Polypeptide materials

Researchers studying polypeptide and polypeptide hybrid systems have also processed vesicles using two solvents. This method usually involves a common organic solvent that solubilizes both blocks and an aqueous solvent that solublizes only the hydrophilic block. The two solvents can be mixed with the polypeptide or polypeptide hybrid system at the same time or added sequentially. The choice of organic solvent depends heavily upon the properties of the polypeptide material, and commonly used solvents include dimethylformamide (DMF) [46, 59], methanol (MeOH) [49], dimethyl sulfoxide (DMSO) [50, 72], and tetrahydrofuran (THF) [44, 55]. Vesicles are usually formed when the organic solvent is slowly replaced with an aqueous solution via dialysis or removed through evaporation however, some vesicles have been reported to be present in the organic/aqueous mixture [49]. 

The Jing group investigated their poly(L-lysine)-6-poly(L-phenylalanine) vesicles for the development of synthetic blood, since PEG-lipid vesicles were previously used to encapsulate hemoglobin to protect it from oxidation and to increase circulation time. They extended this concept and demonstrated that functional hemoglobin could be encapsulated into their vesicles. The same polypeptide material was also used to complex DNA, which caused the vesicles to lose their... 

Panitch et al. (1997) produced impressive yields of 700 mg/L by E. coli fermentation of a simple small artificial protein comprising 60 repeats of an (AG)4 motif with 23 and 33 amino acid N- and C-terminal fusions, respectively. The (AG)240 repeat units were not separated after expression, and the fusion sequences comprised just 10% of the whole fusion protein. This meant that loss of polypeptide material due to inefficient cleavage by... 

As scientists and engineers, natural self-assembly processes represent a tremendous resource, which we can use to create our own miniature materials and devices. Our endeavors are informed by hundreds of years of curiosity-driven research interested in the natural world. Our toolbox is further expanded by modem synthetic chemistry which extends beyond the realm of natural molecules. We can also create artificial environments to control and direct assembly and use computer-based tools and simulations to model and predict self-assembly pathways and their resulting protein structures. Many researchers believe we can use these modern tools to simplify, improve, and refine assembly processes. We have much to do in order to reach this ambitious goal but the next 10 years are likely to be filled with exciting discoveries and advances as self-assembling polypeptide materials move from the laboratory to the clinic or the manufacturing assembly line. 

Reliable circular dichroism spectra cannot be obtained from crystalline, oriented polypeptide material that is birefringent or scatters light. However, monolayers of protein do not appear to provide anomalous spectra (4,15), probably because of the relative uniformity of the film and the minimal refractive index increment at the protein/water interface. Nevertheless, previous results from this and other laboratories (3,16,17) have shown that albumin and fibrinogen molecules tend to lie flat, that is, with their long axes parallel to the surface, whereas globulins lie perpendicular to the surface. 

Over the past few decades, increasing attentirm has been paid to synthetic polypeptide materials, including their syntheses, properties, and applications [1-14]. Polypeptides are derived from amino acids and their deilvates. The continuing interest in polypeptides is mainly stimulated by their close relationship with proteins. Polypeptides can be used as a model system for protein research. Learning from natural proteins, polypeptides with diverse structures and functionalities have been widely synthesized and studied. The biorelated applications of the polypeptides and their assemblies are active topics of current research. 

Deming TJ (1997) Polypeptide materials new synthetic methods and applications. Adv Mater 9 299-311... 

Polypeptide Materials Based on other Naturally Occurring or De Novo Designed Self-Assembling Domains such as Coiled Coils... 

Despite the foregoing evidence, the type-II p-tum has not been unequivocally established as the determinative element for the development of elastomeric behavior within the elastomeric domains of elastin and other native polypeptide materials. Spectroscopic analyses of native elastin and elastin-mimetic polypeptides have provided strong evidence for the presence of alternative conformations, particularly above the inverse transition temperature, which may contribute to the elastomeric behavior of the material in its coacervate state. In addition, the elastomeric domains of native tropoelastin display quite substantial sequence diversity, although it appears that Pro-Gly sequences are conserved... 

Deming, T.J. (1997) Polypeptide materials New synthetic methods and appUcations. Advanced Materials, 9,299. 

Other types of chemical polypeptide modification include the addition of nonionic, polar groups to increase solubility and blood circulation lifetime, addition of mesogenic groups, addition of linker groups to allow efficient functionalization of preformed polypeptides by click reactions, and the addition of sugars. Increasing bioavailability and biofunctionality are major goals for development of useful synthetic polypeptide materials. 

Gramicidin, tyrocidine, and gramicidin S are synthesized by strains of Bacillus brevis. The original culture used by Dubos (1939) for production of the first two of the three polypeptides was designated BG and is now hsted as ATCC8185. Of six substrains of BG obtained by colony selection, two were found to produce more than twice the quantity of active polypeptide materials than the wild strain and one to form no active substances whatsoever (Appleby... 

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