Highly-sensitive analysis of fluorescence XANES at Europium (Eu) L-edge for the determination of oxidation state for trace amount of Eu in natural samples by bragg-type crystal analyzer system

Konagaya, Rimi*; Kawamura, Naomi*; Yamaguchi, Akiko; Takahashi, Yoshio*

Chemistry Letters, 50(8), p.1570 - 1572, 2021/08

https://doi.org/10.1246/cl.210249

no abstracts in English

Freezable and unfreezable hydration water; Distinct contributions to protein dynamics revealed by neutron scattering

Yamamoto, Naoki*; Kofu, Maiko; Nakajima, Kenji; Nakagawa, Hiroshi; Shibayama, Naoya*

Journal of Physical Chemistry Letters (Internet), 12(8), p.2172 - 2176, 2021/03

https://doi.org/10.1021/acs.jpclett.0c03786

Hydration water plays a crucial role for activating the protein dynamics required for functional expression. Yet, the details are not understood about how hydration water couples with protein dynamics. A temperature hysteresis of the ice formation of hydration water is a key phenomenon to understand which type of hydration water, unfreezable or freezable hydration water, is crucial for the activation of protein dynamics. Using neutron scattering, we observed a temperature-hysteresis phenomenon in the diffraction peaks of the ice of freezable hydration water, whereas protein dynamics did not show any temperature hysteresis. These results show that the protein dynamics is not coupled with freezable hydration water dynamics, and unfreezable hydration water is essential for the activation of protein dynamics.

Gas barrier properties of chemical vapor-deposited graphene to oxygen imparted with sub-electronvolt kinetic energy

Ogawa, Shuichi*; Yamaguchi, Hisato*; Holby, E. F.*; Yamada, Takatoshi*; Yoshigoe, Akitaka; Takakuwa, Yuji*

Journal of Physical Chemistry Letters (Internet), 11(21), p.9159 - 9164, 2020/11

https://doi.org/10.1021/acs.jpclett.0c02112

Atomically thin layers of graphene have been proposed to protect surfaces through the direct blocking of corrosion reactants such as oxygen with low added weight. The long term efficacy of such an approach, however, is unclear due to the long-term desired protection of decades and the presence of defects in as-synthesized materials. Here, we demonstrate catalytic permeation of oxygen molecules through previously-described impermeable graphene by imparting sub-eV kinetic energy to molecules. These molecules represent a small fraction of a thermal distribution thus this exposure serves as an accelerated stress test for understanding decades-long exposures. The permeation rate of the energized molecules increased 2 orders of magnitude compared to their non-energized counterpart. Graphene maintained its relative impermeability to non-energized oxygen molecules even after the permeation of energized molecules indicating that the process is non-destructive and a fundamental property of the exposed material.

Local structure of rare earth elements (REE) in marine ferromanganese oxides by extended X-ray absorption fine structure and its comparison with REE in ion-adsorption type deposits

Nagasawa, Makoto*; Qin, H.-B.*; Yamaguchi, Akiko; Takahashi, Yoshio*

Chemistry Letters, 49(8), p.909 - 911, 2020/08

https://doi.org/10.1246/cl.200257

Bromine-isotope selective ionization using field-free alignment of IBr isotopologues with a switched nanosecond laser pulse

Akagi, Hiroshi*; Kumada, Takayuki; Otobe, Tomohito*; Itakura, Ryuji*; Hasegawa, Hirokazu*; Oshima, Yasuhiro*

Chemistry Letters, 49(4), p.416 - 418, 2020/04

https://doi.org/10.1246/cl.200024

Finding free-energy landmarks of chemical reactions

Shiga, Motoyuki; Tuckerman, M. E.*

Journal of Physical Chemistry Letters (Internet), 9(21), p.6207 - 6214, 2018/11

https://doi.org/10.1021/acs.jpclett.8b01958

Predicting reaction pathways is one of the most important goals in theoretical and computational chemistry. In this paper, we propose a novel approach to search for free-energy landmarks, i.e., minima and the saddle points, of chemical reactions in an automated manner using a combination of steepest descent and gentlest ascent methods. As demonstrations, we present applications to the ring-opening reaction of benzocyclobutene and an SN2 reaction in aqueous solution.

