Vibrational energy transport through a capping layer of appropriately designed peptide helices over gold nanoparticles.
ABSTRACT We design and characterize spherical gold nanoparticles, which are covalently linked to and completely covered by 3(10)-helical peptides. These helices provide a scaffold to place (13)C=O isotope labels at defined distances from the gold surface, which we employ as local thermometers. Probing these reporter groups with transient infrared spectroscopy, we monitor the vibrational energy flow across the peptide capping layer following excitation of the nanoparticle plasmon resonance.
- SourceAvailable from: Lian-Ao Wu[Show abstract] [Hide abstract]
ABSTRACT: Quantum energy transfer in a chain of two-level (spin) units, connected at its ends to two thermal reservoirs, is analyzed in two limits: (i) in the off-resonance regime, when the characteristic subsystem excitation energy gaps are larger than the reservoirs frequencies, or the baths temperatures are low and (ii) in the resonance regime, when the chain excitation gaps match populated bath modes. In the latter case, the model is studied using a master equation approach, showing that the dynamics is ballistic for the particular chain model explored. In the former case, we analytically study the system dynamics utilizing the recently developed Energy-Transfer Born-Oppenheimer formalism [L.-A. Wu and D. Segal, Phys. Rev. E 83, 051114 (2011)], demonstrating that energy transfers across the chain in a superexchange (bridge assisted tunneling) mechanism, with the energy current decreasing exponentially with distance. This behavior is insensitive to the chain details. Since at low temperatures the excitation spectrum of molecular systems can be truncated to resemble a spin chain model, we argue that the superexchange behavior obtained here should be observed in widespread systems satisfying the off-resonance condition.The Journal of Chemical Physics 12/2011; 135(23):234508. · 3.12 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: To measure the transport of vibrational energy along a peptide helix, Hamm and co-workers [J. Phys. Chem. B 112, 9091 (2008)] performed time-resolved vibrational experiments, which showed that the energy transport rate increases by at least a factor of 4, when a localized C=O mode of the peptide instead of an attached chromophore is excited. This finding raises the question if coherent excitonic energy transfer between the C=O modes may be of importance for the overall energy transport in peptides. With this idea in mind, nonequilibrium molecular dynamics simulations as well as quantum-classical calculations are performed, which qualitatively reproduce the experimental findings. Moreover, the latter model (an exciton Hamiltonian whose matrix elements depend on the instantaneous positions of the peptide and solvent atoms) indeed exhibits the signatures of coherent quantum energy transport, at least within the first few picoseconds and at low temperatures. The origin of the observed decoherence, the absence of vibrational self-trapping, and the possibility of quantum interference between various transport paths are discussed in some detail.The Journal of Chemical Physics 03/2011; 134(12):124518. · 3.12 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: In a previous paper [M. Schade, P. Hamm, Vibrational energy transport in the presence of intrasite vibrational energy redistribution, J. Chem. Phys. 131 (2009) 044511], it has been shown that on ultrashort length and time scales, the speed of vibrational energy transport along a molecular chain is limited by intrasite vibrational relaxation rather than the actual intersite propagation. However, since intrasite vibrational relaxation is length independent, the intersite propagation rate is expected to become rate-limiting at some length scale, where propagation approaches the bulk limit. In the present paper, we investigate the transition between both regimes. The response of different types of modes may be very different at early times, depending on how much they contribute directly to energy transport. Surprisingly though, when averaging the energy content over all vibrational modes of the various chain sites, the complexity of the intrasite vibrational relaxation process is completely hidden so that energy transport on the nanoscale can be described by an effective propagation rate, that equals the bulk value, even at short times.Chemical Physics 01/2012; 393(1):46–50. · 1.96 Impact Factor