Nucleosides & nucleotides最新文献

The interactions of natural and synthetic polynucleotide double strands with the antitumor agent paclitaxel and the oncological product "Taxol for Injection Concentrate" (abbreviated as taxol) were examined in diluted aqueous solutions by thermal denaturation profiles (Tm), CD spectra and UV-absorption measurements. Furthermore, DNA-paclitaxel and -taxol complexes in condensed nucleic acid solutions were studied by differential scanning calorimetry. As polynucleotides alternating and homologous poly[d(AT)] and poly[d(GC)] and calf thymus DNA were used. The results point to stabilizing interactions of paclitaxel to AT nucleotides, whereas in the presence of GC base pairings no interaction took place. Thereby the interaction to homologous (dA).(dT)-tracts seems to be preferred.

Geminal difluorocyclopropane analogues of nucleosides 7a-7e were synthesized. Compounds 7a and 7c-7e were obtained by alkylation of nucleic acid bases or their appropriate precursors with (cis)-1-benzyloxymethyl-2-bromomethyl-3,3-difluorocyclopropane+ ++ (8). Analogue 7b was prepared by hydrolysis of 2-amino-6-chloropurine derivative 7e. Compounds 7a-7d did not exhibit any antiviral activity against HCMV, HSV-1, HSV-2, EBV, VZV, HBV and HIV-1 or antitumor effects against murine leukemia L1210, mouse tumors PO3 or C38 and human tumor H15.

Purine carbanucleosides built on a 6-oxabicyclo[3.1.0]hexane template were synthesized from readily available 2-cyclopentenone employing a Mitsunobu reaction to incorporate the base onto the carbocyclic ring. Both adenosine and guanosine analogues exhibited moderate antiviral activity.

A method for the introduction of depurinated lesions in DNA is described, and is based on the formation of a covalent cross-link between an antisense oligonucleotide probe and the target DNA sequence followed by an unexpectedly mild thermal depurination.

The two ribo-configured nucleosides 1-(3-C-allyl-2-O-methyl-beta-D-ribo-pentofuranosyl)thymine 3 and (1S,5R,6R,8R)-5-hydroxy-6-(hydroxymethyl)-1-methoxy-8-(thymin-1-yl )- 2,7-dioxabicyclo[3.3.0]octane 6 have been transformed into their corresponding phosphoramidites, 5 and 8 respectively, and used as building blocks for the synthesis of modified oligonucleotides. The oligonucleotides were shown to hybridize with decreased binding affinity towards complementary single stranded DNA and RNA.

The carbocyclic analogs of CMP, UMP, GMP, IMP, and ribo-TMP, of the same absolute configuration as the naturally occurring beta-D-ribofuranose-based ribonucleoside monophosphates, have been synthesized. The synthetic route employed Mitsunobu coupling of the heterocycles, appropriately protected where necessary, with a differentially protected, chiral carbocyclic core.

The synthesis of a homologues series of compounds related to (R, S)-isodideoxynucleosides has been completed by coupling a variety of natural purine and pyrimidine bases with a modified sugar intermediate. This sugar precursor was prepared regiospecifically and stereospecifically from D-glucose.

A region of c-myc mRNA was identified which permitted very efficient antisense effects to be achieved in living cells using chimeric methylphosphonate--phosphodiester antisense effectors. Novel inosine--containing ribozymes (which cleave after NCH triplets) were directed to an ACA triplet within this region and delivered into living cells. No ribozyme intracellular activity could be identified. Very low ribozyme function was also observed in in vitro assays using a 1700nt substrate RNA.

The endonuclease from Serratia marcescens is a non-specific enzyme that cleaves single and double stranded RNA and DNA. It accepts a phosphorylated pentanucleotide as a minimal substrate which is cleaved in the presence of Mg2+ at the second phosphodiester linkage. The present study is aimed at understanding the role of electrostatic and hydrogen bond interactions in phosphodiester hydrolysis. Towards this objective, six pentadeoxyadenylates with single stereoregular methylphosphonate substitution within this minimal substrate (2a-4b) were synthesized following a protocol described here. These modified oligonucleotides were used as substrates for the Serratia nuclease. The enzyme interaction studies revealed that the enzyme failed to hydrolyze any of the methylphosphonate analogues suggesting the importance of negative charge and/or hydrogen bond acceptors in binding and cleavage of its substrate. Based on these results and available site-directed mutagenesis as well as structural data, a model for nucleic acid binding by Serratia nuclease is proposed.

The influence of the secondary structure of oligonucleotides having a natural phosphodiester backbone on their ability to interact with DNA and RNA targets and on their resistance to the nucleolytic digestion is investigated. Oligonucleotides having hairpin, looped and snail-like structure are found to be much more stable to nuclease degradation in different biological media and inside cells than the linear ones. The structured oligonucleotides can also hybridise with their DNA and RNA targets.