Arsenic Speciation on Silver Nanofilms by Surface-Enhanced Raman Spectroscopy.

Surface-enhanced Raman spectroscopy (SERS), as a nondestructive and fast detection technique, is a promising alternative approach for arsenic detection, particularly for in situ applications. SERS-based speciation analysis according to the fingerprint SERS signals of different arsenicals has the potential to provide a superior technique in species preservation over the conventional chromatographic separation methods, albeit with some difficulties due to the similarity in SERS patterns. In this study, we explored a novel SERS method for arsenic speciation by using the separation potential of the coffee ring effect on negatively charged silver nanofilms (AgNFs). Four arsenic species, including arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMAV), and dimethylarsinic acid (DMAV), were measured for fingerprint SERS signals in solution and on the films. Significant enhancement of SERS signals on the dried coffee ring stains by the AgNFs were observed except for AsIII, and more importantly, arsenicals migrated varying distances during coffee ring development, promoting better speciation. Sodium dodecyl sulfate was then introduced into the droplet to reduce the droplet surface tension, facilitating the migration of solution into the peripheral region. Under the combined interactions of arsenicals with the AgNFs, solvent, and surfactant, enhanced separation between arsenicals was observed as a result of the formation of two concentric rings. Combining the SERS fingerprint signals and physical separation of arsenicals on the surface, arsenic speciation was achieved using the AgNFs substrate-based SERS technology, demonstrating the potential of the coffee ring effect for rapid separation and analysis of small molecules by SERS.

Novel GPIHBP1-independent pathway for clearance of plasma TGs in Angptl4-/-Gpihbp1-/- mice.

Mice lacking glycosylphosphatidylinositol-anchored HDL-binding protein 1 (GPIHBP1) are unable to traffic LPL to the vascular lumen. Thus, triglyceride (TG) clearance is severely blunted, and mice are extremely hypertriglyceridemic. Paradoxically, mice lacking both GPIHBP1 and the LPL regulator, angiopoietin-like 4 (ANGPTL4), are far less hypertriglyceridemic. We sought to determine the mechanism by which Angptl4-/-Gpihbp1-/- double-knockout mice clear plasma TGs. We confirmed that, on a normal chow diet, plasma TG levels were lower in Angptl4-/-Gpihbp1-/- mice than in Gpihbp1-/- mice; however, the difference disappeared with administration of a high-fat diet. Although LPL remained mislocalized in double-knockout mice, plasma TG clearance in brown adipose tissue (BAT) increased compared with Gpihbp1-/- mice. Whole lipoprotein uptake was observed in the BAT of both Gpihbp1-/- and Angptl4-/-Gpihbp1-/- mice, but BAT lipase activity was significantly higher in the double-knockout mice. We conclude that Angptl4-/-Gpihbp1-/- mice clear plasma TGs primarily through a slow and noncanonical pathway that includes the uptake of whole lipoprotein particles.

The conformation of the histone H3 tail inhibits association of the BPTF PHD finger with the nucleosome.

Histone tails harbor a plethora of post-translational modifications that direct the function of chromatin regulators, which recognize them through effector domains. Effector domain/histone interactions have been broadly studied, but largely using peptide fragments of histone tails. Here, we extend these studies into the nucleosome context and find that the conformation adopted by the histone H3 tails is inhibitory to BPTF PHD finger binding. Using NMR spectroscopy and MD simulations, we show that the H3 tails interact robustly but dynamically with nucleosomal DNA, substantially reducing PHD finger association. Altering the electrostatics of the H3 tail via modification or mutation increases accessibility to the PHD finger, indicating that PTM crosstalk can regulate effector domain binding by altering nucleosome conformation. Together, our results demonstrate that the nucleosome context has a dramatic impact on signaling events at the histone tails, and highlights the importance of studying histone binding in the context of the nucleosome.

Angiopoietin-like 4 directs uptake of dietary fat away from adipose during fasting.

OBJECTIVE: Angiopoietin-like 4 (ANGPTL4) is a fasting-induced inhibitor of lipoprotein lipase (LPL) and a regulator of plasma triglyceride metabolism. Here, we examined the kinetics of Angptl4 induction and tested the hypothesis that ANGPTL4 functions physiologically to reduce triglyceride delivery to adipose tissue during nutrient deprivation. METHODS: Gene expression, LPL activity, and triglyceride uptake were examined in fasted and fed wild-type and Angptl4-/- mice. RESULTS: Angptl4 was strongly induced early in fasting, and this induction was suppressed in mice with access to food during the light cycle. Fasted Angptl4-/- mice manifested increased LPL activity and triglyceride uptake in adipose tissue compared to wild-type mice. CONCLUSIONS: Angptl4 is induced early in fasting to divert uptake of fatty acids and triglycerides away from adipose tissues.