Guanine structure

Chemical Name 2-Amino-1,9-dihvdro-9-[(2-hvdroxvethoxv)methvl] -6H-purin-6-one Common Name Acycloguanosine 9-(2-hvdroxvethoxvmethvl)guanine Structural Formula ... 

Figure 11-8. Structures of representative conical intersections Sj/Sq in the purine bases, 9H-adenine and 9H-guanine. Adenine structures (a,b) are taken from Ref. [138]. Guanine structure (c) is taken from Ref. [171]...

Common Name Acycloguanosine 9-(2-Hydroxyethoxymethyl)guanine Structural Formula ... 

Write a resonance form for guanine in which the six membered ring has an electronic structure analogous to benzene Show all unshared pairs... 

The structure of guanine illustrates an important feature of substituted pyrimidines and purines Oxygen substitution on the ring favors the keto form rather than the enol Ammo substitution does not... 

Pai, E.F., et al. Structure of the guanine-nucleotide-binding domain of the Ha-ras oncogene product p21 in the triphosphate conformation. Nature 341 209-214,... 

Another property of pyrimidines and purines is their strong absorbance of ultraviolet (UV) light, which is also a consequence of the aromaticity of their heterocyclic ring structures. Figure 11.8 shows characteristic absorption spectra of several of the common bases of nucleic acids—adenine, uracil, cytosine, and guanine—in their nucleotide forms AMP, UMP, CMP, and GMP (see Section 11.4). This property is particularly useful in quantitative and qualitative analysis of nucleotides and nucleic acids. 

DNA is made up ot two intertwined strands. A sugar-phosphate chain makes up the backbone of each, and the two strands are joined by way of hydrogen bonds betwen parrs of nucleotide bases, adenine, thymine, guanine and cytosine. Adenine may only pair with thymine and guanine with cytosine. The molecule adopts a helical structure (actually, a double helical stnrcture or double helix ). 

After inconclusive early work,-" structure 218 was demonstrated for adenine hydrochloride using X-ray diffraction (cf. also reference 256) and was later supported by nuclear magnetic resonance evidence. Four possible structures have been advanced for guanine... 

MP2/6-31G calculations were performed for bonded and stacked structures of adenine-2,4-difluorotoluene complexes 152 [99CPL393] and for adenine with guanine or thymine [97JPC(B)3846]. Classical base pair structures of 152... 

The secondary structure of DNA is shown in Figure B. This "double helix" model was first proposed in 1953 by James Watson and Francis Crick, who used the x-ray crystallographic data of Rosalind Franklin and Maurice Wilkins. Beyond that, they were intrigued by the results of analyses that showed that in DNA the ratio of adenine to thymine molecules is almost exactly 1 1, as is the ratio of cytosine to guanine ... 

The different possible adducts formed between mitomycin C and DNA have been isolated by degradation of DNA after in vitro alkylation/crosslinking reactions and structurally characterized. Monoadduct 21 (Scheme 11.3), derived from alkylation at C-l only [53], and monoadducts 22 [54] and 23 [55, 56] (derived from C-10 alkylation by 16 at N-7 or N-2 of guanine, respectively) have been isolated, together with bisadducts 24 [57] and 25 [58], derived from interstrand and intrastrand crosslinks, respectively, and adduct 26 [59], formed by addition of a molecule of water to C-10 instead of the second guanine. All of these adducts have also been isolated from DNA after in vivo crosslinking [60, 61]. 

Saito et al. achieved the first direct confirmation of double alkylation of purine bases by azinomycin B [140]. They incubated azinomycin B with the self-comple-mentary DNA duplex d(TAGCTA)2 and monitored the reaction by HPLC and ion spray MS. They observed initial formation of a monoadduct that was then converted into a crosslinked bisadduct. The crosslink position was identified as between the guanine of one strand and the 5 -adenine on the other strand by thermo-lytic depurination. Further decomposition prevented structural analysis of the azi-... 

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