Protein basic chemical units

Textile fibers are normally broken down into two main classes, natural and man-made fibers. All fibers which come from natural sources (animals, plants, etc.) and do not require fiber formation or reformation are classed as natural fibers. Natural fibers include the protein fibers such as wool and silk, the cellulose fibers such as cotton and linen, and the mineral fiber asbestos. Man-made fibers are fibers in which either the basic chemical units have been formed by chemical synthesis followed by fiber formation or the polymers from natural sources have been dissolved and regenerated after passage through a spinneret to form fibers. Those fibers made by chemical synthesis are often called synthetic fibers, while fibers regenerated from natural polymer sources are called regenerated fibers or natural polymer fibers. In other words, all synthetic fibers and regener-... 

FIGURE 1-2 Diverse living organisms share common chemical features. Birds, beasts, plants, and soil microorganisms share with humans the same basic structural units (cells) and the same kinds of macromolecules (DNA, RNA, proteins) made up of the same kinds of monomeric subunits (nucleotides, amino acids). They utilize the same pathways for synthesis of cellular components, share the same genetic code, and derive from the same evolutionary ancestors. Shown here is a detail from "The Garden of Eden," by Jan van Kessel the Younger (1626-1679). 

Fig. 2.1. a. Basic chemical structure and stereochemistry of L-amino acids, b. Polymeric structure of proteins and peptides constructed from monomeric units. 

Proteins are macromolecules consisting of 20 different amino acid residues arranged in a highly sophisticated three-dimensional structure. The basic structural units of proteins are amino acids. All proteins are constructed from the same set of 20 amino acids in different combinations. These 20 building blocks differ in size, shape, polarity, charge, and chemical reactivity. Amino acids are joined by peptide linkage between the a-carboxyl group of one amino acid... 

A polymer is a macromolecule that is constructed by chemically linking together a sequent of molecular fragments. In simple synthetic polymers such as polyethylene or polystyrer all of the molecular fragments comprise the same basic unit (or monomer). Other poly me contain mixtures of monomers. Proteins, for example, are polypeptide chains in which eac unit is one of the twenty amino acids. Cross-linking between different chains gives rise to j-further variations in the constitution and structure of a polymer. All of these features me affect the overall properties of the molecule, sometimes in a dramatic way. Moreover, or... 

As already noted, it is the basic element of all living and once-living tissue. It has the capacity to combine in a multiplicity of complex chains with other elements to form new chemicals. Some of these you know as carbohydrates, fats, and proteins. But there are many others. There are many different carbohydrates, fats, and proteins that in turn can unite in... 

Amino acids The basic units that join together to make proteins. They contain functional groups amines (-NH2) and carboxylic acids (-COOH), hence their name. The chemical bonds formed between amino acids when joining together to form proteins are called peptide links. 

Hydrolysed protein preparations have been used to attract various insects. The general subject of insect attractant use both in nature and by man is introduced, with particular reference to the Tephritid family of fruit flies. The work of the Biocommuni-cation Chemistry Research Unit on the identification of the active attractant compounds in the hydrolysed corn protein, Nu-Lure Insect Bait (NLIB) is discussed. Different isolates have been obtained by running simultaneous steam distillation-extractions (SDE) under vacuum and atomospherlc pressure and under basic and acidic conditions. Chemical fractionation of these isolates has also been accomplished. Chemical identification by gas chromatography/mass spectrometry (gc/ms) is discussed. 

In this problem, we will determine the degrees of freedom of a process circuit conqjosed of several process units by examining a methanol-synthesis process. Methanol was first synthesized from carbon monoxide and hydrogen on a commercial scale in 1923 by Badische Anilindund Soda-Fabrik (BASF) in Germany [25]. Methanol is an important basic bulk chemical used in the synthesis of formaldehyde and acetic acid [28] and it has been proposed as an automobile fuel and fixel additive [26]. Methanol has also been proposed as a substrate to produce a bacterium suitable as a protein source (single-cell protein). The bacterium would be a soy meal and fishmeal substitute for animal and poultry feeds [27]. If these applications should ever develop, the demand for methanol will increase considerably. 

The twenty basic units of differing chemical properties, their random order and variable abundance in the polymer, and the variable length of proteins provide a tremendous diversity to proteins as a class. For example, there are 400 possible dipeptides (20x20) and 8000 (20 ) possible tripeptides, and the numbers become astronomical (20 ) when even moderately small proteins of as few as 100 amino acids are considered. Superimposed on this diversity are further modifications such as intrachain and interchain disulfide linkages, which are covalent linkages between cysteines, and other covalent modifications of the sidechains of individual amino acids (discussed below). The linear amino acid sequence together with further covalent modifications is known as the primary structure of a protein. 

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