Reactant concentrations from fluorescence correlation spectroscopy with tailored fluorescent probes. An example of local calibration-free pH measurement

The present account is concerned with the measurement of local reactant concentrations by observing specific fluorescent probes in fluorescence correlation spectroscopy (FCS). The Theoretical Analysis section revisits the photophysical, thermodynamic, and kinetic information that is contained in the corresponding FCS correlation curves. In particular, we examine the conditions under which FCS is revealed as a superior tool to measure concentrations of reactive species. Careful molecular engineering of the specific fluorescent probes that simultaneously integrates photophysical, thermodynamic, and kinetic constraints will be required to benefit most from FCS. We illustrate the FCS titration approach with a series of fluorescent probes that we tailored to measure pH at around 4-6 by FCS after two-photon excitation. We show that an optimal design allows one to access pH without any preliminary calibrations such as the determination of the protonation constant or the photophysical properties of the fluorescent probe.     

6π/10π-Electrocyclization of ketene-iminium salts for the synthesis of substituted naphthylamines

An intramolecular 6π/10π-electrocyclization from ketene-iminium salts was developed for the preparation of naphthylamines. Various substituents on the nitrogen, on the aromatic ring, and on the olefin were studied. Tricyclic skeletons were obtained in few steps and good overall yields. The electrocyclization of ketene-iminium salts has been computationally explored by means of DFT calculations and their activation barriers were compared to the parent triene as well as the corresponding dienyl allenes and dienyl ketenes. Electrocyclizations for ketene-iminium salts were shown to be highly exergonic and have much smaller barriers to activation.     

Macromolecular surfactants for miniemulsion polymerization

The use of polymeric surfactants as stabilizers in miniemulsion polymerization was reviewed. The structural characteristics of reported polymeric surfactants were detailed and compared. The concept of multi-functional polymeric surfactants was evidenced. The specificities brought by polymeric surfactants in the process of miniemulsion polymerization in comparison to molecular surfactants were analysed for the stability of the initial monomer emulsion, polymerization kinetics and characteristics of the obtained latexes. The contribution of polymeric surfactants to the control of the characteristics of the obtained nanoparticles was detailed with regard to the nature of the core material and to the surface coverage. Polymeric surfactants can be seen as powerful tools for the design of original nanoparticles. On the basis of the available data, possible research topics are suggested.     

Alkynylgold(I) C3-Chiral Concave Complexes: Aggregation and Luminescence

Chiral gold(I) acetylide trinuclear complexes 1 – 3 based on the cyclotribenzylene platform and terminal PR₃ ligands (R=Ph, Et, and Cy, respectively), were characterized and their light emission studied. They exhibited long-lived blue phosphorescence in CHCl₃ and a weak fluorescence in the UV. In MeOH/CHCl₃ mixtures of >1:1 volume ratio, 1 and 2 exhibited a new emission band at ca. 540 nm that developed at the expense of the UV emission. DLS studies demonstrated the presence of molecular aggregates of Ø 30–80 nm. The green emission observed in MeOH-rich solvent mixtures was therefore induced by aggregation, and could originate from Au⋅⋅⋅Au interactions. The AIE spectrum of 3 was observed only in solutions containing 99 % of MeOH, and correlated with its solid state emission. The AIE profiles of the enantiomers of 1 differed from that of rac- 1 , suggesting that the latter is a true racemate.     

Pseudo-moderate deviations in the euler method for real diffusion process

We consider the problem of the non-sequential detection of a change in the drift coefficient of a stochastic differential equation, when a misspecified model is used. We formulate the generalized likelihood ratio (GLR) test for this problem, and we study the behaviour of the associated error probabilities (false alarm and nodetection) in the small noise asymptotics. We obtain the following robustness result: even though a wrong model is used, the error probabilities go to zero with exponential rate, and the maximum likelihood estimator (MLE) of the change time is consistent, provided the change to be detected is larger (in some sense) than the misspecification error. We give also computable bounds for selecting the threshold of the test so as to achieve these exponential rates.     

Design of polymeric nanoparticles for the encapsulation of monoacylglycerol

Dextran-covered nanoparticles were produced by two different processes: emulsion/solvent evaporation and nanoprecipitation for the encapsulation of monomyristin. The inner core was formed by poly(lactic acid) or by a hydrophobically modified dextran (carrying n-decyl chains). According to the core materials and/or to the process, the average size of nanoparticles as well as the extent of aggregate formation was modulated. It was shown that the presence of monomyristin induced significant modifications on the characteristics of the resulting suspension (size and aggregate formation). Varying the matrix polymer as well as the amount of monomyristin in the feed allowed obtaining nanoparticles with convenient size. The use of hydrophobically modified dextran as the matrix material appeared promising.     

On-tissue protein identification and imaging by MALDI-Ion mobility mass spectrometry

MALDI imaging mass spectrometry (MALDI-IMS) has become a powerful tool for the detection and localization of drugs, proteins, and lipids on-tissue. Nevertheless, this approach can only perform identification of low mass molecules as lipids, pharmaceuticals, and peptides. In this article, a combination of approaches for the detection and imaging of proteins and their identification directly on-tissue is described after tryptic digestion. Enzymatic digestion protocols for different kinds of tissues—formalin fixed paraffin embedded (FFPE) and frozen tissues—are combined with MALDI-ion mobility mass spectrometry (IM-MS). This combination enables localization and identification of proteins via their related digested peptides. In a number of cases, ion mobility separates isobaric ions that cannot be identified by conventional MALDI time-of-flight (TOF) mass spectrometry. The amount of detected peaks per measurement increases (versus conventional MALDI-TOF), which enables mass and time selected ion images and the identification of separated ions. These experiments demonstrate the feasibility of direct proteins identification by ion-mobility-TOF IMS from tissue. The tissue digestion combined with MALDI-IM-TOF-IMS approach allows a proteomics “bottom-up” strategy with different kinds of tissue samples, especially FFPE tissues conserved for a long time in hospital sample banks. The combination of IM with IMS marks the development of IMS approaches as real proteomic tools, which brings new perspectives to biological studies.