P-nitrobenzyl Alcohol Research Articles

Biological reduction and hydrodechlorination of chlorinated nitroaromatic antibiotic chloramphenicol under H2-transfer membrane biofilm reactor

Chlorinated nitroaromatic antibiotic chloramphenicol (CAP) is a persistent pollutant that is widely present in environments. A H2 transfer membrane biofilm reactor (H2-MBfR) and short-term batch tests were setup to investigate the co-removal of CAP and NO3-. Results showed that the presence of CAP (<10 mg L-1) has no effect on the denitrification process while 100% removal efficiency of CAP can be obtained when nitrate was absent. Nitroaromatic reduction and completely dechlorination were successfully realized when CAP was removed. The CAP transformation product p-aminobenzoic acid (PABA) was detected and batch tests revealed that the hydroxy carboxylation was far faster than nitroaromatic reduction when p-nitrobenzyl alcohol (PNBOH) was conversed to p-aminobenzoic acid (PABA). The path way of CAP degradation was proposed based on the intermediate’s analysis. Microbial community analysis indicated that Pleomorphomonadaceae accounts for the dechlorination of CAP.

Bioactivity Screening of Endophytic Fungus Eutypa linearis isolated from Coleus amboinicus (Lour.)

Coleus amboinicus (Lour.) is a medicinal plant containing various bioactive compounds. Endophytes are microorganisms living inside intracellular tissue of plants and known as the source of bioactive compounds. In order to explore the potential of endophyte in producing novel bioactive compounds, this study focused on isolating endophytic fungi from the leaves of C.amboinicus, characterisation and screening their metabolite bioactivity during submerged culture fermentation. Isolation of endophytic fungi from the leaves segment of C.amboinicus was conducted on PDA media and fungus identification was carried out by analyzing its morphology and molecular examination. The production of metabolites was examined using thin layer chromatography and gas chromatography. Identification of the endophytic fungus showed 98.84% similarity with Eutypa linearis. This species was fermented submergedly in PDB medium for 14 days under dark and exposed to light and the fermentation broth was extracted using ethyl acetate. The results showed that exposure to the light did not significantly influence metabolite production. The ethyl acetate extract exhibited antioxidant and cytotoxic activities. Antioxidant activity of this extract as examined by DPPH assay showed IC50 of 105.31 ± 2.11 µg/mL. Cytotoxic activity against Hela cell line was known to be the best among other cell lines (IC50 301.53 ± 11.34 µg/mL) although it was found to be non selective (SI&lt;1). The extract contained five major compounds namely Benzenemethanol, 4-nitro-(CAS) p-Nitrobenzyl alcohol; 2-Pentadecanone (CAS) Pentadecan-2-one; (1R*,6S*,10R*)-5,5-Dimethyl-11,12-dioxatricyclo[8.2.1.0(1,6)] tridecan-10-ol; 9,12-Octadecadienoic acid (Z,Z)-, methyl ester (CAS) Methyl linoleate; and 3-Furanacetic acid, 4-hexyl-2,5-dihydro-2,5-dioxo- (CAS) 2-carboxymethyl-3-N-hexyl-maleic anhydride.

A Redox Isomerization Strategy for Accessing Modular Azobenzene Photoswitches with Near Quantitative Bidirectional Photoconversion.

Photoswitches capable of accessing two geometric states are highly desirable, especially if their design is modular and incorporates a pharmacophore tethering site. We describe a redox isomerization strategy for synthesizing p-formylazobenzenes from p-nitrobenzyl alcohol. The resulting azo-aldehydes can be readily converted to photoswitchable compounds with excellent photophysical properties using simple hydrazide click chemistry. As a proof of principle, we synthesized a photoswitchable surfactant enabling the photocontrol of an emulsion with exceptionally high spatiotemporal precision.

