Degradation Of Ring Research Articles

Fenpropathrin Biodegradation Pathway in Bacillus sp. DG-02 and Its Potential for Bioremediation of Pyrethroid-Contaminated Soils

The widely used insecticide fenpropathrin in agriculture has become a public concern because of its heavy environmental contamination and toxic effects on mammals, yet little is known about the kinetic and metabolic behaviors of this pesticide. This study reports the degradation kinetics and metabolic pathway of fenpropathrin in Bacillus sp. DG-02, previously isolated from the pyrethroid-manufacturing wastewater treatment system. Up to 93.3% of 50 mg L(-1) fenpropathrin was degraded by Bacillus sp. DG-02 within 72 h, and the degradation rate parameters qmax, Ks, and Ki were determined to be 0.05 h(-1), 9.0 mg L(-1), and 694.8 mg L(-1), respectively. Analysis of the degradation products by gas chromatography-mass spectrometry led to identification of seven metabolites of fenpropathrin, which suggest that fenpropathrin could be degraded first by cleavage of its carboxylester linkage and diaryl bond, followed by degradation of the aromatic ring and subsequent metabolism. In addition to degradation of fenpropathrin, this strain was also found to be capable of degrading a wide range of synthetic pyrethroids including deltamethrin, λ-cyhalothrin, β-cypermethrin, β-cyfluthrin, bifenthrin, and permethrin, which are also widely used insecticides with environmental contamination problems with the degradation process following the first-order kinetic model. Bioaugmentation of fenpropathrin-contaminated soils with strain DG-02 significantly enhanced the disappearance rate of fenpropathrin, and its half-life was sharply reduced in the soils. Taken together, these results depict the biodegradation mechanisms of fenpropathrin and also highlight the promising potentials of Bacillus sp. DG-02 in bioremediation of pyrethroid-contaminated soils.

Elastin degradation and ensuing inflammation as emerging keys to atherosclerosis

This editorial refers to ‘Elastin-derived peptides potentiate atherosclerosis through the immune Neu1–PI3Kγ pathway’ by S. Gayral et al. , pp. 118–127, this issue. In atherosclerosis, remodelling of extracellular matrix (ECM) has long been considered a critical step in disease development/progression, but the multitude of cell types and molecular mechanisms involved is only now starting to emerge. In arteriosclerotic vascular disease, infiltrating leucocytes are known to release proteases, degrade the ECM, and lead to environmental changes allowing smooth muscle growth and plaque evolution. Among the enzymes secreted by leucocytes, a major role is played by elastases, which promote degradation of the elastin ring of arterial walls. This process triggers a tissue rearrangement that is more extensive than simple ECM destruction, because it triggers the production of elastin-derived peptides (EPs) that are not only degradation products, but also bioactive moieties evoking reactions in the surrounding tissues.1 EPs, also known as elastokines, are a family of matrix fragments that possess cytokine-like functions and primarily signal via binding to a unusual cell surface receptor, the elastin receptor …

Combined Application of Biological-Photocatalytic Process in Degradation of Reactive Black Dye: An Excellent Outcome

In the present study, the decolorization and degradation of Reactive Black 5 azo dye was investigated by biological, photocatalytic (UV/TiO2) and combined processes. An application of <i>Pseudomonas aeruginosa</i> ETL-2211 in treatment of the synthetic medium containing RB5 indicated complete decolorization of the dye with 200 mg/L in less than 24 h. Degradation of the aromatic rings, resulting from the destruction of the dye, did not occur during the biological treatment. Mineralization of 50 mg/L RB5 solution was obtained after 80 min by photocatalytic process (in presence of 0.2 g/L TiO2). COD (chemical oxygen demand) was not detectable after complete decolorization of 50 mg/L RB5 solution. However, photocatalytic process was not effective in the removal of the dye at high concentrations (≥200 mg/L). With 200 mg/L concentration, 74.9% of decolorization was achieved after 4 h illumination under photocatalytic process and the absorbance peak in UV region (attributed to aromatic rings) was not completely removed. A two-step treatment process, namely, biological treatment by bacteria followed by photocatalytic degradation, was also assessed. In the combined process (with 200 mg/L RB5), absorbance peak in UV region significantly disappeared after 2 h illumination and about 60% COD removal was achieved in the biological step. It is suggested that the combined process is more effective than the biological and photocatalytic treatments in the remediation of aromatic rings.

