Elastic protein-based polymers

Urry DW. Physical chemistry of biological free energy transduction as demonstrated by elastic protein-based polymers. J Phys Chem B 1997 101 11007-11028. 

Table 1. Hydrophobicity scale for protein-based polymers and proteins based on the properties of the inverse temperature transition of elastic protein-based polymers, poly[/v(GVGVP), (GXGVP)]. ...

Therefore, TMDSC has been demonstrated to be an effective method to split the overlapping phenomena present in the ITT of elastic protein-based polymers. By tuning the frequency of the periodic component, a maximum split can be achieved that shows an exothermic contribution arising from the Van der Waals contacts attending chain folding and assembly, and an endothermic contribution associated with loss of hydrophobic hydration, the... 

Figure 1.3. A Hill plot of the set of designed elastic-contractile model proteins shown in Figure 1.2 with Hill coefficients, n, ranging from 1.5 to 8.0. B Hill plot of myoglobin (n = 1) and hemoglobin (n = 2.8). It is shown that the vaunted hemoglobin positive cooperativity is relatively small compared with that of designed elastic protein-based polymers and, in particular, of designed Model protein v.

D.W. Urry, Physical Chemistry of Biological Free Energy Transduction as Demonstrated by Elastic Protein-based Polymers, invited Feature Article, J. Phys. Chem. B, 101, 11007-11028, 1997. 

It has now been possible to stretch a single elastic protein-based polymer chain and to obtain a uniformly increasing force versus extension curve.This was done with a surprisingly simple device called an atomic force microscope, the development of which resulted in the Nobel prize for Paul Hansma. The performance of the mechanical work of lifting a weight, shown in... 

D.W. Urry, L.C. Hayes, D. Channe Gowda, S.Q. Peng, and N. Jing, Electrochemical Transduction in Elastic Protein-based Polymers. Biochem. Biophys. Res. Commun., 210, 1031-1039,1995. 

The phase separated state of the parent elastic protein-based polymer, (GVGVP) , at 37° C is about 50% polymer and 50% water by weight. This was the composition for the transitions represented in Figure 5.2. On exposure of this state to 20 Mrad of y-irradiation, a nearly ideal elastic band forms with properties similar to those of the major elastic arteries. On lowering the temperature to 25° C or below, the elastic band swells and increases its volume 10-fold. A return to body temperature, 37° C (98.6° F),... 

Low frequency mechanical resonances within elastic protein-based polymers occur near 3 kHz (within the frequency range of sound absorption) and 5 MHz (near radio frequencies). 

Obviously, the effect of raising the temperature of a loaded, cross-linked elastic band composed of elastic protein-based polymers of the poly(GVGVP) family is to drive hydrophobic association with the consequence of lifting of the attached weight. How does this combine with the above understanding of elasticity to perform mechanical work ... 

The absorption in the microwave region at 5 GHz, as will be discussed below, is due to hydrophobic hydration. Putting in energy of this frequency ought to be the most effective way to heat the elastic protein-based polymer and drive contraction. Another intense absorption occurs near 5 MHz that is due to the internal chain motions of the protein backbone. It is the damping of these motions on stretching that is the source of the entropic component of the... 

Concepts Introduced During Development of Elastic Protein-based Polymers for Free... 

D.W. Urry,J.Xu,W.Wang, L. Hayes,F. Prochazka, and T.M. Parker, Development of Elastic Protein-based Polymers as Materials for Acoustic Absorption. Mat. Res. Soc. Symp. Proc. Materials Inspired by Biology, 774,81-92,2003. 

L. Hayes, Effect of Hydrophobicity of Elastic Protein-based Polymers on Redox Potential. Ph.D. Dissertation, University of Alabama, Birmingham, 1998. 

Muscle and Cross-linked Elastic Protein-based Polymer, (GVGVP) , Contract on Raising the Temperature over the Same Temperature Range... 