Sorption behavior of Np(V) on microbe pure culture and consortia

Onuki, Toshihiko; Kozai, Naofumi; Sakamoto, Fuminori; Utsunomiya, Satoshi*; Kato, Kenji*

Chemistry Letters, 46(5), p.771 - 774, 2017/05

https://doi.org/10.1246/cl.170068

The sorption behavior of Np(V) by the microbe consortia and by a single pure culture of Fe reducing bacterium was studied at pH between 3 and 7 in resting cell conditions. The sorption of Np(V) by the Fe reducing bacterium obtained in the inert condition and by the consortia in aerated condition were higher than by the Fe reducing bacterium in aerobic condition at pH below 5, strongly suggesting presence of other mechanism than the adsorption on microbial cell surface, i.e. reduction to Np(IV).

Complexing agents for oxonium anions of Mo and Re and their masking effects on extraction using N-donor extractants

Sasaki, Yuji; Suzuki, Tomoya; Morita, Keisuke; Tsubata, Yasuhiro

Chemistry Letters, 43(10), p.1538 - 1539, 2014/10

https://doi.org/10.1246/cl.140502

Several complexing agents including soft donor in their structures are examined for the masking effects of Mo and Re through solvent extraction. The available extractants are hexaoctyl-nitrilotriacetamide (NTAamide) and methyliminodioctylacetamide (MIDOA), whose extractants have high D(Mo, Re). It is clear that Mo and Re in HNO dissolving N-donor ligands, ethylenediamine, diethylenetriamine, and 1,3-diaminopropane, can be suppressed for extraction into organic phase. The ligands including sulfur donor, e.g., thiourea, are also tested, however, less masking effect can be seen.

Adsorption behavior of lanthanide ions on nonbiological phospholipid membranes; A Model study using liposome

Yamasaki, Shinya; Shirai, Osamu*; Kano, Kenji*; Kozai, Naofumi; Sakamoto, Fuminori; Onuki, Toshihiko

Chemistry Letters, 42(8), p.819 - 821, 2013/08

https://doi.org/10.1246/cl.130226

The adsorption behavior of lanthanide ions (except for Pm) on liposomes composed of phosphatidylcholine and cholesterol was examined to understand the interaction between lanthanide ions and the phosphoryl moiety of phospholipids. The adsorption of lanthanide ions increased with an increase in pH under the weakly acidic conditions. Selective adsorption with the local maximum at the Er ion and local minimum at the Er ion was observed, similar to the selective adsorption of the bacterial cell surface but different from that of orthophosphates. These results indicate that the adsorption of lanthanide on the phospholipid does not result from simple adsorption on orthophosphate functional groups but by the composition and molecular structure of the phospholipid. Our results strongly suggest that liposomes can be used as a simple biomembrane model without any biological activity for the study of adsorption of lanthanide ions.

Novel soft-hard donor ligand, NTAamide, for mutual separation of trivalent actinides and lanthanides

Sasaki, Yuji; Tsubata, Yasuhiro; Kitatsuji, Yoshihiro; Morita, Yasuji

Chemistry Letters, 42(1), p.91 - 92, 2013/01

https://doi.org/10.1246/cl.2013.91

The new N-donor extractant, NTAamide, is synthesized and tested for extraction and separation of Am-Cm-Ln. It was found that the high separation factors for An-Ln can be seen at 0.1-0.2M HNO, which suggest the de-protonation to N donor is important to show the high SF between An and Ln. From the present work, the stable N-donor extractant having high SF of An-Ln from nitric acid to n-dodecane can be obtained. The highest separation factor, 6.5, of Am-Cm for the condition of 0.5M NTAamide (C8) in n-dodecane and 10 mM TEDGA in 0.2M HNO as one of the highest SF values is found. NTAamide is the promising extractants for partitioning process of Am-Cm-Ln.