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At least 109 records · Page 6Linked to original sources
PubMed2006

Alkyl-fluorinated thymidine derivatives for imaging cell proliferation I. The in vitro evaluation of some alkyl-fluorinated thymidine derivatives.

Derivatives of 2'-deoxyuridine that contain fluoroalkyl groups at the C5 position and derivatives of thymidine that contain fluoroalkyl groups at the N3 position were synthesized and examined in three in vitro assays designed to evaluate their potential as radiopharmaceuticals for imaging cellular proliferation. Three of the former nucleosides and five of the latter were synthesized. The three assays were as follows: (a) phosphoryl transfer assay, which showed that all three of the former nucleosides and four of the latter ones were phosphorylated by recombinant human thymidine kinase 1 (TK1) and that N(3)-(2-fluoroethyl)-thymidine (NFT202) was the most potent substrate of the eight nucleosides studied; (b) transport assay, which indicated that all eight nucleosides had good affinity for an 6-[(4-nitrobenzyl)thio]-9-beta-d-ribofuranosylpurine-sensitive mouse erythrocyte nucleoside transporter, with inhibition constants in the range of 0.02-0.55 mM; and (c) degradation assay, which showed that all but one of the former nucleosides and none of the latter were degraded by recombinant Escherichia coli thymidine phosphorylase (an enzyme that catalyzes the glycosidic bond of thymidine and 2'-deoxyuridine derivatives). From these in vitro screening assays, we selected NFT202 as a candidate for subsequent in vivo evaluation because this compound met the three minimum requirements of the in vitro screening assays and had the most potent phosphorylation activity as a substrate for recombinant human TK1.

Animals↗
PubMed2004

A fluorine scan of the phenylamidinium needle of tricyclic thrombin inhibitors: effects of fluorine substitution on pKa and binding affinity and evidence for intermolecular C-F...CN interactions.

The H-atoms of the phenylamidinium needle of tricyclic thrombin inhibitors, which interacts with Asp189 at the bottom of the selectivity pocket S1 of the enzyme, were systematically exchanged with F-atoms in an attempt to improve the pharmacokinetic properties by lowering the pK(a) value. Both the pK(a) values and the inhibitory constants K(i) against thrombin and trypsin were decreased upon F-substitution. Interestingly, linear free energy relationships (LFERs) revealed that binding affinity against thrombin is much more affected by a decrease in pK(a) than the affinity against trypsin. Surprising effects of F-substitutions in the phenylamidinium needle on the pK(a) value of the tertiary amine centre in the tricyclic scaffold of the inhibitors were observed and subsequently rationalised by X-ray crystallographic analysis and ab initio calculations. Evidence for highly directional intermolecular C-F...CN interactions was obtained by analysis of small-molecule X-ray crystal structures and investigations in the Cambridge Structural Database (CSD).

Amidines↗
PubMed1966

Toxic fluorine compounds. The use of the omega-fluorine atom in the study of the metabolism of fatty acids containing ethyl, n-propyl and isopropyl branches.

1. Some omega-fluoroalkanoic acids containing a branched ethyl, n-propyl or isopropyl group in the alpha- or beta-position have been prepared. 2. A study of the toxicity of these acids revealed that the ethyl group partially inhibited, and the n-propyl and isopropyl groups completely inhibited, the normal processes of oxidative degradation.

Animals↗
PubMed1982

Effect of maternal fluorine intake on breast milk fluorine content.

1. Breast milk samples were collected from mothers living in areas having an average of 0.2 and 1.7 microgram fluorine/ml in drinking water. The samples were analysed for their ionic and total F concentrations. 2. Ionic F was determined after microdiffusion by the fluoride-selective electrode. For total F determinations, milk samples were ashed with magnesium succinate fixative, after which the F concentration was determined as mentioned previously. 3. The median totals for F content of breast milk in the low- and high-F areas were 7.0 ng/ml (range 4.3-14.0 ng/ml, fifteen mothers) and 10.9 ng/ml (range 4.5-50.7 ng/ml, nine mothers). The median ionic F concentrations were 5.0 ng/ml (range 3.0-6.3 ng/ml, fifteen mothers) and 8.9 ng/ml (range less than 2.0-39.9 ng/ml, nine mothers) respectively. Both the total F (0.01 greater than P greater than 0.001) and ionic F (0.05 greater than P greater than 0.01) in breast milk were significantly higher in the high-F area compared to the low-F area. 4. At the ages of 1,2 and 3 months, the calculated average total daily F intakes of exclusively breast-fed infants were 4.8 and 7.3 microgram; 5.0 and 7.8 micrograms; 5.4 and 8.5 micrograms in the low- and high-F areas respectively.

Diet↗