Guanine Group

Figure 29. Docking of an alkylated base into Z-DNA and torsion of the PAH group, (a, b) Two views of the alkylated base (as determined by X-ray diffraction techniques) docked onto the syn-guanine group in Z-DNA. (c, d) Two views of the same modelling experiment with a torsional rotation of 180 about C6-N6. Note how the curvature of the PAH group conforms to that of the helix. This is a model of the carcinogen lying in a groove of DNA.

Figure 2.5 The cisplatin reactive group can covalently couple to methionine-, cysteine-, and histidine-containing peptides or proteins. It also reacts with guanine groups to form a covalent modification on the N7 nitrogen.

Capping. Covalent modification involving the addition of a modified guanine group in a 5 -5" linkage. It occurs only in eukaryotes, primarily on mRNA molecules. 

Alternatively, the drug could link two guanine groups on the same chain such that the drug is attached like a limpet to the side of the DNA helix. Such an attachment would mask that portion of DNA and block access to the necessary enzymes required for DNA function. 

Jones, J. B., and J. M. Young Carcinogenicity of Lactones. IV. Alkylation of Analogues of DNA Guanine Groups such as Imidazole, N-Methylimidazole, and Guanosine by a,p-Unsaturated Acids. Canad. J. Chem. 48, 1567 (1970). 

Many protective groups have been developed for the amino group, including carbamates (>NCO,R), used for the protection of ammo acids in peptide and protein syntheses, and amides (>NCOR). used more widely in syntheses of alkaloids and for the protection of the nitrogen bases adenine, cytosine, and guanine in nucleo-... 

The steps involved in automated oligonucleotide synthesis illustrate the current use of protective groups in phosphate chemistry (Scheme 1). Oligonucleotide synthesis involves the protection and deprotection of the 5 -OH, the amino groups on adenine, guanine, and cytosine, and -OH groups on phosphorus. 

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