Structure and function of a silicic acid channel Lsi1

Silicon is a beneficial element for plant growth and production, especially in rice. Plant roots take up silicon in the form of silicic acid. Silicic acid channels, which belong to the NIP subfamily of aquaporins, are responsible for silicic acid uptake. Accumulated experimental results have deepened our understanding of the silicic acid channel for its uptake mechanism, physiological function, localization, and other aspects. However, how the silicic acid channel efficiently and selectively permeates silicic acid remains to be elucidated. Recently reported crystal structures of the silicic acid channel enabled us to discuss the mechanism of silicic acid uptake by plant roots at an atomic level. In this mini-review, we focus on the crystal structures of the silicic acid channel and provide a detailed description of the structural determinants of silicic acid permeation and its transport mechanism, which are crucial for the rational creation of secure and sustainable crops

Structural basis for high selectivity of a rice silicon channel Lsi1

Silicon (Si), the most abundant mineral element in the earth’s crust, is taken up by plant roots in the form of silicic acid through Low silicon rice 1 (Lsi1). Lsi1 belongs to the Nodulin 26-like intrinsic protein subfamily in aquaporin and shows high selectivity for silicic acid. To uncover the structural basis for this high selectivity, here we show the crystal structure of the rice Lsi1 at a resolution of 1.8 Å. The structure reveals transmembrane helical orientations different from other aquaporins, characterized by a unique, widely opened, and hydrophilic selectivity filter (SF) composed of five residues. Our structural, functional, and theoretical investigations provide a solid structural basis for the Si uptake mechanism in plants, which will contribute to secure and sustainable rice production by manipulating Lsi1 selectivity for different metalloids

OMAE2011-49594 DEVELOPMENT OF 6% NICKEL STEEL FOR LNG STORAGE TANKS

ABSTRACT 9% Ni steel has been used for LNG storage tanks for more than four decades although 5.5% Ni steel (N-TUF CR196) was developed in the 1970's using a special heat treatment method named L-treatment. The reason why the actual application of 5.5% Ni steel has not been attained to LNG storage tanks is mainly because the requirement of fracture properties is not confirmed for the tanks. Under the circumstances of expanding demand for natural gas and double-integrity in LNG storage tanks, we restarted developing low Ni steel for LNG storage tanks by using both conventional and advanced techniques. For the application of low Ni steel to the present LNG storage tanks, both fracture initiation and propagation properties of base metal plates and welded joints should be concerned. The fracture initiation and propagation properties of base metal were compensated with the intercritical reheating process (L-treatment), and the propagation property was additionally enhanced by combining TMCP with L-treatment. In addition, the chemical composition adjustment and the homogenization treatment of solute elements were conducted for improving the fracture initiation and propagation properties of welded joints. 6% Ni steel plates were manufactured by the process of continuous casting, reheating, hot rolling, direct quenching (TMCP), L-treatment, and tempering, and their chemical composition was 0.05C-0.06Si-1.0Mn-6.3Ni-Cr-Mo. As the results of fracture property evaluation including large-scale fracture tests such as the duplex ESSO test and the wide plate tensile test, it was demonstrated that 6% Ni steel has good characteristics regarding brittle fracture initiation and propagation in base metal plates and welded joints

Orchestrated ensemble activities constitute a hippocampal memory engram

The brain stores and recalls memories through a set of neurons, termed engram cells. However, it is unclear how these cells are organized to constitute a corresponding memory trace. We established a unique imaging system that combines Ca2+ imaging and engram identification to extract the characteristics of engram activity by visualizing and discriminating between engram and non-engram cells. Here, we show that engram cells detected in the hippocampus display higher repetitive activity than non-engram cells during novel context learning. The total activity pattern of the engram cells during learning is stable across post-learning memory processing. Within a single engram population, we detected several sub-ensembles composed of neurons collectively activated during learning. Some sub-ensembles preferentially reappear during post-learning sleep, and these replayed sub-ensembles are more likely to be reactivated during retrieval. These results indicate that sub-ensembles represent distinct pieces of information, which are then orchestrated to constitute an entire memory

