Quantitative characterization of a biological membrane by means of its spatial autocovariance.

Profiles for the exoplasmic face (EF) of the freeze-fractured plasma membrane from the root storage tissue of red beets are reconstructed by microdensitometry of micrographs of surface-shadowed-platinum carbon replicas. Autocovariance functions (ACFs) are computed from those profiles. The initial portions of the ACFs have a Gaussian form whose parameters (root mean square surface roughness and autocovariance length) are estimated. The parameter estimates are used to show that the pits on the EF faces are in good complementarity with the intramembrane particles seen on the complementary protoplasmic fracture faces.     

The effects of heat treatment on physical and technological properties and surface roughness of Camiyani Black Pine (Pinus nigra Arn. subsp. pallasiana var. pallasiana) wood

Heat treatment is often used to improve the dimensional stability of wood. In this study, the effects of heat treatment on physical properties and surface roughness of Camiyani Black Pine (Pinus nigra Arn. subsp. pallasiana var. pallasiana) wood were examined. Samples obtained from Yenice-Zonguldak Forest Enterprises, Turkey, were subjected to heat treatment at varying temperatures and for varying durations. The physical properties of heat-treated and control samples were tested, and oven-dry density, air-dry density, and swelling properties were determined. The mechanical properties of heat-treated and control samples were tested, and compression strength, and Janka-hardness were determined. A stylus method was employed to evaluate the surface characteristics of the samples. Roughness measurements by the stylus method were made in the direction perpendicular to the fiber. Four main roughness parameters, mean arithmetic deviation of profile (Ra), mean peak-to-valley height (Rz), root mean square roughness (Rq), and maximum roughness (Ry) obtained from the surface of wood were used to evaluate the effect of heat treatment on the surface characteristics of the specimens. Significant difference was determined (p=0.05) between physical and technological properties, and surface roughness parameters (Ra, Rz, Ry, Rq) for three temperatures and three durations of heat treatment. Based on the findings in this study, the results showed that density, swelling, compression strength, Janka-hardness and surface roughness values decreased with increasing treatment temperature and treatment times. Increase in temperature and duration further diminished technological strength values of the wood specimens. Camiyani Black Pine wood could be utilized by using proper heat treatment techniques without any losses in strength values in areas where working, stability, and surface smoothness, such as in window frames, are important factors.     

Observation of optimal gecko's adhesion on nanorough surfaces

In this letter we report experimental observations on the times of adhesion of living Tokay geckos (Gekko geckos) on polymethylmethacrylate (PMMA) inverted surfaces. Two different geckos (male and female) and three surfaces with different root mean square (RMS) roughness (RMS=42, 618 and 931 nm) have been considered, for a total of 72 observations. The measured data are proved to be statistically significant, following the Weibull Statistics with coefficients of correlation between 0.781 and 0.955. The unexpected result is the observation of a maximal gecko adhesion on the surface with intermediate roughness of RMS=618 nm, that we note has waviness comparable to the seta size.     

Electrosprayed Molybdenum Trioxide Aqueous Solution and Its Application in Organic Photovoltaic Cells

A molybdenum trioxide thin film with smooth surface and uniform thickness was successfully achieved by an electrospray deposition method using an aqueous solution with a drastically low concentration of 0.05 wt%. Previous papers demonstrated that an additive solvent technique is useful for depositing the thin film by the electrospray deposition, and the high vapor pressure and a low surface tension of an additive solvent were found to be important factors. As a result, the smooth molybdenum trioxide thin film was obtained when the acetonitrile was used as the additive solvent. Furthermore, the vapor pressure of acetone is much higher than that of aqueous solution, and this indicates that the acetone is easily evaporated after spraying from the glass capillary. By optimizing a concentration of acetone in the molybdenum aqueous solution, a minimum root mean square roughness of the MoO₃ thin film became 3.7 nm. In addition, an organic photovoltaic cell was also demonstrated using the molybdenum trioxide as a hole transport layer. Highest photoconversion efficiency was 1.72%, a value comparable to that using conventional thermal evaporation process even though the aqueous solution was used for the solution process. The photovonversion efficiency was not an optimized value, and the higher value can be achieved by optimizing the coating condition of the active layer.     

