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Diazo peptides have been described earlier, however, due to their high reactivity have not been broadly used until today. Here, we report the preparation, properties, and applications of chemically stable internal diazo peptides. Peptidyl phosphoranylidene‐esters and amides were found to react with triflyl azide primarily to novel 3,4‐disubstituted triazolyl‐peptides. Nonaflyl azide instead furnished diazo peptides, which are chemically stable from pH 1–14 as amides and from pH 1–8 as esters. Thus, diazo peptides prepared by solid phase peptide synthesis were stable to final deprotection with 95 % trifluoroacetic acid. Diazo peptides with the recognition sequence of caspase‐3 were identified as specific, covalent, and irreversible inhibitors of this enzyme at low nanomolar concentrations. A fluorescent diazo peptide entered living cells enabling microscopic imaging and quantification of apoptotic cells via flow cytometry. Thus, internal diazo peptides constitute a novel class of activity‐based probes and enzyme inhibitors useful in chemical biology and medicinal chemistry. [ABSTRACT FROM AUTHOR]

Introduction: Bovine teeth are commonly used as substitutes for human teeth in scientific investigations. The present study was performed in vitro with the objective of comparing bovine and human enamel subjected to thermocycling for microleakage beneath metal brackets., Materials and Methods: A total of 50 bovine and human teeth (25 per group) void of defects or carious decay were extracted and stored in chloramine B (0.5%). A light-curing adhesive (Transbond™ XT) was used as instructed by the manufacturer (3M Unitek, Monrovia, CA, USA) to bond a metal bracket (discovery®; Dentaurum, Ispringen, Germany) to the surface of each tooth following 30 s of enamel etching (phosphoric acid 35%). After 24 h of dye penetration in methylene blue (0.5%), the cervical and incisal bracket surfaces were analyzed by light microscopy for excess bonding material, dye penetration, and microleakage at the bracket-adhesive and adhesive-enamel interfaces. Staining and evaluation was repeated after thermocycling (5000 cycles at 5/55 °C)., Results: Before thermocycling, the number of human teeth showing marginal gaps was one-third the number of bovine teeth (p<0.001). After thermocycling, the distribution of gaps was similar (p=0.180). The adhesive-enamel interface was most frequently affected (on 74% of human and 64% of bovine teeth). No dye penetration in either group after examining a horizontal slice through the bracket basis was observed., Conclusion: Immediately after bonding, less microleakage was observed around the base of metal brackets on human than bovine teeth. These marginal gaps were, however, superficial in both groups, none of them involving deep penetration of dye under the bracket base.