Cuticular penetration of 2,4-D as affected by interaction between a diethylene glycol monooleate surfactant and apple leaf cuticles

Impacts of pH and sorption-desorption of ‘Pegosperse’ 100-O (PEG. 100-O; diethylene glycol monooleate, containing 15% diester) surfactant by apple (Malus pumila M.) leaf cuticles on surfactant-enhanced cuticular penetration of 2,4-D [(2,4-dichlorophenoxy)acetic acid] were studied. Glass cylinders were affixed to enzymatically isolated adaxial apple leaf cuticles after the cuticle segments had been soaked in 10 ml liter^?1 PEG 100-O solution and washed for 20 and 120 min, respectively. Quantities of [¹⁴C]2,4-D in the glass-cuticle chambers passing through the cuticles at pH values from 1 to 6 5 were determined. PEG 100-O significantly increased cuticular penetration of dissociated 2,4-D at pH 4–5; the surfactant had no effect on penetration of undissociated 2,4-D at pH 10. Surfactant-enhanced penetration of 2,4-D occurred only when the surfactant was in the cuticles, while the process of surfactant sorption-desorption alone had no effect on penetration. These results support a ‘hydrophilic channel’ hypothesis, i.e. that surfactants may create hydrophilic channels or increase the area of the channels in the cuticle and, consequently, enhance the passing of polar molecules like dissociated 2,4-D through the cuticle.     

Effects of nonionic surfactants on cuticular sorption and penetration of 2, 4-dichlorophenoxy acetic acid

Surfactants increase the uptake of some foliar-applied chemicals to a greater extent than would be expected from their effects on surface tension and spray coverage. This study of the uptake of 2, 4-D [(2, 4-dichlorophenoxy)acetic acid] evaluated the effect of surfactants on penetration through and sorption by isolated cuticles of apple leaves. [¹⁴C]2, 4-D was placed in glass chambers affixed to enzymatically isolated adaxial apple leaf cuticles after the cuticle segments had been treated with various surfactants. The same surfactant pretreatments were included in sorption studies in which cuticle segments were immersed in [¹⁴C]2, 4-D for 96 h. Quantities of 2, 4-D passing through or sorbed by the cuticle were determined. Similar experiments were conducted with unaltered cuticles and cuticles dewaxed with chloroform. The hydrophile-lipophile balance (HLB) of polyethylene-glycol-based surfactants was inversely related to the sorption of those surfactants by the cuticles and penetration of 2, 4-D. Sorption of 2, 4-D by apple leaf cuticles was unaffected by surfactant pretreatment. Dewaxed cuticle membranes showed a similar response to 2, 4-D penetration and sorption following the surfactant pretreatment.     

Sorption of low levels of nonionic and anionic surfactants on soil: effects on sorption of triticonazole fungicide

The sorption of two anionic surfactants and a series of seven nonionic alkylphenolethoxylate surfactants of increasing hydrophilic/lipophilic balance (HLB) in a loamy clay soil was evaluated. The effect of low doses of these surfactants on the sorption characteristics of the fungicide triticonazole was investigated. The critical micellar concentration (CMC) of the surfactants in pure water and soil–water systems, and surfactant sorption were estimated by surface tension measurements using a batch equilibration technique. Triticonazole sorption, alone and in the presence of low doses of surfactants, was also measured by batch equilibration. CMC of the alkylphenol surfactants increased with their HLB. The sorption of surfactants increased with their lipophilicity. CMC in the soil–water systems were considerably higher than in pure water. Sorption of the most lipophilic alkylphenol surfactants at the higher doses significantly increased triticonazole sorption. Proposed mechanisms are modifications of soil surface properties, and increase of soil organic carbon content. Sorption of the other nonionic and anionic surfactants only resulted in monomeric surfactant concentrations in pore water, and did not affect triticonazole sorption. © 1998 Society of Chemical Industry     

Cuticular lipids of two resistant and a susceptible strain of houseflies

A study was made of the composition of the cuticular lipids of two resistant strains of houseflies (Rutgers and Fc), both of which show a reduced rate of absorption of insecticides as a partial mechanism of resistance and a susceptible strain (CSMA). Total lipids, monoglycerides, diglycerides and sterol esters (except in the Fc strain), sterols, fatty acids and phospholipid phosphorus were higher in resistant strains than in the susceptible strain. Phosphatidyl-ethanolamine and phosphatidyl-choline were major constituents of the phospholipid fractions and were appreciably higher in the resistant strains. Cuticular wax contents did not differ among strains. Incorporation of lipid precursors, [U-¹⁴]acetate and [³²P]orthophosphate, was greater in the cuticle of one or both resistant strains, depending on the lipid component examined.     

