Polymers, biological proteins

Proteins are nature s polyamide condensation polymers. A protein is formed by polymerization of o-artiino acids, with the amino group on the carbon atom next to the carboxylic acid. Biologists call the bond formed a peptide rather than an amide. In the food chain these amino acids are continuously hydrolyzed and polymerized back into polymers, which the host can use in its tissues. These polymerization and depolymerization reactions in biological systems are all controlled by enzyme catalysts that produce extreme selectivity to the desired proteins. 

Taylor A. McCarty received her BA in biology and chemistry from SUNY Potsdam in 2003. She recently obtained her PhD in analyhcal chemistry from the University at Buffalo under the supervision of Dr. Frank Bright, where she is now the lab manager. Her research interests include the behavior of macromolecules such as polymers and proteins dissolved in environment-friendly solvent systems. 

Soft ionization techniques such as electrospray ionization and matrix assisted laser desorption are now routinely used to determine the mass of large hydrophilic polymers like proteins (27). However, as is usual for the ionization process, the presence of sails and detergents, which is common for biological samples, can affect the process significantly. The use of the on-line capillary reversed-phase HPLC in combination of the electrospray mass spectrometer (LC/MS) has made it possible to analyze such samples directly (10,16, 28). When GAP-43 isolated from the membrane fractions of bovine brain was analyzed, a single major peak with a minor peak corresponding to a phosphorylated species was observed (Fig. la). To study the posttranslational modifications in detail, the protein was digested with specific proteases such as lysyl... 

Finally, the diversity of the bulk properties of proteins is unequaled in any other known polymer class. Proteins form materials as diverse as the hard substance of nails and hair, the transparent substance of the lens, the elastic substance of collagen, and so on. Some of tliese properties are equaled by polymers in other classes keratin by the carbohydrate polymer chitin (A-acyl-o-glucosamine), the transparency of the lens proteins by the polymer Perspex (polymethyl methacrylate), the toughness and elasticity of collagen by the polyamide nylon. But no single polymer class has demonstrated such a variety of diverse bulk properties. The compaction of so many diverse bulk properties into one polymer class, polypeptides composed of the twenty proteinaceous amino acids, obviously contributes greatly to their biological fitness. 

DHA works because of a reaction between its carbonyl group and a free amino group (—NH3+) of several amino adds in the skin protein keratin. Amino adds are the building blocks of the biological polymers called proteins (Chapter 19) keratin is just one such protein. The DHA produces brown-colored compounds called melanoids when it bonds to the keratins. These polymeric melanoids are chemically linked to cells of the stratum corneum, the dead, outermost layer of the skin. DHA does not penetrate this outer layer so the chemical reaction that causes tanning only affects the stratum corneum. As this dead skin sloughs off, so does your tan ... 

A number of polymer systems were tested for tissue biocompatibility and release kinetics. The best long-term release results were obtained with hydrophobic polymers. Examples included non-degradable ethylene-vinyl acetate or biodegradable polylactic acid. Certain hydrogels such as polyhy-droxyethylmethacrylate or polyvinylalcohol also worked effectively, but released proteins for shorter time periods. With the hydrophobic polymers, biologically active protein was released for more than 100 days (2). In other tests, larger molecules (2 million MW), such as polysaccharides and polynucleotides, were also successfully released for long time periods (2). 

Quantum dots (QDs) are semiconductor nanocrystals with unique and size-dependent electronic and fluorescent properties. The properties of QDs have sparked interest in many commercial applications, including computing, photovoltaic cells, and biological labeling. CdSe QDs are the most common type of QDs considered for use in biological applications. The CdSe core is often surrounded by another semiconductor shell, such as ZnS, to enhance emission properties. The shell of QDs can be capped with functionalized thiol molecules to make them water soluble and may be additionally coated with polymer or protein coatings to make them biologically compatible. 

Industrial commodity polymers are the backbone of the world chemical industry and provide extreme value and stability that are appropriate for a plethora of applications. Their ease of synthesis enables the utilization of a large number of chemical functionalities that influence their final properties, but with relatively little control over 3D polymer shape on the molecular scale. By contrast, biological polymers, primarily proteins, feature a relatively small pool of chemical functionalities, yet their molecular stmctures can be almost infinitely custom-tailored for specific applications. However, biomacromolecules are orders of magnitude more expensive to produce and generally display much poorer stability in harsh conditions, and thus are limited, essentially, to medical and biotechnology applications. ... 

Figm 35 Synthetic-biological hybrid polymers exhibit the potential to realize complex function in synthetic polymer systems. (Protein stmcture was reproduced from PDB source ID 1AB9.)... 

Surfactants constitute some of the most important (in terms of function, not quantity) ingredients in cosmetic and toiletry products, foods, coatings, pharmaceuticals, and many other systems of wide economic and technological importance. In many, if not most, of those applications, polymeric materials, either natural or synthetic, are present in the final product formulations or are present in the targets for their use. Other surfactant applications, especially in the medical and biological fields, also potentially involve the interaction of polymers (including proteins, nucleosides, etc.) with surfactant system. 

Based on the DLS measurements it is possible to find particle size distributions of polymers and proteins, particle aggregation phenomena, micellar systems and their stability, micro-emulsion technology, colloid behaviour, nucleation processes and protein crystallization. DLS is a non-destructive and convenient method and so it can find application in various branches of science. In chemistry it finds application in topics of colloids, polymers, emulsions, suspensions, nanoparticles, and in physics, applications such as in astrophysics and atmosphere physics and in biology it involves biophysics and biomedicine applications. 

Polymer molecules, which by their mere size belong to the colloid family, are described in Chapter 12. Special attention is paid to polymer-solvent interaction and its influence on the structure adopted by polymer molecules. Proteins are a special class of biopolymers. Because of their central role in biological systems, a full chapter (Chapter 13) is dedicated to describing their three-dimensional structure and structure stability in an aqueous environment. It is shown that the compact structures of globular protein molecules is the result of intramolecular self-assembly. 

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