Oil-like character

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. 

Stepwise increases in oil-like character, as when the mildly oil-like Val (V) residue is replaced by the very oil-like Phe (F) residue, cause the add-base titration curves to be shifted to higher pH values and to be steeper. The energy required to drive the model protein from the phase separated, contracted state to the swollen, relaxed state is proportional to the width of the curve, that is, inversely proportional to the steepness of the curve. Accordingly, the model protein with the steepest curve exhibits the most efficient function for performing the work of lifting a weight. 

The Fi-motor structure due to the Walker groups functions ideally to demonstrate the steps whereby the rotating cusp of insolubility would result in the synthesis of ATP. The y-rotor may be represented by the relative oil-like character of its three faces that are calculated in Chapter 8, section S.4.4.3, shown in Figures 8.31 to 8.33, and listed in Table 8.2. As represented in Figure 1.8, there is a very oil-like face (marked by -20 and shown directed toward the empty catalytic site), a neutral face (indicated by 0 and directed toward the P-ADP-t-P site), and a relatively vinegar-like face (indicated by -1-9 and directed toward the site indicated in Figure 1.8 as occupied by P-ADP). 

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. 

Increasing Oil-like Character Lowers Transition Temperature... 

As represented in Figure 2.6C, reduction of a more polar oxidized group attached to the model protein drives contraction. For more oillike model proteins, the affinity for electrons is greater, as in curve a, and reduction requires less electrical energy due to the steeper curve. More oil-like model proteins require less electrical energy to drive contraction. Furthermore, reduction of a group attached to a model protein increases the oil-like character of the model protein, because reduction lowers the temperature at which contraction occurs, as shown in Figure 2.6A. 

Figure 2.13. Shown is one complete cycle of the Fj-motor of ATP synthase on filling all catalytic sites with nucleotide and with a y-rotor that has three faces of very different hydrophobicities, that is, of very different oil-like character. As discussed in Chapter 8, the relative oil-like character of the three faces compare as -20kcal/mol-face for the most oillike, -i-Okcal/mol-face for an essentially neutral face, and h-9 kcal/mol-face for the least oil-like face. The least oil-like face would allow ADP and Pi to enter the catalytic site. As the Fo-motor rotates the darkened, oil-like face of the rotor toward the catalytic site containing ADP plus Pi, the repulsion between...

Moving the T,-divide by a Bound Chromophore That Changes Its Oil-like Character on Absorbing Light... 

Impact of the Relative Oil-like Character of Functional Groups of Proteins on the T,-divide... 

The relative oil-like character of each amino acid residue is given in terms of the Tt-based hydrophobicity scale in Table 5.1. T, is measured by plotting as indicated in Figure 5.9 and the technical term for oil-like, hydrophobic (meaning water fearing), is used. The more commonly used technical term, hydrophobicity, replaces the equivalent statement of oil-like character. 

Axiom 1 The change in temperature interval, over which occurs the oil-like folding and assembly transition of a host model protein on introduction of different guest substituents, becomes a functional measure of relative oil-like character of the substituents, that is, of their relative hydrophobicity, and it provides a measure of the change in free energy of the hydrophobi-cally associated state. 

Any interaction of light that causes a change in the oil-like character of the model protein will change the value of T, and hence will change... 

Pumping Iron by Using Light to Change the Oil-like Character of a Chromophore Attached to the Model Protein... 

Each State of a Functional Group Couples to the States of Another Functional Group by Contributing to and Being Affected by the Oil-like Character of the Polymer... 

Hydrophobicity (Degree of Oil-like Character) Positions Transition Zone... 

Changing the Oil-like Character by Progressive Addition of More Oil-like Phe Groups Moves the Temperature Interval (Transition Zone) to Lower Temperatures... 

When the transition zone is specifically the temperature interval, any change in oil-like character of the model protein-based machine moves... 

A Changing the Oil-like Character of a Model Protein by Any Energy Input, %, That Moves the Transition Zone Can Be Used to Change the Energy of a Functional Group That Is Also Capable of Changing the Oil-like Character of the Model Protein... 

Change in the Hydrophobicity (Extent of Oil-like Character) Due to Action on One Functional Group, for Example, Reduction of Oxidized N-methyl Nicotinamide, Moves the Transition Zone for a Second Functional Group, for Example, the Carboxyl/Carboxylate Chemical Couple Electro Chemical Transduction... 

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