Glycerol Layer Research Articles

An improved method for measuring aggregation of certain streptococcal bacteria found in dental plaque

Various cells were incubated with either dextran or sucrose and the reaction was terminatec by the addition of a 20 per cent solution of formaldehyde. A reaction mixture consisting of cells and aggregated cells was applied to a step-gradient glycerol column (0–60 per cent) and 0.5 ml fractions were collected from the bottom of the column. Non-aggregated cells remained: n the top layer of the column. Aggregated cells settled in the 30 per cent glycerol layer as determined by either spectrophotometric or radioactive methods. The amount of aggregated cells demonstrated in this layer increased with either incubation time or concentration of sucrose, dextran or cells. Cells of Strep. mutans strains 6715, AHT. 10449, OMZ-176. OMZ-175 and two mutants of Strep. mutans strain 6715 (designated C4 and C307) aggregated strongly. Cells of Strep. mutans strain LM7 aggregated weakly, whereas cells of Strep. mutans 6715 mutant U AB 165. a mutant defective in aggregation. Strep. mutans strain BHT, Strep. salivarius and Strep. sanyuis did not aggregate in the presence of either sucrose or dextran. Experiments testing co-aggregation between two different types of cells were done by using 3H-labelled and 14C-labelled cells. Strep. mutans strain 6715 co-aggregated with Strep. sanguis in the presence of sucrose or dextran, whereas Strep. mutans strain 6715 did not aggregate with Strep. salivarius. The method separates aggregated from non-aggregated cells and enables quan-titation of sucrose- or dextran-induced aggregation and co-aggregation.

A rapid and inexpensive procedure for the purification of adenovirions

A procedure for the purification of adenovirions is described. About 99 per cent pure adenovirions were obtained within only eight hours by use of chloroform treatment and two cycles of simultaneous sedimentation velocity and isopycnic centrifugation through a glycerol layer into a preformed potassium bromide gradient.

Rising behavior of air bubbles in superposed liquid layers

AbstractAn air bubble that passes through a horizontal interface from a lower layer of Freon‐113 to an upper layer of aqueous glycerol forms a two‐phase bubble in the upper layer as a result of entrainment of a certain volume of Freon‐113 from the lower layer. The volume of entrained Freon‐113 and the rise velocity of such a two‐phase bubble have been measured. The former increases with an increase of the bubble size irrespective of the viscosity of the upper liquid. The latter is somewhat lower than that of a normal air bubble of the same size.

Ultra-thin Layer of Lipids in Polymer Film and Its Electric Properties. New Sorption Method to Prepare a Model Biomembrane System

Abstract The ultra-thin layer of glycerol α-cis-9-octadecenate (glycerol α-monooleate:GMO) could be formed by impregnating nitrocellulose (NC) film with GMO and by then filling microscopically the interstices of the network structure of NC with microdrops of GMO. The dielectric dispersion characteristic of this film was found to be similar to that observed for bimolecular films. In a concentrated KCl solution (100 mM), however, an anomalous dielectric dispersion phenomenon was observed below 10 kHz. The low-frequency dispersion was attributed to surface conductance along the planes of contact between the GMO microdrops and the NC network. The ultra-thin film of di(cis-9-octadecenyl)phosphate (dioleyl phosphate: DOPH) could also be formed by this method. When a constant DC voltage (50 mV) was applied across the film in a 20 mM KCl solution, the electric current through the whole system changed periodically.

Fluorescent probes of biological membranes.

FLUORESCENT AND PHOSPHORESCENT PROBES THAT HAVE READILY INTERPRETABLE EMISSION PROPERTIES CAN BE SPECIFICALLY INSERTED INTO BIOLOGICAL MACROMOLECULES TO REVEAL FACETS OF THEIR STRUCTURE AND DYNAMICS: (1) Proximity. Singlet-singlet and triplet-singlet energy transfer can serve as spectroscopic rulers in the 10-65 A range, whereas triplet-triplet transfer can be used to show that two groups are less than about 12 A apart. (2) Rotational mobility. Nanosecond fluorescence polarization measurements can reveal whether a macromolecular system has any modes of flexibility in times of nanoseconds. (3) Polarity. The presence of mobile dipoles in the environment of certain chromophores is reflected in their fluorescence quantum yield and emission spectrum. We have synthesized a number of new fluorescent probes for biological membranes. Anthroyl stearic acid (I), dansyl phosphatidyl ethanolamine (II), and octadecyl naphthylamine sulfonic acid (III) are readily incorporated into bilayer vesicles composed of phosphatidyl choline. The emission spectra of these probes in the vesicles indicate that the chromophore of I is located in the hydrocarbon region, that of II is located in the glycerol layer, and that of III is located at the aqueous interface of the bilayer. Thus, fluorescent chromophores can be selectively placed in different transverse regions of a model membrane system.

