Nagasawa, Makoto*; Qin, H.-B.*; Yamaguchi, Akiko; Takahashi, Yoshio*
Chemistry Letters, 49(8), p.909 - 911, 2020/08
Oba, Yojiro; Motokawa, Ryuhei; Hino, Masahiro*; Adachi, Nozomu*; Todaka, Yoshikazu*; Inoue, Rintaro*; Sugiyama, Masaaki*
Chemistry Letters, 49(7), p.823 - 825, 2020/07
Akagi, Hiroshi*; Kumada, Takayuki; Otobe, Tomohito*; Itakura, Ryuji*; Hasegawa, Hirokazu*; Oshima, Yasuhiro*
Chemistry Letters, 49(4), p.416 - 418, 2020/04
Fujiwara, Satoru*; Matsuo, Tatsuhito*; Sugimoto, Yasunobu*; Shibata, Kaoru
Journal of Physical Chemistry Letters (Internet), 10(23), p.7505 - 7509, 2019/12
Characterization of the dynamics of disordered polypeptide chains is required to elucidate the behavior of intrinsically disordered proteins and proteins under non-native states related to the folding process. Here we develop a method using quasielastic neutron scattering, combined with small-angle X-ray scattering and dynamic light scattering, to evaluate segmental motions of proteins as well as diffusion of the entire molecules and local side-chain motions. We apply this method to RNase A under the unfolded and molten-globule (MG) states. The diffusion coefficients arising from the segmental motions are evaluated and found to be different between the unfolded and MG states. The values obtained here are consistent with those obtained using the fluorescence-based techniques. These results demonstrate not only feasibility of this method but also usefulness to characterize the behavior of proteins under various disordered states.
Shiga, Motoyuki; Tuckerman, M. E.*
Journal of Physical Chemistry Letters (Internet), 9(21), p.6207 - 6214, 2018/11
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.
Shimizu, Takeshi*; Wang, H.*; Tanifuji, Naoki*; Matsumura, Daiju; Yoshimura, Masashi*; Nakanishi, Koji*; Ota, Toshiaki*; Yoshikawa, Hirofumi*
Chemistry Letters, 47(5), p.678 - 681, 2018/05
Onuki, Toshihiko; Kozai, Naofumi; Sakamoto, Fuminori; Utsunomiya, Satoshi*; Kato, Kenji*
Chemistry Letters, 46(5), p.771 - 774, 2017/05
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).
Suzuki, Tomoya; Morita, Keisuke; Sasaki, Yuji
Chemistry Letters, 44(2), p.152 - 153, 2015/02
To recover Rh(III) from HNO solution, adsorption experiments have been performed using an ion-exchange resin bearing an -trimethylglycine group (AMP03). AMP03 was found to exhibit relatively high adsorption ability for Rh(III) for [HNO] 0.02 M ([HNO] denotes HNO concentration in the supernatant), and the values increase significantly with the addition of triethylamine or tris(2-aminoethyl)amine to 0.12 M HNO solutions. In contrast, the addition of thiourea leads to a decrease in the values; i.e., a masking effect on Rh(III) was observed. These results show that AMP03 has a significant potential for effectively recovering Rh from HNO solution.
Sasaki, Yuji; Suzuki, Tomoya; Morita, Keisuke; Tsubata, Yasuhiro
Chemistry Letters, 43(10), p.1538 - 1539, 2014/10
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.
Sasaki, kotoe*; Suzuki, Tomoya*; Arai, Tsuyoshi*; Takao, Koichiro*; Suzuki, Shinichi; Yaita, Tsuyoshi; Ikeda, Yasuhisa*
Chemistry Letters, 43(5), p.670 - 672, 2014/05
no abstracts in English
Yamasaki, Shinya; Shirai, Osamu*; Kano, Kenji*; Kozai, Naofumi; Sakamoto, Fuminori; Onuki, Toshihiko
Chemistry Letters, 42(8), p.819 - 821, 2013/08
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.
Suzuki, Yoshinori*; Nankawa, Takuya; Onuki, Toshihiko
Chemistry Letters, 42(8), p.888 - 890, 2013/08
no abstracts in English
Sasaki, Yuji; Tsubata, Yasuhiro; Kitatsuji, Yoshihiro; Morita, Yasuji
Chemistry Letters, 42(1), p.91 - 92, 2013/01
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.
