A5030792542- Mass Spectrometry Techniques and Applications
- Nanocluster Synthesis and Applications
- Spectroscopy and Quantum Chemical Studies
- Ion channel regulation and function
- Magnetic properties of thin films
- Analytical Chemistry and Chromatography
- Nicotinic Acetylcholine Receptors Study
- Gold and Silver Nanoparticles Synthesis and Applications
- Advanced Chemical Physics Studies
- Molecular Sensors and Ion Detection
- Molecular Spectroscopy and Structure
- Advanced Nanomaterials in Catalysis
- Molecular spectroscopy and chirality
- Receptor Mechanisms and Signaling
- Inorganic Chemistry and Materials
- Molecular Junctions and Nanostructures
- Photochemistry and Electron Transfer Studies
- Photoreceptor and optogenetics research
- Electrochemical Analysis and Applications
- Magnetic Properties of Alloys
- Metallic Glasses and Amorphous Alloys
- Adhesion, Friction, and Surface Interactions
- Magnetic Properties and Applications
- Quantum Dots Synthesis And Properties
- Liver Diseases and Immunity
Tokyo Institute of Technology
2009-2025
Life Science Institute
2019-2024
Institute of Science Tokyo
2024
Nagasaki Medical Center
2021
The University of Tokyo
1993-2020
Graduate School USA
2019
Kumamoto University
1992-2016
Shinshu University
1988
The switching of the protonation sites in hydrated nicotine, probed by experimental infrared (IR) spectroscopy and theoretical ab initio calculations, is facilitated via a Grotthuss instead bimolecular proton transfer (vehicle) mechanism at temperature (T = 130 K) as unambiguously confirmed experiments with deuterated water. In contrast, vehicle preferred higher temperatures 300 determined theory. for concerted results production nicotine's bioactive addictive pyrrolidine-protonated...
Gas-phase photoelectron spectroscopy (PES) was conducted on [XAg24 (SPhMe2 )18 ]- (X=Ag, Au) and [YAg24 ]2- (Y=Pd, Pt), which have a formal superatomic core (X@Ag12 )5+ or (Y@Ag12 )4+ with icosahedral symmetry. PES results show that orbitals in the (Au@Ag12 remain unshifted respect to those (Ag@Ag12 core, whereas (Y = Pd, Pt) shift up energy by about 1.4 eV. The remarkable doping effect of single Y atom electronic structure chemically modified superatom reproduced theoretical calculations...
Atomically precise Au and Ag clusters protected by organic ligands can be viewed as chemically modified Au/Ag superatoms have attracted interest promising building units of functional materials ideal platforms for studying the size-dependent evolution structures properties. Their structures, stability, physicochemical properties been characterized in solution solid (or crystalline) phases various methods conventionally used science. However, novel complementary information on their intrinsic...
Valinomycin is a macrocyclic ionophore that transports K+ across hydrophobic membranes. Its function depends on selectivity, capture, transport, and release of the ion. While thermodynamics clearly indicate valinomycin binds preferentially over all other alkali ions, characterizing capture/transport/release by at molecular level remains challenge. The bracelet-like structure valinomycin-K+ (K+VM) has ion completely enveloped, facilitating transport through cell membrane. We report hydration...
To elucidate the principal interaction of nicotine (NIC) with binding pocket nicotinic acetylcholine receptor (nAChR), a simplified model complex comprising N'-methyl-indolyl-2-propanamide (MIPA) and NIC was studied using infrared spectroscopy theoretical calculations. MIPA serves as surrogate for tryptophan 156 residue α-subunit nAChR, which previously identified to stabilize in pocket. The MIPA-NIC stabilizes bioactive N-methylpyrrolidinium protomer (Pyrro-H+, 60% population) that...
This study provides a comprehensive investigation of the structural and vibrational properties protonated cytosine monomers dimers. Experimental IRPD spectroscopy, combined with theoretical calculations, revealed distinct behaviors for monomers...
The adiabatic electron affinity of [Au<sub>25</sub>(SC<sub>12</sub>H<sub>25</sub>)<sub>18</sub>]<sup>0</sup> was experimentally determined to be 2.2 eV by anion photoelectron spectroscopy.
The human MutT homolog 1 (hMTH1, NUDT1) hydrolyzes oxidatively damaged nucleoside triphosphates and is the main enzyme responsible for nucleotide sanitization. hMTH1 recently has received attention as an anticancer target because blockade leads to accumulation of oxidized nucleotides in cell, resulting mutations death cancer cells. Unlike Escherichia coli MutT, which shows high substrate specificity 8-oxoguanine nucleotides, broad including 8-oxo-dGTP 2-oxo-dATP. However, reason this remains...
Cryogenic double ion trap IR spectroscopy combined with isotopic labelling reveals that the solvent-mediated intracluster proton transfer mechanism in microhydrated protonated p -aminobenzoic acid changes from vehicle to Grotthuss between n = 5 and 7.
We herein investigated collision-induced dissociation (CID) processes of undecagold clusters protected by mixed ligands [Au11(PPh3)8X2]+ (X = Cl, C≡CPh) using mass spectrometry and density functional theory calculations. The results showed that the CID produced fragment ions [Au x (PPh3) y X z ]+ with a formal electron count eight via sequential loss PPh3 AuX(PPh3) units in competitive manner, indicating channels are governed electronic stability fragments. Interestingly, branching fraction...
Collision cross sections (CCSs) of ligand-protected metal clusters were evaluated using ion mobility mass spectrometry. The targets used in this study phosphine-protected [PdAu8(PPh3)8]2+ and [Au9(PPh3)8]3+, for which the total structures have been resolved by single-crystal X-ray analysis. arrival time distributions as a function He flow rate cell located just front traveling wave filled with N2 buffer gas demonstrated that it got converted to another structural isomer having smaller CCS,...
