Elastic-contractile protein

For our model elastic-contractile proteins in water, a plot of heat absorbed on increasing temperature exhibits an abrupt rise and then a more gradual decline as the temperature reaches the start of and passes through the tran-... 

Due to the struggle to survive under circumstances of limited food supply, organisms evolve to use the most efficient mechanism available to their composition. The most efficient mechanism available to the proteins that sustain Life would seem to be the apolar-polar repulsive free energy of hydration as observed for the inverse temperature transitions for hydrophobic association. The efficiency of designed elastic-contractile protein-based machines and a number of additional properties make designed protein-based materials of substantial promise for the marketplace of the future. 

A brief description of the chemical synthesis of elastic-contractile proteins immediately follows in the context of the general message of the chemical synthesis of natiural biological products. 

V in Table 5.5 with 0,2,3,4, and 5 F residues per 30-mer exhibits a systematic nonlinear increase in steepness, that is, in positive cooperativity, and an associated nonlinear increased pKa shift, as plotted in Figure 5.34. The energy required to convert from the COOH state to the COO" state systematically in a supralinear way becomes less and less, as more Phe residues replace Val residues. The energy required to convert from the hydrophobically dissociated state of COO" to the hydrophobically associated (contracted) state of COOH becomes less, as the model protein becomes more hydro-phobic. The elastic-contractile protein-based machine becomes more efficient as it becomes more hydrophobic. The cooperativity of Model Protein iv with a Hill coefficient of 2.6 is similar... 

The Design of Poised Elastic-Contractile Protein-based Machines... 

Mammalian muscle acts as though it is poised for hydrophobic association at room temperature much as is the (GVGVP) elastic-contractile protein-based polymer on which are based the visually demonstrated contractions reviewed in Chapter 5. 

Accordingly, the perspectives in Chapter 5, developed on elastic-contractile protein-based polymers, introduce new concepts into the functional description of biology s protein-based machines. As with the introductory comments in Chapter 7, the footnote relevant to reactions toward new concepts in science is repeated here in footnote form. ... 

At the level of the myofibril, the addition of calcium ion, the lowering of pH, and stretching have each been shown to activate muscle contraction as well as to drive contraction of suitably designed elastic contractile protein-based polymers by hydrophobic association (see more extensive discussion in Chapter 7). 

Figure 9.5. Elastic-contractile protein material, (GVGVPlai, obtained by phase separation from the ruptured E. coli cells of a single fermentation run. (A) Note taffy-like appearance of the mass of product. (B) Viscoelastic mass being pulled into a fine strand. (Courtesy of Bioelastics Research, Ltd.)...

Figure 9.8. Purification by phase separation of the elastic-contractile protein-based polymer (GVGIPjjec (Top) Pancake formed on phase separation. (Bottom) Stretching of the robust viscoelastic pancake out to a length of about 1 meter. (Courtesy of Bioelastics Research, Ltd.)...

A.5.4 Nanoparticles Composed of a Hydrophobic Series of Charged Elastic-contractile Protein-based Polymers... 

The difference between the contractile protein of the models and that of muscle becomes even greater if one attributes the elastic resistance of resting living muscle entirely to the sarcolemma and the connective tissue (Ramsey and Street, 1940, 1941 A. V. Hill, 1949a, 1950a). The con-... 

The mechanism by which ATP affects the elasticity and activity of the contractile proteins can be investigated in two ways ... 

A diverse set of energy conversions that sustain life can be experimentally demonstrated by de novo design of elastic-contractile model proteins under the precept of a single, pervasive, mechanism, that is, by a consilient mechanism that creates a common groundwork of explanation. It is a mechanism that achieves function by controlling association of... 

Based on a series of designed elastic-contractile model proteins. Figure 1.2 exhibits a family of curves whereby stepwise linear increases in oil-like character give rise to supra-linear increases in curve steepness, that is, in positive cooperativity. More oil-like phenylalanine (Phe, F) residues with the side chain -CH2-C6H5 replace less oil-like valine (Val, V) residues with the side chain -CH-(CH3)2. Here the structural symmetry is translational with as many as 42 repeats (Model protein v) of the basic 30-residue sequence, and the structure is designed beginning with a repeating five-residue sequence of a fibrous protein, the mam-mahan elastic fiber. 

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.

Most significantly, however, the molecular basis for positive cooperativity and the result of increased functional efficiency in designed elastic-contractile model proteins has been experimentally determined to be the competition for water that occurs between oil-like domains and charged groups constrained to coexist within a protein structure (see immediately below and Chapter 5, section 5.1.7.4). This represents the principal statement of the Mechanistic Assertion. 

Figure 1.7. Shown are the first reported data of the conversion by an elastic-contractile model protein of chemical energy due to an increase in concentration of acid into the mechanical work of contraction. A Length changes at constant force (isotonic contraction) in phosphate-buffered saline. B Force changes at constant length (isometric contraction) in phosphate-buffered saline. (Reproduced from Urry et al. )...

Figure 2.4. The lefthand side shows a representative sheet of y-irradiation cross-linked elastic-contractile model protein, designed for the conversion of an input energy into the output of pumping iron, per-...

Figure 2.6. In general, the conversion from the extended state to the contracted state shown in Figure 2.5 is graphed here as a systematic family of sigmoid-shaped curves with a common dependence of oil-like character of the elastic-contractile model protein whether the energy input is thermal, chemi-...

The sigmoid-shaped curves of Figure 2.6A represent the shortening of contraction that occurs on raising the temperature through the relevant temperature interval for the particular extent of oil-like character of the model protein. Elastic-contractile model proteins of more oillike composition contract at lower temperatures and over narrower temperature intervals. 

In general, the key chemicals for changing the folding temperature in our elastic-contractile model proteins are prevalent triggers of function in biology. 

Synthetic Elastic-contractile Model Protein Machines to Energize Phosphates... 

Ec(uivalence of Energy Conversion to Biology s Proteins yet Structural Limitations of Elastic-contractile Model Proteins... 

Much fundamental science came from the study of elastic-contractile model proteins. The elastic-contractile model proteins provided the molecular system for realizing the correct description of elasticity. Furthermore, competition for hydration between oil-like and polar. 

Figure 2.18. Energies are shown that can be inter-converted by means of elastic-contractile model proteins capable of exhibiting inverse temperature transitions functioning by means of the competition for hydration between oil-like and charged groups called an apolar-polar repulsive free energy of hydration. See Chapter 5 for a more complete development of the phenomenology and physical basis and Chapter 8 for details of the molecular process.

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