Proteins polypeptide

A dipeptide is a molecule consisting of two ammo acids joined by a peptide bond A tnpeptide has three ammo acids joined by two peptide bonds a tetrapeptide has four ammo acids and so on Peptides with more than 30-50 ammo acids are polypeptides Proteins are polypeptides that have some biological function... 

Sephadex. Other carbohydrate matrices such as Sephadex (based on dextran) have more uniform particle sizes. Their advantages over the celluloses include faster and more reproducible flow rates and they can be used directly without removal of fines . Sephadex, which can also be obtained in a variety of ion-exchange forms (see Table 15) consists of beads of a cross-linked dextran gel which swells in water and aqueous salt solutions. The smaller the bead size, the higher the resolution that is possible but the slower the flow rate. Typical applications of Sephadex gels are the fractionation of mixtures of polypeptides, proteins, nucleic acids, polysaccharides and for desalting solutions. 

The biological function of biopolymers such as polypeptides, proteins, nucleic acids etc. depends strongly on their ordered structure which is determined by the pattern of inter- and intramolecular interactions given by the primary structure. 

Nevertheless, despite the inherent disadvantages of exclusion chromatography, there are instances where it is the only practical method of choice. The technique is widely used in the separation of macro-molecules of biological origin, e.g. polypeptides, proteins, enzymes, etc. In fact, it is in this area of biotechnology where the major growth in HPLC techniques appears to be taking place. 

Types Steroids, iodothyro-nines, calcitriol, retinoids Polypeptides, proteins, glycoproteins, catecholamines... 

Chemical techniques for the isolation, purification and elucidation of the structure of toxins have evolved to the extent that it is frequently a routine procedure to identify the chemical nature of a newly discovered toxin once it has been purified, although difficulties arise when the toxin is a very large polypeptide, protein, or a very complex organic molecule. However, it is sometimes found that a toxin becomes progressively more labile and stabilizing contaminants are removed by the purification processes. An example of this is Cyanea toxic material which becomes increasingly labile with each purification step 111). 

Wilson, W.R., Tuan, R.S., Shepley, K.J., Freedman, D.O., Greene, B.M., Awadzi, K. and Unnasch, T.R. (1994) The Onchocerca volvulus homologue of the multifunctional polypeptide protein disulfide isomerase. Molecular and Biochemical Parasitology 68, 103-117. 

There are three potential methods by which a protein s three-dimensional structure can be visualized X-ray diffraction, NMR and electron microscopy. The latter method reveals structural information at low resolution, giving little or no atomic detail. It is used mainly to obtain the gross three-dimensional shape of very large (multi-polypeptide) proteins, or of protein aggregates such as the outer viral caspid. X-ray diffraction and NMR are the techniques most widely used to obtain high-resolution protein structural information, and details of both the principles and practice of these techniques may be sourced from selected references provided at the end of this chapter. The experimentally determined three-dimensional structures of some polypeptides are presented in Figure 2.8. 

OATP/oatp Organic anion transporting polypeptide (protein / nucleic acid)... 

Macromolecules may be classified according to different criteria. One criterion is whether the material is natural or synthetic in origin. Cellulose, lignin, starch, silk, wool, chitin, natural rubber, polypeptides (proteins), polyesters (polyhydroxybutyrate), and nucleic acids (DNA, RNA) are examples of naturally occurring polymers while polyethylene, polystyrene, polyurethanes, or polyamides are representatives of their synthetic counterparts. When natural polymers are modified by chemical conversions (cellulose —> cellulose acetate, for example), the products are called modified natural polymers. 

Polymeric amides are found in nature in the many polypeptides (proteins) that constitute a variety of animal organisms and the composition of silk and wool. It was a search to prepare substitutes for the latter that led to the commercial development of the synthetic polyamides known as nylons. 

Three amino acids can be joined by two peptide bonds to form a tripeptide similarly, amino acids can be linked to form tetrapeptides, pentapeptides, and so forth. When a few amino acids are joined in this fashion, the structure is called an oligopeptide. When many amino acids are joined, the product is called a polypeptide. Proteins may have thousands of amino acid residues. Although the terms protein and polypeptide are sometimes used interchangeably, molecules referred to as polypeptides generally have molecular weights below 10,000, and those called proteins have higher molecular weights. 

R. R. Becker, Polyamino Acids, Polypeptides, Proteins, Proc. Intern. Symp., Madison, Wise. 1961 p. 301. Univ. of Wisconsin Press, Madison, Wisconsin, 1962. 

Further reaction with many more amino acids takes place at each end of each molecule to produce the final protein (Figures 15.22 and 15.23). For a molecule to be a protein, there must be at least 100 amino acids involved. Below this number, they are called polypeptides. Proteins make up some 15% of our body weight. 

Fig. 7.10. Plot of the PCA coefficients for the two most important basis functions for a set of 78 polypeptide, protein and virus ROA spectra. Definitions of the structural types analysed are all alpha, > 60% a-helix with little other secondary structure mainly alpha, > 35% a-helix and a small amount of (3-sheet ( 5-15%) alpha beta, similar significant amounts of a-helix and (3-sheet mainly beta, > 35% 13-sheet and a small amount of a-helix ( — 5—15%) all beta, > 45% (3-sheet with little other secondary structure mainly disordered/irregular, little secondary structure all disordered/irregular, no secondary structure...

Charged and hydrophilic large molecules (polypeptides, proteins) were challenging compounds tested with ethosomal carriers [93,98-100]. The ability of trihexyphenidyl hydrochloride... 

The order of amino acids in the protein molecule determines its primary structure. Secondary protein structures result from the folding of polypeptide protein chains to produce a maximum number of hydrogen bonds between peptide linkages ... 

TGM2 Transglutaminase 2 (6 polypeptide, protein-glutamine-gamma-glutamyltransferase)... 

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