Chs6p-dependent anterograde transport of Chs3p from the chitosome to the plasma membrane in Saccharomyces cerevisiae

Chitin synthase III (CSIII), an enzyme required to form a chitin ring in the nascent division septum of Saccharomyces cerevisiae, may be transported to the cell surface in a regulated manner. Chs3p, the catalytic subunit of CSIII, requires the product of CHS6 to be transported to or activated at the cell surface. We find that chs6Delta strains have morphological abnormalities similar to those of chs3 mutants. Subcellular fractionation and indirect immunofluorescence indicate that Chs3p distribution is altered in chs6 mutant cells. Order-of-function experiments using end4-1 (endocytosis-defective) and chs6 mutants indicate that Chs6p is required for anterograde transport of Chs3p from an internal endosome-like membrane compartment, the chitosome, to the plasma membrane. As a result, chs6 strains accumulate Chs3p in chitosomes. Chs1p, a distinct chitin synthase that acts during or after cell separation, is transported normally in chs6 mutants, suggesting that Chs1p and Chs3p are independently packaged during protein transport through the late secretory pathway.

Preparation and stabilization of heparin/gelatin complex coacervate microcapsules

The aims of this study are to optimize conditions for the preparation, stabilization, and harvesting of heparin/gelatin microcapsules prepared by complex coacervation. Microelectrophoresis and dry coacervate weight were used to determine the optimum conditions of pH and ionic strength for maximum heparin/gelatin coacervate yield. Heparin/gelatin microcapsules were formed by complex coacervation in the presence and absence of poly(1-vinyl-2-pyrrolidone) (PVP), which was used as a stabilizer. The microcapsules were collected using a spray-drying technique. Microcapsule particle size was analyzed using an AccuSizer optical sizer. Optimized conditions for maximum coacervate yield were pH 2.6, ionic strength 10 mM, and a 1:2 heparin/gelatin A ratio. PVP stabilized the heparin/gelatin coacervate droplets and reduced droplet aggregation during spray-drying. The mean particle diameter of the spray-dried coacervate droplets was lower in the presence of PVP and was unaffected by PVP concentration (in the range 0.5-2.0% w/w). Heparin/gelatin microcapsules, prepared under conditions optimized for maximum coacervate yield, were stabilized without the use of chemical cross-linking agents. Stabilization was achieved by a combination of the addition of PVP and spray-drying.