Huisgen 1,3-dipolar cycloadditions [1] are exergonic fusion processes that unite two unsaturated reactants and provide fast access to an enormous variety of five-membered hetero-Cl atoms having a marked anionic character. [30] This feature is also realized, but to a lesser extent, in the MÀCl bonds of complexes 2 ± 6.The present study illustrates for the first time the ability of an a-cyclodextrin cavity to recognize a transition metal MÀCl bond through weak Cl ¥¥¥ H-5 interactions in the solid state as well as in solution. The fact that such subtle interactions could be observed in non-aqueous media is a consequence of the absence of stronger competing supramolecular forces, such as the hydrophobic effect, which usually plays a prevailing role in the formation of CD inclusion complexes. Overall these results illustrate the potential of modified cyclodextrins as second-sphere ligands.

Huisgen 1,3-dipolar cycloadditions [1] are exergonic fusion processes that unite two unsaturated reactants and provide fast access to an enormous variety of five-membered hetero-Cl atoms having a marked anionic character. [30] This feature is also realized, but to a lesser extent, in the MÀCl bonds of complexes 2 ± 6.The present study illustrates for the first time the ability of an a-cyclodextrin cavity to recognize a transition metal MÀCl bond through weak Cl ¥¥¥ H-5 interactions in the solid state as well as in solution. The fact that such subtle interactions could be observed in non-aqueous media is a consequence of the absence of stronger competing supramolecular forces, such as the hydrophobic effect, which usually plays a prevailing role in the formation of CD inclusion complexes. Overall these results illustrate the potential of modified cyclodextrins as second-sphere ligands.

The cover picture shows the electric eel, Electrophorus electricus, a source for commercially available acetylcholinesterase. In an experiment described by K. B. Sharpless and M. G. Finn and co‐workers on pp. 1053–1057, a femtomolar inhibitor was assembled by the enzyme from a collection of building blocks containing azide and alkyne functional groups, shown floating in solution. The templated 1,3‐dipolar cycloaddition reaction, producing the inhibitor, is represented by the flare of light at the center of the image.

Form‐fitting chemistry in a protein mold is enabled by the use of the 1,3‐dipolar cycloaddition of azides and alkynes. The enzyme acetylcholinesterase preferentially assembles one pair of these reactants, each of which bears a group that binds to adjacent positions on the protein structure (see picture), into a 1,2,3‐triazole adduct that is the most potent noncovalent inhibitor of the enzyme yet developed.

The fragmentation characteristics of native and permethylated oligosaccharides using a matrix-assisted laser desorption/ionization (MALDI) time-of-flight/time-of-flight tandem mass spectrometer are described. The use of two MALDI matrixes, alpha-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB), is shown to control the nature and extent of fragmentation observed in collision-induced dissociation experiments on synthetic oligosaccharides. CHCA promotes the occurrence of glycosidic cleavages, whereas DHB promotes a wide range of fragmentations. These latter fragmentations include glycosidic cleavages, cross-ring cleavages, and the formation of "internal" cleavage ions, which are derived from elimination of substituents from around the pyranose ring. This extensive fragmentation is shown to facilitate the detailed structural characterization of high-mannose and hybrid-type N-glycans purified from avidin. Importantly, the cross-ring fragments reveal linkage information, unambiguously define antennae substitutions, and differentiate isomeric glycoforms.