环境氟迁移与茶叶氟富集的关系

选择３种类型茶场进行大气氟污染与茶叶氟富集的现场监测与研究,对苏南茶区１１个茶场的土壤总氟、水溶性氟和茶叶氟富集量进行了测定。结果表明：茶叶氟富集量与来自砖瓦窑厂的大气氟污染浓度呈现高度的正相关,与土壤含氟量不呈现相关;茶树是高富集氟的植物,富集能力远高于一般植物,氟富集量可达每千克数十至数百毫克。茶叶的氟富集与氟污染应引起重视     

氟的环境地球化学行为及其对生态环境的影响

近几十年来,氟的区域性环境地球化学异常和人为环境污染所导致的植物和人体氟暴露现象引起了广泛关注,世界各国学者对不同环境介质中氟的地球化学行为进行了较为深入的研究,但仍然存在诸多争议和不确定性.本文回顾了近些年来有关氟在大气、水、土壤中的来源、数量、存在形态、迁移转化和控制因素等方面的研究成果,以及氟的地球化学行为与植物和人体氟暴露的关联性,并提出了未来有关氟的环境地球化学行为研究应优先考虑的几个方向.     

Fluorosubstitution and 7-alkylation as prospective modifications of biologically active 6-aryl derivatives of tricyclic acyclovir and ganciclovir analogues

A series of fluorine containing tricyclic analogues of acyclovir (ACV, 1) and ganciclovir (GCV, 2) were synthesized and evaluated for their activity against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) and cytostatic activity against HSV-1 thymidine kinase (TK) gene-transduced human osteosarcoma tumour cells. It was found that fluorine substitution reduced the antiviral activity, but most of the new compounds were pronounced cytostatic agents with potency and selectivity similar to those of parental ACV and GCV. Compounds 12, 13 and 16 seem to be promising as labeled substrates for (19)F NMR studies of the HSV TK-ligand interaction and/or monitoring of their metabolites in cells expressing HSV TK.     

Fluorine content in natural water in the southern Ob-Irtysh interfluve

Fluorine content in 327 sources of surface, soil-ground and underground water in the southern Ob-Irtysh interfluve has been studied. Fluctuations of fluorine concentration in water are rather considerable; their possible geochemical origins are considered. A large region with high (exceeding MPC) fluorine concentration in the sources of underground water involved in water supply to inhabited areas was discovered in the western Baraba plain. The fluorine/calcium ratios in those water samples evidence a high danger of fluorosis in the population.     

Benzaldehyde O-Alkyloximes as New Plant Growth Regulators

Fourty-two kinds of benzaldehyde O-alkyloximes derived from benzaldehydes were prepared and their biological activities were investigated. Introduction of a fluorine or bromine atom to the benzene ring of the oximes enhanced their phytotoxic activity. The O-alkyloximes with a fluorine atom at the 3 or 4 position of the benzene ring were more active than the other oximes in the GA₃-induced α-amylase induction inhibition test. In the transpiration test, 4-bromobenzaldehyde O-carboxylmethyloxime was the most active. The O-alkyloximes exhibited weak abscisic acid-like activity by inhibiting not only the germination, root growth and transpiration of higher plants but also GA₃-induced α-amylase induction in embryoless barley seeds.     

Effects of diets containing sodium fluoride on mink

Mink (Mustela vison) kits still nursing, and adult male mink were fed diets containing various levels of fluorine (as NaF) to determine the effects on health, growth and pelt quality. Different groups were fed diets containing 25.5 (control), 46.0, 111.5 or 287.0 ppm fluorine (on a wet basis) for 7-8 mo. Gross, radiographic and microscopic changes were seen in bones from some animals ingesting the higher levels of fluorine. Chemical analyses for fluorine generally reflected levels ingested. Fluorine caused no detectable differences in pelt quality. After data were evaluated, tolerance levels in the feed of not more than 50 ppm fluorine for breeding stock and 100 ppm fluorine for animals being raised only for pelts are recommended.     

