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Biomedical subjects

R J Kempton

Publications and source records attributed to R J Kempton.

11 recordsLinked to original sources
PubMed1984

A fluorescent analogue of methotrexate as a probe for folate antagonist molecular receptors.

A dansyl-L-lysine analogue of methotrexate, N alpha-(4-amino-4-deoxy-10- methylpteroyl )-N epsilon-(5-[N,N-dimethylamino]-1-naphthalenesulfonyl)-L-lysine, is a potent inhibitor of murine L1210 dihydrofolate reductase. The dansyl fluorescence emission was enhanced approximately 3-fold with a 10 nm blue shift upon binding to L1210 dihydrofolate reductase. The fluorescent analogue was only 10-fold less potent than methotrexate in inhibiting the growth of methotrexate-sensitive and -resistant L1210 cells and competes effectively for [3H]methotrexate transport with a Ki of 7.02 microM, a value virtually identical to the Kt for methotrexate in both cell lines. In addition, strong dansyl fluorescence was found to be associated with dihydrofolate reductase from methotrexate-resistant, dihydrofolate reductase-overproducing L1210 cells following incubation of viable cells with the fluorescent methotrexate analogue for 4 hr. The results demonstrate that the dansyl-L-lysine analogue of methotrexate was rapidly transported into L1210 cells where it formed a high-affinity, fluorescent complex with intracellular dihydrofolate reductase.

Animals↗
PubMed1983

Fluorescent analogues of methotrexate: characterization and interaction with dihydrofolate reductase.

The dansylated derivatives of lysine and ornithine analogues of methotrexate exhibit fluorescence properties characteristic of the dansyl moiety with an excitation at 328 nm and an emission maximum at 580 nm in aqueous media. As in the case of dansyl amino acids, the fluorescence emission is dependent upon the polarity of the medium. In solvents of low dielectric constant there is an enhancement of the dansyl fluorescence intensity as well as a shift to shorter wavelengths. The dansylated analogues show a reduction in the quantum yields as compared to N epsilon-dansyl-L-lysine and 5-(N,N-dimethylamino)-1-naphthalenesulfonic acid. The absorption spectra of the two dansyl analogues are similar to the spectra of the parent basic amino acid precursors but with reduced molar extinction values. The two fluorescent analogues of methotrexate were found to be potent inhibitors of purified dihydrofolate reductases from Lactobacillus casei and from chicken liver. The binding of these fluorescent analogues to either dihydrofolate reductase resulted in 10-15-nm blue shift of the ligand emission maxima and a 2-5-fold enhancement of the emission. These fluorescent properties of the bound ligands indicate a possible interaction of the dansyl moiety with a region on the enzyme molecule which is more hydrophobic relative to the surrounding solvent.

Animals↗
PubMed1983

High-performance liquid chromatography of methotrexate analogs containing terminal lysine or ornithine and their dansyl derivatives.

A procedure utilizing a reverse-phase semipreparative high-performance liquid chromatography column and a binary solvent system consisting of trifluoroacetic acid and 1-propanol has been developed for the semipreparative scale purification and analytical identification of four newly synthesized analogs of methotrexate. The methotrexate analogs containing a lysine or an ornithine residue in place of a terminal glutamate residue together with their respective dansyl derivatives were purified in milligram quantities by the procedures described.

Chromatography, High Pressure Liquid↗
PubMed1982

Lysine and ornithine analogues of methotrexate as inhibitors of dihydrofolate reductase.

The ornithine (6a) and lysine (6b) analogues of methotrexate (1) have been synthesized via condensation of 4-amino-4-deoxy-N10-methylpteroic acid (2) with N gamma-carbobenzoxy-L-ornithine tert-butyl ester (3a) and N epsilon-carbobenzoxy-L-lysine tert-butyl ester (3b), respectively. Removal of the protecting groups gave 5a and 6b. Compounds 6a and 6b and their precursor Cbz acids (5a and 5b) show significant inhibition of dihydrofolate reductase.

Chemical Phenomena↗
PubMed1981

Chemically reactive estrogens: synthesis and estrogen receptor interactions of hexestrol ether derivatives and 4-substituted deoxyhexestrol derivatives bearing alkylating functions.

A series of chemically reactive derivatives of the nonsteroidal estrogen hexestrol have been synthesized as potential affinity labels for the estrogen receptor or as cytotoxic agents with selective activity against receptor-containing cells. These compounds are hexestrol ethers with halo ketone, halohydrin, or epoxide functions or 4-substituted deoxyhexestrols with halo ketone, benzyl halide, nitro, azide, sulfonyl fluoride, or sulfonyl azide groups. The alkylating activity of the electrophilic derivatives was measured using the colorimetric reagent nitrobenzylpyridine, the bromo derivatives being considerably more reactive than the chloro ones. Their reversible binding to the lamb uterine estrogen receptor was measured by competitive binding assays, and their irreversible reaction with receptor was measured by exchange assays that determine the rate and extent of receptor inactivation. In general, monoetherification of hexestrol or substitution of deoxyhexestrol produces compounds with relatively low affinity for the estrogen receptor (0.3-10% that of estradiol). Most of the electrophilic derivatives are rapid and effective inactivators of receptor (24-70% inactivation within 0.5-5 h at 25 degrees C). Of the photosensitive derivatives, 4-azidodeoxyhexestrol appears to be the most efficient receptor inactivator (49%). The high reactivity of these compounds toward the estrogen receptor and the lack of interference by their reaction with other cellular nucleophiles suggest that these compounds may be useful as affinity-labeling agents or as selective cytotoxic agents in intact systems.

Affinity Labels↗
PubMed1980

Allergic contact dermatitis to dimethoxane in a spin finish.

A textile worker exposed to dimethoxane in an aqueous system developed allergic contact dermatitis. Patch testing to this compound and its possible products in an aqueous system demonstrated sensitization to acetaldehyde and crotonaldehyde.

Antifungal Agents↗