Modulating angiogenesis is an attractive goal because many pathological conditions depend on the growth of new vessels. Angiogenesis is mainly regulated by the VEGF, a mitogen specific for endothelial cells. In the last years, many efforts have been pursued to modulate the angiogenic response targeting VEGF and its receptors. Based on the x-ray structure of VEGF bound to the receptor, we designed a peptide, QK, reproducing a region of the VEGF binding interface: the helix region 17–25. NMR conformation analysis of QK revealed that it adopts a helical conformation in water, whereas the peptide corresponding to the α-helix region of VEGF, VEGF15, is unstructured. Biological assays in vitro and on bovine aorta endothelial cells suggested that QK binds to the VEGF receptors and competes with VEGF. VEGF15 did not bind to the receptors indicating that the helical structure is necessary for the biological activity. Furthermore, QK induced endothelial cells proliferation, activated cell signaling dependent on VEGF, and increased the VEGF biological response. QK promoted capillary formation and organization in an in vitro assay on matrigel. These results suggested that the helix region 17–25 of VEGF is involved in VEGF receptor activation. The peptide designed to resemble this region shares numerous biological properties of VEGF, thus suggesting that this region is of potential interest for biomedical applications, and molecules mimicking it could be attractive for therapeutic and diagnostic applications.

Peptide nucleic acids (PNAs) are oligonucleotide analogues in which the sugar-phosphate backbone has been replaced by a pseudopeptide skeleton. They bind DNA and RNA with high specificity and selectivity, leading to PNA–RNA and PNA–DNA hybrids more stable than the corresponding nucleic acid complexes. The binding affinity and selectivity of PNAs for nucleic acids can be modified by the introduction of stereogenic centers (such as d -Lys-based units) into the PNA backbone. To investigate the structural features of chiral PNAs, the structure of a PNA decamer containing three d -Lys-based monomers (namely H-GpnTpnApnGpnAdlTdlCdlApnCpnTpn-NH ₂ , in which pn represents a pseudopeptide link and dl represents a d -Lys analogue) hybridized with its complementary antiparallel DNA has been solved at a 1.66-Å resolution by means of a single-wavelength anomalous diffraction experiment on a brominated derivative. The d -Lys-based chiral PNA–DNA (LPD) heteroduplex adopts the so-called P-helix conformation. From the substantial similarity between the PNA conformation in LPD and the conformations observed in other PNA structures, it can be concluded that PNAs possess intrinsic conformational preferences for the P-helix, and that their flexibility is rather restricted. The conformational rigidity of PNAs is enhanced by the presence of the chiral centers, limiting the ability of PNA strands to adopt other conformations and, ultimately, increasing the selectivity in molecular recognition.

Peptide Nucleic Acids (PNAs), nucleic acid analogues showing high stability to enzyme degradation and strong affinity and specificity of binding toward DNA and RNA are widely investigated as tools to interfere in gene expression. Several studies have been focused on PNA analogues with modifications on the backbone and bases in the attempt to overcome solubility, uptake and aggregation issues. γ PNAs, PNA derivatives having a substituent in the γ position of the backbone show interesting properties in terms of secondary structure and affinity of binding toward complementary nucleic acids. In this paper we illustrate our results obtained on new analogues, bearing a sulphate in the γ position of the backbone, developed to be more DNA-like in terms of polarity and charge. The synthesis of monomers and oligomers is described. NMR studies on the conformational properties of monomers and studies on the secondary structure of single strands and triplexes are reported. Furthermore the hybrid stability and the effect of mismatches on the stability have also been investigated. Finally, the ability of the new analogue to work as antigene, interfering with the transcription of the ErbB2 gene on a human cell line overexpressing ErbB2 (SKBR3), assessed by FACS and qPCR, is described.