Novel Biodegradable Polymer with Redox‐Triggered Backbone Cleavage Through Sequential 1,6‐Elimination and 1,5‐Cyclization Reactions

In the past decade, the self-immolative biodegradable polymer arose as a novel paradigm for its efficient degradation mechanism and vast potential for advanced biomedical applications. This study reports successful synthesis of a novel biodegradable polymer capable of self-immolative backbone cleavage. The monomer is designed by covalent conjugations of both pendant redox-trigger (p-nitrobenzyl alcohol) and self-immolative linker (p-hydroxybenzyl alcohol) to the cyclization spacer (n-2-(hydroxyethyl)ethylene diamine), which serves as the structural backbone. The polymerization of the monomer with hexamethylene diisocyanate yields a linear redox-sensitive polymer that can systemically degrade via sequential 1,6-elimination and 1,5-cyclization reactions within an effective timeframe. Ultimately, the polymer's potential for biomedical application is simulated through in vitro redox-triggered release of paclitaxel from polymeric nanoparticles.

Molecularly imprinted polymer containing Fe(III) catalysts for specific substrate recognition

A series of molecularly imprinted polymers (MIPs) containing equal amounts of iron(III) were prepared by the polymerization of acrylamide and ethylene dimethacrylate in the presence of the template of o-, m-, or p-nitrobenzyl alcohol (NBA) and a FeCl3 complex. The samples were characterized by scanning electron microscopy, N2 adsorption, and Fourier transform infrared spectroscopy. The catalysts exhibited high catalytic activity and unique substrate recognition in the oxidation of benzyl alcohol derivatives in water using 30% H2O2 as the oxidant. The conversion of p-NBA was 80% over the p-Fe(III)-MIP catalyst when the template molecule was p-NBA, which had a good fit with the substrate. However, the conversion of p-NBA was less than 58% over o-Fe(III)-MIP or m-Fe(III)-MIP due to the mismatch of the substrate with the cavities of the Fe(III)-MIP. The results indicated that the Fe(III)-MIP samples contained molecular recognizable shapes and sites in their cavities that match the corresponding substrate. The special recognizing cavities of the Fe(III)-MIP catalyst exhibited unique substrate recognition, and therefore the selectivity for the substrate was improved.

The Meerwein–Ponndorf–Verley type reaction in a mixture of supercritical isopropanol/CO 2 in a continuous flow reactor in the presence of alumina

A system for efficient reduction of aromatic and aliphatic aldehydes to respective alcohols by the Meerwein–Ponndorf–Verley reaction at a contact time of less than 4 min and temperature below 473 K has been developed. The system comprises a continuous flow reactor, mixed supercritical isopropanol/CO 2 solvent and alumina as a catalyst. Reduction of p-nitobenzealdehyde at 425 K yields p-nitrobenzyl alcohol; at 465 K the main reaction product is p-toluidine. α,β-Unsaturated monoterpenic aldehyde myrtenal was reduced into corresponding α,β-unsaturated alcohol myrtenol. At higher temperatures, reduction of myrtenol to saturated alcohol myrtanol becomes possible.

N-(ethoxycarbonyl)ferrocenecarboxamide: Synthesis and use as the pronucleophile in the Mitsunobu reaction

The title compound has been synthesized in the reaction of ferrocene with ethoxycarbonyl isocyanate in methanesulfonic acid. It has been found that it undergoes N-alkylation with benzyl alcohols under classical Mitsunobu conditions (PPh 3/DEAD). However, in the reaction with cholesterol and stigmasterol O-alkylation with inversion of configuration occurred (confirmed by hydrolysis of the product obtained from cholesterol to epicholesterol). The structure of the product obtained from p-nitrobenzyl alcohol was determined by X-ray diffraction.

