Influence of bovine serum albumin and alginate on silver nanoparticle dissolution and toxicity to Nitrosomonas europaea.

Bovine serum albumin (BSA), a model protein, reduced the toxicity of 20 nm citrate silver nanoparticles (AgNP) toward Nitrosomonas europaea, a model ammonia oxidizing bacteria, through a dual-mode protection mechanism. BSA reduced AgNP toxicity by chelating the silver ions (Ag(+)) released from the AgNPs. BSA further reduced AgNP toxicity by binding to the AgNP surface thus preventing NH3-dependent dissolution from occurring.

Influence of ammonia on silver nanoparticle dissolution and toxicity to Nitrosomonas europaea.

Nitrosomonas europaea, a model ammonia oxidizing bacterium, was sensitive to both ionic silver (Ag(+)) and 20 nm citrate capped silver nanoparticles (AgNPs). AgNP toxicity has been previously shown to be primarily due to the dissolution of Ag(+). The rate of AgNP dissolution dramatically increased in test medium containing ammonium sulfate ((NH4)2SO4) and HEPES buffer compared to test medium containing either deionized water or HEPES buffer alone.

Conformational defects slow Golgi exit, block oligomerization, and reduce raft affinity of caveolin-1 mutant proteins.

Caveolin-1, a structural protein of caveolae, is cleared unusually slowly from the Golgi apparatus during biosynthetic transport. Furthermore, several caveolin-1 mutant proteins accumulate in the Golgi apparatus. We examined this behavior further in this mutant study.

Role of the hydrophobic domain in targeting caveolin-1 to lipid droplets.

Although caveolins normally reside in caveolae, they can accumulate on the surface of cytoplasmic lipid droplets (LDs). Here, we first provided support for our model that overaccumulation of caveolins in the endoplasmic reticulum (ER) diverts the proteins to nascent LDs budding from the ER. Next, we found that a mutant H-Ras, present on the cytoplasmic surface of the ER but lacking a hydrophobic peptide domain, did not accumulate on LDs.

Caveolin-1 does not affect SR-BI-mediated cholesterol efflux or selective uptake of cholesteryl ester in two cell lines.

Free cholesterol (FC) has been reported to efflux from cells through caveolae, which are 50-100 nm plasma membrane pits. The 22 kDa protein caveolin-1 is concentrated in caveolae and is required for their formation. The HDL scavenger receptor BI (SR-BI), which stimulates both FC efflux and selective uptake of HDL-derived cholesteryl ester (CE), has been reported to be concentrated in caveolae, suggesting that this localization facilitates flux of FC and CE across the membrane.