Dishevelled (DVL) is the key component of the Wnt signaling pathway. Currently, DVL conformational dynamics under native conditions is unknown. To overcome this limitation, we develop the Fluorescein Arsenical Hairpin Binder- (FlAsH-) based FRET in vivo approach to study DVL conformation in living cells. Using this single-cell FRET approach, we demonstrate that (i) Wnt ligands induce open DVL conformation, (ii) DVL variants that are predominantly open, show more even subcellular localization and more efficient membrane recruitment by Frizzled (FZD) and (iii) Casein kinase 1 ɛ (CK1ɛ) has a key regulatory function in DVL conformational dynamics. In silico modeling and in vitro biophysical methods explain how CK1ɛ-specific phosphorylation events control DVL conformations via modulation of the PDZ domain and its interaction with DVL C-terminus. In summary, our study describes an experimental tool for DVL conformational sampling in living cells and elucidates the essential regulatory role of CK1ɛ in DVL conformational dynamics.

Backbone N-substitution of peptides (N-Me and N-alkyl) has become of special interest as a chemical tool for peptide lead modification, either to improve biological activity or to optimize key pharmacokinetic characteristics. For the synthesis of backbone N-methylated peptides, many protocols have been developed already, yet some effort often has to be made to find appropriate conditions for the acylation of N-Me residues. Fewer examples are reported of peptides with other backbone N-substituents different than N-Me, and their synthesis is frequently reported as difficult. The synthesis of such peptides becomes more difficult as the size of the N-substituent increases. Coupling methods that work for the synthesis of N-methylated peptides were often found to fail when applied to peptides with larger N-substituents. This review addresses the challenges of the synthesis of backbone N-modified peptides, focusing on N-substituents larger than the N-Me group.

Cu(I)-catalyzed 1,3-dipolar cycloaddition with mPEG 2000 -NH-CO-CH 2 CH 2 -alkyne …..…..…….. 18 N-acylation with mPEG 2000 -CH 2 CH 2 -COOSu ……………………………………………………….. 19 Reductive N-alkylation with mPEG 2000 -CH 2 CH 2 -CHO…………..……..…………………………… 20 3. NMR characterization of cyclo[RGDfNMeV] (1) and cyclo[RGDf(N-CH 2 CH 2 CH 2 CH 2 N 3

Here we studied the N-triethylene glycol (N-TEG) group as a surrogate for the N-Me group in Sansalvamide A peptide. The five N-TEG and N-Me analogs of this cyclic pentapeptide were synthesized, and their biological activity, lipophilicity and conformational features were compared.

Cilengitide is an RGD-peptide of sequence cyclo[RGDfNMeV] that was was developed as a highly active and selective ligand for the αvβ3 and αvβ5 integrin receptors. We describe the synthesis of three analogues of this peptide in which the N-Me group has been replaced by N-oligoethylene glycol (N-OEG) chains of increasing size: namely N-OEG2, N-OEG11, and N-OEG23, which are respectively composed of 2, 11, and 23 ethylene oxide monomer units. The different N-OEG cyclopeptides and the original peptide were compared with respect to lipophilicity and biological activity. The N-OEG2 analogue was straightforward to synthesize in solid phase using an Fmoc-N-OEG2 building block. The syntheses of the N-OEG11 and N-OEG23 cyclopeptides are hampered by the increased steric hindrance of the N-substituent, and could only be achieved by segment coupling, which takes place with epimerization and thus requires extensive product purification. All the N-OEG analogues were found to be more hydrophobic than the parent peptide, and their hydrophobicity was systematically enhanced upon increasing the length of the OEG chain. The N-OEG2 cyclopeptide displayed the same capacity as Cilengitide to inhibit the integrin-mediated adhesion of HUVEC endothelial, DAOY gliobastoma, and HT-29 colon cancer cells to their ligands vitronectin and fibrinogen. The N-OEG11 and N-OEG23 analogues also inhibited cell adhesion to these immobilized ligands, but their IC50 values dropped by 1 order of magnitude with respect to the parent peptide. These results indicate that replacement of the backbone N-Me group of Cilengitide by a short N-OEG chain provides a more lipophilic analogue with a similar biological activity. Upon increasing the size of the N-OEG chain, liophilicity is enhanced, but synthetic yields drop and the longer polymer chains may impede targeted binding.

No abstract

Backbone N‐substitution of peptides (N‐Me and N‐alkyl) has become of special interest as a chemical tool for peptide lead modification, either to improve biological activity or to optimize key pharmacokinetic characteristics. For the synthesis of backbone N‐methylated peptides, many protocols have been developed already, yet some effort often has to be made to find appropriate conditions for the acylation of N‐Me residues. Fewer examples are reported of peptides with other backbone N‐substituents different than N‐Me, and their synthesis is frequently reported as difficult. The synthesis of such peptides becomes more difficult as the size of the N‐substituent increases. Coupling methods that work for the synthesis of N‐methylated peptides were often found to fail when applied to peptides with larger N‐substituents. This review addresses the challenges of the synthesis of backbone N‐modified peptides, focusing on N‐substituents larger than the N‐Me group. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 104: 435–452, 2015.

An efficient strategy to synthesize tartaric acid building blocks for totally regioselective transformations or derivatizations was disclosed. Starting from l-tartaric acid or l-dimethyl tartrate, respectively, we obtained type I and II building blocks with orthogonal sets of protecing groups (4-8 steps, 38-56% overall yield).