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PubMed1985

Fluorine concentration changes in human periodontally diseased tooth roots following several treatment times with citric acid.

Citric acid conditioning of exposed cementum has become an important adjunct to the clinical management of periodontal disease, and aggressive root planing is recommended to remove hypermineralized and endotoxin-laden diseased cementum. A nuclear resonance reaction technique was used to examine fluorine concentration changes subsequent to application of citric acid (pH 1.0) to the periodontal disease-exposed cementum surfaces of human tooth roots. The technique does not require the test teeth to be sectioned, thereby permitting longitudinal assessments of changes in fluorine concentration and minimizing measurement errors due to the considerable biological variation found between individuals. Initial fluorine concentrations ranged from 0.9%-2.4%, and maxima occurred within 4-6 microns of the surface, suggesting the presence of a hypermineralized layer. Within 60 sec, the citric acid had effectively removed the hypermineralized layer and the previously observed fluctuations in fluorine concentration leveled out at 0.3%-0.5%. Although the results indicated rapid removal of the hypermineralized layer and establishment of fluorine levels normally found in healthy cementum, the experimental design did not permit appraisal of potential effects upon the organic components of periodontally-exposed cementum.

Citrates↗
PubMed2005

Incorporation of fluorine ions into hydroxyapatite by a pH cycling method.

Fluorine ions were incorporated into hydroxyapatite (HA) using a pH cycling method and the resulting materials were studied using transmission electron microscopy (TEM), X-ray diffraction (XRD), and electrochemical analysis. TEM observations showed that fluoridated hydroxyapatite (FHA) nanoparticles with a narrow particle size distribution were obtained at several different levels of fluorine incorporation. Significant particle growth was observed following calcining at 1200 degrees C. The TEM data revealed that, instead of forming laminated structures, a mixture of HA and FA was obtained, and that this mixture transformed into a single homogeneous FHA phase upon heating. It was found that the efficiency of fluorine incorporation did not vary significantly with the initial HA particle size, but increased as the fluorine content of the initial solution was increased. A relatively low fluorine incorporation efficiency, approximately 60%, was attained for most of the FHA samples and this was attributed to the short holding time at each pH cycle and the limited number of pH cycles employed in the current study.

Biocompatible Materials↗
PubMed1992

Effect of fluorine substitution on benzo[j]fluoranthene genotoxicity.

The metabolism and mutagenic activity of 4-fluorobenzo[j]fluoranthene (4F-B[j]F) and 10-fluorobenzo[j]fluoranthene (10F-B[j]F) were evaluated and compared with benzo[j]fluoranthene (B[j]F) using an identical rat liver homogenate preparation. Previous studies have shown that the major genotoxic metabolites of B[j]F are the 4,5- and 9,10-dihydrodiol. The 9,10-dihydrodiol was the principal metabolite formed in the case of 4F-B[j]F, while the 4,5-dihydrodiol was the principal metabolite formed in the metabolism of 10F-B[j]F. Studies on the relative genotoxicity of these fluorinated derivatives were performed to indirectly determine the possible contribution of the 4,5- and 9,10-dihydrodiol in the activation of B[j]F to a genotoxic agent. In the presence of microsomal activation, both of these fluorinated derivatives of B[j]F were more mutagenic in S. typhimurium TA97a, TA98 and TA100 than B[j]F. However, differences in mutagenic potency were observed between 4F- and 10F-B[j]F. 10F-B[j]F had similar mutagenic potency to 4F-B[j]F in TA97a and TA98 at doses associated with the linear portion of the dose response curve. However, a slightly higher mutagenic response was observed with 10F-B[j]F in TA98 at doses above 5 nmol. In contrast, 4F-B[j]F was more active than 10F-B[j]F as a mutagen in TA100. The tumor-initiating activity of these analogs on mouse skin was assessed at doses of 2.0, 1.0 and 0.3 mumol. Skin irritation was observed with the fluorinated B[j]F derivatives at doses above 0.3 mumol. At a dose of 0.3 mumol, 4F-B[j]F exhibited tumorigenic activity which was similar to B[j]F. In contrast, 10F-B[j]F was less active than B[j]F at all three doses assayed. Both fluorinated derivatives of B[j]F formed higher levels of DNA adducts in vivo in mouse skin than B[j]F. A modified 32P-postlabeling method was required to detect fast migrating B[j]F:DNA adducts that went undetected in previous studies. The level of DNA adducts formed from 4F-B[j]F was considerably greater than the levels observed with 10F-B[j]F. This is consistent with the greater mutagenic activity in S. typhimurium TA100 and tumor-initiating activity exhibited by 4F-B[j]F. These studies suggest that fluorine substitution may significantly alter the intrinsic genotoxicity of the 4,5- and 9,10-dihydrodiol of B[j]F. These data also imply that B[j]F may be primarily activated via the formation of the 9,10-dihydrodiol metabolite. This pathway of activation is inconsistent with our previous studies which indicate that the 4,5-dihydrodiol is the most important pathway of activation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Accelerated oxide growth on titanium implants during autoclaving caused by fluorine contamination.

