Protein-reactive electrophiles are critical to chemical proteomic applications including activity-based protein profiling, site-selective protein modification, and covalent inhibitor development. Here, we explore the protein reactivity of a panel of aryl halides that function through a nucleophilic aromatic substitution (S(N)Ar) mechanism. We show that the reactivity of these electrophiles can be finely tuned by varying the substituents on the aryl ring. We identify p-chloro- and fluoronitrobenzenes and dichlorotriazines as covalent protein modifiers at low micromolar concentrations. Interestingly, investigating the site of labeling of these electrophiles within complex proteomes identified p-chloronitrobenzene as highly cysteine selective, whereas the dichlorotriazine favored reactivity with lysines. These studies illustrate the diverse reactivity and amino-acid selectivity of aryl halides and enable the future application of this class of electrophiles in chemical proteomics.
Small-molecule inhibitors can accelerate the functional annotation and validate the therapeutic potential of proteins implicated in disease. Phenotypic screens provide an effective platform to identify such pharmacological agents but are often hindered by challenges associated with target identification. For many protein targets, these bottlenecks can be overcome by incorporating electrophiles into small molecules to covalently trap interactions in vivo and by employing bioorthogonal handles to enrich the protein targets directly from a complex proteome. Here we present the trifunctionalized 1,3,5-triazine as an ideal modular scaffold for generating libraries of irreversible inhibitors with diverse target specificities. A divergent synthetic scheme was developed to derivatize the triazine with an electrophile for covalent modification of target proteins, an alkyne as a click-chemistry handle for target identification, and a diversity element to direct the compounds toward distinct subsets of the proteome. We specifically targeted our initial library toward cysteine-mediated protein activities through incorporation of thiol-specific electrophiles. From this initial screen we identified two compounds, RB-2-cb and RB-11-ca, which are cell permeable and highly selective covalent modifiers for Cys239 of β-tubulin (TUBB) and Cys53 of protein disulfide isomerase (PDI) respectively. These compounds demonstrate in vitro and cellular potencies that are comparable to currently available modulators of tubulin polymerization and PDI activity. Our studies demonstrate the versatility of the triazine as a modular scaffold to generate potent and selective covalent modifiers of diverse protein families for chemical genetics applications.
Treatment of cyclobutanone or cyclopentanone with N-hydroxybenzenesulfonamide under basic conditions yields the ring-expanded cyclic hydroxamic acid in 18-69% yield. Reactions of substituted cyclobutanones give ring expanded products where the -NOH group regio- and stereoselectively inserts to the more substituted position. This expansion likely proceeds through a mechanism that includes addition of the N-anion of N-hydroxybenzenesulfonamide to the ketone and a C-nitroso intermediate that rearranges to the final product.
une solution de phénol-formaldéhyde dans l'eau à une température élevée proche de 140 °C. On a trouvé expérimentalement qu'à une température entre 135 °C et 140 °C, une solution contenant 3,0 % de phénol avec un rapport molaire de phénol-formaldéhyde de 1,0:3,5 formait un gel ayant un pH compris entre 9,6 et 12,0. Le temps de gélifi cation minimum est observé à une valeur de pH de 10,4. La formation de gel s'avère fortement dépendante du pH à cette température élevée. On présente une explication pour le comportement de gélifi cation, qui s'appuie sur une concentration d'ions optimale de Na+ pour initier la formation de tri-méthylol. On pose comme hypothèse que la formation de gel commence quand la concentration de phénol de tri-méthylol atteint une valeur de concentration seuil. Des observations expérimentales et une analyse cinétique appuient cette hypothèse.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.