Influence of some nonionic surfactants on water sorption by isolated tomato fruit cuticles in relation to cuticular penetration of glyphosate

The effects of several nonionic surfactants on [¹⁴C]glyphosate mono(isopropylammonium) diffusion across isolated tomato fruit cuticles (Lycopersicon esculentum Mill.) were compared under controlled atmospheric conditions (25°C; 65% R.H.) using a model system consisting of 1-μl droplets applied to isolated cuticles on agar blocks. Rates of diffusion for glyphosate (10 g acid equivalent litre^?1 in the applied solution) and overall amounts recovered in underlying agar blocks were influenced by the ethylene oxide (EO) chain length for a homologous nonylphenol surfactant series (10 g litre^?1). Glyphosate uptake increased with EO content, reaching an optimum at a mean of 17 EO, then decreasing below control values for surfactants with 40 EO. There was a strong influence of the hydrophobe on glyphosate penetration for different surfactants with similar mean EO content (10 EO). The primary aliphatic amine enhanced penetration the most, followed by the nonylphenol while the aliphatic alcohol showed no improvement on glyphosate transfer across cuticles. Water soprtion was greatly enhanced by a primary aliphatic amine (10 EO) and by a nonylphenol (17 EO). The aliphatic alcohol (10 EO) and a shorter-chained nonylphenol (4 EO) did not significantly enhance water sorption. Comparison of water sorption with glyphosate diffusion across cuticles suggests a strong relationship between the two. Change in solution pH over a limited range had no significant effect. Promotion of cuticular hydration by surfactants may thus play an important role in the enhancement of foliar uptake of water-soluble herbicides such as glyphosate.     