Titanium implants were occasionally found to be strongly discoloured after autoclaving. The discolouration is shown to be due to an accelerated growth of the surface oxide that covers the implants. Oxide thicknesses up to 650 A have been observed, i.e. more than ten times thicker than on normal implants. By applying surface sensitive spectroscopies (SIMS and XPS or ESCA) it is also shown that these oxide films contain considerable amounts of fluorine, alkali metals and silicon. Screening tests with alkali-halide solutions identify fluorine as the impurity responsible for the accelerated oxide growth. Discolouration after autoclaving can be observed for fluorine contaminations down to the ppm level. In those cases where discolouration was observed in the clinical situation, the source of fluorine was the textile cloths in which the titanium implant storage box had been wrapped during the autoclaving procedure. The cloths contained residual Na2SiF6 which had been used as an additive to the rinsing water used in the last step of the cloth laundry procedure. Since the biocompatibility of titanium implants is closely related to their surface oxides it is advisable to avoid all sources of fluorine in the implant preparation procedures.

Color↗
PubMedDate not supplied

One-dimensional chemical shift imaging of fluorinated neuroleptics in rat brain in vivo by 19F NMR rotating frame zeugmatography.

One-dimensional chemical shift imaging reflecting local tissue contents of the fluorinated neuroleptics fluphenazine and trifluoperazine in rat brain was obtained noninvasively in vivo using one-dimensional 19-fluorine (19F) nuclear magnetic resonance (NMR) rotating frame zeugmatography. Activities of these fluorinated neuroleptics showed a differential distribution in the brain, maximal in the deep structures presumably within the basal ganglia. An additional resonance of an unidentified fluorinated metabolite was localized to the subcutaneous tissue. The present data indicate the feasibility of chemical shift imaging of fluorinated neuroleptics using a high field NMR system and the potential for future development of neurotransmitter imaging by NMR.

Animals↗
PubMed1985

Effects of a fluorinated bisphosphonate on bone remodeling in vivo.

A new fluorinated bisphosphonate, difluoromethylene bisphosphonate (F2MBP), was studied for its effects on physiologic bone remodeling in the actively growing rat tibia. Young male Sprague-Dawley rats were given daily subcutaneous injections of either saline (control) or 30 mg/kg per day of F2MBP, dichloromethylene bisphosphonate (Cl2MBP), or 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) for 30 days. Microradiographs of the epiphysealmetaphyseal region of tibiae from animals treated with either F2MBP or Cl2MBP demonstrated increased radiodensity but, unlike those treated with HEBP, without an increase in the width of the epiphyseal growth plate. Quantitative analyses of these microradiographs showed that there was an increase of calcified tissue in the metaphyseal region in all diphosphonate groups when compared with controls. However, the HEBP-treated animals exhibited significantly less increase than either F2MBP-treated or Cl2MBP-treated rats. In addition, the total area of calcified tissue in the diaphyseal transverse sections was greater in the F2MBP-treated animals than in controls. Elemental calcium, phosphorus, and fluorine, as detected by the electron probe, also increased in the metaphyseal region of the F2MBP-treated animals, but no significant differences in the calcium: phosphorous ratio were found among the control, F2MBP, and Cl2MBP treatment groups, indicating no alterations in the chemical composition of bone. The greater amount of fluorine in the tibiae of F2MBP-treated animals reflected the presence of the F2MBP molecule. Thus, this study has demonstrated that this new fluorinated bisphosphonate, like Cl2MBP, inhibits physiologic bone remodeling without disturbing mineralization. Furthermore, the presence of fluorine in F2MBP allows the precise localization of the incorporation of the bisphosphonate within the bone.

