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1.
The association of quantum dots (QDs) to carbohydrate-binding proteins – lectins – has revealed novel biotechnological strategies for glycobiology studies. Herein, carboxyl-coated QDs were conjugated by adsorption to Cramoll, a glucose/mannose lectin obtained from Cratylia mollis seeds. Then, the conjugates were optically characterized and used to evaluate the surface carbohydrate profiles of four Aeromonas species isolated from the tambaqui fish (Colossoma macropomum). All the Aeromonas cells were labeled by the conjugate. Inhibition assays with methyl-α-D-mannopyranoside and mannan were performed to confirm the labeling specificity. Cramoll-QDs conjugates presented high brightness and showed similar absorption and emission profiles compared to bare QDs. According to the labeling pattern of Aeromonas spp. by the conjugate, results suggested that A. jandaei and A. dhakensis strains may harbor a higher content of more complex glucose/mannose surface glycans, with more available sites for Cramoll-QDs interaction, than A. hydrophila and A. caviae. Noteworthy, the Cramoll-QDs conjugates demonstrated to be potential tools for bacterial characterization based on superficial carbohydrate detection.  相似文献   

2.
The efficiency of the chemotherapeutic agent methotrexate (MTX) in cancer treatment is limited by the frequent development of the drug resistance of tumor cells. We had previously shown in vitro using human acute leukemia cells with various sensitivity to MTX (T-lymphoblastic CCRF-CEM line and resistant CEM/MTX subline) that MTX incorporation into liposomes in the form of a lipophilic prodrug, diglyceride conjugate (MTX-DG), allows for the overcoming of cell resistance due to the impaired active transmembrane transport. In this work, we have studied the profile of binding with carbohydrates of the cell lines mentioned using carbohydrate fluorescent probes (poly(acryl amide) conjugates). Lipophilic conjugates of tetrasaccharide SiaLeX, 6′-HSO3LacNAc, and also inactive pentaol for incorporation into liposomes, have been synthesized. The cytotoxicity of MTX-DG liposomes equipped with the SiaLeX ligand toward the sensitive CCRF-CEM cell culture was demonstrated to be 3.5 times higher than that of MTX-DG liposomes bearing the control inactive pentaol. The activity of MTX liposomes bearing 6′-HSO3LacNAc toward resistant CEM/MTX was 1.6-fold increased. The use of carbohydrate ligands as molecular addresses for drug-carrying liposomes as a potential method of treating heterogeneous tumor tissue is discussed.  相似文献   

3.
The anti-MUC1 antibody, CTM01, has been chosen to target the potently cytotoxic calicheamicin antitumor antibiotics to solid tumors of epithelial origin that express this antigen. Earlier calicheamicin conjugates relied on the attachment of a hydrazide derivative to the oxidized carbohydrates that occur naturally on antibodies. This produced a "carbohydrate conjugate" capable of releasing active drug by hydrolysis in the lysosomes where the pH is low. Conjugates have now been made that are formed by reacting a calicheamicin derivative containing an activated ester with the lysines of antibodies. This gives an "amide conjugate" that is stable to hydrolysis, leaving the disulfide that is present in all calicheamicin conjugates as the only likely site of drug release from the conjugate. As previously shown for the carbohydrate conjugate, this amide conjugate of CTM01 produces complete regressions of xenograft tumors at doses of 300 microg/kg (calicheamicin equivalents) given three times. This indicates that hydrolytic drug release is not necessary for potent, selective cytotoxicity for calicheamicin conjugates of CTM01. Although the unconjugated calicheamicins are in general less active in cells expressing the multidrug resistance phenotype, both in vitro and in vivo results of studies reported here suggest that the efficacy of the calicheamicins toward such tumors is unexpectedly enhanced by antibody conjugation, especially for the "amide conjugate". These hydrolytically stable conjugates are also active toward cisplatin-resistant ovarian carcinoma cells as well. Such studies indicate that the calicheamicin amide conjugate of CTM01 may have potential for the treatment of MUC1-positive solid tumors, including some types of resistant tumors.  相似文献   

