Second-harmonic generation from organic molecules incorporated in sol-gel matrices

Orientation of optically nonlinear organic molecules inside sol-gel matrices upon application of an external D.C. electrical field is demonstrated for the first time. The quadratic nonlinear response of silicon oxide or transition metal oxide based gels containing organic molecules has been determined from Electric Field Induced Second Harmonic (EFISH) measurements. Large concentrations of Optically Nonlinear Organic Molecules (ONOM) have been either incorporated inside the macromolecular network or chemically bonded to the oxide backbone of the gels. These results demonstrate the feasibility of permanently poled doped sol-gel matrices. Moreover, EFISH measurements performed on organic molecules appear to be a useful tool for monitoring the changes occurring during sol-gel transformations.     

Analysis of DNA adducts by accelerator mass spectrometry in human breast tissue after administration of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and benzo[a]pyrene

Epidemiological evidence has suggested an association between meat consumption and the risk of breast cancer. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a heterocyclic amine found in cooked meat, has been implicated in the aetiology of breast cancer and has been shown to induce tumour formation in rodent mammary glands. In addition, polycyclic aromatic hydrocarbons, such as benzo[a]pyrene (B[a]P) which has also been shown to induce tumour formation at a number of sites in rodents including the breast, are produced during the cooking of meat through the pyrolysis of fats. The aim of this study was to examine the bioavailability of these compounds to human breast tissue and their ability to bind to DNA to form DNA adducts. Patients undergoing breast surgery at York District Hospital were orally administered prior to surgery a capsule containing 20 μg of ¹⁴C PhIP (182 kBq, specific activity 2.05 GBq/mmol) or 5 μg of ¹⁴C B[a]P (36 kBq, specific activity 1.81 GBq/mmol). At surgery, normal and tumour breast tissue was resected and tissue concentrations of carcinogen measured by liquid scintillation counting and DNA adduct levels by accelerator mass spectrometry (AMS) were subsequently determined. It was found that both ¹⁴C PhIP and ¹⁴C B[a]P were able to reach the target organ where they had the ability to form DNA adducts. The level of adducts ranged from 26.22–477.35 and 6.61–208.38 adducts/10¹² nucleotides following administration of ¹⁴C PhIP and ¹⁴C B[a]P, respectively, with no significant difference observed between levels in normal or tumour tissue. In addition, the data obtained in this study were comparable to adduct levels previously found in colon samples following administration of the same compounds to individuals undergoing colorectal surgery. This is the first report that these two carcinogens bind to human breast DNA after administration of a defined low dose.     

Cloning of aroG, the gene coding for phospho-2-keto-3-deoxy-heptonate aldolase(phe), in Escherichia coli K-12, and subcloning of the aroG promoter and operator in a promoter-detecting plasmid

Defective transducing phages carrying aroG, the structural gene for phenylalanine (phe)-inhibitable phospho-2-keto-heptonate aldolase (EC 4.1.2.15; previously known as 3-deoxy-D-arabinoheptulosonate-7-phosphate synthetase[phe]), have been isolated, and DNA from two of these phages has been used to construct a restriction map of the region from att lambda to aroG. A 7.6-kb PstI-HindIII fragment from one of these phages was cloned into pBR322 and shown to contain aroG. The location of aroG within the 7.6 kb was established by subcloning and Tn3 transpositional mutagenesis. A fragment carrying the aroG promoter and operator has been cloned into a high copy number promoter-cloning vector (pMC489), and the resulting aroGpo-LacZ' (alpha) fusion subcloned in a low copy number vector. Strains with this fusion on the low copy number vector exhibit negative regulation of beta-galactosidase expression by both phenylalanine and tryptophan and positive regulation by tyrosine in a tyrR+ background.     

Metabolism of halohydroquinones inRhodococcus chlorophenolicus PCP-1

The actinomyceteRhodococcus chlorophenolicus PCP-1 metabolises pentachlorophenol into ultimate inorganic end products via tetrachloro-p-hydroquinone. This intermediate was further dehalogenated in the cytoplasm requiring reductant in the cell free system. Tetrafluoro-p-hydroquinone and tetrabromo-p-hydroquinone were also dehalogenated. Chlorophenol analogs, thiol blocking agents and molecular oxygen inhibited the activity. The dehalogenating reactions led to 1,2,4-trihydroxybenzene, which was further metabolized into maleic acid.Abbreviations PCP pentachlorophenol - TeCH tetrachloro-p-hydroquinone - TeFH tetrafluoro-p-hydroquinone - TeBH tetrabromo-p-hydroquinone - THB trihydroxybenzene     

Lipase-catalyzed synthesis of aromatic polyesters

The enzymatic synthesis of aromatic polyesters by direct polyesterification between a diacid and a diol is described. The effects of the type of substrate, type and quantities of lipase, temperature, vacuum, and reaction time on the synthesis of aromatic polyesters were studied in detail. Among three lipases investigated, only Novozym 435 worked well for aromatic polyester synthesis. Temperature and vacuum played an important role in obtaining a high molar mass of the aromatic polyesters. Furthermore, with isophthalic acid and 1,6-hexanediol as substrates, the mass average molar mass of the polyester obtained increased with an increase in the lipase quantity up to 0.375 g (11.7%, w/w of total reactor contents). The mass average molar mass of the polyester was as high as 50000 g mol⁻¹ in 168 h, with a polydispersity of PD ≈ 1.4. Received 27 January 1998/ Accepted in revised form 19 May 1998     

A new methoxylated flavone from Lonicera hypoglauca and its chemotaxonomic significance

