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Z-RNA
Z-RNA is a left-handed alternative conformation for the RNA double helix. Just like for Z-DNA, Z-RNA is favored by a sequence composed of Purine/Pyrimidine repeats and especially CG repeats. Discovery The ability of dsRNA to convert into a left-handed helix was demonstrated using NMR and circular dichroism Circular dichroism (CD) is dichroism involving circular polarization, circularly polarized light, i.e., the differential Absorption (electromagnetic radiation), absorption of left- and right-handed light. Left-hand circular (LHC) and right-hand ci ... in 1984. This conversion was shown to require high ionic strength and elevated temperatures (35 degrees). Structural characteristics Z-RNA to resemble, but not be identical, to that of Z-DNA. The structure of the complex of a Zalpha domain with Z-RNA under close to physiological salt concentrations however suggests a structure much closer to the Z-DNA conformation and points to two forms of Z-RNA (low and high salt conformations) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Z-DNA
Z-DNA is one of the many possible double helical structures of DNA. It is a left-handed double helical structure in which the helix winds to the left in a zigzag pattern, instead of to the right, like the more common B-DNA form. Z-DNA is thought to be one of three biologically active double-helical structures along with A-DNA and B-DNA. History Left-handed DNA was first proposed by Robert Wells and colleagues, as the structure of a repeating polymer of inosine–cytosine. They observed a "reverse" circular dichroism spectrum for such DNAs, and interpreted this incorrectly to mean that the strands wrapped around one another in a left-handed fashion. The relationship between Z-DNA and the more familiar B-DNA was indicated by the work of Pohl and Jovin, who showed that the ultraviolet circular dichroism of poly(dG-dC) was nearly inverted in 4 M sodium chloride solution and that the structure of poly d(I–C)·poly d(I–C) was in fact a right-handed D-DNA conformation. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circular Dichroism
Circular dichroism (CD) is dichroism involving circular polarization, circularly polarized light, i.e., the differential Absorption (electromagnetic radiation), absorption of left- and right-handed light. Left-hand circular (LHC) and right-hand circular (RHC) polarized light represent two possible spin angular momentum of light, spin angular momentum states for a photon, and so circular dichroism is also referred to as dichroism for spin angular momentum. This phenomenon was discovered by Jean-Baptiste Biot, Augustin Fresnel, and Aimé Cotton in the first half of the 19th century. Circular dichroism and optical rotation, circular birefringence are manifestations of optical activity. It is exhibited in the absorption (electromagnetic radiation), absorption bands of optical activity, optically active chirality (chemistry), chiral molecules. CD spectroscopy has a wide range of applications in many different fields. Most notably, Ultraviolet, far-UV CD is used to investigate the second ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