4.
A series of melphalan-O-carboxymethyl chitosan (Mel-OCM-chitosan) conjugates with different spacers were prepared and structurally characterized. All conjugates showed satisfactory water-solubility (160-217 times of Mel solubility). In vitro drug release behaviors by both chemical and enzymatic hydrolysis were investigated. The prodrugs released Mel rapidly within papain and lysosomal enzymes of about 40–75%, while released only about 4–5% in buffer and plasma, which suggested that the conjugates have good plasma stability and the hydrolysis in both papain and lysosomes occurs mostly via enzymolysis. It was found that the spacers have important effect on the drug content, water solubility, drug release properties and cytotoxicity of Mel-OCM-chitosan conjugates. Cytotoxicity studies by MTT assay demonstrated that these conjugates had 52–70% of cytotoxicity against RPMI8226 cells in vitro as compared with free Mel, indicating the conjugates did not lose anti-cancer activity of Mel. Overall these studies indicated Mel-OCM-chitosan conjugates as potential prodrugs for cancer treatment.  相似文献   

5.
Daunomycin has been attached to various structurally related synthetic branched polypeptides with a polylysine backbone, using its acid-labile cis-aconityl derivative (cAD). Due to the importance of the side-chain structure in alpha-helix formation and immunological and pharmacological properties of branched polypeptides, we have investigated the conformation, biodistribution, and in vitro cytotoxicity of cAD-carrier conjugates with polypeptides containing amino acid residues of different identity and/or configuration at the side-chain end (XAK type) or at the position next to the polylysine backbone (AXK type), where X = Leu, D-Leu, Pro, Glu, or D-Glu. According to CD studies, polycationic conjugates with hydrophobic Leu in the side chains could assume a highly ordered conformation, while amphoteric conjugates containing Glu proved to be unordered in PBS. The reduction of in vitro cytotoxic activity of cAD by conjugation to carriers and the biodistribution profile of the conjugates were found to be dependent predominantly on the charge properties and on the side-chain sequence of the carrier polypeptide. It was demonstrated that by proper combination of structural elements of the carrier molecule, it is feasible to construct a cAD-branched polypeptide conjugate with significantly prolonged blood survival and with no reduction in in vitro cytotoxicity of the drug.  相似文献   

6.
The influence of sodium metaperiodate concentration on kinetics and conversion degree of peroxidase carbohydrate moiety as well as the effect of the oxidation degree of the carbohydrate moiety on the composition, structure and properties of insulin-peroxidase conjugates were studied. The initial rate of peroxidase's oxidation is directly proportional to the periodate concentration; the oxidation rate constant of peroxidase carbohydrate moiety is 1.23 x 10(-3) M-1 min-1. At the molar ratio of metaperiodate to peroxidase 150:1 or higher, the maximal quantity of aldehyde groups (62 +/- 2) in the peroxidase molecule is formed and the oxidation of each carbohydrate chain leads to the formation of eight aldehyde groups. The molecular mass composition of the insulin-peroxidase conjugates was studied by HPLC. The conjugates proved to be multicomponent mixtures of oligomers (53, 83, 128, 174, 268, 440 kD and higher). The insulin-peroxidase molar ratio in the fractions of the conjugates with molecular masses higher than 83 kD is 8:1. It was shown that the affinity of insulin-peroxidase conjugates to antibodies depends on the oxidation degree of peroxidase used for production of conjugates.  相似文献   

7.
 本研究采用间接连接法,应用异型双功能连接剂SPDP,形成以酰胺键和二硫键连接的氮甲喋吟-人血清白蛋白-单抗79(MTX-HSA-McAb79)结合物。其中McAb79与HSA克分子比有效地控制在1:1~2,且结合物的纯度及产率均较高,有一定的制备价值。 对靶细胞Nalm-6的体外细胞毒试验结果表明:MTX-HSA-McAb 79的杀伤活性显著强于MTX-HSA-nIgG,但较游离MTX的杀伤活性为弱。且MTX-HSA-McAb 79的杀伤作用依赖于McAb 79与靶抗原CALLA的抗原抗体反应。  相似文献   

