why RNA duplex is more stable than DNA duplex?

Question

melting point of former is 10 degree higher than that of latter.

Answer 1

Its form. You have to look at the length of the bonds. With protein, form equals function. The strands are shaped differently, so they function differently, so they have different physical properties including melting point.

Answer 2

I cannot tell you the answer for sure, however you can take solace in the fact that i am quite confident and that i did not copy completely different information from a website then plagerise it.

If i remember correctly, the only real difference between the two is the Uracil instead of thiamine. Uracils structure is obviously different and it forms closer and therefore stronger Hydrogen bonds with the adenine. Also, I don't know if you know this, but in RNA you can get mis-pairing; G can form H-bonds with U and C with A, although this doesn't happen often in DNA.

So that is my answer: The Uracil Hydrogen bonds are stronger than Thiamine

Answer 3

Pyrene is highly emissive when attached to the RNA duplex but not to the DNA duplex: the structural basis of this difference

Answer 4

Antisense RNAs in prokaryotic systems often inhibit translation of mRNAs. In some cases, this involves sequestration of Shine-Dalgarno (SD) sequences and start codons. In other cases, antisense/target RNA duplexes do not overlap these signals, but form upstream. We have performed toeprinting analyses on repA mRNA of plasmid R1, both free and in duplex with the antisense RNA, CopA. An intermolecular RNA duplex 2 nt upstream of the tap SD prevents ribosome binding. An intrastrand stem-loop at this location yields the same inhibition. Thus, stable secondary structures immediately upstream of the tap SD sequence inhibit translation, as shown by toeprinting in vitro and repA-lacZ expression in vivo. Previous work showed that repA (initiator protein) expression requires tap (leader peptide) translation. Toeprinting data confirm that the tap ribosome binding site (RBS) is accessible, whereas the repA RBS, which is sequestered by a stable stem-loop, is weakly recognized by the ribosome. Truncated CopA RNA (CopI) is unable to pair completely with target RNA, but proceeds normally to a kissing intermediate. This mutant RNA species inhibits repA expression in vivo. By a kinetic toeprint inhibition protocol, we have shown that the structure of the kissing complex is sufficient to sterically prevent ribosome binding. These results are discussed in comparison with the effect of RNA structures elsewhere in the ribosome-binding region of an mRNA.

A 5' cap, also termed an RNA cap, an RNA 7-methylguanosine cap or an RNA m7G cap, is a modified guanine nucleotide that has been added to the "front" or 5' end of a eukaryotic messenger RNA shortly after the start of transcription. The 5' cap consists of a terminal 7-methylguanosine residue which is linked through a 5'-5'-triphosphate bond to the first transcribed nucleotide. Its presence is critical for recognition by the ribosome and protection from RNases.

Cap addition is coupled to transcription, and occurs co-transcriptionally, such that each influences the other. Shortly after the start of transcription, the 5' end of the mRNA being synthesized is bound by a cap-synthesizing complex associated with RNA polymerase. This enzymatic complex catalyzes the chemical reactions that are required for mRNA capping. Synthesis proceeds as a multi-step biochemical reaction.

First, the triphosphate at the 5' end of the newly synthesized RNA is cleaved. The enzyme phosphohydrolase cleaves the gamma phosphodiester bonds while leaving the alpha and beta phosphates. Second, the enzyme guanylyltransferase transfers a guanine and its alpha phosphate onto the beta phosphate of the 5' end of the mRNA producing a 5'-5'-triphosphate linkage. Third, the nitrogen-7 (N-7) position of the newly added guanine is methylated (guaninemethylation) by the enzyme guanine-7-methyltransferase. Finally, 2'-O-methyltransferase methylates the 2' position of the ribose sugar. This methyl group provides extra stability to the RNA due to the protection from phosphoester cleavage by nucleophilic attack of the neighbor hydrogen. After the 5' end has been capped, it is released from the cap-synthesizing complex and is subsequently bound by a cap-binding complex associated with RNA polymerase.

Polyadenylation is the covalent linkage of a polyadenylyl moiety to a messenger RNA molecule. In eukaryotic organisms, polyadenylation is the mechanism by which most messenger RNA (mRNA) molecules are terminated at their 3' ends. The poly(A) tail aids in mRNA stability by protecting it from exonucleases. Polyadenylation is also important for transcription termination, export of the mRNA from the nucleus, and translation. Some prokaryotic mRNAs also are polyadenylated, although the poly(A) tail's function is different from that in eukaryotes.

Polyadenylation occurs during and immediately after transcription of DNA into RNA. After transcription has been terminated, the mRNA chain is cleaved through the action of an endonuclease complex associated with RNA polymerase. The cleavage site is characterized by the presence of the base sequence AAUAAA near the cleavage site. After the mRNA has been cleaved, 80 to 250 adenosine residues are added to the free 3' end at the cleavage site. This reaction is catalyzed by polyadenylate polymerase.

We have studied the fate of covalently-closed circular DNA in the temperature range from 95 to 107 degrees C. Supercoiled plasmid was not denatured up to the highest temperature tested. However, it was progressively transformed into open DNA by cleavage and then denatured. Thermodegradation was not dependent on the DNA supercoiling density. In particular, DNA made positively supercoiled by an archaeal reverse gyrase was not more resistant to depurination and thermodegradation than negatively supercoiled DNA. Thermodegradation was similar in aerobic or anaerobic conditions but strongly reduced in the presence of physiological concentrations of K+ or Mg2+. These results indicate that the major problem faced by covalently closed DNA in hyperthermophilic conditions is not thermodenaturation, but thermodegradation, and that intracellular salt concentration is important for stability of DNA primary structure. Our data suggest that reverse gyrase is not directly required to protect DNA against thermodegradation or thermodenaturation.