ONIOM Investigation of the Second-Order Nonlinear Optical Responses of Fluorescent Proteins

Marc De Wergifosse, Edith Botek, Evelien De Meulenaere, K. Clays, Benoît Champagne

Research output: Contribution to journalArticle

Abstract

The first hyperpolarizability (β) of six fluo-rescent proteins (FPs), namely, enhanced green fluorescent protein, enhanced yellow fluorescent protein, SHardonnay, ZsYellow, DsRed, and mCherry, has been calculated to unravel the structure−property relationships on their second-order nonlinear optical properties, owing to their potential for multidimensional biomedical imaging. The ONIOM scheme has been employed and several of its refinements have been addressed to incorporate efficiently the effects of the microenvironment on the nonlinear optical responses of the FP chromophore that is embedded in a protective β-barrel protein cage. In the ONIOM scheme, the system is decomposed into several layers (here two) treated at different levels of approximation (method1/method2), from the most elaborated method (method1) for its core (called the high layer) to the most approximate one (method2) for the outer surrounding (called the low layer). We observe that a small high layer can already account for the variations of β as a function of the nature of the FP, provided the low layer is treated at an ab initio level to describe properly the effects of key H-bonds. Then, for semiquantitative reproduction of the experimental values obtained from hyper-Rayleigh scattering experiments, it is necessary to incorporate electron correlation as described at the second-order Møller−Plesset perturbation theory (MP2) level as well as implicit solvent effects accounted for using the polarizable continuum model (PCM). This led us to define the MP2/6-31+G(d):HF/6-31+G(d)/IEFPCM scheme as an efficient ONIOM approach and the MP2/6-31+G(d):HF/6-31G(d)/IEFPCM as a better compromise between accuracy and computational needs. Using these methods, we demonstrate that many parameters play a role on the β response of FPs, including the length of the π - conjugated segment, the variation of the bond length alternation, and the presence of π -stacking interactions. Then, noticing the small diversity of the FP chromophores, these results highlight the key role of the β -barrel and surrounding residues on β , not only because they can locally break the noncentrosymmetry vital to a β response but also because it can impose geometrical constraints on the chromophore.
Original languageEnglish
Pages (from-to)4993-5005
Number of pages13
JournalJournal of physical chemistry A
Volume122
Issue number19
DOIs
Publication statusPublished - 17 May 2018

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proteins
Proteins
Chromophores
chromophores
Electron correlations
Rayleigh scattering
Bond length
alternations
Optical properties
Imaging techniques
perturbation theory
continuums
optical properties
Experiments
approximation
electrons
interactions

Cite this

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title = "ONIOM Investigation of the Second-Order Nonlinear Optical Responses of Fluorescent Proteins",
abstract = "The first hyperpolarizability (β) of six fluo-rescent proteins (FPs), namely, enhanced green fluorescent protein, enhanced yellow fluorescent protein, SHardonnay, ZsYellow, DsRed, and mCherry, has been calculated to unravel the structure−property relationships on their second-order nonlinear optical properties, owing to their potential for multidimensional biomedical imaging. The ONIOM scheme has been employed and several of its refinements have been addressed to incorporate efficiently the effects of the microenvironment on the nonlinear optical responses of the FP chromophore that is embedded in a protective β-barrel protein cage. In the ONIOM scheme, the system is decomposed into several layers (here two) treated at different levels of approximation (method1/method2), from the most elaborated method (method1) for its core (called the high layer) to the most approximate one (method2) for the outer surrounding (called the low layer). We observe that a small high layer can already account for the variations of β as a function of the nature of the FP, provided the low layer is treated at an ab initio level to describe properly the effects of key H-bonds. Then, for semiquantitative reproduction of the experimental values obtained from hyper-Rayleigh scattering experiments, it is necessary to incorporate electron correlation as described at the second-order M{\o}ller−Plesset perturbation theory (MP2) level as well as implicit solvent effects accounted for using the polarizable continuum model (PCM). This led us to define the MP2/6-31+G(d):HF/6-31+G(d)/IEFPCM scheme as an efficient ONIOM approach and the MP2/6-31+G(d):HF/6-31G(d)/IEFPCM as a better compromise between accuracy and computational needs. Using these methods, we demonstrate that many parameters play a role on the β response of FPs, including the length of the π - conjugated segment, the variation of the bond length alternation, and the presence of π -stacking interactions. Then, noticing the small diversity of the FP chromophores, these results highlight the key role of the β -barrel and surrounding residues on β , not only because they can locally break the noncentrosymmetry vital to a β response but also because it can impose geometrical constraints on the chromophore.",
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ONIOM Investigation of the Second-Order Nonlinear Optical Responses of Fluorescent Proteins. / De Wergifosse, Marc; Botek, Edith; De Meulenaere, Evelien; Clays, K.; Champagne, Benoît.

In: Journal of physical chemistry A, Vol. 122, No. 19, 17.05.2018, p. 4993-5005.

Research output: Contribution to journalArticle

TY - JOUR

T1 - ONIOM Investigation of the Second-Order Nonlinear Optical Responses of Fluorescent Proteins

AU - De Wergifosse, Marc

AU - Botek, Edith

AU - De Meulenaere, Evelien

AU - Clays, K.

AU - Champagne, Benoît

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