Peptide Nanomaterials Designed from Natural Supramolecular Systems

Natural supramolecular assemblies exhibit unique structural and functional properties that have been optimized over the course of evolution. Inspired by these natural systems, various bio-nanomaterials have been developed using peptides, proteins, and nucleic acids as components. Peptides are attractive building blocks because they enable the important domains of natural protein assemblies to be isolated and optimized while retaining the original structures and functions. Furthermore, the peptide subunits can be conjugated with exogenous molecules such as peptides, proteins, nucleic acids, and metal nanoparticles to generate advanced functions. In this personal account, we summarize recent progress in the construction of peptide-based nanomaterial designed from natural supramolecular systems, including (1) artificial viral capsids, (2) self-assembled nanofibers, and (3) protein-binding motifs. The peptides inspired by nature should provide new design principles for bio-nanomaterials

COMPARISON OF THE ACCELERATION PHASE OF SPRINTING BETWEEN COLLEGE SPRINTERS AND COLLEGE BASEBALL PLAYERS

The purpose of this study was to examine and compare the sprinting movement of college sprinters and college baseball players, the latter are assumed to be specialized in the acceleration phase. Twenty subjects, 10 sprinters and 10 baseball players, participated in this study. Lower limbs joint angle (hip, knee and ankle), step length, step frequency, contact time and position of the center of mass at the toe-on and the toe-off were calculated. The results indicated that the center of mass of baseball players was located behind that of sprinters at the 3rd step toe on (p 0.008). In addition, the knee joint was significantly extended at the toe-on in the baseball players at the first and the second steps .These observations indicate that baseball players tend to contact with their foot more forward, and with their knees extended, compared to sprinters

Construction of Artificial Viral Capsids Encapsulating Short DNAs via Disulfide Bonds and Controlled Release of DNAs by Reduction

To construct an artificial viral capsid encapsulated short single-stranded DNA, a β-annulus peptide conjugated with ssDNA through a disulfide bond at the N-terminus (DNA-SS-β-Annulus) was synthesized. The DNA-SS-β-Annulus conjugate self-assembled into spherical structures ranging in the size of 36–60 nm. ssDNA was released from the capsids via the reduction of disulfide bonds

Condensation of Nonazeotropic Refrigerant Mixture R114/R113 in Horizontal Annuli with an Enhanced Inner Tube : Experimental Results

Local heat transfer and pressure drop measurements were made during condensation of a nonazeotropic refrigerant mixture R114/R113 in the annuli of horizontal double-tube condensers. The inner tube was a 19.1mm o.d. corrugated copper tube with soldered wire fins on the outer surface. The outer tubes were smooth tubes with inside diameter D_i of 29.9 and 25.0mm. The pressure drop and the heat transfer coefficient based on the bulk vapor-to-wall temperature difference were considerably smaller for R114/R113 than for R113. The vapor phase mass transfer coefficient β_n was higher for larger test fluid mass velocity G and D_i. At constant values of G and D_i, β_n was higher for larger condensation mass flux. The radial distribution of the vapor temperature was affected by the vapor velocity, becoming flatter at the outer part of the annulus and steeper near the liquid-vapor interface as the vapor velocity increased.蒸気圧縮式ヒートポンプ、冷凍機などの成績係数を向上させるための一方策としてローレンツサイクルが提案され、このサイクルに近づけることのできる非共沸2成分混合冷媒が実用されつつある。しかし、この冷媒が凝縮する際には低沸点蒸気が不凝縮ガスと類似の挙動を示すため、凝縮伝熱性能が単成分蒸気に比べて低下する。したがって、この冷媒を用いる凝縮器の性能向上を図るためには、凝縮液膜の熱抵抗と混合気の拡散抵抗の両者を減少させる必要がある。著者らは前提で純冷媒用の伝熱促進管の一種であるワイヤフィン付きコルゲート管を内管とする水平二重管環状部における非共沸混合冷媒R114/R113の凝縮実験を行い、圧力降下の摩擦成分は純冷媒に対する実験式で整理できること、凝縮側の熱抵抗にしめる気相の熱抵抗の割合は冷媒流量の増大につれて減少することを示した。そして、混合気相の物質伝達係数を円管上の強制対流凝縮理論から導かれた無次元パラメータを用いて整理した。しかし、より一般性のある整理式を得るためにはフィン形状、内外管径比などの影響を明らかにする必要がある。なお、フロン系非共沸2成分混合冷媒の管内、シェル側あるいは環状部における凝縮については最近多くの実験的研究が報告されているが、混合気相の物質伝達について検討したものは少なく、実験データの蓄積が望まれる。本報では、前報の内管とフィン配列が多少異なる管を内管とし、内径の異なる2種類の平滑管を外管とする水平二重管環状部におけるR114/R113の凝縮実験を行い、前報の結果と比較する。また、混合気相の温度分布測定結果についても述べる

