Biopolymers nucleic adds

BIOPOLYMERS. Biopolymers are the naturally occurring macromolec-ular materials that are the components of all living systems. There are three principal categories of biopolymers, proteins nucleic adds and polysaccharides. See also Carbohydrates. Biopolymers are formed through condensation of monomeric units i.e., the corresponding monomers are amino acids, nucleotides, and monosaccharides for proteins, nucleic acids, and polysaccharides, respectively. The term biopolymers is also used to describe synthetic polymers prepared from the same or similar monomer units as are the natural molecules. 

Several factors must be considered for a particular biomacromolecular structure application that will affect the choice of spectroscopic methods. These include structural resolution necessary, chemical nature of biomacromolecule (protein, nucleic add, or glycan), amount/concentration of biopolymer available, sample preparation (solid or solution), solvents of interest, and desired structure information (secondary or tertiary structure). Structural resolution varies considerably for the various spectroscopic methods, with X-ray diffraction and NMR providing atomic resolution (high resolution) and ultraviolet (UV) absorption revealing merely information about the polarity of the chromophore s environment (low resolution). X-ray studies require crystals while NMR experiments prefer solutions in deuterated solvent. Solvent preferences can affect the choice of spectroscopic method as, for example, infrared (IR) encoimters strong interference from water, while optical rotatory dispersion (ORD) and circniar dichroism (CD) do not. Some of the commonly used spectroscopic methods in structural analyses of biomacromolecules will be discussed. 

Of the three above-mentioned major classes of natural biopolymers, chemical synthesis of nucleic adds (in particular DNA) and proteins had already been achieved by the Merrifield solid-phase synthesis method a computer-controlled automated synthesizer became commerdally available more than 20 years ago. However, the chemical synthesis of polysaccharides like cellulose was far more difficult than that of the former two classes. Polysaccharide synthesis is the repetition of glycosylation, the most fimdamental reaction in carbohydrate chemistry (Scheme 2). 

Nucleic acid (Introduction, Chapter 28) A biopolymer containing three types of monomer units heterocyclic aromatic amine bases derived from purine and pyrimidine, the monosaccharides D-ribose or 2-deoxy-D-iibose, and phosphoric add. 

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