Aluminum hydroxide adjuvant produced under constant reactant concentration.

Aluminum hydroxide adjuvant, AlO(OH), is used to potentiate the immune response to vaccines by adsorbing the antigen. The structure of aluminum hydroxide adjuvant is unusual as it is crystalline but has a high surface area due to its very small primary particles. The purpose of this study was to investigate the chemical and thermal conditions required to synthesize aluminum hydroxide adjuvant that is stable and exhibits a high protein adsorptive capacity. Aluminum hydroxide adjuvant was precipitated using a procedure in which the concentration of reactants was maintained constant throughout the precipitation. The precipitation variables were: 2.50, 2.75, and 3.00 OH/Al molar ratio; 0.5, 4.0, and 5.0 M NaCl; and 25, 60, and 65 degrees C. High sodium chloride concentration and high temperature facilitated the formation of AlO(OH) rather than crystalline forms of aluminum hydroxide, Al(OH)(3). The AlO(OH) produced was not stable because crystalline forms of aluminum hydroxide formed during aging at room temperature. Aluminum hydroxide adjuvant was stabilized for the study period of 12 weeks at room temperature by either the addition of 3.0 M NaCl after precipitation and washing or hydrothermal treatment at 110 degrees C for 4 h. Stabilization by the addition of sodium chloride required a hypertonic concentration of sodium chloride and was not practical as vaccines for parenteral administration are desired to be isotonic (equivalent to 0.15 M NaCl). Stabilization by hydrothermal treatment produced aluminum hydroxide adjuvant, which exhibited a high protein adsorptive capacity that did not change during the 12-week study period.

Evidence of a Multicopper Oxidase in Mn Oxidation by Gaeumannomyces graminis var. tritici.

ABSTRACT Manganese (Mn) oxidation by the plant-pathogenic fungus Gaeumannomyces graminis var. tritici has been correlated with virulence in take-all disease. The mechanism of Mn oxidation has not, however, been investigated adequately. Research on bacteria and other fungi indicates that Mn oxidation is most often the result of the activity of multicopper oxidases. To determine if G. graminis var. tritici oxidizes Mn by similar means, the Mn oxidizing factor (MOF) produced by G. graminis var. tritici was characterized by cultural, spectrophotometric, and cellulose acetate electrophoresis methods. Based on our results, the MOF is an extracellular enzyme with an estimated molecular weight of 50 to 100 kDa. Electrophoresis and spectrophotometry indicate that the MOF is a multicopper oxidase with laccase activity.

Fungal manganese oxidation in a reduced soil.

Manganese chemistry in soils is a function of complex, competing biotic and abiotic reactions. The role of soil-borne fungi in mediating these reactions is poorly understood. The objective of this article is to document direct observation of fungal Mn oxidation in soil under near in situ conditions, and to isolate, describe and confirm the role of fungi in the observed Mn oxidation, and present a model to explain our observations. We incubated soil under different moisture contents in sample cells designed to allow us to use synchrotron microspectroscopic techniques to analyse areas as small as 38x40 microm2. Mn was redistributed and accumulated in distinct small circular shapes or in dendritic patterns near the air-soil interface when water-saturated soil was incubated for >or=7 days. Mn oxidation did not occur at 3 or 52 degrees C indicating that oxidation was caused by microbial activity. Mn-oxidizing fungi were isolated from the sample cells and cultured on agar. Reinoculation of sterile soil with the Mn-oxidizing isolates resulted in the formation of Mn oxides around fungal hyphae. A model to describe the distinct zonal distribution of Mn oxides in the sample cells is presented. We believe that our data are the first direct observation of Mn oxidation by soil-inhabiting fungi under in situ conditions. Mn-oxidizing fungi may play an underappreciated role in the cycling of Mn in soils.

Role of soil manganese in the oxidation of aromatic amines.

Soil-induced oxidation and subsequent polymerization of aromatic amines is an important pathway for reducing the mobility of amines in soils and their hazard potential in the environment. This study assesses the hypothesis that manganese(III/IV) oxides/hydroxides play a significant role in the oxidation of aromatic amines in whole soils. Aromatic amines including alpha-naphthylamine, p-methoxyaniline, and aniline were allowed to react in aqueous whole soil suspensions for 5 d. Irreversible binding and/or transformation of amines were estimated using a rigorous extraction method and extractable transformation products were analyzed by matrix-assisted laser desorption/ ionization mass spectrometry. The Mn speciation shifts in the soil residue after amine-soil reactions were measured using a successive fractionation method and in-situ using X-ray absorption near-edge structure spectroscopy. A fraction of each of the three amines became irreversibly sorbed, and a large polymer formation was observed for alpha-naphthylamine and p-methoxyaniline. The increase in the irreversibly sorbed/transformed amine fraction over time was concomitant with the reduction of Mn(III/IV) to Mn(II), although oxidation by Mn(III/IV) was not sufficient to account for all amine irreversibly lost. Oxidation by soil Mn did contribute to immobilizing amines within organic matter and to the formation of large aromatic amine polymers, which serves to reduce mobility and bioavailability of aromatic amines in the natural environment.

A technique for cutting brittle undisturbed lateritic soil block samples.

This note describes a technique for cutting undisturbed brittle block samples into smaller specimens for further geotechnical testing. This technique revealed very useful in dealing with collapsible soils, where the sampling is recommended to be done with block soil samples. A further use of this technique as an efficient way for sampling collapsible soils is proposed.