Intestinal IgA+ Cell Numbers as well as IgA, IgG, and IgM Contents Correlate with Mucosal Humoral Immunity of Broilers During Supplementation with High Fluorine in the Diets

Fluoride (F), a well-recognized harmful substance, is easily absorbed by the intestinal mucosa. The intestinal mucosal immune system is equipped with unique innate and adaptive defense mechanisms that provide a first line of protection against infectious agents. Meanwhile, immunoglobulins are the major secretory products of the adaptive immune system and their levels can be a strong indicator of a disease or condition. In this study, therefore, we investigated the effects of high dietary fluorine on the numbers of immunoglobulin A-positive (IgA⁺) cells in the lamina propria of intestines (duodenum, jejunum and ileum) by immunohistochemistry as well as on the contents of immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM) in the mucosa of intestines (duodenum, jejunum, and ileum) by enzyme-linked immunosorbent assay (ELISA). A total of 280 1-day-old healthy avian broilers were randomly divided into four groups and fed on a corn–soybean basal diet as control diet (fluorine 22.6 mg/kg) or the same basal diet supplemented with 400, 800, and 1,200 mg/kg fluorine (high fluorine groups I, II, and III) in the form of sodium fluoride (NaF) for 42 days. The experimental data showed that the numbers of IgA⁺ cells as well as the IgA, IgG, and IgM contents were significantly decreased (P?<?0.01 or P?<?0.05) in the high fluorine groups II and III when compared with those of the control group. It was concluded that dietary fluorine in the range of 800–1,200 mg/kg significantly reduced the numbers of the IgA⁺ cells and the contents of aforementioned immunoglobulins in the intestines (duodenum, jejunum, and ileum) of broilers, which could finally impact the mucosal humoral immune function in the intestines by a way that reduces the lymphocyte population and/or lymphocyte activation.     

Activity of fluoro and deoxy analogues of glycerol as substrates and inhibitors of glycerol kinase

Analogues of glycerol in which each of the three hydroxy groups is successively replaced by fluorine or hydrogen have been examined as substrates or inhibitors of glycerol kinase (Candida mycoderma) to assess the ability of fluorine to mimic a substrate hydroxy group in enzyme-analogue interactions. The four diols resulting from replacement of the hydroxy groups at C-1 or C-2 of sn-glycerol by fluorine or hydrogen are weak substrates. Similar substitution of the C-3 hydroxy group gives compounds which act as competitive inhibitors of glycerol or dihydroxyacetone phosphorylation but show no activity as substrates. Comparison of the steady-state kinetic parameters of the corresponding analogues shows that replacement of a hydroxy group by either fluorine or hydrogen leads to compounds with similar activity in this system. A convenient synthesis of (+)-propane-1,2-diol is described.     

The role of fluorine in medicinal chemistry

The small and highly electronegative fluorine atom can play a remarkable role in medicinal chemistry. Selective installation of fluorine into a therapeutic or diagnostic small molecule candidate can enhance a number of pharmacokinetic and physicochemical properties such as improved metabolic stability and enhanced membrane permeation. Increased binding affinity of fluorinated drug candidates to target protein has also been documented in a number of cases. A further emerging application of the fluorine atom is the use of 18F as a radiolabel tracer atom in the exquisitely sensitive technique of Positron Emission Tomography (PET) imaging. This short review aims to bring together these various aspects of the use of fluorine in medicinal chemistry applications, citing selected examples from across a variety of therapeutic and diagnostic settings. The increasingly routine incorporation of fluorine atom(s) into drug candidates suggests a bright future for fluorine in drug discovery and development. A major challenge moving forward will be how and where to install fluorine in a rational sense to best optimise molecular properties.     

Suppressive Effects of Dietary High Fluorine on the Intestinal Development in Broilers

Fluoride (F) is a well-recognized hazardous substance. Ingested F initially acts locally on the intestines. The small intestine plays a critical role in the digestion, absorption, and defense. In this study, therefore, we investigated the effects of fluorine on the intestinal development by light microscopy, transmission electron microscopy, and histochemistry. A total of 280 one-day-old avian broilers were randomly divided into four groups and fed on a corn-soybean basal diet as control diet (fluorine, 22.6 mg/kg) or the same basal diet supplemented with 400, 800, and 1,200 mg/kg fluorine (high fluorine groups I, II, and III) in the form of sodium fluoride for 42 days. The results showed that the intestinal gross, histological, and ultrastructural changes were observed in the high fluorine groups II and III. Meanwhile, the intestinal length, weight, viscera index, villus height, crypt depth, villus height to crypt depth ratio, diameter, muscle layer thickness, and goblet cell numbers were significantly lower (p?<?0.01 or p?<?0.05), and the intestinal diameter to villus height ratio was markedly higher (p?<?0.01 or p?<?0.05) in the high fluorine groups II and III than those in control group. In conclusion, dietary fluorine in the range of 800–1,200 mg/kg obviously altered the aforementioned parameters of the intestines, implying that the intestinal development was suppressed and the intestinal functions, such as digestion, absorption, defense, or osmoregulation were impaired in broilers.     

