DNA, base pairing

The DNA base pairs guanine (G), cytosine (C), adenine (A) and thymine (T). The uracil-2,6-diaminopyridine pair can also form three hydrogen bonds but has a much lower association constant than G-C. 

Thirty-four sets of data on D2S44 were sent to NIST. Nineteen laboratories also reported results on D4S139 (PH30), 17 tested D10S28, 16 laboratories examined D1S7 (MSi), and 12 provided results on D17S79 (Vi). The certified values (number of DNA base pairs) for SRM 2390 are shown on the NIST SRM 2390 Certificate. 

DNA mismatch repair genes Genes that identify and correct errors in DNA base pairs during DNA replication. Mutations in the mismatch repair genes can lead to cancer by allowing abnormal cells to continue to grow. 

Extended solid state n systems facilitate CT, particularly when doped [4-6]. The analogy between DNA and conductive solid state -stacks therefore establishes that a requisite condition for CT may exist in DNA. DNA contains an array of heterocyclic aromatic base pairs, stacked at a distance of 3.4 A, wrapped within a negatively charged sugar phosphate backbone [7] (Fig. 1). The interactions between the n electrons of the DNA base pairs provide the electronic coupling necessary for CT to occur. 

The analogy drawn between -stacked solids and duplex DNA has provided a useful starting point for experiments to probe and understand DNA-medi-ated CT. As with the -stacked solids, the DNA base pair array can provide an effective medium for long range CT. Mechanistically, however, the differences between DNA and these solid state materials may be even more important to consider. Duplex DNA, as a molecular -stacked structure, undergoes dynamical motion in solution. The time-dependent and sequence-dependent structures that arise serve to modulate and gate CT. Indeed in probing DNA CT as a function of sequence and sequence-dependent structure, we may better understand mechanistically how CT proceeds and how DNA CT may be utilized. 

DNA-mediated charge transport has been a hot topic in chemistry for the last decade. Studies of DNA-mediated guanine radical cation (hole) transport are often focused on the efficiency of the transport between two guanines separated by a large distance, through the /r-stack of DNA base pairs [1-14]. The efficiency of the hole transport could be easily determined if one knew the distance between the hole donor and acceptor, the relative number of holes that reach the acceptor, and the time required for the transport. 

Jasien, P. G., and G. Fitzgerald. 1990. Molecular dipole moments and polarizabilities from local density functional calculations Applications to DNA base pairs. J. Chem. Phys. 93, 2554. 

Figure 1.2 Watson-Crick DNA base pairs and the DNA backbone...

DNA base pairs The general structure of the information-bearing molecule used in biology on Earth... 

Intercalating agents are hydrophobic, planar structures that can fit between the DNA base pairs in the center of the DNA double helix. These compounds (ethidium bromide and actinomycin D are often-used examples) take up space in the helix and cause the helix to unwind a little bit by increasing the pitch. The pitch is a measure of the distance between successive base pairs. 

In DNA, base pairing occurs between guanine and cytosine in its most stable form [87], as in [92]. However, cytosine in its imino form [91] is able to form a hydrogen bond to adenine as in [93], and such a base pairing could lead to the formation of mutations if it continued in DNA replication. The kinetics of the tautomerisation of purine and pyrimidine bases has been... 

Such activity enhancement can be ascribed to planarity of the naphthalene nucleus and its disposition for n-n stacking between the DNA base pairs. There is no literature precedence for involvement of naphthalene in such processes unless it is % electron deficient.211,212 However, our results suggest that both alkylated and acylated naphthalenes are intercalators with bacterial DNA. 

Figure 26. Schematic of the mediation of ET by a jt-stack of aromatic rings, such as the base pairs of duplex DNA. The D and A groups associated with the DNA molecule may be covalently linked to the helix, they may be intercalators, or they may be DNA base pairs.

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