Dissipative particle dynamics simulation on the meso-scale structure of diblock copolymer under cylindrical confinement

The meso-scale structure of symmetric diblock copolymer under cylindrical confinement is studied by dissipative particle dynamics (DPD). The simulation results show that coiled cylindrical geometry is favored in the presence of larger cylinder radius (R/L ₀>～1.5), and the number of rings depends on the cylinder radius. Because of the cylinder wall's selectivity, each block can form the central core, but only the preferential block forms the outmost layer. An approximately linear relationship exists between structure transition point, which is approximately in proportion to the 3/5 exponential of chain length of copolymer and number of layers. As the cylinder radius is decreased, a helical morphology is found. Lamellae parallel to the underside of the cylinder appear when the cylinder radius is made smaller (R/L ₀ < ～1.1).     

Phosphorylation of C-terminal polycystin-2 influences the interaction with PIGEA14: A QCM study based on solid supported membranes

Polycystin-2 (PC2) trafficking has been proposed to be a result of the interaction of PIGEA14 with PC2 as a function of the phosphorylation state of PC2. Here, we investigated the interaction of PIGEA14 with the C-terminal part of polycystin-2 wild type (cPC2wt) and the pseudophosphorylated mutant (cPC2S812D) to first, quantify the binding affinity between cPC2 and PIGEA14 and second, to elucidate the influence of PC2 phosphorylation on PIGEA14 binding. Solid supported membranes composed of octanethiol/1,2-dioleoyl-sn-glycero-3-phosphocholine doped with the receptor lipid DOGS–NTA–Ni were used to attach PIGEA14 to the membrane via its hexahistidine tag. By means of the quartz crystal microbalance technique, binding affinities as well as kinetic constants of the interaction were extracted in a label-free manner by applying the scaled particle theory. The results show that the dissociation constant of cPC2 to PIGEA14 is in the 10 nM regime providing strong evidence of a very specific interaction of cPC2 with PIGEA14. The interaction of cPC2wt is twofold larger than that of cPC2S812D. The moderate higher binding affinity of cPC2wt to PIGEA14 is discussed in light of PC2 trafficking to the plasma membrane.     

Structure of native oligomeric Sprouty2 by electron microscopy and its property of electroconductivity

Receptor tyrosine kinases (RTKs) regulate many cellular processes, and Sprouty2 (Spry2) is known as an important regulator of RTK signaling pathways. Therefore, it is worth investigating the properties of Spry2 in more detail. In this study, we found that Spry2 is able to self-assemble into oligomers with a high-affinity KD value of approximately 16 nM, as determined through BIAcore surface plasmon resonance analysis. The three-dimensional (3D) structure of Spry2 was resolved using an electron microscopy (EM) single-particle reconstruction approach, which revealed that Spry2 is donut-shaped with two lip-cover domains. Furthermore, the method of energy dispersive spectrum obtained through EM was analyzed to determine the elements carried by Spry2, and the results demonstrated that Spry2 is a silicon- and iron-containing protein. The silicon may contribute to the electroconductivity of Spry2, and this property exhibits a concentration-dependent feature. This study provides the first report of a silicon- and iron-containing protein, and its 3D structure may allow us (1) to study the potential mechanism through the signal transduction is controlled by switching the electronic transfer on or off and (2) to develop a new type of conductor or even semiconductor using biological or half-biological hybrid materials in the future.     

Estimation of hurdle clearance parameters using a monocular human motion tracking method

This paper presents a method of monocular human motion tracking for estimation of hurdle clearance kinematic parameters. The analysis involved 10 image sequences of five hurdlers at various training levels. Recording of the sequences was carried out under simulated starting conditions of a 110 m hurdle race. The parameters were estimated using the particle swarm optimization algorithm and they are based on analysis of the images recorded with a 100 Hz camera. The proposed method does not involve using any special clothes, markers, inertial sensors, etc. As the quality criteria, the mean absolute error and mean relative error were used. The level of computed errors justifies the use of this method to estimate hurdle clearance parameters.     