Avramov, P.; Fedorov, D. G.*; Sorokin, P. B.*; Sakai, Seiji; Entani, Shiro; Otomo, Manabu; Matsumoto, Yoshihiro; Naramoto, Hiroshi*
Journal of Physical Chemistry Letters (Internet), 3(15), p.2003 - 2008, 2012/08
Suzuki, Daisuke; Kokubu, Yoko; Lee, C. G.; Esaka, Fumitaka; Magara, Masaaki; Kimura, Takaumi
Chemistry Letters, 41(1), p.90 - 91, 2012/01
In conventional isotope ratio analysis of individual plutonium particles, the analytical procedure is complicated, because the particles have to be dissolved prior to the measurement. The chemical treatments may cause contamination of U existing in the environment. This makes it difficult to obtain accurate Pu/Pu isotope ratio. In the present work, an analytical method by a combination of single particle transfer and thermal ionization mass spectrometry with a continuous heating method is examined for individual plutonium particles, namely the particles are measured without any chemical treatments. In addition, the technique is applied to the analysis of individual uranium-plutonium mixed oxide (MOX) particles. The results of analysis of individual particles produced from standard solutions indicate that all isotope ratios are consistent with the certified values. There is no effect of isobaric interference on the results. In conclusion, the proposed analytical method is a useful tool for the isotope ratio analysis of plutonium and MOX particles without any chemical treatments.
Onuki, Toshihiko; Yoshida, Takahiro*
Chemistry Letters, 41(1), p.98 - 100, 2012/01
We have studied the interactions of REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er) - desferrioxamine B (DFO) complexes with cells and with -AlO, at pH 4 - 9. The higher percent adsorption of REEs was obtained at lower pHs on P. Fluorescens cells and at higher pHs on -AlO. Degree of negative anomaly of Ce compared to its neighboring REEs, La(III) and Pr(III) decreased with increasing pH. Thus, the pH dependence of Ce anomaly is predominantly dependent on the stability of Ce(IV)-DFO complex.
Tanaka, Kazuya*; Tani, Yukinori*; Onuki, Toshihiko
Chemistry Letters, 40(8), p.806 - 807, 2011/08
We made sorption experiments of actinides on Mn oxide in dilute NaCl solution. Sorption affinity of actinides on synthetic Mn oxide was Th(IV) U(VI) Np(V). The specific sorption behavior of actinides on biogenic Mn oxide was observed. Thorium sorbed on biogenic Mn oxide was desorbed into solution with increasing time. Neptunium was not sorbed on biogenic Mn oxide. The specific sorption behavior is possibly due to organic ligands released from microorganisms and surface property of biogenic Mn oxide.
Sasaki, Takayuki*; Yoshida, Hatsumi*; Kitatsuji, Yoshihiro; Takagi, Ikuji*; Moriyama, Hirotake*
Chemistry Letters, 40(8), p.870 - 871, 2011/08
Trivalent metal ion selective electrode (ISE) consisting of bis-(diphenylphosphoryl)-methane as an ionophore was developed for the determination of formation constants with organic ligands. The ISE prepared exhibited Nernstian response to the concentration of Eu in the test solutions. Even in the presence of carboxylic acids such as malonic acid in samples, the obtained potential values were found to be stable and reproducible during the measurement time. The present formation constants of Eu with carboxylates were in good agreement with the reported values.
Shimojo, Kojiro; Mitamura, Hisayoshi; Mouri, Tsuyoshi; Naganawa, Hirochika
Chemistry Letters, 40(5), p.435 - 437, 2011/05
A simple fabrication strategy of DNA-transcribed silica materials has been developed. An ionic liquid incorporating an alkoxysilane group is capable of binding with DNA and acts as nuclei for subsequent sol-gel reaction with tetramethoxysilane. Unique silica materials with worm-like, rod-shaped, toroidal, or linearly fibrous structures are created from the same DNA template through the morphological transition of DNA induced by the ionic liquid.
Sasaki, Yuji; Morita, Yasuji; Kitatsuji, Yoshihiro; Kimura, Takaumi
Chemistry Letters, 39(8), p.898 - 899, 2010/08
The separation of Am and Cm from Sm, Eu and Gd was examined by using the combination of new extractant, DOODA (tetraoctyl-3,6-dioxaoctanediamide) and the masking agent, TEDGA (tetraethyl-diglycolamide). These reagents show the neutral donor feature and work in the acidic condition. DOODA can extract light lanthanides with high values into the organic phase, on the other hand TEDGA shows strong complexing ability with middle and heavy lanthanides in the aqueous phase. Americium and Cm behave as light lanthanides in this extraction system, therefore Am and Cm show high separation from middle lanthanides. The separation factors for (Am)/(Sm), (Am)/(Eu), and (Am)/(Gd) are 14.4, 40, and 111, respectively, under the condition of 0.3M DOODA/dodecane and 10 mM TEDGA/ 5M HNO. The high separation of Am and Cm from these lanthanides, having high neutron cross section, is confirmed in HNO-dodecane system without any pH buffer and metal salts.