Editing Guanine (section)

==Properties==
Guanine, along with adenine and cytosine, is present in both DNA and RNA, whereas thymine is usually seen only in DNA, and uracil only in RNA. Guanine has multiple [[tautomer]]ic forms. For the [[imidazole]] ring, the proton can reside on either nitrogen.  For the pyrimidine ring, the ring N-H can center can reside on either of the ring nitrogens.  The latter tautomer does not apply to nucleoside or nucleotide versions of guanine.<ref>{{cite book|author=Saenger, W.|title=Principles of Nucleic Acid Structure|publisher=Springer Science & Business Media|year=1984|doi= 10.1007/978-1-4612-5190-3|page = 112}}</ref>

It binds to cytosine through three [[hydrogen bond]]s. In cytosine, the amino group acts as the hydrogen bond donor and the C-2 carbonyl and the N-3 amine as the hydrogen-bond acceptors. Guanine has the C-6 carbonyl group that acts as the hydrogen bond acceptor, while a group at N-1 and the amino group at C-2 act as the hydrogen bond donors.{{cn|date=February 2024}}

{{multiple image
| align=center
| total_width = 400
| image1=Cytonum2.svg
| caption1=[[Cytosine]]
| image2=Guannum2.svg
| caption2=Guanine
| footer=Cytosine and guanine with the direction of hydrogen bonding indicated (arrow points positive to negative charge)
}}

Guanine can be [[hydrolyzed]] with strong acid to [[glycine]], [[ammonia]], [[carbon dioxide]], and [[carbon monoxide]]. First, guanine gets [[Deamination|deaminated]] to become [[xanthine]].<ref>{{cite web |last=Angstadt |first=Carol N |title=Purines and pyrimidines |url=http://library.med.utah.edu/NetBiochem/pupyr/pp.htm |date=1997 |access-date=2024-11-20 |website=utah.edu}}</ref> Guanine oxidizes more readily than adenine, the other purine-derivative base in DNA. Its high melting point of 350&nbsp;°C reflects the intermolecular hydrogen bonding between the oxo and amino groups in the molecules in the crystal. Because of this intermolecular bonding, guanine is relatively insoluble in water, but it is soluble in dilute acids and bases.