Experimental Study of Condensation Heat Transfer from Downward-Facing Inclined Surfaces

Experiments were perfomed to study the effect of surface inclination on condensation heat transfer from downward-facing horizontal surfaces. A smooth surface and two low-finned surfaces with a length of 50mm were tested for condensation of R-113. The angle of inclination from the horizontal φ ranged from 0 to 90 deg. For the smooth surface, the heat tranfer coefficient α first decreased with the increasing of φ, then took a minimum near 5 deg, and then increased monotonically with further increasing φ. For the low-finned surfaces, α increased sharply with φ in the range of 0 to 30 deg, and then increased moderately with further increasing φ. The heat tranpfer coefficient for the better performing finned surface was 2.5, 9 and 12 times the smooth surface value for φ=0, 10 and 90 deg., respectively.電子素子の発熱密度の増大にともない、高性能の冷却法として浸漬冷却に対する関心が高まり、研究が盛んになっている。この冷却法では、発生蒸気を凝縮させるための凝縮器が必要となる。その形式として種々のものが検討されているが、容器の上面または側面を凝縮器として使用するものが最も簡便な方式であると考えられる。著者らはさきに下向き水平凝縮面下部に蒸気空間が存在する場合および凝縮面が液中に浸漬されている場合の熱伝達特性とその促進法について実験的に検討し、多孔質排液板を取付けたフィン付き面を使用することによって熱伝達が平滑面に比べて大幅に促進されることを見いだした。これは、フィン間溝部に充満した凝縮液が毛細管力によって効率良く多孔質排液板へ引き込まれ、フィン頂部が高性能の凝縮面として働くためである。同様の排液効果は伝熱面を傾斜させ、重力を利用することによっても期待できる。本報では平滑面と2種類のローフィン付き面をとりあげ、下向き面上の凝縮熱伝達に及ぼす伝熱面傾斜角の影響を冷媒R113を用いて実験的に検討する

Condensation of Nonazeotropic Refrigerant Mixture R114/R113 in Horizontal Annuli with an Enhanced Inner Tube : Correlation of Frictional Pressure Drop and Vapor Phase Mass Transfer

Frictional pressure gradient and vapor phase mass transfer correlations were developed for condensation of nonazeotropic refrigerant mixture R114/R113 in the annuli of horizontal double tubes with an enhanced inner tube. The frictional pressure gradient data were correlated fairly well by a previously developed empirical equation for condensation of pure refrigerants. The vapor phase mass transfer correlation was based on the previous results for turbulent flow in smooth and rough tubes with and without surface suction. For given conditions of vapor and tube wall, the heat transfer coefficient can be calculated by using the correlations for the vapor phase mass transfer coefficient and the heat transfer coefficient for the condensate film. The calculated values agree with the measured data to a mean absolute deviation of 14.3%.蒸気圧縮式ヒートポンプ、冷凍機の成績係数向上させることのできる作動媒体として、非共沸2成分混合冷媒が有望視されており、最近その凝縮熱伝達に関する研究が開発に行われている。非共沸2成分混合冷媒が凝縮する際には、低沸点蒸気が不凝縮ガスと類似な挙動を示すため、熱伝達係数が単成分蒸気に比べて低下する。したがって、この冷媒を用いる凝縮器については液膜の伝熱促進とともに混合気の物質伝達促進をはかる必要がある。著者らは伝熱促進管の一種であるワイヤフィン付きコルゲート管を内管とする水平二重管の環状部における冷媒R11およびR113ならびに非共沸混合冷媒R114/R113の凝縮な関する一連の実験を行い、圧力降下と熱伝達の特性を明らかにした。R114/R113に関する第1報では液膜の伝熱特性がR113の場合と同一であると仮定して、混合気相の物質伝達係数を求め、円管上の強制対流凝縮理論から導かれた無次元パラメータを用いてデータ整理を行った。また、圧力降下の摩擦成分は純冷媒に対する実験式によって良好に整理できることを示した。第2報では、第1報の内管とフィン配列が多少異なる内管を使用し、外管内径を2種類に変化させて混合気相の物質伝達特性をより詳細に調べた。その結果、第1報で得られた物質伝達の式は凝縮質量流束の影響をよく表現するが、質量速度の影響および予測精度に関しては十分でないことが明らかになった。本報では、管内の乱流熱・物質伝達に関する従来の実験および理論解析の結果をもとにして、より一般性のある物質伝達の整理式を導く。また、圧力降下の摩擦成分の整理法についても検討する。なお、記号表中には本報で用いる主な記号のみ列挙する。その他の記号は第2報と同一である

