Hydrogen/Deuterium Exchange Reaction Rate of Cytochrome Determined by Droplet Collision Atmospheric Pressure Infrared Laser Ablation Mass Spectrometry.

The hydrogen/deuterium (H/D) exchange rate is an optimal measure for studying the structures and dynamics of hydrogen bonding systems, as it reflects the molecular contact environment and the strength of the hydrogen bonds. A method for rapid measurement of the H/D exchange reaction rates is required to examine the intermolecular environments of molecules in solutions. We developed a droplet collision atmospheric pressure infrared laser ablation mass spectrometry technique for this purpose.

Cavity-Enhanced Fluorescence in Colliding Droplets of Rhodamine 6G Aqueous Solutions.

A liquid droplet can act as a microscale high-Q optical cavity via a whispering gallery mode, where light resonates with enhanced intensity. A collision of two droplets temporarily exhibits a unique morphology, which provides a more effective optical cavity than a single droplet. We investigated the mechanisms of cavity-enhanced fluorescence in colliding droplets of aqueous rhodamine 6G.

Stimulated Raman Scattering of an Organic Liquid in a Spherical-Shell Optical Cavity around an Aqueous Pendant Drop.

Stimulated Raman scattering (SRS) in a liquid droplet enhances the Raman scattering intensity through optical resonances. We have previously used a pendant drop at the tip of a capillary as the Raman-enhancing medium. In this study, we develop a new optical cavity for SRS measurement that consists of a spherical shell of organic liquid.

Carborane as an Alternative Efficient Hydrophobic Tag for Protein Degradation.

Carboranes and were designed and synthesized for hydrophobic tag (HyT)-induced degradation of HaloTag fusion proteins. The levels of the hemagglutinin (HA)-HaloTag2-green fluorescent protein (EGFP) stably expressed in Flp-In 293 cells were significantly reduced by HyT13, HyT55, and carboranes and , with expression levels of 49, 79, 43, and 65%, respectively, indicating that carborane is an alternative novel hydrophobic tag (HyT) for protein degradation under an intracellular environment. To clarify the mechanism of HyT-induced proteolysis, bovine serum albumin (BSA) was chosen as an extracellular protein and modified with maleimide-conjugated -carborane (MIC).

Chemical Reactions at the Interface Periphery of Colliding Droplets Studied by Raman Image Analysis.

Chemical reactions at the interface of reactive solutions are of importance for a full understanding of solution reactions. We investigate the chemical reaction induced by the collision of two droplets. The extent of the reaction is measured by analyzing spectra and images of the Raman scattered light emerging from the interface of the colliding droplets of HSO and NH aqueous solutions.

Gas-Phase Resonance Raman Spectroscopy Combined with IR-Laser Ablation of a Droplet Beam: Local Structural Analysis of Myoglobin.

Gas phase spectroscopy is a powerful tool for examining fundamental chemical structures and properties free from solvent molecules. We developed a gas-phase resonance Raman spectroscopy combined with IR-laser ablation of a droplet beam, which allowed us to elucidate local structures around chromophores in gas-phase proteins and DNAs. To demonstrate the potential of this approach, we applied this method to myoglobin, one of the heme proteins, and elucidated its structures in the gas phase and in aqueous solution.

Gas-phase hydration of the lysozyme ion produced by infrared-laser ablation of a droplet beam studied by photodissociation and fluorescence spectroscopy.

Biomolecules function in an aqueous environment. Elucidation of the hydration structures of biomolecules is hence important to understand their functions. Here, we investigated the hydration structure of lysozyme (Lys) in the gas phase by photodissociation and fluorescence spectroscopy in combination with droplet-beam laser ablation mass spectrometry.

Low-Frequency Raman Scattering in Colliding Benzene Droplets.

Low-frequency intermolecular motions are of importance for understanding the structure of molecular liquids, which can be elucidated by Raman spectroscopy. A liquid droplet provides a field where stimulated Raman scattering (SRS) readily proceeds. Our previous study showed that multiorder SRS is more effectively generated in colliding droplets than a single droplet.

Design of S-S bond containing maleimide-conjugated closo-dodecaborate (SSMID): identification of unique modification sites on albumin and investigation of intracellular uptake.

An S-S bond containing maleimide-conjugated closo-dodecaborate (SSMID) was synthesised for identification of albumin binding sites. Three Lys residues, Lys221, Lys413 and Lys431, were identified as SSMID modification sites in addition to Cys34 in bovin serum albumin (BSA). Fluorescent-labelled MID-BSA was found to be accumulated in the cytosol of HeLa cells.

Multiorder Stimulated Raman Scattering in Colliding Droplets.

Nonlinear Raman spectroscopy is a versatile method to enhance the intensities of Raman scattering. It requires an intense light field that can be provided by a liquid droplet acting as a high-quality optical cavity. Here, colliding droplets were used as a novel optical cavity to enhance the intensity of Raman scattering.

