Exchange of monooleoylphosphatidylcholine with single egg phosphatidylcholine vesicle membranes

In a previous paper we described the experiments and the framework of a model for the exchange of monooleoylphosphatidylcholine with a single egg phosphatidylcholine membrane. In the present paper a model is presented that relates the experimentally measured apparent characteristics of the overall kinetics of lysolipid exchange to the true rates of lysolipid exchange and interbilayer transfer. It is shown that the adsorption of the lysolipid follows two pathways: one through the adsorption of lipid monomers and other through the fusion of micelles. The desorption of lysolipid follows a single pathway, namely, the desorption of monomers. The overall rate of fast desorption under convective flow conditions gives the true rate of monomer desorption from the outer membrane monolayer. The overall rate of both slow lysolipid uptake and slow desorption gives the rate of interbilayer transfer. Because of the uneven distribution of lysolipid between the two monolayers during its uptake, one of the membrane monolayers is apparently extended relative to the other. This relative extension of one of the monolayers induces a monolayer tension. The induced monolayer tension can increase up to 7 mN.m-1, when most of the intercalated lysolipid only partitions into the monolayer facing the lysolipid solution. This value is similar to the measured value for the critical monolayer tension of membrane failure, which is on the order of 5 mN.m-1. The similarity of the magnitudes of the induced monolayer tension during monooleoylphosphatidylcholine exchange and the monolayer tension of membrane failure suggests that the interbilayer lipid transfer may be affected by the formation of short living membrane defects. Furthermore, the pH-induced interbilayer exchange of phosphatidylglycerol is considered. In this case, it is shown that the rate of interbilayer transfer is a function of the phosphatidylglycerol concentration in the membrane.     

Zolpidem is differentiated from triazolam in humans using a three-response drug discrimination procedure

The discriminative stimulus effects of the imidazopyridine hypnotic zolpidem and the classic benzodiazepine hypnotic triazolam were examined in seven healthy volunteers using a three-response drug discrimination procedure and a within-subject design. During an initial sampling phase, the training drug conditions (placebo, 20 mg/70 kg zolpidem, and 0.5 mg/70 kg triazolam) were identified to subjects by letter codes before oral drug administration. During a subsequent training phase, subjects earned money for correct drug identifications made 3.75 h after drug administration. Five out of seven subjects acquired the three-response discrimination. Analyses of standardized and unstructured self-report questionnaires revealed that zolpidem and triazolam produced different profiles of effects; zolpidem was associated with a number of negative somatic symptoms including nausea, blurred vision, visual images/hallucinations, and heavy limbs, whereas triazolam was associated with greater sedative effects. These results demonstrate a distinct profile of discriminative stimulus and subjective effects for zolpidem, relative to triazolam, which is consistent with its somewhat distinct pharmacological profile, and provide evidence for the sensitivity of the three-response drug discrimination procedure for detecting between-drug differences.     

Azide Reactive Dyes

Reactive dyes containing a sulphonylazide group can undergo fixation on nylon substrates by two different mechanisms. Under aqueous dyeing conditions, at or below 120d? C, the free amino end-groups of the polymer attack the sulphonylazide group with displacement of azide ion, and results in attachment of the dye to the substrate by a sulphonamide linkage. In contrast, if the dyed substrate is subjected to dry heat fixation at 170d? C, the azide group decomposes to a sulphonylnitrene species which undergoes insertion into C-H bonds of the polymer. The dye is again attached by a sulphonamide bridge, but in this case the amount of dye that can be fixed is independent of the amino end-group content of the polymer.     

Effect of preheating on chemical structure and infrared spectra of Yanzhou coal

The results of thermosolvolysis experiments performed on a high volatile bituminous coal from Yanzhou, China are described. The coal was preheated in a vacuum at temperatures between 250 and 400 °C, after which the soluble materials were extracted with chloroform, l.r. spectra of the preheated coal, the chloroform extract, and the residue after extraction were measured and compared. The extraction yield passed through a maximum for a preheating temperature near the plastic softening point of the coal. As the preheating temperature was increased, the aromaticity of the coal and its residue after extraction increased markedly. The aromaticity of the extract appeared to increase slightly and the methylene-methyl ratio of the extract dropped significantly near the softening temperature. The ester content of the extract was reduced to almost zero on preheating the coal, presumably because of decarboxylation during preheating.     

Activity of quassinoids as antifeedants against aphids

A series of quassinoids was tested for antifeedant activity against the aphidMyzus persicae (Hemiptera, Aphididae). Isobrucein B, brucein B and C, glaucarubinone, and quassin decreased feeding at concentrations down to 0.05% and isobrucein A was effective at 0.01%. Only quassin showed no phytotoxic effects and is therefore the most promising compound for further development.     

1，4-环己二酮单乙二醇缩酮的合成研究

对1,4-环已二酮的单保护反应进行了研究,在自制催化荆催化下,用n(乙二醇)∶n(1,4-环己二酮)=1∶1进行脱水缩合反应,在环己烷溶液中除去部分未保护的原料,在乙酸乙酯中用亚硫酸氢钠提取单保护产物,用10%的碳酸钠脱去亚硫酸氢钠,结晶精制而得产品1,4-环己二酮单乙二醇缩酮[1,4-二氧杂螺(4,5)癸烷-8-酮],收率为68.2%,气相色谱测定其纯度为99.8%.