深圳地区参考作物蒸散量计算方法适用性分析

根据深圳1998~2007日值气象资料,以4种方法计算参考作物蒸散量,并以FAO Penman-Monteith公式计算结果为标准,评价其他各公式在深圳的适用性。结果表明:Irmark-Allen公式的月平均参考作物蒸散量及年参考作物蒸散量与Penman-Monteith公式结果没有显著差异,与Hargreaves公式和Pristley-Taylor公式计算结果差异显著,Hargreaves最大,Pristley-Taylor最小;Irmark-Allen公式、Pristley-Taylor公式与Penman-Monteith公式的相关性较高,而Hargreaves相关性较低。Irmark-Allen法可作为深圳地区缺少相关气象资料条件下计算ET0较理想的替代方法。     

Continual reassessment method for partial ordering

Summary Much of the statistical methodology underlying the experimental design of phase 1 trials in oncology is intended for studies involving a single cytotoxic agent. The goal of these studies is to estimate the maximally tolerated dose, the highest dose that can be administered with an acceptable level of toxicity. A fundamental assumption of these methods is monotonicity of the dose–toxicity curve. This is a reasonable assumption for single‐agent trials in which the administration of greater doses of the agent can be expected to produce dose‐limiting toxicities in increasing proportions of patients. When studying multiple agents, the assumption may not hold because the ordering of the toxicity probabilities could possibly be unknown for several of the available drug combinations. At the same time, some of the orderings are known and so we describe the whole situation as that of a partial ordering. In this article, we propose a new two‐dimensional dose‐finding method for multiple‐agent trials that simplifies to the continual reassessment method (CRM), introduced by O'Quigley, Pepe, and Fisher (1990, Biometrics 46 , 33–48), when the ordering is fully known. This design enables us to relax the assumption of a monotonic dose–toxicity curve. We compare our approach and some simulation results to a CRM design in which the ordering is known as well as to other suggestions for partial orders.     

A colorimetric method for the evaluation of anti-giardial drugs in vitro

The aim of this study was to develop a simple and reliable method to determine the viability of Giardia intestinalis after incubation with an anti-giardial agent by using a colorimetric method. Factors that may affect the optical density value were systematically evaluated. The most suitable conditions were obtained when G. intestinalis trophozoites, 5 × 10⁵ cells/ml were incubated with the anti-giardial agent for 48 h. The culture medium was removed and trophozoites were immediately fixed by immersing the whole plate in absolute methanol for 2 min. The fixed trophozoites were then stained with 0.1% w/v methylene blue for 10 min, washed once by immersing the whole plate into distilled water. The dye was released by adding 0.1 M hydrochloric acid solution (300 μl) and the optical density was read at 655 nm. The 50% inhibitory concentration values (IC₅₀) of metronidazole, ornidazole and furazolidone obtained from our proposed method (0.41 ± 0.06, 0.18 ± 0.01, 0.26 ± 0.13 μg/ml, respectively) were comparable to the IC₅₀ values obtained by the current conventional method (0.14 ± 0.05, 0.15 ± 0.04, 0.14 ± 0.02 μg/ml, respectively). This new method did provide a convenient and reliable way to screen for potential anti-giardial agents.     

Hydrothermal synthesis, characterization, and KOH activation of carbon spheres from glucose

Carbon spheres (CSs) with controllable sizes and rich in oxygen-containing groups were fabricated using a simple hydrothermal treatment of glucose. The effects of the hydrothermal parameters, including the concentration of glucose, reaction temperature, duration, and the second hydrothermal treatment were investigated. The obtained CSs were then activated using KOH for the eventual preparation of porous carbon spheres. A scanning electron microscope was used to characterize the morphology and size of the CSs. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to analyze the functional surface groups. N₂ adsorption–desorption isotherms were used to analyze the porous structure of the CS. The results revealed that the morphologies and size distribution of the CSs can be controlled by adjusting the experimental parameters. A hydrothermal temperature between 180 and 190 °C over 4–5 h was suitable for CS formation. Under these conditions, the size of the CS increased with the concentration of glucose. Mono-dispersed CSs with good morphologies and large numbers of oxygen-containing functional groups (primarily –OH and CO) can be obtained using a 0.3 mol/L glucose solution that is hydrothermally treated at 190 °C for 4 h. The resulting CSs sizes were about 350 nm in diameter. After a second hydrothermal treatment, the sizes of CSs grew nearly 250 nm without damage to its morphology or broadening of their size distribution. Porous CSs with perfectly spherical shapes and fully developed structures (S_BET = 1282.8 m²/g, V_micro = 0.44 cm³/g) could then be obtained via KOH activation.     

Syntheses of chitin-based imprinting polymers and their binding properties for cholesterol

A novel chitin derivative, cholesteryl chitin carbonate (Chitin-Chol), was synthesized from chitin and cholesteryl chloroformate. This product was characterized by Fourier transform infrared (FTIR) spectroscopy and solid-state ¹³C nuclear magnetic resonance (¹³C NMR), and was used as a covalently bound template precursor for imprinting cholesterol. After cross-linking with toluene 2,4-diisocyanate, it was efficiently cleaved hydrolytically to afford a guest-binding site accompanying the easy and efficient removal of a sacrificial spacer. The selectivity and efficacy of a chitin-based imprinting polymer for steroid binding were assessed by a chromatographic screening process. The results of binding experiments showed that this molecular imprinting polymer (MIP) has a high binding capacity with cholesterol. The target discrimination towards cholesterol over its close structural analogue suggested that the polymer recognition site was possible on the basis of the inversion of configuration of a single hydroxyl group. In addition, non-covalent imprinting was done using chitin as a precursor and its binding properties for cholesterol were also evaluated.     

