Differential scanning calorimetry studies of NaCl effect on the inverse temperature transition of some elastin‐based polytetra‐, polypenta‐, and polynonapeptides

Abstract

Differential scanning calorimetry studies of the effect of NaCl on protein-based polymer self-assembly has been carried out on six elastin-based synthetic sequential polypeptides--i.e., the polypentapeptide (L-Val1-L-Pro2-Gly3-L-Val4-Gly5)n and its more hydrophobic analogues (L-Leu1-L-Pro2-Gly3-L-Val4-Gly5)n and (L-Val1-L-Pro2-L-Ala3-L-Val4-Gly5)n; the polytetrapeptide (L-Val1-L-Pro2-Gly3-Gly4)n and its more hydrophobic analogue (L-Ile1-L-Pro2-Gly3-Gly4)n; and the polynonapeptide (a pentatetra hybrid), (L-Val1-L-Pro2-Gly3-L-Val4-Gly5-L-Val6-L-Pro7-Gly8-Gly9++ +)n. Previous physical characterizations of the polypentapeptides have demonstrated the occurrence of an inverse temperature transition since increase in order of the polypentapeptide, as the temperature is raised from below to above that of the transition, has been repeatedly observed using different physical characterizations. In the present experiments, it is observed that the transition temperatures of the polypeptides studied are linearly dependent on NaCl concentration. The molar effectiveness of NaCl in shifting the transition temperature delta Tm/[N], is about 14 degrees C/[N], with the dependence on peptide hydrophobicity being fairly small. Interestingly, however, the delta delta Q/[N] does depend on the hydrophobicity of a polypeptide.

The molecular basis of the temperature‐ and pH‐induced conformational transitions in elastin‐based peptides

“…1 Recently, elastin-derived polypeptides, represented by (VPGVG) n , have attracted much attention due to their potential uses in energy conversions, 2 as control-release drugs, 3 designing artificial vascular tissue, 4 and as building blocks for elastic biomolecular machines. 5 For example, Urry and co-workers have shown that one can modulate the transition temperature of a given elastin polymer by many physicochemical changes, such as pH, 6 pressure, 7 salt, 8 organic solutes, 6 and the oxidation state of a side-chain functional group. 5 Chilkoti and co-workers have devised a new way to thermally target polymer-drug conjugates to solid tumors, by exploiting the phase transition-induced aggregation of elastin-like polypeptides.…”

Fusion order controls expression level and activity of elastin‐like polypeptide fusion proteins

“…The inverse phase transition of ELPs can also be isothermally triggered by depressing their T t below solution temperature by the addition of kosmotropes from the Hofmeister series. [8][9][10][11] At the molecular design level, the T t of an ELP can be tuned by two orthogonal parameters: the identity and mole fraction of the ''guest'' residue in the fourth position (Xaa), and the chain length of the ELP; recombinant synthesis provides complete control over these two variables, so that its is possible to synthesize ELPs with exquisite control of their T t , which is important for different applications of these stimulus responsive polypeptides. 12,13 We discovered that the phase transition behavior of ELPs is retained when ELPs are fused to soluble proteins, 1 and we exploited this observation to develop a non-chromatographic method-ITC-for purification of recombinant proteins.…”

Physics of engineered protein hydrogels

“…4). 101 Adding salts usually lowers the solubility of ELPs 91,102 according to the Hofmeister series, providing the opportunity to use ELP tags in nonchromatography protein purification by using inverse transition cycling. 103 Similar to synthetic polymers exhibiting LCST and consistent with the Flory-Huggins theory of polymer solutions, ELPs with a larger molecular weight have a lower T t .…”