliminary estimates indicate that combined gain was of order 10 6 (ph/e), producing sharp high-contrast raw images without resorting any...

Thrombocytopenia is a common occurrence in sick newborn babies. Despite this, platelet production the has rarely been assessed, principally because of difficulties obtaining bone marrow, especially on serial basis. We have developed two miniaturized assay systems to study megakaryocyte (MK) progenitor cell differentiation, from BFU-MK and CFU-MK mature MK, by culturing mononuclear cells purified 0.5-1 ml neonatal peripheral blood. were assayed agar, whilst total cultured MK precursors...

Prior X-ray crystal structures of rabbit cytochrome P450 2B4 (2B4) in complexes with various imidazoles have demonstrated markedly different enzyme conformations depending on the size inhibitor occupying active site. In this study, were determined antiplatelet drugs clopidogrel and ticlopidine, which expected to greater freedom movement binding pocket. Ticlopidine could be modeled into electron density maps two distinct orientations, both are consistent metabolic data gathered other...

Cytochrome b5 (cyt b5) is one of the key components in microsomal cytochrome P450 monooxygenase system. Consensus has not been reached about underlying mechanism cyt modulation CYP catalysis. Both and apo are reported to stimulate activity several isoforms. In this study, surface interactions both holo with CYP3A4 were investigated compared for first time. Chemical cross-linking coupled mass spectrometric analysis was used identify potential electrostatic between protein surfaces....

A combined structural and computational analysis of rabbit cytochrome P450 2B4 covalently bound to the mechanism-based inactivator tert-butylphenylacetylene (tBPA) has yielded insight into how enzyme retains partial activity. Since conjugation tBPA modifies a highly conserved active site residue, residual activity tBPA-labeled observed in previous studies was puzzling. Here we describe first crystal structures modified mammalian P450, which show an oxygenated metabolite conjugated Thr 302...

4-Hydroxy-2-nonenal (HNE) is a toxic aldehyde generated during lipid peroxidation and has been implicated in variety of pathological states associated with oxidative stress. Glutathione S-transferase (GST) A4-4 recognized as one the predominant enzymes responsible for metabolism HNE. However, substrate product stereoselectivity remain to be fully explored. The results from formation assay indicate that hGSTA4-4 exhibits modest preference biotransformation S-HNE presence both enantiomers....