First-Order Hyperpolarizability Of Triphenylamine Derivatives Containing Cyanopyridine: Molecular Branching Effect

In the present work, we report the multibranching effect on the dynamic first-order hyperpolarizability (β(-2ω; ω, ω)) of triphenylamine derivatives containing cyanopyridine one-branch (dipolar structure), two-branch (V-shaped structure), and three-branch (octupolar structure) structures. For this study, we used the hyper-Rayleigh scattering (HRS) technique involving picosecond pulse trains at 1064 nm. Our results show that βHRS increases from 2.02 × 10-28 to 9.24 × 10-28 cm5/esu when an extra branch is added to the molecule, configuring a change from a dipolar to a V-shaped (quadrupolar) molecular structure. When a third branch is added, leading to an octupolar structure, a decrease to 3.21 × 10-28 cm5/esu is observed. Such a significant decrease in βHRS is attributed to a negative contribution presented in the βHRS description by using a three-level energy approach due to their electronic structure and considering a specific combination of the angle between the dipole moments. On the other hand, the enhancement of βHRS found for the quadrupolar structure is associated with the cooperative enhancement due to the electronic coupling between the branches that increases considerably the transition dipole moment and permanent dipole moment change. To explain the βHRS results obtained for different molecules, we employed the HRS figure of merit, FOMHRS = βHRS/Neff 3/2, in which Neff is the effective number of π-conjugated bonds, and the few-energy level approach for βHRS within the Frenkel exciton model. To shed more light on the experimental results interpretation, we performed time-dependent density functional theory calculations combined with a polarizable continuum model to confirm the energy and oscillator strength of the electronic transitions assumed in the Frenkel exciton model employed here

Quadruple Functionalization of a Tetraphenylethylene Aromatic Scaffold with Ynamides or Tetracyanobutadienes: Synthesis and Optical Properties

International audienceYnamides are useful and versatile building blocks in organic synthesis, from which 1,1,4,4-tetracyanobutadienes (TCBD) can be prepared for application in molecular electronics. However, their insertion onto multi-functional molecular scaffold remains a synthetic challenge. In this work, we report the two-steps synthesis in good isolated yield (64 % overall, 89 % stepwise) of a tetraphenylethylene (TPE) bearing four ynamides, and its further one-step conversion into the tetra-TCBD derivative through a [2 + 2] cycloaddition-retroelectrocyclization sequence. The concomitant formation of the four ynamides required a specific optimisation of the reaction conditions. Although a poor fluorescent emitter in solution, the tetra-TCBD compound displayed near-infrared luminescence in the solid state, which is an attractive optoelectronic feature when considering future applications in molecular electronic devices

New designed naphthalimide-phthalocyanine pentads: Synthesis, photophysical and photochemical properties in DMSO and room temperature ionic liquids

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Specific detection of cysteine sulphenic acid by coupling Mass Spectrometry with Laser Induced Dissociation

International audienceImprovement of oxidative stress induced modification of cysteine residues detection. Protein cysteine residues are oxidized into sulphenic acid (SOH), derivatized with a specific chromophore and specificaly detected and identified thanks to Laser Induced Dissociation (LID) in the visible range. In a context of population aging, discovery and validation of novel oxidative stress biomarkers for screening of neurodegenerative diseases is a key issue. One of the modification induced by reactive oxygen species (ROS) is the oxidation of protein cysteine (Cys) residues . As this oxidative process is minor, the detection of these oxidized proteins at low concentrations is problematic due to the complexity and dynamic concentration range of the samples to be analyzed. In order to improve the detection specificity for oxidized proteins, we use an experimental setup coupling mass spectrometry and laser induced dissociation (LID) in the visible range (473 nm) to add a stringent optical specificity to the mass selectivity

Relative quantification of sulfenic acids in plasma proteins using differential labelling and mass spectrometry coupled with 473 nm photo-dissociation analysis: A multiplexed approach applied to an Alzheimer's disease cohort

