Development of Computer Control System for Neutron Spin Echo Spectrometer

We have developed a computer control system for a neutron spin echo spectrometer (NSE) which has been constructed at C_ cold neutron guide port of JRR-3M, JAERI. This system controls the current of coils, the measurements by counters and the pulse-motor-drivers using a personal computer. The current of the coils is controlled using GP-IB or the D/A converters equipped in the I/O box connected to the personal computer. The current can be inverted using a current invertor controlled by the computer. The computer gets the data from a He^3 detector or one dimensional position sensitive detector (1DPSD) and saves them into hard- or floppy- disks, prints out them or transfers to another computer connected through RS-232C which analyzes the data. The computer programs for this system called NSEC are made of an assembly of the several simple programs (command) which can be rearranged easily. An NSE mesurement can be carried out automatically using the Batch files composed of the commands. This system is very convenient for NSE measurements

Tuning Membrane Thickness Fluctuations in Model Lipid Bilayers

AbstractMembrane thickness fluctuations have been associated with a variety of critical membrane phenomena, such as cellular exchange, pore formation, and protein binding, which are intimately related to cell functionality and effective pharmaceuticals. Therefore, understanding how these fluctuations are controlled can remarkably impact medical applications involving selective macromolecule binding and efficient cellular drug intake. Interestingly, previous reports on single-component bilayers show almost identical thickness fluctuation patterns for all investigated lipid tail-lengths, with similar temperature-independent membrane thickness fluctuation amplitude in the fluid phase and a rapid suppression of fluctuations upon transition to the gel phase. Presumably, in vivo functions require a tunability of these parameters, suggesting that more complex model systems are necessary. In this study, we explore lipid tail-length mismatch as a regulator for membrane fluctuations. Unilamellar vesicles of an equimolar mixture of dimyristoylphosphatidylcholine and distearoylphosphatidylcholine molecules, with different tail-lengths and melting transition temperatures, are used as a model system for this next level of complexity. Indeed, this binary system exhibits a significant response of membrane dynamics to thermal variations. The system also suggests a decoupling of the amplitude and the relaxation time of the membrane thickness fluctuations, implying a potential for independent control of these two key parameters

Investigating the Effect of Medium Chain Triglycerides on the Elasticity of Pulmonary Surfactant

In recent years, vaping has increased in both popularity and ease of access. This has led to an outbreak of a relatively new condition known as e-cigarette/vaping-associated lung injury (EVALI). This injury can be caused by physical interactions between the pulmonary surfactant (PS) in the lungs and toxins typically found in vaping solutions, such as medium chain triglycerides (MCT). MCT has been largely used as a carrier agent within many cannabis products commercially available on the market. Pulmonary surfactant ensures proper respiration by maintaining low surface tensions and interface stability throughout each respiratory cycle. Therefore, any impediments to this system that negatively affect the efficacy of this function will have a strong hindrance on the individual’s quality of life. Herein, neutron spin echo (NSE) and Langmuir trough rheology were used to probe the effects of MCT on the mechanical properties of pulmonary surfactant. Alongside a porcine surfactant extract, two lipid-only mimics of progressing complexity were used to study MCT effects in a range of systems that are representative of endogenous surfactant. MCT was shown to have a greater biophysical effect on bilayer systems compared to monolayers, which may align with biological data to propose a mechanism of surfactant inhibition by MCT oil

Transverse lipid organization dictates bending fluctuations in model plasma membranes

© 2020 The Royal Society of Chemistry. Membrane undulations play a vital role in many biological processes, including the regulation of membrane protein activity. The asymmetric lipid composition of most biological membranes complicates theoretical description of these bending fluctuations, yet experimental data that would inform any such a theory is scarce. Here, we used neutron spin-echo (NSE) spectroscopy to measure the bending fluctuations of large unilamellar vesicles (LUV) having an asymmetric transbilayer distribution of high- and low-melting lipids. The asymmetric vesicles were prepared using cyclodextrin-mediated lipid exchange, and were composed of an outer leaflet enriched in egg sphingomyelin (ESM) and an inner leaflet enriched in 1-palmitoyl-2-oleoyl-phosphoethanolamine (POPE), which have main transition temperatures of 37 °C and 25 °C, respectively. The overall membrane bending rigidity was measured at three temperatures: 15 °C, where both lipids are in a gel state; 45 °C, where both lipids are in a fluid state; and 30 °C, where there is gel-fluid co-existence. Remarkably, the dynamics for the fluid asymmetric LUVs (aLUVs) at 30 °C and 45 °C do not follow trends predicted by their symmetric counterparts. At 30 °C, compositional asymmetry suppressed the bending fluctuations, with the asymmetric bilayer exhibiting a larger bending modulus than that of symmetric bilayers corresponding to either the outer or inner leaflet. We conclude that the compositional asymmetry and leaflet coupling influence the internal dissipation within the bilayer and result in membrane properties that cannot be directly predicted from corresponding symmetric bilayers

Observation of Small Cluster Formation in Concentrated Monoclonal Antibody Solutions and Its Implications to Solution Viscosity

AbstractMonoclonal antibodies (mAbs) are a major class of biopharmaceuticals. It is hypothesized that some concentrated mAb solutions exhibit formation of a solution phase consisting of reversibly self-associated aggregates (or reversible clusters), which is speculated to be responsible for their distinct solution properties. Here, we report direct observation of reversible clusters in concentrated solutions of mAbs using neutron spin echo. Specifically, a stable mAb solution is studied across a transition from dispersed monomers in dilute solution to clustered states at more concentrated conditions, where clusters of a preferred size are observed. Once mAb clusters have formed, their size, in contrast to that observed in typical globular protein solutions, is observed to remain nearly constant over a wide range of concentrations. Our results not only conclusively establish a clear relationship between the undesirable high viscosity of some mAb solutions and the formation of reversible clusters with extended open structures, but also directly observe self-assembled mAb protein clusters of preferred small finite size similar to that in micelle formation that dominate the properties of concentrated mAb solutions

Japanese guidelines for atopic dermatitis 2020.

