Theoretical studies of molecular orientation and charge recombination in poly-paraphenylenevinylene light-emitting diodes

We review the standard model for de novo computational design of enzymes, which primarily focuses on the development of an active site geometry composed of protein functional groups in orientations optimized to stabilize the transition state for a novel chemical reaction not found in nature. Its emphasis is placed on the structure and energetics of the active site embedded in an accommodating protein that serves as a physical support that shields the reaction chemistry from solvent, which is typically improved upon using laboratory directed evolution. We also provide a review of design strategies that move beyond the standard model, by placing more emphasis on the designed enzyme as a whole catalytic construct. Starting with complete de novo enzyme design examples, we consider additional design factors such as entropy of individual residues, correlated motion between side chains (mutual information), dynamical correlations of the enzyme motions that could aid the reaction, reorganization energy, and electric fields as a way to exploit the entire protein scaffold to improve upon the catalytic rate, thereby providing directed evolution with better starting sequences for increasing the biocatalytic performance.

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Section: Beyond the Standard Model For Enzyme Designmentioning

confidence: 99%

Computational Design of Synthetic Enzymes

2018

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“…In this work, we make use of constrained DFT (cDFT) [24][25][26][27] in combination with linear-scaling DFT (as implemented in the ONETEP code [28]), applying it to intermolecular charge-transfer in two nearest-neighbour dimers taken from the pentacene crystal structure. The cDFT method has been applied to a wide variety of molecular systems, to date, in the context of CT excitation energies [29][30][31][32], electronic couplings [33][34][35], electron transfer [36][37][38][39] and molecular dynamics [40,41]. A largely unresolved issue in this context, however, is that of achieving supercell convergence of CT excitations in extended models suitable for capturing the screening and hybridisation effects encountered in realistic systems.…”

Section: Introductionmentioning

confidence: 99%

Supercell convergence of charge-transfer energies in pentacene molecular crystals from constrained DFT

et al. 2016

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Singlet fission (SF) is a multi-exciton generation process that could be harnessed to improve the efficiency of photovoltaic devices. Experimentally, systems derived from the pentacene molecule have been shown to exhibit ultrafast SF with high yields. Charge-transfer (CT) configurations are likely to play an important role as intermediates in the SF process in these systems. In molecular crystals, electrostatic screening effects and band formation can be significant in lowering the energy of CT states, enhancing their potential to effectively participate in SF. In order to simulate these, it desirable to adopt a computational approach which is acceptably accurate, relatively inexpensive, which and scales well to larger systems, thus enabling the study of screening effects. We propose a novel, electrostatically-corrected constrained Density Functional Theory (cDFT) approach as a low-cost solution to the calculation of CT energies in molecular crystals such as pentacene. Here we consider an implementation in the context of the ONETEP linear-scaling DFT code, but our electrostatic correction method is in principle applicable in combination with any constrained DFT implementation, also outside the linear-scaling framework. Our newly developed method allows us to estimate CT energies in the infinite crystal limit, and with these to validate the accuracy of the cluster approximation.

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“…6 CDFT has been successfully used to describe the charge transfer and ET phenomena in the ground state of some compounds. 6,10,11 In this work, we use CDFT to generate the excited ET states of the MNEI-I complex. We expect that possible phenomena can be detected qualitatively although it is impossible to avoid artifacts in CDFT because biased charge or spin constraints are imposed.…”

mentioning

confidence: 99%