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1.
Kazutaka Hirakawa 《Analytical and bioanalytical chemistry》2009,393(3):999-1005
A method for the fluorometry of singlet oxygen (1O2) using less fluorescent folic acid and its analogue, methotrexate (MTX), was examined. Folic acid and MTX were decomposed
into a strongly fluorescent pteridine compound via a photosensitized reaction by 1O2-generating photosensitizers in a deuterium oxide solution. The fluorescence intensity increased in proportion to the irradiation
time or the number of photons absorbed by the photosensitizer. This method using the fluorescence enhancement of these folic
acid analogues can be applied to determine the quantum yield of 1O2 generated through a photosensitized reaction in deuterium oxide. The background fluorescence of MTX is quite smaller than
that of folic acid, indicating that MTX can be used for the more sensitive detection of 1O2.
Figure (DOC 37.0 KB) 相似文献
2.
A chemiluminescence method for the determination of folic acid by the sodium hypochlorite–folic acid–semicarbazide hydrochloride system with a new flow injection technique has been established. The new method can perform simple, sensitive and rapid determinations of folic acid. The response to the concentration of folic acid, in the range of 1.0×10−75.0×10−5 g/ml, is linear. The relative standard deviation of the method is 2.3% (Cs=4.0×10−6 g/ml, n=11). The detection limit is 2.7×10−8 g/ml. This method is suitable for automatic and continuous analysis, and has been successfully tested for the determination of folic acid in a folic acid tablet. 相似文献
3.
《Journal of Saudi Chemical Society》2020,24(1):98-104
A key advantage of amino-modified SiO2 nanoparticles for delivery of phosphorylated nucleosides is a broad possibility for functionalization. It can be modified with ligands currently investigated in targeted drug delivery. To improve the efficacy for intracellular delivery, SiO2 nanoparticles were functionalized with tumor-targeting ligands folic acid, biotin or 5-fluorouracil. Studies of accumulation of these conjugates in HCT116 colon carcinoma cells revealed that the uptake of modified conjugates was significantly bigger compared to unmodified nanoparticles, with the biotinylated conjugate as the preferred compound. The nanocomposites of biotin modified SiO2 and 2′,3′-dideoxyuridine triphosphate showed a pronounced antiproliferative potency relative to the unmodified nanocomposites. Thus, multi-functionalization of SiO2 nanoparticle based conjugates has a major potential for delivery of nucleoside triphosphate analogues, therefore tentatively enhancing their bioactivity. 相似文献
4.
Taft F Harmrolfs K Nickeleit I Heutling A Kiene M Malek N Sasse F Kirschning A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(3):880-886
Access of four new tumor specific folic acid/ansamitocin conjugates is reported that relies on a synthetic strategy based on the combination of mutasynthesis and semisynthesis. Two bromo‐ansamitocin derivatives were prepared by mutasynthesis or by a modified fermentation protocol, respectively, that served as starting point for the semisynthetic introduction of an allyl amine linker under Stille conditions. A sequence of standard coupling steps introduced the pteroic acid/glutamic acid/cysteine unit to the modified ansamitocins. All new derivatives, including those that are expected to be generated after internalization of the folic acid/ansamitocin conjugates into the cancer cell and reductive cleavage of the disulfide linkage showed good to strong antiproliferative activity (IC50 <10 nM ) for different cancer cell lines. Finally, the four conjugates were exposed to two cancer cell lines [cervix carcinoma, KB‐3‐1 (FR+) and lung carcinoma, A‐459 (FR?)], the latter devoid of the membrane‐bound folic acid receptor (FR?). All four conjugates showed strong antiproliferative activity for the FR+ cancer cell line but were inactive against the FR? cell line. The synthetic strategy pursued is based on the combination of mutasynthesis and semisynthesis and proved to be powerful for accessing new ansamitocin derivatives that are difficult to prepare by total synthesis. 相似文献
5.
A new, simplified and unequivocal synthesis of folic acid free of isomers is described. A melt of N(2′)-acetyl-6-formylpterine and dimethyl-N-(p-aminobenzoyl)-L-glutamate was quantitatively converted to 6-azomethin-pterine-ester IV. NaBH4-reduction followed by basic hydrolysis of acetyl and ester groups gives pure folic acid in good yield. 相似文献
6.