Oxygen-evolving photosystem II structures during S1–S2–S3 transitions

Photosystem II (PSII) catalyses the oxidation of water through a four-step cycle of Si states (i = 0–4) at the Mn4CaO5 cluster1,2,3, during which an extra oxygen (O6) is incorporated at the S3 state to form a possible dioxygen4,5,6,7. Structural changes of the metal cluster and its environment during the S-state transitions have been studied on the microsecond timescale. Here we use pump-probe serial femtosecond crystallography to reveal the structural dynamics of PSII from nanoseconds to milliseconds after illumination with one flash (1F) or two flashes (2F). YZ, a tyrosine residue that connects the reaction centre P680 and the Mn4CaO5 cluster, showed structural changes on a nanosecond timescale, as did its surrounding amino acid residues and water molecules, reflecting the fast transfer of electrons and protons after flash illumination. Notably, one water molecule emerged in the vicinity of Glu189 of the D1 subunit of PSII (D1-E189), and was bound to the Ca2+ ion on a sub-microsecond timescale after 2F illumination. This water molecule disappeared later with the concomitant increase of O6, suggesting that it is the origin of O6. We also observed concerted movements of water molecules in the O1, O4 and Cl-1 channels and their surrounding amino acid residues to complete the sequence of electron transfer, proton release and substrate water delivery. These results provide crucial insights into the structural dynamics of PSII during S-state transitions as well as O–O bond formation

複数の埋伏過剰歯を伴った石灰化嚢胞性歯原性腫瘍の1例

石灰化嚢胞性歯原性腫瘍(以下CCOT)は病理組織学的に,裏装上皮内にghost cellの出現とそれらの石灰化を特徴とし,また,歯牙腫をはじめとする歯原性腫瘍を合併することがある.さらに,CCOT症例の半数前後は埋伏歯を伴うことが知られているが,複数の埋伏過剰歯を伴うことは稀である。今回われわれは,歯牙腫と8本の埋伏過剰歯を伴ったCCOTの1例を経験したので,その概要を報告する.症例は40歳代の男性で,近歯科医院を受診した際にX線検査にて右側上顎洞部に嚢胞様透過像が認められ,精査・加療目的に当科紹介となった.初診時,上顎右側側切歯から右側第一大臼歯部の頬側歯肉に弾性軟の腫脹を認め,波動が触知された.CTにて,右側上顎洞および鼻腔の下部に境界明瞭で単胞性の嚢胞様病変を認め,病変内部に大小の石灰化像および歯牙様石灰化像を認めた.全身麻酔下にて摘出術および対孔形成術を施行した.摘出組織ではCCOTとともに歯牙腫ならびに8本の埋伏歯を認めた.病理組織学的に上皮層内にghost cellとその石灰化がみられた.文献的に本症例のように複数の埋伏過剰歯を伴ったCCOTはきわめてまれであった.It is well known that an associated impacted tooth is seen in about half of cases with calcifying cystic odontogenic tumor (CCOT), but CCOT with two or more impacted teeth is extremely rare. This paper reports a case of CCOT with 8 impacted, supernumerary teeth. The patient is an adult male with swelling of right maxilla. X-ray examination showed a cystic lesion with calcification and with numerous impacted, supernumerary teeth. A clinical diagnosis of CCOT with odontoma was made. And surgical excised of the lesion was performed. Macroscopically, surgically excised specimen showed eight supernumerary teeth with formal and/or unformal shape were involved in the lesion, but these teeth were not enclosed by fibrous capsule. The lesion was diagnosed finally as CCOT with odontoma and with eight impacted, supernumerary teeth by pathological examination. The review of the literature yielded CCOT with more than 3 associated supernumerary has not been documental

Electroresistance Effect in Gold Thin Film Induced by Ionic-Liquid-Gated Electric Double Layer

Electroresistance effect was detected in a metallic thin film using ionic-liquid-gated electric-double-layer transistors (EDLTs). We observed reversible modulation of the electric resistance of a Au thin film. In this system, we found that an electric double layer works as a nanogap capacitor with 27 (-25) MVcm(-1) of electric field by applying only 1.7V of positive (negative) gate voltage. The experimental results indicate that the ionic-liquid-gated EDLT technique can be used for controlling the surface electronic states on metallic systems. (C) 2012 The Japan Society of Applied Physic