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Laboratory studies of the disposition and toxicity of hydroxylated polychlorinated biphenyl (OH-PCB) metabolites are challenging because authentic analytical standards for most unknown OH-PCBs are not available. To assist with the characterization of these OH-PCBs (as methylated derivatives), we developed machine learning-based models with multiple linear regression (MLR) or random forest regression (RFR) to predict the relative retention times (RRT) and MS/MS responses of methoxylated (MeO-)PCBs on a gas chromatograph-tandem mass spectrometry system. The final MLR model estimated the retention times of MeO-PCBs with a mean absolute error of 0.55 min (n = 121). The similarity coefficients cos θ between the predicted (by RFR model) and experimental MS/MS data of MeO-PCBs were >0.95 for 92% of observations (n = 96). The levels of MeO-PCBs quantified with the predicted MS/MS response factors approximated the experimental values within a 2-fold difference for 85% of observations and 3-fold differences for all observations (n = 89). Subsequently, these model predictions were used to assist with the identification of OH-PCB 95 or OH-PCB 28 metabolites in mouse feces or liver by suggesting candidate ranking information for identifying the metabolite isomers. Thus, predicted retention and MS/MS response data can assist in identifying unknown OH-PCBs.

The secondary metabolite pseudopyronine B, isolated from

Plant-derived cytochrome P450-dependent flavonoid 3'-hydroxylases are the rate-limiting enzymes in flavonoid biosynthesis. In this study, the large component (HpaB) of a prokaryotic 4-hydroxyphenylacetate (4-HPA) 3-hydroxylase was engineered for efficient 3'-hydroxylation of naringenin. First, we selected four HpaBs through database search and phylogenetic analysis and compared their catalytic activities toward 4-HPA and naringenin. HpaB from

We explored the most expedient pathway for phenolic compound preparation using a combination of arylboronic acids, a green oxidant (H2O2) and a catalytic amount of readily available medicinal materials (TYLENOL® and ASPIRIN®). The arylboronic acids were successfully transformed into the corresponding phenols in high yields under metal- and base-free aqueous aerobic conditions. We demonstrated that enhanced availability and sustainability are some advantages associated with the use of medicinal supports.

The photoredox-catalyzed radical difluoroalkylation/cyclization/hydroxylation cascade reaction of various 2-bromo-2,2-difluoro

A novel route has been described for C-H borylation and hydroxylation of benzenethiols directed by adamantane-1-carbonyl using BBr

Ferulic acid (FA) is a natural methylated phenolic acid which represents various bioactivities. Bioproduction of FA suffers from insufficient methyl donor supplement and inefficient hydroxylation. To overcome these hurdles, we first activate the S-adenosylmethionine (SAM) cycle in E. coli by using endogenous genes to supply sufficient methyl donor. Then, a small protein Fre is introduced into the pathway to efficiently regenerate FADH

Lower chlorinated polychlorinated biphenyls (LC-PCBs) and their metabolites make up a class of environmental pollutants implicated in a range of adverse outcomes in humans; however, the metabolism of LC-PCBs in human models has received little attention. Here we characterize the metabolism of PCB 2 (3-chlorobiphenyl), an environmentally relevant LC-PCB congener, in HepG2 cells with

Nitrilases capable of performing hydroxylation of 2-chloroisonicotinonitrile to 2-chloroisonicotinic acid were screened, and ES-NIT-102 was the best nitrilase for said biotransformation. Nitrilase was immobilized as cross linked enzyme aggregates (nitrilase-CLEAs) by fractional precipitation with iso-propanol, and cross linked with glutaraldehyde. The nitrilase-CLEAs prepared with optimized 35 mM glutaraldehyde for 120 min cross linking time had 82.36 ± 4.45% residual activity, and displayed type-II structural CLEAs formation as confirmed by particle size, SEM, FTIR, and SDS-PAGE analysis. Nitrilase-CLEAs had superior pH and temperature stability, showed a shift in optimal temperature by 5 °C, and retained nearly 1.5 to 1.7 folds activity over free nitrilase at 50 °C and 55 °C after more than 9 h incubation. Nitrilase-CLEAs showed reduced affinity and decreased conversion of substrate as indicated by slightly higher K

Herein, hydroxylation activities at the 6β-position and 21-position of progesterone mediated by human cytochrome P450 (CYP) 2D6 and its variants and the effects of psychotropic drugs on these hydroxylation activities were compared to clarify whether CYP2D6 polymorphisms and psychotropic drugs impact neurosteroid levels in the brain.Progesterone was incubated with CYP2D6.1, CYP2D6.2 (Arg296Cys, Ser486Thr), CYP2D6.10 (Pro34Ser, Ser486Thr), and CYP2D6.39 (Ser486Thr) in the absence or presence of typical psychotropic drugs (fluvoxamine, fluoxetine, paroxetine, fluphenazine, and milnacipran) and endogenous steroids (testosterone and cortisol). Then, 6β- and 21-hydroxyprogesterone levels were determined by high-performance liquid chromatography.Although the Michaelis-Menten constants (KThese results suggest that CYP2D6 polymorphism can affect the stimulation/inhibition of progesterone 21-hydroxylation.

