Vibrational Dynamics of Hydrogen-Bonded Complexes in Solutions Studied with Ultrafast Infrared Pump−Probe Spectroscopy

Banno, Motohiro; Ohta, Kaoru; Yamaguchi, Sayuri; Hirai, Satori; Tominaga, Kazuhiro

doi:10.1021/ar9000229

“…[12] For example, in D 2 O the IR spectrum of MA gives rise to two distinct peaks, centered at 1703.6 and 1727.0 cm -1 , which is consistent with the two dimensional IR (2D IR) study of Righini and coworkers. [13] In agreement with the study of Tominaga and coworkers, [14] the ester carbonyl stretching band of MA in methanol consists of three resolvable spectral features, centered at 1748.1, 1729.6 and 1708.1 cm -1 . For MP, however, the spectrum obtained in D 2 O is broad and almost featureless.…”

Section: Ir Probe; Protein Electrostatics; Hydrogen Bondingsupporting

confidence: 87%

Ester Carbonyl Vibration as a Sensitive Probe of Protein Local Electric Field

Pazos

¹

,

Ghosh

²

,

Tucker

³

et al. 2014

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The ability to quantify the local electrostatic environment of proteins and protein/peptide assemblies is key to yielding a microscopic understanding of many biological interactions and processes. Herein, we show that the ester carbonyl stretching vibration of two non-natural amino acids, L-aspartic acid 4-methyl ester and L-glutamic acid 5-methyl ester, is a convenient and sensitive probe in this regard since its frequency correlates linearly with the local electrostatic field for both hydrogen-bonding and non-hydrogen-bonding environments. We expect that the resultant frequency-electric field map will find use in various applications. In addition, we show that, when situated in a non-hydrogen bonding environment, this probe can also be used to measure the local dielectric constant (ε). For example, applying it to amyloid fibrils formed by Aβ [16][17][18][19][20][21][22] reveals that the interior of such β-sheet assemblies has a ε of ~5.6. Keywords IR Probe; Protein Electrostatics; Hydrogen BondingElectrostatic interactions are ubiquitous in biological molecules and, in many cases, play a key role in molecular association and enzymatic reactions. [1] However, quantifying the local electric field or how it changes inside a protein, especially in a site-specific manner and/or as a function of time, still remains a challenging task. One promising method in this regard is vibrational Stark spectroscopy, [2] which capitalizes on the fact that vibrational transitions have an intrinsic dependence on local electrostatic environment and uses an infrared (IR) probe that has a well-defined, localized vibrational mode to sense local electric field amplitude through the response of the frequency. [3] For example, the vibrational Stark effect has been used to determine the local electric field at protein interfaces and to monitor protein conformational transitions and dynamics. [4] While the theoretical underpinning of this methodology is straightforward, in practice the application of vibrational Stark spectroscopy to biological systems is currently limited by the availability of suitable vibrational probes. Herein, we show, using linear and nonlinear IR measurements and molecular dynamics (MD) simulations, that the ester carbonyl vibration in two non-natural amino acids can be used to quantitatively and site-specifically probe the electric fields of proteins, including those arising from hydrogen-bond (H-bond) interactions.The utility of a vibrational probe to reliably and conveniently measure local electric fields in proteins is evaluated by how well it meets several criteria. First and foremost, its frequency must show a sensitive and quantifiable dependence on the local electric field. Also, a chemical or biological method must exist to incorporate the probe into a protein.Furthermore, it must minimally perturb the native chemical and structural environment of interest. Finally, its vibration must be a localized mode having a large cross-section and, ideally, be located in an uncongested region of the IR spectru...