Relative quantitation of restriction fragment length polymorphic DNAs via DNA melting analysis provides an effective way to determine allele frequencies

To accurately and precisely estimate the allele frequencies in DNA pools for a cost-effective approach to correlate genetic variations to phenotypic traits, we exploited differential melting kinetics between restriction fragment length polymorphic DNAs. The allele frequencies of two SNPs in a series of DNA mixtures with known allelic compositions of the SNPs were determined by analyzing the meltings of restricted PCR amplicons, yielding a result with a root mean square error (RMSE) of 0.014 relative to the expected values and a standard deviation (SD) of 0.018 from triplicate measurements. This method was then applied in the measurement of genotype frequencies in DNA pools in which varying numbers of genomic DNAs were intermingled while maintaining uniform quantitative contribution. Analyses of 10 SNPs demonstrated the feasibility of this method in an economical and highly accurate manner as the results yielded an RMSE value of 0.027 and a SD of 0.019.     

Coarse-grained molecular dynamics of tetrameric transmembrane peptide bundles within a lipid bilayer

The conformations of model transmembrane peptides are studied to understand the structural and dynamical aspects of tetrameric bundles using a series of coarse grain (CG) molecular dynamics (MD) simulations since membrane proteins play a crucial role in cell function. In this work, two different amphipathic models have been constructed using similar hydrophobic/hydrophilic characteristics with two structurally distinct morphologies to evaluate the effect of roughness and hydrophilic topology on the structure of tetrameric bundles, one class that forms an ion-channel and one class that does not. Free energy calculations of typical amphipathic peptide topologies show that using a relatively smooth surface morphology allows for a stable conformation of the tetramer bundle in a diamond formation. However, the model with side chains attached to the core in order to roughen the surface has a stable square tetramer bundle which is consistent with experimental data and all-atom (AA) MD simulations. Comparisons of the CG simulations with AA MD simulations are in reasonable agreement with the formation of tetrameric homo-oligomers, partitioning within the lipid bilayer and tilt angle with respect to the bilayer normal. We concluded that a square or diamond shape tetrameric homo-oligomers could be stabilized by rational design of the peptide morphology and topology of the surface, thus allowing us to tune the permeability of the bundle or channel.     

Surface myoelectric signals during ergocycle exrcises at various mechanical powers and pedalling rates

The surface myoelectric (ME) signal from the vastus lateralis muscle was studied during ergocycling at various mechanical powers (MPs) and pedalling rates (PRs). The envelope of the signal was described using a power spectral density function estimate at very low frequency. A highly smoothed burst pattern was found independently at 80 rpm on MP. The envelope presence in surface ME signals was demonstrated to affect the total band power spectrum estimate slightly. In addition, the total band power spectrum changes with MPs and PRs were described using the root mean square value and the mean power frequency. Total band power spectrum was enhanced and shifted toward the low frequencies as PR increased. It was shifted toward the high frequencies as MP increased. These changes were attributed to the progressive recruitment of fast fibers.     

Observation of optimal gecko's adhesion on nanorough surfaces

In this letter we report experimental observations on the times of adhesion of living Tokay geckos (Gekko geckos) on polymethylmethacrylate (PMMA) inverted surfaces. Two different geckos (male and female) and three surfaces with different root mean square (RMS) roughness (RMS = 42, 618 and 931 nm) have been considered, for a total of 72 observations. The measured data are proved to be statistically significant, following the Weibull Statistics with coefficients of correlation between 0.781 and 0.955. The unexpected result is the observation of a maximal gecko adhesion on the surface with intermediate roughness of RMS = 618 nm, that we note has waviness comparable to the seta size.     

Surface EMG of proximal leg muscles in neuromuscular patients and in healthy controls. Relations to force and fatigue.

