Revealing the Role of Electronic Effect to Modulate the Photophysics and Z-Scan Responses of -Locked GFP Chromophores.

Three novel core green fluorescent protein (GFP) chromophore analogues, based on a doubly locked conformation and variable electronic effects by replacing one hydrogen with bromine, iodine, and methyl, respectively, have been synthesized to modulate the push-pull effect. These chromophores exhibited intramolecular H-bonding, as evidenced by single-crystal X-ray and H NMR studies. The fluorescence quantum yields (ϕ) of all of the chromophores were found to be more than an order of magnitude higher (∼0.

Aggregation-Induced Modulation of Ground and Excited State Photophysics of 5-(-Butyl)-2-Hydroxy-1,3-Isophthalaldehyde (5-BHI).

5-(-Butyl)-2-hydroxy-1,3-isophthalaldehyde (5-BHI) is a photochromic material susceptible to either excited state proton transfer or excited state intramolecular proton transfer, depending upon the solvent. However, it has also been found to aggregate in the presence of sodium dodecyl sulfate. In this current study, based on the steady-state and time-resolved spectroscopy, supported by crystallography, quantum chemical density functional theory calculation, and molecular dynamics (MD) simulation, we report on the aggregation of this potential single benzene-based emitter (SBBE) in neat solvents as well as solid phase to modulate its photophysics.

Non-trivial ground and excited state photophysics of a substituted phenol.

5-(-Butyl)-2-hydroxy-1,3-isophthalaldehyde (5-BHI) shows solvent dependent single or dual emission. The photophysics of 5-BHI has been studied in a variety of solvents and the results were compared with that of the methyl derivative of the probe as well as the 5-BHI anion. It has been found that the intramolecular H-bonded conformer of 5-BHI predominantly exists in non-polar solvents, and undergoes facile excited state intramolecular proton transfer (ESIPT).

Unusual absence of FRET in triazole bridged coumarin-hydroxyquinoline, an active sensor for Hg2+ detection.

A triazole-bridged coumarin conjugated quinoline sensor has been 'click'-synthesized by Cu(i) catalyzed Huisgen cycloaddition, and it exhibited high selectivity for toxic Hg2+. Surprisingly, no evidence of energy transfer from the quinoline moiety to coumarin has been found, substantiated by time-resolved fluorescence study. The possible binding mode of this sensor to Hg2+ has been established via NMR study, steady-state and time-resolved fluorescence spectroscopy, which is further supported by TDDFT calculations.

Room-Temperature Dual Fluorescence of a Locked Green Fluorescent Protein Chromophore Analogue.

A structurally locked green fluorescent protein (GFP) chromophore with a phenyl group at C(2) of the imidazolone has been synthesized. Rotation around the exocyclic double bond is hindered, resulting in room-temperature fluorescence. The quantum yield in water is 500 times greater than that of unlocked analogues.

Excited state dynamics of brightly fluorescent second generation epicocconone analogues.

The natural product epicocconone, owing to its unique fluorescence properties, has been developed into a range of products used in biotechnology, especially proteomics. However, its weak green fluorescence in its native state, while advantageous for proteomics applications, is a disadvantage in other applications that require two-color readouts. Here we report the photophysical characterization of two brightly fluorescent analogues of epicocconone.

The role of different structural motifs in the ultrafast dynamics of second generation protein stains.

Engineering the properties of fluorescent probes through modifications of the fluorophore structure has become a subject of interest in recent times. By doing this, the photophysical and photochemical properties of the modified fluorophore can be understood and this can guide the design and synthesis of better fluorophores for use in biotechnology. In this work, the electronic spectra and fluorescence decay kinetics of four analogues of the fluorescent natural product epicocconone were investigated.

Ultrafast dynamics of epicocconone, a second generation fluorescent protein stain.

Femtosecond upconversion experiment has been carried out for epicocconone and its butylamine adduct in acetonitrile and tert-butanol. An ultrafast component is found to dominate the decay of fluorescence of epicocconone in acetonitrile solution. Upon reacting with butylamine, a model for the epicocconone-protein adduct, this ultrafast component remains almost unaffected but an additional rise time occurs, indicating the formation of a highly emissive species from the locally excited state.

Role of spacer in single- or two-step FRET: studies in the presence of two connected cryptands with properly chosen fluorophores.

Two cryptand molecules are connected via p-xyloyl, benzene-1,4-dicarbolyol and 9,10-dimethylene anthracene. Each cryptand is further derivatized with fluorophores such that electronic absorption of one fluorophore overlaps emission of the other. This way, three different systems L(1), L(2) and L(3) have been synthesized to get a better view of the effect on the distance in single- and two-step fluorescence resonance energy transfer (FRET) process.