Recovery and sporicidal resistance of various B. subtilis spore preparations on porcelain penicylinders compared with results from AOAC test methods

Sporicidal test results obtained from carriers inoculated with 4 types of defined Bacillus subtilis spore preparations were compared with the standard AOAC sporicidal test using soil extract nutrient broth (SENB) B. subtilis 19659 spores. Recoveries of spores inoculated on penicylinders from B. subtilis clean spores (washed and suspended in water) and B. subtilis 19659 spores inoculated from culture filtrates according to the AOAC method were compared. Spores were exposed to 6 concentrations (0.5-3.0% w/v) of glutaraldehyde in phosphate buffer (pH 7.5) for 10 h. Concentrations were established by titrimetry and liquid chromatography. Recoveries of surviving spores were determined for 3 types of clean B. subtilis var. niger preparations, one clean B. subtilis 19659 preparation, and the SENB B. subtilis 19659 filtrates. Spore carriers, inoculated by the standard AOAC protocol, resulted in as much as a 2-log number difference in runs 1-12, but not more than 0.5 log number for each clean spore preparation. The SENB spores varied most in resistance to glutaraldehyde, with no growth in recovery media from 3 different batches of 1, 1.5, and 2% glutaraldehyde. Separate batches of SENB preparations of B. subtilis 19659 were resistant and destroyed by 1.0% glutaraldehyde, with 3.98 and 6.0 log numbers of spores on penicylinders, respectively. Clean spore preparations of B. subtilis 19659 on porcelain penicylinders were more resistant to glutaraldehyde than were SENB spores. Nutrient agar/Mg/Ca and nutrient agar/Mg spore preparations of B. subtilis var. niger showed the most uniform resistance to glutaraldehyde. Spores with calcium added showed increased resistance to glutaraldehyde. B. subtilis 19659 spores from the Columbia broth spore preparation were the most resistant and were recovered after exposure to 3.0% glutaraldehyde.     

The theory of non-Cottrellian diffusion on the surface of a sphere or truncated sphere.

A method is developed whereby spherical and other particles can be derivatised with electroactive species on their surface and then immobilised on the surface of an electrode. The chronoamperometric and voltammetric responses in the limit of reversible electrode kinetics are modelled using a theory of charge movement over the surface of the spheres where this movement is considered as a diffusional process. The model is extended to include different distributions of sphere radii and to model the scenario of truncated spheres resting on the electrode surface. It is found that a good estimation of the truncation angle can be found by fitting the experimental data with theoretical predictions.     

Viscoelastic properties of single poly(ethylene glycol) molecules.

The viscoelastic properties of single poly(ethylene glycol) (PEG) molecules were measured by analysis of thermally and magnetically driven oscillations of an atomic force microscope (AFM) cantilever/molecule system. The molecular and monomer stiffness and friction of the PEG polymer were derived using a simple harmonic oscillator (SHO) model. Excellent agreement between the values of these two parameters obtained by the two approaches indicates the validity of the SHO model under the experimental regimes and the excellent reproducibility of the techniques. A sharp minimum in the monomeric friction is seen at around 180 pN applied force which we propose is due to a force induced change in the shape of the energy landscape describing the conformational transition of PEG from a helical to a planar state, which in turn affects the timescale of the transition and therefore modifies the measured internal friction. A knowledge of the viscoelastic response of PEG monomers is particularly important since PEG is widely used as a linker molecule for tethering groups of interest to the AFM tip in force spectroscopy experiments, and we show here that care must be exercised because of the force-dependent viscoelastic properties of these linkers.     

Substitution-Inert Metal Complex Mobile Phases in Non-Suppressed Cation Chromatography

Substitution-inert metal complexes, [Co(edda)(H₂O)₂]⁺, (Co(edda)(en)]⁺, [Co(edda)(dmen)]⁺, [Co(en)₂-(gly)]²⁺, [Co(en)₂(acac)]²⁺, and [Co(trien)(gly)]²⁺ in their nitrate salt solutions are used as eluents in nonsuppressed cation chromatography (where edda = ethylenediamine-N,N′-diacetic acid, en = ethylenediamine, dmen = N,N′-dime-thylethylenediamine, gly = glycine, acac = acetylacetone, and trien = triethylenetetraamine). It is found that all the mono- and di-valent charged complexes can be used to separate alkali and alkaline earth metal cations, respectively. The separations for monovalent cations are sometimes comparable to those using ultrapure HNO₃ solutions. However, the divalent Ca²⁺ and Sr²⁺ ions cannot be resolved using the metal complex eluents. On the other hand, a selected, direct non-suppressed IC separation of zinc(II) and cadmium(II) ions is demonstrated for the first time using a substitution-inert metal complex eluent and a conductivity detector. Comparisons of these eluents with those reported previously, i. e. HNO₃ and ethylenediammonium salt solution are made and explanations are proposed to account for the different selectivities observed where possible. The future development of this technique is also briefly discussed.     