Disruption of the blood-urine barrier can result in acute or chronic inflammatory bladder injury. Activation of the oxygen-regulated hypoxia-inducible factor (HIF) pathway has been shown to protect mucosal membranes by increasing the expression of cytoprotective genes and by suppressing inflammation. The activity of HIF is controlled by prolyl hydroxylase domain (PHD) dioxygenases, which have been exploited as therapeutic targets for the treatment of anemia of chronic kidney disease. Here, we established a mouse model of acute cyclophosphamide (CYP)-induced blood-urine barrier disruption associated with inflammation and severe urinary dysfunction to investigate the HIF-PHD axis in inflammatory bladder injury. We found that systemic administration of dimethyloxalylglycine or molidustat, two small-molecule inhibitors of HIF-prolyl hydroxylases, profoundly mitigated CYP-induced bladder injury and inflammation as assessed by morphological analysis of transmural edema and urothelial integrity and by measuring tissue cytokine expression. Void spot analysis to examine bladder function quantitatively demonstrated that HIF-prolyl hydroxylase inhibitor administration normalized micturition patterns and protected against CYP-induced alteration of urinary frequency and micturition patterns. Our study highlights the therapeutic potential of HIF-activating small-molecule compounds for the prevention or therapy of bladder injury and urinary dysfunction due to blood-urine barrier disruption. NEW & NOTEWORTHY Disruption of the blood-urine barrier can result in acute or chronic inflammatory bladder injury. Here, we demonstrate that pharmacological inhibition of hypoxia-inducible factor (HIF)-prolyl hydroxylation prevented bladder injury and protected from urinary dysfunction in a mouse model of cyclophosphamide-induced disruption of the blood-urine barrier. Our study highlights a potential role for HIF-activating small-molecule compounds in the prevention or therapy of bladder injury and urinary dysfunction and provides a rationale for future clinical studies.

Exposure to polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (OH-PCBs) has been implicated in neurodevelopmental disorders. However, the distribution of PCBs and OH-PCBs in the human brain has not been characterized. This study investigated the age-, sex-, and brain region-specific distribution of all 209 PCBs using gaschromatography-tandem mass spectrometry (GC-MS/MS) in neonatal (

Polychlorinated biphenyls (PCBs) can be metabolized into hydroxylated PCBs (OH-PCBs) that exhibit greater toxicity than their parent compounds. In particular, 2,2',4,5,5'-pentachlorobiphenyl (PCB 101) is commonly found in chicken feeds and breeding environments, although information on the biotransformation of this PCB in chickens is lacking. In this study, the hydroxylation metabolization of PCB 101 was assessed based on in vitro trials with Sanhuang chicken liver microsomes and in vivo experiments with Hy-Line Brown hens. The

High-valent metal-oxo species play critical roles in enzymatic catalysis yet their properties are still poorly understood. In this work we report a combined experimental and computational study into biomimetic iron(IV)-oxo and iron(III)-oxo complexes with tight second-coordination sphere environments that restrict substrate access. The work shows that the second-coordination sphere slows the hydrogen atom abstraction step from toluene dramatically and the kinetics is zeroth order in substrate. However, the iron(II)-hydroxo that is formed has a low reduction potential and hence cannot do OH rebound favorably. The tolyl radical in solution then reacts further with alternative reaction partners. By contrast, the iron(IV)-oxo species reacts predominantly through OH rebound to form alcohol products. Our studies show that the oxidation state of the metal influences reactivities and selectivities with substrate dramatically and that enzymes will likely need an iron(IV) center to catalyze C−H hydroxylation reactions.

Nonheme iron halogenases are unique enzymes in nature that selectively activate an aliphatic C-H bond of a substrate to convert it into C-X (X = Cl/Br, but not F/I). It is proposed that they generate an FeIII(OH)(X) intermediate in their catalytic cycle. The analogous FeIII(OH) intermediate in nonheme iron hydroxylases transfers OH• to give alcohol product, whereas the halogenases transfer X• to the carbon radical substrate. There remains significant debate regarding what factors control their remarkable selectivity of the halogenases. The reactivity of the complexes FeIII(BNPAPh2O)(OH)(X) (X = Cl, Br) with a secondary carbon radical (R•) is described. It is found that X• transfer occurs with a secondary carbon radical, as opposed to OH• transfer with tertiary radicals. Comprehensive computational studies involving density functional theory were carried out to examine the possible origins of this selectivity. The calculations reproduce the experimental findings, which indicate that halogen transfer is not observed for the tertiary radicals because of a nonproductive equilibrium that results from the endergonic nature of these reactions, despite a potentially lower reaction barrier for the halogenation pathway. In contrast, halogen transfer is favored for secondary carbon radicals, for which the halogenated product complex is thermodynamically more stable than the reactant complex. These results are rationalized by considering the relative strengths of the C-X bonds that are formed for tertiary versus secondary carbon centers. The computational analysis also shows that the reaction barrier for halogen transfer is significantly dependent on secondary coordination sphere effects, including steric and H-bonding interactions.

Catechol pollutants (CATPs) serving as chelating agents could coordinate with many metal ions to form various CATPs-metal complexes. Little information is available on the effects of complexation of metal ions on CATPs degradation. This work presents a systematical study of •OH-mediated degradation of catechol and catechol-metal complexes over the whole pH range in advanced oxidation processes (AOPs). Results show that the pH-dependent complexation of metal ions (Zn2+, Cu2+, Ti4+ and Fe3+) promotes the deprotonation of catechol under neutral and even acidic conditions. The radical adduct formation (RAF) reactions are both thermodynamically and kinetically favorable for all dissociation and complexation species, and OH/ O− group-containing C positions are more vulnerable to •OH attack. The kinetic results show that the complexation of the four metal ions offers a wide pH range of effectiveness for catechol degradation. At pH 7, the apparent rate constant (kapp) values for different systems follow the order of catechol+Ti4+ ≈ catechol+Zn2+ > catechol+Cu2+ > catechol+Fe3+ > catechol. The mechanistic and kinetic results would greatly improve our understanding of the degradation of CATPs-metal and other organics-metal complexes in AOPs. The toxicity assessment indicates that the •OH-based AOPs have the ability for decreasing the toxicity and increasing the biodegradability during the processes of catechol degradation.