Interactions of the DNA polymerase X from African Swine Fever Virus with the ssDNA. Properties of the total DNA-binding site and the strong DNA-binding subsite

Interactions of the polymerase X from the African Swine Fever Virus with the ssDNA have been studied, using quantitative fluorescence titration and fluorescence resonance energy transfer techniques. The primary DNA-binding subsite of the enzyme, independent of the DNA conformation, is located on the C-terminal domain. Association of the bound DNA with the catalytic N-terminal domain finalizes the engagement of the total DNA-binding site of the enzyme and induces a large topological change in the structure of the bound ssDNA. The free energy of binding includes a conformational transition of the protein. Large positive enthalpy changes accompanying the ASFV pol X-ssDNA association indicate that conformational changes of the complex are induced by the engagement of the N-terminal domain. The enthalpy changes are offset by large entropy changes accompanying the DNA binding to the C-terminal domain and the total DNA-binding site, predominantly resulting from the release of water molecules.     

一种高效获取基因5′末端的RACE方法

RACE技术是一种快速高效克隆基因5′末端和3′末端的方法,是获取基因全长的主要手段之一,但是RACE技术本身也存在一些缺点。我们在前人改良的RACE技术基础上进一步优化RACE技术,获得了一种操作简单、快速、高效、成本低廉的改良RACE方法,该方法适合于大量基因5′末端的获取,可以在普通实验室推广应用。     

Optimization of a sample preparation method for the metabolomic analysis of clinically relevant bacteria

Metabolomics, or metabolite profiling, is an approach that is increasingly used to study the metabolism of diverse organisms, elucidate biological processes and/or find characteristic biomarkers of physiological states. Here, we describe the optimization of a method for global metabolomic analysis of bacterial cultures, with the following steps. Cells are grown to log-phase, starting from an overnight culture and bacterial concentrations are monitored by measuring the optical density of the cultures at 600 nm. At an appropriate density they are harvested by centrifugation, washed three times with NaCl solution and metabolites are extracted using methanol and a bead-mill. Dried extracts are methoxymated and derivatized with methyltrimethylsilyltrifluoroacetamide (MSTFA) then analyzed using gas chromatography coupled to time-of-flight mass spectrometry (GC-MS/TOF). Finally, patterns in the acquired data are examined by multivariate data modeling. This method enabled us to obtain reproducible metabolite profiles of Yersinia pseudotuberculosis, with about 25% compound identification, based on comparison with entries in available GC-MS libraries. To assess the potential utility of the method for comparative analysis of other bacterial species we analyzed cultures of Pseudomonas aeruginosa, Salmonella typhimurium, Escherichia coli and methicillin-sensitive Staphylococcus aureus (MSSA). Multivariate analysis of the acquired data showed that it was possible to differentiate the species according to their metabolic profiles. Our results show that the presented procedure can be used for metabolomic analysis of a wide range of bacterial species of clinical interest.     

Analysis of the glucagon receptor first extracellular loop by the substituted cysteine accessibility method

Glucagon is an important hormone for the prevention of hypoglycemia, and contributes to the hyperglycemia observed in diabetic patients, yet very little is known about its receptor structure and the receptor-glucagon interaction. In related receptors, the first extracellular loop, ECL1, is highly variable in length and sequence, suggesting that it might participate in ligand recognition. We applied a variant of the SCAM (Substituted Cysteine Accessibility Method) to the glucagon receptor ECL1 and sequentially mutated positions 197 to 223 to cysteine. Most of the mutations (15/27) affected the glucagon potency, due either to a modification of the glucagon binding site, or to the destabilization of the active receptor conformation. We reasoned that side chains accessible to glucagon must also be accessible to large, hydrophilic cysteine reagents. We therefore evaluated the accessibility of the introduced cysteines to maleimide-PEO₂-biotin ((+)-biotinyl-3-maleimido-propionamidyl-3,6-dioxa-octanediamine), and tested the effect of pretreatment of intact cells with a large cationic cysteine reagent, MTSET ([2-(trimethylammonium)ethyl]methanethiosulfonate bromide), on glucagon potency. Our results suggest that the second and third transmembrane helices (TM2 and TM3) are extended to position 202 and from position 215, respectively, and separated by a short β stretch (positions 203-209). Glucagon binding induced a conformational change close to TM2: L198C was accessible to the biotin reagent only in the presence of glucagon. Most other mutations affected the receptor activation rather than glucagon recognition, but S217 and D218 (at the top of TM3) were good candidates for glucagon recognition and V221 was very close to the binding site.     

A rapid DNA extraction method for PCR amplification from wetland soils

Aims: We tested a method of rapid DNA extraction from wetland soil samples for use in the polymerase chain reaction. Methods and Results: The glass bead/calcium chloride/SDS method obtained in the present study was compared with the calcium chloride/SDS/enzymatic extraction method and the UltraClean? Soil DNA Isolation Kit. Rapid DNA extraction could be completed within about two hours without purification steps. Conclusions: This study succeeded in establishing a fast soil DNA extraction protocol that can be applied to various environmental sources that are rich in humic acid content. Significance and Impact of the Study: The method provides a technology with high‐quality DNA extraction from soils for testing the diversity of AOB and AOA.