Guanine-cytosine

A,G,CT, (U) Adenine, guanine, cytosine, thymine - the four bases present in DNA. Urac replaces thymine in RNA... 

Source Guanine Cytosine Thymine Cytosine Pyrimidines... 

Examine AT pair and GC pair, adenine-thymine and guanine-cytosine base pairs, respectively. Identify the hydrogen bonds in each. Are they the same as those you sketched Are the base pairs flat as normally drawn in textbooks, or are they significantly puckered or twisted ... 

It has been shown that photoexcitation of the guanine-cytosine (G-C) base pair leads to proton transfer [231], Watson-Crick (WC) base pairs have excited state lifetimes much shorter than other non-WC base pairs indicating once again that the natural occurring WC base pairs are more photostable than other alternative configurations [115, 118, 232-235], Much work has been done in the gas phase where many different base pair isomers exist. The ultrafast relaxation of the WC base pair has also been confirmed in solution using fluorescence up-conversion measurements [117]. 

Abo-Riziq A, Grace L, Nir E, Kabelac M, Hobza P, de Vries MS (2005) Photochemical selectivity in guanine-cytosine base-pair structures. Proc Natl Acad Sci USA 102 20-23... 

Sobolewski AL, Domcke W, Hattig C (2005) Tautomeric selectivity of the excited-state lifetime of guanine/cytosine base pairs The role of electron-driven proton-transfer processes. Proc Natl Acad Sci USA 102 17903-17906... 

Sobolewski AL, Domcke W (2004) Ab initio studies on the photophysics of the guanine-cytosine base pair. Phys Chem Chem Phys 6 2763... 

Markwick PRL, Doltsinis NL (2007) Ultrafast repair of irradiated DNA nonadiabatic ab initio simulations of the guanine-cytosine photocycle. J Chem Phys 126 175102... 

Miannay F-A, Banyasz A, Gustavsson T, Markovitsi D (2007) Ultrafast excited-state deactivation and energy transfer in guanine-cytosine DNA double helices. J Am Chem Soc 129 14574-14575... 

Sarai, A., and M. Saito. 1985. Theoretical Studies on the Interaction of Proteins with Base Paris. II. Effect of External H-Bond Interactions on the Stability of Guanine-Cytosine and Non-Watson-Crick Pairs. Int. J. Quantum Chem. 28, 399-409. 

These definitions apply to any atomic system, molecule or crystal. Fig. 7.3 a illustrates their application to the charge distribution of the guanine-cytosine base-pair. Fig. 7.3 b shows the molecular structure defined by the bond paths and the associated CPs that clearly and uniquely define the three hydrogen bonds that link the two bases. Fig. 7.3 c shows the atomic boundaries and bond paths overlaid on the electron density in the plane of the nuclei. All properties of the atoms can be determined, enabling one, for example, to determine separately the energy of formation of each of the three hydrogen bonds. 

Guanine-Cytosine Base-Pair Interacting with Metal Cations... 

Attention should be given to the selection of primers. Typically, primers used are between 15 and 30 bases in length, with guanine-cytosine composition between 40 and 60%. The primer should not have within its sequence any unusual composition such as stretches of polypurines or polypyrimidines. The primer pair should not be complementary at the 3 ends, since otherwise the DNA synthesizing enzyme can extend one primer over the other primer, creating a double-stranded product whose length approximates the sum of the two primers. This artifact is called primer dimer, which could very well become the predominant and undesirable PCR product when primer pairs complementary at the 3 ends are used (B4, N3). 

Like all bacteria, actinomycetes are prokaryotic microorganisms. In addition, the adenine-thymine and guanine-cytosine contents of bacteria and actinomycetes are similar, as are the cell wall constituents of both types of microorganisms. Actinomycetes filaments are also about the same size as those of bacteria. 

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