Glycoside hydrolases are important enzymes in a number of essential biological processes. Irreversible inhibitors of this class of enzyme have attracted interest as probes of both structure and function. In this review we discuss some of the compounds used to covalently modify glycosidases, their use in residue identification, structural and mechanistic investigations, and finally their applications, both in vitro and in vivo, to complex biological systems.

While covalent catalytic intermediates of retaining alpha-transglycosylases have been structurally characterized previously, no such information for a hydrolytic alpha-amylase has been obtained. This study presents a new "in situ" enzymatic elongation methodology that, for the first time, has allowed the isolation and structural characterization of a catalytically competent covalent glycosyl-enzyme intermediate with human pancreatic alpha-amylase. This has been achieved by the use of a 5-fluoro-beta-l-idosyl fluoride "warhead" in conjunction with either alpha-maltotriosyl fluoride or 4'-O-methyl-alpha-maltosyl fluoride as elongation agents. This generates an oligosaccharyl-5-fluoroglycosyl fluoride that then reacts with the free enzyme. The resultant covalent intermediates are extremely stable, with hydrolytic half-lives on the order of 240 h for the trisaccharide complex. In the presence of maltose, however, they undergo turnover via transglycosylation according to a half-life of less than 1 h. Structural studies of intermediate complexes unambiguously show the covalent attachment of a 5-fluoro-alpha-l-idosyl moiety in the chair conformation to the side chain of the catalytic nucleophile D197. The elongated portions of the intermediate complexes are found to bind in the high-affinity -2 and -3 binding subsites, forming extensive hydrogen-bonding interactions. Comparative structural analyses with the related noncovalent complex formed by acarbose highlight the structural rigidity of the enzyme surface during catalysis and the key role that substrate conformational flexibility must play in this process. Taken together, the structural data provide atomic details of several key catalytic steps. The scope of this elongation approach to probe the active sites and catalytic mechanisms of alpha-amylases is further demonstrated through preliminary experiments with porcine pancreatic alpha-amylase.

The ongoing COVID-19 pandemic has disrupted face-to-face instruction in educational institutions all over the world. As instructors we had to scramble to completely change courses to emergency remote delivery, sometimes with only a few days' notice. Herein, we present reflections on the successes and challenges we encountered following the sudden and unexpected transition to remote delivery. We also address ways that we managed the obstacles faced, from overcoming technological issues posed by remote delivery to adaptation of laboratory content for emergency remote delivery. In addition, we discuss successful strategies for assessment of student learning and student engagement in the online environment. Overall, we found that students' motivation was high, as indicated by online class attendance and engagement with course activities. We believe that the existing strong student−instructor relationships at our small liberal arts and sciences campus contributed to the unexpectedly high level of student engagement.

Amides of 2‐iodoxybenzoic acid (IBX amides, 1) are a new class of pentavalent iodine compounds with a pseudo‐benziodoxole structure. These 2‐iodoxybenzamides are useful reagents for the oxidation of alcohols, with a reactivity pattern similar to IBX (R=CH(CH3)CO2CH3 or CH(CH2Ph)CO2CH3 (in crystal structure shown)).

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