Interaction of alkylating oligonucleotide derivatives with mammalian cells. A study of the uptake mechanism of derivative cells

Interaction of alkylating deoxyribooligonucleotide derivatives, bearing 4-[(N-2-chloroethyl-N-methyl)amino]benzylamine residues at their 5'-terminal phosphates, with mouse fibroblasts L929 and with ascite carcinoma cells Krebs 2 has been investigated. It was found, that the derivatives are taken up by the cells according to the endocytosis mechanism. At high concentration of the oligonucleotide derivatives in the cultivation medium (greater than 10 microM), the fluid phase endocytosis is the major pathway of uptake; binding of the derivatives by the cells is partially reversible and their intracellular mean concentration approaches 1/20 of their extracellular concentration. At low concentration of the oligonucleotide derivatives, the predominant mechanism is the more efficient adsorption endocytosis; at concentration of the derivatives less than 0.5 microM, their mean intracellular concentration exceeds that in the culture medium. Stability of the oligonucleotide derivatives in cells depends on their nucleotide composition. Their nucleolytic degradation rate is low enough to allow them to react with cellular biopolymers.     

Effect of substituents of the benzoquinone ring on electron-transfer activities of ubiquinone derivatives

The effect of substituents on the 1,4-benzoquinone ring of ubiquinone on its electron-transfer activity in the bovine heart mitochondrial succinate-cytochrome c reductase region is studied by using synthetic ubiquinone derivatives that have a decyl (or geranyl) side-chain at the 6-position and various arrangements of methyl, methoxy and hydrogen in the 2, 3 and 5 positions of the benzoquinone ring. The reduction of quinone derivatives by succinate is measured with succinate-ubiquinone reductase and with succinate-cytochrome c reductase. Oxidation of quinol derivatives is measured with ubiquinol-cytochrome c reductase. The electron-transfer efficacy of quinone derivatives is compared to that of 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone. When quinone derivatives are used as the electron acceptor for succinate-ubiquinone reductase, the methyl group at the 5-position is less important than are the methoxy groups at the 2- and 3-positions. Replacing the 5-methyl group with hydrogen causes a slight increase in activity. However, replacing one or both of 2- and 3-methoxy groups with a methyl completely abolishes electron-acceptor activity. Replacing the 3-methoxy group with hydrogen results in a complete loss of electron-acceptor activity, while replacing the 2-methoxy with hydrogen results in an activity decrease by 70%, suggesting that the methoxy group at the 3-position is more specific than that at the 2-position. The structural requirements for quinol derivatives to be oxidized by ubiquinol-cytochrome c reductase are less strict. All 1,4-benzoquinol derivatives examined show partial activity when used as electron donors for ubiquinol-cytochrome c reductase. Derivatives that possess one unsubstituted position at 2, 3 or 5, with a decyl group at the 6-position, show substrate inhibition at high concentrations. Such substrate inhibition is not observed when fully substituted derivatives are used. The structural requirements for quinone derivatives to be reduced by succinate-cytochrome c reductase are less specific than those for succinate-ubiquinone reductase. Replacing one or both of the 2- and 3-methoxy groups with a methyl and keeping the 5-position unsubstituted (plastoquinone derivatives) yields derivatives with no acceptor activity for succinate-Q reductase. However, these derivatives are reducible by succinate in the presence of succinate-cytochrome c reductase. This reduction is antimycin-sensitive and requires endogenous ubiquinone, suggesting that these (plastoquinone) derivatives can only accept electrons from the ubisemiquinone radical at the Qi site of ubiquinol-cytochrome c reductase, and cannot accept electrons from the QPs of succinate-ubiquinone reductase.     

Synthesis and inhibitory activity against COX-2 catalyzed prostaglandin production of chrysin derivatives

A series of chrysin derivatives were prepared and evaluated for their inhibitory activities of cyclooxygenase-2 catalyzed prostaglandin production. Chrysin derivatives were prepared from 2-hydroxyacetophenone, 2,4-dihydroxyacetophenone and 2,6-dihydroxyacetophenone in 2 to 4 steps, respectively. Methxoylated chrysin derivatives were converted to the corresponding hydroxylated chrysin derivatives by the reaction with BBr(3) in good yields. The inhibitory activity of the chrysin derivatives against prostaglandin production from lipopolysaccharide-treated RAW 264.7 cells was measured. We found that chrysin derivatives with 3',4'-dichloro substituents (5e, 6e and 7e) exhibited good inhibitory activity of prostaglandin production.     

