Antibodies for fluorescent molecular rotors

Iwaki, Tomomichi; Torigoe, Chikako; Noji, Masahide; Nakanishi, Mamoru

doi:10.1021/bi00080a034

Cited by 81 publications

(84 citation statements)

References 21 publications

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“…Of particular interest are some dyes with segmental mobility that are capable of an intramolecular twisting motion in the excited state [6], which are often referred to as "molecular rotors" [7,8]. Those molecules have two competing deexcitation pathways: (a) a pathway in which the molecule remains in a planar conformation when it returns to the ground state, and (b) a pathway in which the molecule assumes a twisted state before returning to the ground state.…”

Section: Introductionmentioning

confidence: 99%

Apparent Shear Sensitivity of Molecular Rotors in Various Solvents

et al. 2015

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Fluorescent environment-sensitive dyes often change their spectral properties concomitantly with multiple solvent properties, such as polarity, protonation, hydrogen bond formation, or viscosity. Careful consideration of the response is needed when a fluorescent dye is used to report a single property. Recently, we observed an increase of emission intensity of viscosity-sensitive molecular rotors in fluids subject to flow and speculated that either polar-polar interaction or hydrogen bond formation play a role in the apparent flow sensitivity. In this study, we show experimental evidence that photoisomerization to an isomer with a lower quantum yield, first proposed by Rumble et al. (J Phys Chem A 116(44):10786-10792, 2012), plays a key role in the observed phenomenon. We subjected four molecular rotors with different electron acceptor motifs to fluid flow in solvents of different polarity and ability to form hydrogen bonds. We also measured the isomerization dynamics in a custom fluorophotometer with extremely low light exposure. Our results indicate that the photoisomerization rate depends both on the solvent and on the electron acceptor group, as does the recovery of the original isomer in the dark. In most solvents, recovery of the dark isomer is much more rapid than originally reported, and a state of quasiequilibrium between both isomers is possible. Moreover, the sensitivity (i.e., relative intensity increase at the same flow rate) is also solvent-dependent. The intensity increase can be detected at very low velocities (as low as 0.06 mm/s). Characteristic for fluorescent dyes is the high spatial resolution, and no flow measurement device with comparable sensitivity and spatial resolution exists, although the nature of the solvent needs to be taken into account for quantitative flow measurement.

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Section: Introductionmentioning

confidence: 99%

Apparent Shear Sensitivity of Molecular Rotors in Various Solvents

et al. 2015

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“…It was shown that the fluorescence lifetime for another malononitrile, 9-(2-carboxy-2-cyanovinyl)julolidine (CCVJ) increased by more than a factor of 5 upon binding of an antibody. [34] Functionalising a similar molecule with a hydrophobic Figure 1. Example ground-(S 0 ) and excited-state (S 1 ) potential energy surfaces for a molecular rotor as a function of intramolecular torsional angle.…”

Section: Introductionmentioning

confidence: 99%

Fluorescence Anisotropy of Molecular Rotors

et al. 2011

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We present polarization-resolved fluorescence measurements of fluorescent molecular rotors 9-(2-carboxy-2-cyanovinyl)julolidine (CCVJ), 9-(2,2-dicyanovinyl)julolidine (DCVJ), and a meso-substituted boron dipyrromethene (BODIPY-C(12)). The photophysical properties of these molecules are highly dependent on the viscosity of the surrounding solvent. The relationship between their quantum yields and the viscosity of the surrounding medium is given by an equation first described and presented by Förster and Hoffmann and can be used to determine the microviscosity of the environment around a fluorophore. Herein we evaluate the applicability of molecular rotors as probes of apparent viscosity on a microscopic scale based on their viscosity dependent fluorescence depolarization. We develop a theoretical framework, combining the Förster-Hoffmann equation with the Perrin equation and compare the dynamic ranges and usable working regimes for these dyes in terms of utilising fluorescence anisotropy as a measure of viscosity. We present polarization-resolved fluorescence spectra and steady-state fluorescence anisotropy imaging data for measurements of intracellular viscosity. We find that the dynamic range for fluorescence anisotropy for CCVJ and DCVJ is significantly lower than that of BODIPY-C(12) in the viscosity range 0.6<η<600 cP. Moreover, using steady-state anisotropy measurements to probe microviscosity in the low (<3 cP) viscosity regime, the molecular rotors can offer a better dynamic range in anisotropy compared with a rigid dye as a probe of microviscosity, and a higher total working dynamic range in terms of viscosity.