An approach to Produce Biodiesel From Non-edible <i>Jatropha curcus</i> Oil through Dual Step Process: Preesterification and Transesterification

Studies were carried out to produce potential biodiesel from non-edible oil of Jatropha curcus. Due to its high free fatty acid (12% FFA), the crude Jatropha oil was processed in two steps: the acid-catalyzed esterification and followed by the base-catalyzed transesterification. The first step reduced the FFA level to less than 1% in 1h at 50°C for the 0.40 w/w methanol-to-oil ratio with 1% w/w of H2SO4. After the reaction, the mixture was stagnated for an hour and the methanol-water upper layer was discarded. The second step converted the product of the first step into biodiesel and glycerol through transesterification using 0.20 w/w methanol-to-oil and 0.5% w/w NaOH to oil as alkaline catalyst at 65°C. The maximum yield of biodiesel (organic phase of upper layer) and fatty acid methyl esters (FAME) yield were achieved at about 95% and 84% within 1 hour respectively. The glycerol concentration in the byproduct (glycerol layer) obtained after dual step transesterification was found 32%. Key words: Jatropha curcus, Biodiesel, Esterification, Glycerol and Fatty acid DOI: 10.3329/bjsir.v44i3.4409 Bangladesh J. Sci. Ind. Res. 44(3), 347-352, 2009

Secondary-Electron Emission from Glycerol-Coated Copper Surfaces

This paper reports the results of an experimental determination of the secondary-emission characteristics of glycerol layers on copper surfaces. This work has as its motivation the use of glycerol as a working fluid in electric thrustors for spacecraft. Secondary-emission coefficients for glycerol are reported as a function of incident primary-electron energy. Primary-electron energy was varied from 200–900 eV and glycerol secondary-emission coefficients were found to vary from 2.5 to about 1.0. These results are compared with values for clean copper surfaces found by using the same apparatus.

Surface Areas of Clay Minerals as Derived from Measurements of Glycerol Retention

AbstractThe use of glycerol retention measurements to calculate surface areas of clay minerals is described. Assuming that the glycerol retained on external surfaces is monomolecular in thickness, and that both this layer and the monomolecular glycerol layers adsorbed on internal surfaces of montmorillonite, vermiculite, and halloysite are of the density of liquid glycerol, it is calculated that each percentage of glycerol retained corresponds to an area of 17.6 square meters per gram on external surfaces and 35.3 on internal surfaces. The corresponding figures for ethylene glycol retention under these conditions are 22.3 and 44.6, respectively. For nonexpanding clays, surface areas calculated from glycerol retention values agree well with published figures derived from Brunauer, Emmett, and Teller (B.E.T.) gas adsorption measurements. For montmorillonites, surface areas agree reasonably well with published determinations based on B.E.T. treatment using polar adsorbates. Values of surface area are also presented for samples of vermiculite and endellite and for the nonexpanding clay minerals—illite, kaolinite, halloysite, and allophane.Calculations of the surface area as a function of particle size for montmorillonites of hypothetically uniform particle sizes show that montmorillonites dispersed into very thin flakes must have an appreciable external surface. The ratio of internal to total surface is shown to furnish an estimate of the thickness of the individual montmorillonite flakes. Glycerol retention data for a Wyoming bentonite saturated with a number of different cations are interpreted as indicating particle thicknesses varying from 3 unit cells (about 30A) for Na+ saturation to about 20 unit cells for saturation with a number of polyvalent cations.

Studies in narcosis. IV. A simple and rapid method for the determination of ether in blood.

The principle of the method here described depends upon the separation of ether from blood by boiling a tannic acid blood mixture and determining the amount of recovered ether by differential absorption in concentrated sulfuric acid. Obtaining the gas sample requires 5 minutes and the entire procedure, 15 minutes. The methods described in the literature are time consuming.1, 2, 3A 30 cc. test tube is arranged in aspirator fashion. The rubber stopper is protected by a copper guard to reduce the exposure of rubber to ether vapor. Fifteen cc. of a 1 per cent tannic acid solution are put into the test tube to which 1 cc. of oxalated blood is added. The test tube is stoppered, the tube extending into the liquid is closed by means of a pinchcock and the tube extending only through the stopper is connected with a sampling tube containing concentrated calcium chloride solution covered with a generous layer of glycerol in which ether is practically insoluble. With the sampling tube under negative pressure, the blo...