We present an atomic lattice model for studying the polymerization of silicic acid in sol-gel and related processes for synthesizing silica materials. Our model is based on Si and O atoms occupying the sites of a body-centered-cubic lattice, with all atoms arranged in SiO(4) tetrahedra. This is the simplest model that allows for variation in the Si-O-Si angle, which is largely responsible for t...

Natural systems excel in directing the synthesis of inorganic materials for various functional purposes. One of the best-studied systems is silica synthesis, as occurs in diatoms and marine sponges. Various biological and synthetic polymers have been shown to template and catalyze silica formation from silicic acid precursors. Here, we describe the use of poly-L-lysine to promote the synthesis ...

We describe a new, rapid, and simple column-chromatographic procedure for 25-OH vitamin D3 in plasma. The vitamin is extracted by use of Sep-pak C18 (octadecyl alkylated silicic acid), a short factory-packed reversed-phase column, and 25-OH vitamin D2 + 25-OH vitamin D3 fraction is eluted with methanol/water. The 25-OH D2 and 25-OH D3 are then well resolved on a high-resolution 3-micrometer sil...

Previous studies from this laboratory revealed that phosphatidyl serine (PS) isolated from plate-let phospholipid extracts by silicic-acid column chromatography could replace blood platelets in tests of thromboplastin generation and prothrom-bin consumption of platelet-poor "native" plasma (1, 2). When rigorous criteria of identification were employed, it was found that phosphatidyl ethanolamin...

Mycobacterium avium accumulates (14)C-palmitic acid with saturation kinetics; the process is both temperature dependent and pH sensitive. The fatty acid is incorporated into triglyceride in vivo and the conversion is detectable within 5 min after exposure of the cells to (14)C-palmitic acid. The triglyceride is rapidly utilized because (14)CO(2) evolution from it begins within 30 min after (14)...

Ocean circulation is a remarkable interconnecting conduit, such that biological processes occurring in the remote Southern Ocean can influence the regulation of productivity in Northern Hemisphere waters. Marine phytoplankton, despite their small size, play a disproportionately important role in setting the stoichiometric relationship between elements such as nitrogen, phosphorus, carbon and si...

A three-step procedure has been developed for the separation of complex mixtures of sterol intermediates in cholesterol biosynthesis. The method has been applied to the separation of sterol intermediates formed from [14C]mevalonate by normal rat hepatocyte culture cells. In Step 1, a short gravity-flow silicic acid column (1.2 x 6.5 cm) separates the incubation products into four classes consis...

In spring/summer 2015, a toxic bloom by the diatom Pseudo-nitzschia (PN) occurred along the west coast of the United States which led to closures of the harvest of razor clams and Dungeness crabs. Twice monthly observations of temperature, salinity, nutrients, chlorophyll and phytoplankton species composition allowed us to track oceanographic conditions preceding and during the development of t...