<i>Molecular Interactions and Electronic Spectra</i>

Matoga, Noboru; Kubota, Tanekazu; Person, Willis B.

doi:10.1063/1.3127907

Cited by 159 publications

(142 citation statements)

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“…Electrostatic fields in condensed media are traditionally quantified by the solvent induced shift of optical 35 or vibrational 36 transition lines. The electrostatic component of the shift, often dominant, 37 is given by the product of the dipole moment change of the chromophore ∆m and the reaction field R in the ground state in equilibrium with the ground-state dipole m g h∆ν = −∆mR.…”

Section: Connection To Experimentsmentioning

confidence: 99%

Electrostatics of liquid interfaces

Matyushov

2014

The Journal of Chemical Physics

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The standard Maxwell formulation of the problem of polarized dielectrics suffers from a number of difficulties, both conceptual and practical. These difficulties are particularly significant in the case of liquid interfaces, where the ability of the interfacial multipoles to change their orientations to minimize their free energies leads to interfacial polarization localized within a thin microscopic layer. A formalism to capture this physical reality of localized interfacial polarization is proposed and is based on the surface charge as the source of microscopic electric fields in dielectrics. The surface charge density incorporates the local structure of the interface into electrostatic calculations. The corresponding surface susceptibility and interface dielectric constant provide local closures to the electrostatic boundary value problem. A robust approach to calculate the surface susceptibility from numerical simulations is proposed. The susceptibility can alternatively be extracted from a number of solution experiments, in particular those sensitive to the overall dipole moment of a closed dielectric surface. The theory is applied to the solvent-induced spectral shift and high-frequency dielectric response of solutions.

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Section: Connection To Experimentsmentioning

confidence: 99%

Electrostatics of liquid interfaces

Matyushov

2014

The Journal of Chemical Physics

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“…The curvature of F i (Ω) is the restoring force constant of the harmonic motion, which loses its stiffness with increasing α 0 . The same statement applies to the dynamics of the solvent electric field E. The harmonic stiffness constant for the equations of field evolution is (2a p ) −1 − α 0i (eq (47)), and it decreases with increasing solute polar- Reorganization energies are calculated according to eq (9). c g and e denote ground and excited states, respectively.…”

Section: Dynamicsmentioning

confidence: 99%

“…is the skewness correlation function, 22 with the stationary spectral width σ given by eq (9). Note that linear response does not stipulate Gaussian dynamics, and only the smallness of the perturbation introduced in the solvent by the electronic transition is required.…”

Section: Time-resolved Lineshapesmentioning

confidence: 99%

“…Standard electrostatic models of solvation indeed suggest a linear coupling between permanent charges of the solute and the solvent. For instance, if the distribution of the chromophore's molecular charge is given by a dipole m 0 , it couples linearly to the electric field of the medium E and the electrostatic solute-solvent interaction energy is simply −m 0 · E. 9,10 If the electric field is a Gaussian stochastic variable, i.e., only the first two cumulants of E contribute to the cumulant generating functional (line broadening function), 5,11,12 the statistics of the transition frequency is Gaussian as well.…”

Section: Introductionmentioning

confidence: 99%

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Non-Gaussian Lineshapes and Dynamics of Time-Resolved Linear and Nonlinear (Correlation) Spectra

Dinpajooh

Matyushov

2014

J. Phys. Chem. B

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Signatures of nonlinear and non-Gaussian dynamics in time-resolved linear and nonlinear (correlation) 2D spectra are analyzed in a model considering a linear plus quadratic dependence of the spectroscopic transition frequency on a Gaussian nuclear coordinate of the thermal bath (quadratic coupling). This new model is contrasted to the commonly assumed linear dependence of the transition frequency on the medium nuclear coordinates (linear coupling). The linear coupling model predicts equality between the Stokes shift and equilibrium correlation functions of the transition frequency and time-independent spectral width. Both predictions are often violated, and we are asking here the question of whether a nonlinear solvent response and/or non-Gaussian dynamics are required to explain these observations. We find that correlation functions of spectroscopic observables calculated in the quadratic coupling model depend on the chromophore's electronic state and the spectral width gains time dependence, all in violation of the predictions of the linear coupling models. Lineshape functions of 2D spectra are derived assuming Ornstein-Uhlenbeck dynamics of the bath nuclear modes. The model predicts asymmetry of 2D correlation plots and bending of the center line. The latter is often used to extract two-point correlation functions from 2D spectra. The dynamics of the transition frequency are non-Gaussian. However, the effect of non-Gaussian dynamics is limited to the third-order (skewness) time correlation function, without affecting the time correlation functions of higher order. The theory is tested against molecular dynamics simulations of a model polar-polarizable chromophore dissolved in a force field water.

