Quick Search:

uzh logo
Browse by:
bullet
bullet
bullet
bullet

Zurich Open Repository and Archive 

Permanent URL to this publication: http://dx.doi.org/10.5167/uzh-8694

Backus, E H G; Nguyen, P H; Botan, V; Pfister, R; Moretto, A; Crisma, M; Toniolo, C; Stock, G; Hamm, P (2008). Energy transport in peptide helices: a comparison between high- and low-energy excitations. Journal of Physical Chemistry. B, 112(30):9091-9099.

[img]PDF - Registered users only
2300Kb

Abstract

Energy transport in a short helical peptide in chloroform solution is studied by time-resolved femtosecond spectroscopy and accompanying nonequilibrium molecular dynamics (MD) simulations. In particular, the heat transport after excitation of an azobenzene chromophore attached to one terminus of the helix with 3 eV (UV) photons is compared to the excitation of a peptide C=O oscillator with 0.2 eV (IR) photons. The heat in the helix is detected at various distances from the heat source as a function of time by employing vibrational pump−probe spectroscopy. As a result, the carbonyl oscillators at different positions along the helix act as local thermometers. The experiments show that heat transport through the peptide after excitation with low-energy photons is at least 4 times faster than after UV excitation. On the other hand, the heat transport obtained by nonequilibrium MD simulations is largely insensitive to the kind of excitation. The calculations agree well with the experimental results for the low-frequency case; however, they give a factor of 5 too fast energy transport for the high-energy case. Employing instantaneous normal mode calculations of the MD trajectories, a simple harmonic model of heat transport is adopted, which shows that the heat diffusivity decreases significantly at temperatures initially reached by high-energy excitation. This finding suggests that the photoinduced energy gets trapped, if it is deposited in high amounts. The various competing mechanisms, such as vibrational T1 relaxation, resonant transfer between excitonic states, cascading down relaxation, and low-frequency mode transfer, are discussed in detail.

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Physical Chemistry
DDC:540 Chemistry
Language:English
Date:31 July 2008
Deposited On:14 Jan 2009 17:22
Last Modified:27 Nov 2013 22:18
Publisher:American Chemical Society
ISSN:1520-5207
Publisher DOI:10.1021/jp711046e
PubMed ID:18597522
Citations:Web of Science®. Times Cited: 39
Google Scholar™

Users (please log in): suggest update or correction for this item

Repository Staff Only: item control page