Re-optimized technology of protective ileostomy with no need of reversal

To explore the clinical application of aoptimizedtechniquebased onpreviouslyreported protecting stoma with no need forreversal. Thetechniquealso used "the assembly of drainage device" to performprotecting ileostomy. The original method includes enterotomy at the terminal ileum to placedrainage device, which was optimized as follows: two intestinal pursestring with 0.5 cm distance were placed 5 cm away from the ileocecal valve. Transverse enterotomy was performed in the anti-mesenteric side. The assembly was placed at the root of the appendix between two pursestring, and then the intestine purse suture was tighten. Ligation of the small intestine anastomosis between the anastomosis ring at both ends was carried out, and theanastomosis ring was deployed. From the root of the appendix in the cecum wall, the assembly was embedded about 2 cm and pulled out of abdominal cavitythough the Trocar hole. Seventeen cases of ultra-low rectal cancer completed protecting stoma, including 11 cases through ileocecal protective stoma. All the anastomosis healed well. Defecation drainage tube was removed 3-5 weeks after anastomosis ring degradation. Drainage nozzle healed after 3 to 5 days, and no complications occurred. The optimized ileocecal protective ileostomy has the following advantages: (1)wound healing time is significantly shorter. (2)secondary intestinal fistula can be prevented. (3)no need to fix ileum and less chance of subsequent volvulus, intestinal obstruction.

ChemInform Abstract: Design and Synthesis of New 4‐Alkylthio Monocyclic β‐Lactams.

AbstractThe designed products (VI and XIV) contain penicillin‐like structures.

In silico and in vitro metabolism studies support identification of designer drugs in human urine by liquid chromatography/quadrupole-time-of-flight mass spectrometry

Human phase I metabolism of four designer drugs, 2-desoxypipradrol (2-DPMP), 3,4-dimethylmethcathinone (3,4-DMMC), α-pyrrolidinovalerophenone (α-PVP), and methiopropamine (MPA), was studied using in silico and in vitro metabolite prediction. The metabolites were identified in drug abusers’ urine samples using liquid chromatography/quadrupole-time-of-flight mass spectrometry (LC/Q-TOF/MS). The aim of the study was to evaluate the ability of the in silico and in vitro methods to generate the main urinary metabolites found in vivo. Meteor 14.0.0 software (Lhasa Limited) was used for in silico metabolite prediction, and in vitro metabolites were produced in human liver microsomes (HLMs). 2-DPMP was metabolized by hydroxylation, dehydrogenation, and oxidation, resulting in six phase I metabolites. Six metabolites were identified for 3,4-DMMC formed via N-demethylation, reduction, hydroxylation, and oxidation reactions. α-PVP was found to undergo reduction, hydroxylation, dehydrogenation, and oxidation reactions, as well as degradation of the pyrrolidine ring, and seven phase I metabolites were identified. For MPA, the nor-MPA metabolite was detected. Meteor software predicted the main human urinary phase I metabolites of 3,4-DMMC, α-PVP, and MPA and two of the four main metabolites of 2-DPMP. It assisted in the identification of the previously unreported metabolic reactions for α-PVP. Eight of the 12 most abundant in vivo phase I metabolites were detected in the in vitro HLM experiments. In vitro tests serve as material for exploitation of in silico data when an authentic urine sample is not available. In silico and in vitro designer drug metabolism studies with LC/Q-TOF/MS produced sufficient metabolic information to support identification of the parent compound in vivo.

Maleimides in recent sediments – Using chlorophyll degradation products for palaeoenvironmental reconstructions