Amplification of Anti-Diastereoselectivity via Curtin−Hammett Effects in Ruthenium-Catalyzed Hydrohydroxyalkylation of 1,1-Disubstituted Allenes: Diastereoselective Formation of All-Carbon Quaternary Centers

Under the conditions of ruthenium-catalyzed transfer hydrogenation, 1,1-disubstituted allenes 1a-c and alcohols 2a-g engage in redox-triggered generation of allylruthenium-aldehyde pairs to form products of hydrohydroxyalkylation 3a-g, 4a-g, and 5a-g with complete branched regioselectivity. By exploiting Curtin-Hammett effects, good to excellent levels of anti-diastereoselectivity (4:1 to >20:1) are obtained. Thus, all carbon quaternary centers are formed in a diastereoselective fashion upon carbonyl addition from the alcohol oxidation level in the absence of premetalated nucleophiles or stoichiometric byproducts. Exposure of allene 1b to equimolar quantities of alcohol 2a and aldehyde 6b under standard reaction conditions delivers adducts 4a and 4b in a 1:1 ratio. Similarly, exposure of allene 1b to equimolar quantities of aldehyde 6a and alcohol 2b provides adducts 4a and 4b in an identical equimolar ratio. Exposure of allene 1b to d(2)-p-nitrobenzyl alcohol, deuterio-2a, under standard reaction conditions delivers the product of hydrohydroxyalkylation, deuterio-4a, which incorporates deuterium at the carbinol position (>95% (2)H) and the interior vinylic position (34% (2)H). Competition experiments involving exposure of allene 1b to equimolar quantities of benzylic alcohols 2a and deuterio-2a reveal no significant kinetic effect. The collective data corroborate rapid, reversible alcohol dehydrogenation, allene hydrometalation, and (E)-, (Z)-isomerization of the transient allylruthenium in advance of turnover-limiting carbonyl addition. Notably, analogous allene-aldehyde reductive C-C couplings employing 2-propanol as the terminal reductant display poor levels of anti-diastereoselectivity, suggesting that carbonyl addition is not turnover-limiting in reactions conducted from the aldehyde oxidation level.

Selective oxidation of p-nitrobenzyl alcohol to p-nitrobenzaldehyde with 10% Ni silica with 30% H2O2 in acetonitrile solvent

p-Nitrobenzyl alcohol is oxidized to p-nitrobenzaldehyde with good selectivity using 30% H2O2 and 10% Ni/SiO2 as catalyst in acetonitirle, as refluxing solvent. A 95% conversion and single product are achieved. Using the same system, benzhydrol was selectively converted to benzophenone with 100% conversion. Cinnamyl alcohol, menthol and cyclohexanol were also converted to their corresponding aldehydes or ketones, but with less efficiency.

Fluorocarbon Soluble Copper(II) Carboxylate Complexes with Nonfluoroponytailed Nitrogen Ligands as Precatalysts for the Oxidation of Alkenols and Alcohols under Fluorous Biphasic or Thermomorphic Modes: Structural and Mechanistic Aspects

This fluorous biphasic catalysis (FBC) contribution was focused on the synthesis and characterization of new fluorous soluble R(f)-Cu(II) carboxylate complexes containing nonfluoroponytailed ligands and defines their role as precatalysts for the FBC oxidation of alkenols and alcohols in the presence of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO)/O(2). In this FBC approach, we have utilized the phase-switching technique of Vincent et al. (J. Am. Chem. Soc. 2002, 124, 12942) to solubilize the nonfluoroponytailed ligands, N-1,4,7-Me(3)TACN, 2, and N-1,4,7-pentamethyldiethylenetriamine (PMDETA), 3, by reaction with a fluorous solvent-soluble copper (II) dimeric complex, [Cu({C(8)F(17)(CH(2))(2)}(2)CHCO(2))(2)](2), 1. Moreover, the reaction of nonfluoroponytailed ligands 2 and 3 with 1 afforded new perfluoroheptane-soluble Cu(II) complexes, [Cu({C(8)F(17)(CH(2))(2)}(2)CHCO(2))(2)(2)], 4, and [Cu({C(8)F(17)(CH(2))(2)}(2)CHCO(2))(2) (3)], 5, respectively. The known Cu(II) complex, 1, was further characterized by electron paramagnetic resonance (EPR) spectroscopy confirming its dimeric structure, while 4 and 5 were characterized by elemental analysis, IR, diffuse reflectance UV-vis, and EPR spectroscopy. Furthermore, 1, 4, and 5 were evaluated as precatalysts for alkenol and alcohol oxidation. The oxidation reactions of alkenols and alcohols in the presence of TEMPO/O(2) proceeded under FBC conditions for 1, 4, and 5, but 1-octanol was unreactive under single-phase FBC conditions at 90 degrees C with TEMPO/O(2). The thermomorphic property of 5, soluble in chlorobenzene/toluene at 90 degrees C but insoluble at room temperature, was also evaluated in the selective oxidation of p-nitrobenzyl alcohol to p-nitrobenzaldehyde. Plausible mechanisms concerning these FBC/thermomorphic oxidation reactions will be discussed.

