Polypeptide and polysaccharide

Principles to stabilize lipid bilayers by polymerization have been outlined schematically in Fig. 4a-d. Mother Nature — unfamiliar with the radically initiated polymerization of unsaturated compounds — uses other methods to-stabilize biomembranes. Polypeptides and polysaccharide derivatives act as a type of net which supports the biomembrane. Typical examples are spectrin, located at the inner surface of the erythrocyte membrane, clathrin, which is the major constituent of the coat structure in coated vesicles, and murein (peptidoglycan) a macromolecule coating the bacterial membrane as a component of the cell wall. Is it possible to mimic Nature and stabilize synthetic lipid bilayers by coating the liposome with a polymeric network without any covalent linkage between the vesicle and the polymer One can imagine different ways for the coating of liposomes with a polymer. This is illustrated below in Fig. 53. 

The biopolymer modeling of HyperChem includes Building polynucleotides, polypeptides and polysaccharides, Amino acid sequence (fasta format) editing, Mutations, Overlapping by RMS fit, and Merging structures. To facilitate manipulation of protein structures, there is often a need to display the protein backbone only as follows. 

These bacterial antigens (in their susceptibility to hydrolysis, which separates polysaccharide from the rest of the molecular complex) differ markedly from the blood-group substances, where amino acids and sugars cannot be separated from one another as polypeptide and polysaccharide. ... 

Sulfite oxidase catalyzes one of the final stops in the oxidation of the sulfur amino acids. The catabolism of methionine can result in the appearance of its sulfur atom in cysteine, as shown in Chapter 8. Cysteine can be oxidized to cysteine sulfonate, as shciwn in the section on taurine in Chapter 2, and then degraded to pyruvate. Daily, an average of 25 mmol of sulfite is produced in the body. This amount is large compared with the dally intake of fo< sulfite, which is about 2.5 mmol- The point at which sulfite oxidase occurs in the cysteine catabolic pathway is shown in Figure 10,53, Sulfate (SO ") is required for the synthesis of su I fated polypeptides and polysaccharides. It is thought that sulfate is not required in the dict-... 

Ans. Nucleic acids, polypeptides, and polysaccharides are synthesized from nucleotides, amino acids, and glucose, respectively. 

Biomacromolecules are considered as single molecules when they are present in a well-defined stoichiometry and when they display little tendency to dissociate spontaneously under physiological conditions. This text deals specifically with covalent bio-macromolecnles in which monomer units are linked together by covalent bonds to form giant biomolecules. They include nucleic acids, proteins and polysaccharides (under this defiifition, biomembranes are excluded). The Web site of the International Union of Bio-chenfistry and Molecular Biology (lUBMB) at http //www.chem.qmw.ac.uk/iubmb/ provides useful information for the nomenclature and conformations of polynucleotides, polypeptides and polysaccharides (Figure 1.1). 

Solid films have been examined frequently for infrared analysis in biochemical work, for example, in structural studies of proteins, polypeptides, and polysaccharides. Such films have been of particular value for studying polarization spectra of macromolecules in intact films and in oriented ones (stretched, rolled, or stroked), thereby permitting knowledge to be gained concerning spatial arrangements within the molecule and conformational effects among molecules. (See The Use of Polarized Infrared Radiation and the Measurement of Dichroism, p. 73, for a detailed discussion.) A few workers have discussed the film technique (Lecomte, 1948 Randall et al., 1949 Hacskaylo, 1954). 

A large number of water-soluble polymers are derived from biological sources. Termed hiopolymers, this class includes polynucleotides (qv), polypeptides and polysaccharides (qv). Becanse these polymers perform special biological functions, they have specific microstmctin-es and are often perfectly monodisperse. In the following section the general stmctural features of major biopolymer types will be reviewed as related to water solubility. 

There are two major classes of natural polymers used as scaffolds polypeptides and polysaccharides (Table 37.1, Figure 37.1). Natural polymers are typically biocompatible and enzymatically biodegradable. The main advantage for using natural polymers is that they contain bio-functional molecules that aid the attachment, proliferation, and differentiation of cells. However, disadvantages of natural polymers do exist. Depending upon the application, the previously mentioned enzymatic degradation may inhibit... 

Given the successfiil results in the biomineralization of both polypeptides and polysaccharides, a natural follow-up was the combination of both biopolymer types to tailor the mineralization process. Moreover, given the complex biological conditions imder which biosilicification occurs in plants, diatoms, and sponges, there is a strong possibility that proteins and polysaccharides coexist in the domains where biomineralization occurs. In this sense, the association of polysaccharides and proteins to control the mineralization processes appears to be not only a sensible approach but also a means to deepen the fundamental processes of biomineralization. 

Diez-Pascual, A. M., Wong, J. E. Effect of layer-by-layer confinement of polypeptides and polysaccharides onto thermoresponsive microgels A comparative study. J. Colloid Interf. Sci. 2010, 347, 79-89. 

---