Animals↗
PubMed2005

Fluorine-substituted dihydrobicyclomycins: synthesis and biochemical and biological properties.

Many studies show that selective introduction of fluorine within pharmacological agents leads to improved activities. In this study, we determine the effects of aryl fluorine substitution in 5a-(benzylsulfanyl)-dihydrobicyclomycin (3) on the in vitro inhibition of Escherichia coli rho-dependent ATPase activity. Compound 3 is an analog of bicyclomycin (1), which is the only known selective inhibitor of rho, and 1 and 3 have comparable in vitro inhibitory activities. We demonstrate that aryl fluorine substitution of 3 leads to increase in inhibitory activity but that the beneficial effects due to fluorine were dependent upon the site and number of fluorine substituents. The bioactivities are rationalized in terms of the bond moment created by the aryl fluoride bond within the 5a-aryl dihydrobicyclomycin-rho-binding pocket. Use of this hypothesis led to the design of dihydrobicyclomycin derivatives with superior in vitro rho inhibitory activities.

Bridged Bicyclo Compounds, Heterocyclic↗
PubMed2004

A study on dielectric characteristics of fluorinated polyimide thin film.

In this work, the effects of fluorination of polyimide thin films on surface and dielectric characteristics were studied using X-ray photoelectron spectroscopy (XPS) and dielectric spectrometry, respectively. The thermal and mechanical properties of the film were characterized by thermogravimetric analysis (TGA) and tensile strengths, respectively. The fluorine content of the polyimide thin film was increased with increasing treatment concentration, resulting in decreasing dielectric constant of the film. It was found that the replacement of fluorine led to the decrease of the local electronic polarizability of polyimide, or to the increase of the free volume, which can be attributed to the relatively large size of fluorine. Nevertheless, the fluorination did not significantly affect thermal or mechanical properties of the polyimide film under mild conditions in this system.

Chemical Phenomena↗
PubMed2006

Characterisation of fluorine containing glasses by 19F, 27Al, 29Si and 31P MAS-NMR spectroscopy.

OBJECTIVE: The aim of this study is to characterise a range of model and commercially available glasses used to form glass (ionomer) polyalkenoate cements. METHODS: A range of model fluoro-alumino-silicate glasses that form the basis of glass (ionomer) polyalkenoate cements and five commercial glasses have been characterised by 29Si, 27Al, 31P and 19F Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR). RESULTS: The 29Si spectra indicate a predominantly Q33Al and Q44Al structure where the Q33Al species represents a silicon with one non-bridging oxygen and three Si-O-Al linkages and the Q44Al species a silicon with four Si-O-Al bonds. Aluminium was found in predominantly four coordinate sites, but glasses with high fluorine contents showed an increasing proportion of five and six coordinate aluminium. In phosphate containing glasses the phosphorus was present as Al-O-PO3(2-) type species indicating local charge compensation of Al3+ and P5+ in the glass structure. 19F MAS-NMR indicated the presence of F-Ca(n), Al-F-Ca(n), F-Sr(n), Al-F-Sr(n) and Al-F-Na(n) species where F-M(n) indicates a fluorine surrounded by n next nearest neighbour cations and Al-F-M(n) represents a fluorine bonded to aluminium with the metal, M in close proximity charge balancing the tetrahedral AlO3F species. The proportion of Al-F-M(n) species increased with increasing fluorine content of the glass and lower non-bridging oxygen contents. There was no evidence of Si-F bonds in any of the glasses. CONCLUSIONS: The local structure of the phosphate containing glasses with regard to fluorine, calcium, strontium and phosphate is similar to that of fluorapatite the mineral phase of tooth. This may explain the ease with which these glasses crystallize to fluorapatites and the recently observed mineralization of glass polyalkenoate cements found in vivo.

Aluminum↗
PubMed2002

Behavior of fluorinated analogs of L-(3,4-dihydroxyphenyl)alanine and L-threo-(3,4-dihydroxyphenyl)serine as substrates for Dopa decarboxylase.