Atopic dermatitis (AD) is a disease characterized by relapsing eczema with pruritus as a primary lesion, which is frequently encountered in clinical practice. Skin barrier dysfunction leads to enhanced skin irritability to non-specific stimuli and epicutaneous sensitization. In the lesion site, a further inflammation-related reduction in skin barrier function, enhanced irritability and scratching-related stimuli deteriorate eczema, leading to vicious cycle of inflammation. The current strategies to treat AD in Japan from the perspective of evidence-based medicine consist of three primary measures: (i) the use of topical corticosteroids and tacrolimus ointment as the main treatment for the inflammation; (ii) topical application of emollients to treat the cutaneous barrier dysfunction; and (iii) avoidance of apparent exacerbating factors, psychological counseling and advice about daily life. The guidelines present recommendations to review clinical research articles, evaluate the balance between the advantages and disadvantages of medical activities, and optimize medical activity-related patient outcomes with respect to several important points requiring decision-making in clinical practice

62. Pressure-effects on the structure formation in microemulsion systems(poster presentation,Soft Matter as Structured Materials)

この論文は国立情報学研究所の電子図書館事業により電子化されました。非イオン性界面活性剤C_E_5、水、油からなる三元系マイクロエマルションの構造変化に及ぼす圧力効果を調べた。実験は、小角中性子散乱(SANS)及び中性子スピンエコー(NSE)により行い、静的構造変化と動的構造変化について測定した。圧力上昇に伴う、ラメラからヘキサゴナルへの構造変化が観測され、圧力印加による活性剤の体積変化によって自発曲率変化が誘発されるためであることがわかった。一方、温度下降でも同様の構造変化が観測されるが、温度変化による構造変化の起源は活性剤の体積変化による自発曲率変化では説明できない。また、NSEにより活性剤膜の弾性率を測定したところ、圧力上昇による膜の硬化現象が観測された。この現象は、イオン性界面活性剤膜の場合にも観測されており、マイクロエマルション系では加圧によって活性剤膜が硬化する、という描像が一般的であると考えられる

Long-range periodic structure induced by coupling of the solvation effect and concentration fluctuation in water and 3-methylpyridine with salts

この論文は国立情報学研究所の電子図書館事業により電子化されました。研究会報告塩の添加により、相分離が誘発されることが知られている水と3-メチルピリジン(3MP)の混合溶液系の臨界挙動について、小角中性子散乱(SANS)により測定を行なった。その結果、溶媒の臨界揺らぎと塩の溶媒和効果がカップルすることで、数百Aを特徴的長さとする周期構造が形成されることが示された

The bending rigidity of lipid bilayers in the anomalous swelling regime determined by neutron spin echo(Poster session 2, New Frontiers in Colloidal Physics : A Bridge between Micro- and Macroscopic Concepts in Soft Matter)

この論文は国立情報学研究所の電子図書館事業により電子化されました。人工リン脂質が水中で形成するラメラ構造は、リン脂質分子の膜内でのpackingの違いにより、温度上昇に応じてゲル相から液晶相に転移する。そしてDMPCやDPPCなどのリン脂質においては、ゲル相/液晶相の転移点直上において膜間距離が増大する「異常膨潤」の現象が見られることが知られていた。今回はその異常膨潤の要因を調べるため、中性子スピンエコー法を用いて二重膜の曲げ弾性係数の変化を調べた。その結果、膜間距離が広がるに従って膜が堅くなる事が分かった。これは、膜が柔らかくなることにより立体斥力が増大して膜間距離が広がる、と言うこれまで考えられていた描像に反する結果となっている。The origin of anomalous swelling in multilamellar vesicles of phospholipids upon approaching the main transition is still a matter of dispute. From the recent small-angle X-ray scattering experiment on DMPC, the decrease of the bending modulus of the lipid bilayers is confirmed to be the origin of the anomalous swelling ; this would increase undulations of lipid bilayers and would increase the steric repulsion between bilayers. However, nobody has any ideas to explain the microscopic origin of the decrease of bending modulus near the main transition so far

Effects of temperature and pressure on phase transitions in a ternary microemulsion system

Temperature variation experiments of small angle neutron scattering ͑SANS͒ and neutron spin echo ͑NSE͒ were carried out in order to compare effects of temperature and pressure on a structural formation in a ternary microemulsion system composed of AOT ͑Aerosol-OT; dioctyl sulfosuccinate sodium salt͒, D 2 O, and n-decane. From SANS measurements, a phase transition from one-phase dense water-in-oil droplet to two-phase coexistence with a lamellar and a disordered structure was observed with increasing temperature, similar to the case of pressure variation. Another phase transition was observed at a higher temperature above the lamellar phase, although such a subsequent phase transition has not been observed at higher pressure. The characteristic features of structural phase transitions by temperature and by pressure were compared by introducing a reduced temperature and pressure. The dynamical property observed from the NSE measurement was different between the high-temperature phase and the high-pressure phase. These results indicate that the mechanism of the phase transition induced by temperature is different from that by pressure