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In Saccharomyces cerevisiae, external high osmolarity activates the Hog1 mitogen-activated protein kinase (MAPK), which controls various aspects of osmoadaptation. Ssk1 is a homolog of bacterial two-component response regulators and activates the Ssk2 MAPK kinase kinase upstream of Hog1. It has been proposed that unphosphorylated Ssk1 (Ssk1-OH) is the(More)
A judicious choice of photoreactive group is critical in successful photoaffinity labeling studies of small molecule-protein interactions. A set of carbohydrate-based photoaffinity probes was prepared to compare the effects of three major photoreactive groups on the efficiency and selectivity of crosslinking a binding protein with low affinity. We showed(More)
PHOTO OPPORTUNITY: We have developed a dual photoaffinity labeling system in which an active and an inactive probe bearing orthogonal detection groups are co-reacted in a single photoreaction. The approach allowed selective fluorescent detection of a model binding protein in cell lysate by either 1D or 2D electrophoresis.
OSW-1 is a steroidal saponin, which has emerged as an attractive anticancer agent with highly cancer cell selective activity. A fluorescent analog was prepared from the natural product to analyze its cellular uptake and localization. We found that the fluorescent analog is rapidly internalized into cells and is primarily distributed in endoplasmic reticulum(More)
A strategy to site-selectively monoacylate an antitumor saponin OSW-1 was developed using an organotin reagent to rapidly access its derivatives that are useful as chemical probes. 4″-O-Acylated OSW-1 derivatives bearing a fluorophore, an alkyne tag, or biotin were prepared in good yields and were shown to maintain highly cytotoxic activity.
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