Attention has shifted from the treatment of colorectal cancer (CRC) to chemoprevention using aspirin and folic acid as agents capable of preventing the onset of colon cancer. However, no sensitive analytical method exists to simultaneously quantify the two drugs when released from polymer‐based nanoparticles. Thus, a rapid, highly sensitive method of high‐performance liquid chromatography analysis to simultaneously detect low quantities of aspirin (hydrolyzed to salicylic acid, the active moiety) and folic acid released from biodegradable polylactide‐co‐glycolide (PLGA) copolymer nanoparticles was developed. Analysis was done on a reversed‐phase C18 column using a photodiode array detector at wavelengths of 233 nm (salicylic acid) and 277 nm (folic acid). The mobile phase consisted of acetonitrile–0.1% trifluoroacetic acid mixture programmed for a 30 min gradient elution analysis. In the range of 0.1–100 μg/mL, the assay showed good linearity for salicylic acid (R2 = 0.9996) and folic acid (R2 = 0.9998). The method demonstrated good reproducibility, intra‐ and inter‐day precision and accuracy (99.67, 100.1%) and low values of detection (0.03, 0.01 μg/mL) and quantitation (0.1 and 0.05 μg/mL) for salicylic acid and folic acid, respectively. The suitability of the method was demonstrated by simultaneously determining salicylic acid and folic acid released from PLGA nanoparticles. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
7.
Elena V. Dorozhko Nikita A. Lunev Elena I. Korotkova Galina B. Slepchenko Olga I. Lipskikh Ekaterina I. Mikhnevich 《Electroanalysis》2023,35(9):e202300054
In this work two strategies for the synthesis of peroxidase silver conjugates for the qualitative and quantitative determination of immunoglobulins (IgG) to ixodid tick-borne borreliosis (ITBB) (Lyme disease) in human serum were proposed. The first approach for Ab-HRP@AgNP conjugate synthesis involved silver nanoparticles (Ag NPs) capped with a commercial peroxidase conjugate (Ab-HRP) by passive adsorption. The second strategy was based on the initial coupling of Ag NPs with human anti-species antibodies (Ab) by passive adsorption followed by the introduction of horseradish peroxidase (HRP) enzyme into the reaction mixture as a blocking reagent for Ab@AgNP@HRP conjugate synthesis. The formation of peroxidase silver conjugates was proved by UV/Vis spectroscopy and Transmission Electron Microscopy (TEM). The catalytic activity of Ab-HRP@AgNP and Ab@AgNP@HRP conjugates was evaluated by Michaelis-Menten kinetics. A commercially available 96-well microtiter plate with recombinant antigens to ITBB was used as a platform for immobilization of analyzed IgG. The HRP in Ab-HRP@AgNP conjugate was found to retain a sufficient level of activity for interaction with the H2O2 substrate to form an intensely colored reaction product. Therefore Ab-HRP@AgNP conjugate can be used in enzyme-linked immunosorbent assay (ELISA) with spectrophotometric detection of 3,3’,5,5’-Tetramethylbenzidine (TMB Ox) for quantitative determination of IgG to ITBB in human serum in the concentration range 12.5–800 ng ml−1 with LOD 2 ng ml−1. Ab@AgNP@HRP conjugate is recommended for the electrochemical determination of IgG to ITBB in human serum at LOD 3 ng ml−1 with registration of silver oxidation by linear sweep anodic stripping voltammetry (LSASV). Ag NPs in Ab-HRP@AgNP and Ab@AgNP@HRP conjugates do not change electrochemical activity during storage and can be used as an electrochemical label in LSASV method in case of HRP inactivation. The immunoassay based on peroxidase silver conjugates expands the analytical potential for the determination of IgG to ITBB especially during the period of increasing incidence. 相似文献
8.
Srinivas Kothakota Michael J. Dougherty Maurille J. Fournier Thomas L. Mason Eiichiro Yoshikawa David A. Tirrell 《Macromolecular Symposia》1995,98(1):573-583
A general method for the in vivo incorporation of amino acid analogues into artificial proteins is described. The method involves the construction of an artificial gene encoding the sequence of interest (with the corresponding natural amino acid encoded in place of the analogue), transformation of a bacterial host strain that cannot synthesize the natural amino acid, and induction of protein synthesis in a host culture enriched in the analogue. Results are described for the amino acid analogues selenomethionine, p-fluorophenylalanine, trifluoroleucine and 3-thienylalanine. 相似文献
9.