Dinuclear zinc(II) double-helicates of homochirally substituted bis(dipyrromethene)s

[structure: see text] A series of bis(dipyrromethene)s substituted with aromatic amide and aliphatic ester homochiral auxiliaries have been prepared and complexed with zinc(II) ions to form double-helical dinuclear complexes. CD analysis of the crude complexes revealed that the helicates formed in a diastereoselective manner. The helicates have been resolved into their constituent M and P helices by HPLC, indicating that the helical sense of the complexes is stable to racemization.     

Synthesis of some pyridylamino-1,4-disubstituted phthalazines

Two general procedures involving the condensation of phthalonitrile or 1,3-diiminoisoindoline with various aminopicolines, followed by ring expansion with hydrazine to the corresponding phthalazine are described. Syntheses are reported of 1, 4-di(3′-methyl-2′-pyridyl) aminophthalazine, 1,4-di(5′-methyl-2′-pyridyl)aminophthalazine, and 1,4-di(4′, 6′-dimethyl-2′-pyridyl)aminophthalazine.     

Improving splitless injection with electronic pressure programming

An experimental injection port has been designed for split or splitless sample introduction in capillary gas chromatography; the inlet uses electronic pressure control, in order that the column head pressure may be set from the GC keyboard, and the inlet may be used in the constant flow or constant pressure modes. Alternatively, the column head pressure may be programmed up or down during a GC run in a manner analogous to even temperature programming. Using electronic pressure control, a method was developed which used high column head pressures (high column flow rates) at the time of injection, followed by rapid reduction of the pressure to that required for optimum GC separation. In this way, high flow rates could be used at the time of splitless injection to reduce sample discrimination, while lower flow rates could be used for the separation. Using this method, up to 5 μl of a test sample could be injected in the splitless mode with no discrimination; in another experiment, 2.3 times as much sample was introduced into the column by using electronic pressure programming. Some GC peak broadening was observed in the first experiment.     

Effects of high intensity ultrasound on inorganic solids

Ultrasonic irradiation dramatically affects the reactivity of a variety of inorganic solids. We have found, for example, large increases in the rates of intercalation of a wide range of compounds into various layered inorganic solids (such as ZrS2, V2O5, TaS2 and MoO3. High intensity ultrasound also enhances the heterogeneous catalysis of alkene hydrogenation by Ni powders. Scanning electron microscopy reveals that ultrasound has multiple effects on the morphology and surface characteristics of inorganic solids, creating substantial surface damage, increasing surface areas significantly and causing increased particle aggregation.     

Tuning the mesogenic properties of 5-alkoxy-2-(4-alkoxyphenyl)pyrimidine liquid crystals: the effect of a phenoxy end-group in two sterically equivalent series

Two sterically equivalent series of phenoxy-terminated 5-alkoxy-2-(4-alkoxyphenyl)pyrimidine liquid crystals were synthesised, and their mesogenic properties were characterised by polarised optical microscopy and differential scanning calorimetry (DSC). The phenoxy end-group causes a significant increase in melting point and inhibits – at least partially – the mesomorphism of these materials relative to the parent isomers; in most cases, the broad enantiotropic SmC phase formed by the parent isomers is suppressed by the addition of the phenoxy end-group. However, detailed analyses by small-angle X-ray scattering and monodomain 2D X-ray scattering suggest that these compounds form a SmA phase with a partially intercalated bilayer structure in which the phenoxy end-groups are nanosegregated. Such an intercalated bilayer structure might enable the tuning of smectogenic properties by appropriate substitution of the phenoxy end-groups.     

The Orion Water-Hardness Electrode: An Unexpected Response to Magnesium Ion

Abstract

The Orion water-hardness electrode, while being used to measure magnesium ion activity in a series of calcium-free solutions, displayed some unanticipated changes in potential. As the overall potential change observed for one solution was 183 mV (equivalent to more than six orders of magnitude changes in magnesium-ion activity), several precautions are suggested which should be observed when using this electrode for specific purposes. In particular, it is recommended that the exchanger be pre-equilibrated with an appropriate solution if the electrode is to be used in restricted systems of known chemical composition.