Protein A naturally occurring polymeric

Protein A naturally occurring polymeric chain of L-amino acids linked together by peptide bonds. 

The conversion of animal hides into leather by treatment with water-soluble plant extractives has been practiced since antiquity. This process became known as tanning and obviously involved the reaction of a naturally occurring extractive, tannin, with the protein in the hide. We now know, of course, that tannins comprise a whole spectrum of chemical compounds, but generally they are polyphenolic and polymeric. Tannins have been isolated from a wide variety of raw materials, including insect galls, fruit skins, seed hulls, leaves, bark, and heartwood. Indeed, tannins are of nearly ubiquitous occurrence in higher orders... 

Some six hundred structures of naturally occurring carbogenic molecules appe on the pages which follow, together with the name of each compound and references to the original literature of successful chemical synthesis. Thus, Part Three of this book is effectively a key to the literature of chemical synthesis as applied to the complex molecules of nature. The survey does not include oligomeric or polymeric structures, such as peptides, proteins, carbohydrates and polynucleotides, which fall outside the scope of this book because they can be assembled by repetitive procedures. 

Polymers are examples of organic compounds. However, the main difference between polymers and other organic compounds is the size of the polymer molecules. The molecular mass of most organic compounds is only a few hundred atomic mass units (for reference, atomic hydrogen has a mass of one atomic mass unit). The molecular masses of polymeric molecules range from thousands to millions of atomic mass units. Synthetic polymers include plastics and synthetic fibers, such as nylon and polyesters. Naturally occurring polymers include proteins, nucleic acids, polysaccharides, and rubber. The large size of a polymer molecule is attained by the repeated attachment of smaller molecules called monomers. 

Amino acids become linked by reactions that occur between the amine group of one amino acid and the carboxyl group of another. As shown in Figure 22.23, this polymerization produces a molecule of water and, hence, is a condensation reaction. Naturally occurring polypeptides with molecular weights in excess of 10,000 daltons are termed proteins. These biomolecules are ubiquitous in marine organisms and are not specific to particular species. Proteins are important components of enzymes as well as of structural parts and connective tissues. 

Plants and animals synthesize a number of polymers (e.g., polysaccharides, proteins, nucleic acids) by reactions that almost always require a catalyst. The catalysts present in living systems are usually proteins and are called enzymes. Reactions catalyzed by enzymes are called enzymatic reactions, polymerizations catalyzed by enzymes are enzymatic polymerizations. Humans benefit from naturally occurring polymers in many ways. Our plant and animal foodstuffs consist of these polymers as well as nonpolymeric materials (e.g., sugar, vitamins, minerals). We use the polysaccharide cellulose (wood) to build homes and other structures and to produce paper. 

Another class of surfactants that are used in cosmetics and personal care products is the phosphoric acid esters. These molecules are similar to the phospholipids that are the building blocks of the stratum corneum (the top layer of the skin, which is the main barrier for water loss). Glycerine esters, in particular, triglycerides, are also frequently used. Macromolecular surfactants of the A-B-A block type [where A is PEO and B is polypropylene oxide (PPO)] are also frequently used in cosmetics. Another important naturally occurring class of polymeric surfactants is the proteins, which can be used effectively as emulsifiers. 

A) Macromolecular SOs They can be divided (a) into those consisting of the same repeat units or monomers (homopolymer) comprising the naturally occurring polysaccharide type SOs as well as synthetic polymeric type SOs (including polymethacrylate and imprinted polymer type SOs), and (b) into those made up of different repetitive units or monomers like the proteins. 

LI.2 Synthetic polymeric type CSPs. With the aim of mimicking nature and naturally occurring biopolymeric SOs like polysaccharides or proteins, researchers have developed several approaches for the preparation of new types of synthetic macromolec-ular SOs. These new polymeric SOs may be divided into (a) SOs synthesized from achiral monomers including helical polyacrylates and molecular imprint type CSPs and (b) SOs synthesized from chiral monomers including polyacrylamides and network polymers based on tartaric acid diamides. 

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