Maleimides (transformation products of chlorophylls and bacteriochlorophylls) were studied in recent sediments from the Swiss lake Rotsee and the Romanian Black Sea Shelf to investigate chlorophyll degradation, the role of oxygen in maleimide formation, and to identify their sources. Naturally occurring maleimides (i.e. “free” maleimides) and maleimides obtained after chromic acid oxidation of sediment extracts (i.e. “bound” maleimides) were analysed. 2-Methyl-maleimide (Me,H maleimide), 2,3-dimethyl-maleimide (Me,Me maleimide), 2-methyl-3-vinyl-maleimide (Me,vinyl maleimide), 2-methyl-3-ethyl-maleimide (Me,Et maleimide) and traces of 2-methyl-3-iso-butyl-maleimide (Me,i-Bu maleimide) occurred naturally in the sediment with a large predominance of the Me,Et homologue. Tetrapyrrolic pigments related to chlorophylls were the main source of maleimides, although variable contributions of other sources such as cytochromes and/or phycobilins cannot be completely ruled out. The predominant Me,Et maleimide and Me,vinyl maleimide most likely originate mainly from chlorophyll a related pigments. The same holds for Me,H maleimide, which might be formed following degradation of ring E from the tetrapyrrolic nucleus. Alternatively, Me,H maleimide and Me,Me maleimides might be formed by a recently discovered transformation pathway involving the oxidation of vinylic chlorophyll substituents and the formation of an aldehyde intermediate. 2-Methyl-3-n-propyl-maleimide (Me,n-Pr maleimide) and Me,i-Bu maleimide arising from bacteriochlorophyll related pigments traced the presence of phototrophic sulfur bacteria (Chlorobi), indicating photic zone euxinic and anoxic conditions in Rotsee during the last 150years and throughout the Black Sea history, including the limnic phase of the Black Sea (Unit 3). Some other minor maleimides with specific alkylation pattern also originate from bacteriochlorophylls, while the source of others could not be identified. Free maleimides were mainly formed in the sediment in the absence of oxygen. Novel maleimide degradation indices are proposed to estimate the degree of OM degradation (OM freshness/degradability). These proxies are applicable on longer timescales than e.g. the chlorin index.

Design and Synthesis of New 4-Alkylthio Monocyclic β-Lactams

Sang Hyup LeeCollege of Pharmacy, Duksung Women’s University, Seoul 132-714, Korea. E-mail: sanghyup@duksung.ac.krReceived August 1, 2012, Accepted October 16, 2012New types of monocyclic β-lactams constitute an important class of compounds due to their unique structuresand natures. Here, the design and synthesis of new 4-alkylthio monocyclic β-lactams 2a and 3a are reported.Significantly, compounds 2a and 3a, while keeping a monocyclic system, were designed to contain all of thesubstructures provided by the cleavage of C(2)-C(3) bond in penicillins. Efficient synthetic pathways forcompounds 2a and 3a were established based on two different strategies. Compound 2a was synthesized fromraw materials, using 4-acetoxyazetidin-2-one as a key intermediate, through a ten-step synthetic sequence in3% overall yield. Compound 3a was synthesized from potassium salt of penicillin G (17), using the degradedproduct 20 as a key intermediate, through a six-step synthetic sequence in 11% overall yield. 4-Alkylthio-azetidin-2-one derivatives, introduced in this study, could serve as valuable intermediates for the developmentof new monocyclic β-lactams. Key Words : Monocyclic β-lactams, Penicillin, Isopropylthioazetidinone, t-Butylthioazetidinone, Degrada-tion of penicillin IntroductionThe four-membered ring appears to be the smallest cyclicsystem that accommodates the amide function as a con-stituent. Such four-membered cyclic amides, commonly re-ferred to β-lactams, possess physical and chemical pro-perties that diverge sharply from those of acyclic amides,partially due to ring strain. After numerous penicillins andcephalosporins, new types of nonclassical β-lactams haveappeared. Monocyclic β-lactam compounds

A hybrid photocatalysis–ultrafiltration continuous process for humic acids degradation

The successful operation of a hybrid photocatalysis–membrane separation process (in a laboratory-scale pilot system) is demonstrated for degradation of Humic Acids (HAs), which are typical refractory components of Natural Organic Matter (NOM). The Photocatalytic Membrane Reactor (PMR) employing an Ultrafiltration (UF) submerged module was operated in continuous mode with TiO2 catalyst concentration 0.75g/L and UV-A radiant flux 15.1J/s, treating feed water with HA concentrations 5.0 and 10.0mg/L. Experiments carried out within a sufficiently broad pH range (approx. 3.5–7.0) exhibited satisfactory HA mineralization rates and rather high HA mineralization efficiencies; a near optimum pH at approx. 5.5 was identified. The overall process removal efficiency (comprising both HA oxidation and UF membrane rejection) was even higher, as a result of the synergistic effects of photocatalytic oxidation and membrane filtration. The degradation of HA aromatic rings, that diminishes the Disinfection By-Products (DBPs) formation potential, was also very high; the specific UV-A254 removal efficiency was greater than 95% in almost all cases studied. Concerning membrane filtration performance, the periodic backwashing employed, combined with the moderate membrane flux, effectively controlled membrane fouling thus permitting stable continuous operation with no wastewater stream.