8.
A soluble isolated wheat protein fraction (sIWP) prepared from isolated wheat protein (30–35% deamidation) was incubated alone or in the presence of glucose or maltodextrins of various molecular weights (MW 1, 1.9 and 4.3 kDa) at 60 °C and 75% relative humidity to promote the formation of Maillard conjugates. The formation of Maillard conjugates was confirmed by the loss of available -NH2 groups on incubation. Approximately 3–4 carbohydrate moieties (glucose or low molecular weight carbohydrates in the commercial maltodextrin) were attached per mole of sIWP after 24 h incubation. Principal component analysis of attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra measured in the dry state showed that there were no major structural changes among non-incubated sIWP, sIWP incubated alone, sIWP–glucose conjugate and sIWP–maltodextrin (MW 1 kDa) conjugate. Structural changes were observed when the protein was incubated with larger molecular weight maltodextrin (MW 1.9 kDa or 4.3 kDa). However, there were no detectable differences in their circular dichroism (CD) spectra suggesting the absence of conformational changes in proteins with or without attached carbohydrates in solution state. The differences between the FTIR and CD results are possibly due to differences in water content of the samples although pressure-induced changes to protein structure induced in the ATR cell and the influence of unreacted maltodextrins cannot be discounted. Attachment of low molecular weight carbohydrate moieties on a relatively large molecular weight protein (i.e. sIWP with average MW of 40.4 kDa) with low lysine content (average three per mole of protein) is not sufficient to have an impact on the secondary structure of the protein.  相似文献   

9.
The anti-CD33 antibody, P67.6, has been chosen to target the potently cytotoxic calicheamicin antitumor antibiotics to acute myeloid leukemia (AML) due to the presence of CD33 on >80% of patient samples and its lack of expression outside the myeloid cell lineages, especially its lack of expression on pluripotent stem cells. Previous calicheamicin conjugates relied on the attachment of a hydrazide derivative to the oxidized carbohydrates that occur naturally on antibodies. This results in a "carbohydrate conjugate" capable of releasing active drug by hydrolysis of a hydrazone bond in the lysozomes where the pH is low. Conjugates have now been made that are formed by reacting a calicheamicin derivative containing an activated ester with the lysines of antibodies. This results in an "amide conjugate" that is stable to hydrolysis, leaving the disulfide that is present in all calicheamicin conjugates as the likely site of drug release from the conjugate. In this article, these two classes of calicheamicin-antibody conjugates are compared for potential use in AML with the anti-CD33 antibody P67.6. Conjugates of P67.6 are shown to require the site of hydrolytic release afforded by the carbohydrate conjugates in order to retain good potency and selectivity in vitro, in vivo, and ex vivo. The P67.6 carbohydrate conjugate of calicheamicin is selectively cytotoxic at <0.006 ng/mL of calicheamicin equivalents (cal equiv) toward HL-60 promyelocytic leukemia cells in tissue culture. Long-term, tumor-free survivors are seen in xenograft models when mice bearing HL-60 subcutaneous tumors are treated with the P67.6 carbohydrate conjugate at a dose of 300 microg/kg cal equiv given three times. This conjugate also selectively inhibits the formation of colonies from AML marrow samples at 2 ng/mL cal equiv. The P67.6 carbohydrate conjugate of calicheamicin therefore appears to have promise as an antibody-targeted chemotherapeutic agent for CD33-positive diseases such as AML.  相似文献   