International audienceCysteine (Cys) is subject to a variety of reversible post-translational modifications such as formation of sulfenic acid (Cys-SOH). If this modification is often involved in normal biological activities, it can also be the result of oxidative damage. Indeed, oxidative stress yields abnormal cysteine oxidations that affect protein function and structure and can lead to neurodegenerative diseases. In a context of population ageing, validation of novel biomarkers for detection of neurodegenerative diseases is important. However, Cys-SOH proteins investigation in large human cohorts is challenging due to their low abundance and lability under endogenous conditions. To improve the detection specificity towards the oxidized protein subpopulation, we developed a method that makes use of a mass spectrometer coupled with visible laser induced dissociation (LID) to add a stringent optical specificity to the mass selectivity. Since peptides do not naturally absorb in the visible range, this approach relies on the proper chemical derivatization of Cys-SOH with a chromophore functionalized with a cyclohexanedione. To compensate for the significant variability in total protein expression within the samples and any experimental bias, a normalizing strategy using free thiol (Cys-SH) cysteine peptides derivatized with a maleimide chromophore as internal references was used. Thanks to the differential tagging, oxidative ratios were then obtained for 69 Cys-containing peptides from 19 proteins tracked by parallel reaction monitoring (PRM) LID, in a cohort of 49 human plasma samples from Alzheimer disease (AD) patients. A statistical analysis indicated that, for the proteins monitored, the Cys oxidative ratio does not correlate with the diagnosis of AD. Nevertheless, the PRM-LID method allows the unbiased, sensitive and robust relative quantification of Cys oxidation within cohorts of samples

Specific detection of cysteine sulphenic acid by coupling Mass Spectrometry with Laser Induced Dissociation

International audienceOverview Improvement of oxidative stress induced modification of cysteine residues detection. Protein cysteine residues are oxidized into sulphenic acid (SOH), derivatized with a specific chromophore and specificaly detected and identified thanks to Laser Induced Dissociation (LID) in the visible range Chromophore derivatization of cysteine sulphenic aci

Unbiased Detection of Cysteine Sulfenic Acid by 473 nm Photodissociation Mass Spectrometry: Toward Facile In Vivo Oxidative Status of Plasma Proteins

International audienceCysteine (Cys) is prone to diverse post-translational modifications in proteins, including oxidation into sulfenic acid (Cys-SOH) by reactive oxygen species generated under oxidative stress. Detection of low concentrated and metastable Cys-SOH within complex biological matrices is challenging due to the dynamic concentration range of proteins in the samples. Herein, visible laser-induced dissociation (LID) implemented in a mass spectrometer was used for streamlining the detection of Cys oxidized proteins thanks to proper derivatization of Cys-SOH with a chromophore tag functionalized with a cyclohexanedione group. Once grafted, peptides undergo a high fragmentation yield under LID, leading concomitantly to informative backbone ions and to a chromophore reporter ion. 79 % of the Cys-containing tryptic peptides deriving from human serum albumin and serotransferrin tracked by Parallel Reaction Monitoring (PRM) were detected as targets subjected to oxidation. These candidates, as well as Cys-containing peptides predicted by in silico trypsin digestion of 5 other human plasma proteins, were then tracked in real plasma samples to pinpoint the endogenous Cys-SOH subpopulation. Most of the targeted peptides were detected in all plasma samples by LID-PRM, with significant differences in their relative amounts. By eliminating the signal of interfering co-eluted compounds, LID-PRM surpasses conventional HCD-PRM in detecting grafted Cys-SOH containing peptides and allows now to foresee clinical applications in large human cohorts

Novel pH-sensitive probes with a ratiometric detection for intracellular pH

International audienceThe development of new pH-sensitive fluorescent probes based on a push-pull architecture is presented with a 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofurane as strong electron acceptor group. With a small structural change, it is possible to obtain a large range of phenolic pKa from 4.8 to 8.6 with some close to neutrality, underlining the role of the electron density modulation on the acidic properties. Remarkable changes in the optical properties (both absorption and fluorescence) were observed as a function of the pH. Ratiometric imaging of intracellular pH was carried out with the most promising probes and highlighted the possibility to distinguish near-neutral minor pH fluctuations in cells

Fluorescent push–pull pH-responsive probes for ratiometric detection of intracellular pH

International audienceA family of fluorescent push-pull pH-responsive probes based on 2-dicyanomethylidene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran as a strong electron acceptor group is described. Small structural variations allow obtaining pK(a) ranging from 4.8 to 8.6, underlining the role of the substituent in modulating the acidic properties. Remarkable changes in the optical properties (in particular the fluorescence intensity ratios) were observed as a function of pH. The most interesting probes with pK(a) close to neutrality were used for ratiometric imaging of intracellular pH