Nucleic acids biological role

In contrast, RNA occurs in multiple copies and various forms (Table 11.2). Cells contain up to eight times as much RNA as DNA. RNA has a number of important biological functions, and on this basis, RNA molecules are categorized into several major types messenger RNA, ribosomal RNA, and transfer RNA. Eukaryotic cells contain an additional type, small nuclear RNA (snRNA). With these basic definitions in mind, let s now briefly consider the chemical and structural nature of DNA and the various RNAs. Chapter 12 elaborates on methods to determine the primary structure of nucleic acids by sequencing methods and discusses the secondary and tertiary structures of DNA and RNA. Part rV, Information Transfer, includes a detailed treatment of the dynamic role of nucleic acids in the molecular biology of the cell. 

The formation of three-stranded nucleic acid complexes was first demonstrated over five decades ago [56] but the possible biological role of an extended triplex was expanded by the discovery of the H-DNA structure in natural DNA samples [57-59]. H-DNA is an intermolecular triplex that is generally of the pyrimidine-purine x pyrimidine type ( dot -Watson-Crick pairing and cross Hoogsteen base paring) and can be formed at mirror repeat sequences in supercoiled plasmids [59]. 

Quinone methides have been shown to be important intermediates in chemical synthesis,1 2 in lignin biosynthesis,3 and in the activity of antitumor and antibiotic agents.4 They react with many biologically relevant nucleophiles including alcohols,1 thiols,5-7 nucleic acids,8-10 proteins,6 11 and phosphodiesters.12 The reaction of nucleophiles with ortho- and /iara-quinone methides is pH dependent and can occur via either acid-catalyzed or uncatalyzed pathways.13-17 The electron transfer chemistry that is typical of the related quinones does not appear to play a role in the nucleophilic reactivity of QMs.18... 

The compounds that are identifiable in the sea represent a vast array of biochemicals attributable to the life and death of marine plants and animals. They are generally grouped into six classes based on structural similarities hydrocarbons, carbohydrates, lipids, fatty acids, amino acids, and nucleic acids. Because they represent compounds that can be quantified and understood for their chemical properties and known role in biological systems, a great deal of information has been accumulated over the years about these groups and the specific compounds found within them.7... 

Fluorescence is also a powerful tool for investigating the structure and dynamics of matter or living systems at a molecular or supramolecular level. Polymers, solutions of surfactants, solid surfaces, biological membranes, proteins, nucleic acids and living cells are well-known examples of systems in which estimates of local parameters such as polarity, fluidity, order, molecular mobility and electrical potential is possible by means of fluorescent molecules playing the role of probes. The latter can be intrinsic or introduced on purpose. The high sensitivity of fluo-rimetric methods in conjunction with the specificity of the response of probes to their microenvironment contribute towards the success of this approach. Another factor is the ability of probes to provide information on dynamics of fast phenomena and/or the structural parameters of the system under study. 

Macromolecules of biological origin perform various functions in the body. For example, proteins which perform the role of biological catalysts in the body are called enzymes, those which are crucial to communication system in the body are called receptors. Carrier proteins carry polar molecules across the cell membrane. Nucleic acids have coded genetic information for the cell. Lipids and carbohydrates are structural parts of the cell membrane. We shall explain the drug-target interaction with the examples of enzymes and receptors. 

NMR is a powerful and versatile tool for structural studies of biological RNAs and complexes they form with other nucleic acids, proteins, and small molecules. The goal of these studies is to determine the role that structure and dynamics play in biological function. NMR has the capacity to determine high-resolution structures, as well as to map RNAiligand interfaces at low resolution. Most structures of RNA and RNA-ligand complexes are under 20 KDa in size however, recent advances allow for determination of solution structures of complexes up to 40 kDa. NMR can also probe dynamic motions in RNA on micro- to millisecond time scales. A number of biologically relevant internal motions such as... 

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