Effects of Application Methods and Plastic Covers on Distribution of Cis- and Trans-1,3-Dichloropropene and Chloropicrin in Root Zone

This study examined the effects of three application methods (chisel injection, Avenger coulter injection, and drip irrigation) and two plastic films (polyethylene film [PE] and virtually impermeable film [VIF]) on distribution of cis- and trans- 1,3-dichloropropene (1,3-D) and chloropicrin (CP) in a Florida sandy soil after application of Telone C35 or Telone In-Line. Regardless of application method, VIF retained greater amounts of cis- and trans-1,3-D and CP in the root zone with longer residential time than PE. There was better retention of the three compounds in the root zone when applied with the Avenger coulter injection rig than chisel injection, especially in combination with VIF. Distribution of the three compounds in the root zone was less predictable when applied by drip irrigation. Following drip irrigation, more than 50% of the three compounds in the PE and VIF-covered beds was found near the end of the drip tapes in one experiment, whereas the distribution was much more uniform in the root zone in a second experiment. Among the three biologically active compounds, CP disappeared from the root zone more rapidly than cis- and trans-1,3-D, especially in the PE-covered beds.     

旱地小麦施氮和地膜栽培的氮素效应与淋溶

在陕西长武旱塬进行的试验表明,小麦施用氮肥增产显著。在小麦生育前期持续干旱条件下,地膜覆盖并没有使小麦表现出较好的增产效果。施用氮肥或氮肥与有机肥配施都可能引起NO3^-向深层淋溶,而且氮肥用量越大,淋溶量及深度愈大;施用有机肥NO3^-累积现象减弱。小麦对硝态氮主要吸收深度范围为0～80cm;不同施肥处理对土壤剖面NH4^ 的影响不大。施用氮肥会明显增加小麦吸氮量,但氮肥利用率随其用量增加而降低。试验条件下,低(施氮量为100kg／hm^2)、高(施氮量为150kg／hm^2)两种氮肥用量时的氮肥利用率分别为52％和27％,有机肥氮的利用率为12％。     

Exploring the interactions of gliadins with model membranes: Effect of confined geometry and interfaces

Mechanisms leading to the assembly of wheat storage proteins into proteins bodies within the endoplasmic reticulum (ER) of endosperm cells are unresolved today. In this work, physical chemistry parameters which could be involved in these processes were explored. To model the confined environment of proteins within the ER, the dynamic behavior of γ‐gliadins inserted inside lyotropic lamellar phases was studied using FRAP experiments. The evolution of the diffusion coefficient as a function of the lamellar periodicity enabled to propose the hypothesis of an interaction between γ‐gliadins and membranes. This interaction was further studied with the help of phospholipid Langmuir monolayers. γ‐ and ω‐gliadins were injected under DMPC and DMPG monolayers and the two‐dimensional (2D) systems were studied by Brewster angle microscopy (BAM), polarization modulation infrared reflection‐absorption spectroscopy (PM‐IRRAS), and surface tension measurements. Results showed that both gliadins adsorbed under phospholipid monolayers, considered as biological membrane models, and formed micrometer‐sized domains at equilibrium. However, their thicknesses, probed by reflectance measurements, were different: ω‐gliadins aggregates displayed a constant thickness, consistent with a monolayer, while the thickness of γ‐gliadins aggregates increased with the quantity of protein injected. These different behaviors could find some explanations in the difference of aminoacid sequence distribution: an alternate repeated ‐ unrepeated domain within γ‐gliadin sequence, while one unique repeated domain was present within ω‐gliadin sequence. All these findings enabled to propose a model of gliadins self‐assembly via a membrane interface and to highlight the predominant role of wheat prolamin repeated domain in the membrane interaction. In the biological context, these results would mean that the repeated domain could be considered as an anchor for the interaction with the ER membrane and a nucleus point for the formation and growth of protein bodies within endosperm cells. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 610–622, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

The effect of packing hydrophilization on bacterial attachment and the relationship with the performance of biotrickling filters

Many bioprocesses depend on the effective formation of a biofilm on a solid support. In the present study, three different surface treatments (sandblasting, pure‐O₂ plasma, and He–O₂ plasma treatments) were conducted on polypropylene (PP) Pall rings used as a support in biotrickling filters for air pollution control. The intent was to modify the ring surface and/or electrochemical properties in order to possibly improve cell adhesion, wetting properties, and possibly reduce the start‐up time and increase the performance of the biotrickling filters. The surface treatments were found to generally increase the hydrophilicity and the zeta potential of the surfaces. However, the startup and performance of lab‐scale biotrickling filters packed with treated Pall rings were not significantly different than the control with untreated rings. Cell and colloid deposition experiments conducted in flow cells showed that the treated surfaces and the hydrodynamic conditions were not favorable for cell deposition indicating that there could be significant opportunities for improving packings used in environmental bioprocess applications. Biotechnol. Bioeng. 2009;103: 1060–1067. © 2009 Wiley Periodicals, Inc.     

含铜抗菌不锈钢的抗菌性能研究

对铁素体和奥氏体2种含铜抗菌不锈钢的抗菌性能进行了考察.采用覆膜法检测抗菌率,用透射电镜观察与铁素体抗菌不锈钢作用后的大肠埃希菌细胞形态.2种抗菌不锈钢材料对供试的 17 株常见菌,除产气肠杆菌外均显示较强的抗菌性能,抗菌谱广;铁素体和奥氏体对1×107 cfu/mL及以下浓度的大肠埃希菌在 24 h内杀灭率达到99%;铁素体和奥氏体分别在作用 3 h和 9 h时可将1×107 cfu/mL的大肠埃希菌全部杀灭;打磨次数和环境温度的变化不影响2种抗菌不锈钢的杀菌率;透射电镜结果显示,与抗菌不锈钢作用后的大肠埃希菌菌体结构松散,细胞壁和细胞膜破裂,有内容物漏出.铁素体和奥氏体抗菌不锈钢均具优良的抗菌性能,抗菌谱广,与其作用后的细菌菌体破裂,有内容物溶出,最终致菌死亡.     

