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Unravelling the electronic structure and dynamics of an isolated molecular rotary motor in the gas-phase.

ABSTRACT: Light-driven molecular motors derived from chiral overcrowded alkenes are an important class of compounds in which sequential photochemical and thermal rearrangements result in unidirectional rotation of one part of the molecule with respect to another. Here, we employ anion photoelectron spectroscopy to probe the electronic structure and dynamics of a unidirectional molecular rotary motor anion in the gas-phase and quantum chemistry calculations to guide the interpretation of our results. We find that following photoexcitation of the first electronically excited state, the molecule rotates around its axle and some population remains on the excited potential energy surface and some population undergoes internal conversion back to the electronic ground state. These observations are similar to those observed in time-resolved measurements of rotary molecular motors in solution. This work demonstrates the potential of anion photoelectron spectroscopy for studying the electronic structure and dynamics of molecular motors in the gas-phase, provides important benchmarks for theory and improves our fundamental understanding of light-activated molecular rotary motors, which can be used to inform the design of new photoactivated nanoscale devices.

SUBMITTER: Beekmeyer R

PROVIDER: S-EPMC5627543 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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Unravelling the electronic structure and dynamics of an isolated molecular rotary motor in the gas-phase.

Beekmeyer Reece R Parkes Michael A MA Ridgwell Luke L Riley Jamie W JW Chen Jiawen J Feringa Ben L BL Kerridge Andrew A Fielding Helen H HH

Chemical science 20170627 9

Light-driven molecular motors derived from chiral overcrowded alkenes are an important class of compounds in which sequential photochemical and thermal rearrangements result in unidirectional rotation of one part of the molecule with respect to another. Here, we employ anion photoelectron spectroscopy to probe the electronic structure and dynamics of a unidirectional molecular rotary motor anion in the gas-phase and quantum chemistry calculations to guide the interpretation of our results. We fi ...[more]

PMID: 28989644

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Project description:The membrane-bound component F(0), which is a major component of the F(0)F(1)-ATP synthase, works as a rotary motor and plays a central role in driving the F(1) component to transform chemiosmotic energy into ATP synthesis. We conducted molecular dynamics simulations of b(2)-free F(0) in a 1-palmitoyl-2-oleoyl-phosphatidylcholine lipid bilayer for tens of nanoseconds with two different protonation states of the cAsp-61 residue at the interface of the a-c complex in the absence of electric fields and under electric fields of +/-0.03 V/nm across the membrane. To our surprise, we observed that the upper half of the N-terminal helix of the c(1) subunit rotated about its axis clockwise by 30 degrees . An energetic analysis revealed that the electrostatic repulsion between this N-terminal helix and subunit c(12) was a major contributor to the observed rotation. A correlation map analysis indicated that the correlated motions of residues in the interface of the a-c complex were significantly reduced by external electric fields. The deuterium order parameter (S(CD)) profile calculated by averaging all the lipids in the F(0)-bound bilayer was not very different from that of the pure bilayer system, in agreement with recent (2)H solid-state NMR experiments. However, by delineating the lipid properties according to their vicinity to F(0), we found that the S(CD) profiles of different lipid shells were prominently different. Lipids close to F(0) formed a more ordered structure. Similarly, the lateral diffusion of lipids on the membrane surface also followed a shell-dependent behavior. The lipids in the proximity of F(0) exhibited very significantly reduced diffusional motion. The numerical value of S(CD) was anticorrelated with that of the diffusion coefficient, i.e., the more ordered lipid structures led to slower lipid diffusion. Our findings will help elucidate the dynamics of F(0) depending on the protonation state and electric field, and may also shed some light on the interactions between the motor F(0) and its surrounding lipids under physiological conditions, which could help to rationalize its extraordinary energy conversion efficiency.

Project description:Rubbery organic frameworks-ROFs have recently emerged as an intriguing class of dynamers by virtue of reversible connections between their building units. Their highly adaptative features at the origin of their spectacular self-healing properties made them also attractive candidates for the development of gas-selective membranes combining high selectivity and fast permeability. So far, little is known on the origin of this unique trait and this clearly hampers the exploitation of this class of dynamers in many areas where stimuli-responsive pore dynamics is of great importance. To address this lack of fundamental knowledge, herein we unravel the self-assembly process of ROFs via the development of an advanced computational methodology combining quantum and force field molecular simulations that enable the description of reversible connections of building units and the long-range organization of the cross-linked ROF network. We demonstrate that both accurate energy barriers associated with the covalent bond formation between the building units and presence of solvent are key parameters to ensure the in silico construction of reliable ROF structure models that are supported by a set of experimental data collected on synthesized ROFs including density, connectivity and porosity. Atomistic insights into the unusual guest-responsive pore dynamics of this intriguing class of dynamers are further gained with a special attention paid to the tunability of this pore flexibility by controlling the chemical composition of the building units. As a further stage, the dynamics of CO2 in these compliance frameworks is scrutinized to shed light on the mechanism at the origin of their promising performance as CO2-selective membranes. We highlight that guest-triggered pore dynamics enables the creation of a diffusion pathway to ensure effective gas transport throughout the whole ROF. This knowledge of the pore structure and its guest-responsive dynamics at the microscopic level is unprecedented in the field of dynamers and it is expected to pave the way towards the optimization of this class of adaptive porous frameworks for many potential applications. Interestingly, this computational approach can be transferable to the exploration of any complex disordered systems showing a high degree of flexibility and guest induced structure/pore reorganization.

Dataset Information

Unravelling the electronic structure and dynamics of an isolated molecular rotary motor in the gas-phase.

Publications

Unravelling the electronic structure and dynamics of an isolated molecular rotary motor in the gas-phase.

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