Construction and optimization of a monophasic organic–water system for enzymatic synthesis of p-nitrobenzyl β- d-glucopyranosides by reverse hydrolysis

A monophasic organic–water system for efficient enzymatic synthesis of β- d-glucopyranoside by reverse hydrolysis was constructed and optimized. p-Nitrobenzyl alcohol ( pNBA), selected as a model substrate alcohol, was readily glucosylated with d-glucose through reverse hydrolysis using almond β- d-glucosidase in a monophasic aqueous-organic medium, producing a new glucoside, p-nitrobenzyl β- d-glucopyranoside (pNBG). The effects of different buffers, organic solvents and water contents were investigated. Buffer type and pH affected the initial reaction rate but had little effect on the final yields. The ratio of organic solvent to water plays a crucial role in shifting the reaction equilibrium toward synthesis, but a minimum amount of water is necessary to maintain the enzyme activity. Dioxane, which was previously known as an unsuitable solvent for β- d-glucosidase-catalyzed reactions, was found to be the most appropriate solvent for this synthetic procedure. The reaction equilibrium and enzyme stability in the reaction medium were also investigated. Under the optimal reaction conditions, i.e. 90% dioxane (v/v) + 10% buffer (Na 2HPO 4–KH 2PO 4, 70 mM, pH 6.0) with alcohol-to-glucose molar ratio of 9:1, p-nitrobenzyl β- d-glucopyranoside was produced with a maximum yield (13.3%).

Glycosylation of sialyl acetates with a novel catalyst combination: Bismuth triflate and BF 3·OEt 2 system

A combined system of bismuth triflate [Bi(OTf) 3] and boron trifluoride etherate (BF 3·OEt 2) in dichloromethane is an efficient promoter for the glycosylation of N-acetylneuraminic acid derivatives. The co-existence of two acid catalysts such as Bi(OTf) 3–BF 3·OEt 2 or Bi(OTf) 3–PPA is confirmed to be essential for obtaining high yields of glycosylation products with p-nitrobenzyl alcohol, which also turned to be superior to those reported previously.

Micellar electrokinetic chromatography with on-line Fourier transform infrared detection.

Micellar electrokinetic chromatography (MEKC) was successfully coupled to Fourier transform infrared (FTIR) detection, using a micromachined IR-transparent flow cell with an optical path length of 15 micro m for the on-line detection of five neutral analytes. Tight connections between the flow cell and the capillaries were achieved by creating a small O-ring of UV-curing epoxy adhesive on the sharply cut capillary ends. The background electrolyte consisted of 15 mM phosphate buffer at pH 7 and 40 mM sodium dodecyl sulfate (SDS). Five analytes (paracetamol, caffeine, p-nitro benzyl alcohol, m-nitrophenol and p-nitrophenol) were successfully separated, yielding detailed IR stack plots that could be used for quantification and identification. Linear calibration graphs were obtained for each individual analyte present in mixtures at concentrations up to 10 mM. The limit of detection (3 S/N) ranged between 1.1 and 1.5 mM (1.2-1.8 ng). Analytes were identified by comparing spectra obtained during the MEKC separation with those resulting from completely filling the capillary with each individual analyte dissolved in the micelle-containing electrolyte. Information on the specific functional groups of all analytes could be elucidated from the spectra. Since FTIR is a nondestructive detection technique, a conventional on-line UV detector was introduced directly after the developed IR flow cell to test the system's performance and to demonstrate that tandem FTIR and UV detection is feasible.

