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When yeast cells enter into quiescence in response to nutrient limitation, the adenine deaminase Aah1p is specifically degraded via a process requiring the F-box protein Saf1p and components of the Skp1-Cullin-F-box complex. In this paper, we show that Saf1p interacts with both Aah1p and Skp1p. Interaction with Skp1p, but not with Aah1p, requires the F-box domain of Saf1p. Based on deletion and point mutations, we further demonstrate that the F-box domain of Saf1p is critical for degradation of Aah1p. We also establish that overexpression of Saf1p in proliferating cells is sufficient to trigger the degradation of Aah1p. Using this property and a two-dimensional protein gel approach, we found that Saf1p has a small number of direct targets. Finally, we isolated and characterized several point mutations in Aah1p, which increase its stability during quiescence. The majority of the mutated residues are located in two distinct exposed regions in the Aah1p three-dimensional model structure. Two hybrid experiments strongly suggest that these domains are directly involved in interaction with Saf1p. Importantly, we obtained a mutation in Aah1p that does not affect the protein interaction with Saf1p but abolishes Aah1p degradation. Because this mutated residue is an exposed lysine in the Aah1p three-dimensional model, we propose that it is likely to be a major ubiquitylation site. All together, our data strongly argue for Saf1p being a bona fide Skp1-Cullin-F-box subunit. [ABSTRACT FROM AUTHOR]

Abstract: Conducting polymer–fibre composites with polypyrrole cellulose (paper) and protein (wool) fibres have been produced by polymerizing pyrrole with ferric chloride as the oxidant around separated individual cellulose (wood) fibres from bleached Pinus radiata Kraft pulp, and merino wool fibres respectively to generate new composite materials that retain the inherent properties of the polymer and individual fibres. For the polypyrrole–cellulose composite, the polypyrrole consisted of spheres of about 100nm in size fused together to form a continuous coating that fully encapsulates the cellulose fibre and associated finer fibrils. For the polypyrrole–wool composite the polypyrrole formed a similar coating of about 200nm spheres. Electrical conductivities of the composites were substantially increased over those of the precursor fibres. [Copyright &y& Elsevier]

We studied the aging behaviour of gelatin used to size paper. Thus far, research on the aging of paper has largely ignored the sizing agent. Degradation of the protein was characterised and the impact of paper components, such as cellulose, and aluminium potassium sulphate was evaluated. Whatman No. 1 filter papers sized with two types of gelatins (A and B) were prepared as model samples. Commercially sized modern papers (Arches) were also studied in order to compare laboratory samples with real artist papers. Both types of papers were artificially aged (80 °C, 50% relative humidity for 35 and 94 days). Historic papers were included in the study in order to compare artificially aged with naturally aged gelatin. The aqueous extracts from the papers were characterised by aqueous size-exclusion chromatography (SEC) using four PL-Aquagel-OH columns and UV photodiode array detection at 220, 254 and 280 nm. Results showed that gelatin undergoes hydrolysis upon aging, type A gelatin showing a faster degradation rate than type B. The result was an increase in the lower-molar-mass fractions, under 50 000 g mol−1, and especially in a characteristic fraction with a peak molecular mass (Mp) of 14 000 g mol−1. A significant decrease in the extraction yields of α-, β- and γ-chains occurred after aging. This was attributed to crosslinking, leading to the formation of less-soluble polypeptides with very high molar mass (>800 000 g mol−1). Less than 10% alum had no impact on the degradation rate; higher alum contents accelerated hydrolysis reactions. [Copyright &y& Elsevier]