Tunable Probes with Direct Fluorescence Signals for the Constitutive and Immunoproteasome

Electrophiles are commonly used for the inhibition of proteases. Notably, inhibitors of the proteasome, a central determinant of cellular survival and a target of several FDA‐approved drugs, are mainly characterized by the reactivity of their electrophilic head groups. We aimed to tune the inhibitory strength of peptidic sulfonate esters by varying the leaving groups. Indeed, proteasome inhibition correlated well with the pK_a of the leaving group. The use of fluorophores as leaving groups enabled us to design probes that release a stoichiometric fluorescence signal upon reaction, thereby directly linking proteasome inactivation to the readout. This principle could be applicable to other sulfonyl fluoride based inhibitors and allows the design of sensitive probes for enzymatic studies.     

Squaraine dyes: The hierarchical synthesis and its application in optical detection

Squaraine dyes, a four-membered ring system with structural rigidity, possess unique photoelectrical properties and are marked by their exceptionally sharp and intense absorption associated with a strong fluorescent emission in solution. These favorable characteristics have prompted their exploitation in a number of state of the art applications including photoconductivity, data storage, light-emitting field-effect transistors, solar cells and fluorescent histological probes. In this review, we first summarize the recently proposed novel methods in the synthesis of these versatile derivatives. Subsequently, their extensive applications in the prevalent optical detection of the surrounding medium such as ions, pH, thiol-based compounds, biomolecules and cell over the past decades are covered and discussed. In addition, different categories for the synthesis and sensing mechanisms for various squaric acid-based chemo-/bio- sensors are illustrated. Finally, the challenges and opportunities in the synthesis and application of these derivatives are also briefly discussed.     

MONOMETALLIC SOLVENT STABILIZED TRANSITION METAL CATIONS AS INITIATORS FOR CYCLOPENTADIENE POLYMERIZATION

Several mononuclear transition metal cations stabilized by acetonitrile molecules act as initiators for the polymerization of cyclopentadiene. The highest yield is reached with Cr, Mn, Fe, and Zn complexes, all of them in the oxidation state +II. The analogous V and Ni complexes, however, are completely or nearly inactive. In general, the observed activity of the examined monomeric complexes correlates well with the ligand field stabilization energy as a function of the number of d electrons for octahedrally coordinated transition metals in the oxidation state +II. The counter ions have a pronounced influence on the catalytic activity: the less coordinating they are, the higher is the activity of the cations. The reaction temperature also has a significant influence: above 50°C the complex activity is on decline, possibly due to initiator decomposition or com-petitive inhibition by dicyclopentadiene.     

Quaternary Ammonium Polyelectrolytes. V. Amination Studies of Chloromethylated Polystyrene with N,N-Dimethylalkylamines

The amination reactions of chloromethylated polystyrene with N,N-dimethyldodecylamine, N,N-dimethyltetradecylamine, and N,N-dimethylhexadecylamine were studied. The physical properties, particularly the solubility properties of the resulting polymers, are influenced by the hydrophobic properties of the long alkyl chain on the N⁺ atoms. The main factor that influences the kinetics of the reactions is the polymersolvent interaction parameter.     

Cationic Lanthanide Luminescent Copolymer: Design,Synthesis and Interaction with DNA

Polymerizable rare earth complex Eu(AA)₃Phen was synthesized by complexion of europium ion, acrylic acid (AA), and 1,10-phenanthroline (Phen). The structure and fluorescence properties of the complex were studied by elemental analysis, ¹H-NMR spectroscopy, and fluorescence spectroscopy. Eu-containing copolymer poly(PEGMA-co-MMA-co-METAC-co-Eu(AA)₃Phen) (PPMMEu) was then synthesized by free radical copolymerization of Eu(AA)₃Phen and other functional monomers including poly(ethylene glycol) methyl ether methacrylate (PEGMA) and [2-(Methacryloyloxy) ethyl] trimethylammonium chloride (METAC). ¹H-NMR spectroscopy and fluorescence spectroscopy were used to characterize the copolymer and the interactions between the copolymer and DNA was investigated by TEM, fluorescence spectroscopy, and agarose gel electrophoresis. The desired luminescent cationic copolymer was successfully obtained. The copolymer can form micelles in water solution and can efficiently bind to DNA molecules through electrostatic interaction. The results suggest the potential use of PPMMEu in bioprobes and gene vectors.