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“…[12] For example, in D 2 O the IR spectrum of MA gives rise to two distinct peaks, centered at 1703.6 and 1727.0 cm -1 , which is consistent with the two dimensional IR (2D IR) study of Righini and coworkers. [13] In agreement with the study of Tominaga and coworkers, [14] the ester carbonyl stretching band of MA in methanol consists of three resolvable spectral features, centered at 1748.1, 1729.6 and 1708.1 cm -1 . For MP, however, the spectrum obtained in D 2 O is broad and almost featureless.…”

supporting

confidence: 88%

Ester Carbonyl Vibration as a Sensitive Probe of Protein Local Electric Field

Pazos

¹

,

Ghosh

²

,

Tucker

³

et al. 2014

View full text Add to dashboard Cite

The ability to quantify the local electrostatic environment of proteins and protein/peptide assemblies is key to yielding a microscopic understanding of many biological interactions and processes. Herein, we show that the ester carbonyl stretching vibration of two non-natural amino acids, L-aspartic acid 4-methyl ester and L-glutamic acid 5-methyl ester, is a convenient and sensitive probe in this regard since its frequency correlates linearly with the local electrostatic field for both hydrogen-bonding and non-hydrogen-bonding environments. We expect that the resultant frequency-electric field map will find use in various applications. In addition, we show that, when situated in a non-hydrogen bonding environment, this probe can also be used to measure the local dielectric constant (ε). For example, applying it to amyloid fibrils formed by Aβ16-22 reveals that the interior of such β-sheet assemblies has a ε of ~5.6.

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“…14 −18 It has been shown that, for certain classes of molecules, a linear correlation exists between the frequency of the excited vibrational mode and its population relaxation time 19 whereas, in other cases, this relationship is complicated by interactions with the solvent. 20,21 In the current work, we performed a detailed study of the solvent−solute interactions between two VC adducts in two series of binary solvent mixtures. We focused our attention on the behavior of the frequency and width of the inhomogeneous line shape and the rate of VER of ν CO for two specific VC adducts: the dioxygen adduct (VC-O 2 ) and the diiodide adduct (VC-I 2 ).…”

Section: ■ Introductionmentioning

confidence: 99%

Solvent-Mediated Vibrational Energy Relaxation from Vaska’s Complex Adducts in Binary Solvent Mixtures

Jones

¹

,

Huber

²

,

Massari

³

2013

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A vibrational pump-probe and FTIR study was performed on two different adducts of Vaska's complex in two different sets of binary solvent mixtures. The carbonyl vibrational mode in the oxygen adduct exhibits solvatochromic shifts of ~10 cm(-1) in either benzyl alcohol or chloroform relative to benzene-d6, whereas this vibration is nearly unchanged for the iodine adduct for the same three solvents. The width and center frequency of the carbonyl stretch for each adduct are compared to its vibrational lifetime in binary mixtures of benzene-d6 with either benzyl alcohol or chloroform. In neat solvents, the trends in line width, frequency, and vibrational lifetime are consistent for the two adducts, but complex relationships emerge when the trends in each property are compared as a function of mixed solvent composition. ν(CO) is more sensitive to the solvation environment around the trans ligand, whereas the line width and lifetime depend on the environment around the CO group itself. The carbonyl frequency and width vary nonlinearly across the two binary solvent series, indicating preferential solvation. In contrast, the vibrational lifetime changes linearly with solvent composition and is correlated with the mole fraction of chloroform but anticorrelated with the mole fraction of benzyl alcohol. The results are explained by differences in the densities of solvent modes that affect intermolecular relaxation of the carbonyl mode.

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Vibrational Dynamics of Hydrogen-Bonded Complexes in Solutions Studied with Ultrafast Infrared Pump−Probe Spectroscopy

Cited by 71 publications

References 49 publications

Ester Carbonyl Vibration as a Sensitive Probe of Protein Local Electric Field

Ester Carbonyl Vibration as a Sensitive Probe of Protein Local Electric Field

Ester Carbonyl Vibration as a Sensitive Probe of Protein Local Electric Field

Solvent-Mediated Vibrational Energy Relaxation from Vaska’s Complex Adducts in Binary Solvent Mixtures

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