Adenine structures

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]...

Compounds of non-adenine structure were sought based on the considerations of steric similarities between A -substituted adenine and phenylurea and also between phenylurea, A-arylcarbamates and s-triazine herbicides. Many of the compounds found are known as inhibitors of photosystem 11 electron flow and some also inhibit the cytokinin-stimulated callus growth [36,37]. It has been concluded that phenylureas, s-triazines and V-arylcarbamates share the same place of action, which is the cytokinin receptor localized in chloroplasts [28]. 

Volkov, S.N. Conformational transitions and the mechanism of transmission of long-range effects in DNA. Preprint ITP-88-12E, Kiev (1988) 22 Krumhansl, J.A., Alexander, D.M. Nonlinear dynamics and conformational exitations in biomolecular materials. In Structure and dynamics nucleic acids and proteins. (Clementi, E., Sarma, R.H., eds) Adenine Press, New York (1983) 61-80... 

Firefly lucifenn is an example of an azole that contains a benzene ring fused to the five membered ring Such structures are fairly common Another example is benzimidazole present as a structural unit m vitamin B12 Some compounds related to benzimidazole include purine and its ammo substituted derivative adenine one of the so called het erocychc bases found m DNA and RNA (Chapter 28)... 

FIGURE 15 5 Structure of NAD the oxidized form of the coenzyme nicotinamide adenine dinucleotide The functional part of the coen zyme is framed in red... 

UV photoelectron spectra, 5, 517 Adenine, 8-methyl-synthesis, 5, 570 Adenine, 9-methyl-crystal structure, 5, 509... 

Oxidation of P-nicotinamide adenine dinucleotide (NADH) to NAD+ has attracted much interest from the viewpoint of its role in biosensors reactions. It has been reported that several quinone derivatives and polymerized redox dyes, such as phenoxazine and phenothiazine derivatives, possess catalytic activities for the oxidation of NADH and have been used for dehydrogenase biosensors development [1, 2]. Flavins (contain in chemical structure isoalloxazine ring) are the prosthetic groups responsible for NAD+/NADH conversion in the active sites of some dehydrogenase enzymes. Upon the electropolymerization of flavin derivatives, the effective catalysts of NAD+/NADH regeneration, which mimic the NADH-dehydrogenase activity, would be synthesized [3]. 

KD Gibson, HA Scheraga. In RH Sarma, MH Sarma, eds. Structure and Expression, Vol 1, From Proteins to Ribosomes. New York Adenine Press, 1988, pp 67-94. 

Figure 13.4 Schematic diagram (a) and topology diagram (b) of the polypeptide chain of cH-ras p21. The central p sheet of this a/p structure comprises six p strands, five of which are parallel a helices are green, p strands are blue, and the adenine, ribose, and phosphate parts of the GTP analog are blue, green, and ted, respectively. The loop regions that are involved in the activity of this protein are red and labeled Gl-GS. The Gl, G3, and G4 loops have the consensus sequences G-X-X-X-X-G-K-S/T, D-X-X-E, and N-K-X-D, respectively. (Adapted from E.R Pai et al., Nature 341 209-214, 1989.)...

Adenine is a weak base. Which one of the three nitrogens designated by arrows in the structural formula shown is protonated in acidic solution A resonance evaluation of the three protonated forms will tell you which one is the most stable. 

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. 

Several classes of vitamins are related to, or are precursors of, coenzymes that contain adenine nucleotides as part of their structure. These coenzymes include the flavin dinucleotides, the pyridine dinucleotides, and coenzyme A. The adenine nucleotide portion of these coenzymes does not participate actively in the reactions of these coenzymes rather, it enables the proper enzymes to recognize the coenzyme. Specifically, the adenine nucleotide greatly increases both the affinity and the speeifieity of the coenzyme for its site on the enzyme, owing to its numerous sites for hydrogen bonding, and also the hydrophobic and ionic bonding possibilities it brings to the coenzyme structure. 

Riboflavin, or vitamin B2, is a constituent and precursor of both riboflavin 5 -phosphate, also known as flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD). The name riboflavin is a synthesis of the names for the molecule s component parts, ribitol and flavin. The structures of riboflavin. 

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 ). 

The determination of the structure of adenine hydrochloride (see Volume 2, Section IV,K, of article IV by Katritzky and Lagowski) is an example of extremely accurate X-ray crystallography whereby the positions of individual hydrogen atoms were located. An example of the deduction of structure from bond lengths between heavy atoms is provided by Penfold s investigation of pyrid-2-thione. ... 

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