Synthesis,characterization and fluorescent properties of water-soluble glycopolymer bearing curcumin pendant residues

Curcumin is a potential natural anticancer drug with low oral bioavailability because of poor water solubility. The aqueous solubility of curcumin is enhanced by means of modification with the carbohydrate units. Polymerization of the curcumin-containing monomer with carbohydrate-containing monomer gives the water-soluble glycopolymer bearing curcumin pendant residues. The obtained copolymers (P1 and P2) having desirable water solubility were well-characterized by infrared spectroscopy (IR), nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), UV–Vis absorption spectroscopy, and photoluminescence spectroscopy. The copolymer P2 with a molar ratio of 1:6 (curcumin/carbohydrate) calculated from the proton NMR results exhibits a similar anticancer activity compared to original curcumin, which may serve as a potential chemotherapeutic agent in the field of anticancer medicine.     

Synthesis and physical properties of anti-HIV antisense oligonucleotides bearing terminal lipophilic groups.

A number of phosphoramidite monomers have been prepared and used in the synthesis of antisense phosphorothioate oligonucleotides bearing 5'-polyalkyl and cholesterol moieties. Similar groups have also been attached to the 3'-end of oligonucleotides by means of functionalised CPG. Melting temperatures of duplexes formed between phosphorothioate oligonucleotides with lipophilic end-groups and complementary DNA strands were found to be identical to those formed by the equivalent unmodified phosphorothioates.     

Synthesis and chiroptical properties of a helical poly(phenylacetylene) bearing optically active pyrene pendants

A novel poly(phenylacetylene) derivative bearing optically active pyrene moieties as the pendant groups (poly-(R)-1) was prepared by the polymerization of the corresponding monomer (R)-1 in the presence of a rhodium catalyst, and its chiroptical property was investigated. Poly-(R)-1 exhibited an induced circular dichroism (ICD) in the polymer backbone region due to the predominantly one-handed helical conformation. The ICD pattern dramatically changed and was accompanied by inversion of the Cotton effect sign in response to a change in the temperature and solvent, indicating that poly-(R)-1 underwent a helix-helix transition in response to the external stimuli.     

Synthesis and physicochemical properties of new tripodal amphiphiles bearing fatty acids as a hydrophobic group

Saturated fatty acids (FA) were grafted using tyrosine as a spacer group to the cyclotriphosphazene ring along with equimolar hydrophilic methoxy poly(ethylene glycol) (MPEG) in cis-nongeminal way. Seven new cyclotriphosphazene amphiphiles were prepared from combinations of hydrophilic MPEGs with different molecular weights of 350, 550, 750 and 1000 and four different fatty acids of different hydrophobicity including lauric, myristic, palmitic and stearic acids. These steric amphiphiles bearing fatty acids as a hydrophobic group were found to form more stable micelles with very low critical micelle concentrations (CMC) (2.95–7.80 mg/L) compared with oligopeptide analogues, and their highly hydrophobic core environment is unique and potentially useful for various biomedical applications.     

Synthesis and properties of novel antisense oligonucleotides bearing an anthraquinone moiety at an internucleotide linkage.

Antisense oligonucleotides bearing an anthraquinone moiety at an internucleotide linkage were synthesized utilizing the stereoisomers of anthraquinone incorporated T-C dimer phosphoramidite derivatives. Some physicochemical properties of the anthraquinon bearing oligomers were investigated.     

Synthesis and properties of modified oligonucleotides.

Phosphorothioate oligonucleotide analogs conjugated to cholesteryl by a neutral, 6 atom linker are more effective inhibitors of HIV-1 in cell culture than the corresponding analogs conjugated via a phosphorothioate group. The antiviral activity correlates with the hydrophobic character of the oligonucleotide. Some new synthetic methodology is also discussed.     

Synthesis and properties of oligonucleotides containing a cholesterol thymidine monomer

Highly selective base-pair recognition makes DNA a suitable building block for orderly self-assembled structures. For some applications in nanotechnology DNA complexes need to be fixed onto surfaces. To fulfil this requirement on lipid membranes we have synthesised a thymidine monomer modified with a cholesterol moiety. Solution studies show that the melting temperature (Tm) of the duplex, with adjacent cholesterols on each strand, is much higher than that of the unmodified duplex.     

