A new class of model glycolipids: synthesis, characterization, and interaction with lectins.

A method is described for preparing model glycolipids by linking aldobionic acids to an alkylamine through an amide bond. These compounds may be rapidly prepared in large quantities. The glycolipids precipitate specifically with lectins. Precipitation occurs at glycolipid concentrations just above their critical micelle concentration.     

Poly-2''-deoxy-2''-fluoro-cytidylic acid: enzymatic synthesis, spectroscopic characterization and interaction with poly-inosinic acid.

The polymerization of 2'deoxy-2'-fluoro-cytidine-diphosphate (dCflDP) by polynucleotide phosphorylase is barely detectable in the presence of Mg++ under usual experimental conditions for polymerization of nucleoside diphosphates. High concentrations of enzyme have to be used to accomplish the synthesis. Mn++ is a better activator than Mg++ for the reaction. cCflDP inhibits the polymerization of CDP and has a Km=8.8X10-3M, six times higher than CDP.- The polymer, poly (dCfl), ressembles in many respects poly(C), but not poly(dC): the acid selfstructure forms at similar pK's; interaction with poly(I) yields a 1:1 complex the CD spectrum of which is similar to that of poly(I).poly(C). Finally, the Tm's of poly(I).poly(dCfl) are comparable to those of poly(I).poly(C).     

Mannosylated poly(ethylene oxide)-b-poly(epsilon-caprolactone) diblock copolymers: synthesis, characterization, and interaction with a bacterial lectin

A novel bioeliminable amphiphilic poly(ethylene oxide)-b-poly(epsilon-caprolactone) (PEO-b-PCL) diblock copolymer end-capped by a mannose residue was synthesized by sequential controlled polymerization of ethylene oxide and epsilon-caprolactone, followed by the coupling of a reactive mannose derivative to the PEO chain end. The anionic polymerization of ethylene oxide was first initiated by potassium 2-dimethylaminoethanolate. The ring-opening polymerization of epsilon-caprolactone was then initiated by the omega-hydroxy end-group of PEO previously converted into an Al alkoxide. Finally, the saccharidic end-group was attached by quaternization of the tertiary amine alpha-end-group of the PEO-b-PCL with a brominated mannose derivative. The copolymer was fully characterized in terms of chemical composition and purity by high-resolution NMR spectroscopy and size exclusion chromatography. Furthermore, measurements with a pendant drop tensiometer showed that both the mannosylated copolymer and the non-mannosylated counterpart significantly decreased the dichloromethane/water interfacial tension. Moreover, these amphiphilic copolymers formed monodisperse spherical micelles in water with an average diameter of approximately 11 nm as measured by dynamic light scattering and cryo-transmission electron microscopy. The availability of mannose as a specific recognition site at the surface of the micelles was proved by isothermal titration microcalorimetry (ITC), using the BclA lectin (from Burkholderia cenocepacia), which interacts selectively with alpha-D-mannopyranoside derivatives. The thermodynamic parameters of the lectin/mannose interaction were extracted from the ITC data. These colloidal systems have great potential for drug targeting and vaccine delivery systems.     

Conjugates of cyclooligosaccharide scaffolds and carbohydrate ligands: Methods for synthesis and the interaction with lectins

The main approaches to the preparation of mono- and oligodentate glycoconjugates based on cyclodextrin and cyclooligo-β-(1 → 6)-D-glucosamine scaffolds are surveyed in the review. The data on the biological activity of the glycoconjugates are discussed exemplified in their interaction with carbohydrate-binding proteins named lectins.     

Poly(L-lysine)-graft-chitosan copolymers: synthesis, characterization, and gene transfection effect

Polypeptide/polysaccharide graft copolymers poly(L-lysine)-graft-chitosan (PLL-g-Chi) were prepared by ring-opening polymerization (ROP) of epsilon-benzoxycarbonyl L-lysine N-carboxyanhydrides (Z-L-lysine NCA) in the presence of 6-O-triphenylmethyl chitosan. The PLL-g-Chi copolymers were thoroughly characterized by 1H NMR, 13C NMR, Fourier transform infrared (FT-IR), and gel permeation chromatography (GPC). The number-average degree of polymerization of PLL grafted onto the chitosan backbone could be adjusted by controlling the feed ratio of NCA to 6-O-triphenylmethyl chitosan. The particle size of the complexes formed from the copolymer and calf thymus DNA was measured by dynamic light scattering (DLS). It was found in the range of 120 approximately 340 nm. The gel retardation electrophoresis showed that the PLL-g-Chi copolymers possessed better plasmid DNA-binding ability than chitosan. The gene transfection effect in HEK 293T cells of the copolymers was evaluated, and the results showed that the gene transfection ability of the copolymer was better than that of chitosan and was dependent on the PLL grafting ratio. The PLL-g-Chi copolymers could be used as effective gene delivery vectors.     

