Chemical analysis of acoustically levitated drops by Raman spectroscopy

An experimental apparatus combining Raman spectroscopy with acoustic levitation, Raman acoustic levitation spectroscopy (RALS), is investigated in the field of physical and chemical analytics. Whereas acoustic levitation enables the contactless handling of microsized samples, Raman spectroscopy offers the advantage of a noninvasive method without complex sample preparation. After carrying out some systematic tests to probe the sensitivity of the technique to drop size, shape, and position, RALS has been successfully applied in monitoring sample dilution and preconcentration, evaporation, crystallization, an acid–base reaction, and analytes in a surface-enhanced Raman spectroscopy colloidal suspension

Unusual spectroscopic and photophysical properties of meso-tert-butylBODIPY in comparison to related alkylated BODIPY dyes

meso-t-Bu-BODIPY produces unusual spectroscopic and photophysical characteristics in comparison to those of related alkylated BODIPY dyes.</p

A photoinduced electron transfer-based nanoprobe as a marker of acidic organelles in mammalian cells

Photoinduced electron transfer (PET)-based molecular probes have been successfully used for the intracellular imaging of the pH of acidic organelles. In this study, we describe the synthesis and characterization of a novel PET-based pH nanoprobe and its biological application for the signaling of acidic organelles in mammalian cells. A fluorescent ligand sensitive to pH via the PET mechanism that incorporates a thiolated moiety was synthesized and used to stabilize gold nanoparticles (2.4?±?0.6 nm), yielding a PET-based nanoprobe. The PET nanoprobe was unambiguously characterized by transmission electron microscopy, proton nuclear magnetic resonance, Fourier transform infrared, ultraviolet-visible absorption, and steady-state/time-resolved fluorescence spectroscopies which confirmed the functionalization of the gold nanoparticles with the PET-based ligand. Following a classic PET behavior, the fluorescence emission of the PET-based nanoprobe was quenched in alkaline conditions and enhanced in an acidic environment. The PET-based nanoprobe was used for the intracellular imaging of acidic environments within Chinese hamster ovary cells by confocal laser scanning microscopy. The internalization of the nanoparticles by the cells was confirmed by confocal fluorescence images and also by recording the fluorescence emission spectra of the intracellular PET-based nanoprobe from within the cells. Co-localization experiments using a marker of acidic organelles, LysoTracker Red DND-99, and a marker of autophagosomes, GFP-LC3, confirm that the PET-based nanoprobe acts as marker of acidic organelles and autophagosomes within mammalian cells

Ubiquitin chain conformation regulates recognition and activity of interacting proteins

Mechanisms of protein recognition have been extensively studied for single-domain proteins1, but are less well characterized for dynamic multidomain systems. Ubiquitin chains represent a biologically important multidomain system that requires recognition by structurally diverse ubiquitin-interacting proteins2, 3. Ubiquitin chain conformations in isolation are often different from conformations observed in ubiquitin-interacting protein complexes, indicating either great dynamic flexibility or extensive chain remodelling upon binding. Using single-molecule fluorescence resonance energy transfer, we show that Lys 63-, Lys 48- and Met 1-linked diubiquitin exist in several distinct conformational states in solution. Lys 63- and Met 1-linked diubiquitin adopt extended \u27open\u27 and more compact \u27closed\u27 conformations, and ubiquitin-binding domains and deubiquitinases (DUBs) select pre-existing conformations. By contrast, Lys 48-linked diubiquitin adopts predominantly compact conformations. DUBs directly recognize existing conformations, but may also remodel ubiquitin chains to hydrolyse the isopeptide bond. Disruption of the Lys 48-diubiquitin interface changes conformational dynamics and affects DUB activity. Hence, conformational equilibria in ubiquitin chains provide an additional layer of regulation in the ubiquitin system, and distinct conformations observed in differently linked polyubiquitin may contribute to the specificity of ubiquitin-interacting proteins