Circular nucleic acids

Plasmid DNAs. Plasmids are nucleic acid molecules capable of intracellular extrachromosomal repHcation. Usually plasmids are circular DNA species, but linear and RNA plasmids are known. In nature, plasmids can assume a variety of lifestyles. Plasmids can recombine into the host chromosome, be packaged into vims particles, and repHcate at high or low copy number relative to the host chromosome. Additionally, their information can affect the host phenotype. Whereas no single plasmid is usually capable of all these behaviors, the properties of various plasmids have been used to constmct vectors for a variety of purposes. 

Maiti M (1986) Application of circular dichroic technique in nucleic acids research. In Chatterjee SN (ed) Physical techniques in biology. Indian Physical Society, Calcutta, p 52... 

Not all the cellular DNA is in the nucleus some is found in the mitochondria. In addition, mitochondria contain RNA as well as several enzymes used for protein synthesis. Interestingly, mitochond-rial RNA and DNA bear a closer resemblance to the nucleic acid of bacterial cells than they do to animal cells. For example, the rather small DNA molecule of the mitochondrion is circular and does not form nucleosomes. Its information is contained in approximately 16,500 nucleotides that func-tion in the synthesis of two ribosomal and 22 transfer RNAs (tRNAs). In addition, mitochondrial DNA codes for the synthesis of 13 proteins, all components of the respiratory chain and the oxidative phosphorylation system. Still, mitochondrial DNA does not contain sufficient information for the synthesis of all mitochondrial proteins most are coded by nuclear genes. Most mitochondrial proteins are synthesized in the cytosol from nuclear-derived messenger RNAs (mRNAs) and then transported into the mito-chondria, where they contribute to both the structural and the functional elements of this organelle. Because mitochondria are inherited cytoplasmically, an individual does not necessarily receive mitochondrial nucleic acid equally from each parent. In fact, mito-chondria are inherited maternally. 

C. Helene, T. Montenay-Garestier, and J. L. Dimicoli, Interactions of tyrosine and tyramine with nucleic acids and their components. Fluorescence, nuclear magnetic resonance, and circular dichroism studies, Biochim. Biophys. Acta 254, 349-365 (1971). 

When genetic information (nucleic acid) is transferred between different cells, species or genera it is often carried by a specialized DNA molecule called a vector. Viruses are natural vectors, as are some kinds of small independently replicating circular extra-chromosomal DNA molecules (plasmids). A few of the basic features of plasmids used in molecular biology are reviewed in Figure 2.6. 

Optical Spectroscopy General principles and overview, 246, 13 absorption and circular dichroism spectroscopy of nucleic acid duplexes and triplexes, 246, 19 circular dichroism, 246, 34 bioinorganic spectroscopy, 246, 71 magnetic circular dichroism, 246, 110 low-temperature spectroscopy, 246, 131 rapid-scanning ultraviolet/visible spectroscopy applied in stopped-flow studies, 246, 168 transient absorption spectroscopy in the study of processes and dynamics in biology, 246, 201 hole burning spectroscopy and physics of proteins, 246, 226 ultraviolet/visible spectroelectrochemistry of redox proteins, 246, 701 diode array detection in liquid chromatography, 246, 749. 

Several direct methods are available to analyze the tertiary structure of ODNs like nuclear magnetic resonance (NMR) and X-ray crystallographic (XRC) techniques, which needs a sophisticated setup and infrastructure. An alternative but indirect method to study the structure and conformations of nucleic acids is circular dichroism spectroscopy (CD spectroscopy) (25, 26), where circular dichroism refers to the differential absorption of left and right circularly polarized light (27). 

Baase WA, Johnson WC Jr (1979) Circular dichroism and DNA secondary structure. Nucleic Acids Res 2 797-814... 

Induced Circular Dichroism in Nucleic Acid-Dye Systems... 

Circular Dichroism Spectral Properties of Nucleic Acids... 

Feasibility of the Induced Circular Dichroism Technique for Nucleic Acid Research... 

The significance of light absorption in biochemical studies lies in the great sensitivity of electronic energy levels of molecules to their immediate environment and to the fact that spectrophotometers are precise and sensitive. The related measurements of circular dichroism and fluorescence also have widespread utility for study of proteins, nucleic acids, coenzymes, and many other biochemical substances that contain intensely absorbing groups or chromophores.58... 

Vibrational circular dichroism involves IR absorption bands. The technique has been applied to sugars,110 oligosaccharides,111 proteins,112 and nucleic acids.113 The related vibrational Raman optical activity has also been applied to polyribonucleotides.114... 

Abstract Now an incisive probe of biomolecular structure, Raman optical activity (ROA) measures a small difference in Raman scattering from chiral molecules in right- and left-circularly polarized light. As ROA spectra measure vibrational optical activity, they contain highly informative band structures sensitive to the secondary and tertiary structures of proteins, nucleic acids, viruses and carbohydrates as well as the absolute configurations of small molecules. In this review we present a survey of recent studies on biomolecular structure and dynamics using ROA and also a discussion of future applications of this powerful new technique in biomedical research. 

Evdokimov, Y.M., Pyatigorskaya, T.L., Polyvtsev, O.F., Akimenko, N.M., Kadykov, V.A., Tsvanki, D.Y. and Marshavsky, Y.M. (1976) A comparative x-ray diffraction and circular dichroism study ofDNA compact particles formed in water-salt solutions, containing polyethylene glycol). Nucleic Acids Res., 3, 2353-2366. 

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