It has been proposed that photodegradation of folates may be the reason for the pigmentation of races living under high fluence rates of ultraviolet radiation. The photodegradation of folic acid (FA) induced by ultraviolet-A (UV-A) radiation, in solution and in the presence of human serum albumin (HSA), was studied with absorption and fluorescence spectroscopy. FA photodegradation, with formation of p-aminobenzoyl-l-glutamic acid, 6-formylpterin and pterin-6-carboxylic acid, was found to follow an exponential trend. A scheme of FA photodegradation, which involves photosensitization of FA degradation by its photoproducts, was proposed. The rate of FA photodegradation decreased drastically in the presence of HSA, whereas the spectral characteristics of the photoproducts remained constant. The reduction of the FA photodegradation rate by HSA was accompanied by degradation of tryptophan in HSA. Tryptophan, when added to solutions of FA, had a similar effect as HSA. In solutions of FA and HSA the FA photoproducts cause photodamage mainly to HSA rather than to FA itself. The oxygen dependence of FA photodegradation and the inhibition of this process by sodium azide indicate that singlet oxygen may participate in the photosensitizing activity of FA photoproducts. 相似文献
The methylation of folic acid (2) with excess methyl iodide resulted in the formation of dimethyl 1,3-dimethylfolate ( 4 ), whereas, methylation of dimethyl folate ( 3 ) with an equimolar amount of methyl iodide gave mainly dimethyl 3-methylfolate ( 6 ). Both 4 and 6 underwent the Dimroth rearrangement in base to give the corresponding 2-deamino-2-methyiamino folic acids 5 and 7, respectively. Amination of 2 with hydroxylamine-O-sulfonic acid in dilute base gave a low yield of 3-amino folic acid (8), which underwent Dimroth rearrangement to give 2-deamino-2-hydrazino folic acid (9) in an acidic, but not a basic, medium. 相似文献
One of the most promising strategies in anticancer therapies is the targeted delivery through malignancy-associated cellular markers. The design of new synthetic devices with enhanced stimuli-responsive sensitivity and targeting ligands is a promising field for the development of cancer-specific delivery systems. One of the pathways to achieve this aim is the chemical functionalization of nanodevices such as microgels. The p-nitrophenyl acrylate (NPA) is an active ester molecule with a group that can be easily cleavaged by the nucleophilic attack of species such as amines. This modification consists of an easy chemical reaction that leads to several types of functionalized microgels, which are originally made up of NPA as one of their constituent monomers.
Here is reported the chemical functionalization of NPA-based microgels by incorporating pH-sensitive functional groups and folic acid as a tumor targeting ligand into the same initial polymer network. For this purpose, microgels of p-nitrophenyl acrylate (NPA)-co-methacrylamide (MeAM) synthesized by precipitation polymerization, were modified with two different pyridine derivatives: 2-aminomethylpyridine (2-AMP) and 2-aminopyridine (2-AP), thus pH-sensitive microgels with acid pH swelling capacity were obtained. The equilibrium swelling behaviour was studied as a function of pH, ionic strength, copolymer composition and type of pyridine derivative. In addition, the microgels were derivatized with ethylene diamine, to obtain amino-functionalized microgels to which the folic acid was subsequently attached as the targeting ligand. As final step, pH-sensitive groups and folic acid were equimolarly attached to the polymer chains to obtain the fully functionalized microgels. 相似文献
Journal of Solid State Electrochemistry - UV/Vis absorption spectroelectrochemistry is a very promising analytical technique due to the complementary information that is simultaneously obtained... 相似文献
The preparation of isonipecotinoyl analogues of aminopterin and methotrexate is described. Condensation of diethyl N-isonipecotinoyl-L-glutamate 4 with 2-amino-5-bromomethyl-3-cyanopyrazine 5 afforded diethyl N-(N-[(2-amino-3-cyanopyrazin-5-yl)methyl]isonipecotinoyl)-L-glutamate 6 . Cyclisation of 6 with guanidine followed by blocking group hydrolysis afforded N-([N-(2,4-diaminopteridin-6-yl)methyl]isonipecotinoyl)-L-glutamic acid 8 . Coupling of N-(2-amino-4(3H)ioxopteridin-6-yl]methyl)isonipecotinic acid 11 with diethyl L-glutamate gave diethyl N-[(N-[2-amino-4(3H)-oxopteridin-6-yl]methyl)isonipecotinoyl]-L-glutamate 12 . Blocking group hydrolysis afforded N-[(N-[2-amino-4(3H)-oxopteridin-6-yl]methyl)isonipecotinoyl]-L-glutamic acid 13 . 相似文献
We report on a novel luminescent method for the detection of folic acid (FA), a member of the vitamin B family. Y2O3 nanoparticles were doped with europium(III) ions and surface-modified with captopril. Their fluorescence is quenched by FA, and intensity is a function of folic acid concentration in the 0.1 – 40 μM concentration range. The detection limit is 83 nM of FA at pH 7 and room temperature.
Figure
In this work, we propose a novel method based on the changes in the fluorescence intensity of nanoparticles. Modified Eu-doped Y2O3 nanoparticles by captopril have been used as a probe for the detection of folic acid. 相似文献
The reduction of nitroblue tetrazolium (NBT) to formazan by folic acid, N-(4-aminobenzoyl) glutamic acid, and other amino acids was studied in this paper. The reduction involves only one of the two tetrazolium rings of NBT. The reaction is considerably more rapid with folic acid and N-(4-aminobenzoyl) glutamic acid than with the other amino acids under study. The electron donor moiety appears to be the carboxylic acid in the alpha position. N-ethyl-N′(3-dimethylaminopropyl) carbodiimide notably increases the rate of the reaction and promotes the reduction of both tetrazolium rings. 相似文献
Hydrogen peroxide (H2O2) is one of the most important reactive oxygen species. In the present study, a fluorometry method for detecting H2O2 utilizing folic acid was evaluated. Folic acid was decomposed by H2O2 in the presence of Cu(II) into pterine-6-carboxylic acid, leading to strong fluorescence enhancement. In the absence of the
metal ion, superoxide and H2O2 could not decompose folic acid. Also, H2O2 plus sodium hypochlorite (a source of singlet oxygen) could not induce fluorescence enhancement. These results demonstrate
that H2O2 can be selectively detected using folic acid plus Cu(II). The limit of detection (LOD; at S/N=3) for H2O2 is 0.5 μM. This method based on the fluorescence enhancement of folic acid was applied in order to determine small amounts
of H2O2 generated through the autooxidation of semicarbazide (generation rate: ∼0.01 μM min−1), a carcinogenic compound.
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15N-Chemical shifts of a series of 5, 6, 7, 8-tetrahydropterins, 7, 8-dihydropterins and pterins have been measured in acidic solution by means of a probe for 20 mm sample tubes. Included are the relevant data of folic acid (11) , 5, 6, 7, 8-tetrahydrofolic acid (5) and N (5, 10)-metheno-5, 6, 7, 8-tetrahydrofolic acid (6) . The different oxidation states are clearly relected in the chemical shifts of N (5) and N (8). Assignment of the nitrogen resonances was achieved by protonation effects (discrimination between N (1) and N (3)) and with the aid of alkyl substitution at C (6) and C(7), to distinguish between N (5) and N (8). 相似文献