Synthesis of organosoluble chitosan derivatives with polyphenolic side chains

A one-pot synthesis was used to produce chitosan derivatives with polyphenolic side chains via a regioselective phenolic coupling reaction. Under Mannich reaction conditions, treatment of chitosan with formaldehyde and methyl 2,4-dihydroxybenzoate gave N-(2,6-dihydroxy-3-methoxycarbonylphenyl)methylated chitosan in good yield (87%). Formation of a CC bond occurred regioselectively at the C(3) position of methyl 2,4-dihydroxybenzoate. Chitosan derivatives having various phenolic compounds as a side chain were easily synthesized in a similar manner. The chitosan derivatives showed good biodegradability and improved their solubility in methanol (9.8mgmL(-1)) and 2-methoxyethanol (> 10mgmL(-1)). The UV protection provided by the derivatives with phenolic benzophenone side chain was evaluated using UV spectra of polyethylene terephthalate and poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) films coated with the derivatives and the derivatives absorbed effectively in the UV-A region (<60%). Self-aggregation of the chitosan derivatives with the phenolic side chain was observed by using a fluorescent probe in aqueous solution.     

Identification of ketoses by use of their peracetylated oxime derivatives: A G.L.C.-M.S. approach

A method based on peracetylated oxime (PAKO) derivatives has been developed for rapid g.l.c.-m.s. survey of ketoses. This derivatization procedure (and the chromatographic analysis of these derivatives) is identical to one previously employed to identify aldoses by means of peracetylated aldononitrile (PAAN) derivatives. The production of chemically different derivatives from the aldoses and ketoses by the same derivatization procedure greatly simplifies the chromatographic separation of the derivatives of the ketoses from those of the aldoses, and also results in distinctively different, mass-spectral fragmentation-pathways for the two sets of derivatives. Both the electron-impact (e.i.) and ammonia chemical-ionization (c.i.) mass spectra of PAKO derivatives have been examined. Extensive differences between the fragmentation-pathways of the PAAN and the PAKO derivatives have been observed both by e.i.m.s. and ammonia c.i.m.s. The g.l.c.-m.s. of these PAKO derivatives, in conjunction with various, isotopic variants of the derivatization process, can yield extensive structural information with regard to the starting saccharides associated with the known, or unknown, g.l.c. peaks. The g.l.c. and mass-spectral properties of highly O-methylated PAKO derivatives of d-fructose are compared, and contrasted, to those of the PAKO derivatives of non-O-methylated saccharides. The chromatographic properties of derivatives of oligosaccharides that result from the PAAN-PAKO derivatization procedure have also been studied.     

Preparation of some starch-based neutral chelating agents

Various neutral starch derivatives have been prepared by reacting maize starch with mono- and dimethylol resins based on urea, thiourea, and melamine. The factors affecting these reactions were studied. These factors include curing duration, catalyst, and resin concentrations. The starch derivatives so prepared were used in heavy-metal removal from solutions. The sorption ability of those derivatives depends on resin type and metal ions. The sorption values of different starch derivatives follow the order (a) monomethylol resin-starch > dimethylol resin starch; (b) thiourea resin-starch > urea resin-starch > melamine resin-starch. The sorption efficiency (%) of starch derivatives increases with increasing nitrogen content, reaching a maximum value and then decreasing. The sorption values of Hg2+ (mmol/mol resin) of different starch monomethylol derivatives at the maximum values were 1135, 2624, and 2538 for urea, thiourea, and melamine derivatives, respectively. This indicates that urea derivatives act as bidentate ligands, while thiourea and melamine act as tridentate ligands.     

Complementary addressed modification of plasmid DNA

The possibility to accomplish the sequence-specific chemical modification of superhelical DNA with reactive oligonucleotide derivatives was demonstrated. Plasmids containing fragments of the immunoglobulin gene were modified with alkylating derivatives of oligonucleotides complementary to a nucleotide sequence in the immunoglobulin gene. In contrast to the relaxed plasmid DNAs, superhelical DNAs (sigma = -0.1) were found to be attacked by the derivatives at the target nucleotide sequence. The efficiency of the reaction increases with the increase of the plasmids negative superhelicity. It was found also that the denatured derivatives. The sequence-specific modification of plasmid DNAs with the reactive oligonucleotide derivatives can be used for the site-directed mutagenesis and the investigation of the repair processes.     

The isolation of acyl-CoA derivatives as products of partial reactions in the microsomal chain elongation of fatty acids.

