N-linked peptidoresorc[4]arene-based receptors designed for protein surface recognition. NMR analysis of Italian virgin olive oils and structural analysis of polysaccharides

The first part of this work concerned the synthesis of N-linked peptideresorcarenes and the study of their surface interaction with enzymes. As known, an important class of protein surface receptors based on the attachment of four cyclic peptides to a calix[4]arene scaffold was developed by Hamilton and targeted to the serine protease α-chymotrypsin (ChT). Moving from Hamilton’s results and from some preliminary molecular modeling studies, valyl-leucine, leucyl-valine and valyl-aspartic peptidoresorc[4]arenes have been designed with the aim to target the predominantly cationic region surrounding the active site of ChT. By varying sequence, nature, and stereochemistry of the side chains, we prepared anionically functionalized N-linked peptidoresorc[4]arenes by hydrogenation of their precursor benzyl esters. From this family of receptors we have identified noncompetitive inhibitors of ChT, which function by binding to the surface of the enzyme in the neighborhood of the active site cleft (Ki values ranging from 13 to 0.8 µM). The second topic of the work was the NMR characterization of the Italian virgin olive oils from the harvesting seasons 2009/10, 2010/11. Following the experimental protocol established in the Annalaura Segre NMR Laboratory (CMI, CNR in Montelibretti, Rome), based on 1H-NMR and statistical multivariate analysis of the data (ANOVA, PCA and LDA), nearly 300 Italian virgin olive oil samples, produced in two harvesting years, 2009/10 and 2010/11, by certified chains in different italian regions have been studied. The NMR results confirm that the chemical composition of olive oils, with regards to minor components, is influenced by geographical, ecological and genetic factors and depends also on the harvesting year. We could also identify some oil components that remain stable in different harvesting years, representing seasonal-independent characteristics of the oil produced in each region. A contemporary investigation, carried out at CNR, was focused on structural analysis of polysaccharides. Specificaly, we performed NMR characterization of a carboxy-methyl derivative of scleroglucan, a polysaccharide produced by fungi of the Sclerotium genus, to identify the position involved in the carboxymethylation; furthermore, a preliminary structural study has been performed on a set of polysaccharides obtained from the cultures of Hericium erinaceus, with the aim of identifying the configuration and the connections between the monosaccharidic units.