Dataset Information

Dynamics of the folded and unfolded villin headpiece (HP35) measured with ultrafast 2D IR vibrational echo spectroscopy.

ABSTRACT: A series of two-dimensional infrared vibrational echo experiments performed on nitrile-labeled villin headpiece [HP35-(CN)(2)] is described. HP35 is a small peptide composed of three alpha helices in the folded configuration. The dynamics of the folded HP35-(CN)(2) are compared to that of the guanidine-induced unfolded peptide, as well as the nitrile-functionalized phenylalanine (PheCN), which is used to differentiate the peptide dynamic contributions to the observables from those of the water solvent. Because the viscosity of solvent has a significant effect on fast dynamics, the viscosity of the solvent is held constant by adding glycerol. For the folded peptide, the addition of glycerol to the water solvent causes observable slowing of the peptide's dynamics. Holding the viscosity constant as GuHCl is added, the dynamics of unfolded peptide are much faster than those of the folded peptide, and they are very similar to that of PheCN. These observations indicate that the local environment of the nitrile in the unfolded peptide resembles that of PheCN, and the dynamics probed by the CN are dominated by the fluctuations of the solvent molecules, in contrast to the observations on the folded peptide.

SUBMITTER: Chung JK

PROVIDER: S-EPMC3048147 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature

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Dynamics of the folded and unfolded villin headpiece (HP35) measured with ultrafast 2D IR vibrational echo spectroscopy.

Chung Jean K JK Thielges Megan C MC Fayer Michael D MD

Proceedings of the National Academy of Sciences of the United States of America 20110214 9

A series of two-dimensional infrared vibrational echo experiments performed on nitrile-labeled villin headpiece [HP35-(CN)(2)] is described. HP35 is a small peptide composed of three alpha helices in the folded configuration. The dynamics of the folded HP35-(CN)(2) are compared to that of the guanidine-induced unfolded peptide, as well as the nitrile-functionalized phenylalanine (PheCN), which is used to differentiate the peptide dynamic contributions to the observables from those of the water s ...[more]

PMID: 21321226

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Project description:Dynamic and structural properties of carbonmonoxy (CO)-coordinated cytochrome c(552) from Hydrogenobacter thermophilus (Ht-M61A) at different temperatures under thermal equilibrium conditions were studied with infrared absorption spectroscopy and ultrafast two-dimensional infrared (2D IR) vibrational echo experiments using the heme-bound CO as the vibrational probe. Depending on the temperature, the stretching mode of CO shows two distinct bands corresponding to the native and unfolded proteins. As the temperature is increased from low temperature, a new absorption band for the unfolded protein grows in and the native band decreases in amplitude. Both the temperature-dependent circular dichroism and the IR absorption area ratio R(A)(T), defined as the ratio of the area under the unfolded band to the sum of the areas of the native and unfolded bands, suggest a two-state transition from the native to the unfolded protein. However, it is found that the absorption spectrum of the unfolded protein increases its inhomogeneous line width and the center frequency shifts as the temperature is increased. The changes in line width and center frequency demonstrate that the unfolding does not follow simple two-state behavior. The temperature-dependent 2D IR vibrational echo experiments show that the fast dynamics of the native protein are virtually temperature independent. In contrast, the fast dynamics of the unfolded protein are slower than those of the native protein, and the unfolded protein fast dynamics and at least a portion of the slower dynamics of the unfolded protein change significantly, becoming faster as the temperature is raised. The temperature dependence of the absorption spectrum and the changes in dynamics measured with the 2D IR experiments confirm that the unfolded ensemble of conformers continuously changes its nature as unfolding proceeds, in contrast to the native state, which displays a temperature-independent distribution of structures.

Dataset Information

Dynamics of the folded and unfolded villin headpiece (HP35) measured with ultrafast 2D IR vibrational echo spectroscopy.

Publications

Dynamics of the folded and unfolded villin headpiece (HP35) measured with ultrafast 2D IR vibrational echo spectroscopy.

Similar Datasets

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