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Calcium oxide is also a separate mineral species (with the unit formula CaO), named 'Lime'. [30] [31] It has an isometric crystal system, and can form a solid solution series with monteponite. The crystal is brittle, pyrometamorphic, and is unstable in moist air, quickly turning into portlandite (Ca(OH) 2). [32]
DNA and RNA also contain other (non-primary) bases that have been modified after the nucleic acid chain has been formed. In DNA, the most common modified base is 5-methylcytosine (m 5 C). In RNA, there are many modified bases, including those contained in the nucleosides pseudouridine (Ψ), dihydrouridine (D), inosine (I), and 7-methylguanosine ...
Ambigrams (symbols that convey different meaning when viewed in a different orientation) have been designed to mirror structural symmetries found in the DNA double helix. [9] By assigning ambigraphic characters to complementary bases (i.e. guanine: b, cytosine: q, adenine: n, and thymine: u), it is possible to complement DNA sequences by simply ...
Calcium peroxide or calcium dioxide is the inorganic compound with the formula CaO 2. It is the peroxide (O 2 2−) salt of Ca 2+. Commercial samples can be yellowish, but the pure compound is white. It is almost insoluble in water. [3]
A section of DNA. The bases lie horizontally between the two spiraling strands [15] (animated version). The DNA double helix is stabilized primarily by two forces: hydrogen bonds between nucleotides and base-stacking interactions among aromatic nucleobases. [16] The four bases found in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T).
Ten years after James Watson and Francis Crick published their model of the DNA double helix, [2] Karst Hoogsteen reported [3] a crystal structure of a complex in which analogues of A and T formed a base pair that had a different geometry from that described by Watson and Crick. Similarly, an alternative base-pairing geometry can occur for G ...
The nucleobases are important in base pairing of strands to form higher-level secondary and tertiary structures such as the famed double helix. The possible letters are A , C , G , and T , representing the four nucleotide bases of a DNA strand – adenine , cytosine , guanine , thymine – covalently linked to a phosphodiester backbone.
These bonds are weak, easily separated by gentle heating, enzymes, or physical force. Melting occurs preferentially at certain points in the nucleic acid. [3] T and A rich sequences are more easily melted than C and G rich regions. Particular base steps are also susceptible to DNA melting, particularly T A and T G base steps. [4]