Spontaneous recessive orthovanadateresistant mutants of Saccharomyces cerevisiae were obtained in five complementation groups, and all show defects in protein glycosylation that mimic the previously isolated mnn mutants. Three of the groups are allelic to the known mnn8, mnn9, and manlO mutants, whereas the other two groups show other glycosylation defects. The vanadate-resistant phenotype was associated with enhanced hygromycin B sensitivity. The glycosylation phenotypes of the mutants are all reflections of defects in glycoprotein trafficking, and the easy isolation of vanadate-resistant or hygromycin B-sensitive mutants should facilitate the study of this process.Orthovanadate-resistant mutants of Saccharomyces cerevisiae have been studied extensively by Willsky and coworkers (1-3), who identified at least five complementation groups with this phenotype. Considerable effort has been expended to define the site(s) of vanadate action in the sensitive cell and, thereby, provide a clue to the possible mechanism(s) by which vanadate resistance could arise (2, 4). Although a rather high concentration of vanadate (5 mM) is required to inhibit yeast growth, it is reported that the intracellular concentration is only about 0.1 mM (3). Since vanadate enters the cell by an active process (5), one mechanism for resistance could be a change in the transport system(s) that reduces uptake or enhances excretion. Alternatively, resistant cells could develop more effective detoxification mechanisms (2) or target site(s) could in some way become desensitized. Vanadate is known to inhibit enzymes of phosphate metabolism (2, 4), thereby affecting plasma membrane ion pumps and cytoplasmic motility (5), and it is expected that vanadate could affect processing, sorting, and secretion of macromolecules.It was recently found (R.A.H., C. Y. Chen, N. J. Simpson, and V. Chisholm, unpublished data) that the S. cerevisiae mnn9 mutant, which is defective in protein glycosylation (6), is remarkably resistant to orthovanadate and sensitive to hygromycin B, compared to the parent strain X2180. We have now analyzed a number of vanadate-resistant mutants to determine whether the glycosylation defect is a general property ofthis class. Ofthe five complementation groups we identified, all show defects in protein glycosylation and three of the groups are allelic with the previously characterized mnn8, mnn9, and mnnlO mutants (6). This result suggests that the primary sites of vanadate inhibition impinge directly on the processing of glycoproteins in the Golgi.MATERIALS AND METHODS Sodium orthovanadate, Na3VO4, was from Aldrich. Vanadate-containing plates were made by adding a freshly prepared filter-sterilized sodium orthovanadate solution to a melted sterilized agar medium, which was then poured into sterile Petri plates. Antisera that recognized the wild-type terminal al -3-linked mannose determinant and the unsubstituted al 6-linked mannose determinant of the mnn2 mutant outer chain came from laboratory stocks (7). The cell surface pheno...

The authors study the dissolution mechanism of hydrogen silsesquioxane in base solutions with the addition of chloride salts to elucidate the development mechanism. The reaction mechanisms are proposed based on the dissolution mechanism of quartz. Development kinetics suggests two dose-dependent development mechanisms. Considering ion sizes, both hydrated and nonhydrated, and ion exchange, they propose that a combination of a surface dominated reaction at higher doses and a matrix dominated reaction at lower doses accounts for the high development contrast with a NaOH base/NaCl salt mixture. The interplay between the hydrated and the nonhydrated ion sizes leads to higher contrast developers, such as tetramethyl ammonium hydroxide with NaCl.

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