Phytochemical investigation of the stems and leaves of Lonicera hypoglauca Miq. led to the isolation of one novel methoxylated flavone, acunminatin (7,2′,4′-trihydroxyl-5,5′- methoxyflavone) (1), and fourteen known compounds (2–15), including six flavonoids (mearnsetin 2, kaempferol 3, acacetin 4, 5,7,3′,4′-tetramethoxyflavone 5, tricin 6, and 5,7,3′,4′,5′-pentamethoxyflavone 7), two coumarins (umbelliferone 8 and scopoletin 9), two phenylpropanoids (trans-ferulic acid 10 and chlorogenic acid 11), two iridoid glycosides (loganin 12 and sweroside 13), and two triterpenoids (uvaol 14 and ursolic acid 15). The structures of the compounds were identified by spectroscopic analysis and by comparing their spectral data with those reported in the literature. Five of these compounds (1, 2, 4, 5, and 7) were isolated from the L. genus for the first time, and compounds 6–8 and 14–15 were isolated for the first time from L. hypoglauca. The chemotaxonomic significance of the isolated compounds in the L. genus and the Caprifoliaceae family are discussed herein.     

Recent Advances in the Development of a Diagnostic Test for Irradiated Foodstuffs

Recent advances in the development and application of diagnostic tests for irradiated foodstuffs are reviewed. Exposure of water, the major chemical constituent of most foodstuffs to a source of ionising radiation initially generates the highly reactive radical species H', -OH and e^- (aq) which react very rapidly with a wide variety of biological molecules. The detection of foodstuffs subjected to irradiation processing requires the identification and/or quantification of ‘unnatural’ chemical species (i.e. those not usually formed by normal metabolic processes) produced by the attack of ·OH radical or e^-(aq) on suitable ‘target’ molecules. Modern methods for the analysis of a series of these ‘unnatural’ products arising from the interaction of radiolytically-generated ·OH radical or e^-(aq) with polyunsaturated fatty acids, DNA, aromatic compounds and other biologically important scavenger molecules are examined. It is concluded that the analytical test to be conducted is highly dependent on the nature of the foodstuff to be tested.     

Monooxygenation of aromatic compounds by flavin‐dependent monooxygenases

Many flavoenzymes catalyze hydroxylation of aromatic compounds especially phenolic compounds have been isolated and characterized. These enzymes can be classified as either single‐component or two‐component flavin‐dependent hydroxylases (monooxygenases). The hydroxylation reactions catalyzed by the enzymes in this group are useful for modifying the biological properties of phenolic compounds. This review aims to provide an in‐depth discussion of the current mechanistic understanding of representative flavin‐dependent monooxygenases including 3‐hydroxy‐benzoate 4‐hydroxylase (PHBH, a single‐component hydroxylase), 3‐hydroxyphenylacetate 4‐hydroxylase (HPAH, a two‐component hydroxylase), and other monooxygenases which catalyze reactions in addition to hydroxylation, including 2‐methyl‐3‐hydroxypyridine‐5‐carboxylate oxygenase (MHPCO, a single‐component enzyme that catalyzes aromatic‐ring cleavage), and HadA monooxygenase (a two‐component enzyme that catalyzes additional group elimination reaction). These enzymes have different unique structural features which dictate their reactivity toward various substrates and influence their ability to stabilize flavin intermediates such as C4a‐hydroperoxyflavin. Understanding the key catalytic residues and the active site environments important for governing enzyme reactivity will undoubtedly facilitate future work in enzyme engineering or enzyme redesign for the development of biocatalytic methods for the synthesis of valuable compounds.     

ASSESSING THE CONTAMINATED LEVELS AND RISK OF TYPICAL CONTAMINANTS IN THE UPPER REACHES OF THE YANGTZE RIVER北大核心CSCD

We generally reviewed the distributions and potential risks of heavy metals, polycyclic aromatic hydrocarbons (PAHs) and phthalic acid esters (PAEs) in the upper reaches of the Yangtze River based on recent studies. The distribution of heavy metals varied significantly with locations and types of mediums, and contents of some metals exceeded the limits in food. The contents of PAHs in the upper reaches of the Yangtze River were in line with those in the lower reaches. Low molecular weight PAHs were predominant in surface water, while high molecular weight PAHs were predominant in sediments, indicating low molecular PAHs may pose greater risks to aquatic ecosystems. DEHP and DBP were the predominant monomers of PAEs in surface water and sediments, and BBP and DBP ranked first and second respectively in fish bodies. The results of risk assessment also indicated that monomers such as DBP and DnBP had greater risk than DEHP. Over all, heavy metals and organic pollutants were widely distributed in the aquatic environment in the upper reaches of the Yangtze River, which may pose potential risks to the ecosystem. © 2019, Institute of Hydrobiology, Chinese Academy of Sciences. All rights reserved.     

Immunomodulation of carcinogens-induced steroids-dependent human diseases

The experimental and clinical data about antibodies against environmental chemical carcinogens and endogenous steroids are represented. The conception of immunomodulation of carcinogens- and steroids-dependent human diseases is proposed. It is postulated that antibodies to polycyclic aromatic hydrocarbons and heterocyclic amines in cooperation with antibodies to cholesterol, sex hormones, mineralo- and glucocorticoids stimulate or inhibit cancer, malformation, cardiovascular and autoimmune diseases depending on their personal combination. It is recommended to use immunoassay of these antibodies for the human diseases prediction. The alternative approaches for prevention using the probiotics transformed by anti-carcinogen antibodies are substantiated.