Drishty Satpati Archana Mukherjee Meera Venkatesh Sharmila Banerjee 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(1):89-93
The over-expression of folate receptors in variety of neoplastic tissues makes radiolabeled folate conjugates potential agents
for imaging and therapy of such cancers. With the aim of preparing an imaging agent for targeting folate receptors, folic
acid has been conjugated with homocysteine for complexation with [99mTc(CO)3(H2O)3]+ core. The radiolabeled complex of the homocysteine-folate could be obtained in >95% radiochemical yield as observed by HPLC.
Stability of complex in saline was studied and challenge studies with histidine and cysteine revealed kinetic stability of
the complex. Lipophilicity of the radiolabeled complex (log P) was found to be 0.45. In vitro uptake of 99mTc(CO)3-labeled folic acid derivative was studied in KB cells and inhibition studies were carried out using 3H-folic acid and cold homocysteine–folate conjugate. The in vitro studies indicated loss of binding affinity of the derivative
towards folate receptors. 相似文献
10.
New procedures have been developed for the synthesis of peptide alcohols, such as octreotide conjugates, fragment of gramicidin, and fragment of Trichorzianines in high yield using dihydropyran-2-carboxylic acid as a bifunctional linker to anchor Fmoc-threoninol(But), Fmoc-glycinol, and Fmoc-phenylalaninol onto amine-resins. The linker is stable during peptide elongation as evidenced by a high yield at each coupling step. The octreotide disulfide bonds were formed on-resin by incubating the elongated octreotide/resin with Tl(TFA)3/DMF at 0 °C for 1 hour. Tl(TFA)3/DMF is sufficiently mild that the protecting group and the linker remain intact and allow further the direct coupling of conjugates to octreotide using an autosynthesizer. 相似文献
11.
Johannes Notni Dr. Petr Hermann Dr. Jana Havlíčková Jan Kotek Dr. Vojtěch Kubíček Dr. Jan Plutnar Dr. Natalia Loktionova Patrick Johannes Riss Dr. Frank Rösch Prof. Dr. Ivan Lukeš Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(24):7174-7185
For application in positron emission tomography (PET), PrP9 , a N,N′,N′′‐trisubstituted triazacyclononane with methyl(2‐carboxyethyl)phosphinic acid pendant arms, was developed as 68Ga3+ complexing agent. The synthesis is short and inexpensive. GaIII and FeIII complexes of PrP9 were characterized by single‐crystal X‐ray diffraction. Stepwise protonation constants and thermodynamic stabilities of metal complexes were determined by potentiometry. The GaIII complex possesses a high thermodynamic stability (log K[GaL]=26.24) and a high degree of kinetic inertness. 68Ga labeling of PrP9 is possible at ambient temperature and in a wide pH range, also at pH values as low as 1. This means that for the first time, the neat eluate of a TiO2‐based 68Ge/68Ga generator (typically consisting of 0.1 M HCl) can be directly used for labeling purposes. The rate of 68Ga activity incorporation at pH 3.3 and 20 °C is higher than for the established chelators DOTA and NOTA. Tris‐amides of PrP9 with amino acid esters were synthesized to act as models for multimeric peptide conjugates. These conjugates exhibit radiolabeling properties similar to those of unsubstituted PrP9 . 相似文献
12.
Emanuele F. Pissinati José A. C. Delgado Pedro A. M. Moro Dr. José T. M. Correia Prof. Dr. Roberto G. S. Berlinck Prof. Dr. Márcio W. Paixão 《European journal of organic chemistry》2023,26(21):e202300274
A site-selective carbamoylation strategy to access non-proteinogenic N4-modified asparagines has been described. The protocol is characterized by mild reaction conditions, high functional group compatibility, and a wide diversity of functionalized carbamoyl radicals making possible the access to peptides, pharmaceuticals, and natural N4-asparagine conjugates, as well as enantioenriched unnatural N4-asparagines. Besides that, deuterated analogues were achieved with the insertion of D2O and enantioenriched derivatives could be obtained in 15 min in continuous-flow conditions. 相似文献
13.