We have determined the kinetic parameters for Dopa decarboxylase (DDC) of three ring-fluorinated analogs of 3,4-dihydroxyphenylalanine (Dopa). The rank order of catalytic efficiency of decarboxylation (k(cat)/K(m)) is Dopa>6-F-Dopa>2-F-Dopa>5-F-Dopa. This rank is consistent with previous in vivo and in vitro studies which indicate that, of the fluorinated analogs, 6-F-Dopa has pharmacokinetics that are most suited for positron emission tomographic (PET) evaluation of dopamine function. The effectiveness of PET as a diagnostic tool, the convenient half-life of (18)F (110 min) and the favorable pharmacokinetics of 6-[(18)F]FDOPA have combined to make this an extremely valuable reagent to study dopaminergic activity. The reactions of the related fluorinated DOPS analogs show that, while 6-F-threo-3,4-(dihydroxyphenyl)serine (DOPS) is decarboxylated at approximately the same rate as the non-fluorinated substrate, 2-F-threo-DOPS is not converted into the corresponding amine. In both cases a Pictet-Spengler condensation with the pyridoxal 5(')-phosphate (PLP) cofactor occurs to produce tetrahydroisoquinolines. Condensation of fluorinated catecholamines and catechol amino acids with endogenous aldehydes will be investigated as an approach to study possible mechanisms of L-Dopa-linked neurotoxicity.

Dihydroxyphenylalanine↗
PubMed2001

Fluorine in the soils of the White Sea Basin and bioindication of pollution.

Assessment of the pollution level of soils and vegetation by fluorine and heavy metals and also of the state of the soil microflora in the impact zone of Kandalaksha aluminium factory is discussed. The significant pollution of natural media by fluorine in the basin of the White Sea is established. Concentration of the total fluorine in the organogenic horizon of the Al-Fe-humus podzol soil at a distance of 20 km in the northern direction from the source of emission exceeds the background level by a factor of 3. In the epicentre of emission the amount of total fluorine in the soil exceeds the background level by a factor of 7-8 (Tolerable Amount: 4-5-fold). It is noted that the soil becomes more alkaline under the influence of fluorine and the increased content of chromium along the soil profile exceeds PC by a factor of 3 in the vicinity of the factory. The differences in the dimensions of bacterial and fungi biomass along the gradient of pollution were not revealed in the impact zone. But the changes in the taxonomic structure of fungi and in the level of their domination along the gradient of pollution were estimated. Floristic composition of the soil algae is represented mainly by unicellular green algae with Chlamydomonas elliptica and Bracteacoccus minor predominating.

Air Pollutants↗
PubMed2003

Volcanogenic fluorine in rainwater around active degassing volcanoes: Mt. Etna and Stromboli Island, Italy.

Many studies have assessed the strong influence of volcanic activity on the surrounding environment. This is particularly true for strong gas emitters such as Mt. Etna and Stromboli volcanoes. Among volcanic gases, fluorine compounds are potentially very harmful. Fluorine cycling through rainwater in the above volcanic areas was studied analysing more than 400 monthly bulk samples. Data indicate that only approximately 1% of fluorine emission through the plume is deposited on the two volcanic areas by meteoric precipitations. Although measured bulk rainwater fluorine fluxes are comparable to and sometimes higher than in heavily polluted areas, their influence on the surrounding vegetation is limited. Only annual crops, in fact, show some damage that could be an effect of fluorine deposition, indicating that long-living endemic plant species or varieties have developed some kind of resistance.

Air Pollutants↗
PubMed1996

Molecular dynamics simulations of silicon-fluorine etching.

