Nucleic acid definition

Nonviral Coding Nucleic Acids Definition and Characteristics in Relation to Potential Therapeutic Use... 

NONVIRAL CODING NUCLEIC ACIDS DEFINITION AND CHARACTERISTICS IN RELATION TO POTENTIAL THERAPEUTIC USE... 

Lavery R and H Sklenar 1988. The Definition of Generalized Helicoidal Parameters and of A> Curvature for Irregular Nucleic Acids. Journal of Biomolecular Structure and Dynamics 5 63-91. 

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. 

In addition to effects on biochemical reactions, the inhibitors may influence the permeability of the various cellular membranes and through physical and chemical effects may alter the structure of other subcellular structures such as proteins, nucleic acid, and spindle fibers. Unfortunately, few definite examples can be listed. The action of colchicine and podophyllin in interfering with cell division is well known. The effect of various lactones (coumarin, parasorbic acid, and protoanemonin) on mitotic activity was discussed above. Disturbances to cytoplasmic and vacuolar structure, and the morphology of mitochondria imposed by protoanemonin, were also mentioned. Interference with protein configuration and loss of biological activity was attributed to incorporation of azetidine-2-carboxylic acid into mung bean protein in place of proline. 

The concept of the similarity of molecules has important ramifications for physical, chemical, and biological systems. Grunwald (7) has recently pointed out the constraints of molecular similarity on linear free energy relations and observed that Their accuracy depends upon the quality of the molecular similarity. The use of quantitative structure-activity relationships (2-6) is based on the assumption that similar molecules have similar properties. Herein we present a general and rigorous definition of molecular structural similarity. Previous research in this field has usually been concerned with sequence comparisons of macromolecules, primarily proteins and nucleic acids (7-9). In addition, there have appeared a number of ad hoc definitions of molecular similarity (10-15), many of which are subsumed in the present work. Difficulties associated with attempting to obtain precise numerical indices for qualitative molecular structural concepts have already been extensively discussed in the literature and will not be reviewed here. 

DNA arrays have been categorized into different formats based upon what is immobilized to the surface (also known as the solid phase, substrate, or chip) and what is captured from the sample solution. Definitions change depending upon the format. For the classic Southern dot blot, the sample was first spotted down on the surface, cross-linked, and then bathed with a radio-labeled oligonucleotide under hybridization (complementary nucleic acid strand base-pairing) conditions to detect the presence of a parhcular sequence within the sample. This was called probing. The oligonucleohde... 

It is worth to mention that this definition is not always consistent with the nature of the macromolecular assembly when applying to nucleic acids. For example, from all different types of quadruplex nucleic acids only quadruplex monomers are covered by lUPAC definition of tertiary structure being a single chain of DNA or RNA. However, also the quadruplexes with higher molecularity of the formed structures (dimers, tetramers) belong to this important tertiary structure family. 

The oldest definitions of life, such as those given by Engels, Bernal, and Rolle, referred to what we have called life at the individual level. With the advent of molecular biology and the emergence of nucleic acids, genetics also became important when considering the definition of life. 

The popularity of the NASA definition among the scientists studying the origin of life reflects this obvious prejudice, that the molecular mechanism of nucleic acids is the main and only reality for defining life. This definition is particularly dear to all adherents of the RNA-world, and actually the NASA definition appears to be created to define life at the molecular level. In fact, some of the adherents to the RNA-world would probably be satisfied by the definition of minimal life summarized (Luisi, 1998) in the following terms ... 

Closely related to solvent effect, and governed by the same or similar factors, are the phenomena of dimerization via self-association, and association with other species present in solution, such as cations or anions, in definite stoichiometric proportions. Studies of such associations lead to further knowledge of such interactions involving the more complex bases in nucleic acid structures. One of the earliest workers to study dimerization systematically was Shindo (59CPB407), who examined the broad N—H stretch region 3300-2400 cm-1 in the IR spectra of a variety of substituted pyridin-2-ones and quinolin-2-ones in perfluorocarbon mulls and CC14 solution. 

All the phosphodiester linkages have the same orientation along the chain (Fig. 8-7), giving each linear nucleic acid strand a specific polarity and distinct 5 and 3 ends. By definition, the 5 end lacks a nucleotide at the 5 position and the 3 end lacks a nucleotide at the 3 position. Other groups (most often one or more phosphates) may be present on one or both ends. 

A short nucleic acid is referred to as an oligonucleotide. The definition of short is somewhat arbitrary, but polymers containing 50 or fewer nucleotides are generally called oligonucleotides. A longer nucleic acid is called a polynucleotide. 

Operational Definition of Lipids How is the definition of lipid different from the types of definitions used for other biomolecules that we have considered, such as amino acids, nucleic acids, and proteins ... 

RNA is the only macromolecule known to have a role both in the storage and transmission of information and in catalysis, which has led to much speculation about its possible role as an essential chemical intermediate in the development of life on this planet. The discovery of catalytic RNAs, or ribozymes, has changed the very definition of an enzyme, extending it beyond the domain of proteins. Proteins nevertheless remain essential to RNA and its functions. In the modem cell, all nucleic acids, including RNAs, are complexed with proteins. Some of these complexes are quite elaborate, and... 

In general, the problem of tautomerism in nucleic acid bases has been approached by comparing the IR spectra of several isoelectronic model compounds. The model corresponding to the cytosine tautomers 4 or 5 have not yet been investigated. The IR spectroscopy studies cannot therefore definitely rule out these tautomers. It seems, however, that they do rule out form 6 for cytosine and cytidine and indicate that the dominant tautomer of the compounds in aqueous solution is the lactam-amino form 2, and that the protonated cations have the structure 7. 

The hybridisation of a nucleic acid to its complementary target is one of the most definite and well-known molecular recognition events. Therefore, the hybridisation of a nucleic acid probe to its DNA target can provide a very high degree of accuracy for identifying complementary DNA sequences [32-36]. 

An antimetabolite is a compound that is (1) similar to a compound required for normal cellular function and (2) interferes with cellular processes. Based on this definition, many drugs technically qualify as antimetabolites. The term antimetabolite is, however, most closely associated with drugs that interfere with the synthesis or action of nucleic acids. Antimetabolites are commonly discussed in the treatment of cancer, viruses, and bacterial infections. 

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