Conformational study of a conventionally protected beta-Casomorphine-8

Many biologically active peptides are generated by proteolytic processing of various higher molecular weight multifunctional precursor peptides and proteins. The enzymes of different structures and specificity are involved in the synthesis, posttranslational modifications and release of peptide products, including hormones, neurotransmitters, and opioids. During the last two decades a variety of "atypical" exogenous opioid peptides derived from enzymatic digest of various food proteins sources has been demonstrated. Most of the food-derived opioids are peptides fragments of milk proteins (caseins, alpha-lactalbumin, beta-lactoglobulin, and lactotransferrin), plant proteins (wheat gluten) or constituents of meats (hemoglobin and bovine serum albumin). These peptides identified in exogenous sources were named exorphins. Most of the information available so far has been collected about exorphins isolated from ?- or ?-casein, casomorphins (CM). In this work we present the data of conformational study of the synthetic analogues of ?-CM-8 having Boc- and -OMe as terminals protecting groups. These products have been synthesized, purified and then analyzed by NMR spectroscopy in order to obtain structural and conformational information to use in molecular simulation experiments. A comparison of experimental spectroscopic data with structural information from empirical models allow us to understand behaviour of these peptides in solution.