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Utilization of mononuclear iron- and 2-oxoglutarate-dependent (Fe/2OG) enzymes to enable C-H bond functionalization is a widely used strategy to diversify the structural complexity of natural products. Besides those well-studied reactions including hydroxylation, epoxidation, and halogenation, in the biosynthetic pathway of dehydrofosmidomycin, an Fe/2OG enzyme is reported to catalyze desaturation, alkyl chain elongation, along with demethylation in which trimethyl-2-aminoethylphosphonate is converted into methyldehydrofosmidomycin. How this transformation takes place is largely unknown. Herein, we characterized the reactive species, revealed the structure of the reaction intermediate, and used mechanistic probes to investigate the reaction pathway and mechanism. These results led to the elucidation of a two-step process in which the first reaction employs a long-lived Fe(IV)-oxo species to trigger C═C bond installation. During the second reaction, the olefin installed in situ enables C-C bond formation that is accompanied with a C-N bond cleavage and hydroxylation to furnish the alkyl chain elongation and demethylation. This work expands the reaction repertoire of Fe/2OG enzymes by introducing a new pathway to the known C-C bond formation mechanisms utilized by metalloenzymes.

Flavonols have been studied extensively because of their interesting biological activities and excited-state intramolecular proton transfer (ESIPT) behavior. Galangin, kaempferol, quercetin, and myricetin are structurally related flavonols that differ only in the number of B-ring hydroxyl substituents. In this work, we have carried out a detailed study on the photophysical behavior of these structurally related flavonols in various solvents and a 1,2-dimyristoyl

3-Alkyl-3-hydroxyoxindoles, a subclass of oxindole products, have antioxidant, neuroprotective, anticancer, and anti-HIV activities. In this study, a green and economical protocol for the synthesis of 3-alkyl-3-hydroxyoxindoles is developed for the first time via α-alkylation-α-hydroxylation of oxindole with benzyl alcohols without using any transition-metal catalysts in yields of 29-93%.

Itraconazole (ITZ) is an important drug in the treatment of superficial and deep mycoses in dogs. Its primary metabolite is hydroxy-itraconazole, which has antifungal activity similar to the parent compound. The purpose of this study was to identify the cytochrome P450 enzyme (CYP) isoform(s) responsible for ITZ hydroxylation in canine liver. Reaction kinetics for ITZ hydroxylation were determined in a panel of canine recombinant CYPs and dog liver microsomes (DLMs). Findings were confirmed using CYP isoform-specific inhibitors in rCYPs and DLMs. In rCYP experiments, CYP2D15 and CYP3A12 had highest activity for ITZ hydroxylation. In inhibitor experiments, quinidine and erythromycin inhibited ITZ hydroxylation in CYP2D15 and CYP3A12, respectively, in an isoform-specific manner. In DLMs, quinidine and erythromycin combined inhibited ITZ hydroxylation more than erythromycin alone but not quinidine alone. However, this may be related to inhibitor potency rather than the contribution of the individual CYP isoforms to the reaction. These findings support a role for CYP2D15 and CYP3A12 in ITZ biotransformation in canine liver.

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The difficulty in Fe(III)/Fe(II) conversion in the Fe(III)/peroxymonosulfate (PMS) process limits its efficiency and application. Herein, L-cysteine (Cys), a green natural organic ligand with reducing capability, was innovatively introduced into Fe(III)/PMS to construct an excellent Cys/Fe(III)/PMS process. The Cys/Fe(III)/PMS process, at room temperature, can degrade a variety of organic contaminants, including dyes, phenolic compounds, and pharmaceuticals. In subsequent experiments with acid orange 7 (AO7), the AO7 degradation efficiency followed pseudo-first-order kinetic which exhibited an initial “fast stage” and a second “slow stage”. The rate constant values ranged depending on the initial Cys, Fe(III), PMS, and AO7 concentrations, reaction temperature, and pH values. In addition, the presence of Cl−, NO3−, and SO42− had negligible impact while HCO3− and humic acid inhibited the degradation of AO7. Furthermore, radical scavenger experiments and methyl phenyl sulfoxide (PMSO) transformation assay indicated that sulfate radical, hydroxyl radical, and ferryl ion (Fe(IV)) were the dominant reactive species involved in the Cys/Fe(III)/PMS process. Finally, based on the results of gas chromatography-mass spectrometry, several AO7 degradation pathways, including N=N cleavage, hydroxylation, and ring opening were proposed. This study provided a new insight to improve the efficiency of Fe(III)/PMS process by accelerating Fe(III)/Fe(II) cycle with Cys.