我国重点氟污染行业排放清单与土壤氟浓度估算

工业生产排放和土壤氟高背景值导致我国部分地区氟污染严重,给生态安全和人类健康造成严重威胁.本文基于我国氟排放重点行业的生产产能,估算重点行业生产过程中氟排放量,构建我国重点行业氟排放清单,基于数据集成和融合,分析我国土壤氟背景值、氟地球化学分布和土壤氟浓度分布,并对氟污染典型区域氟污染成因及控制进行系统分析.分析发现,我国氟排放的重点行业有钢铁、磷肥和电解铝.磷肥施用的氟排放量最大,但施用面积大,浓度贡献小;电解铝行业的氟排放强度大;钢铁行业的氟排放总量大,但排放强度较小.我国大部分地区土壤氟背景值不高,环境容量大.但部分地区氟污染严重,主要是由工业氟排放和土壤氟高背景值造成,这些地区应采取相应的防控措施.     

Biochemical mechanisms of fluorine action

Biochemical mechanisms of fluorine ion action accounting for the biological role and significance of fluorine for vital activity of the organism are investigated. Results of these investigations are generalized. This trace element is shown to participate at least in two vitally important systems of the organism: the adenylate cyclase system which accounts for the cell response to neuroendocrinological information and the immune protection system providing antimicrobic resistance. Available data permit considering that cytotoxic fluorine action is based on the ability to hinder protein synthesis in eukaryotes and to stimulate peroxidation processes of biomembrane lipids. Inorganic fluorine compounds are recommended to be used with the treatment-and-prophylactic purpose for certain pathologic states, associated with its insufficient or excessive arrival into the organism.     

Landscape-geochemical approach to solving problems of environmental pollution

This paper shows under which loads of pollutants their accumulation in soils occurs with the course of time. A map of soil contamination with fluorine, reflecting the patterns of its secondary differentiation in steppe geosystems is presented. The features of the fluorine distribution in soils depending on environmental conditions, as well as the factors that ensure the self-cleaning of soils under conditions of contamination, are revealed. The necessity of reducing dust and gas emissions from the production of aluminum is identified.     

Influence of Fluorination of the Sugar Moiety on the Anti-HIV-1 Activity of 2′,3′-Dideoxynucleosides

Abstract

The advent of AIDS has prompted the search for effective anti-HIV-1 agents, and, in view of the efficacy of azidothymidine in the treatment of AIDS, 2′,3′-dideoxynucleosides and analogues thereof have been considered as the most obvious candidates for AIDS chemotherapy. Various substituents have been introduced at the 3′-position, but only the 3′-azido and 3′-fluoro derivatives were found active against HIV-1. Introduction of a fluorine in organic compounds frequently causes a dramatic change in their biological activity. The stability of the carbon-fluorine bond and the strong electronegative character of fluorine, altering the electronic properties of the substituted molecule, led us to synthesize dideoxynucleosides with a fluorine substituent at different positions. The synthe-     

Stereo-ultrastructure of the surface of HeLa cells following exposure to the MPEL of a number of trace elements

Scanning electron microscopy was used to study the surface ultrastructure of HeLa cells after the incubation with maximum-permissible concentrations (MPC) of zinc, nickel, cobalt, cadmium and fluorine for 2, 4 and 24 hours. It was established that the action of zinc, nickel, fluorine was accompanied by the ultrastructural changes in plasmalemma up to the end of experiment. The effect of the cobalt and cadmium MPC was short-term, and cells restored their typical surface morphology within 24 hours.     

