Double-stranded hybrid

In addition to conventional applications in conducting polymers and electrooptical devices, a number of recent novel applications have emerged. Switching of DNA electron transfer upon single-strand/double-strand hybridization fonns the basis for a new medical biosensor teclmology. Since the number of base pairs of length 20... 

A third alternative starts with an extract of RNA, not DNA. Mature eukaryotic mRNA contains a long run or tail of adenine residues at its 3 end. The poly(rA) tail can be hybridized with an oligomer of thymine residues, and the oligo(dT) can then be used as a primer for a particular kind of DNA polymerase known as reverse transcriptase. This enzyme, a polymerase associated with retroviruses, will use RNA as a template to make a complementary DNA copy of the RNA, creating a DNA-RNA double-stranded hybrid. In another round of synthesis, the enzyme can replace the RNA strand entirely with DNA, so that the RNA-DNA hybrid is completely converted to double-stranded DNA containing an exact copy of the original RNA sequence. This DNA molecule is known as cDNA because it has a strand that is complementary to (or a copy of) the original RNA. 

SI Nuclease Method. Sutton25 and Crosa et al.26 demonstrated that DNA hybridization mixtures could be freed of single-stranded DNA by hydrolysis with SI endonuclease. Double-stranded hybrids are then removed from the reaction mix by precipitation with trichloroacetic acid (TCA) or by collection on Whatman (Clifton, NJ) DE-81 filters.27... 

The second major category of nucleic acid discrimination techniques is hybridization. All hybridization assays are based on the ability of single-stranded nucleic acids to form specific double-stranded hybrids. The process requires (1)... 

Fig. 6. (continued) incubated with the probe-modified electrode (B2), hybridization takes place between the complementary strands resulting in the formation of a hybrid-modified electrode (B3), Hoechst 33258, is incubated with the hybrid-modified-electrode (B4), since Hoechst 33258 intercalates into the double-stranded hybrids on the surface, a high electrochemical current response is obtained (B5). The peak current intensity at the peak potential (—0.6V) is recorded relative to the background response of the blank buffer solution (dashed grey line). 

Heteroduplex A double-strand hybrid of complementary nucleic acid DNA DNA heteroduplexes are formed during recombination. 

Single strands of DNA will associate with single-stranded RNA, if their base sequences are complimentary, to give double-stranded hybrid molecules. This has analytical applications (Chapter 14.3). 

The DNA-based dienes formed highly active catalysts, and no difference in activity was observed between single- and double-stranded hybrid catalysts. Thus, DNA and its numerous functional groups do not interfere with the metal ion coordination. The stability of the catalyst under these conditions is remarkable up to 4600 turnovers were observed. 

The different thermodynamic stabilities of fully matched and partially matched double-stranded hybridized DNA were utilized to detect mismatches in the analyzed DNA, by controlling the hybridization temperature [50], The 30-base primer (36) was covalently linked to apolyacrylamide-acrylhydrazide and 1-vinylimida-... 

It may be noted that the anti-poly A poly U antibodies react very well with reovirus RNA and to a lesser degree with the double-stranded hybrid from denatured bacteriophage T 4 DNA and RNA induced by this bacteriophage (Stollar, 1970). Variation of the specificity of anti-poly A poly U antibodies obtained in different laboratories with respect to RNA from... 

Fig. 1. Southern blot analysis of DNA showing (a) step 1, an agarose gel containing separated restriction fragments of DNA, denoted by (—), which is immersed in NaOH to denature the double-stranded stmcture of DNA, and then transferred by capillary flow to a nitrocellulose filter. In step 2, the bound DNA is allowed to hybridize to a labeled nucleic acid probe, and the unbound probe is washed off In step 3, the filter is placed into contact with x-ray film resulting in (b) bands of exposure on the film which are detected after development and correspond to regions where the restriction fragment is...

Belotserkovskii B.P., Zarling D.A. Peptide nucleic acid (PNA) facilitates multistranded hybrid formation between linear double-stranded DNA targets and RecA protein-coated complementary single-stranded DNA probes. Biochemistry 2002 41 3686-3692. 

After hybridization and washing, the samples were stained with DAPI (4, 6-di-amidino-2-phenylindole), which apparently associates in the minor groove of double-stranded DNA (Kapuscinski 1990). DAPI from Sigma was used. Binding of DAPI to double-stranded DNA occurs with about a 20-fold fluorescence enhancement, which usually does not occur with single-stranded DNA (Haugland 1992). 

Excess Electron Transfer in DNA PNA Hybrid Double Strands. . 200... 

Incorporation of an artificial flavin nucleobase and of a cyclobutane pyrimidine dimer building block into DNA DNA double strands, DNArPNA hybrid duplexes, and DNA-hairpins, provided compelling evidence that an excess electron can hop through DNA to initiate dimer repair even at a remote site. The maximum excess electron transfer distance realised so far in these defined Donor-DNA-Acceptor systems is 24 A. New experiments are now in progress to clarify whether even larger transfer distances can be achieved. 

The latter is an interesting example of self-organizing chiral dendrimers. The construction of the dendrimer is based on the natural property of nucleic acids to recognize and specifically bind to complementary sequences. Pairwise hybridization of two designed DNA strands results in the formation of large monomers which have four single stranded arms and a double stranded waist (24, Fig. 12). 

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