Modulating Accidental Fermi Resonance: What a Difference a Neutron Makes

Lipkin, Jacob S.; Song, Rui; Fenlon, Edward E.; Brewer, Scott H.

doi:10.1021/jz2006447

Cited by 61 publications

(82 citation statements)

References 42 publications

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“…This asymmetry has been detected within other cyano- substituted aromatic side chains, and it is likely due to a slight Fermi resonance. [7] Another possibility is that two conformers of the molecule are present in THF whereas only one is seen in water, as seen in other ring systems. [1i] In our current work, the transition dipole strength (μ) of Trp 5CN in water was measured to be 0.49 ± 0.02 D using methods reported by Zanni and coworkers.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of 5‐Cyano‐Tryptophan as a Two‐Dimensional Infrared Spectroscopic Reporter of Structure

et al. 2018

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A concise synthesis of protected 5-cyano-L-tryptophan (Trp5CN) has been developed for 2D IR spectroscopic investigations within peptides or proteins. To assess the potential of differently substituted cyano-tryptophans, several model cyanoindole systems were characterized using IR spectroscopy. Upon assessment of their spectroscopic properties, Trp5CN was integrated into a model peptide sequence, Trp5CN–Gly–Phe4CN, to elucidate its structure. This peptide demonstrates the capability of this probe, Trp5CN and Phe4CN, to capture structural information via 2D IR spectroscopy. The 2D IR spectrum of the peptide in water was simulated to reveal a unique spectral signature resulting from the presence of dipolar coupling. The coupling strength between cyano-labels was determined to be 1.4 cm−1 by matching the slopes along the max contour between the simulated and experimental spectrum. Using transition dipole coupling, a distance between the two probes of 13 Å was calculated.

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Section: Resultsmentioning

confidence: 99%

Synthesis of 5‐Cyano‐Tryptophan as a Two‐Dimensional Infrared Spectroscopic Reporter of Structure

et al. 2018

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“…In addition, due to its utility in click chemistry, many methods are available to introduce an azide into proteins and several unnatural amino acids containing the azide moiety are commercially available. On the other hand, the azide stretching frequency shows a lesser dependence on solvent than that of C≡N and, in many cases, its vibrational band is accompanied by features arising from Fermi resonances, making it less attractive in certain applications (117). Examples that illustrate the IR applications of azide probes include using 1) azidohomoalanine to probe differences in folding rates of the protein backbone versus sidechains (118), 2) p -azido- l -phenylalanine to investigate the structures of rhodopsin photointermediates (119), and 3) 3-picolyl azide adenine dinucleotide to examine the local environment and dynamics of the formate dehydrogenase enzyme active site (120).…”

Section: Sidechain-based Ir Probesmentioning

confidence: 99%

Site-Specific Infrared Probes of Proteins

Pazos²,

Zhang³

et al. 2015

Annu. Rev. Phys. Chem.

166

189

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Infrared spectroscopy has played an instrumental role in studying a wide variety of biological questions. However, in many cases it is impossible or difficult to rely on the intrinsic vibrational modes of biological molecules of interest, such as proteins, to reveal structural and/or environmental information in a site-specific manner. To overcome this limitation, many recent efforts have been dedicated to the development and application of various extrinsic vibrational probes that can be incorporated into biological molecules and used to site-specifically interrogate their structural and/or environmental properties. In this Review, we highlight some recent advancements of this rapidly growing research area.

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“…Analysis of the calculated fully-anharmonically corrected vibrations of the molecule shows that the observed doublet is due to a combination band of two vibrations localized on the 13 C-arm of the molecule in resonance with the ν( 13 C) fundamental, leading to quantum mechanical mixing and intensity borrowing between the two modes. 24,25 A prerequisite to ensure that mode-selective excitation with an IR pump leads to localised excitations on either arm of the molecule is that ν( 13 C) and ν( 12 C) are decoupled. To ascertain that this condition is fulfilled, two-dimensional IR experiments (2DIR), which can be used to probe off-diagonal coupling elements between sets of vibrations, 26 were performed on this system.…”

Section: Vibrationally Decoupling the Two Electron Transfer Pathwaysmentioning

confidence: 99%

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

et al. 2017

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Ultrafast electron transfer in condensed-phase molecular systems is often strongly coupled to intramolecular vibrations that can promote, suppress and direct electronic processes. Recent experiments exploring this phenomenon proved that light-induced electron transfer can be strongly modulated by vibrational excitation, suggesting a new avenue for active control over molecular function. Here, we achieve the first example of such explicit vibrational control through judicious design of a Pt(II)-acetylide charge-transfer Donor-Bridge-Acceptor-Bridge-Donor "fork" system: asymmetric 13 C isotopic labelling of one of the two -C≡C-bridges makes the two parallel and otherwise identical Donor→Acceptor electron-transfer pathways structurally distinct, enabling independent vibrational perturbation of either. Applying an ultrafast UV pump (excitation)-IR pump (perturbation)-IR probe (monitoring) pulse sequence, we show that the pathway that is vibrationally perturbed during UV-induced electron-transfer is dramatically slowed down compared to its unperturbed counterpart. One can thus choose the dominant electron transfer pathway. The findings deliver a new opportunity for precise perturbative control of electronic energy propagation in molecular devices. Main TextControlling the function of future advanced materials demands a profound understanding of energymatter interactions in molecular systems at the quantum level. 1 There is a growing consensus that energy-and electron-transfer processes occurring far away from equilibrium in condensed-phase systems on femto-to-picosecond timescales do not conform to the Born-Oppenheimer approximation. Indeed, nuclear and electronic wave functions often strongly interact with each other, leading to exotic phenomena whereby vibrational motion can mediate and dictate the rate and efficiency of electronic transitions. [2][3][4][5] With overwhelming evidence that nuclear-electronic (vibronic) interactions play a crucial role in a broad range of systems, including light harvesting and conversion in photosynthetic organisms, 6-11 this phenomenon represents a tremendous opportunity to acquire deeper knowledge and control over the structural traits that govern molecular function and reactivity.Recent efforts led by Rubtsov et al.,12,13 Bakulin et al., 14 and our group 15,16 have shown that one way to experimentally exploit vibronic coupling to modulate molecular function is to introduce targeted vibrational excitation along specific reaction co-ordinates using ultrafast mid-infrared (IR) pulses. This approach enables promoting or suppressing electronic transitions, notably photo-induced electron transfer (ET), an elementary process that pervades the natural world. Although the demonstrated excited state modulations have been remarkably efficient, up to 100% suppression in one case, 15 predictive and directive control of electron transfer in the condensed phase has not been achieved yet.

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Modulating Accidental Fermi Resonance: What a Difference a Neutron Makes

Cited by 61 publications

References 42 publications

Synthesis of 5‐Cyano‐Tryptophan as a Two‐Dimensional Infrared Spectroscopic Reporter of Structure

Synthesis of 5‐Cyano‐Tryptophan as a Two‐Dimensional Infrared Spectroscopic Reporter of Structure

Site-Specific Infrared Probes of Proteins

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

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