Degradation of Reactive Black 5 in Aqueous Solution by Double-Dielectric Barrier Discharge

Degradation of Reactive Black 5 in aqueous solution was studied by double-dielectric barrier discharge, degradation efficiency and degradation mechanism has been investigated. Results shows that during in ten minutes degradation, decolorization efficiency can reach 98.76%,COD and TOC could not be reduce observably, while the biodegradability has been greatly improved, the BOD5/COD ratio increase from 0.079 to 0.495.Decolorization efficiency is higher than that of mineralization, decolorization follows the first order kinetics with a constant rate of 0.4008 min-1. pH of the solution decrease gradually, but the conductivity increase during the degradation process. The ions of sulfate, nitrate, acetic acid, and oxalic acid have been found in the final treated sample and their concentrations increase with the reaction time. Chromophore group is damaged firstly and the solution has been decolorized efficiently, the degradation of benzene ring and naphthalene ring is more difficult than that of the azo bond, and the reduction or disappearance of absorption peaks indicates that the aromatic ring of KN-B was degraded partly.

Degradation of a textile reactive azo dye by a combined biological-photocatalytic process: Candida tropicalis Jks2 -Tio2/Uv

In the present study, the decolorization and degradation of Reactive Black 5 (RB5) azo dye was investigated by biological, photocatalytic (UV/TiO2) and combined processes. Application of Candida tropicalis JKS2 in treatment of the synthetic medium containing RB5 indicated complete decolorization of the dye with 200 mg/L in less than 24 h. Degradation of the aromatic rings, resulting from the destruction of the dye, did not occur during the biological treatment. Mineralization of 50 mg/L RB5 solution was obtained after 80 min by photocatalytic process (in presence of 0.2 g/L TiO2). COD (chemical oxygen demand) was not detectable after complete decolorization of 50 mg/L RB5 solution. However, photocatalytic process was not effective in the removal of the dye at high concentrations (≥200 mg/L). With 200 mg/L concentration, 74.9% of decolorization was achieved after 4 h illumination under photocatalytic process and the absorbance peak in UV region (attributed to aromatic rings) was not completely removed. A two-step treatment process, namely, biological treatment by yeast followed by photocatalytic degradation, was also assessed. In the combined process (with 200 mg/L RB5), absorbance peak in UV region significantly disappeared after 2 h illumination and about 60% COD removal was achieved in the biological step. It is suggested that the combined process is more effective than the biological and photocatalytic treatments in the remediation of aromatic rings.

WYE‐120318, a ring contraction product of methylnaltrexone, and structure revision of coniothyrione

A contracted ring degradation product, WYE-120318 (compound 2), was discovered during the development phase for methylnaltrexone bromide (compound 1) drug substance. The compound was isolated by high-performance liquid chromatography fractionation, and its structure was determined by spectroscopic data analyses. WYE-120318 is formed from methylnaltrexone through a benzyl-benzilic acid type rearrangement reaction to yield an α-hydroxy-cyclopentanecarboxylic acid substructure. The proposed structure and the formation mechanism are confirmed by the synthesis of WYE-120318 from methylnaltrexone (compound 1). A similar benzyl-benzilic acid type rearrangement reaction can be envisioned as the biological origin of remisporine A (compound 3), a naturally occurring cyclopentadienyl compound that autocatalytically dimerizes to remisporine B (compound 4). The structure of remisporine A was deduced from its dimer 4. Coniothyione (compound 5) can be considered as the first example of a stable natural product bearing the remisporine A skeleton. However, the regiochemistry of the chlorosubstitution in the coniothyrione structure needs to be revised to compound 6 on the basis of the nuclear magnetic resonance data and biogenesis analysis.

Ozonation of metoprolol in aqueous solution: ozonation by-products and mechanisms of degradation

This study investigated the degradation pathway of metoprolol, a widely used β-blocker, in the ozonation via the identification of generated ozonation by-products (OPs). Structure elucidation of OPs was performed using HPLC coupled with quadrupole time-of-flight high-resolution mass spectrometry. Seven OPs were identified, and four of these have not been reported elsewhere. Identified OPs of metoprolol included aromatic ring breakdown by-products; aliphatic chain degraded by-products and aromatic ring mono-, di-, and tetrahydroxylated derivatives. Based on the detected OPs, metoprolol could be degraded through aromatic ring opening reaction via reaction with ozone (O3) and degradation of aliphatic chain and aromatic ring via reaction with hydroxyl radical (•OH).