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“…First, the ~120 nm (~25 kcal/mol) difference between model compounds and the observed intermediate is unusually large to be rationalized by charge-transfer. 22 Second, features in the circular dichroism (CD) spectrum are frequently, although not always, seen as a consequence of CT. 21 No changes in the CD spectrum of CEAS were detected upon formation of the chromophore. Third, the appearance of CT bands is typically altered by changes in solvent composition or temperature.…”

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confidence: 99%

Observation of an Acryloyl−Thiamin Diphosphate Adduct in the First Step of Clavulanic Acid Biosynthesis

Merski

Townsend

2007

J. Am. Chem. Soc.

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The first committed biosynthetic step toward clavulanic acid, the clinically-important β-lactamase inhibitor, is catalyzed by the thiamin diphosphate (ThDP)-dependent enzyme N 2 -(2-carboxyethyl)arginine synthase (CEAS). This protein carries out a unique reaction among ThDPdependent processes in which a C-N bond is formed, and an electrophilic acryloyl-thiazolium intermediate of ThDP is proposed to be involved, unlike the nucleophilic enamine species typically generated by this class of enzymes. Here we present evidence for the existence of the putative acryloyl adduct, and report the unexpected observation of a long-wavelength chromophore (λ = 433 nm), which we attribute to this enzyme bound species. Chemical models were synthesized that both confirm its expected absorption (λ = 310-320 nm), and exclude selfcondensation and intramolecular imine formation with the cofactor as its cause. Circular dichroism experiments and others discount charge transfer as a likely explanation for the ~120 nm red shift of the chromophore (~25 kcal). Examples are well-known of charged molecules that exhibit significantly red-shifted UV-visible spectra compared to their neutral forms as, for example, polyene cations and dyes such as indigo and the cyanines. Rhodopsin is the classic biochemical example where the protein (opsin)-bound protonated Schiff base of retinal displays a remarkable range of red-shifted absorptions modulated by the protein environment. Similar tuning of the chromophoric behavior of the enzyme-bound CEAS acryloyl•ThDP species may be occurring.With the rise in resistance to penicillins and cephalosporins, the β-lactamase inhibitor clavulanic acid (1) has grown in importance for the treatment of bacterial infections 1 . Several mechanistically intriguing reactions take place in the biosynthesis of 1, 2 the first of which is mediated by N 2 -(2-carboxyethyl)arginine synthase (CEAS). The primary metabolites D-glyceraldehyde-3-phosphate (G3P) and L-arginine are recruited by this enzyme and reacted in a thiamine diphosphate (ThDP)-dependent internal redox process to yield N 2 -(2-carboxyethyl)arginine (6, CEA; Scheme 1). 3 The mechanism shown in Scheme 1 was proposed in accord with extensive isotopic labeling and stereochemical experiments. 3 NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript feature of this mechanism was the suggested intermediacy of an acryloyl-ThDP adduct 4. The observation of overall retention of configuration at the G3P β-carbon is consistent with a β-elimination/addition process proceeding by way of this highly electrophilic 4 partner for reaction with the incoming L-arginine. This is a unique reaction cycle among ThDPdependent enzymes where typically intermediates formed are nucleophilic rather than electrophilic, and N-C bond formation has not been seen previously.In this Communication we demonstrate the formation of the acryloyl species 4 and report the observation of an unexpectedly long-wavelength chromophore, which owes to the presence of the acryloyl inter...

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Molecular Interactions and Electronic Spectra

Cited by 159 publications

References 0 publications

Electrostatics of liquid interfaces

Electrostatics of liquid interfaces

Non-Gaussian Lineshapes and Dynamics of Time-Resolved Linear and Nonlinear (Correlation) Spectra

Observation of an Acryloyl−Thiamin Diphosphate Adduct in the First Step of Clavulanic Acid Biosynthesis

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