Initial Collision Process of Two Miscible Droplets.

Dynamic properties of the metastable interface between two miscible solutions are investigated by the collision of two droplets. A clear interface is observed between the two colliding droplets. The interface moves in the colliding droplet toward the side where the original droplet has a lower surface tension.

Nanosecond pump-probe device for time-resolved serial femtosecond crystallography developed at SACLA.

X-ray free-electron lasers (XFELs) have opened new opportunities for time-resolved X-ray crystallography. Here a nanosecond optical-pump XFEL-probe device developed for time-resolved serial femtosecond crystallography (TR-SFX) studies of photo-induced reactions in proteins at the SPring-8 Angstrom Compact free-electron LAser (SACLA) is reported. The optical-fiber-based system is a good choice for a quick setup in a limited beam time and allows pump illumination from two directions to achieve high excitation efficiency of protein microcrystals.

Evaporation and Subsequent Adsorption of Alcohol Molecules at Aqueous Droplet Surface Observed by Cavity-Enhanced Raman Spectroscopy.

Mass transfer toward and across liquid surfaces is important for the interpretation of various interfacial phenomena, such as evaporation, adsorption, and mass accommodation, which have been investigated by the use of various methods. These studies, however, have focused on only one of the mass-transfer processes occurring at the surface. We investigate the surface concentration of alcohol molecules at aqueous droplet surfaces on the several-millisecond time scale using cavity-enhanced droplet Raman spectroscopy.

Development of a Tandem Electrodynamic Trap Apparatus for Merging Charged Droplets and Spectroscopic Characterization of Resultant Dried Particles.

Materials work in multicomponent forms. A wide range of compositions must be tested to obtain the optimum composition for a specific application. We propose optimization using a series of small levitated single particles.

Microcrystal delivery by pulsed liquid droplet for serial femtosecond crystallography.

A liquid-droplet injector has been developed that delivers pristine microcrystals to an X-ray irradiation area for conducting serial femtosecond crystallography (SFX) with an X-ray free-electron laser (XFEL). By finely tuning the pulsed liquid droplets in time and space, a high hit rate of the XFEL pulses to microcrystals in the droplets was achieved for measurements using 5 µm tetragonal lysozyme crystals, which produced 4265 indexable diffraction images in about 30 min. The structure was determined at a resolution of 2.

Mechanism of Protein Molecule Isolation by IR Laser Ablation of Droplet Beam.

Gas-phase isolation of bovine serum albumin (BSA) from aqueous solutions is performed by IR laser ablation of a droplet beam. Multiply charged BSA ions (positive and negative) were produced by the IR laser irradiation onto a droplet beam of aqueous BSA solutions with various pH values prepared by addition of hydrochloric acid or sodium hydroxide to the solution. The isolation mechanism was discussed based on the charge state of the isolated BSA ions.

Coloring Rate of Phenolphthalein by Reaction with Alkaline Solution Observed by Liquid-Droplet Collision.

Many important chemical reactions are induced by mixing two solutions. This paper presents a new way to measure rates of rapid chemical reactions induced by mixing two reactant solutions using a liquid-droplet collision. The coloring reaction of phenolphthalein (H2PP) by a reaction with NaOH is investigated kinetically.

Simultaneous detection of images and Raman spectra of colliding droplets: composition analysis of protrusions emerging during collisions of ethanol and water droplets.

Processes involved between colliding droplets were investigated using simultaneous analysis of spectra and images of Raman-scattered light emitted by irradiation with a pulsed laser. This enabled spatially and temporally resolved Raman spectra of the colliding droplets to be obtained. Colliding droplets of ethanol and water produce a characteristic protrusion from the contact point to the antipode of the water droplet in the course of interaction.

Charge state of lysozyme molecules in the gas phase produced by IR-laser ablation of droplet beam.

Molecules exhibit their intrinsic properties in their isolated forms. Investigations of isolated large biomolecules require an understanding of the detailed mechanisms for their emergence in the gas phase because these properties may depend on the isolation process. In this study, we apply droplet-beam laser-ablation mass spectrometry to isolate protein molecules in the gas phase by IR-laser ablation of aqueous protein solutions, and we discuss the isolation mechanism.

Nanoscale soldering of metal nanoparticles for construction of higher-order structures.

We demonstrated that platinum nanoparticles dispersed in pure water were "soldered" by gold into higher-order structures such as "nanowebs". In practice, gold nanoparticles in water containing the platinum nanoparticles were melted by irradiation of a pulsed 532-nm laser, which excites selectively the surface plasmon band of the gold nanoparticles, and the melted gold nanoparticles solder the platinum nanoparticles together into the nanowebs. Optical absorption spectroscopy and electron microscopy together with electron probe microanalysis were employed to observe the structure of the nanowebs and to elucidate their formation dynamics.