A regioselective access to both α- and γ-folic acid conjugates derived from archaeal lipid analogues is described. The synthetic approach is based on conveniently protected glutamates that led first to α- and γ-glutamate derivatives. The final reconstruction of the folic acid moiety was achieved through the reaction of a protected/activated pteroate followed by a simple deprotection step. These α- and γ-folic acid conjugates would permit to establish the importance of a regiocontrolled introduction of folic acid on the folic acid/folate receptor interaction in the case of a targeted drug/gene delivery. 相似文献
14.
Chu Tang Linhui Zhu Jun Li Rui Qin Chang Liu Yu Chen Guangzhong Yang 《Magnetic resonance in chemistry : MRC》2012,50(3):236-241
Five new conjugates of oleanolic acid derivatives and chalcones have been designed and synthesized. The structure elucidation of these conjugates was accomplished by using extensive 1D (1H, 13C) and 2D NMR spectroscopic studies (COSY, HSQC and HMBC); and α‐glucosidase inhibitory activity is reported for these conjugates. Compound 2b (IC50 = 47.5 µm ) displayed much stronger activity than oleanolic acid and acarbose. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
15.
Antonio Clementi Maria Chiara Aversa Carmelo Corsaro Jeroen Spooren Rosanna Stancanelli Christine O??Connor Mary McNamara Antonino Mazzaglia 《Journal of inclusion phenomena and macrocyclic chemistry》2011,69(3-4):321-325
A novel folic acid?C??-cyclodextrin (??-CD) conjugate was synthesized and preliminarily characterized by 1H NMR, ESI-MS, and MALDI-MS. 1H NMR shows the presence of ??- and ??-conjugates which are generated by ??-CD linkage in turn with both carboxylic functions of folic acid. Moreover ROESY evidences supramolecular interactions between the benzene ring of the folic acid and the ??-CD cavity. DOSY suggests that ethylenediamine derived ??-CD?Cfolic acid forms a colloidal dispersion difficult to purify from free folic acid. An analysis of self-diffusion coefficient (Ds) of the three species (??-, ??-conjugates, and free folic acid) and relaxation times (T1 and T2) is reported to tentatively explain the colloidal behaviour of the new species in an aqueous solution. 相似文献
16.
Buzhe Xu Yann Hermant Dr. Sung-Hyun Yang Prof. Dr. Paul W. R. Harris Prof. Dr. Margaret A. Brimble 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(62):14101-14107
A de novo solid-phase synthesis of the cyclic lipodepsipeptide daptomycin via Boc chemistry was achieved. The challenging ester bond formation between the nonproteinogenic amino acid kynurenine was achieved by esterification of a threonine residue with a protected tryptophan. Subsequent late-stage on-resin ozonolysis, inspired by the biomimetic pathway, afforded the kynurenine residue directly. Synthetic daptomycin possessed potent antimicrobial activity (MIC100=1.0 μg mL−1) against S. aureus, while five other daptomycin analogues containing (2R,3R)-3-methylglutamic acid, (2S,4S)-4-methylglutamic acid or canonical glutamic acid at position twelve prepared using this new methodology were all inactive, clearly establishing that the (2S,3R)-3-methylglutamic acid plays a key role in the antimicrobial activity of daptomycin. 相似文献
17.
Hirotada Iida Keishiro Hayashida Mitsuaki Yamada Kazumasa Takahashi Kazutoshi Yamada 《合成通讯》2013,43(3):225-230
The general synthetic method of pyrazines1 has been established. The method for synthesizing symmetrically substituted pyrazine derivatives, however, has not been well-studied.2 Especially for synthesis of the title pyrazines, it is only described in a few words by Adkins3 and co-workers that ethyl 2-aminoacetoacetate employed in process to preparing of the threonine synthesis is spontaneously autoxidized to give 2,5-dimethyl-3,6-dicarbetoxy pyrazine as a byproduct. On the basis of this finding of Adkins, we have established a convenient method for the synthesis of 2,5-di-methylpyrazine-3,6-dicarboxylic acid derivatives (D1–5) using the corresponding acetoacetic acid derivatives (A1–4) as the starting materials (Scheme). 相似文献
18.