Diblock copolymers based on dihydroxyacetone and ethylene glycol: synthesis, characterization, and nanoparticle formulation

Polymeric biomaterials have played an integral role in tissue engineering, biomedical devices, and targeted drug delivery. Block copolymers are especially important because their physical and chemical properties can be controlled by adjusting the ratio, size, and type of constituting blocks. Herein, the synthesis and characterization of diblock copolymers composed of poly(ethylene glycol) and a polycarbonate based on the metabolic intermediate, dihydroxyacetone, are reported. The length of the dihydroxyacetone-based block was controlled by adjusting the reactant feed ratios and initiator injection conditions. Intermediates and final products were characterized via (1)H NMR, GPC, DSC, TGA, and diffusion-ordered NMR spectroscopy. The dihydroxyacetone-based hompolymer is insoluble in water and most organic solvents, but is hydrophilic in nature. This, coupled with poly(ethylene glycol)'s solubility characteristics, allows the block copolymer to form nanoparticles in aqueous and organic anti-solvents. Dynamic light scattering and TEM results indicated the formation of spherical nanoparticles.     

Chiral multinuclear macrocyclic polyamine complexes: synthesis, characterization and their interaction with plasmid DNA

A series of multinuclear macrocyclic polyamine metal (Zn(2+), Cu(2+), Co(2+)) complexes containing chiral dipeptide linkage were synthesized and used as artificial nuclease enzyme model. The interaction between the complexes and plasmid DNA (pUC19) was studied, and the results revealed that these complexes could act as powerful catalysts for the cleavage of plasmid DNA under physiological conditions.     

Biodegradable amphiphilic block copolymers bearing protected hydroxyl groups: synthesis and characterization

A new biodegradable amphiphilic block copolymer, poly(ethylene glycol)-b-poly(L-lactide-co-9-phenyl-2,4,8,10-tetraoxaspiro[5,5]undecan-3-one) [PEG-b-P(LA-co-PTO)], was successfully prepared by ring-opening polymerization (ROP) of L-lactide (LA) and functionalized carbonate monomer 9-phenyl-2,4,8,10-tetraozaspiro[5,5]undecan-3-one (PTO) in the presence of monohydroxyl poly(ethylene glycol) as macroinitiator using Sn(Oct)2 as catalyst. NMR, FT-IR, and GPC studies confirmed the copolymer structure. It could self-assemble into micelles in aqueous solution with critical micelle concentration (CMC) in the magnitude of mg/L, which changed with the composition of the copolymer. After catalytic hydrogenation, copolymers with active hydroxyl groups were obtained. Adhesion and proliferation of Vero cells on the copolymer films showed that the synthesized copolymers were good biocompatible materials. In vitro degradation of the copolymer before and after deprotection was investigated in the presence of proteinase K. The free hydroxyl groups on the copolymers were capable of further modification with biotin. This new amphiphilic block copolymer has great potential for both drug encapsulation and conjugate because of its low CMC and the presence of active hydroxyl groups.     

Legume lectins interact with muramic acid and N-acetylmuramic acid

The inhibitory potency of both muramic acid (MurAc) and N-acetylmuramic acid (MurNAc) on various legume lectins, including Glc/Man- and Gal/GalNAc-specific lectins, was investigated by a haemagglutination inhibition technique. Data indicated that many lectins, especially those specific for Glc/Man, specifically interact with MurAc and MurNAc often to a greater extent than with other monosaccharides and their derivatives, such as N-acetylglucosamine (GlcNAc) and sialic acid. Glc/Man-specific lectins were also shown to interact with the muramyl-dipeptide MurNAc-D-Ala-D-isoGln. These interactions could explain why various lectins readily agglutinate some bacterial strains of which cell walls contain peptidoglycans with high amounts of MurNAc.     

Novel synthesis and characterization of bioconjugate block copolymers having oligonucleotides

Novel and efficient synthesis of polymers terminated with nucleotides via the phosphoramidite method has been developed. A hydroxyl-terminated polymer was converted into a polymer capped with a nucleotide in three steps, where the conversion of the reactions was very high, almost 100%. By repetition of this synthetic method, a block copolymer composed of a synthetic polymer, polystyrene, and biological oligonucleotides with thymidine units has been successfully synthesized. A microphase-separated structure of this block copolymer was observed by both transmission electron microscopy and small-angle X-ray scattering, and a cylindrical structure was confirmed.     

