α-Aminoisobutyric acid modified protected analogues of β-amyloid residue 17–20: a change from sheet to helix

Supramolecular helical self-assembly of small peptides

In this highlight, we describe the construction of supramolecular single/double/triple-helical assemblies from small di/tri/tetrapeptides and their applications.

Glucagon-Like Peptide-1 Receptor Agonists and Strategies To Improve Their Efficiency

Type 2 diabetes mellitus (T2DM) is increasing in global prevalence and is associated with serious health problems (e.g., cardiovascular disease). Various treatment options are available for T2DM, including the incretin hormone glucagon-like peptide-1 (GLP-1). GLP-1 is a therapeutic peptide secreted from the intestines following food intake, which stimulates the secretion of insulin from the pancreas. The native GLP-1 has a very short plasma half-life, owning to renal clearance and degradation by the enzyme dipeptidyl peptidase-4. To overcome this issue, various GLP-1 agonists with increased resistance to proteolytic degradation and reduced renal clearance have been developed, with several currently marketed. Strategies, such as controlled release delivery systems, methods to reduce renal clearance (e.g., PEGylation and conjugation to antibodies), and methods to improve proteolytic stability (e.g., stapling, cyclization, and glycosylation) provide means to further improve the ability of GLP-1 analogs. These will be discussed in this literature review.

A novel self-assembling peptide with UV-responsive properties

A novel heptapeptide comprising Ile-Gln-Ser-Pro-His-Phe-Phe (IQSPHFF) identified and found to undergo self-assembly into microparticles in solution. To understand the effects of ultraviolet (UV) irradiation on the self-assembly process, IQSPHFF solutions were exposed to the UV light of 365 nm at room temperature. This exposure was found to have a profound effect on the morphology of the self-assembled aggregates, converting the microparticles to nanorod shapes. Circular dichroism and FTIR studies indicated distinct structural differences in the arrangements of the peptide moieties before and after UV irradiation. However, Mass spectrum analysis and high performance liquid chromatography of the peptide molecules before and after UV irradiation demonstrated that the chemical structure of IQSPHFF was not changed. UV-visible spectroscopy and fluorescence spectroscopy studies showed that the absorption peak both increased after UV irradiation. Overall, our data show that the heptapeptide with UV-responsive properties.

Self-assembled peptide microspheres for sustainable release of sulfamethoxazole

Porous peptide microspheres have been used for the loading and sustained release of the bacteriostatic antibiotic sulfamethoxazole.

A single-residue substitution inhibits fibrillization of Ala-based pentapeptides. A spectroscopic and molecular dynamics investigation

The aggregation properties of two Ala-based pentapeptides were investigated by spectroscopic techniques and molecular dynamics (MD) simulations. The two peptides, both functionalized at the N-terminus with a pyrenyl group, differ in the insertion of an α-aminoisobutyric acid residue at position 4. We showed that this single modification of the homo-peptide sequence inhibits the aggregation of the pentapeptide in aqueous solutions. Atomic force microscopy imaging revealed that the two peptides form mesoscopic aggregates of very different morphologies when deposited on mica. MD experiments showed that the two peptides have a very different propensity to form β-pleated sheet structures, as confirmed by our spectroscopic measurements. The implications of these findings for our understanding of the mechanism leading to the formation of amyloid structures, primary responsible for numerous neurodegenerative diseases, are also discussed.

Fabrication of hollow self-assembled peptide microvesicles and transition from sphere-to-rod structure

This paper presents the construction of hollow peptide microspheres and the mechanism of transition of microspheres to rod-like vesicles at low concentration. The tripeptides Boc-Phe-Maba-Phe-OMe 1 and Boc-Phe-Maba-Tyr-OMe 2, each of them containing a rigid m-aminobenzoic acid (Maba) template at the central position, forms microspheres at a concentration of 1.6 mM in methanol. At low concentration, these vesicular structures are fused through neck formation, and this leads to sphere-to-rod transition of vesicles. Sizes of these microspheres increase with increasing concentration. We have successfully characterized this transition by fluorescence spectroscopy, DLS, and electron microscopic study. The scanning electron microscopy clearly shows that these spheres are hollow. One important property of these microvesicular structures is the encapsulation of a potent anticonvulsant and mood stabilizing drug carbamazepine, which holds future promise to use these microvesicles as delivery vehicles.