Simple synthesis methods for mesoporous fibers and powders by rapid evaporation of hydrolyzed silicon alkoxide−surfactant solutions are described. Mesoporous fibers are prepared by dry spinning, and mesoporous powders by spray drying of alkoxide−surfactant solutions. Precursor solutions, containing fully hydrolyzed tetraethoxysilane, cetyltrimethylammonium chloride surfactant, and, in the case of the fibers, a fiber-forming polymer, in an acidic alcohol/water mixture, are drawn into continuous filaments or atomized into droplets in a heated air stream. During solvent drying, silica and surfactant self-assemble to form the hexagonally ordered mesophase structure, and all of the nonvolatile components (silica, polymer, and surfactant) are incorporated into the mesophase. The pore diameter and surface area of calcined fibers were 20 Å and 1100 m2/g, respectively. For the powders, pore sizes of 25 Å and surface areas as high as 1770 m2/g were measured. Spray-dried powders consisting of hollow spherical particles with mesoporous shells were also produced with this approach.

Resident late-Golgi membrane proteins in Saccharomyces cerevisiae are selectively retrieved from a prevacuolar–endosomal compartment, a process dependent on aromatic amino acid–based sorting determinants on their cytosolic domains. The formation of retrograde vesicles from the prevacuolar compartment and the selective recruitment of vesicular cargo are thought to be mediated by a peripheral membrane retromer protein complex. We previously described mutations in one of the retromer subunit proteins, Vps35p, which caused cargo-specific defects in retrieval. By genetic and biochemical means we now show that Vps35p directly associates with the cytosolic domains of cargo proteins. Chemical cross-linking, followed by coimmunoprecipitation, demonstrated that Vps35p interacts with the cytosolic domain of A-ALP, a model late-Golgi membrane protein, in a retrieval signal–dependent manner. Furthermore, mutations in the cytosolic domains of A-ALP and another cargo protein, Vps10p, were identified that suppressed cargo-specific mutations in Vps35p but did not suppress the retrieval defects of a vps35 null mutation. Suppression was shown to be due to an improvement in protein sorting at the prevacuolar compartment. These data strongly support a model in which Vps35p acts as a “receptor” protein for recognition of the retrieval signal domains of cargo proteins during their recruitment into retrograde vesicles.

Resident membrane proteins of the trans-Golgi network (TGN) of Saccharomyces cerevisiae are selectively retrieved from a prevacuolar/late endosomal compartment. Proper cycling of the carboxypeptidase Y receptor Vps10p between the TGN and prevacuolar compartment depends on Vps35p, a hydrophilic peripheral membrane protein. In this study we use a temperature-sensitive vps35 allele to show that loss of Vps35p function rapidly leads to mislocalization of A-ALP, a model TGN membrane protein, to the vacuole. Vps35p is required for the prevacuolar compartment-to-TGN transport of both A-ALP and Vps10p. This was demonstrated by phenotypic analysis of vps35 mutant strains expressing A-ALP mutants lacking either the retrieval or static retention signals and by an assay for prevacuolar compartment-to-TGN transport. A novel vps35 allele was identified that was defective for retrieval of A-ALP but functional for retrieval of Vps10p. Moreover, several other vps35 alleles were identified with the opposite characteristics: they were defective for Vps10p retrieval but near normal for A-ALP localization. These data suggest a model in which distinct structural features within Vps35p are required for associating with the cytosolic domains of each cargo protein during the retrieval process.

The yeast COG complex has been proposed to function as a vesicle-tethering complex on an early Golgi compartment, but its role is not fully understood. COG complex mutants exhibit a dramatic reduction in Golgi-specific glycosylation and other defects. Here we show that a strain carrying a COG3 temperature-sensitive allele,

Low dielectric-constant mesoporous silica films were prepared by condensation of a silicate network around surfactant micellar structures. Adherent, porous films 0.5–1.0 μm in thickness, and containing an ordered assemblage of ≈2 nm diameter pores were synthesized by spin-coating water/ethanol-based solutions containing a silica precursor and surfactant template. In this paper, film deposition conditions are described, and film thickness, porosity, refractive index and dielectric constant measured by ellipsometry are presented. Using a coating solution containing tetraethyl orthosilicate (TEOS) and a cationic cetyltrimethylammonium chloride (CTAC) surfactant template, the film porosity and dielectric properties were controlled over a wide range by adjusting the CTAC/TEOS molar ratio. With the CTAC/TEOS ratio between 0.1 and 0.15, the pores were highly ordered in hexagonal arrays after heat treatment at 550 °C. With a CTAC/TEOS ratio of 0.21, films with a pore volume of ≈64% (≈36 vol% silica) could be synthesized. The measured index of refraction for these highly porous films at 500 nm wavelength was 1.16, indicating that these films are potentially useful as low K interlayer dielectrics.