Synthesis and triplex binding properties of oligonucleotides containing a novel nucleobase

The thiazolo-indole compound 1 bearing the complementary donor-acceptor-donor sites (dad) was designed for specific recognition of an AT inverted base pair in pyrimidine triple helix motif. It was successfully incorporated into 14-mer oligonucleotide using a serinol unit as sugar derivative. The triple helix hybridization studies were examined by means of thermal denaturation experiments with a 26-mer DNA duplex containing the AT inverted base pair.     

Synthesis and properties of oligonucleotides carrying cryptolepine derivatives

A carboxy derivative of the antimalarial cytotoxic drug cryptolepine was introduced into synthetic oligonucleotides by reaction of the carboxy derivative of cryptolepine with oligonucleotides carrying an amino group either at the 3'- or at the 5'-end. Oligonucleotides carrying the cryptolepine derivative bind their complementary sequences with greater affinity than unmodified ones. When cryptolepine is attached to a polypyrimidine oligonucleotide designed to form a parallel triplex, the triplex shows none or weak stabilization.     

Synthesis and hybridization properties of inverse oligonucleotides.

The synthesis of adenine and thymine cyclopentylethyl nucleosides is presented. This novel constrained monomeric building block is very difficult to incorporate into oligonucleotides. It was introduced in 13mer oligodeoxynucleotide sequences at a single position using H-phosphonate chemistry. Phosphoramidite chemistry completely failed in this particular case. The H-phosphonate building blocks were obtained starting from the corresponding phosphoramidites. Stability of duplexes with RNA and DNA is significantly reduced.     

Preparation of a DNA matrix via an electrochemically directed copolymerization of pyrrole and oligonucleotides bearing a pyrrole group.

A new methodology for the preparation of addressed DNA matrices is described. The process includes an electrochemically directed copolymerization of pyrrole and oligonucleotides bearing on their 5' end a pyrrole moiety introduced by phosphoramidite chemistry. The electro-controlled synthesis of the copolymer (poly-pyrrole) gives, in one step, a solid conducting film deposited on the surface of an electrode. The resulting polymer consists of pyrrole chains bearing covalently linked oligonucleotide. The polymer growth is limited to the electrode surface, so that it is possible to prepare a DNA matrix on a multiple electrode device by successive copolymerizations. A support bearing four oligonucleotides was used to detect three ras mutations on a synthetic DNA fragment.     

Synthesis and properties of oligonucleotides containing 2'-pyrenylalkyluridine.

The synthesis, binding and fluorescence properties of oligonucleotides containing the uridine modified at the 2'-position by a pyrene group using different length of linker arm have been described. It is demonstrated that the oligonucleotides possessing a C3-amide group at the 2'-position display an enhanced signal of the pyrene monomer fluorescence upon binding to DNA segments.     

Synthesis and properties of oligonucleotides containing aminodeoxythymidine units.

Procedures are described for synthesis via solid support methodology of oligonucleotide analogues derived in part from 3'-amino-3'-deoxythymidine or 5'-amino-5'-deoxythymidine. Oligothymidylate decamers terminated with a 3'-amino group or containing a 3'-NHP(O)(O-)O-5' internucleoside link are found to form unusually stable complexes with poly(dA), poly(A), and oligo(dA). For related derivatives of 5'-amino-5'-deoxythymidine enhancement is less or absent, and in the case of multiple substitution destabilization of the heteroduplex may be observed. That the effect of the 3'-amino group is general for oligonucleotide derivatives is indicated by enhanced Tm values for heteroduplex complexes of the mixed-base oligomer, d(TATTCAGTCAT(NH2)), and the methyl phosphonate derivatives, TmTmTmTmTmTmTmTmTmT(NH2) and d(TmAmTmTmCmAmGmTmCmAmT(NH2)).     