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“…5,9 Increased glycerol content is known to increase viscosity with only minimal changes of solvent polarity. 10 Glycerol contents of 40, 50, 60, 70, and 80% resulted in viscosities of 72, 109, 165, 248, and 374 mPa‚s, respectively.…”

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confidence: 99%

A Ratiometric Fluorescent Viscosity Sensor

et al. 2005

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Variations in fluid viscosity are linked to a variety of functions and diseases both at the cellular level (e.g., membrane and cytoplasmic viscosity changes in cell signaling modulation) 1 and at the organismal level (e.g., blood, plasma, or lymphatic fluid viscosity changes in diabetes, hypertension, infarction, and aging). 2 It has been proposed that monitoring of biofluid viscosity could provide a diagnostic tool for the detection of diseases. 3 Since mechanical devices do not provide the spatial and temporal resolution needed, a new type of fluorescent-based viscosity sensors was developed. 4 These sensors are based on a class of environmentsensitive fluorescent dyes that are characterized by a viscositydependent emission quantum yield. 4,5 The chemical structure of these dyes contains an electron donor unit (such as a nitrogen atom) in conjugation with an electron acceptor unit (such as a nitrile). Upon photoexcitation, the two units can rotate relative to each other in a manner that is dependent on the viscosity of their environment. Representative examples of such fluorescent rotors are 9-(dicyanoVinyl)julolidine (DCVJ, 1) and 2-cyano-3-(4-dimethylaminophenyl)acrylic acid methyl ester (CMAM, 2) ( Figure 1). 5 Their viscosity-dependent fluorescent quantum yield is described by the Förster-Hoffmann equation (eq 1). 6 Fluorescent molecular rotors have been used for viscosity studies that are performed by steady-state fluorescence through emission intensity measurements. This method suffers, however, from drawbacks arising from changes of the fluid optical properties and fluctuations in dye concentrations. An additional disadvantage is that a calibration curve is needed for the absolute determination of viscosity. 5 As a consequence, changes in fluid properties and dye concentration may cause erroneous readings.We hypothesized that a dual dye composed of two distinct fluorescent units, one providing an internal intensity reference and the other acting as a viscosity sensor, would create a ratiometric sensing system, thus overcoming the above disadvantages. Dividing the sensor emission intensity by the reference emission intensity would yield a normalized intensity that should not only eliminate some of the fluid-and concentration-related artifacts but also provide a means to quantify viscosity by an internal reference. To test this hypothesis, we synthesized a compound 4 in which the CMAM motif was coupled with 7-methoxycoumarin-3-carboxylic acid (MCCA, 3). We chose MCCA as the donor fluorophore in order to induce excitation of the rotor moiety (CMAM) via Resonance Energy Transfer (RET). 7 We envisioned that, due to its viscosity-independent quantum yield, MCCA could be used as both the internal reference and the RET donor. The latter event could then excite the CMAM motif, resulting in a viscosity-dependent emission of the rotor. The linker was chosen to maintain a distance between the chromophores in the same range as the Förster distance 7a to allow considerable energy transfer to the acceptor combined w...

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Antibodies for fluorescent molecular rotors

Cited by 81 publications

References 21 publications

Apparent Shear Sensitivity of Molecular Rotors in Various Solvents

Apparent Shear Sensitivity of Molecular Rotors in Various Solvents

Fluorescence Anisotropy of Molecular Rotors

A Ratiometric Fluorescent Viscosity Sensor

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