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Modulation of Pyrene Fluorescence in DNA Probes Depends upon the Nature of the Conformationally Restricted Nucleotide
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Bioorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Bioorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Bioorganic Chemistry.
2008 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, Vol. 73, no 7, 2829-2842 p.Article in journal (Refereed) Published
Abstract [en]

The DNA probes (ODNs) containing a 2'-N-(pyren-1-yl)-group on the conformationally locked nucleosides [2'-N-(pyren-1-yl)carbonyl-azetidine thymidine, Aze-pyr (X), and 2'-N-(pyren-1-yl)carbonyl-aza-ENA thymidine, Aza-ENA-pyr (Y)], show that they can bind to complementary RNA more strongly than to the DNA. The Aze-pyr (X) containing ODNs with the complementary DNA and RNA duplexes showed an increase in the fluorescence intensity (measured at lambda em approximately 376 nm) depending upon the nearest neighbor at the 3'-end to X [dA ( approximately 12-20-fold) > dG ( approximately 9-20-fold) > dT ( approximately 2.5-20-fold) > dC ( approximately 6-13-fold)]. They give high fluorescence quantum yields (Phi F = 0.13-0.89) as compared to those of the single-stranded ODNs. The Aza-ENA-pyr (Y)-modified ODNs, on the other hand, showed an enhancement of the fluorescence intensity only with the complementary DNA (1.4-3.9-fold, Phi F = 0.16-0.47); a very small increase in fluorescence is also observed with the complementary RNA (1.1-1.7-fold, Phi F = 0.17-0.22), depending both upon the site of the Y modification introduced as well as on the chemical nature of the nucleobase adjacent to the modification site into the ODN. The fluorescence properties, thermal denaturation experiments, absorption, and circular dichroism (CD) studies with the X- and Y-modified ODNs in the form of matched homo- and heteroduplexes consistently suggested (i) that the orientation of the pyrene moiety is outside the helix of the nucleic acid duplexes containing a dT-d/rA base pair at the 3'-end of the modification site for both X and Y types of modifications, and (ii) that the microenvironment around the pyrene moiety in the ODN/DNA and ODN/RNA duplexes is dictated by the chemical nature of the conformational constraint in the sugar moiety, as well as by the nature of neighboring nucleobases. The pyrene fluorescence emission in both X and Y types of the conformationally restricted nucleotides is found to be sensitive to a mismatched base present in the target RNA: (i) The X-modified ODN showed a decrease ( approximately 37-fold) in the fluorescence intensity (measured at lambda em approximately 376 nm) upon duplex formation with RNA containing a G nucleobase mismatch (dT-rG pair instead of dT-rA) opposite to the modification site. (ii) In contrast, the Y-modified ODN in the heteroduplex resulted in a approximately 3-fold increase in the fluorescence intensity upon dT-rG mismatch, instead of matched dT-rA pair, in the RNA strand. Our data corroborate that the pyrene moiety is intercalated in the X-modified mismatched ODN/RNA (G mismatch) heteroduplex as compared to that of the Y-modified ODN/RNA (G mismatch) heteroduplex, in which it is located outside the helix.

Place, publisher, year, edition, pages
2008. Vol. 73, no 7, 2829-2842 p.
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:uu:diva-97302DOI: 10.1021/jo702747wISI: 000254544800043PubMedID: 18331060OAI: oai:DiVA.org:uu-97302DiVA: diva2:172174
Available from: 2008-05-14 Created: 2008-05-14 Last updated: 2009-11-12Bibliographically approved
In thesis
1. Conformationally Constrained Nucleosides, Nucleotides and Oligonucleotides: Design, Synthesis and Properties
Open this publication in new window or tab >>Conformationally Constrained Nucleosides, Nucleotides and Oligonucleotides: Design, Synthesis and Properties
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is based on six original research publications describing synthesis, structure and physicochemical and biochemical analysis of chemically modified oligonucleotides (ONs) in terms of their potential diagnostic and therapeutic applications. Synthesis of two types of bicyclic conformationally constrained nucleosides, North-East locked 1',2'-azetidine and North locked 2',4'-aza-ENA, is described. Study of the molecular structures and dynamics of bicyclic nucleosides showed that depending upon the type of fused system they fall into two distinct categories with their respective internal dynamics and type of sugar conformation. The physicochemical properties of the nucleobases in the conformationally constrained nucleosides found to be depended on the site and ring-size of the fused system.

The incorporation of azetidine modified nucleotide units into 15mer ONs lowered the affinity toward the complementary RNA. However, they performed better than previously reported isosequential 1',2'-oxetane modified analogues. Whereas aza-ENA-T modification incorporated into ONs significantly enhanced affinity to the complementary RNA. To evaluate the antisense potential of azetidine-T and aza-ENA-T modified ONs, they were subjected to RNase H promoted cleavage as well as tested towards nucleolytic degradation. Kinetic experiments showed that modified ONs recruit RNase H, however with lower enzyme efficiency due to decreased enzyme-substrate binding affinity, but with enhanced turnover number. Both, azetidine-T and aza-ENA-T modified ONs demonstrated improved 3'-exonuclease stability in the presence of snake venom phosphodiesterase and human serum compared to the unmodified sequence.

Oligodeoxynucleotides (ODNs) containing pyrene-functionalized azetidine-T (Aze-pyr X) and aza-ENA-T (Aza-ENA-pyr Y) modifications showed different fluorescence properties. The X modified ODNs hybridized to the complementary DNA and RNA showed variable increase in the fluorescence intensity depending upon the nearest-neighbor at the 3'-end to X modification (dA > dG > dT > dC) with high fluorescence quantum yield. However, the Y modified ODNs showed a sensible enhancement of the fluorescence intensity only with complementary DNA. Also, the X modified ODN showed decrease (~37-fold) in the fluorescence intensity upon duplex formation with RNA containing a G nucleobase mismatch opposite to the modification site, whereas a ~3-fold increase was observed for the Y modified probe.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 71 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 440
Keyword
Bioorganic chemistry, antisense oligonucleotides, conformationally constrained nucleosides, azetidine, aza-ENA, target affinity, RNase H, exonuclease stability, pyrene-functionalized nucleotides, fluorescence, mismatch discrimination, Bioorganisk kemi
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-8887 (URN)978-91-554-7219-1 (ISBN)
Public defence
2008-06-05, C10:301, BMC, Husargatan 3, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2008-05-14 Created: 2008-05-14 Last updated: 2010-03-03Bibliographically approved

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