Use of artificial neural networks for analysis of the factors affecting particle size in mebudipine nanoemulsion

In this study, a nanoemulsion containing mebudipine [composed of ethyl oleate (oil phase), Tween 80 (T80), Span 80 (S80) (surfactants), polyethylene glycol 400, ethanol (cosurfactants), and deionized water] was prepared with the aim of improving its bioavailability for an effective antihypertensive therapy. Particle size of the formulation was measured by dynamic light scattering. Then, artificial neural networks were used in identifying factors that influence the particle size of the nanoemulsion. Three variables, namely, amount of surfactant system (T80?+?S80), amount of polyethylene glycol, and amount of ethanol as cosurfactants, were considered as input values and the particle size was used as output. The developed model showed that all the three inputs had some degrees of effect on particles size: increasing the value of each input decreased the size. Furthermore, amount of surfactant was found to be the dominant factor in controlling the final particle size of nanoemulsion.

Communicated by Ramaswamy H. Sarma     

我国大麦和性花叶病毒（BaMMV）研究初报

本文根据F(ab′)2－ELISA和ISEM实验,结合病毒粒子长度测定,报道了江苏省如东县农科所大麦黄花病毒源（吕种盐辐矮早3）中除存在大麦花花叶病毒（BaYMV）外,还复合感染大麦和性花叶病毒（BaMMV）,这是我国BaMMV的第一次报道。     

The cyanobacterial genome contains a single copy of the ffh gene encoding a homologue of the 54 kDa subunit of signal recognition particle

Cyanobacteria possess thylakoid membranes that differ in their protein composition from the cytoplasmic membrane. To study possible pathways of protein targeting to these membranes, we have investigated whether or not cyanobacteria have a homologue or homologues of the signal recognition particle-like chaperone Ffh. We have amplified a fragment of ffh by polymerase chain reaction and established that ffh is present as a single copy in the genomes of three cyanobacterial species. We have cloned and sequenced ffh from Synechococcus sp. PCC7942 and predict that Ffh functions as a ribonucleoprotein in cyanobacteria and chloroplasts.     

Viscometric flow for a many-body dissipative particle dynamics (MDPD) fluid with Lees–Edwards boundary condition

Viscometric properties of polymer are explored by the many-body dissipative particle dynamics (MDPD) using Lees–Edwards boundary conditions. The equation of state for the MDPD system is modified by fitting the density correction to different values of the cut-off radius. Due to the many-body interactions in MDPD, the viscosity contributed from the conservative force increases considerably with increasing repulsive coefficient, density and cut-off radius, and cannot be ignored compared to the ‘standard’ DPD case. The influence of these parameters on the MDPD viscosity is investigated, and we propose an equation to predict the viscosity in MDPD model. Additionally, the dumbbell polymer suspension model is investigated in the MDPD fluid, and the relations concerning first normal stress difference and shear rate, the relaxation time and spring constant, are consistent to theoretical works. We conclude that the MDPD model can be used to investigate the dynamics of non-Newtonian droplets.     

生物炭对土壤水分蒸发的影响

为确定干旱区生物炭的合理施用量及其对土壤水文过程的影响,采用室内土柱试验,研究了3种生物炭添加量(5%、10%和15%)和4种生物炭类型(d<0.25 mm竹炭、0.25 mm<d<1 mm竹炭、d<0.25 mm木炭和0.25 mm <d<1 mm木炭;d为粒径)对地下水补给、土壤持水能力、土壤水分上升运动和蒸发的影响.结果表明: 生物炭对地下水补给、土壤持水能力、土壤水分上升运动和蒸发都有明显影响,但生物炭原料和粒径不同,其影响效果不同;随生物炭施加量的升高,地下水对土壤补给量增大;添加生物炭可提高土壤持水能力,促进土壤水含量的上升速度,其中,添加竹炭效果大于木炭,小粒径生物炭大于大粒径生物炭;生物炭添加量较低(5%)时能有效抑制土壤蒸发,但添加量过高则可能促进土壤蒸发.干旱地区土壤适当施用生物炭可提高土壤保墒能力.