Matthias Hoffmann Fred Burkhart Gerhard Hessler Horst Kessler 《Helvetica chimica acta》1996,79(6):1519-1532
The synthesis of C-glycosidic analogues 15–22 of N4-(2-acetamido-2-deoxy-β-D -glucopyranosyl)-L -asparagine (Asn(N4GlcNAc)) possessing a reversed amide bond as an isosteric replacement of the N-glycosidic linkage is presented. The peptide cyclo(-D -Pro-Phe-Ala-CGaa-Phe-Phe-) (CGaa = C-glycosylated amino acid; 24 ) was prepared to demonstrate that 3-[(3-acetamido-2,6-anhydro-4,5,7-tri-O-benzyl-3-deoxy-β-D -glycero-D -guloheptonoyl)amino]-2-[(9H-fluoren-9-yloxycarbonyl)amino]propanoic acid ( 22 ) can be used in solid-phase peptide synthesis. The conformation of 24 was determined by NMR and molecular-dynamics (MD) techniques. Evidence is provided that the CGaa side chain interacts with the peptide backbone. The different C-glycosylated amino acids 15–21 were prepared by coupling 3-acetamido-2,6-anhydro-4,5,7-tri-O-benzyl-3-deoxy-β-D -glycero-D -gulo-heptonic acid ( 4 ) with diamino-acid derivatives 8–14 in 83–96% yield. The synthesis of 4 was performed from 2-(acetamido-3,4,6-tri-O-benzyl-2-deoxy-β-D -glucopyranosyl) tributylstannane ( 2 ) by treatment with BuLi and CO2 in 83% yield. Similarly, propyl isocyanat yielded the glycoheptonamide 7 in 52% from 2 . Compound 2 was obtained from 2-acetamido-3,4,6-tri-O-benzyl-2-deoxy-D -glucopyranose ( 1 ) by chlorination and addition of tributyltinlithium in 74% yield. A procedure for a multigram-scale synthesis of 1 is given. 相似文献
19.
There is considerable interest in the development of novel and more efficient delivery systems for improving the efficacy of photodynamic therapy (PDT). The authors in this highlighted issue describe the synthesis and the photobiological characterizations of two photosensitizer (PS) conjugates based on β‐carboline derivatives covalently conjugated to folic acid (FA) coupled to bovine serum albumin (BSA) as a carrier system specifically targeting cancer cells overexpressing FA receptor alpha (FRα). Accordingly, only the FA–BSA–β‐carboline conjugates are internalized specifically in FRα‐positive cells and are proved to be phototoxic. On the other hand, albumin–β‐carboline conjugates without FA or β‐carboline derivatives alone are not internalized and nontoxic. This conjugate is among the first to produce a conjugate composed of a PS and FA molecules that are directly conjugated to BSA. In addition, the in vitro studies are the first evidence that directly conjugated FA‐BSA can be used as carriers to selectively enhance cytotoxicity by PDT relative to unmodified PS or nontargeted BSA‐PS. This strategy is a positive step forward for the covalent design and construction of a photodynamic nanomedicine for FR‐positive tumors. 相似文献
20.
Chemoenzymatic Syntheses of Sialylated Oligosaccharides Containing C5‐Modified Neuraminic Acids for Dual Inhibition of Hemagglutinins and Neuraminidases
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Dr. Lémonia Birikaki Stéphanie Pradeau Dr. Sylvie Armand Dr. Bernard Priem Luis Márquez‐Domínguez Dr. Julio Reyes‐Leyva Dr. Gerardo Santos‐López Dr. Eric Samain Dr. Hugues Driguez Dr. Sébastien Fort 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10903-10912
A fast chemoenzymatic synthesis of sialylated oligosaccharides containing C5‐modified neuraminic acids is reported. Analogues of GM3 and GM2 ganglioside saccharidic portions where the acetyl group of NeuNAc has been replaced by a phenylacetyl (PhAc) or a propanoyl (Prop) moiety have been efficiently prepared with metabolically engineered E. coli bacteria. GM3 analogues were either obtained by chemoselective modification of biosynthetic N‐acetyl‐sialyllactoside (GM3NAc) or by direct bacterial synthesis using C5‐modified neuraminic acid precursors. The latter strategy proved to be very versatile as it led to an efficient synthesis of GM2 analogues. These glycomimetics were assessed against hemagglutinins and sialidases. In particular, the GM3NPhAc displayed a binding affinity for Maackia amurensis agglutinin (MAA) similar to that of GM3NAc, while being resistant to hydrolysis by Vibrio cholerae (VC) neuraminidase. A preliminary study with influenza viruses also confirmed a selective inhibition of N1 neuraminidase by GM3NPhAc, suggesting potential developments for the detection of flu viruses and for fighting them. 相似文献