Synthesis and Characterization of Rhenium(III) and Technetium(III) Organohydrazide Chelate Complexes. Reactions of 2-Hydrazinopyridine with Complexes of Rhenium and Technetium.

The organohydrazide chelate complexes M(III)(NNpy)(PPh(3))(2)Cl(2) (1, 3) (M = Re, Tc) have been synthesized using the organohydrazine 2-hydrazinopyridine. The chelated organohydrazide is a diazenido(1-) ligand that forms a five-membered ring with the metal center. An X-ray structural analysis of 1 indicates that there is a delocalized pi-system formed by the chelate ring. These octahedral, d(4) metal complexes have diamagnetic (1)H NMR spectra. Complex 1, C(41.50)H(34)Cl(2)N(3)O(0.5)P(2)Re, crystallizes in the triclinic space group P&onemacr; with a = 10.5549(7) Å, b = 12.2699(8) Å, c = 16.8206(12) Å, alpha = 105.9050(10) degrees, beta = 95.8930(10) degrees, gamma = 111.0100(10) degrees, V = 1906.1(2) Å(3), Z = 2, and R = 0.0650 based on 5268 unique reflections. The FABMS+ in (p-nitrobenzyl alcohol) of 3 reveals a parent ion peak at m/z 799.2. The complex [Re(HNNpy)(NNpy)(PMe(2)Ph)(2)Cl](+)[Cl](-) (2) contains a chelated, neutral organodiazene ligand and a linear, diazenido(1-) ligand. The X-ray structural analysis of 2, C(26)H(30)Cl(2)N(6)P(2)Re, indicates a delocalized pi-system formed by the chelate ring. The (1)H NMR spectrum of 2 is not paramagnetically shifted. Complex 2 crystallizes in the orthorhombic space group Pna2(1) with a = 17.383(4) Å, b = 13.967(3) Å, c = 12.002(2) Å, V = 2913.9(10) Å(3), Z = 4, and R = 0.0384 based on 3083 unique reflections.

Efficient and selective p-nitrophenyl-ester-hydrolyzing antibodies elicited by a p-nitrobenzyl phosphonate hapten.

A number of monoclonal antibodies elicited against a nitrobenzyl (Nbzl)-phosphonate transition-state analogue (TSA), and which were selected for the hydrolysis of the corresponding Nbzl-ester, were also found to catalyze the hydrolysis of the analogous p-nitrophenyl(Np) ester with notable efficiency and specificity. The activity towards the Np-ester is higher in terms of rates (k(cat); as expected from the higher intrinsic reactivity of Np-esters); however, the rate acceleration (k(cat)/k(uncat)) is close to or lower than that observed with the Nbzl-ester. Unexpectedly, the affinity to the Np-ester substrate (1/K(M)) and therefore k(cat)/K(M) are significantly higher. The best example is antibody D2.4 having a k(cat)/K(M) value of 64 s(-1) x M(-1) with the Nbzl-ester and 9400 s(-1) x M(-1) with the Np-ester. Moreover, due to a lower product inhibition by p-nitrophenol relative to p-nitrobenzyl alcohol, these antibodies exhibit more than 1000 turnovers with the Np-ester. The differential affinity of these antibodies to the Nbzl-phosphonate TSA versus the Nbzl-ester substrate (K(S)/K(TSA) or K(M)/K(i)) correlates well with the observed rate enhancement (k(cat)/k(uncat)). For the Np-ester, however, stabilisation of the transition state (as reflected by K(S)/K(TSA) and by the catalytic proficiencies, k(cat)/K(M)/k(uncat)) does not fully account for the catalytic power (k(cat)/k(uncat)), indicating a more complex catalytic mechanism than simply transition-state stabilization. A comparison of the kinetic parameters of D2.4 with other Np-ester-hydrolyzing antibodies raised against Np-phosphonate haptens emphasizes the marked advantage of this antibody which was elicited against an Nbzl-phosphonate hapten. These results appear to be general: anti-(Nbzl-phosphonate TSA) antibodies obtained from other mouse strains and using different immunization protocols are also efficient Np-esterases. They demonstrate the use of an expanded TSA-hapten, where a spacer (a methylene group) mimics bonds that are partially cleaved in the transition state of the catalyzed reaction.

