Elastin like polypeptide (ELP) has interesting thermal behaviors. At room low te

Question

Elastin like polypeptide (ELP) has interesting thermal behaviors. At room low temperature, it is highly solubilized in the water, but it's precipitated out from the solution when it's heated up called inverse temperature transition (ITT). Here are the model ELP structures and their thermal behavior characterized by spectroscopy (Figure 2, where n=50). Using UV-Vis spectrophotometer, we obtained the following observation related to IIT of the ELP (Figure 5).

(a) Calculate the entropy and enthalpy values related to this thermal behaviors of poly (Ile-25) at pH7 and poly (Lys-25) at pH13 and 7.

(b) Calculate the percent of the protonated amino side chains of Lys at pH 7 and pH 13 (5). Explain why poly (Lys-25) have pH dependent thermal behaviors and explain why this phenomenon is reflected in the thermodynamic parameters that you calculated

Flexible Elastin Backbone H2N-I(Va-Pro-Gly-Val-Gly)(Val-Pro-Gly-Lys-Gly)ln CO2H Chemically reactive crosslinkable group NH3 Figure 2. Design of the repeat sequence of the cross-linkable elastin-mimetic protein polymer poly(Lys-25). In the repeat sequence of poly(Ile-25), an isoleucine residue replaces the lysine residue of poly(Lys-25)

Explanation / Answer

Elastin-like polypeptides (ELPs) have a distinctive thermal property, transition temperature (Tt), which leads to phase transition. This thermal property depends on the molecular weight (MW) of ELP, ELP concentration, composition of the amino acids constituting ELPs, and ionic strength of the aqueous solution. In order to investigate the effects of ELP length, ionic strength and existence of fusion protein, ELP genes of three different sizes were cloned using the recursive directional ligation (RDL) method and expressed in Escherichia coli. Following purification, thermal behaviors of ELPs were monitored using a spectrophotometer with temperature scanning. The results of our study indicated that Tt shifted to low in accordance with ELP length or increased ionic strength. Additionally, it was observed that Tt was affected by the physical properties of the protein fused with ELPs.

The temperature-dependent behavior of a solvated oligopeptide, GVG(VPGVG), is investigated. Spectroscopic measurements, thermodynamic measurements, and molecular dynamics simulations find that this elastinlike octapeptide behaves as a two-state system that undergoes an "inverse temperature" folding transition and reentrant unfolding close to the boiling point of water. A molecular picture of these processes is presented, emphasizing changes in the dynamics of hydrogen bonding at the protein/water interface and peptide backbone librational entropy.

AcidBase Interactions and Secondary Structures of Poly-l-Lysine Probed by 15 N and 13C Solid State NMR and Ab initio Model Calculations ..... The signals obtained below pH 7 and above pH 13 are sharp and exhibit line widths of less than 10 Hz. Between pH 9.2 and 11.4, line widths on the order of 30 Hz are observed

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