Degradation of a sulfonamide herbicide as a function of soil sorption

The degradation of DE-498 (proposed common name flumetsulam) was studied in 21 US soils as a first step in developing a management plan for this new herbicide. Degradation half-lives were shorter in soils that adsorbed the compound less. Adsorption was lower in soils with higher pH and lower organic carbon content. Degradation half-lives were thus influenced by both pH and organic carbon: they were in the range 2–4 weeks in higher pH soils (pH 5 7.0) unless the organic carbon content was above 2.5%, at which half-lives were in the range 1–3 months. In medium pH soils (6.4 pH 6.9) half-lives were 1–2 months, while in lower pH soils (5.9 pH 6.3) they were 1–4 months. The laboratory data were supported by the response of sunflowers (Helianthus annuus L.) planted 1 year after application of flumetsulam to different soils. A quantitative model relating half-life to sorption K_d (r²= 0.85) was coupled with an additional equation relating sorption K_d to the proportion of neutral and anionic forms of the compound at different pH values. The study allows estimates of this herbicide's degradation in soil to be made if its pH and organic carbon content are known. Degradation d'un herbicide sulfonamide en fonction de la capacité d'absorption du sol La dégradation du flumetsulam a étéétudiée dans les sols aux Etats Unis comme premier stade dans le développement d'un plan d'utilisation de ce nouvel herbicide. Les demi-vies de dégradation étaient plus courtes dans les sols qui absorbaient moins le produit. L'absorption était plus faible dans les sols à pH élevé et à faible teneur en carbone organique. Les demi-vies étaient ainsi sous l'influence du pH et du carbone organique: elles étaient de 2 à 4 semaines pour les pH de sols élevés (pH 7) sauf si le carbone organique était au dessus de 2,5%, dans ce cas, les demi-vies etaient de 1 à 3 mois. Dans les sols à pH moyen (6,4 pH 6,9) les demi-vies étaient de 1 à 2 mois, tandis que dans les sols à pH faible (5,9 pH 6,3) elles étaient de 1 à 4 mois. Les résultats de laboratoire ont été confirmés par le comportement de tournesols plantés un an aprfès l'application de flumetsulam dans différents sols. Un modèle reliant la demi-vie au coefficient d'absorption Kd (r²= 0.85) a été couplé avec une équation additionelle reliant le coefficient d'absorption Kd à la proportion de particules neutres et anioniques de la molécule aux différents pH. L'étude permet de faire des estimations de la dégradation de cet herbicide dans le sol dès que le pH et la teneur en carbone organique sont connus. Abbau eines Sulfonamid-Herbizids als Funktion der Bodensorption Der Abbau von Flumetsulam (DE-498) wurde in 21 Böden untersucht, um eine Grundlage zur Produktentwicklung dieses neuen Herbizids zu gewinnen. Die 50%ige Verlustrate (DT₅₀) war in schwächer sorptiven Böden kürzer. Bei hohem pH-Wert und geringem Gehalt an organischer Substanz war die Adsorption schwächer. Die DT₅₀ wurde durch den pH-Wert und den Gehalt organischer Substanz wie folgt beeinflußt: Sie betrug 2 bis 4 Wochen in Böden mit pH >7,0 (wenn der C_org-Gehalt nicht über 2,5% lag; dort dann 1 bis 3 Monate), 1 bis 2 Monate bei 6,4 < pH < 6,9 und 1 bis 4 Monate bei 5,9 < pH < 6,3). Die Ergebnisse der Laboruntersuchungen wurden durch Untersuchungen an Sonnenblumen gestützt. die 1 Jahr nach Applikation von Flumetsulam auf verschiedenen Böden angebaut wurden. Ein quantitatives Modell über das Verhältnis der Verlustrate zum Sorptionskoeffizienten K_d (r²= 0,85) wurde mit einer zusätzhchen Gleichung der Beziehung des Sorptionskoeffizienten K_d zum Verhältnis der neutralen und der anionischen Verbindungen des Wirkstoffs bei verschiedenen pH-Werten verknüpft. Aufgrund der Untersuchungen kann der Abbau dieses Herbizids in Böden bekannten pH-Werts und C_org-Gehalts abgeschätzt werden.     

Analysis,sorption and residues of a homologous series of isothiocyanates on wheat

A series of isothiocyanates (R-NCS, R, 1–6 carbon atoms) was applied in the vapour phase to wheat in sealed containers. The speed of sorption, as measured by the rate of loss from the intergranular air space, was inversely proportional to molecular weight; e.g. the time for 50% sorption of hexyl isothiocyanate was over 100 times longer than for the methyl analogue. Despite extensive sorption, most of the applied chemicals was recovered from the fumigated wheat seven days after dosing, indicating that sorption did not lead to extensive degradation. Purge and trap techniques proved suitable for recovery of low-boiling, but not high-boiling chemicals.     

双叉犀金龟表皮蛋白Td14144表达纯化及性质研究

表皮蛋白是昆虫表皮的重要组成成份,在昆虫的生长发育过程中起着重要作用,有可能成为农业害虫的防治靶标。双叉犀金龟Trypoxylus dichotomus是铁皮石斛的一种重要害虫,且对其表皮蛋白的研究较少。本文通过研究双叉犀金龟表皮蛋白Td14144的表达纯化及与几丁质结合的相关性质明确Td14144功能的重要性。根据双叉犀金龟转录组测序数据,利用RT-PCR获得表皮蛋白Td14144基因（GenBank登录号：MZ463195）,并对其进行生物信息学分析。序列分析表明表皮蛋白Td14144属于CPR家族中RR-2亚族,含有R&R保守结构域;系统进化分析结果表明,Td14144与光肩星天牛Anoplophora glabripennis的AgCP的亲缘关系最近。随后将基因片段与pET-28a载体同源重组构建表达载体pET28a-14144,在大肠杆菌Escherichia coli BL21中原核表达,并使用金属螯合层析进行分离纯化,SDS-PAGE及Western blot验证重组蛋白的表达纯化,成功获得95%以上纯度的Td14144蛋白。利用几丁质结合试验评估Td14144与不同类型几丁质结合的能力,发现Td14144可以与壳聚糖、α-几丁质、β-几丁质和胶体几丁质结合,其中对壳聚糖和α-几丁质的结合能力最强。     

