Nucleic acids Macromolecules with nucleotides

A major theme running through these chapters is the added complexity inherent in the biosynthesis of macromolecules that contain information. Assembling nucleic acids and proteins with particular sequences of nucleotides and amino acids represents nothing less than preserving the faithful expression of the template... 

In theory, if the net charge, q, on a molecule is known, it should be possible to measure / and obtain information about the hydrodynamic size and shape of that molecule by investigating its mobility in an electric field. Attempts to define /by electrophoresis have not been successful, primarily because Equation 4.3 does not adequately describe the electrophoretic process. Important factors that are not accounted for in the equation are interaction of migrating molecules with the support medium and shielding of the molecules by buffer ions. This means that electrophoresis is not useful for describing specific details about the shape of a molecule. Instead, it has been applied to the analysis of purity and size of macromolecules. Each molecule in a mixture is expected to have a unique charge and size, and its mobility in an electric field will therefore be unique. This expectation forms the basis for analysis and separation by all electrophoretic methods. The technique is especially useful for the analysis of amino acids, peptides, proteins, nucleotides, nucleic acids, and other charged molecules. 

Nucleic acid is the general name for the macromolecules RNA and DNA. They are each made up of a polymer of nucleotides with the 5 phosphate of each nucleotide forming a phosphodiester bond with the 3 hydroxyl of the adjacent one. 

Living cells today are assemblages that include very large molecules, such as proteins, nucleic acids, and polysaccharides. These molecules are larger by many powers of ten than the smaller molecules from which they are built. Hundreds or thousands of these smaller molecules, or monomers, can be linked to produce macromolecules, which are also called polymers. The versatility of carbon is important here. Carbon is tetravalent and able to form bonds with itself and with many other elements, giving rise to different kinds of monomers, such as amino acids, nucleotides, and monosaccharides (sugar monomers). 

Nucleic acid nu- kle-ik- [fr. their occurrence in cell nuclei] (1892) n. A family of macromolecules, of molecular masses ranging upward from 25,000, found in the chromosomes, nucleoli, mitochondria, and cytoplasm of all cells, and in viruses in complexes with proteins, they are called nu-cleoproteins. On hydrolysis they yield purines, pyrimidines, phosphoric acid, and a pentose, either D-ribose or D-deoxyribose from the last, the nucleic acid derive their more specific names, ribronucleic acid and deoxyribonucleic acid. Nuclear acids are liner (i.e., unbranched) chains of nucleotides in which the 5 -phosphoric group of each one is esterified with the 3 -hydroxyl of the adjoining nucleotide. Black JG (2002) Microbiology, 5th edn. John Wiley and Sons Inc., New York. 

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