Photoelectron (PE) spectra of thiolate-protected coinage metal clusters [Au25(SC2H4Ph)18]− and [Ag25(SPhMe2)18]− isolated in vacuum were recorded at 355 266 nm. Their adiabatic electron affinities determined to be 2.36 ± 0.01 2.02 0.02 eV, respectively, from the onsets PE Upon irradiation with a nm light, emission slow electrons was observed as major process, while suppressing direct detachment dissociation into anionic fragments. Curve fitting analysis suggests that is assigned thermionic...
We report a joint experimental–theoretical study of the never reported before structure and infrared spectra gas phase monohydrated nicotine (NIC) nornicotine (NOR) use them to assign their protonation sites. NIC's biological activity is strongly affected by its site, namely, pyrrolidine (Pyrro-NICH+, anticipated active form) pyridine (Pyri-NICH+) forms; however, these have yet be directly experimentally determined in either nicotinic acetylcholine receptor (nAChR, no water present) or...
The protonation site of molecules can be varied by their surrounding environment. Gas-phase studies, including the popular techniques infrared spectroscopy and ion mobility spectrometry, are a powerful tool for determination sites in solvated clusters but often suffer from inherent limits larger hydrated clusters. Here, we present collision-assisted stripping (CAS-IR) as new technique to overcome these problems apply it proof-of-principle experiment protonated benzocaine (H+BC), which shows...
We synthesised heteroleptic azadipyrrinato-dipyrrinato hybrid zinc(II) complex 1-Zn-2, by means of the stepwise coordination method. Homoleptic bis(azadipyrrinato)zinc(II) 1-Zn-1 was non-fluorescent, whereas 1-Zn-2 exhibited detectable fluorescence from azadipyrrinato ligand 1.
The electron binding mechanism in [Ag44(SC6H3F2)30]4- (SC6H3F2 = 3,4-difluorobenzenethiolate) tetra-anion was studied by photoelectron spectroscopy (PES), collision-induced dissociation mass spectrometry (CID-MS), and density functional theory (DFT) computations. PES showed that is energetically metastable with respect to autodetachment {[Ag44(SC6H3F2)30]3- + e-} features a repulsive Coulomb barrier (RCB) height of 2.7 eV. However, CID-MS revealed does not release an upon collisional...
The electron binding energies of the ligand-protected gold/silver-based cluster anions, [Au25(SR)18]-, [XAg24(SR')18]2- (X = Ag+, Au+, Pd0, or Pt0), and [PdAu24(C≡CR″)18]2- having icosahedral M13 superatomic cores, were reexamined by gas-phase photoelectron spectroscopy (PES) on a significantly intensified mass-selected ion beam. Laser fluence-dependent PE spectra pump-probe PES revealed that previous contaminated signals due to two-photon detachment via long-lived photoexcited states....
The origin of high uniaxial magnetic asnisotropy in FeCoB thin films was investigated by focusing on the changes FeCo crystal distortion and alignment. were prepared facing targets sputtering using F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">88.8</sub> Co xmlns:xlink="http://www.w3.org/1999/xlink">27.2</sub> B xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> alloy examined with X-ray diffraction (XRD) analysis. Preparation a Ru...
Abstract The infrared (IR) spectra of alkali and alkaline earth metal ion complexes with the Ac‐Tyr‐NHMe (GYG) peptide have been measured by laser photodissociation in a cold trap coupled an electrospray mass spectrometer. GYG corresponds to portion selectivity filter KcsA K + channel that allows pass, but blocks Na even though it has smaller ionic radius than . This current study extends previous investigation on entire set metaI ions dications. IR‐IR hole‐burning (IR 2 dip) spectroscopy...
Cryogenic ion trap infrared spectroscopy reveals that different binding motifs between the two enantiomers of protonated tyrosine and permethylated β-cyclodextrin result in chiral discrimination.
Potassium ion channels selectively permeate K+, as well Rb+ and Cs+ to some degree, while excluding Na+ Li+. Conformations of alkali metal complexes Ac-Tyr-NHMe, a model peptide the selectivity filter in K+ channel, were previously found correlate with permeability ions channel by cold trap infrared spectroscopy. With an additional temperature-controlled trap, we examined conformations complexes, allowing collide He buffer gas at different temperatures, prior spectroscopic investigation. The...
Para-Aminobenzoic acid (PABA) is a benchmark molecule to study solvent-induced proton site switching. Protonation of the carboxy and amino groups PABA generates O- N-protomers PABAH+, respectively. Ion mobility mass spectrometry (IMS) infrared photodissociation (IRPD) studies have claimed that O-protomer most stable in gas phase converted N-protomer solution upon hydration with six water molecules gas-phase cluster. However, threshold size has remained ambiguous because arrival time...
The binding affinity of nicotinoids to the residues α4β2 variant nicotinic acetylcholine receptor (nAChR) was identified as a strong predictor nicotinoid's addictive character. Using ab initio calculations for model pockets increasing size composed 3, 6, and 14 amino acids (3AA, 6AA, 14AA) that are derived from crystal structure, differences in 6 nicotinoids, namely, nicotine (NIC), nornicotine (NOR), anabasine (ANB), anatabine (ANT), myosmine (MYO), cotinine (COT) were correlated their...
The infrared (IR) spectra of gas phase protonated nicotine has been measured in the never-before probed N-H "fingerprint region" (3200-3500 cm-1). molecules generated by an electrospray source are thermalized first ion trap with water vapor and He at a pre-determined temperature prior to being IR spectroscopy second 4 K. exhibit two stretching bands which assigned pyridine pyrrolidine protomers aid high-level electronic structure calculations. This finding is sharp contrast previous...