Herein is reported the successful entrapment of three esterase enzymes within silica, by means of the sol−gel process. The enzymes were acetylcholinesterase (AChE) from electric eel (ee), AChE from bovine erythrocytes (er), and butyrylcholinesterase (BChE) from horse serum. Enzyme entrapment was carried out in a novel configuration by casting the doped sol−gel material in 96-well microtiter plates. The study determined the apparent kinetics of the activity and inhibition of the three entrapped enzymes and elucidated the optimal sol−gel matrix composition and preparation procedure. The enzyme mode of action within the sol−gel matrix was compared with that obtained in solution, under various experimental conditions. The activity of entrapped ee-AChE was found to depend on the concentration of the entrapped enzyme and on the sol−gel preparation procedure and composition. It was found that whereas the activity of ee-AChE was 3−4-times lower than that in solution, one gained significantly higher stability. The entrapped enzymes were sensitive to various organophosphates and to the carbamate carbaryl, with inhibition patterns similar to those obtained in aqueous reactions. Keywords: Cholinesterases; residue analysis; sol−gel; organophosphates; carbamates

We describe an application of the backbone cyclization and cycloscan concept for the design and synthesis of pheromone biosynthesis activating neuropeptide (PBAN) antagonists capable of inhibiting sex pheromone biosynthesis in Heliothis peltigera female moths. Two backbone cyclic (BBC) sub-libraries were designed and synthesized. The structure of the first sub-library ([Arg 27 ]PBAN27-33NH 2 , termed the Ser sub-library) was based on the active C-terminal hexapeptide sequence (Tyr-Phe-Ser-Pro-Arg-Leu-NH 2 ) of PBAN1-33NH 2 , which was found to comprise its active core. It is well established that the activation of multiple receptors by the same peptide arises from the ability of a given peptide to exist in different interchangeable bioactive conformations (1). To attain receptor selectivity it is, therefore, essential to restrict the conformational space of a peptide so it can attain one bioactive conformation.Cyclization is an important and attractive way to restrict the conformational space of peptidic structures (1). Conformationally restricted peptides containing medium and long range cyclizations have been mainly prepared following the same modes of cyclization of naturally occurring peptides. These include end-to-end, side-chain-to-side-chain, and side-chain-toend (2). These modes of cyclization involve modifications of side chains and ends which in many cases are essential for bioactivity, and therefore their modification causes loss of activity. Also, these modes of cyclization are not sufficient to screen effectively the conformational space available for a linear peptide with a given sequence. To overcome these limitations, we have introduced two methods called backbone cyclization (2) and cycloscan (3).Backbone cyclization is a general method by which a conformational constraint is imposed on peptides through the connection of the N ␣ and/or C ␣ atoms in the peptide backbone to each other or to side chains or to the carboxyl and amino ends (2). Thus, the cyclization can be performed while retaining the functionality and the activity of the side chains. Backbone cyclization allows nine new modes of cyclization in addition to the four modes in naturally occurring peptides. Preparation of backbone cyclic (BBC) 1 peptides involves the use of a large variety of orthogonally protected N ␣ and C ␣ (-amino-, -carboxy-, and -thio-alkyl) amino acids building units (4 -6). Synthetic procedures have been developed to incorporate these building units into peptides using the solid phase methodology (7,8).The advantages of backbone cyclization over the naturally occurring modes of cyclization are because of the immense variability of spatial orientation of the constitute residues which result from the multiple anchoring points within a chain or between chains. This allows us to screen the conformational space of a given peptide in an extremely efficient manner. Furthermore, most of the modes of backbone cyclization do not involve chemical modifications of side chains which are essential for biological activity. Ba...

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