10.
Colon-specific azo based polyphosphazene–anticancer drug conjugates (1118) have been synthesized and evaluated by ex-vivo release studies. The prepared polyphosphazene drug conjugates (1118) are stable in acidic (pH = 1.2) buffer which showed that these polymer drug conjugates are protected from acidic environment which is the primary requirement of colon specific targeted drug delivery. The ex-vivo release profiles of polyphosphazene drug conjugates (1118) have been performed in the presence as well as in the absence of rat cecal content. The results showed that more than 89% of parent drugs (methotrexate and gemcitabine) are released from polymeric backbone of polyphosphazene drug conjugates (14 and 18) having n-butanol (lipophilic moiety). The in-vitro cytotoxicity assay has also been performed which clearly indicated that these polymeric drug conjugates are active against human colorectal cancer cell lines (HT-29 and COLO 320 DM). The drug release kinetic study demonstrated that Higuchi’s equation is found to be best fitted equation which showed that release of drug from polymeric backbone as square root of time dependent process based on non-fickian diffusion. Therefore, the synthesized polyphosphazene azo based drug conjugates of methotrexate and gemcitabine are the potential candidates for colon targeted drug delivery system with minimal undesirable side effects.  相似文献   

11.
Neoglycoconjugates containing 4, 8, 32, and 64 terminal residues of B-disaccharide (BDI) or N-acetylneuraminic acid (Neu5Ac) attached to poly(aminoamide)-type dendrimers (PAMAMs) were synthesized. The ability of BDI conjugates to bind natural xenoantibodies (anti-BDI antibodies) and the ability of Neu5Ac conjugates to inhibit the hemagglutinin-mediated adhesion of influenza virus were studied. The biological activity of PAMAM conjugates turned out to be higher than that of free carbohydrate ligands, but less than that of multivalent glycoconjugates based on other types of synthetic polymeric carriers. A conformational analysis of PAMAM matrices and resulting conjugates was performed to determine the statistical distances between carbohydrate ligands. The computations revealed the tendency of the PAMAM chains toward compaction and formation of dense globules. The process results in a decrease in the distances between the carbohydrate ligands in the conjugates and, hence, could affect the ability of glycoconjugates to efficiently bind the polyvalent carbohydrate-recognizing proteins.  相似文献   

12.
INTRODUCTION: Nutrition therapy is an integral part of the management of gestational diabetes mellitus (GDM). Most women with GDM are treated by nutritional management alone. The goal of our study was to compare low and high carbohydrate diets in their effectiveness, safety and tolerability in women with GDM. MATERIAL AND METHODS: The study group consisted of 30 Caucasian women newly diagnosed with GDM, with a mean age of 28.7 +/- 3.7 years and pregnancy duration of 29.2 +/- 5.4 weeks. The patients were randomised into two groups: those on a low and those on a high carbohydrate diet (45% vs. 65% respectively of energy supply coming from carbohydrates). The presence of urine ketones was controlled every day. After two weeks daily glucose profiles and compliance with the recommended diets were analysed. RESULTS: Glucose concentration before implementation of the diet regimen did not differ between groups. No changes in fasting blood glucose were noticed in the group that had followed a low carbohydrate diet, although a significant decrease in glucose concentration was observed after breakfast (102 +/- 16 vs. 94 +/- 11 mg/dl), lunch (105 +/- 12 vs. 99 +/- 9 mg/dl) and dinner (112 +/- 16 vs. 103 +/- 13 mg/dl) (p < 0.05). In the high carbohydrate diet group fasting and after-breakfast glucose concentration did not change. A significant decrease in glycaemia was noticed after lunch (106 +/- 15 vs. 96 +/- 7 mg/dl) and dinner (107 +/- 12 vs. 97 +/- 7 mg/dl) (p < 0.05). Ketonuria was not observed in either group. Obstetrical outcomes did not differ between groups. CONCLUSIONS: Both high and low carbohydrate diets are effective and safe. A diet with carbohydrate limitation should be recommended to women who experience the highest glycaemia levels after breakfast.  相似文献   

13.
The production and characterization of covalent amyloglucosidase-antibody conjugates using anti-human serum albumin immunoglobulin G are described. The conjugation procedure is based on the periodate oxidation of carbohydrate moieties that are covalently linked to the enzyme, followed by Schiff's base formation with amino residues on IgG. An ultrasensitive enzyme cycling assay for glucose, the product of maltose cleavage by amyloglucosidase, was developed in order to increase the sensitivity of detecting the enzyme-antibody conjugate. The cycling assay, which allows the accurate measurement of glucose in the picomole range, involves an enzymatic conversion of glucose to glucose-6-phosphate and then isomerization to fructose-6-phosphate. A futile cycle between fructose-6-phosphate and fructose-1,6-diphosphate results in accumulation of adenosine diphosphate at a rate proportional to the original glucose concentration. The rate was monitored by a spectrophotometric system involving pyruvate kinase, phospho(enol)pyruvate, lactate dehydrogenase, and diphosphopyridine nucleotide.  相似文献   