Cytochrome P450 3A (CYP3A), the most important class of drug-metabolizing enzymes, participates in the metabolism of half of clinically used drugs. The CYP3A index reactions of dogs, one of the most widely used preclinical nonrodent species, are still poorly understood. This work evaluated the activity and selectivity of 10 CYP3A index reactions, including midazolam (MDZ) 1'- and 4-hydroxylation, alprazolam (APZ) and triazolam (TRZ)

Aerobic α-hydroxylation of α-methylene esters has proven challenging due to overoxidation and hydrolysis of the materials. In this article, KO

The disposition of the hepatoselective ACC inhibitor PF-05221304 (Clesacostat) was studied after a single 50-mg oral dose of [14C]-PF-05221304 to healthy human subjects.Mass balance was achieved with 89.9% of the administered dose recovered in urine and faeces, over the 11-day study period. The total administered radioactivity excreted in faeces and urine was 81.7 and 8.2%, respectively. Unchanged PF-05221304 accounted for 35.6% of the radioactive dose in faeces, suggesting ∼64% of the administered dose was absorbed.PF-05221304 was principally metabolised via oxidative and reductive pathways involving: (a) N-dealkylation, (b) isopropyl group monohydroxylation to yield enantiomeric metabolites (M2a and M2b), (c) hydroxylation on the 3-azaspiro[5.5]undecan-8-one moiety to metabolites M5 and 519c, and (d) carbonyl group reduction to enantiomeric alcohol metabolites M3, and M4. Secondary metabolites (521a, 521b, and 533), derived from a combination of oxidation and reduction of the primary metabolites accounted for ∼14.8% of the dose. In plasma, unchanged PF-05221304 represented 96.1% circulating radioactivity. Metabolites M1, M2b, and M2a represented 1.94, 1.76, and 0.18% of circulating radioactivity, respectively.Overall, these data suggest that PF-05221304 is well absorbed in humans and eliminated largely via phase I metabolism. The disposition of the hepatoselective ACC inhibitor PF-05221304 (Clesacostat) was studied after a single 50-mg oral dose of [14C]-PF-05221304 to healthy human subjects. Mass balance was achieved with 89.9% of the administered dose recovered in urine and faeces, over the 11-day study period. The total administered radioactivity excreted in faeces and urine was 81.7 and 8.2%, respectively. Unchanged PF-05221304 accounted for 35.6% of the radioactive dose in faeces, suggesting ∼64% of the administered dose was absorbed. PF-05221304 was principally metabolised via oxidative and reductive pathways involving: (a) N-dealkylation, (b) isopropyl group monohydroxylation to yield enantiomeric metabolites (M2a and M2b), (c) hydroxylation on the 3-azaspiro[5.5]undecan-8-one moiety to metabolites M5 and 519c, and (d) carbonyl group reduction to enantiomeric alcohol metabolites M3, and M4. Secondary metabolites (521a, 521b, and 533), derived from a combination of oxidation and reduction of the primary metabolites accounted for ∼14.8% of the dose. In plasma, unchanged PF-05221304 represented 96.1% circulating radioactivity. Metabolites M1, M2b, and M2a represented 1.94, 1.76, and 0.18% of circulating radioactivity, respectively. Overall, these data suggest that PF-05221304 is well absorbed in humans and eliminated largely via phase I metabolism.

Based on single metal-organic framework (MOF) composite catalyst ZIF-67/g-C3N4 (ZG), the composite catalysts ZIF-67/MOF-74(Ni)/g-C3N4 (ZNG) and ZIF-67/MIL-100(Fe)/g-C3N4 (ZMG) with double MOFs were synthesized, used to effectively activate peroxymonosulfate (PMS) for degrade venlafaxine (VEN). Various characterization methods (XRD, FT-IR, Raman, SEM, EDS, TEM and TG) showed that ZIF-67 and g-C3N4; ZIF-67, MOF-74(Ni) and g-C3N4; as well as ZIF-67, MIL-100(Fe) and g-C3N4 successfully formed heterostructures. The series of catalytic degradation results showed that within 120 min, the degradation rate of VEN by ZMG achieved 100% and the mineralization rate reached 51.32%. The removal rate of VEN by ZNG was 91.38%, while that by ZG was only 27.75%. Free radical quenching tests and EPR further confirmed the production of •OH and SO4•-, which could be conducive to the degradation of VEN. The mechanism analysis of PMS activation confirmed that the interaction of ≡Fe2+/≡Co3+ was stronger than that of ≡Ni2+/≡Co3+, and it was an important driving force to significantly enhance the synergistic effect. Finally, Gauss theory calculation and HPLC-MS/MS were used to analyze the intermediate products of VEN. It was verified that the main chemical reactions in the degradation process of VEN were hydroxylation, dehydration, demethylation and tertiary amine substitution.

In a previous study, we identified CYP5035S7 of the white-rot fungus Polyporus arcularius with a broad activity towards monoterpenes such as p-cymene. Therefore, in this study we aimed at further exploring the substrate scope of detoxifying CYP5035S7 towards terpenes and semi-preparatively isolating some of the products via whole-cell biotransformation, in order to obtain information about the enzyme's reactivity. We noticed a clear preference for the monoterpene skeleton and elucidated a distinct regioselectivity pattern based on key structural and electronic features of its substrates. This study illustrates how minimal characterisation effort may already suffice to provide vital information on enzymatic reactivity by the comparison of structural derivatives.