An analysis of overall chain elongation, condensation, beta-hydroxyacyl-CoA dehydrase and 2-trans enoyl-CoA reductase reactions, using the appropriate CoA derivatives as substrates which are required in the microsomal chain elongation of both palmitoyl-CoA and 6,9-octadecadienoyl-CoA, demonstrated that in each instance, the products of these reactions were the CoA derivatives. Reverse dehydrase reactions run with 2-trans enoyl-CoA derivatives as substrates, in the absence of NADPH, revealed that the product was the beta-hydroxyacyl-Coa. In the presence of NADPH, incubations with beta-hydroxyacyl-CoA demonstrated that both the 2-trans derivatives and the alpha, beta-saturated product were recovered as their CoA derivatives. These latter findings are more consistent with the involvement of discrete dehydrase and 2-trans-enoyl-CoA reductase enzymes rather than a single protein catalyzing two reactions.     

Enhanced microtubule binding and tubulin assembly properties of conformationally constrained paclitaxel derivatives

Microtubule binding and tubulin assembly promotion by a series of conformationally restricted paclitaxel (PTX) derivatives was investigated. In these derivatives, the C-4 acetate of the taxane is tethered to the C-3' phenyl at ortho and meta positions with different length linkers. The apparent affinity of these derivatives for GMPCPP-stabilized microtubules was assessed by a competition assay, and their influence on microtubule polymerization was evaluated by measuring the critical concentration of GDP-tubulin in the presence of the respective molecule. In general, taxane derivatives with higher apparent affinity for microtubules induced tubulin assembly more efficiently. Among the derivatives, molecules with the shortest tether display the strongest affinity for microtubules. These derivatives exhibited enhanced microtubule stabilization properties and efficiently induced GDP-tubulin assembly into microtubules at low temperature of 12 degrees C and in the absence of Mg2+ ions in 0.1 M PIPES. Based on molecular dynamics simulations, we propose that the enhanced ability to assemble microtubules by these taxane derivatives is linked to their ability to effectively shape the conformation of the M-loop of tubulin for cross-protofilament interaction.     

New ribose-modified fluorescent analogs of adenine and guanine nucleotides available as substrates for various enzymes

The synthesis of fluorescent derivatives of nucleosides and nucleotides, by reaction with isatoic anhydride in aqueous solution at mild pH and temperature, yielding their 3'-O-anthraniloyl derivatives, is here described. The N-methylanthraniloyl derivatives were also synthesized by reaction with N-methylisatoic anhydride. Upon excitation at 330-350 nm these derivatives exhibited maximum fluorescence emission at 430-445 nm in aqueous solution with quantum yields of 0.12-0.24. Their fluorescence was sensitive to the polarity of the solvent; in N,N-dimethylformamide the quantum yields were 0.83-0.93. The major differences between the two fluorophores were the longer wavelength of the emission maximum of the N-methylanthraniloyl group and its greater quantum yield in water. All anthraniloyl derivatives, as well as the N-methylanthraniloyl ones, had virtually identical fluorescent properties, regardless of their base structures. The ATP derivatives showed considerable substrate activity as a replacement of ATP with adenylate kinase, guanylate kinase, glutamine synthetase, myosin ATPase and sodium-potassium transport ATPase. The ADP derivatives were good substrates for creatine kinase and glutamine synthetase (gamma-glutamyl transfer activity). The GMP and adenosine derivatives were substrates for guanylate kinase and adenosine deaminase, respectively. All derivatives had only slightly altered Km values for these enzymes. While more fluorescent in water, the N-methylanthraniloyl derivatives were found to show relatively low substrate activities against some of these enzymes. The results indicate that these ribose-modified nucleosides and nucleotides can be versatile fluorescent substrate analogs for various enzymes.     

Obtaining and study of monosaccharide derivatives of low-molecular-weight chitosan

The possibility of obtaining monosaccharide derivatives of low-molecular-weight chitosan with the use of the Maillard reaction was studied. Chitosan derivatives (molecular weight, 24 and 5 kDa) obtained with glucosamine, N-acetyl galactosamine, galactose, and mannose with a substitution degree of 4-14% and a yield of 60-80% were obtained. Some physicochemical and biological properties of these derivatives were studied. We showed that monosaccharide derivatives of low-molecular-weight chitosan exhibited antibacterial activity. Chitosan at a concentration of 0.01% caused 100% death of bacteria B. subtilis and E. coil. The strongest antibacterial effect was exhibited by 24-kDa derivatives: only 0.02-0.08% of cells survived. These derivatives were two orders of magnitude more effective than the 5-kDa chitosan modified with galactose.     