Investigation of the inner structure of La Crosa de Sant Dalmai maar (Catalan Volcanic Zone, Spain)

La Crosa de Sant Dalmai volcano is the largest volcanic edifice of the Catalan Volcanic Zone (NE Spain). It is a very well preserved maar-type structure, 1.5km in diameter, excavated at the contact between a hard substrate and a soft substrate formed by Palaeozoic granites and Pliocene and Quaternary gravels, respectively. In order to infer the uppermost inner structure of La Crosa de Sant Dalmai maar and to characterise its main geological and tectonic constraints, we have performed a multiparametric geophysical study including gravimetry, magnetometry, self-potential, and electrical resistivity tomography. The results obtained together with a field geology revision and additional geological data from two drill cores, provide a detailed picture of the post-eruptive maar infill sequence as well as of the uppermost part of the maar-diatreme structure. This information helps in understanding the origin and subsequent evolution of the volcano, which included an alternation of phreatomagmatic and Strombolian phases. Geophysical data show that the last Strombolian phase, which culminated with the formation of a scoria cone inside the maar, was associated with a NW–SE trending regional fault. The little erosion and degradation of the original tephra ring suggest a much younger age of La Crosa de Sant Dalmai maar than was previously stated.

Anaerobic p -Coumarate Degradation by Rhodopseudomonas palustris and Identification of CouR, a MarR Repressor Protein That Binds p -Coumaroyl Coenzyme A

The phenylpropanoid p-coumarate and structurally related aromatic compounds are produced in large amounts by green plants and are excellent carbon sources for many soil bacteria. Aerobic bacteria remove the acyl side chain from phenylpropanoids to leave an aromatic aldehyde, which then enters one of several possible central pathways of benzene ring degradation. We investigated the pathway for the anaerobic degradation of p-coumarate by the phototrophic bacterium Rhodopseudomonas palustris and found that it also follows this metabolic logic. We characterized enzymes for the conversion of p-coumarate to p-hydroxybenzaldehyde and acetyl coenzyme A (acetyl-CoA) encoded by the couAB operon. We also identified a MarR family transcriptional regulator that we named CouR. A couR mutant had elevated couAB expression. In addition, His-tagged CouR bound with high affinity to a DNA fragment encompassing the couAB promoter region, and binding was abrogated by the addition of nanomolar quantities of p-coumaroyl-CoA but not by p-coumarate. Footprinting demonstrated binding of CouR to an inverted repeat sequence that overlaps the -10 region of the couAB promoter. Our results provide evidence for binding of a CoA-modified aromatic compound by a MarR family member. Although the MarR family is widely distributed in bacteria and archaea and includes over 12,000 members, ligands have been identified for relatively few family members. Here we provide biochemical evidence for a new category of MarR ligand.

Formation of nanocrystalline h-AlN during mechanochemical decomposition of melamine in the presence of metallic aluminum

Decomposition of melamine was studied by solid state reaction of melamine and aluminum powders during high energy ball-milling. The milling procedure performed for both pure melamine and melamine/Al mixed powders as the starting materials for various times up to 48h under ambient atmosphere. The products were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results revealed that Al causes melamine deammoniation at the first stages of milling and further milling process leads to the s-triazine ring degradation while nano-crystallite hexagonal aluminum nitride (h-AlN) was the main solid product. Comparison to milling process, the possibility of the reaction of melamine with Al was also investigated by thermal treatment method using differential scanning calorimeter (DSC) and thermo gravimetric analyzer (TGA). Melamine decomposition occurred by thermal treatment in the range of 270–370°C, but no reaction between melamine and aluminum was observed.

Improvement of RNA-SIP by pyrosequencing to identify putative 4-n-nonylphenol degraders in activated sludge

Nonylphenols (NP) have estrogenic potential because of their phenolic ring, but the organisms involved in the degradation of this alkylated phenol remain unidentified. Using 16S ribosomal RNA (rRNA)-based stable isotope probing (SIP) and a new method based on pyrosequencing, we identified the bacteria involved in the degradation of the aromatic ring of [U-ring- 13C] 4-n-NP in aerobic sludge. The first order degradation rate of 4-n-NP was 5.5 d −1. Single strand conformation polymorphism of density-separated labeled and unlabeled 16S rRNA showed significant differences and enabled selection of four representative fractions for pyrosequencing. Nineteen phylotypes showed a significant enrichment in the heavy fraction in the labeled pulse. The relative abundances of these phylotypes were combined with the RNA concentration of each fraction to yield a simple model of the distribution of each phylotype across the gradient. This model was used to estimate the percentage of labeling for each phylotype. The sequences showing the highest labeling (11%) were closely related to Afipia sp. but represented only 2 % of the RNA in the heavy fraction of the labeled pulse. The sequences representing the largest proportion of the RNA in the heavy fraction were related to Propionibacterium acnes and Frateuria aurantia, which are known to possess enzymes for phenol degradation. The model shows that despite Afipia having the highest 13C enrichment, other species encoding phenol degradation pathways are responsible for more 13C incorporation. Last, we showed that some species represent 12% of the total RNA but contain only 1% 13C above natural abundance.