亚洲玉米螟表皮蛋白CPR9的表达纯化及与几丁质的相互作用

亚洲玉米螟Ostrinia furnacalis是我国玉米最重要的害虫,了解亚洲玉米螟表皮形成的机制将有助于对其开展生物防治。表皮蛋白和几丁质是构成昆虫表皮的两种主要成分,因此研究两者的相互作用对于阐明昆虫表皮形成机制具有关键意义。CPR9是亚洲玉米螟体壁表皮转录组中相对丰度最高的表皮蛋白基因。序列分析发现CPR9属于CPR家族中RR-1亚家族的表皮蛋白,含有R&R结构域,可能是通过结合几丁质来发挥功能。为了研究CPR9与几丁质的相互作用,本研究利用pET-SUMO载体实现了SUMO-CPR9融合蛋白的可溶表达,并通过SUMO蛋白酶处理及两次金属螯合亲和层析纯化了CPR9,平均收率为5 mg/L。几丁质结合试验发现,CPR9对不同类型的几丁质的结合具有选择性。CPR9对α-几丁质结合能力很强,对胶体几丁质结合能力较强,但不与β-几丁质结合。脱乙酰几丁质（壳聚糖）结合试验发现,CPR9能与脱乙酰几丁质结合并使其发生团聚。圆二色光谱分析表明,CPR9在结合脱乙酰几丁质后,其二级结构中平行β折叠和β转角比例上升,反平行β折叠及无规卷曲比例下降。本研究发现了CPR家族表皮蛋白与不同类型几丁质的结合存在特异性,而且在结合过程中会发生结构变化,有助于进一步了解昆虫表皮的形成机制。     

Influence of formulation on triticonazole solubilisation and sorption in a soil–water system

The effect of agronomic doses of three suspension concentrate formulations and two anionic surfactant adjuvants on the solubilisation and sorption characteristics of triticonazole fungicide in a loamy clay soil was investigated. Soil sorption of [¹⁴C]triticonazole alone, in the formulations, and in the presence of increasing doses of formulation additives was measured using the classical batch equilibration technique. Triticonazole solubilisation in water‐formulation systems was also evaluated using a batch procedure, and sorption of the formulation aqueous phases on soil was examined. Solubilisation of triticonazole in the formulation systems occurred in excess of the solubility in water (S_w). This was attributed to triticonazole association with surfactant monomers. Sorption isotherms of triticonazole with diluted surfactants and other formulation additives were similar to that of triticonazole alone. We concluded that in soil‐formulation systems, triticonazole solubilisation in excess of the S_w may increase the amount available in soil solution for plant absorption. However, triticonazole molecules preferentially associated with the soil surfaces, and the presence of diluted amounts of the formulation adjuvants would not significantly affect the soil sorption process. © 2000 Society of Chemical Industry     

三氟苯嘧啶在5种土壤中的吸附与解吸附行为

为研究三氟苯嘧啶的吸附-解吸附特性,采用振荡平衡法研究了三氟苯嘧啶在采集于吉林通化、江苏扬州、江西萍乡、广西南宁和海南海口等地的5种土壤中的吸附-解吸附行为及其环境影响因素。结果表明:三氟苯嘧啶在土壤中的吸附动力学符合Elovich模型,吸附和解吸附等温线符合Freundlich模型,吸附常数在1.886~7.626。温度的升高更有利于吸附,土壤对三氟苯嘧啶的吸附主要是物理吸附;随着溶液中pH值的升高,土壤对三氟苯嘧啶的吸附能力逐渐下降。除广西南宁黏壤土外,三氟苯嘧啶在5种土壤中的解吸附过程中存在滞后现象,不易在土壤中长期积累,具有一定的迁移特性。     

