Watson-Crick base-pair, hydrogen bonding

RNA and DNA are held together by the conventional Watson-Crick base pairing hydrogen bonding rules. There is no covalent bond. 

Pervushin, K., Ono, A., Fernandez, C., Szyperski, T., Kainosho, M., and Wiithrich, K. 1998. NMR scalar couplings across Watson-Crick base pair hydrogen bonds in DNA observed by transverse relaxation optimized spectroscopy. Proc. Nat. Acad. Sci. USA 95 14147-14151. 

Watson-Crick base pair Hydrogen bond partners in RNA or DNA. Adenine is the Watson-Crick partner to uracil (or thymine in DNA) guanine pairs with cytosine. 

This is consistent with there not being enough space (20 °) for two purines to fit within the helix and too much space for two pyrimidines to get close enough to each other to form hydrogen bonds between them. These relationships are often called the rules of Watson-Crick base pairing. 

Fig. 3.2 Pairing rules for polyamide recognition of all four Watson—Crick base pairs of DNA. Putative hydrogen bonds are shown as dashed lines. Circles with dots represent lone pairs of N(3) of purines and 0(2) of pyrimi-...

The DNA double heUx illustrates the contribution of multiple forces to the structure of biomolecules. While each individual DNA strand is held together by covalent bonds, the two strands of the helix are held together exclusively by noncovalent interactions. These noncovalent interactions include hydrogen bonds between nucleotide bases (Watson-Crick base pairing) and van der Waals interactions between the stacked purine and pyrimidine bases. The hehx presents the charged phosphate groups and polar ribose sugars of... 

In molecular biology, a set of two hydrogen-bonded nucleotides on opposite complementary nucleic acid strands is called a base pair. In the classical Watson-Crick base pairing in DNA, adenine (A) always forms a base pair with thymine (T) and guanine (G) always forms a base pair with cytosine (C). In RNA, thymine is replaced by uracil (U). 

The hydrogen bond length in Watson-Crick base pairs can be characterized using the recently developed method of measuring the cross-correlated relaxation [61] between H chemical shift anisotropy and dipole-dipole coupling of H and its hydrogen bond donor... 

Figure 20.4 The bases present in RNA and DNA and the Watson-Crick base pairing relationships. Uracil is present in RNA but is replaced by thymine in DNA that is, the pairs C-G and T-A are found in DNA the pairs C-G but U-A are found in RNA. The pairing is brought about by hydrogen bonding, indicated by a broken line.

Scheme 2 Rearrangement of hydrogen bonding induced by hole localization at the G-C Watson-Crick base pair, a Proton shift from the G radical cation to cytosine, b Dissociation of the N2 hydrogen bond in the G radical cation (adapted from [9] and [48])...

Nucleotide Structure Which positions in a purine ring of a purine nucleotide in DNA have the potential to form hydrogen bonds but are not involved in Watson-Crick base pairing ... 

Figure 5-6 Outlines of the purine and pyrimidine bases of nucleic acids showing van der Waals contact surfaces and some of the possible directions in which hydrogen bonds may be formed. Large arrows indicate the hydrogen bonds present in the Watson-Crick base pairs. Smaller arrows indicate other hydrogen bonding possibilities. The directions of the green arrows are from a suitable hydrogen atom in the base toward an electron pair that serves as a hydrogen acceptor. This direction is opposite to that in the first edition of this book to reflect current usage.

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