Horseradish Peroxidase-Decorated Artificial Viral Capsid Constructed from β-Annulus Peptide via Interaction between His-Tag and Ni-NTA

Artificial construction of spherical protein assemblies has attracted considerable attention due to its potential use in nanocontainers, nanocarriers, and nanoreactors. In this work, we demonstrate a novel strategy to construct peptide nanocapsules (artificial viral capsids) decorated with enzymes via interactions between His-tag and Ni-NTA. A β-annulus peptide derived from the tomato bushy stunt virus was modified with Ni-NTA at the C-terminus, which is directed toward the exterior surface of the artificial viral capsid. The β-annulus peptide bearing Ni-NTA at the C-terminus self-assembled into capsids of about 50 nm in diameter. The Ni-NTA-displayed capsids were complexed with recombinant horseradish peroxidase (HRP) with a C-terminal His-tag which was expressed in Escherichia coli. The β-annulus peptide-HRP complex formed spherical assemblies whose sizes were 30–90 nm, with the ζ-potential revealing that the HRP was decorated on the outer surface of the capsid

Planetary Growth with Collisional Fragmentation and Gas Drag

As planetary embryos grow, gravitational stirring of planetesimals by embryos strongly enhances random velocities of planetesimals and makes collisions between planetesimals destructive. The resulting fragments are ground down by successive collisions. Eventually the smallest fragments are removed by the inward drift due to gas drag. Therefore, the collisional disruption depletes the planetesimal disk and inhibits embryo growth. We provide analytical formulae for the final masses of planetary embryos, taking into account planetesimal depletion due to collisional disruption. Furthermore, we perform the statistical simulations for embryo growth (which excellently reproduce results of direct $N$-body simulations if disruption is neglected). These analytical formulae are consistent with the outcome of our statistical simulations. Our results indicate that the final embryo mass at several AU in the minimum-mass solar nebula can reach about $\sim 0.1$ Earth mass within $10^7$ years. This brings another difficulty in formation of gas giant planets, which requires cores with $\sim 10$ Earth masses for gas accretion. However, if the nebular disk is 10 times more massive than the minimum-mass solar nebula and the initial planetesimal size is larger than 100 km, as suggested by some models of planetesimal formation, the final embryo mass reaches about 10 Earth masses at 3-4 AU. The enhancement of embryos' collisional cross sections by their atmosphere could further increase their final mass to form gas giant planets at 5-10 AU in the solar system.Comment: Accepted for publication in Icaru

Dramatic morphological changes in liposomes induced by peptide nanofibers reversibly polymerized and depolymerized by the photoisomerization of spiropyran

Cytoskeletons such as microtubules and actin filaments are natural protein assemblies, which dynamically control cellular morphology by reversible polymerization/depolymerization. Recently, the control of polymerization/depolymerization of fibrous protein/peptide assemblies by external stimuli has attracted significant attention. However, as far as we know, the creation of an “artificial cytoskeleton” that reversibly controls the polymerization/depolymerization of peptide nanofiber in giant unilamellar vesicles (GUVs) has not been reported. Here, we developed peptide nanofiber self-assembled from spiropyran (SP)-modified β-sheet-forming peptides, which can be reversibly polymerized/depolymerized by light. The reversible photoisomerization of the SP-modified peptide (FKFECSPKFE) to the merocyanine-peptide (FKFECMCKFE) by ultraviolet (UV) and visible light irradiation was confirmed by UV–visible spectroscopy. Confocal laser scanning microscopy with thioflavin T staining and transmission electron microscopy of the peptides showed that the SP-peptide formed β-sheet nanofibers, whereas the photoisomerization to the merocyanine-peptide almost completely dissociated the nanofibers. The merocyanine peptide was encapsulated in spherical GUVs comprising of phospholipids as artificial cell models. Interestingly, the morphology of GUV encapsulating the merocyanine-peptide dramatically changed into worm-like vesicles by the photoisomerization to the SP-modified peptide, and then reversibly changed into spherical GUV by the photoisomerization to the MC-modified peptide. These dynamic morphological changes in GUVs by light can be applied as components of a molecular robot with artificially controlled cellular functions