In an effort to find parameters to evaluate patients with neuromuscular disorders, surface electromyography (SEMG) of proximal leg muscles was performed in 33 patients with myotonic dystrophy (MyD), 29 patients with Charcot-Marie-Tooth (CMT) disease and 20 healthy controls. The root mean square (RMS) of the SEMG amplitude (microV) was calculated at different torque levels. Endurance (seconds) and median frequency (Fmed) of the SEMG power spectrum, used as parameters of fatigue, were determined at 80% of MVC. Maximum voluntary contraction (MVC) was found to be decreased in patients; the ratio between RMS values of antagonists and agonists was increased and torque-EMG ratios (Nm/microV) were decreased. These differences with respect to controls were more pronounced in MyD than in CMT. The initial Fmed value was lowest in CMT. The greatest decrease in Fmed was found in MyD. SEMG data in relation to force have not been determined before in groups of MyD or CMT patients. In both disorders, parameters differed from controls, which means that adding SEMG to strength measurements could be useful in studying the progress of the disorder and the effects of interventions.     

Electrooptical monitoring of cell polarizability and cell size in aerobic <Emphasis Type="Italic">Escherichia coli</Emphasis> batch cultivations

The time-dependent development of cell polarizability and length in Escherichia coli batch fermentations were observed at-line with electrooptical measurements. While using a measurement system with fully automated sample preparation, the development of these properties can be observed with a comparable high frequency (six measurements per hour). The polarizability as well as the mean cell length both increase soon after inoculation and then decline from the growth phase on until the stationary phase is reached. Based on the dynamic behavior of polarizability, the growth phase can be divided into four distinct stages. Changes in the cultivation temperature or the pre-cultivation conditions lead to alterations in the development of the polarizability and mean cell length. Based on the frequency disperse of polarizability measured at four different frequencies from 210 to 2,100 kHz, a prediction model is established that is based on the relation of the polarizability to the metabolic activity. Applying multi-linear partial least squares methods (N-PLS), the model is able to predict the specific acetate synthesis and uptake with a root mean square error of prediction of 0.19 (6% of the mean). The method represents a tool for characterization of different stages with respect to microbial metabolic activity and the energy balance during batch cultivations.     

Electrical noise from lipid bilayer membranes in the presence of hydrophobic ions

In the presence of the hydrophobic ion dipicrylamine, lipid bilayer membranes exhibit a characteristic type of noise spectrum which is different from other forms of noise described so far. The spectral density of current noise measured in zero voltage increases in proportion to the square of frequency at low frequencies and becomes constant at high frequencies. The observed form of the noise spectrum can be interpreted on the basis of a transport model for hydrophobic ions in which it is assumed that the ions are adsorbed in potential-energy minima at either membrane surface and are able to cross the central energy barrier by thermal activation. Accordingly, current-noise results from random fluctuations in the number of ions jumping over the barrier from right to left and from left to right. On the basis of this model the rate constant ki for the translocation of the hydrophobic ion across the barrier, as well as the mean surface concentration Nt of adsorbed ions may be calculated from the observed spectral intensity of current noise. The values of ki obtained in this way closely agree with the results of previous relaxation experiments. A similar, although less quantitative, agreement is also found for the surface concentration Nt.     

Determination of cell mass and polymyxin using multi-wavelength fluorescence

Multi-wavelength fluorescence was applied for on-line monitoring of cell mass and the antibiotic polymyxin B in Bacillus polymyxa cultivations. By varying the phosphate and nitrogen content of the medium different polymyxin-cell mass ratios could be obtained. Using this strategy, it was possible to investigate if multi-wavelength fluorescence is able to give independent prediction of the two parameters. Partial least square (PLS) regression was applied to establish mathematical relationships between off-line determined cell mass and polymyxin concentrations and on-line collected fluorescence data. For polymyxin one universal PLS model, with a correlation of 0.95 and a root mean square error of cross validation (RMSECV) of 35 mgl(-1), could be constructed. However, correlation between fluorescence and cell mass dry weight could not be established including data from all three types of cultivations. For data from each type of cultivation, separate models with high correlation and low RMSECV values were built. A large variation in cellular composition as a result of the different levels of nitrogen and phosphorus in the cultivations was the probable reason to the necessity of building three models. The results of the present investigation indicate that production of polymyxin is concomitantly regulated by phosphate and nitrogen as the highest polymyxin yield on cell mass, 0.17+/-0.01 gg(-1), was reached in the cultivations where both nitrogen and phosphate concentrations were kept low.     

