Conformational switch and multiple supramolecular structures of a newly identified self-assembling protein-mimetic peptide from Pseudomonas aeruginosa YeaZ protein

Protein-mimetic peptides (PMPs) are shorter sequences of self-assembling proteins, that represent remarkable building blocks for the generation of bioinspired functional supramolecular structures with multiple applications. The identification of novel aminoacidic sequences that permit the access to valuable biocompatible materials is an attractive area of research. In this work, in silico analysis of the Pseudomonas aeruginosa YeaZ protein (PaYeaZ) led to the identification of a tetradecapeptide that represents the shortest sequence responsible for the YeaZ-YeaZ dimer formation. Based on its sequence, an innovative 20-meric peptide, called PMP-2, was designed, synthesized, and characterized in terms of secondary structure and self-assembly properties. PMP-2 conserves a helical character and self-assembles into helical nanofibers in non-polar solvents (DMSO and trifluoroethanol), as well as in dilute (0.5 mM) aqueous solutions. In contrast, at higher concentrations (>2 mM) in water, a conformational transition from α-helix to β-sheet occurs, which is accompanied by the Protein-mimetic peptide aggregation into 2D-sheets and formation supramolecular gel in aqueous environment. Our findings reveal a newly identified Protein-mimetic peptide that could turn as a promising candidate for future material applications.

Peptide Design and Self-assembly into Targeted Nanostructure and Functional Materials

Peptides have been extensively utilized to construct nanomaterials that display targeted structure through hierarchical assembly. The self-assembly of both rationally designed peptides derived from naturally occurring domains in proteins as well as intuitively or computationally designed peptides that form β-sheets and helical secondary structures have been widely successful in constructing nanoscale morphologies with well-defined 1-d, 2-d, and 3-d architectures. In this review, we discuss these successes of peptide self-assembly, especially in the context of designing hierarchical materials. In particular, we emphasize the differences in the level of peptide design as an indicator of complexity within the targeted self-assembled materials and highlight future avenues for scientific and technological advances in this field.

Acylation of antimicrobial peptide-plasmid DNA vectors formulation for efficient gene delivery in cancer therapy

Antimicrobial peptides/DNA complexes were designed based on AMPs chensinin-1b and its corresponding lipo-chensinin-1b conjugated with an aliphatic acid with different chain lengths and therapeutic genes. The main goal of such a complex includes two aspects: first, antimicrobial peptides deliver therapeutic genes to cancer cells and genes expressed in targeted tissue for cancer gene therapy, and, second, the antimicrobial peptide kills cancer cells when used alone as an anticancer agent. This study presents a model composed of chensinin-1b and its lipo-chensinin-1b and eGFP plasmids, which were used as reporter genes, and the final peptide/eGFP plasmid complexes were analyzed by TEM and DLS. The gene transfection efficiency of the complex was evaluated by a microplate reader, FACS and CLSM. Compared with Lipo2000, the antimicrobial peptide showed specific selectivity for transfection against cancer cells and mammalian cells. The peptides chensinin-1b and lipo-chensinin-1b binding with the eGFP plasmid displayed optimal transfection efficiencies at a mass ratio of 8. In addition, PA-C1b can deliver p53-eGFP plasmids into MCF-7 cancer cells, and the proliferation of cells was inhibited and even caused cell death. Overall, PA-C1b was screened and found to have the highest transfection efficiency for gene delivery and good cellular uptake capability. The in vivo transfection ability of PA-C1b was investigated using a tumor-bearing mouse model, and the transfection efficiency reflected by the fluorescence of expressed GFP was determined by in vivo imaging. Conclusively, the antimicrobial peptide PA-C1b could be used as the nonviral vector with high efficiency for cancer gene therapy.

Synthesis and self-assembly of amphiphilic precision glycomacromolecules

Amphiphilic precision glycomacromolecules (APG) are synthesized using solid-phase synthesis and studied for their self-assembly behavior and as inhibitors of bacterial adhesion.

Peptide-based gene delivery vectors

Gene therapy as a strategy for disease treatment requires safe and efficient gene delivery systems that encapsulate nucleic acids and deliver them to effective sites in the cell.

Structure-Stability-Function Mechanistic Links in the Anti-Measles Virus Action of Tocopherol-Derivatized Peptide Nanoparticles

Measles remains one of the leading causes of child mortality worldwide and is re-emerging in some countries due to poor vaccine coverage, concomitant with importation of measles virus (MV) from endemic areas. The lack of specific chemotherapy contributes to negative outcomes, especially in infants or immunodeficient individuals. Fusion inhibitor peptides derived from the MV Fusion protein C-terminal Heptad Repeat (HRC) targeting MV envelope fusion glycoproteins block infection at the stage of entry into host cells, thus preventing viral multiplication. To improve efficacy of such entry inhibitors, we have modified a HRC peptide inhibitor by introducing properties of self-assembly into nanoparticles (NP) and higher affinity for both viral and cell membranes. Modification of the peptide consisted of covalent grafting with tocopherol to increase amphipathicity and lipophilicity (HRC5). One additional peptide inhibitor consisting of a peptide dimer grafted to tocopherol was also used (HRC6). Spectroscopic, imaging, and simulation techniques were used to characterize the NP and explore the molecular basis for their antiviral efficacy. HRC5 forms micellar stable NP while HRC6 aggregates into amorphous, loose, unstable NP. Interpeptide cluster bridging governs NP assembly into dynamic metastable states. The results are consistent with the conclusion that the improved efficacy of HRC6 relative to HRC5 can be attributed to NP instability, which leads to more extensive partition to target membranes and binding to viral target proteins.

Enhanced gene transfection efficiency by use of peptide vectors containing laminin receptor-targeting sequence YIGSR

This study presents the design and evaluation of a series of multifunctional peptides and their gene delivery abilities. The peptide sequences contained a cell-penetrating segment, six continuous histidine residues, a stearyl moiety and a laminin receptor-targeting segment. The YIGSR segment promoted cellular uptake through the interaction with laminin receptors on the surface of cells, which resulted in a great improvement in gene transfection efficiency. The conformation, particle size and zeta potential of peptide/DNA complexes were characterized via circular dichroism and dynamic light scattering. Their gene transfection efficiency was investigated by fluorescence-activated cell sorting and confocal microscopy. The transfection efficiency of the designed peptide vectors was higher than that of Lipo 2000. The peptide TAT-H₆-K(C₁₈)-YIGSR displayed transfection efficiencies at N/P ratios of 6, which was 3.5 and 7 times higher than that of Lipo 2000 in B16F10 and 293T cells, respectively. All peptides exhibited lower cytotoxicity than Lipo 2000 in B16F10 and 293T cells. In summary, the designed YIGSR-containing multifunctional peptide gene vectors promoted cellular uptake and gene transfection. Their in vivo transfection ability was investigated in zebrafish, and the transfection efficiency was determined by confocal microscopy and bioluminescence imaging. The peptide vectors, owing to their relatively short sequences and ease of functionalization, offer a promising approach for gene delivery because of their low cytotoxicity and high transfection efficiency.

Peptide amphiphiles with multifunctional fragments promoting cellular uptake and endosomal escape as efficient gene vectors

A series of peptides containing multiple functional fragments were designed as gene-delivery vectors with transfection efficiency comparable to Lipofectamine 2000.