Synthesis of new analogues of salacinol containing a pendant hydroxymethyl group as potential glycosidase inhibitors

The synthesis of new analogues of the naturally occurring glycosidase inhibitor, salacinol, and its ammonium analogue, ghavamiol is described. These analogues contain an additional hydroxymethyl group at C-1, which was intended to form additional polar contacts within the active site of glycosidase enzymes. The target zwitterionic compounds were synthesized by means of nucleophilic attack at the least hindered carbon atom of 2,4-O-benzylidene-l (or d)-erythritol 1,3-cyclic sulfate by 2,5-anhydro-1,3:4,6-di-O-benzylidene-2,5-dideoxy-5-thio (or 1,5-imino)-l-iditol.     

Physicochemical properties of a human glycoprotein bearing blood group A activity

A human erythrocyte glycoprotein was isolated and purified from blood of group A+1 by a procedure involving chloroform-methanol extraction and affinity chromatography on Helix pomatia lectin-Sepharose 6MB, and some of its physicochemical properties were determined. The resulting preparation was homogeneous as indicated by polyacrylamide gel electrophoresis. The glycoprotein contained nearly 60% carbohydrate and 40% protein. It was water-soluble and inhibited the agglutination of A-erythrocytes. Its molecular weight was 41,900 (amino acid analysis) or 55,200 (light scattering), whereas electrophoresis revealed two bands of 43,000 and 76,000 Da. The ORD spectrum was consistent with 30% alpha-helix, 20% beta-sheet, and 50% random coil. Intrinsic viscosity was 14.61 ml.g-1, partial specific volume was roughly 0.66, isoelectric and isoionic points were 6.90 and 6.95, respectively. The glycoprotein differs from glycophorin and appears to be one of the minor glycoproteins of the human erythrocyte membrane.     

Synthesis and binding properties of oligonucleotides carrying nuclear localization sequences

The synthesis of oligonucleotides carrying nuclear localization peptide sequences is described using two strategies: first, oligonucleotides carrying a thiol group at the 5' end were reacted with maleimido peptides; second, peptide and oligonucleotide were prepared stepwise on the same support, yielding oligonucleotide-3'-peptide conjugates. This second approach was thoroughly studied. Using amino acids and small peptides as model compounds, some side reactions were analyzed, detected, and minimized. Oligonucleotides complementary to Ha-ras gene and carrying nuclear localization peptides at the 3' and 5' ends were prepared. Melting temperature studies showed that duplexes containing nuclear localization peptides were more stable than duplexes with unmodified oligonucleotides. Moreover, oligonucleotide-peptide conjugates maintain a good mismatch discrimination when they bind to their target RNA.     

Synthesis and properties of oligonucleotides containing 8-bromo-2'-deoxyguanosine

The preparation of oligonucleotides containing 8-bromo-2'-deoxyguanosine is described. Substitution of G by 8-bromoguanine on an alternating CG decamer stabilizes the Z-form in such a way that the B-form was not observed. Melting temperatures showed that duplexes in which 8-bromo-2'-deoxyguanosine paired with natural bases were much less stable.     

Synthesis and properties of oligonucleotides involving a perylene unit linked to a 2'-deoxyribose residue

We report here the synthesis and binding properties of oligonucleotides involving a perylene unit linked to the anomeric position of a 2'-deoxyribose residue. Both anomers were separated and incorporated separately at either the 5'-end or the internal position of a pyrimidine sequence. In any case the presence of the perylene unit stabilizes the complexes formed with either the single or the double-stranded target.     

Synthesis and triplex-forming ability of oligonucleotides bearing 1-substituted 1H-1,2,3-triazole nucleobases

Using the copper(I)-catalyzed alkyne-azide 1,3-dipolar cycloaddition, a post-elongation modification of 1-ethynyl substituted nucleobases has been employed to construct 18 variations of oligonucleotides from a common oligonucleotide precursor. The triplex-forming ability of each oligonucleotide with dsDNA was evaluated by the UV melting experiment. It was found that triazole nucleobases generally tend to exhibit binding affinities in the following order: CG>TA>AT, GC base pairs. Among the triazole nucleobases examined, a 1-(4-ureidophenyl)triazole provided the best result with regard to affinity and selectivity for the CG base pair.