Tank-tread frequency of the red cell membrane: dependence on the viscosity of the suspending medium

Single human red cells were suspended in media with viscosities ranging from 12.9 to 109 mPa s and subjected to shear flow ranging from 1/s to 290/s in a rheoscope. This is a transparent cone-plate chamber adapted to a microscope. The motion of the membrane around red cells oriented in a steady-state fashion in the shear field (tank-tread motion) was videotaped. The projected length and width of the cells as well as the frequency of tank-tread motion were measured. One-thousand eight-hundred seventy-three cells of three blood donors were evaluated. The frequency increased with the mean shear rate in an almost linear fashion. The slope of this dependence increased weakly with the viscosity of the suspending medium. No correlation was found between the frequency and four morphological red cell parameters: the projected length and width of the cells as well as the ratio and the square root of the product of these quantities. The energy dissipation within the red cell membrane was estimated based on the measured parameters and compared to the energy dissipation in the undisturbed shear flow. At constant mean shear rate the rise of the energy dissipation with viscosity is slower whereas at constant viscosity the rise with the shear rate is steeper than in the undisturbed shear flow. A fit of the data collected in this work to a theoretical red cell model might allow one to determine intrinsic mechanical constants in the low deformation regime.     

The effects of heat treatment on physical properties and surface roughness of red-bud maple (Acer trautvetteri Medw.) wood

Heat treatment is often used to improve the dimensional stability of wood. In this study, the effects of heat treatment on physical properties and surface roughness of red-bud maple (Acer trautvetteri Medw.) wood were examined. Samples obtained from Düzce Forest Enterprises, Turkey, were subjected to heat treatment at varying temperatures and durations. The physical properties of heat-treated samples were compared against controls in order to determine their; oven-dry density, air-dry density, and swelling properties. A stylus method was employed to evaluate the surface characteristics of the samples. Roughness measurements, using the stylus method, were made in the direction perpendicular to the fiber. Three main roughness parameters; mean arithmetic deviation of profile (Ra), mean peak-to-valley height (Rz), and maximum roughness (Rmax) obtained from the surface of wood, were used to evaluate the effect of heat treatment on the surface characteristics of the specimens. Significant differences were determined (p>0.05) between surface roughness parameters (Ra, Rz, Rmax) at three different temperatures and three periods of heat treatment. The results showed that the values of density, swelling and surface roughness decreased with increasing temperature treatment and treatment times. Red-bud maple wood could be utilized successfully by applying proper heat treatment techniques without any losses in investigated parameters. This is vital in areas, such as window frames, where working stability and surface smoothness are important factors.     

运用SmartRoot测量橡胶树细根

SmartRoot是基于开放源ImageJ的免费根系分析软件, 通过软件分析根系照片可得到细根长度、表面积、体积和平均根直径等指标。该文以橡胶树(Hevea brasiliensis)细根为例, 探索利用SmartRoot分析细根不同形态特征的可能性。用不同拍照距离与分析方式的对比确定橡胶树细根适合的研究方法, 用WinRhizo软件分析结果验证结果的准确性。结果表明, 不同拍摄高度下对应的细根长度、表面积、体积和平均根直径等指标的标准均方根误差(NRMSE)分别为2.87%、15.73%、32.38%和16.88%; 手动分析与半自动分析相同照片细根长度、表面积、体积和平均根直径等指标的NRMSE分别为3.06%、21.00%、 40.96%和11.64%; 用WinRhizo软件验证SmartRoot分析细根长度、表面积、体积和平均根直径等指标结果NRMSE分别为5.31%、9.37%、9.61%和5.77%。本研究表明, 在适当方法下, 拍照法结合SmartRoot软件分析测量橡胶树细根细根长度、表面积、体积和平均根直径等指标有较高的准确度, 可用于橡胶树细根指标的分析。     

