A new method for nanomolar determination of silicic acid in seawater.

A novel method is proposed to determine concentrations of silicic acid in seawater in the nanomolar range of 3-500 nM. It preconcentrates silicic acid through a "Magnesium Induced Co-precipitation" (MAGIC) step before a classical spectrophotometric measurement. The detection limit (3+/-2 nM) is improved by a factor 10 in comparison to the conventional colorimetric methods. The best precision obtained to date is +/-2 nM for a natural sample of 69 nM Si. No interference of phosphate was observed by contrast to previous methods. This simple method offers a simple, sensitive and accurate tool for silicic acid determination in depleted seawater, where its availability remains unknown.

A study of the alumina-silica gel adsorbent for the removal of silicic acid from geothermal water: increase in adsorption capacity of the adsorbent due to formation of amorphous aluminosilicate by adsorption of silicic acid.

Two kinds of adsorbents (Si adsorbent and Al adsorbent) for the removal of silicic acid from geothermal water to retard the formation of silica scales were prepared using silicic acid contained in geothermal water. The Si adsorbent was prepared by evaporating geothermal water, and the Al adsorbent was prepared by evaporating geothermal water after the addition of aluminum chloride. The specific surface area of the Si adsorbent was small and it's adsorption capacity of silicic acid was low. Although the specific surface area of the Al adsorbent was also small, it was significantly increased by the adsorption of silicic acid and it's adsorption capacity was high. Based on the change in the local structure of aluminum ion by the adsorption of silicic acid, the Al adsorbent was considered to be silica particles covered with crystalline aluminum hydroxide. Moreover, it was concluded that the increase in the specific surface area of the Al adsorbent and the decrease in the zeta potential were due to the formation of an amorphous aluminosilicate with a large surface area and a negative charge (one 4-coordinated Al) by the reaction between aluminum ions and silicic acids.

Mechanism of silicate binding to the bacterial cell wall in Bacillus subtilis.

To investigate the chemical mechanism of silicate binding to the surface of Bacillus subtilis, we chemically modified cell wall carboxylates to reverse their charge by the addition of an ethylenediamine ligand. For up to 9 weeks, mixtures of Si, Al-Fe-Si, and Al-Fe-Si plus toxic heavy metals were reacted with these cells for comparison with control cells and abiotic solutions. In general, more Si and less metal were bound to the chemically modified surfaces, thereby showing the importance of an electropositive charge in cell walls for fine-grain silicate mineral development. The predominant reaction for this development was the initial silicate-to-amine complexation in the peptidoglycan of ethylenediamine-modified and control cell walls, although metal ion bridging between electronegative sites and silicate had an additive effect. The binding of silicate to these bacterial surfaces can thus be described as outer sphere complex formation because it occurs through electrostatic interaction.

Isolation of silicate ionophore(s) from the apochlorotic diatom Nitzschia alba.

An organic extract of Nitzschia alba cells possesses ionophoretic activity towards silicate, as it induces silicate transport across an organic phase or across synthetic lipid membranes. The activity is dependent upon Na+ and prefers silicon to germanium, a congener. The activity can be resolved into two apparently pure fractions by a combination of high performance liquid chromatography and thin-layer chromatography. Preliminary characterization indicates that the compound(s) contains vicinal hydroxyl groups but is devoid of amino, sugar or phosphate groups.

The structure of a new sialic acid-containing decasaccharide from the urine of a patient with mucolipidosis.

A new sialic acid-containing oligosaccharide has been isolated from urine of a patient with a type of mucolipidosis newly recognized by Orii et al. (1972). This compound was found to be composed of galactose (2 moles), mannose (3 moles), N-acetylglucosamine (3 moles) and sialic acid (2 moles). On the basis of the results of sequential glycosidase digestion, of methylation analysis, and of the Smith degradation, the structure of this oligosaccharide was elucidated as follows: NeuAcalpha2-6Galbeta1-4GlcNAcbeta1-2Manalpha1-3[NeuAcalpha2-6Galbeta1-4GlcNAcbeta1-2Manalpha1-6]Manbeta1-4GlcNAc. The increased excretion of this oligosaccharide may be caused by the impaired metabolism of glycoproteins having N-glycosidic linkage.