Sialic acid-binding lectins: submolecular specificity and interaction with sialoglycoproteins and tumour cells

We examined the specificity of limulin,Limax flavus agglutinin (LFA) andSambucus nigra agglutinin I (SNA I) at the submolecular level of sialic acid, and characterized their interactions with a panel of structurally distinct sialoglycoproteins. In haemagglutination inhibition assays NeuAc--glycosides were stronger inhibitors for limulin and LFA than nativeN-acetylneuraminic acid (NeuAc). TheN-acetyl of NeuAc was crucial for binding to both lectins. N-thioacetylated NeuAc lost affinity for LFA, but still bound to limulin. Thus, distinct intermolecular interactions are involved in binding of sialic acid to the lectins. The glyceryl side chain was required for interaction with LFA, but not with limulin. SNA I specifically bound NeuAc2 6Gal1 4Glc, but not monomeric sialic acids. Limulin and LFA strongly interacted with O-chain glycoproteins, whereas SNA I preferred N-chain proteins that carry NeuAc2 6 residues. The lectins were compared with those fromCepaea hortensis andTachypleus tridentatus (TTA) and to wheat-germ agglutinin, and were then used to probe tumour cell lines for cell surface sialylation. With the exception of TTA, all lectins interacted with the tumour cells. Limulin distinguished between the low (Eb) and highly (ESb) metastatic mouse lymphoma lines by selectively agglutinating sialidase-treated ESb cells.Abbreviations BSM bovine submaxillary mucin - CHA I Cepaea hortensis agglutinin I - LFA Limax flavus agglutinin - NeuAc N-acetylneuraminic acid - OSM ovine submaxillary mucin - SNA I Sambucus nigra agglutinin I - THP Tamm-Horsfall protein - TTA Tachypleus tridentatus agglutinin     

Steroidal dihydrocarbothioic acid amido pyrazoles: synthesis,characterization, cytotoxicity and genotoxicity studies

A new series of steroidal dihydrocarbothioic acid amido pyrazole analogues were synthesized, and after characterization, evaluation for cytotoxicity, comet assay and western blotting was carried out. The synthesis of these analogues is convenient and involves two steps, i.e. aldol condensation as first step followed by nucleophilic addition of thiosemicarbazide across α, β-unsaturated carbonyl as a later step. Quantitative yields of more than 80 % are obtained in both the steps. After characterization by IR, ¹H NMR, ¹³C NMR, MS and analytical data, all the compounds of both series were tested for cytotoxic activity against a panel of different human cancer cell lines by MTT assay, during which compound 3e, 3f, 4e, 4f and 4h are very potent especially against HepG2 and MCF-7 cancer cell lines. Cell cycle analysis depicted the cell death in S-phase while as annexin V-FITC/PI analysis showed that compounds effectively induce apoptosis. Apoptotic degradation of DNA of MCF-7 cells in the presence of different steroidal derivatives was analysed by agarose gel electrophoresis and visualized by ethidium bromide staining (comet assay). In western blotting analysis, the relative expressions of relevant apoptotic markers depicted an apoptosis by steroidal dihydropyrazole in MCF-7 cancer cells.     

Infrared spectroscopic characterization of the interaction of lipid bilayers with phenol, salicylic acid and o-acetylsalicylic acid

The interaction of phenol (PHE), salicylic acid (SA) and o-acetylsalicylic acid (ASA) with bilayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) was investigated by infrared spectrometry. The temperature of the main gel to liquid crystal phase transition of DPPC is markedly depressed in the presence of the three guest molecules. The temperature depression depends on the nature and concentration of the additives. The temperature of the pretransition is also affected by these guest molecules and the depression in temperature is even more pronounced than that of the main transition temperature. Possible modes of interaction of these guest molecules with the lipid bilayers are discussed.     

Novel ebselen-porphyrin conjugates: synthesis and nucleic acid interaction study

Novel porphyrins bearing ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]-one) moiety were synthesized and characterized. Their interactions with herring sperm DNA were studied by means of UV-visible, fluorescence, circular dichroism spectroscopy, and gel electrophoresis.     

Monometallic complexes of 1,4,7,10-tetraazacyclododecane containing an imidazolium side: synthesis, characterization, and their interaction with plasmid DNA

The synthesis of macrocyclic polyamine monometallic complexes containing imidazolium salt groups was reported. Their interaction with pUC19 plasmid DNA was studied. The result showed that these complexes can catalyze the DNA cleavage with unprecedented reactivity under physiological conditions.