To screen one-bead-one-compound (OBOC) combinatorial libraries, tens of thousands to millions of compound beads are first mixed with a target molecule. The beads that interact with this molecule are then identified and isolated for compound structure determination. Here we describe an OBOC peptide library screening using streptavidin (SA) as probe protein, labeled with a red fluorescent dye and using the COPAS BIO-BEAD flow sorting equipment to separate fluorescent from nonfluorescent beads. The red dyes used were ATTO 590 and Texas Red. After incubating the library with the SA-red fluorescent dye conjugate, we isolated positive beads caused by peptide-SA interaction and false positive beads produced by peptide fluorescent dye interaction. These false positives were a drawback when sorting beads by COPAS. However,an in depth analysis of both kinds of beads allowed the differentiation of positives from false positives. The false positive beads showed bright homogeneous fluorescence, while positive beads had a heterogeneous fluorescence, exhibiting a characteristic halo appearance, with fluorescence intensity greatest at the bead surface and lowest in the core. The difference was more evident when using Texas Red instead of ATTO 590. Thus, positive beads could be manually separated from false positive ones. The beads were analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Most of the sequences obtained from positive beads had the His-Pro-Gln motif. Peptides from false positive beads were rich in Leu/Ileu, His, Phe, and Tyr.

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α- and β-galactosidase (α- and β-Gal) activities, firmness and pigment content were analysed in tomato (Lycopersicon esculentum Mill.) pericarp during fruit growth and ripening, comparing normal fruit with transgenic fruit containing an ACC-synthase antisense transgene. Normal and transgenic immature green fruit had similar temporal patterns of total α- and β-Gal activity. Immature 21-day-old fruit displayed 93% and 134% higher α- and β-Gal activity on a per gram fresh weight basis, respectively, than mature-green fruit. During ripening, normal fruit presented increasing levels of α- and β-Gal activity towards the red-ripe stage. β-Gal II was detected in mature-green tomatoes; it rose rapidly and reached maximum values at the red-ripe stage. In contrast, α- and β-Gal activity in antisense fruit decreased after reaching the breaker stage, and a low continuous level of activity was apparent between 54 and 108 days after anthesis. 48- to 108-day-old transgenic fruit showed constant basal levels of β-Gal II. There were no significant differences in enzyme activity between antisense attached and detached fruit. An exogenous ethylene treatment performed in transgenic tomatoes brought about a promotive effect on total α- and β-Gal activity in general and on β-Gal II in particular, thus suggesting a role for ethylene in de novo synthesis or activation of these enzymes. Softening, chlorophyll breakdown and lycopene biosynthesis were impaired in the antisense fruits, but the impairment was only complete for lycopene synthesis and all were reversed by applied ethylene. These results can be associated with the signal transduction pathways proposed to be operational during tomato ripening.

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An acid protease having milk clotting activity has been isolated from Mucor bacilliformis cultures. The enzyme was basically purified by ionic exchange chromatography. An average yield of 29 mg purified product was obtained from 100 mL crude extract. As purity criteria, SDS-PAGE, reverse-phase HPLC, and N-terminal analysis were performed. The protease is a protein composed of a single polypeptide chain with glycine at the N-terminus. The mol wt is approx 32,000, and its amino acid composition is very similar to those of other fungal proteases. As expected, its clotting activity was drastically inhibited by pepstatin A action. On the other hand, its instability against heat treatment and its clotting/proteolytic activity ratio indicate that it may be considered as a potential substitute for bovine chymosin.