Intramolecular phenol coupling reactions of alkaloids can lead to active metabolites catalyzed by the mammalian cytochrome P450 enzyme (P450); however, the mechanistic knowledge of such an "unusual" process is lacking. This work performs density functional theory computations to reveal the P450-mediated metabolic pathway leading from

The widely used alkylating agent cyclophosphamide (CY) has substantive interpatient variability in the area under the curve (AUC) of it and its metabolites. Numerous factors may influence the drug-metabolizing enzymes that metabolize CY to 4-hydroxycyclophosphamide (4HCY), the principal precursor to CY's cytotoxic metabolite. We sought to identify endogenous metabolomics compounds (EMCs) associated with 4HCY formation clearance (ratio of 4HCY/CY AUC) using global metabolomics. Patients who undergo hematopoietic cell transplantation receiving post-transplant CY (PT-CY) were enrolled, cohort 1 (n = 26) and cohort 2 (n = 25) donating longitudinal blood samples before they started HCT (pre-HCT), before infusion of the donor allograft (pre-graft), before the first dose of PT-CY (pre-CY), and 24 h after the first dose of PT-CY (24-h post-CY), which is also immediately before the second dose of CY. A total of 512 and 498 EMCs were quantitated in two cohorts, respectively. Both univariate linear regression with false discovery rate (FDR), and pathway enrichment analyses using a global association test were performed. At the pre-CY time point, no EMCs were associated at FDR less than 0.1. At pre-HCT, cohort 1 had one EMC (levoglucosan) survive the FDR threshold. At pre-graft, cohort 1 and cohort 2 had 20 and 13 EMCs, respectively, exhibiting unadjusted p values less than 0.05, with the only EMCs having an FDR less than 0.1 being two unknown EMCs. At 24-h post-CY, there were three EMCs, two ketones, and threitol, at FDR less than 0.1 in cohort 2. These results demonstrate the potential of pharmacometabonomics, but future studies in larger samples are needed to optimize CY.

Cytochrome P450 peroxygenases use hydrogen peroxide to hydroxylate long-chain fatty acids by bypassing the use of O

CYP105A1 from Streptomyces griseolus converts vitamin D3 to its biologically active form, 1α,25-dihydroxy vitamin D3. R73A/R84A mutation enhanced the 1α- and 25-hydroxylation activity for vitamin D3, while M239A mutation generated the 1α-hydroxylation activity for vitamin D2. In this study, the stability of six CYP105A1 enzymes, including 5 variants (R73A/R84A, M239A, R73A/R84A/M239A (=TriA), TriA/E90A, and TriA/E90D), was examined. Circular dichroism analysis revealed that M239A markedly reduces the enzyme stability. Protein fluorescence analysis disclosed that these mutations, especially M239A, induce large changes in the local conformation around Trp residues. Strong stabilizing effect of glycerol was observed. Nondenaturing PAGE analysis showed that CYP105A1 enzymes are prone to self-association. Fluorescence analysis using a hydrophobic probe 8-anilino-1-naphthalenesulfonic acid suggested that M239A mutation enhances self-association and that E90A and E90D mutations, in cooperation with M239A, accelerate self-association with little effect on the stability.

Hyaluronan-collagen composites have been employed in numerous biomedical applications. Understanding the interactions between hyaluronan and collagen is particularly important in the context of joint cartilage function and the treatment of joint diseases. Many factors affect the affinity of collagen for hyaluronan. One of the important factors is the ratio of 3- or 4-hydroxy proline to proline residues. This article presents the results from molecular dynamics calculations of HA-collagen type II interactions with hyaluronan. The applied protocol employed docking and geometry optimization of complexes built using collagen structures with different numbers of hydroxyl groups attached to proline moieties. It was established that the hydroxyproline/proline ratio affects both structural and energetic features of the collagen-hyaluronan complex. Proline hydroxylation was found to significantly influence the number of all identified types of molecular forces, hydrophobic interactions, water bridges and hydrogen bonds, which can be formed between collagen and hyaluronan. Importantly, an increase in the hydroxyproline/proline ratio in the collagen chain increases the binding affinity for hyaluronan. This is illustrated by the linear correlation between the binding free energy and the hydroxylation degree. A comparison of the results obtained for 3 and 4 hydroxylation of proline indicates that the hydroxyl group attachment position plays a minor role in complex stabilization. However, a slightly stronger affinity was observed for 4 hydroxylation. In order to evaluate the effect of the aqueous environment on the collagen-hyaluronan complex stability, the enthalpic and entropic contributions to the free energy of solvation were analyzed.

Maryam Zarghami Dehaghani,1 Farrokh Yousefi,2 Farzad Seidi,1 S Mohammad Sajadi,3,4 Navid Rabiee,5 Sajjad Habibzadeh,6 Amin Esmaeili,7 Amin Hamed Mashhadzadeh,8 Christos Spitas,8 Ebrahim Mostafavi,9,10 Mohammad Reza Saeb11 1Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources and Joint International Research Lab of Lignocellulosic Functional Materials, Nanjing Forestry University, Nanjing, 210037, People’s Republic of China; 2Department of Physics, University of Zanjan, Zanjan, 45195-313, Iran; 3Department of Nutrition, Cihan University-Erbil, Erbil, Iraq; 4Department of Phytochemistry, SRC, Soran University, Soran, Iraq; 5Department of Physics, Sharif University of Technology, Tehran, Iran; 6Department of Chemical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, 1591639675, Iran; 7Department of Chemical Engineering, School of Engineering Technology and Industrial Trades, College of the North Atlantic — Qatar, Doha, Qatar; 8Mechanical and Aerospace Engineering, School of Engineering and Digital Sciences, Nazarbayev University, Nur-Sultan, 010000, Kazakhstan; 9Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA; 10Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA; 11Department of Polymer Technology, Faculty of Chemistry, Gdańsk University of Technology, Gdańsk, 80-233, PolandCorrespondence: Amin Hamed MashhadzadehMechanical and Aerospace Engineering, School of Engineering and Digital Sciences, Nazarbayev University, Nur-Sultan, 010000, KazakhstanEmail amin.hamed.m@gmail.com; amin.hamedmashhadzadeh@nu.edu.kzEbrahim MostafaviStanford Cardiovascular Institute, Stanford University School of Medicine, Biomedical Innovation Building, 240 Pasteur Drive, Palo Alto, Stanford, CA 94304, USAEmail ebimsv@Stanford.edu; ebi.mostafavi@gmail.comIntroduction: Carbon nanotubes (CNTs) have been widely employed as biomolecule carriers, but there is a need for further functionalization to broaden their therapeutic application in aqueous environments. A few reports have unraveled biomolecule–CNT interactions as a measure of response of the nanocarrier to drug-encapsulation dynamics.Methods: Herein, the dynamics of encapsulation of the antimicrobial peptide HA-FD-13 (accession code 2L24) into CNTs and hydroxylated CNTs (HCNTs) is discussed.Results: The van der Waals (vdW) interaction energy of CNT–peptide and HCNT–peptide complexes decreased, reaching − 110.6 and − 176.8 kcal.Mol− 1, respectively, once encapsulation of the peptide inside the CNTs had been completed within 15 ns. The free energy of the two systems decreased to − 43.91 and − 69.2 kcal.Mol− 1 in the same order.Discussion: The peptide was encased in the HCNTs comparatively more rapidly, due to the presence of both electrostatic and vdW interactions between the peptide and HCNTs. However, the peptide remained encapsulated throughout the vdW interaction in both systems. The negative values of the free energy of the two systems showed that the encapsulation process had occurred spontaneously. Of note, the lower free energy in the HCNT system suggested more stable peptide encapsulation.Keywords: drug delivery, hydroxylation, carbon nanotubes, molecular dynamic simulation, encapsulation, antimicrobial peptide