Flow-dependent concentration polarization of plasma proteins at the luminal surface of a semipermeable membrane

The effect of steady shear flow on concentration polarization of plasma proteins and lipoproteins at the luminal surface of a semipermeable vessel wall was studied experimentally using suspensions of these molecules in a cell culture medium and a semipermeable membrane dialysis tube which served as a model of an implanted vascular graft or an artery. The study was carried out by flowing a cell culture medium containing fetal calf serum or bovine plasma lipoproteins or bovine albumin through a 7.5 mm diameter, 60 mm-long dialysis tube in steady flow under a physiologic mean arterial perfusion pressure of 100 mmHg, and measuring the filtration velocity of water (cell culture medium) at the vessel wall which varied as a consequence of the change in concentration of plasma protein particles at the luminal surface of the semipermeable membrane dialysis tube. It was found that for perfusates containing plasma proteins and/or lipoproteins, filtration velocity of water was the lowest in the absence of flow, and it increased or decreased as the flow rate (hence wall shear rate) increased or decreased from a certain non-zero value, indicating that surface concentration of protein particles varied reversibly as a direct function of flow rate. It was also found that at particle concentrations equivalent to those found in a culture medium containing serum at 5% by volume, plasma lipoproteins which were much smaller in number and lower in concentration but larger in size than albumin, had a much larger effect on the filtration velocity of water than albumin. These findings were very much the same as those previously obtained with a cultured endothelial cell monolayer, strongly suggesting that the flow-dependent variation in filtration velocity of water at a vessel wall results from a physical phenomenon, that is, flow-dependent concentration polarization of low density lipoproteins at the luminal surface of the endothelial cell monolayer.     

原子力显微镜定量测定采后蘑菇的表面粗糙度

蘑菇表面的失水情况是评价采后蘑菇质量的重要指标.我们提出用原子力显微镜定量测定蘑菇表皮的粗糙度来表示表面的皱缩程度,用算术平均粗糙度和平方根粗糙度表示.双孢蘑菇(Agaricus bisporus(Lange)Sing)贮藏前的算术平均粗糙度为(34.033±5.116)nm,经过2d贮藏,在2℃、25℃和动态温度自发气调贮藏下,其算术平均粗糙度分别为(40.139±3.359)nm、(65.356±8.253)nm和(43.670±9.280)nm.平方根粗糙度值与算术平均粗糙度值有相似的变化趋势,两者均随贮藏时间的延长和温度的增加而增大.表皮的三维图像直观地表示出水分的蒸发过程,变化趋势符合粗糙度值的变化,特别是在贮藏的早期阶段(0～2 d).由粗糙度分析的结果可以区别不同的贮藏条件表明,原子力显微镜测定的粗糙度指标可有效地表示采后蘑菇的表面失水情况.     

Purification of the major outer membrane protein of Azospirillum brasilense, its affinity to plant roots, and its involvement in cell aggregation

The major outer membrane protein (MOMP) of the nitrogen-fixing rhizobacterium Azospirillum brasilense strain Cd was purified and isolated by gel filtration, and antiserum against this protein was obtained. A screening of the binding of outer membrane proteins (OMPs) of A. brasilense to membrane-immobilized root extracts of various plant species revealed different affinities for the MOMP, with a stronger adhesion to extracts of cereals in comparison with legumes and tomatoes. Moreover, this protein was shown to bind to roots of different cereal seedlings in an in vitro adhesion assay. Incubation of A. brasilense cells with MOMP-antiserum led to fast agglutination, indicating that the MOMP is a surface-exposed protein. Cells incubated with Fab fragments obtained from purified MOMP-antiserum immunoglobulin G exhibited significant inhibition of bacterial aggregation as compared with controls. Bacteria preincubated with Fab fragments showed weaker adhesion to corn roots in comparison to controls without Fab fragments. These findings suggest that the A. brasilense MOMP acts as an adhesin involved in root adsorption and cell aggregation of this bacterium.