Institute of High Technologies

The delivery of SiC-based nanoparticles (SiC-NPs) into living eukaryotic cells is facilitated in the presence of cell-penetrating peptides, both cationic (SAP) and anionic (SAP-E). The SiC-NP surface functional group modification combined with rational CPP selection introduces an additional mode of delivery control. † Electronic supplementary information (ESI) available: Preparation of the SiC-derived nanoparticles, synthesis of the cell-penetrating peptides, treatment of the SiC-NPs with the cell-penetrating peptides SAP and SAP-E, details of the study of the SiC-NPs delivery into the cells. See

A simple and efficient procedure for the multigram synthesis of both (±)-trans-and (±)-cis-1-amino-2-(trifluoromethyl)cyclopropane-1-carboxylic acid was developed. The key step of the synthesis is the addition of 1-diazo-2,2,2-trifluoroethane to methyl 2-[(tert-butoxycarbonyl)amino]acrylate, followed by thermal decomposition of the resulting pyrazoline. Gram quantities of transand cis-1-amino-2-(trifluoromethyl)cyclopropane-1-carboxylic acid were easily prepared from L-serine in one synthetic run.

A range of alkenes have been converted in a single step into the corresponding trifluoromethyl-substituted cyclopropanes by treatment with 2-diazo-l,l,l-trifluoroethane over metal catalysts. Application of the Gaspar-Roth procedure allowed the preparation of target compounds on a multi-gram scale. The practical utility of this reaction has been demonstrated by the synthesis of both diastereoisomers of the non-natural amino acid trifluoronorcoronamic acid in two steps.

Structure analysis of the cell-penetrating peptide transportan 10 (TP10) revealed an exemplary range of different conformations in the membrane-bound state. The bipartite peptide (derived N-terminally from galanin and C-terminally from mastoparan) was found to exhibit prominent characteristics of (i) amphiphilic a-helices, (ii) intrinsically disordered peptides, as well as (iii) b-pleated amyloid fibrils, and these conformational states become interconverted as a function of concentration. We used a complementary approach of solid-state 19 F-NMR and circular dichroism in oriented membrane samples to characterize the structural and dynamical behaviour of TP10 in its monomeric and aggregated forms. Nine different positions in the peptide were selectively substituted with either the Lor D-enantiomer of 3-(trifluoromethyl)bicyclopent-[1.1.1]-1-ylglycine (CF 3 -Bpg) as a reporter group for 19 F-NMR. Using the L-epimeric analogs, a comprehensive three-dimensional structure analysis was carried out in lipid bilayers at low peptide concentration, where TP10 is monomeric. While the N-terminal region is flexible and intrinsically unstructured within the plane of the lipid bilayer, the Cterminal a-helix is embedded in the membrane with an oblique tilt angle of ,55u and in accordance with its amphiphilic profile. Incorporation of the sterically obstructive D-CF 3 -Bpg reporter group into the helical region leads to a local unfolding of the membrane-bound peptide. At high concentration, these helix-destabilizing C-terminal substitutions promote aggregation into immobile b-sheets, which resemble amyloid fibrils. On the other hand, the obstructive D-CF 3 -Bpg substitutions can be accommodated in the flexible N-terminus of TP10 where they do not promote aggregation at high concentration. The cross-talk between the two regions of TP10 thus exerts a delicate balance on its conformational switch, as the presence of the a-helix counteracts the tendency of the unfolded N-terminus to self-assemble into b-pleated fibrils. Citation: Fanghänel S, Wadhwani P, Strandberg E, Verdurmen WPR, Bü rck J, et al. (2014) Structure Analysis and Conformational Transitions of the Cell Penetrating Peptide Transportan 10 in the Membrane-Bound State. PLoS ONE 9(6): e99653.

A practical synthetic approach to the construction of a library of three isomeric/homologous β-trifluoromethyl-substituted pyrrolidines is disclosed. All products were prepared in multigram quantities from a common precursor. The key syn-[a] Enamine

Photobiological processes in nature are usually triggered by nonpeptidic chromophores or by modified side chains. A system is presented in which the polypeptide backbone itself can be conformationally switched by light. An amino acid analogue was designed and synthesized based on a reversibly photoisomerizable diarylethene scaffold. This analogue was incorporated into the cyclic backbone of the antimicrobial peptide gramicidin S at several sites. The biological activity of the resulting peptidomimetics could then be effectively controlled by ultraviolet/visible light within strictly defined spatial and temporal limits.

Single D-amino acid substitutions can be used to suppress or slow down the aggregation of peptides into b-sheeted assemblies compared to the respective L-amino acids. Here, we investigate the influence of local stereochemistry in the model peptide [KIGAKI] 3 -NH 2 , which is known to form amyloid-like fibrils. To find out whether aggregation plays a role in various biologically relevant functions that involve peptide-lipid interactions, we studied the antimicrobial, hemolytic and fusogenic activities of this amphiphilic membrane-active molecule. The stiff and sterically constrained amino acid CF 3 -Bpg [3-(trifluoromethyl)-bicyclopent-[1,1,1]-1-ylglycine] was incorporated either as an L-or a D-enantiomer at different hydrophobic positions of the KIGAKI sequence. D-Epimers have a higher aggregation threshold than the L-epimers, yet the aggregation of both was confirmed using electron microscopy and circular dichroism. Solid-state 19 F-NMR analysis showed that the peptide aggregated in native membranes from human erythrocytes and bacterial protoplasts in the same way as in synthetic lipid bilayers. We then monitored the effect of the single L-or D-CF 3 -Bpg substitutions in KIGAKI on its distinct biological activities, which have to be measured at low peptide concentrations where the aggregation threshold cannot be directly assessed. These functional assays showed that the aggregation propensity of KIGAKI does not play a role in its antimicrobial action, but an increased tendency to aggregate promotes other undesirable effects such as hemolysis and membrane fusion. These results confirm the membranolytic and thereby toxic nature of amyloidogenic peptides, and emphasize the unpredictable role of peptide aggregation in the different assays used to study biological activities.

Two isomeric conformationally restricted analogues of 4-trifluoromethylpiperidine were designed. The synthesis was performed in four steps from commercially available N-benzylmaleimide. The key reaction was the [3+2] cycloaddition between trifluoromethyldiazomethane and N-benzylmaleimide.