An advantage of using elastic protein-based polymers as scaffoldings for soft tissue restoration as discussed in Chapter 9 would be to overcome the problem of infectious prions. 

Raising the temperature to drive contraction by hydrophobic association is the fundamental property of the consilient mechanism as demonstrated in Chapter 5 by means of designed elastic-contractile model proteins. Thermal activation of muscle contraction also correlates with contraction by hydrophobic association, but assisted in this case by the thermal instability of phosphoanhydride bonds associated with ATP, which on breakdown most dramatically drive hydrophobic association. In particular, both muscle and cross-linked elastic protein-based polymer, (GVGVP) contract on raising... 

Finally, for medical applications, the extraordinary biocompatibility of these elastic protein-based materials, we believe, arises from the specific means whereby these elastic protein-based polymers exhibit their motion. Being composed of repeating peptide sequences that order into regular, nonrandom, dynamic structures, these elastic protein-based polymers exhibit mechanical resonances that present barriers to the approach of antibodies as required to be identified as foreign. In addition, we also believe that these mechanical resonances result in extraordinary absorption properties in the acoustic frequency range. 

In general, development of the scientific foundation for protein-based polymers began in an academic setting and continued very effectively in a company setting. The primary funding impetus (the enabler) for the development of elastic protein-based polymers has been grants... 

As introduced in Chapter 1, the present chapter constitutes Assertion 4 The Applications Assertion of the book. Production and purification are first addressed, as they obviously make up the initial enabling steps in moving toward applications of any materials. The most surefooted path toward materials applications of protein-based polymers, however, intertwines issues of production and purification through a combination of the two methods of preparation—chemical synthesis and biosynthesis. Chemical synthesis proved the biocompatibility of elastic protein-based polymers and therefore opened the door to medical applications. Demonstration of the biocompatibility of the chemically synthesized product made clear the purification required of elastic protein-based polymers produced by E. coli if unlimited medical applications were to be possible. Chemical synthesis also provided a faster route to diverse polymer compositions, which allowed... 

Figure 9.1. Diagram showing the approach whereby recombinant DNA technology was used to construct monomer and multi-mer genes for expression of the elastic protein-based polymer [(GVGVP)io]n(GVGVP). (Reproduced with permission from Woods. )...

For production by E. coli there is an important issue of the removal of E. coli toxic proteins, particularly, because all animals have abundant antibodies against E. coli antigens. Because poly(GVGVP) has been chemically synthesized and adequately purified, it was established that these elastic protein-based polymers exhibited extraordinary biocompatibility. This awareness provided the impetus for the necessary levels of purification when using E. cofi-produced protein-based polymers, as discussed below. 

Efforts to produce elastic protein-based polymers include using tobacco, - mushrooms, yeast,and the seeds of arabidopsis, canola, and soy. ° Production in tobacco plants has the potential of providing a healthful product from a plant that is the source of much illness, as such tobacco farms could be viewed as a capacity... 

Only because the remarkable biocompatibility of chemically synthesized poly(GVGVP) was already known was there adequate impetus to purify microbially prepared (GVGVP)2si. Otherwise, it would have been presumed, as had been widely expected, that the toxicity of inadequately purified (GVGVP)25i was an inherent property of the protein-based polymer. To be left in such a state of misunderstanding would have meant that the dramatic potential of elastic protein-based polymers for use in medical applications would be neither appreciated nor realized. The inflammatory response elicited by an inadequately purifled biosynthetic elastic protein-based polymer would have overwhelmed most considered medical applications. 

The advent of recombinant DNA technology, two decades after the remarkable Merrifield advance, has overtaken many of the advantages of the Merrifield approach. After the time-consuming gene construction and development of a good expression system, large quantities of elastic protein-based polymers are produced in a short time, as shown in Figure 9.5. 

S.3 Response of Human Monocytes to Elastic Protein-based Polymers... 

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