Circular dichroism and UV‐resonance Raman investigation of the temperature dependence of the conformations of linear and cyclic elastin

Ahmed, Zeeshan; Scaffidi, Jonathan; Asher, Sanford A.

doi:10.1002/bip.21081

Cited by 16 publications

(24 citation statements)

References 88 publications

(152 reference statements)

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“…This VPT is similar to the “inverse temperature transition” of elastin-like peptides that undergo well-known transitions from an extended, highly mobile conformation to a collapsed molten globule-like conformation at higher temperatures 37–41. This VPT of PNIPAM and elastin-like peptides is related to the cold-denaturation42–48 phenomenon observed in proteins such as myoglobin.…”

Section: Introductionsupporting

confidence: 62%

UV Resonance Raman Determination of Molecular Mechanism of Poly(N-isopropylacrylamide) Volume Phase Transition

et al. 2009

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Poly (N-isopropylacrylamide) (PNIPAM) is the premier example of a macromolecule that undergoes a hydrophobic collapse when heated above its lower critical solution temperature (LCST). Here we utilize, dynamic light scattering, H-NMR, steady-state and time-resolved UVRR measurements to determine the molecular mechanism of PNIPAM's hydrophobic collapse. Our steady-state results indicate that in the collapsed state the amide bonds of PNIPAM do not engage in inter-amide hydrogen bonding, but are hydrogen bonded to water molecules. At low temperatures, the amide bonds of PNIPAM are predominantly fully water hydrogen bonded, whereas, in the collapsed state one of the two normal C=O hydrogen bonds is lost. The NH-water hydrogen bonding, however, remains unperturbed by the PNIPAM collapse. Our kinetic results indicate a mono-exponential collapse with τ~360 (±85) ns. The collapse rate indicates a persistence length of n~10. At lengths shorter than the persistence length the polymer acts as an elastic rod, whereas, at lengths longer than the persistence length the polymer backbone conformation forms a random coil. Based on these results we propose that at low temperatures PNIPAM adopts an extended, water-exposed conformation that is stabilized by favorable NIPAM-water solvation shell interactions which stabilize large clusters of water molecules. At elevated temperatures, thermal agitation disrupts these interactions. The PNIPAM+water polymer undergoes a volume phase transition, expels water and shrinks to a compact conformation that reduces its hydrophobic solvent accessible surface area. In this compact state, PNIPAM forms small hydrophobic nano-pockets where the (i, i +3) isopropyl groups make hydrophobic contacts. A persistent length of n~10 suggests a cooperative collapse where hydrophobic interactions between adjacent hydrophobic pockets stabilize the collapsed PNIPAM.

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Section: Introductionsupporting

confidence: 62%

UV Resonance Raman Determination of Molecular Mechanism of Poly(N-isopropylacrylamide) Volume Phase Transition

et al. 2009

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“…The spectra therefore suggest a different mixture of β‐turn populations for tyrosine and tryptophan ELPs, with the latter having a lower proportion of type I/III. We note that although the putative β‐spiral is composed of repeating type II turns, a mixed population of β‐turns is consistent with previous experimental (Ahmed et al, 2009; Reiersen et al, 1998) and modeling (Glaves et al, 2008; Krukau et al, 2007; Li et al, 2001) studies of short ELPs. Regardless, the increase in the 210/222 peak intensities with increasing temperature is an indication of stabilizing conformations.…”

Section: Resultssupporting

confidence: 91%

“…6). These two peaks are associated with type II and type I/III β‐turns, respectively (Ahmed et al, 2009; Reiersen et al, 1998). The spectra therefore suggest a different mixture of β‐turn populations for tyrosine and tryptophan ELPs, with the latter having a lower proportion of type I/III.…”

Section: Resultsmentioning

confidence: 99%

Effects of short elastin‐like peptides on filamentous particles and their transition behavior

Hathorne

Bermudez

2013

Biotech & Bioengineering

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While elastin-like polypeptides and peptides (ELPs) have been used for various stimulus-responsive applications, details of their switching remain unclear. We therefore constructed a novel series of filamentous phage particles displaying a high surface density of short ELPs. The surface display of ELPs did not disrupt either particle shape or dimensions, and the resulting ELP-phage particles were colloidally stable over several weeks. However, in spite of a saturating surface density, macroscopic aggregation of ELP-phages cannot be triggered in water. To investigate the underlying mechanisms we examined conformational changes in the secondary structure of the phage proteins by circular dichroism and tryptophan fluorescence, which indicate partial protein unfolding in ELP-phage particles. To gain further insight into the ELP itself, analogous "free" ELP peptides were synthesized and characterized. Circular dichroism of these peptides shows the onset of β-type conformations with increasing temperature, consistent with the accepted view of the microscopic transition that underlies the inverse phase behavior of ELPs. Increased guest residue hydrophobicity was found to depress the microscopic transition temperature of the peptides, also consistent with a previously proposed intramolecular hydrogen-bonding mechanism. Importantly, our results indicate that although the nanoscale presentation state can suppress macroscopic aggregation of ELPs, microscopic transitions of the ELP can still occur. Given the growing use of ELPs within supra-molecular scaffolds, such effects are important design considerations for future applications.

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“…74 If the sample volume is limited, a spinning silica capillary or cuvette with a magnetic stir bar can be used to contain the sample. 67,75 …”

Section: Uv Resonance Raman Spectroscopymentioning

confidence: 99%

UV Resonance Raman Investigations of Peptide and Protein Structure and Dynamics

et al. 2012

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Circular dichroism and UV‐resonance Raman investigation of the temperature dependence of the conformations of linear and cyclic elastin

Cited by 16 publications

References 88 publications

UV Resonance Raman Determination of Molecular Mechanism of Poly(N-isopropylacrylamide) Volume Phase Transition

UV Resonance Raman Determination of Molecular Mechanism of Poly(N-isopropylacrylamide) Volume Phase Transition

Effects of short elastin‐like peptides on filamentous particles and their transition behavior

UV Resonance Raman Investigations of Peptide and Protein Structure and Dynamics

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