Understanding the phase regulation mechanism of BaTiO3 synthesized by a hydrothermal method is a complicated and challenging task. Here, we successfully prepared cubic and tetragonal BaTiO3 single nanocrystals by changing the ratio of water and ethanol in the solvent. We confirm that the BaTiO3 phase is mainly affected by the hydroxylation process due to the reaction with solvent. In particular, ethanol can be catalytically oxidized by titanium atoms, cause BaTiO3 hydroxylation and promote the formation of a cubic phase. In the mixed solution of ethanol and water, the hydroxylation process is suppressed, which facilitates the formation of the tetragonal phase. The relationship framework between the solvent ratio, phase structure and hydroxyl defects of BaTiO3 is established. Tetragonal BaTiO3 with fewer hydroxyl defects can promote charge transfer and surface reaction after polarization, thereby enhancing their photoelectric catalytic performance. This work provides references for the controllable synthesis of ferroelectric nanocrystals by hydrothermal methods and new insight for the utilization of polarization in photoelectrocatalysis applications.

The biomimetic iron(ii)-hydroperoxo species prefers to decay to an oxo-iron(iv)-hydroxy one to exert substrate oxidations and ligand self-hydroxylation.

Nowadays, the harm of antibiotics residues in environments to human health and ecological safety has been causing more and more attention. In this paper, a biochar based iron material (MBC) was used to activate persulfate (PS) for the removal of sulfadiazine (SDZ) from aqueous solution. Experiment results indicate that the degradation and mineralization of SDZ by MBC/PS system reached 91.79 and 60 % within 60 min under the optimal reaction conditions, respectively. MBC/PS system exhibited a better performance on SDZ removal compared with MBC/H2O2 system. The addition of Cu2+ ion could enhance the degradation of SDZ by MBC/PS system. PO43-, Cl- and SO42- had a certain degree of inhibitory effect on the SDZ degradation. Both radicals and non-radical species such as SO4•-, •OH and 1O2 participated in the degradation reaction of SDZ by MBC/PS system, but •OH was the main radical species responsible for SDZ degradation. The liquid chromatograph-mass spectrometer (LC-MS) technique was used to identify the intermediate products of SDZ, and it was proposed that the degradation of SDZ might be achieved through hydrolyzation, hydroxylation, deamination and amino-oxidization processes. A possible reaction mechanism involving a synergistic effect between PS homogeneous and heterogeneous activation processes as well as both radicals and non-radicals reactions was finally proposed.

An in-depth study of the degradation of bisphenol S (BPS) by both single-walled carbon nanotubes and heat activated persulfate (PS) was conducted in detail. The effects of various factors, namely, material dosage, initial substrate concentration, initial pH and the water matrix, on the removal of BPS were evaluated, and 10 μM BPS was completely removed in 90 min under the optimal conditions of [BPS]0 : [PS]0 = 1 : 100, T = 25 °C, pH0 = 7.0, and [N-SWCNTs] = 20 mg L−1. Fast removal of BPS was also obtained when the reaction temperature reached 65 °C without catalyst. There were 15 intermediates identified in total, and hydroxylation, sulfate addition, carboxylation, S–C bond cleavage and polymerization were considered to be the main transformation pathways of BPS in both the systems based on LC-MS analysis. The discrepancy in the proportion of hydroxyl and sulfate radicals involved in the two systems led to different distribution and abundance of the observed products. According to quantum chemical calculations, hydroxylation, hydrogen atom abstraction and sulfate addition occurred as the initial reactions between radicals and BPS. Furthermore, the intrinsic reaction coordinate (IRC) paths of the generated primary products were obtained using the program Gaussian 09. Low reaction barriers (22.20, 25.06 and 13.85 kJ mol−1, respectively) revealed that the H atom linked to the phenoxy group and the ortho-C of BPS were the most likely sites to react. The present work reveals the overall transformation behavior of BPS in a radical-triggered PS system by combining experimental and theoretical study.