Activity of 3-Ketosteroid 9α-Hydroxylase (KshAB) Indicates Cholesterol Side Chain and Ring Degradation Occur Simultaneously in Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb), a significant global pathogen, contains a cholesterol catabolic pathway. Although the precise role of cholesterol catabolism in Mtb remains unclear, the Rieske monooxygenase in this pathway, 3-ketosteroid 9α-hydroxylase (KshAB), has been identified as a virulence factor. To investigate the physiological substrate of KshAB, a rhodococcal acyl-CoA synthetase was used to produce the coenzyme A thioesters of two cholesterol derivatives: 3-oxo-23,24-bisnorchol-4-en-22-oic acid (forming 4-BNC-CoA) and 3-oxo-23,24-bisnorchola-1,4-dien-22-oic acid (forming 1,4-BNC-CoA). The apparent specificity constant (k(cat)/K(m)) of KshAB for the CoA thioester substrates was 20-30 times that for the corresponding 17-keto compounds previously proposed as physiological substrates. The apparent K(m)(O(2)) was 90 ± 10 μM in the presence of 1,4-BNC-CoA, consistent with the value for two other cholesterol catabolic oxygenases. The Δ(1) ketosteroid dehydrogenase KstD acted with KshAB to cleave steroid ring B with a specific activity eight times greater for a CoA thioester than the corresponding ketone. Finally, modeling 1,4-BNC-CoA into the KshA crystal structure suggested that the CoA moiety binds in a pocket at the mouth of the active site channel and could contribute to substrate specificity. These results indicate that the physiological substrates of KshAB are CoA thioester intermediates of cholesterol side chain degradation and that side chain and ring degradation occur concurrently in Mtb. This finding has implications for steroid metabolites potentially released by the pathogen during infection and for the design of inhibitors for cholesterol-degrading enzymes. The methodologies and rhodococcal enzymes used to generate thioesters will facilitate the further study of cholesterol catabolism.

Effect of inorganic anions on the photocatalytic decolorisation of an azo dye in the aqueous phase by cadmium sulphide/polymer nanocomposite films under visible light irradiation

Batch experiments were carried out to study the effects of various inorganic anions on the photocatalytic decolorisation of an azo dye (CI Methyl Orange 13025) in the aqueous phase in the presence of cadmium sulphide/polymer nanocomposite films under visible light irradiation. When anion concentrations were low (0.001 m), the inhibition effect on the photocatalytic decolorisation of CI Methyl Orange 13025 caused by these anions was ranked as . The presence of both and baffled the breakage of the benzene ring in the chemical structure of CI Methyl Orange 13025, while the presence of was of benefit to the degradation of the benzene ring. Adsorption experiments indicated that inorganic anions affected the decolorisation of CI Methyl Orange 13025 by competitive adsorption onto the surface of the photocatalyst. The photocatalytic decolorisation of CI Methyl Orange 13025 followed the pseudo‐first‐order kinetic reaction model well in all experimental cases.

Cloning, overexpression, purification, crystallization and preliminary X-ray analysis of 3-ketosteroid Δ(4)-(5α)-dehydrogenase from Rhodococcus jostii RHA1.

3-Ketosteroid dehydrogenases are flavoproteins which play key roles in steroid ring degradation. The enzymes are abundantly present in actinobacteria, including the catabolic powerhouse Rhodococcus jostii and the pathogenic species R. equi and Mycobacterium tuberculosis. The gene for 3-ketosteroid Δ(4)-(5α)-dehydrogenase [Δ(4)-(5α)-KSTD] from R. jostii RHA1 was cloned and overexpressed in Escherichia coli. His-tagged Δ(4)-(5α)-KSTD enzyme was purified by Ni(2+)-NTA affinity chromatography, anion-exchange chromatography and size-exclusion chromatography and was crystallized using the hanging-drop vapour-diffusion method. Seeding greatly improved the number of crystals obtained. The crystals belonged to space group C222(1), with unit-cell parameters a = 99.2, b = 114.3, c = 110.2 Å. Data were collected to a resolution of 1.6 Å.