Ballistic and diffusive vibrational energy transport in molecules

Abstract

Energy transport in molecules is essential for many areas of science and technology. Strong covalent bonds of a molecular backbone can facilitate the involvement of the molecule’s high-frequency modes in energy transport, which, under certain conditions, makes the transport fast and efficient. We discuss such conditions and describe various transport regimes in molecules, including ballistic, diffusive, directed diffusion, and intermediate regime cases, in light of recently developed experimental and theoretical approaches.

Topology, landscapes, and biomolecular energy transport

“…These, though, report diffusivities of 0.02 and 0.1 nm 2 ps −1 , respectively. Theoretical D ( T B ) from this type of estimate consistently exceed experimental values for Aib 10 but are comparable to bulk materials 27 and other proteins 39 . Force-field parameterization likely contributes to this discrepancy in part.…”

“…1d). This corresponds to backbone propagation at v = 1.7 nm ps −1 , approaching ballistic transport velocities in biomolecular materials and alkyl chains 12,25–27,44 . While this channel is weak, additional ballistic pathways may exist at lower group velocities in different vibrational bands 44,45 , though these will inevitably be obscured by more prominent diffusive features.…”

Direct observation of nuclear reorganization driven by ultrafast spin transitions

“…Following the arrival of the BPY molecule onto the HS state surface, the initial Fe-N bond distribution is narrower than that of AZA upon similar photoexcitation, and evolves in a more coherent manner, as observed by X-ray spectroscopies 26,30,40 . The number of lowfrequency modes (of which there are many more in AZA than in BPY), the total number of degrees of freedom, and the symmetry of the ligands are important during the vibrational cooling process 13,19,52 . The delocalized low-frequency modes of BPY and AZA have been calculated using TD-DFT 53 (details in Supplementary Note 7).…”

Through Bonds or Contacts? Mapping Protein Vibrational Energy Transfer Using Non-canonical Amino Acids.

“…Chemical reactions in enzymes create substantial excess energy that needs to be efficiently dissipated in order to avoid damage to the protein. 1,2 The most active enzymes can carry out a catalytic cycle producing significant excess energy up to 10 7 times per second. 3 Light driven reactions for instance, such as the isomerization of chromophores in photoreceptors, can create excess energies in the range of more than 2 eV.…”

“…Vibrational energy is injected into the system either by IR excitation 16,17,[24][25][26] and subsequent relaxation of a local vibration, or by UV/VIS excitation 14,18,20,27 and internal conversion of a chromophore. Energy propagation is monitored by another spectroscopic transition, either vibrational 1,15,17,26,28 or electronic. 29 For VET studies in peptides and proteins we recently introduced a pair of non-canonical amino acids consisting of a vibrational energy donor and a vibrational energy sensor, which can be incorporated either synthetically or cotranslationally during protein expression.…”