Molecular dynamics simulations of the reactions between gaseous fluorine atoms and (SiFx)n adsorbates on the Si(100) - (2 x 1) surface are performed using the SW potential and compared to simulations with the WWC reparameterization of the SW potential. Theoretical and experimental work has demonstrated that the reactive fluorosilyl layer during silicon-fluorine etching is composed of tower-like adspecies of SiF, SiF2 and SiF3 groups. The objective of the simulations is to determine how the chemical composition, mechanism of formation, and energy distribution of the etched gas-phase products depend on the identity of the reacting adsorbate, the incident kinetic energy, and the parameterization of the potential energy function. Three reactions are simulated: F(g) + SiF3(a), F(g) + SiF2-SiF3(a), and F(g) + SiF2-SiF2-SiF3(a). SiF4 is the major product and Si2F6 and Si3F8 are minor products. In Si2F6 and Si3F8, the silicon-fluorine bond that is formed is stronger than the silicon-silicon bond in the molecule and, therefore, the majority of these products have enough energy to dissociate and will fragment before reaching the detector. An SN2-like mechanism is the primary mechanism responsible for the formation of SiF4, Si2F6, and Si3F8. In addition, at higher energies, the simulations have discovered a previously unknown mechanism for the formation of SiF4, which involves an insertion between a silicon-silicon bond. The results of the simulations with the two potentials differ quite substantially in their prediction of the reactivity of the adsorbates. The SW potential predicts a 2- to 3-eV lower energy threshold for reaction and a much higher reaction cross-section, especially for the SiF4 product. These results are explained in terms of the differences in the potential energy functions used to describe the silicon-fluorine interactions. In addition, the results are compared to experimental data on silicon-fluorine etching.

Computer Graphics↗
PubMed2001

NMR study on the interaction of 1,4-cubanedicarboxylic acid and its esters with elemental fluorine. The synthesis of dimethyl 2-fluorocubane-1,4-dicarboxylate.

Elemental fluorine can be successfully used for fluorination of cubane derivatives. The nature of the products depends on the fluorination conditions: in CH3CN at -20 to -30 degrees C, dimethyl 2-fluorocubane-1,4-dicarboxylate was obtained from dimethyl ester of 1,4-cubanedicarboxylic acid; in CF3COOH at -12 to -15 degrees C in the presence of alkali metal acetates, 1,4-cubanedicarboxylic acid and its dimethyl and diethyl esters gave complex mixtures of fluorinated cubane products. Our investigation by 1H and 19F NMR spectroscopy and spectra computer simulation revealed production of mono- and difluorinated cubanes. Fluorine-containing cubane derivatives were also found with extra substituents in other than 1 and 4 positions.

Bridged-Ring Compounds↗
PubMed2006

Synthesis and hemocompatibility of biomembrane mimicing poly(carbonate urethane)s containing fluorinated alkyl phosphatidylcholine side groups.

In this article, we designed and synthesized biomembrane mimicing segmented poly(carbonate urethane)s containing fluorinated alkyl phosphatidylcholine (PC) side groups. To obtain these novel poly(carbonate urethane)s, a new diol with a long side chain fluorinated alkyl phosphatidylcholine polar headgroup (2-[2-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluoro-10-ethoxy-decyloxy-N-(2-hydroxy-1-hydroxymethyl-1-methyl-ethyl)-acetamide] phosphatidylcholine, HFDAPC) was first synthesized and characterized. Then a series of poly(carbonate urethane)s containing fluorinated alkyl phosphatidylcholine side groups were synthesized using methylenebis(phenylene isocyanate) (MDI), poly(1,6-hexyl-1,5-pentyl carbonate) diol (PHPCD), 1,4-butandiol (BDO), and HFDAPC. The obtained fluorinated phosphatidylcholine poly(carbonate urethane)s (FPCPCU) possessed high molecular weight, narrower molecular weight distribution, and good mechanical properties as characterized by GPC and Instron, showing an increased hydrophilicity and a possible arrangement of surface structure as characterized by water contact angle. XPS results indicated that the phosphatidylcholine polar headgroups have been indeed pulled out to the surface with the help of the migration of the fluorinated side chain that was directly connected with the phosphatidylcholine polar headgroup. A preliminary result by protein adsorption and platelet adhesion experiments suggested that only 5 approximately 12.5 mol % phosphatidylcholine could be enough for good hemocompatibility. The current work demonstrates a new synthetic approach that can be used to bring the bioactive PC groups to the surface of the PC-containing polyurethanes more effectively.

Acetic Acid↗
PubMed2002

New method of fluorination using potassium fluoride in ionic liquid: significantly enhanced reactivity of fluoride and improved selectivity.

