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P A Giannaris

Publications and source records attributed to P A Giannaris.

5 recordsLinked to original sources
PubMed1994

Antisense L/D-oligodeoxynucleotide chimeras: nuclease stability, base-pairing properties, and activity at directing ribonuclease H.

Ultraviolet thermal denaturation studies substantiate our earlier hypothesis that substitution of a L-nucleotide residue for a D-nucleotide within a DNA duplex permits a stable structure in which all bases are paired through Watson-Crick hydrogen bonds (Damha, M. J., Giannaris, P. A., Marfey, P., & Reid, L. S. (1991) Tetrahedron Lett. 32, 2573-2576). This conclusion is also evident from the NMR work of Blommers et al. [Blommers, M. J. J., et al. (1994) Biochemistry (following paper in this issue)]. Our thermal denaturation studies indicate that, while weakening the interaction with target DNA and RNA, these substitutions allow for excellent cooperative binding. When the target is single-stranded DNA, the melting temperature of the complex is lowered by 4-5 degrees C per L-dU incorporation and by 0.4-2.6 degrees C when an internal D-dC is replaced by L-dC (1 M NaCl). When the target is RNA, the depression of Tm is also greater for L-dU substitutions (5-8 degrees C) than for L-dC substitutions (2-4 degrees C). The depressions of Tm caused by introducing A/C and G/T mismatches at the same positions were significantly greater. L/D-DNA chimeras were found to activate RNase H cleavage when hybridized to RNA. Furthermore, the stability of chimeric L/D-DNA against degradation by various commercial phosphodiesterases was found to be significant, as was their stability against digestion in human serum. These experiments establish that L/D-DNA chimeras serve as excellent models of antisense oligonucleotides.

Base Sequence↗
PubMed1993

Oligoribonucleotides containing 2',5'-phosphodiester linkages exhibit binding selectivity for 3',5'-RNA over 3',5'-ssDNA.

Oligoribonucleotides containing 2',5'-phosphodiester linkages have been synthesized on a solid support by the 'silyl-phosphoramidite' method. The stability of complexes formed between these oligonucleotides and complementary 3',5'-RNA strands have been studied using oligoadenylates and a variety of oligonucleotides of mixed base sequences including phosphorothioate backbones. In many cases, particularly for 2',5'-linked adenylates, the UV melting profiles are quite sharp and exhibit large hyperchromic changes. Substituting a few 3',5'-linkages with the 2',5'-linkage within an oligomer lowers the Tm of the complex and the degree of destabilization depends on the neighboring residues and neighboring linkages. The 2',5'-linked oligoribonucleotides prepared in this study exhibited remarkable selectivity for complementary single stranded RNA over DNA. For example, in 0.01 M phosphate buffer--0.10 M NaCl (pH 7.0), no association was observed between 2',5'-r(CCC UCU CCC UUC U) and its Watson-Crick DNA complement 3',5'-d(AGAAGGGAGAGGG). However, 2',5'-r(CCC UCU CCC UUC U) with its RNA complement 3',5'-r(AGAAGGGAGAGGG) forms a duplex which melts at 40 degrees C. The decamer 2',5'-r(Ap)9A forms a complex with both poly dT and poly rU but the complex [2',5'-r(Ap)9A]:[poly dT] is unstable (Tm, -1 degree C) and is seen only at high salt concentrations. In view of their unnatural character and remarkable selectivity for single stranded RNA, 2',5'-oligo-RNAs and their derivatives may find use as selective inhibitors of viral mRNA translation, and as affinity ligands for the purification of cellular RNA.

Base Sequence↗
PubMed1993

Solid-phase synthesis and hybridization properties of DNA containing sulfide-linked dinucleosides.

Oligodeoxyribonucleotides incorporating non-hydrolyzable dialkyl sulfide linked thymidine dimers (TsT) were synthesized chemically by the solid-phase approach. The sulfide dimer TsT was stable to degradation by snake-venom phosphodiesterase, calf spleen phosphodiesterase, Nuclease P1 and Nuclease S1. Thermal denaturation analysis indicated that the incorporation of TsT dimers into DNA weakened, but did not prevent, binding to complementary DNA and RNA over a wide range of salt concentrations (10 mM to 2 M NaCl).

Base Sequence↗
PubMed1990

An improved procedure for derivatization of controlled-pore glass beads for solid-phase oligonucleotide synthesis.

A simplified and economical method for the attachment of 2'-deoxyribo, ribo and arabinonucleosides onto long-chain alkylamidopropanoic acid controlled-pore glass (LCAAP-CPG, P-3) is described. In this procedure, 5'-O-tritylated nucleosides are coupled directly to LCAAP-CPG in excellent yields using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (DEC) as coupling reagent. The conventional and time-consuming preparation of nucleoside-3'-O-succinates is no longer required.

Acetic Anhydrides↗