Elastic protein-based polymers frequency

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... 

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). 

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... 

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. 

The Presence of Low Frequency Mechanical Resonances in Elastic Protein-based Polymers... 

Now, it has been shown for materials such as poly(propylene diol) (wherein both the absorption maximum for loss shear modulus and loss permittivity overlap near the frequency of IHz) that their normalized curves perfectly superimpose over their frequency band width. - As shown in Figure 9.15, the lower frequency loss shear modulus curves uniquely overlap with the loss permittivity data at higher frequency. As such the former is melded to calibrate the loss permittivity data to obtain a coarse estimate of the elastic modulus values. This provides an independent demonstration of the mechanic il resonance near 3 kHz and also allows reference to the 5 MHz dielectric relaxation as a mechanical resonance. Thus, as the folding and assembly of the elastic protein-based polymers proceed through the phase (inverse temperature) transition, the pentamers wrap up into a structurally repeating helical arrangement like that represented in Figure 9.17. 

The low-frequency motions of 5 MHz and 3 kHz lower the free energy of the folded and assembled structure of the elastic protein-based polymers. A coarse sense of the amount each mechanical resonance could be contributing to the stability of the structure of these elastic protein-based polymers is obtained from a plot of the logarithm of the frequency as a function of the entropy contribution of resonance frequency using the harmonic oscillator partition function. It is not expected that the harmonic oscillator would give an accurate measurement of the magnitude of the entropy contribution of such low-frequency motions. However, the use of the harmonic oscillator partition function provides a sense of direction and magnitude of the contribution of low-frequency motions to... 

Two basic components comprise the nanosensor of interest here (1) the atomic force microscope (AFM) designed to measme force as a function of extension or further modified to assess frequency dependence of loss shear modulus under isometric conditions and (2) the sensing element of elastic protein-based polymer containing a site or sites of interaction wherein the interaction changes the state of hydrophobic association by means of the apolar-polar repulsive free energy of hydration, AGap. 

On the other hand certain elastic protein-based polymers can exhibit good elastic moduli and yet contain dynamic structural regularities that exhibit mechanical modes. In fact elastic protein-based polymers can be designed to exhibit mechanical resonances with high loss factors over interesting frequency ranges. 

A coarse calibration of the higher frequency loss permittivity data becomes possible by using the overlap with the loss shear modulus values. It seems reasonable to conclude that the loss shear modulus values would reach 5 x 10 Pa or more near 3 kHz. The comparison also suggests that the intensity of the peak in Figure 1A would almost double on continuing from 20 to 40 C. It should also be appreciated that the composition of the elastic protein-based polymer can be chosen such that the temperature interval is below 5 C in which case the intense absorption would exist at temperatures above 5 C. 

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