Poly(styrene-co-acrylonitrile) Particles Prepared by Phase Inversion of W/O Emulsions.

In this paper, we describe a particle preparation method that combines phase inversion of water in oil (W/O) emulsions with solidification of polymers dissolved in the emulsion droplets, induced by introducing a poor solvent, in order to prepare poly(styrene-co-acrylonitrile) (SAN) particles with a relatively narrow size distribution. W/O emulsions containing SAN are prepared by adding an aqueous solution of polyvinylalcohol (PVA) as a protective colloid into a methylethylketone (MEK) solution of SAN. Sufficient addition of the aqueous solution causes the precipitation of SAN particles from MEK followed by phase inversion from W/O emulsions to oil in water (O/W) emulsions. We also demonstrate that the use of sorbitan fatty acid esters as dispersion agents is effective for controlling size and polydispersity of SAN particles. They depend strongly on the concentrations and kinds of sorbitan fatty acid esters; a low concentration of sorbitan monolaurate resulted in an average particle size of 1.2 µm with a narrow size distribution.

A novel chalcone polyphenol inhibits the deacetylase activity of SIRT1 and cell growth in HEK293T cells.

SIRT1 is one of seven mammalian orthologs of yeast silent information regulator 2 (Sir2), and it functions as a nicotinamide adenine dinucleotide (NAD)-dependent deacetylase. Recently, resveratrol and its analogues, which are polyphenols, have been reported to activate the deacetylase activity of SIRT1 in an in vitro assay and to expand the life-span of several species through Sir2 and the orthologs. To find activators or inhibitors to SIRT1, we examined thirty-six polyphenols, including stilbenes, chalcones, flavanones, and flavonols, with the SIRT1 deacetylase activity assay using the acetylated peptide of p53 as a substrate. The results showed that 3,2',3',4'-tetrahydroxychalcone, a newly synthesized compound, inhibited the SIRT1-mediated deacetylation of a p53 acetylated peptide and recombinant protein in vitro. In addition, this agent induced the hyperacetylation of endogenous p53, increased the endogenous p21CIP1/WAF1 in intact cells, and suppressed the cell growth. These results indicated that 3,2',3',4'-tetrahydroxychalcone had a stronger inhibitory effect on the SIRT1-pathway than sirtinol, a known SIRT1-inhibitor. Our results mean that 3,2',3',4'-tetrahydroxychalcone is a novel inhibitor of SIRT1 and produces physiological effects on organisms probably through inhibiting the deacetylation by SIRT1.