We have found the new nucleophilic fluorination reaction of some halo- and mesylalkanes to the corresponding fluoroalkanes with KF in the presence of [bmim][BF4] under various reaction conditions. 2-(3-Methanesulfonyloxypropoxy)naphthalene (1) was used as a model compound to optimize this fluorination reaction. Whereas the fluorination of the mesylate 1 with KF in an organic solvent such as CH3CN at 100 degrees C occurred hardly even after 24 h, the same reaction in ionic liquids, [bmim][BF4], as a reaction solvent was completed within 1.5 h, affording the wanted product 2-(3-fluoropropoxy)naphthalene 2a (85%) together with the alkene byproduct 2c (10%). Very interestingly, however, the addition of water (5 equiv) completely eliminated the formation of the undesired alkene 2c and thus gave higher yield of 2a (92%, entry 2). The use of acetonitrile as a cosolvent did not affect the reactivity of the fluorination. The presence of a proper amount of cosolvent was rather desirable (94% yield of 2a). We performed fluorination reactions with other ionic liquids ([bmim][PF6], [bmim][SbF6], [bmim][OTf], and [bmim][N(Tf)2], and two other cosolvents, to find the optimal ionic liquid and cosolvent. Nine different compounds were examined, including the 10 g-synthesis of 2-(fluoromethyl)naphthalene in 93% of isolated yield.

Chemistry, Organic↗
PubMed2006

Enantioselective synthesis of an all-syn four vicinal fluorine motif.

Alkanes bearing multiple vicinal fluorine atoms at adjacent stereocenters may be considered intermediate between alkanes and perfluoroalkanes, and as a class, their chemistry and behavior remain to be explored. We report here a stereoselective synthesis of an all-syn four vicinal fluorine motif as a single enantiomer. The four vicinal fluorine compound was amenable to single-crystal X-ray analysis, and the resulting structure displays gauche relationships between all four fluorines, consistent with the fluorine gauche effect, and CF...HC hydrogen bonding between adjacent fluoroalkyl chains.

Crystallography, X-Ray↗
PubMed1994

The effect of fluorine substitution on the metabolism and antimalarial activity of amodiaquine.

Amodiaquine (AQ) (2) is a 4-aminoquinoline antimalarial which causes adverse side effects such as agranulocytosis and liver damage. The observed drug toxicity is believed to be related to the formation of an electrophilic metabolite, amodiaquine quinone imine (AQQI), which can bind to cellular macro-molecules and initiate hypersensitivity reactions. 5'-Fluoroamodiaquine (5'-FAQ, 3), 5',6'-difluoroamodiaquine (5',6'-DIFAQ,4), 2',6'-difluoroamodiaquine (2',6'-DIFAQ,5), 2',5',6'-trifluoroamodiaquine (2',5',6'-TRIFAQ, 6) and 4'-dehydroxy-4'-fluoroamodiaquine (4'-deOH-4'-FAQ,7) have been synthesized to assess the effect of fluorine substitution on the oxidation potential, metabolism, and in vitro antimalarial activity of amodiaquine. The oxidation potentials were measured by cyclic voltammetry, and it was observed that substitution at the 2',6'- and the 4'-positions (2',6'-DIFAQ and 4'-deOH-4'-FAQ) produced analogues with significantly higher oxidation potentials than the parent drug. Fluorine substitution at the 2',6'-positions and the 4'-position also produced analogues that were more resistant to bioactivation. Thus 2',6'-DIFAQ and 4'-deOH-4'-FAQ produced thioether conjugates corresponding to 2.17% (SD: +/- 0.27%) and 0% of the dose compared with 11.87% (SD: +/- 1.31%) of the dose for amodiaquine. In general the fluorinated analogues had similar in vitro antimalarial activity to amodiaquine against the chloroquine resistant K1 strain of Plasmodium falciparum and the chloroquine sensitive T9-96 strain of P. falciparum with the notable exception of 2',5',6'-TRIFAQ (6). The data presented indicate that fluorine substitution at the 2',6'-positions and replacement of the 4'-hydroxyl of amodiaquine with fluorine produces analogues (5 and 7) that maintain antimalarial efficacy in vitro and are more resistant to oxidation and hence less likely to form toxic quinone imine metabolites in vivo.

Amodiaquine↗