14.
Summary The use of conjugates of microbial iron chelators (siderophores) and antibiotics for illicit transport of antibiotics into cells is a potentially powerful method for the rational design of therapeutic agents. The structural complexity of most natural siderophores has impeded progress in this area. Described here are the design, syntheses and preliminary biological studies of several siderophore--lactam antibiotic conjugates. Both hydroxamic-acid-based and catechol-based conjugates with and without amino acid spacers to carbacephalosporins were synthesized and demonstrated to be effective inhibitors ofEscherichia coli X580. Mutant selection was noted for each class of conjugates. Mutants selected from exposure of theE. coli to the hydroxamate conjugates were susceptible to the catechol conjugates and vice versa. Combinations of hydroxamate-and catechol-carbacephalosporin conjugates were most effective inhibitors ofE. coli X580.  相似文献   

15.
Stable and lectin-recognizable DNA-carbohydrate conjugates were prepared by diazo coupling of lactose and cellobiose derivatives to fragmented salmon testes DNA. The diazo coupling is suggested to take place selectively to guanine bases since the amount of lactose moiety introduced was directly proportional to the G content of various DNAs with different G contents. According to the CD spectra, the conjugates bearing carbohydrate less than 25% content kept a typical B-type conformation similar to native DNA. The conjugates possessed higher melting temperature and stronger nuclease resistance both to exo- and endonucleases than native DNA. Gel shift assay and fluorescence binding assay showed that the DNA-lactose conjugates were specifically bound to galactose-specific lectin RCA(120) with strong binding affinity (Ka = 10(4)-10(5) M(-1)) due to glycoside cluster effect. This facile method will be a useful protocol of molecular design for cell-targeted gene therapy.  相似文献   

16.
The concepts of rational design and solid phase combinatorial chemistry were used to develop affinity adsorbents for glycoproteins. A detailed assessment of protein–carbohydrate interactions was used to identify key residues that determine monosaccharide specificity, which were subsequently exploited as the basis for the synthesis of a library of glycoprotein binding ligands. The ligands were synthesised using solid phase combinatorial chemistry and were assessed for their sugar‐binding ability with the glycoenzymes, glucose oxidase and RNase B. Partial and completely deglycosylated enzymes were used as controls. The triazine‐based ligand, histamine/tryptamine (8/10) was identified as a putative glycoprotein binding ligand, since it displayed particular affinity for glucose oxidase and other mannosylated glycoproteins. Experiments with deglycosylated control proteins, specific eluants and retardation in the presence of competing sugars strongly suggest that the ligand binds the carbohydrate moiety of glucose oxidase rather than the protein itself. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

17.
Studies of the biological chemistry of most anticancer drugs have revealed their cytotoxicity is expressed after the drugs have entered cells. It is thought that anthracycline antitumor drugs exert their cytotoxicity by entering cells, diffusing into nuclei, and inhibiting topoisomerase II and/or intercalating DNA base pairs. In order to deliver anthracyclines to transferrin (TRF) receptors on the plasma membranes of human tumor cells, we have prepared conjugates of adriamycin (ADR) with human TRF. These TRF-ADR conjugates were found to be stable at low pH and to exert more efficient cytotoxicity than free drug. By using spectrofluorometry, we found that the fluorescence of ADR within the conjugate was quenched by native DNA, demonstrating the presence of conformationally available drug to intercalate with nuclear DNA. However, fluorescence was not quenched when conjugate was reacted with viable cells, indicating that ADR did not reach the nucleus. Results of fluorescence microscopy experiments confirmed that free but not conjugated ADR reached the nuclei of viable cells, and TRF-ADR conjugates labeled with fluorescein isothiocyanate were found to initiate lateral diffusion as determined by patch and cap reactions. The involvement of TRF receptors was shown by flow cytometry experiments in which native TRF inhibited binding of fluorescein-labeled TRF-ADR conjugates. These data suggest that TRF-ADR conjugates mediate cytotoxicity by a mechanism other than intercalation with nuclear DNA. This mechanism, revealed by conjugating ADR to a TRF carrier, may not initiate complications such as cardiotoxicity and drug resistance.  相似文献   