Photoreactivity of chloramphenicol in vitro and in vivo.

The negative side effects of chloramphenicol (CAP) mostly involve blood dyscrasias (e.g. irreversible non-dose-dependent aplastic anemia), allergic skin reactions and eye damage. To learn the cause of these side effects, most research focuses on metabolically formed nitroso- and hydroxylamino derivatives in the predisposed patient. In previous investigations it was demonstrated that photochemical decomposition of CAP in vitro by UV-A leads to formation of p-nitrobenzaldehyde (pNB), p-nitrobenzoic acid (pNBA) and p-nitrosobenzoic acid (pNOBA); the latter comprises up to 45 mol% of the starting amount of CAP. Incubation of these photoproducts in rat blood showed that pNB and pNOBA rapidly react and that PNBA is stable under these conditions. Reaction products from pNB (half-life 1.7 min) proved to be pNBA and p-nitrobenzyl alcohol (pNBOH) while pNOBA (half-life 3.7 min) was converted into p-aminobenzoic acid (pABA). Exposure of CAP in rat blood to UV-A yielded the same end products: pNBA, pABA and pNBOH. To estimate the amount of oxidative stress generated in vivo by these compounds, the ability to form methemoglobin (MetHb) in erythrocytes was tested; only pNOBA and p-hydroxylaminobenzoic acid (pHABA), a possible intermediate in the decomposition of pNOBA, proved to be reactive. Ultraviolet-A exposure of rats, after intraperitoneal injection of CAP, led to 3.6 times the basic level of MetHb. In addition, covalent binding of 3H-labeled CAP photoproducts to the skin of the back and to the ears was found, which was 9.1 and 3.2 times higher, respectively, than the dark values.(ABSTRACT TRUNCATED AT 250 WORDS)

A model for catalytically active zinc(II) ion in liver alcohol dehydrogenase: a novel "hydride transfer" reaction catalyzed by zinc(II)-macrocyclic polyamine complexes

The role of Zn ion at the active center of liver alcohol dehydrogenase has been well-defined for the first time by the comparative studies of Zn( 12)aneN3, 1 ((12)aneN3 = 1,5,9-triazacyclododecane, L,), Zn( 12)aneN4, 2 (( 12)aneN4 = 1,4,7,10-tetraazacyclododecane, L2), Zn( 14)aneN4, 3 (( 14)aneN4 = 1,4,8,1 I-tetraazacyclotetradecane, LJ, and free Zn salts, 4. Variations in Zn acidity and coordination environment in these complexes result in varying degrees of catalytic activity in the reduction of p-nitrobenzaldehyde (9) and an NAD' model compound (18) with alcohols as the sources (e.g., 2-PrOH) to p-nitrobenzyl alcohol (10) and the corresponding NADH model compounds (19 and 20), respectively. Among Zn species tested, the Zn complex of macrocyclic triamine ( 1 2)aneN3, 5 (L,-Zn11-OH)3.(TfO)3.TfOH (TfO = CF3S03-), was by far the most effective catalyst: 10 was obtained from 9 in 7820% yield (based on the concentration of Zn) in the presence of 5 (0.8 mol %) in refluxing 2-PrOH for 24 h. The Zn complex 5, also promotes the from 2-PrOH to an NAD' model compound, N-benzylnicotinamide chloride (18), to yield the 1,4-adduct, N-benzyl-l,4-dihydronicotinamide (19), almost exclusively. It is concluded, from the comparison of 5 with other Zn complexes of ( 12)aneN4 and ( 14)aneN4, that the most acidic and coordinatively least saturated Zn in LI catalytically generates zinc( 11)-alkoxide complex to facilitate the hydride transfer to the hydride acceptor on the Zn coordination sphere. The present study provides the first chemical model illustrating the significance of the Zn acidity and the steric requirement around Zn coordination sphere in the hydride transfer reaction (from alcohol) catalyzed by Zn%ontaining alcohol dehydrogenases (ADH).