Enhanced soil sorption of methidathion using sewage sludge and surfactants

Batch experiments were carried out to examine the partitioning of an organophosphorus insecticide, methidathion, in non-amended agricultural soil and soil amended with urban sewage sludge and/or different types of surfactant. Kinetic data showed that sewage sludge significantly reduced adsorption rate, whereas amendment of the soil with the cationic surfactant tetradecyltrimethylammonium bromide (TDTMA) at 10 x CMC (critical micellar concentration) increased the adsorption rate by a factor of 10. The adsorption isotherms were evaluated using the Freundlich model. The soil adsorption capacity for methidathion was enhanced by amendment with sewage sludge and even more significantly with TDTMA at 10 x CMC or combined with sewage sludge. TDTMA conferred a high hydrophobic character to the soil, enhancing the adsorption capacity of the rather hydrophobic methidathion. The amendment of soil both with sewage sludge and TDTMA combines the increased hydrophobicity with a higher surfactant retention by organic matter, due to an increase in cation exchange capacity, which promotes even more the adsorption capacity for the insecticide. An anionic surfactant, linear alkylbenzene sulfonate, and the non-ionic Tween 80 only induced a slight modification in the kinetics and adsorption of methidathion.     

Role of sorption and degradation in the herbicidal function of isoxaflutole

BACKGROUND: The fate of isoxaflutole (IFT) in soil is closely related to soil sorption. Sorption and transformation of IFT were investigated in laboratory incubations with four soils, and these results were used to interpret greenhouse studies using IFT to control several weed species. RESULTS: Degradation proceeded by previously observed pathways to form diketonitrile (DKN) and benzoic acid (BA) derivatives, as well as traces of unidentified products. Over the course of the incubation, DKN was the dominant active form of the herbicide present in the experimental system, and was thus critical to the soil activity of the herbicide for weed control. CONCLUSION: Control of most weed species appeared to be a function of both sorption and biodegradation of DKN, with greatest weed control being observed in soils in which a significant portion of the DKN that was formed persisted and remained bioavailable over the course of the incubation. Copyright © 2009 Society of Chemical Industry     

鱼藤酮在3种土壤中的吸附-解吸附特性

为了综合评价鱼藤酮在土壤环境中的吸附-解吸附特性,采用批量平衡法,系统研究了鱼藤酮在砂壤土、黏壤土及壤土3种农业土壤中的吸附-解吸附行为。结果表明,鱼藤酮在3种土壤中的吸附-解吸附行为符合Freundlich模型 (R2≥0.946 8),吸附常数 (K_f-ads) 在1.52~11.39之间,吸附能力为:黏壤土 > 砂壤土 > 壤土;而解吸附常数 (K_f-des) 在1.02~4.55之间,解吸附强弱次序为壤土 > 黏壤土 > 砂壤土。鱼藤酮在砂壤土、黏壤土和壤土3种土壤中有机碳吸附常数 (K_OC) 分别为982、101 7和219,而滞后系数 (H) 分别为0.687 3、0.556 9和0.892 3,表明鱼藤酮在黏壤土及砂壤土中移动性较弱,有正迟滞作用,而在壤土中移动性较强,无迟滞作用。该研究将对鱼藤酮的环境风险评估具有一定的理论指导意义。     

Mechanisms of herbicide sorption in microalgae and the influence of environmental factors

The sorption kinetics of photosystem II herbicides in the unicellular microalgae Ankistrodesmus braunii are independent of the herbicide concentration. While diuron-type herbicides attain an equilibrium state of sorption after at most 5 min, it takes up to 60 min for phenol-type herbicides. The kinetics of the inhibition of photosynthetic electron transport display a good correlation to the kinetics of sorption. For both types of herbicides, a phase of prevalent partitioning into the lipid phase of the cell membranes preceeds binding to thylakoid membranes. With phenol-type herbicides this phase is much more extended than with diuron-type compounds. As a consequence, there is no displacement of previously bound herbicides of this type from algal cells by addition of an excess of other photosystem II herbicides. The sorption of phenol-type herbicides to microalgae is under strong influence of environmental factors, such as light, temperature, pH, or oxygen concentration. Thus, besides the lipophilicity of these biocides, the response of the target cells to environmental factors is at least as important for herbicide sorption in the cells. From these results it is concluded that a prediction of the biocide accumulation in aquatic microorganisms can only be partly deduced from the properties of the pesticide molecule. The target cells and their complex responses to their environment strongly relativize correlations of chemical properties, e.g., lipophilicity and biological activity.