Tuning of the Zernike phase-plate for visualization of detailed ultrastructure in complex biological specimens

In order to acquire phase-contrast images with adequate contrast, conventional TEM requires large amount of defocus. Increasing the defocus improves the low-frequency components but attenuates the high-frequency ones. On the other hand, Zernike phase-contrast TEM (ZPC-TEM) can recover low-frequency components without losing the high-frequency ones under in-focus conditions. ZPC-TEM however, has another problem, especially in imaging of complex biological specimens such as cells and tissues; strong halos appear around specimen structures, and these halos hinder the interpretation of images. Due to this problem, the application of ZPC-TEM has been restricted to imaging of smaller particles. In order to improve the halo appearance, we fabricated a new quarter-wave thin film phase-plate with a smaller central hole and tested it on vitreous biological specimens. ZPC-TEM with the new plate could successfully visualize, in in-focus images, the intracellular fine features of cultured cells and brain tissues. This result indicates that reduction of the central hole diameter makes ZPC-TEM applicable on size scales ranging from protein particles to tissue sections. The application of ZPC-TEM to vitreous biological specimens will be a powerful method to advance the new field of imaging science for ultrastructures in close-to-physiological state.     

Interaction of an artificial antimicrobial peptide with lipid membranes

Antimicrobial peptides constitute an important part of the innate immune defense and are promising new candidates for antibiotics. Naturally occurring antimicrobial peptides often possess hemolytic activity and are not suitable as drugs. Therefore, a range of new synthetic antimicrobial peptides have been developed in recent years with promising properties. But their mechanism of action is in most cases not fully understood. One of these peptides, called V4, is a cyclized 19 amino acid peptide whose amino acid sequence has been modeled upon the hydrophobic/cationic binding pattern found in Factor C of the horseshoe crab (Carcinoscorpius rotundicauda). In this work we used a combination of biophysical techniques to elucidate the mechanism of action of V4. Langmuir-Blodgett trough, atomic force microscopy, Fluorescence Correlation Spectroscopy, Dual Polarization Interference, and confocal microscopy experiments show how the hydrophobic and cationic properties of V4 lead to a) selective binding of the peptide to anionic lipids (POPG) versus zwitterionic lipids (POPC), b) aggregation of vesicles, and above a certain concentration threshold to c) integration of the peptide into the bilayer and finally d) to the disruption of the bilayer structure. The understanding of the mechanism of action of this peptide in relation to the properties of its constituent amino acids is a first step in designing better peptides in the future.     

CFD transient simulation of the cough clearance process using an Eulerian wall film model

In this study, a cough cycle is reproduced using a computational methodology. The Eulerian wall film approach is proposed to simulate airway mucus flow during a cough. The reproduced airway domain is based on realistic geometry from the literature and captures the deformation of flexible tissue. To quantify the overall performance of this complex phenomenon, cough efficiency (CE) was calculated, which provided an easily reproducible measurement parameter for the cough clearance process. Moreover, the effect of mucus layer thickness was examined. The relationship between the CE and the mucus viscosity was quantified using reductions from 20 to 80%. Finally, predictions of CE values based on healthy person inputs were compared with values obtained from patients with different respiratory diseases, including chronic obstructive pulmonary disease (COPD) and respiratory muscle weakness (RMW). It was observed that CE was reduced by 50% in patients with COPD compared with that of a healthy person. On average, CE was reduced in patients with RMW to 10% of the average value of a healthy person.     

Study of water vapor and surfactant absorption by lipid model systems using the quartz crystal microbalance

Skin is constantly exposed to surfactants which compromise the essential barrier function of normal healthy skin. To model the interactions of surfactants with the barrier lipids of the stratum corneum (SC), it is essential to develop in vitro and in vivo quantitative measurement methods to predict, evaluate, and demonstrate the effect of the different surfactant chemistries and technologies on skin. In the current work, in vitro water vapor uptake and surfactant absorption onto skin lipid model films were quantitatively studied using a technique based on the piezoelectric effect, the quartz crystal microbalance (QCM). This approach is straightforward and reliable in providing subtle surface/interface related mass change information with high resolution and sensitivity. The results show that barrier properties of the lipid model system may be damaged by surfactant absorption, as well as by long-term water exposure due to alterations to the lipid film structure. Surfactant absorption is found to be concentration dependent even beyond its critical micelle concentration (CMC). QCM results for different surfactant systems are consistent with reported clinical data in showing that clinically milder surfactants (SLES) do not perturb the film as much as clinically harsh surfactants (SDS).     

4-(Ethoxycarbonyl) phenyl-1-amino-oxobutanoic acid-chitosan complex as a new matrix for silver nanocomposite film: preparation, characterization and antibacterial activity

The present work describes the preparation of new chitosan complex with 4-(ethoxycarbonyl) phenyl-1-amino-oxobutanoic acid (ETHA), as a matrix for silver nanoparticles to obtain a nanocomposite film by solution casing method. The characterization of the prepared nanocomposite film was made by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TG) and scanning electron microscopy (SEM). The optical property of nanocomposite film was analyzed by UV-Visible and photo-luminescence (PL) spectroscopy. The nanocomposite film was screen for antibacterial activity with Staphylococcus aureus (gram positive), Pseudomonas aurigionasa (gram negative) and Escherichia coli (gram negative) bacteria by adopting the disk diffusion method. The result of antibacterial study revealed that the prepared nanocomposite film may be a promising candidate for wide range of bio-medical applications.