Elucidation of enzyme mechanisms using fluorinated substrate analogues

A great variety of biological reactions that are physiologically important are catalyzed by enzymes. Understanding the reaction course of these enzyme-catalyzed transformations are of significant importance since the insights gained from these experiments may facilitate the design of methods to control or mimic their actions. A common strategy to study enzyme catalyses is to use fluorinated substrate analogues as mechanistic probes, since fluorine is an effective hydroxyl group mimic and can also be used to replace a hydrogen atom. Using fluorinated substrate probes have enabled researchers to obtain crucial information regarding the catalytic mechanism of enzymatic reactions. Many of these compounds are good enzyme inhibitors and have been developed into clinically useful chemotherapeutic agents. This review will discuss some examples of the use of fluorine containing compounds as mechanistic probes/enzyme inhibitors, many of which are selected from our own work.     

Fluorinated alpha-methylamino acids as 19F NMR indicators of intracellular pH

A series of nontoxic, fluorinated amino acids and their methyl esters have been used to measure intracellular pH in human peripheral blood lymphocytes by 19F NMR. Mono-, di-, and trifluoro alpha-methylalanines and their methyl esters have been characterized with respect to their spectra, the pH dependence of their fluorine resonances, and the effects of temperature and cations on the NH2pKa values. These pH indicators can be used singly or in combination to determine intracellular vs. extracellular pH profiles over a wide range (greater than 2 pH units) of extracellular pH.     

Novel cellulose derivatives. Part VI. Preparation and thermal analysis of two novel cellulose esters with fluorine-containing substituents

Two novel cellulose esters were prepared with fluorine (F)-containing substituents using homogeneous phase reaction chemistry in DMAc/LiCl. The partially substituted derivatives and their corresponding perpropionates proved to be thermoplastic polymers. The 2,2-difluoroethoxy and 2,2,3,3,4,4,5,5-octafluoropentoxy substituents were easily identified by ¹H- and ¹⁹F-NMR spectroscopy without disclosing their precise location on the anhydroglucose unit. Thermal analysis revealed modest or no crystallinity; glass transition temperatures between 53 and 113°C; and improved thermal stability as compared to their F-free counterparts.     

Fluorine compounds inhibit the conversion of active type-1 protein phosphatases into the ATPMg-dependent form.

1. The modulator protein slowly converts the glycogen-bound protein phosphatase from liver, as well as its catalytic subunit, into an inactive form that requires protein kinase FA and MgATP for reactivation. The inactivation process could be completely prevented by addition of either 0.3 mM-NaF or 0.3 mM-phenylmethanesulphonyl fluoride (PMSF). The effectiveness of the proteinase inhibitor was not due to production of free fluoride. With the catalytic subunit a half-maximal effect of either fluorine compound was obtained at 25-50 microM. 2. The inactivation process was instantaneously blocked by the addition of NaF or PMSF at any moment during the incubation of the catalytic subunit with modulator. This fluoride effect was reversible. It did not result from a decreased affinity of modulator for the catalytic subunit. The use of analogues of PMSF showed that the fluorine atom was essential, but structural aspects were also an important determinant. 3. The relative efficiency of fluorine compounds in preventing the inactivation of the catalytic subunit by modulator corresponded to their relative potency as inhibitors of the phosphorylase phosphatase activity, but the latter effect required at least 20-fold higher effector concentrations. Incubation of the catalytic subunit with 10 mM-PMSF or -NaF caused an irreversible inhibition of the enzyme. 4. It is possible to prepare stable complexes of catalytic subunit and modulator, either active or ATPMg-dependent. Both species displayed the same molecular size during gel filtration. The inactive complex could be reactivated by incubation with MgATP and protein kinase FA. NaF and PMSF increased the final extent of re-activation at limiting concentrations of the protein kinase.     

Prediction of fluorine chemical shifts in proteins

Molecular dynamics calculations have been used in an effort to estimate the change in fluorine nmr shielding when a fluorine nucleus enters the tertiary structure of a protein. Considerations of the possible interactions that can define the shift parameter change suggest that van der Waals interactions are the leading determinant of fluorine shifts in proteins, although aromatic ring currents, other magnetic anisotropies, and electrostatic field effects could result in shift distinctions of 1 ppm or smaller. Results of our studies of a fluorine-containing analogue of the ribonuclease A S-protein/S-peptide complex indicate that static structures such as those implied by crystallographic data lead to overestimates of the magnitude of the van der Waals shielding term; molecular dynamics simulations provide indications of the effects of conformational averaging in defining this term. The treatment used predicts the correct direction of the shift change when the fluorine enters this protein environment from aqueous solution and, with an experimentally supported choice of adjustable parameters, gives agreement with the magnitude of the shift.