The role of surface hydroxyls on the radiolysis of gibbsite and boehmite nanoplatelets.

Understanding mechanistic pathways to radiolytic hydrogen generation by metal oxyhydroxide nanomaterials is challenging because of the difficulties of distinguishing key locations of OH bond scission, from structural interiors to hydroxylated surfaces to physi-sorbed water molecules. Here we exploited the interface-selectivity of vibrational sum frequency generation (VSFG) to isolate surface versus bulk hydroxyl groups for gibbsite and boehmite nanoplatelets before and after 60Co irradiation at dose levels of approximately 7.0 and 29.6 Mrad. While high-resolution microscopy revealed no effect on particle bulk and surface structures, VSFG results clearly indicated up to 83% and 94% radiation-induced surface OH bond scission for gibbsite and boehmite, respectively, a substantially higher proportion than observed for interior OH groups by IR and Raman spectroscopy. Electron paramagnetic spectroscopy revealed that the major radiolysis products bound in the mineral structures are trapped electrons, O, O2- and possibly F-centers in gibbsite, and H, O and O3- in boehmite, which persist on the time frame of several months. The entrapped radiolysis products appear to be highly stable, enduring re-hydration of particle surfaces, and likely reflect a permanent adjustment in the thermodynamic stabilities of these nanomaterials.

Improved deposition and deprotection of silane tethered 3,4 hydroxypyridinone (HOPO) ligands on functionalized nanoporous silica.

An improved synthesis of a 3,4 hydroxypyridinone (HOPO) functionalized mesoporous silica is described. Higher 3,4-HOPO monolayer ligand loadings have been achieved, resulting in better performance. Performance improvements were demonstrated with the capture of U(VI) from human blood, plasma and filtered river water.

Chloromethylated Activated Carbon: A Useful New Synthon for Making a Novel Class of Sorbents for Heavy Metal Separations.

The chloromethylation of activated carbon is described. Chloromethylation was found to produce a carbon derivative with a surface area of 1310 m(2)/g and no significant change in the pore structure. The product was found to contain ~1.5 mmole of -CH(2)Cl groups per g of material, similar to the functional density reported in the original Merrifield resin synthesis. Displacement of the benzylic chloride was achieved by treating this material with an excess of sodium thiosulfate in refluxing aqueous methanol. The resulting Bunte salt was then hydrolyzed by treatment with warm 3 M HCl to afford the corresponding thiol ("AC-CH(2)-SH") cleanly and in high yield. AC-CH(2)-SH was found to be an effective heavy metal sorbent, efficiently capturing Hg, Pb, Ag, and Cu. Sorption kinetics were rapid, with equilibrium achieved in less than 30 minutes.

Circulating and luminal testicular factors affect LRP-2 and Apo J expression in the epididymis following efferent duct ligation.

Apolipoprotein J (clusterin or sulfated glycoprotein-2) has been shown to be secreted by the epididymal principal cells, whereupon it binds to sperm in the lumen. Apolipoprotein J also is endocytosed by principal cells along the epididymis. Recently, it has been demonstrated that low-density lipoprotein receptor-related protein-2 (LRP-2) mediates the endocytosis of Apo J and is present in the epididymis. The purpose of the present study was to determine the factors regulating the synthesis of these 2 proteins in various experimentally treated animals. The epididymides of adult rats were fixed with Bouin's fluid and examined with anti-Apo J and anti-LRP-2 antibodies by a light microscope immunocytochemical method. In normal adult animals, expression of Apo J was evident in principal cells of all epididymal regions except the proximal initial segment. Diffuse cytoplasmic staining indicated Apo J secretion. Reactive apical vesicles, presumably endosomal in nature, suggested endocytosis of Apo J. Lipoprotein receptor-related protein-2 expression was solely apical in nature and was seen as an intense apical band in principal cells of all regions except the proximal and distal initial segment and distal caput regions of the epididymis. Hypophysectomy, up to 28 days after the procedure, did not affect expression of Apo J or LRP-2 in principal cells along the entire epididymis. Orchidectomy, with or without testosterone replacement at all time intervals examined, also did not affect LRP-2 expression along the entire epididymis. This also was noted for Apo J expression in all regions except the proximal initial segment. Thus, expression of these 2 proteins does not appear to be regulated by testicular or pituitary factors. In contrast, bilateral as well as unilateral (intact and ligated sides) efferent duct ligation resulted in dramatic differences in LRP-2 and Apo J expression in principal cells in the various epididymal regions. In the case of LRP-2, a complete absence of reaction was noted in principal cells along the entire epididymis. As for Apo J, expression in the distal initial segment, intermediate zone, and caput region remained unchanged compared with that in normal adult animals, whereas in the corpus and cauda epididymides, results of cytoplasmic staining were negligible. These results suggest that under conditions of efferent duct ligation, a circulating factor emanates from the testis to inhibit expression of LRP-2 and Apo J in these epididymal regions. Furthermore, because Apo J was affected in a region-specific manner, unlike the case for LRP-2, different factors appear to be involved for each protein. These factors may be produced to inhibit proteins from being synthesized by the epididymis in the absence of luminal testicular input and may exist in cases of congenital and pathologic epididymal tubule blockages as well as after vasectomy. In the case of immunostaining for Apo J in the proximal initial segment only, normally unreactive principal cells in control adult animals became intensely reactive after orchidectomy as well as bilateral and unilateral (ligated side only) ligation. As this was not the case for hypophysectomized animals and the intact side of unilateral efferent duct-ligated animals, it is suggested that a testicular factor entering via the lumen of the efferent ducts serves to inhibit Apo J expression in this area. The present data also reveal that after efferent duct ligation, there are circulating factors that inhibit Apo J expression in a region-specific manner (corpus and cauda) and that inhibit LRP-2 expression along the entire epididymis and that these are derived from the testis. Furthermore, the data reveal that a testicular luminal factor appears to inhibit Apo J expression in the proximal initial segment of normal adult animals. Key words: Principal cells, orchidectomy, glycoprotein 330, clusterin, sulfated glycoprotein-2.