Composition and Primary Structure

Nucleic acids are high molecular weight polymers whose fundamental repeating units, the mononucleotides, link together to form what are essentially one-dimensional polymers. There are two principal types of nucleic acids  

Generally DNA is found only in the cell nucleus while RNA may be found throughout the cell. Viruses, in contrast, appear to contain DNA or RNA but not both. 

Mononucleotide units are built from three main components (1) a phosphate group, (2) a sugar—ribose or deoxyribose, (3) a nitrogen base—a purine or a pyrimidine. 

In RNA the sugar is ribose and the base is either adenine (A), cytosine (C), guanine (G) or uracil (U) (10.68). In DNA the sugar is 2-deoxyribose and the base is adenine, cytosine, guanine or thymine (T). 

The purines and pyrimidines aU show lactam-lactim tautomerism (10.70). At neutral pH, keto forms predominate, but the effect of alkali is to cause a shift towards enol forms. This can affect the stability of the double helices of DNA and RNA (below). 

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Das A, Ljungdahl LG. 1997. Composition and primary structure of the FiFq ATP synthase from the obhgately anaerobic bacterium Clostridium thermoaceticum. J Bacteriol 179 3746-55. 

As is evident from the above discussion, the composition and primary structure of the peptide as well as the characteristics of the mobile and stationary phases all play critical roles in determining the magnitude of retention in RPC. Solvophobic theory 17 39 40 47 56 69-71 can be... 

A. I. Usov, Alginic acids and alginates Analytical methods used for their estimation and characterization of composition and primary structure, Russ. Chem. Rev., 68 (1999) 957-966 (translated from, Uspekhi Khimii, 68 (1999) 1051-1061). 

The amino acid composition and primary structure of B. ntori and S.c. ricini 104 silk fibroin... 

THE AMINO ACID COMPOSITION AND PRIMARY STRUCTURE OF B. mori AND S.c. ricini SILK FIBROIN... 

The aerospace field is a broad one and has a complex history. A comprehensive review of structural adhesive applications on currently flying aerospace vehicles alone could fill its own book. Hence this chapter will concentrate on the aerospace commercial transport industry and its use of adhesives in structural applications, both metallic and composite. Both primary structure, that is structure which carries primary flight loads and failure of which could result in loss of vehicle, and secondary structure will be considered. Structural adhesives use and practice in the military aircraft and launch vehicle/spacecraft fields as well as non-structural adhesives used on commercial aircraft will be touched on briefly as well. 

Evans, R.E. and Masters, J.E. (1987). A new generation of epoxy composites for primary structural applications materials and mechanics. In Toughened Coinpo.sites, ASTM STP 937 (N.J. Johnston ed.). ASTM. Philadelphia, PA, pp 413-436. 

The contributions of Richard Block to the serum protein problem originated from the hypothesis of Kossel. From recent data on the amino acid composition of the proteins found in animal sera, a formulation is derived which reflects the properties of a continuous system of molecular species originating from a common biosynthetic pathway, as if from mixed polymers of monomeric peptides of lower molecular weight. Indirect evidence of this is found in the amino acid interrelationship, and direct evidence is limited to the isolation of peptides of common composition, whose primary structures are still under investigation. These findings suggest that undifferentiated proteins may be continuous systems rather than discrete molecular species. 

Physicochemical Properties. These will generally include determination of the composition, physical properties, and primary structure. 

A physico-chemical characterization program will generally include a determination of the composition, physical properties, and primary structure of the desired product. In some cases, information regarding higher-order structure of the desired product (the fidelity of which is generally inferred by its biological activity) may be obtained by appropriate physico-chemical methodologies. 

Primary structure refers to the atomic composition and chemical structure of the monomer — the building block of the polymer chain. An appreciation of the nature of the monomer is fundamental to understanding the structure-property relationship of polymers. The chemical and electrical properties of a polymer are directly related to the chemistry of the constituent monomers. The physical and mechanical properties of polymers, on the other hand, are largely a consequence of the macromolecular size of the polymer, which in itself is related to the nature of the monomer. By definition, a polymer is a chain of atoms hooked together by primary valence bonds. Therefore, basic to understanding the structure of the monomer vis-a-vis the structure and properties of the resulting polymer is a fundamental understanding of ... 

For compositions and crystal structures, see Tables 3.1-122-3.1-124 [1.217,218,223,224]. Primary solid solutions have the fee structure of Ag and the lattice parameters correspond roughly to Vegard s rule with a few exceptions. Alloys with Pt, In, Mg, Cd, and Zn form superlattice phases with tetrahedral and rhombo-... 

The chemical composition and the structure of the contamination layer oxides in the primary systems depend highly on the reactor type (PWR, BWR) and also on the operational history of the plant. The optimum decontamination process to be applied, therefore, must be selected and, if necessary, optimized to meet the task in question. In particular, when components and systems are to be decontaminated, different structural materials and, consequently, oxide layers of different composition are involved, resulting in more stringent demands on the decontamination procedures to be applied. 

Various elemental and molecular microanalysis techniques are now available. Characterisation is usually carried out with (micro)beam techniques. By interaction of a primary beam (electrons, photons, ions), secondary signals are generated at the material (electrons, photons, ions, neutrals), which contain information on the composition and/or structure of the material. The various techniques differ in the type of information obtained, i.e. information depth, depth resolution, possibility to obtain depth profiles, lateral resolution, compatibility with certain types of materials (conductors v. insulators), destructive or nondestructive character, and type of information (elemental, isotopic, molecular). The polymer/additive analyst s challenge is to understand and choose from the vast array of available analysis and imaging techniques. 

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