Synthesis and antitumor activity of novel C-8 ester derivatives of leinamycin

A novel series of C-8 ester derivatives of leinamycin are described. Condensation of N-substituted amino acids or carboxylic acids containing polyether moiety with leinamycin resulted in the C-8 ester derivatives with good antitumor activity in several experimental models. Among these derivatives, compound 4e, which has five ethylene glycol ether units in the C-8 acyl group, showed potent antitumor activity against human tumor xenograft. Combination with the modification of the dithiolanone moiety was applied to these C-8 ester derivatives and some of them also showed good antitumor activity.     

The influence of the different inductivity of acetyl phenyl-thiosemicarbazone-chitosan on antimicrobial activities

Ten different acetyl phenyl-thiosemicarbazone derivatives of chitosan were synthesized. Their structures were characterized by FT-IR and elemental analysis. The antimicrobial behaviors of CS and its derivatives against four species of bacteria and four crop-threatening pathogenic fungi were investigated in this paper. The results indicated that the antimicrobial activities of acetyl phenyl-thiosemicarbazone derivatives are much better than that of pure CS. The minimum value of MIC and MBC of the derivatives against Escherichia coli was 7.03 and 225 μg mL(-1), respectively. All of the derivatives had significant inhibiting effect on the investigated fungi in the concentration of 50-500 μg mL(-1), and the maximum inhibitory index was 93.10%. The bioactivities of the derivatives have relationship with the grafted groups with different inductivity.     

Glucosylation of phenolic compounds by Pharbitis nil hairy roots: I. Glucosylation of coumarin and flavone derivatives

Hairy roots of medicinal morning glory (Pharbitis nil) showed potent glucosylation activity against umbelliferone and aesculetin, so the glucosylation activity against several phenolic compounds was tested. Some coumarin derivatives and flavone derivatives having phenolic hydroxyl groups were incubated with the hairy roots. The coumarin derivatives and flavone derivatives almost disappeared from the culture medium in half a day. In the case of the coumarin derivatives, a 7-hydroxyl group was easily glucosylated. A methyl group at C-8 somewhat decreased the glucosylation to a hydroxyl group at C-7 of the coumarin skeleton. The 4-hydroxy coumarin derivatives were changed to acetophenone-type glucosides by incubation with the hairy roots through decarboxylation. Several flavonol derivatives were tested for glucosylation by the hairy roots. 3-Hydroxy flavone, 3.6-dihydroxyflavone and 3,7-dihydroxyflavone were glucosylated to give 3-glucosylated derivatives. Of these, 3,6-dihydroxyflavone was highly glucosylated, but not 3-hydroxyflavone or 3,7-dihydroxyflavone to the same degree. In the case of the flavones, a 3-hydroxy group could be predominantly glucosylated, and hydroxyl groups on the A and B ring of the flavones affected glucosylation by the hairy roots.     

Anti-proliferative activity and structure-activity relationship of honokiol derivatives

As a known natural product with anti-tumor activity, honokiol has been widely researched and structural modified. Lots of honokiol derivatives have been found to possess good anti-proliferative activity and showed great potential in cancer therapy, but the SAR (structure-activity relationship) was still confused. Here in, the SAR were comprehensively researched by summary of reported derivatives and synthesis of novel derivatives. Amongst novel derivatives, the promising compounds A6 and A10 exhibited potent and selective anti-proliferative activities against K562 cell line with the IC₅₀ values of 5.04 and 7.08 μM respectively. The SAR was discussed around honokiol and 79 derivatives by the means of CoMFA and theoretical calculation, which provided useful suggestion for further structural optimization of honokiol derivatives.     

Fluorination of 6-methyluracil and its nlcleosides.

6-Methyluracil and its perbenzoylated 1-(beta-D-ribofuranosyl) and 1-(2-deoxy-beta-D-ribofuranosyl) derivatives afford on treatment with elemental fluorine in acetic acid solutions, the corresponding derivatives of 5-fluoro-6-methyluracil and 5-fluoro-6-fluoromethyluracil. The free nucleosides have been obtained from the protected derivatives by methanolysis. The CH2F linkage in 5-fluoro-6-fluoromethyluracil derivatives is stable towards hydrolysis and nucleophilic agents.     

Fluorescent derivatives of bile salts. II. Suitability of NBD-amino derivatives of bile salts for the study of biological transport.