18.
A series of methoxy poly(ethylene glycol)-succinyl-5'-O-zidovudine conjugates (mPEG-succinyl-AZT) with different molecular weight (M(w): 750 Da, 2, 5 or 10 kDa) of mPEG were synthesized and characterized by Fourier transform infrared (FTIR) spectroscopy, (1)H nuclear magnetic resonance ((1)H NMR) spectroscopy, and matrix-assisted laser desorption/ionization time of flight mass (MALDI TOF MS) spectrometry analysis. All conjugates showed good stability in vitro release experiments, and good anti-HIV activity and low cytotoxicity in MT-4 cells, in which, mPEG(750)-succinyl-AZT exhibited good inhibition to wild-type viruses (strains IIIB and ROD) with EC(50) values of 0.11 and 0.090 μmol/L, respectively, and it showed no cytotoxicity up to 110 μmol/L. Oral pharmacokinetic study in rats showed the half-life time (T(1/2)) of all conjugates are prolonged compared to free AZT. Especially, mPEG(750)-succinyl-AZT displayed a ~2.3-fold prolonged half-life and approximately 224% increased bioavailability of AZT.  相似文献   

19.
Neoglycoconjugates containing 4, 8, 16, 32, and 64 terminal residues of B-disaccharide (BDI) or N-acetylneuraminic acid (Neu5Ac) attached to poly(aminoamide)-type dendrimers (PAMAMs) were synthesized. The ability of BDI conjugates to bind natural xenoantibodies (anti-BDI antibodies) and the ability of Neu5Ac conjugates to inhibit the hemagglutinin-mediated adhesion of influenza virus were studied. The biological activity of PAMAM conjugates turned out to be higher than that of free carbohydrate ligands, but less than that of multivalent glycoconjugates based on other types of synthetic polymeric carriers. A conformational analysis of PAMAM matrices and resulting conjugates was performed to determine the statistical distances between carbohydrate ligands. The computations revealed the tendency of the PAMAM chains toward compaction and formation of dense globules. The process results in a decrease in the distances between the carbohydrate ligands in the conjugates and, hence, could affect the ability of glycoconjugates to efficiently bind the polyvalent carbohydrate-recognizing proteins. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2002, vol. 28, no. 6; see also http://www.maik.ru.  相似文献   

20.
Malignant neoplasms exhibit an elevated rate of glycolysis over normal cells. To target the Warburg effect, we designed a new series of 2-deoxyglucose (2-DG) conjugated platinum (II) complexes for glucose transporter 1 (GLUT1)-mediated anticancer drug delivery. The potential GLUT1 transportability of the complexes was investigated through a comparative molecular docking analysis utilizing the latest GLUT1 protein crystal structure. The key binding site for 2-DG as GLUT1’s substrate was identified with molecular dynamics simulation, and the docking study demonstrated that the 2-DG conjugated platinum (II) complexes can be recognized by the same binding site as potential GLUT1 substrate. The conjugates were synthesized and evaluated for in vitro cytotoxicity study with seven human cancer cell lines. The results of this study revealed that 2-DG conjugated platinum (II) complexes are GLUT1 transportable substrates and exhibit improved cytotoxicities in cancer cell lines that over express GLUT1 when compared to the clinical drug, Oxaliplatin. The correlation between GLUT1 expression and antitumor effects are also confirmed. The study provides fundamental information supporting the potential of the 2-DG conjugated platinum (II) complexes as lead compounds for further pharmaceutical R&D.  相似文献   

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