I
An ECD investigation aiming at assessing the critical main-chain length for peptide helix formation in water solution is reported. To this goal, it was synthesized by a solution step-by-step protocol a complete series of N-terminally acetylated, C-terminally methoxylated oligopeptides, characterized only by alternating Aib and Ala residues, from the di- to the nonamer stage. All of these compounds were investigated by ECD in the far-UV region in water solution as a function of chemical structure, the presence/absence of the ester moiety at the C-terminus and temperature. The critical main-chain lengths for 310- and α-helices, although still formed to a partial extent, in aqueous solution are six and eight residues, respectively.
II
A whole series of AuNps was synthesized from mercaptopropionic derivatives of alternating Aib/Ala peptide series. Our studies established the occurrence of chiroptical properties in peptide-coated 2 nm diameter gold nanoparticles. The peptides induce a chiral effect onto the plasmon resonance band detectable via ECD. Such a behavior appears to be strongly influenced by the secondary structure assumed by the coating peptides.
III
The water solubility displayed by alternating Aib/Ala peptide series was investigated. The evidences of the formation of self-assembled structures in water, likewise responsible for the unexpected solubility properties, are presented. These peptide aggregates are spherical, with diameters up to 100 nm. They can also incorporate other molecular structures of relevant size, such as Au nanoparticles. Such systems may widen the number of applications currently accessible to self-assembled aggregates in the fields of biomedicine and materials science.
IV
Two new Ca-tetrasubstituted a-amino acids bearing two identical azobenzene-derived side chains have been synthesized. Photo-reversible isomerization process was detected. Intermediate chiral species are generated during the isomerization process driven by iii
light. Diastereomers where generated when a chiral protein amino acid was inserted.
The conjugation of one of the bis(azobenzene)-derived amino acids with different metal
nanoparticles allowed the isomerization process to be detected even in solid state.
Furthermore, the Au-derived nanoparticles exhibit a magnetic susceptibility dependence
on the light-driven isomerization state that can be simply detected by 1H-NMR
spectroscopy. Based on this behavior, these amino acids are of relevant potential for the
development of a novel class of materials.
V
A series of Ferrocene and Pyrene labelled helical peptides containing one or more 4-
amino-1,2-dithiolane-4-carboxylic acid (Adt) residues have been synthetized. Such
peptides have been prepared to be employed in the formation of SAMs over gold
surfaces (by means of linkage with the dithiolane Adt side chains) for electrochemical
applications. In particular, the peptides have been designed for ensuring: (i) an highrigidity
of the peptide scaffold and (ii) a parallel disposition of the peptide axle respect
the metal surface. Conformational characterizations and CV tests on a Ferrocene
binding 6-mer are presented. Preliminary experiment on the photo-current generation
property has also been performed
