Formation of Protein-based Materials

Several steps are reqnired to form a protein network  

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In order to be able to describe and predict changes in the physical-chemical properties of proteins during dry processing according to temperature and RH, it is essential to construct the state diagram relative to the water (or plasticiser) content [3,174]. Figure 11.7 shows the different steps involved in the formation of protein-based materials using the dry process [13,136,152,175] ... 

Plasticizers are generally required for the formation of protein-based materials (] 1,14-18). These agents modify the raw material formation conditions and the functional properties of these protein-based materials (i.e. a decrease in resistance, rigidity and barrier properties and an increase in flexibility and maximal elongation of the materials). Polyols (e.g. glycerol and sorbitol), amines (e.g. tri-ethanolamine) and organic acids (e.g. lactic acid) are the most common plasticizers for such applications. Completely or partially water insoluble amphipolar plasticizers such as short-chain fatty acids (e.g. octanoic acid) can be used since some protein chain domains are markedly apolar. 

It is essential to determine the phase equilibrium patterns (Figure 1) of protein-based materials according to the moisture (or plasticizer) contents in order to be able to control the material formation conditions and predict variations in the properties of the end products under different usage conditions (temperature and relative humidity) 6,10,19JO),... 

Surfactants at Interfaces. Somewhat surprisingly, the successes described above in the in-situ studies of protein adsorption have not inspired extensive applications to the study of the adsorption of surfactants. The common materials used in the fabrication of IREs, thalliumbromoiodide, zinc selenide, germanium and silicon do, in fact, offer quite a range in adsorption substrate properties, and the potential of employing a thin layer of a substance as a modifier of the IRE surface which is presented to a surfactant solution has also been examined in the studies of proteins. Based on the appearance of the studies described below, and recent concerns about the kinetics of formation of self-assembled layers, (108) it seems likely that in-situ ATR studies of small molecules at solid - liquid interfaces ("wet" solids), will continue to expand in scope. 

These and other obstacles to the RNA world have led to the suggestion that some other genetic material preceded RNA and DNA. One possibility is a peptide-like RNA analog. A simple coding system could also have been used, e.g. one based on only two bases, such as C and G, instead of four. - Perhaps it is more probable that formation of proteins and the present coding system evolved... 

Furthermore, patients with spinal cord injuries have a high incidence of pressure ulcers and is a population that reaches beyond nursing homes and hospitals. It has been reported that 40% of this group develops pressure ulcers during initial hospitalization and rehabilitation. In fact, all populations dependent on assistive devices where soft tissue is compressed between a bony prominence and the assistive device are at increased risk for pres-sure ulcer formation. Again as discussed below, elastic protein-based materials are being tested in an appropriate animal model, and preliminary results are promising. 

The mechanisms whereby the materials function are common to the tissue to be restored, that is, they exhibit the same hydrophobic association as occurs in protein structure formation and function, and the elasticity is due to damping of internal chain dynamics rather than due to random chain networks. As protein function itself is central to cellular function, this allows elastic protein-based materials in concert with natural cells to achieve tissue restoration in a manner entirely coherent with fundamental relationships between cells and their natural extracellular matrix. 

Colorimetric assays are appropriate methods to investigate protein interactions with cationic polysaccharide materials. However, these assays cannot differentiate between different types of interactions, i.e. adsorption and absorption of proteins. Among these, the bicinchoninic acid assay (BCA) is widely used since it allows an easy determination of the total amount of adsorbed proteins on bulk materials." The assay is based on the reduction of Cu to Cu in a reductive environment in the presence of proteins. The BCA chelates Cu, forming a colored complex whose absorption band at 562 nm can be related to the amount of adsorbed proteins on the materials. Using this method, it has been demonstrated that the incorporation of inorganic materials such as hydroxyapatite (HAP) or nano-HAP into chitosan-based materials leads to the formation of protein-rich layers at the... 

The formation of a 3D network stabilised by new interactions or bonds, after removal of the intermolecular bond scission agent. Two different technological strategies can be used to make protein-based materials the wet process or solvent process involving a protein solution or dispersion, and the dry process or thermoplastic process using the thermoplastic properties of the proteins under low-hydration conditions (Figure 11.4). 

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