Iron(iii)-catalyzed synthesis of indole–xanthydrol hybrid through oxidative cycloisomerization/hydroxylation reaction.

The photocatalytic degradation of tetracycline in aqueous solution is a typical heterogeneous reaction, and thus the design of efficient photocatalysts for tetracycline degradation should revolve the process features of heterogeneous reaction closely. In the present work, TiO2-P/g-C3N4 composites with abundant surface hydroxyls were prepared by coupled g-C3N4 nanosheets with plasma treated TiO2 (TiO2-P) nanoparticles. The resultant TiO2-P/g-C3N4 as photocatalysts showed higher activity for the degradation of tetracycline in aqueous solution than g-C3N4, TiO2, TiO2-P and TiO2/g-C3N4 under visible light irradiation. The better activity of TiO2-P/g-C3N4 photocatalysts for tetracycline degradation could be ascribed to the good synergy between TiO2-P and g-C3N4. Specifically, due to the presence of surface hydroxyls on TiO2-P, the tetracycline adsorption activity, electrons-holes separation property as well as H2O2 activating activity of TiO2-P/g-C3N4 during tetracycline degradation were improved. By integrating the property of g-C3N4 photocatalyst in H2O2 production, as well as the property of TiO2-P in activating H2O2 into •OH and •O2-, efficient photo-Fenton degradation of tetracycline was achieved in the TiO2-P/g-C3N4 photocatalytic system. Our study on TiO2/g-C3N4 composite photocatalyst provides helpful inspiration to design photocatalysts with high-activity for the photo-Fenton degradation of organic pollutants.

In this paper, we studied the transformation of two 3β-hydroxy-5-ene-steroids-pregnenolone and dehydroepiandrosterone (DHEA) by Backusella lamprospora VKM F- 944. The soil-dwelling zygomycete wild-type strain has been earlier selected during the screening and previously unexplored for this purpose. The fungus fully converted pregnenolone to form a mixture of axial 7α-hydroxy-pregnenolone and 7α,11α-dihydroxy-pregnenolone, while no metabolites with β-orientation of the hydroxyl group were detected. The pathway to 7α,11α-diOH-pregnenolone seems to include 7α-hydroxylation of 11α-hydroxylated derivative. The only product from DHEA was identified as 7α-hydroxy-DHEA. The structures of steroid metabolites were confirmed by HPLC, mass-spectrometry (MS), and

Herein, we describe a concise total synthesis of dalesconol A through a "polycyclization/oxidation" approach. In the polycyclization stage, a Pd(0)/NBE-catalyzed 3-fold domino reaction and a subsequent intramolecular Michael addition have been utilized for the one-step assembly of the heptacyclic molecular skeleton. In the late stage of oxidation state adjustments, a stepwise sequence including site-selective benzylic oxidation, Pd(II)-catalyzed oxime ether directed trihydroxylation, and desaturation has been adopted to introduce the oxygen functionalities and furnish the synthesis of dalesconol A. With the advantage of the late-stage amidation of three C-H bonds in a single step, the amino analogue of dalesconol A has also been obtained with high efficiency.

Diosgenin is an important compound in the pharmaceutical industry and it is biosynthesized in several eudicot and monocot species, herein represented by fenugreek (a eudicot), and Dioscorea zingiberensis (a monocot). Formation of diosgenin can be achieved by the early C22,16-oxidations of cholesterol followed by a late C26-oxidation. This study reveals that, in both fenugreek and D. zingiberensis, the early C22,16-oxygenase(s) shows strict 22R-stereospecificity for hydroxylation of the substrates. Evidence against the recently proposed intermediacy of 16S,22S-dihydroxycholesterol in diosgenin biosynthesis was also found. Moreover, in contrast to the eudicot fenugreek, which utilizes a single multifunctional cytochrome P450 (TfCYP90B50) to perform the early C22,16-oxidations, the monocot D. zingiberensis has evolved two separate cytochrome P450 enzymes, with DzCYP90B71 being specific for the 22R-oxidation and DzCYP90G6 for the C16-oxidation. We suggest that the DzCYP90B71/DzCYP90G6 pair represent more broadly conserved catalysts for diosgenin biosynthesis in monocots.

Cephalosporins play an indispensable role against bacterial infections. Deacetyloxycephalosporin C synthase (DAOCS), also called expandase, is a key enzyme in cephalosporin biosynthesis that epoxides penicillin to form the hexavalent thiazide ring of cephalosporin. DAOCS in fungus Acremonium chrysogenum was identified as a bifunctional enzyme with both ring expansion and hydroxylation, whereas two separate enzymes in bacteria catalyze these two reactions. In this review, we briefly summarize its source and function, improvement of the conversion rate of penicillin to deacetyloxycephalosporin C through enzyme modification, crystallography features, the prediction of the active site, and application perspective.