Interaction of unconjugated and taurine-conjugated NBD-amino-dihydroxy-5 beta-cholan-24-oic acids bearing the fluorophor in the 3 alpha, 3 beta, 7 alpha, 7 beta, 12 alpha, or 12 beta position with albumin results in a small hypsochromic shift of the emission maximum and an increase in quantum yield, suggesting binding by hydrophobic interactions. The different unconjugated fluorescent bile salt derivatives are metabolized by intact rat liver in different ways. The unconjugated 3 beta-NBD-amino derivative is completely transformed to its taurine conjugate and secreted as such, whereas the 3 alpha-NBD-amino derivative is completely transformed to a polar fluorescent compound not identical with its taurine conjugate. The unconjugated 7 alpha- and 7 beta-NBD-amino derivatives are only partially conjugated with taurine and mainly secreted in unmetabolized form. The unconjugated 12 alpha- and 12 beta-NBD-amino derivatives are not at all transformed to their taurine conjugates, but are partially metabolized to unidentified compounds. They are predominantly secreted as the unmetabolized compounds. In contrast to the unconjugated derivatives, all taurine-conjugated fluorescent bile salt derivatives are secreted into bile unmetabolized. With the exception of the 3 alpha-compound, all synthesized taurine-conjugated fluorescent derivatives interfere with the secretion of cholyltaurine. Differential photoaffinity labeling studies using (7,7-azo-3 alpha,12 alpha- dihydroxy-5 beta-cholan-24-oyl)-2'-[2'-3H(N)]aminoethanesulfonate as a photolabile derivative revealed that in liver cells all fluorescent bile salt derivatives interact with the same polypeptides as the physiological bile salts. The hepatobiliary transport of taurine-conjugated NBD-amino bile salt derivatives is, due to hydrophobic interactions, accompanied by an increase in fluorescence intensity which is favorable for the study of biological bile salt transport by fluorescence microscopy.     

Complementary addressed modification and cleavage of a single stranded DNA fragment with alkylating oligonucleotide derivatives.

A single stranded DNA fragment was modified with alkylating derivatives of oligonucleotides complementary to a certain nucleotide sequences in the fragment. The derivatives carried aromatic 2-chloroethylamino groups at their 3'- or 5'-terminal nucleotide residues. Some of the derivatives carried both alkylating group and intercalating phenazine group which stabilized complementary complexes. It was found that these oligonucleotide derivatives modify the DNA fragment in a specific way near the target complementary nucleotide sequences, and the DNA fragment can be cleaved at the alkylated nucleotides positions. Alkylating derivatives carrying phenazine groups were found to be the most efficient in reaction with the DNA fragment.     

Galactosylated derivatives of low-molecular-weight chitosan: production and properties

Chitosan, a binary heteropolysaccharide consisting of 2-acetamide-2-deoxy-beta-D-glucopyranose and 2-amino-2-deoxy-beta-D-glucopyranose residues linked in different proportions via beta-glycosidic bonds. The presence of a primary amino group in the chitosan structure allows for the synthesis of various derivatives. The procedure of obtaining activated N-hydroxysuccinimide esters with the use of lactobionic acid was applied to obtain galactosylated derivatives of low-molecular-weight chitosan with a substitution degree varying from 8 to 23%. The properties of these derivatives (viscosity, solubility, and biodegradability) were studied. These derivatives are well soluble at pH values greater than the acidity constant of amino groups of chitosan (6.5). Broadening the pH range towards increase and the presence of galactose residues allows these derivatives to be used in working with biological objects.     

Binding of cholera toxin B-subunits to derivatives of the natural ganglioside receptor, GM1.

In a previous paper we showed that the B-pentamer of cholera toxin (CT-B) binds with reduced binding strength to different C(1) derivatives of N-acetylneuraminic acid (NeuAc) of the natural receptor ganglioside, GM1. We have now extended these results to encompass two large amide derivatives, butylamide and cyclohexylmethylamide, using an assay in which the glycosphingolipids are adsorbed on hydrophobic PVDF membranes. The latter derivative showed an affinity approximately equal to that earlier found for benzylamide ( approximately 0.01 relative to native GM1) whereas the former revealed a approximately tenfold further reduction in affinity. Another derivative with a charged C(1)-amide group, aminopropylamide, was not bound by the toxin. Toxin binding to C(7) derivatives was reduced by about 50% compared with the native ganglioside. Molecular modeling of C(1) and C(7) derivatives in complex with CT-B gave a structural rationale for the observed differences in the relative affinities of the various derivatives. Loss of or altered hydrogen bond interactions involving the water molecules bridging the sialic acid to the protein was found to be the major cause for the observed drop in CT-B affinity in the smaller derivatives, while in the bulkier derivatives, hydrophobic interactions with the protein were found to partly compensate for these losses.