Tissue factor potentiates the factor VIIa-catalyzed hydrolysis of an ester substrate.

We designed a simple and sensitive method to assay the activity of the factor VIIa-tissue factor complex, using as a substrate N alpha-benzyloxycarbonyl-L-arginine p-nitrobenzyl ester (Z-Arg-ONb) (Zur, M., and Nemerson, Y. (1978) J. Biol. Chem. 253, 2203-2209). The principle was to measure the amount of p-nitrobenzyl alcohol released during ester hydrolysis using reversed-phase high performance liquid chromatography. Z-Arg-ONb had a broad specificity for plasma serine proteases and factor IXa. Using this method, we examined the effect of tissue factor on the esterase activity of factor VIIa under various conditions. We found that tissue factor greatly potentiates the factor VIIa-catalyzed hydrolysis of Z-Arg-ONb. Phospholipids were not required for the factor VIIa-catalyzed hydrolysis of Z-Arg-ONb, even in the presence of tissue factor. The Km value of factor VIIa alone toward the ester substrate was six times higher than that of a VIIa-tissue factor complex (3.2 versus 0.54 mM), whereas the kcat value was 12 times lower than that of the VIIa-tissue factor complex (14.3 versus 173 s-1). Thus, tissue factor apparently affects the catalytic site of factor VIIa and enhances hydrolysis of the ester substrate. This enhancing effect of tissue factor disappeared on removal of the gamma-carboxyglutamic acid domain from factor VIIa, whereas the esterase activity in the absence of tissue factor was not affected by this modification. The gamma-carboxyglutamic acid domain is probably required as a potent determinant for interactions with tissue factor, even in the absence of phospholipids in the reaction mixture.

Chloramphenicol resistance in Streptomyces: cloning and characterization of a chloramphenicol hydrolase gene from Streptomyces venezuelae

A 6.5 kb DNA fragment containing a chloramphenicol-resistance gene of Streptomyces venezuelae ISP5230 was cloned in Streptomyces lividans M252 using the high-copy-number plasmid vector pIJ702. The gene was located within a 2.4 kb KpnI-SstI fragment of the cloned DNA and encoded an enzyme (chloramphenicol hydrolase) that catalysed removal of the dichloroacetyl moiety from the antibiotic. The deacylated product, p-nitrophenylserinol, was metabolized to p-nitrobenzyl alcohol and other compounds by enzymes present in S. lividans M252. Examination of the genomic DNA from several sources using the cloned 6.5 kb SstI fragment from S. venezuelae ISP5230 as a probe showed a hybridizing region in the DNA from S. venezuelae 13s but none in the DNA from another chloramphenicol producer, Streptomyces phaeochromogenes NRRLB 3559. The resistance phenotype was not expressed when the 6.5 kb SstI fragment or a subfragment was subcloned behind the lac-promoter of plasmid pTZ18R in Escherichia coli.

Biotransformation of alkyl and aryl carbonates. Microbial degradation.

An enriched mixed culture was successfully grown on model alkyl and aryl carbonates. These compounds were degraded by microorganisms at different rates. P-Chlorophenyl-2-octyl carbonate and p-nitrobenzyl-2-octyl carbonate were metabolized through the formation of p-chlorophenol and p-nitrobenzyl alcohol respectively. A strain of Acinetobacter calcoaceticus isolated from the mixed culture utilized phenyl-2-octyl carbonate by an intracellular hydrolase to phenol and 2-octanol which were further metabolized.