Objectives The present study aimed to evaluate the effects of CYP3A4 genetic variation on the kinetics of mechanism-based inhibition (MBI) of both inhibitors using midazolam as a substrate for comparison with our previous study, as midazolam and testosterone have different binding sites. Background The genetic variation of cytochrome P450 (CYP) 3A4 affects MBI, expressed as the maximum inactivation rate constant (kinact,max) and the inhibitor concentration required to achieve half-maximal inactivation (KI). We previously showed, using testosterone as a substrate, that the MBI kinetics of erythromycin and clarithromycin differ among CYP3A4 variants. Materials and methods Midazolam 1'-hydroxylation inactivation profiles of erythromycin and clarithromycin were assessed using recombinant CYP3A4.1, .2, .7, .16, and .18 expressed in Escherichia coli. MBI parameters were calculated from changes in the inactivation rate constant (Δkobs) by the inhibitors. Results Both inhibitors increased Δkobs value in a concentration- and preincubation time-dependent manner, and MBI kinetics differed among variants. Trends of differences in MBI parameters among variants were similar to those assessed using testosterone as a substrate; KI decreased for CYP3A4.7, and kinact,max decreased for CYP3A4.2, .7, and .16. Conclusion The genetic variation of recombinant CYP3A4 affects the MBI profile of CYP3A4 by erythromycin and clarithromycin, while the influence of genetic variation was similarly observed regardless of substrates. Our findings are of clinical relevance because the residual enzyme activity of CYP3A4 in the presence of inhibitor was estimated to vary among genetic variants.

Cyclohexanecarboxylate (CHCA) is formed by oxidative microbial degradation of n-alkylcycloparaffins and anaerobic degradation of benzoate, and also known to be a synthetic intermediate or the starter unit of biosynthesis of cellular constituents and secondary metabolites. Although two degradation pathways have been proposed, genetic information has been limited to the β-oxidation-like pathway. In this study, we identified a gene cluster, designated chcC1XTC2B1B2RAaAbAc, that is responsible for the CHCA aromatization pathway in Sinomonas (formerly Corynebacterium) cyclohexanicum strain ATCC 51369. Reverse transcription-PCR analysis indicated that the chc gene cluster is inducible by CHCA and that it consists of two transcriptional units, chcC1XTC2B1B2R and chcAaAbAc. Overexpression of the various genes in Escherichia coli, and purification of the recombinant proteins led to the functional characterization of ChcAaAbAc as subunits of a cytochrome P450 system responsible for CHCA hydroxylation; ChcB1 and ChcB2 as trans-4-hydroxyCHCA and cis-4-hydroxyCHCA dehydrogenases, respectively; ChcC1 was identified as a 4-oxoCHCA desaturase containing a covalently bound FAD; and ChcC2 was identified as a 4-oxocyclohexenecarboxylate desaturase. The binding constant of ChcAa for CHCA was found to be 0.37 mM. Kinetic parameters established for ChcB1 indicated that it has a high catalytic efficiency towards 4-oxoCHCA compared to trans- or cis-4-hydroxyCHCA. The Km and Kcat values of ChcC1 for 4-oxoCHCA were 0.39 mM and 44 s−1, respectively. Taken together with previous work on the identification of a pobA gene encoding a 4-hydroxybenzoate hydroxylase, we have now localized the remaining set of genes for the final degradation of protocatechuate before entry into the tricarboxylic acid cycle.

Chiral polychlorinated biphenyls (PCB) are environmentally relevant developmental neurotoxicants. Because their hydroxylated metabolites (OH-PCBs) are also neurotoxic, it is necessary to determine how PCB metabolism affects the developing brain, for example, in mouse models. Because the cytochrome P450 isoforms involved in the metabolism of chiral PCBs remain unexplored, we investigated the metabolism of PCB 91 (2,2',3,4',6-pentachlorobiphenyl), PCB 95 (2,2',3,5',6-pentachlorobiphenyl), PCB 132 (2,2',3,3',4,6'-hexachlorobiphenyl), and PCB 136 (2,2',3,3',6,6'-hexachlorobiphenyl) using liver microsomes from male and female

Ternatin-family cyclic peptides inhibit protein synthesis by targeting the eukaryotic elongation factor-1α (eEF1A). A potentially related cytotoxic natural product (“A3”) was isolated from Aspergillus, but only 4 of its 11 stereocenters could be assigned. Here, we synthesized SR-A3 and SS-A3 – two out of 128 possible A3 epimers – and discovered that synthetic SR-A3 is indistinguishable from naturally derived A3. Relative to SS-A3, SR-A3 exhibits enhanced residence time and rebinding kinetics, as revealed by single-molecule fluorescence imaging of elongation reactions catalyzed by eEF1A in vitro. Increased residence time – stereospecifically conferred by the unique β-hydroxyl in SR-A3 – was also observed in cells. Consistent with its prolonged duration of action, thrice-weekly dosing with SR-A3 led to dramatically increased survival in an aggressive Myc-driven mouse lymphoma model. Our results demonstrate the potential of SR-A3 as a cancer therapeutic and exemplify an evolutionary mechanism for enhancing cyclic peptide binding kinetics via stereospecific side-chain hydroxylation.

MINA53 is a JmjC domain 2-oxoglutarate-dependent oxygenase that catalyzes ribosomal hydroxylation and is a target of the oncogenic transcription factor c-MYC. Despite its anticancer target potential, no small-molecule MINA53 inhibitors are reported. Using ribosomal substrate fragments, we developed mass spectrometry assays for MINA53 and the related oxygenase NO66. These assays enabled the identification of 2-(aryl)alkylthio-3,4-dihydro-4-oxoypyrimidine-5-carboxylic acids as potent MINA53 inhibitors, with selectivity over NO66 and other JmjC oxygenases. Crystallographic studies with the JmjC demethylase KDM5B revealed active site binding but without direct metal chelation; however, molecular modeling investigations indicated that the inhibitors bind to MINA53 by directly interacting with the iron cofactor. The MINA53 inhibitors manifest evidence for target engagement and selectivity for MINA53 over KDM4-6. The MINA53 inhibitors show antiproliferative activity with solid cancer lines and sensitize cancer cells to conventional chemotherapy, suggesting that further work investigating their potential in combination therapies is warranted.