Tuning the double lipidation of salmon calcitonin to introduce a pore-like membrane translocation mechanism.

A widespread strategy to increase the transport of therapeutic peptides across cellular membranes has been to attach lipid moieties to the peptide backbone (lipidation) to enhance their intrinsic membrane interaction. Efforts in vitro and in vivo investigating the correlation between lipidation characteristics and peptide membrane translocation efficiency have traditionally relied on end-point read-out assays and trial-and-error-based optimization strategies. Consequently, the molecular details of how therapeutic peptide lipidation affects it's membrane permeation and translocation mechanisms remain unresolved.

Development of Bifunctional, Raman Active Diyne-Girder Stapled α-Helical Peptides.

Stapled peptides are a unique class of cyclic α-helical peptides that are conformationally constrained via their amino acid side-chains. They have been transformative to the field of chemical biology and peptide drug discovery through addressing many of the physicochemical limitations of linear peptides. However, there are several issues with current chemical strategies to produce stapled peptides.

Quantitative live-cell imaging of lipidated peptide transport through an epithelial cell layer.

Oral drug delivery increases patient compliance and is thus the preferred administration route for most drugs. However, for biologics the intestinal barrier greatly limits the absorption and reduces their bioavailability. One strategy employed to improve on this is chemical modification of the biologic through the addition of lipid side chains.

Conformationally rigid pyrazoloquinazoline α-amino acids: one- and two-photon induced fluorescence.

The synthesis and photophysical properties of a new class of α-amino acid bearing a rigid pyrazoloquinazoline chromophore are described. Confromational constraint of the amino acid side-chains resulted in high emission quantum yields, while the demonstration of two-photon-induced fluorescence via near-IR excitation signifies their potential for sensitive bioimaging applications.

Synthesis and Fluorescent Properties of β-Pyridyl α-Amino Acids.

The preparation of a new class of β-pyridyl α-amino acid is described using a highly regioselective, ytterbium-catalyzed hetero-Diels-Alder reaction of enones with vinyl ethers followed by a modified Knoevenagel-Stobbe reaction as the key heterocycle forming steps. Investigation of the properties and applications of these amino acids showed that they could be utilized in solid phase peptide synthesis for the preparation of a biologically relevant hexapeptide, while pyridines bearing electron-rich substituents exhibited strongly fluorescent properties with high quantum yields and MegaStokes shifts. A solvatochromic study with the most fluorogenic amino acid, a p-methoxyphenyl analogue, revealed that this charge-transfer based chromophore is highly sensitive to solvent polarity with a bathochromic shift of 115 nm on changing from THF to phosphate-buffered saline.

Dipeptides as co-formers in co-amorphous systems.

Drug-amino acid co-amorphous systems have become increasingly well-investigated systems to improve dissolution rate of poorly water-soluble drugs. In this study, dipeptides were investigated as co-formers for co-amorphous systems based on the hypothesis that dipeptides might combine the inherent properties of the two included amino acids. Co-amorphization of the model drug mebendazole was investigated with five dipeptides, tryptophan-phenylalanine, phenylalanine-tryptophan, aspartic acid-tyrosine, histidine-glycine and proline-tryptophan.

Aspartame as a co-former in co-amorphous systems.

Co-amorphous drug delivery systems are a promising approach to improve the dissolution rate and therefore potentially the oral bioavailability of poorly-water soluble drugs. Several low molecular weight excipients, for instance amino acids, have previously been shown to stabilize the amorphous form and increase the dissolution rate of drugs. In this study, the feasibility of aspartame, a methyl ester of the aspartic acid-phenylalanine dipeptide, as a co-former was investigated and compared with the respective single amino acids, both alone and in combination.

Indoloazepinone-Constrained Oligomers as Cell-Penetrating and Blood-Brain-Barrier-Permeating Compounds.

Non-cationic and amphipathic indoloazepinone-constrained (Aia) oligomers have been synthesized as new vectors for intracellular delivery. The conformational preferences of the [l-Aia-Xxx] oligomers were investigated by circular dichroism (CD) and NMR spectroscopy. Whereas Boc-[l-Aia-Gly] -OBn oligomers 12 and 13 and Boc-[l-Aia-β -h-l-Ala] -OBn oligomers 16 and 17 were totally or partially disordered, Boc-[l-Aia-l-Ala] -OBn (14) induced a typical turn stabilized by C - and C -membered H-bond pseudo-cycles and aromatic interactions.

Solid-Phase Synthesis of Oxetane Modified Peptides.

Solid-phase peptide synthesis (SPPS) is used to create peptidomimetics in which one of the backbone amide C═O bonds is replaced by a four-membered oxetane ring. The oxetane containing dipeptide building blocks are made in three steps in solution, then integrated into peptide chains by conventional Fmoc SPPS. This methodology is used to make a range of peptides in high purity including backbone modified derivatives of the nonapeptide bradykinin and Met- and Leu-enkephalin.

Diversity-Oriented Peptide Stapling: A Third Generation Copper-Catalysed Azide-Alkyne Cycloaddition Stapling and Functionalisation Strategy.

The introduction of macrocyclic constraints in peptides (peptide stapling) is an important tool within peptide medicinal chemistry for stabilising and pre-organising peptides in a desired conformation. In recent years, the copper-catalysed azide-alkyne cycloaddition (CuAAC) has emerged as a powerful method for peptide stapling. However, to date CuAAC stapling has not provided a simple method for obtaining peptides that are easily diversified further.

Side Chain Cyclized Aromatic Amino Acids: Great Tools as Local Constraints in Peptide and Peptidomimetic Design.

Constraining the conformation of flexible peptides is a proven strategy to increase potency, selectivity, and metabolic stability. The focus has mostly been on constraining the backbone dihedral angles; however, the correct orientation of the amino acid side chains (χ-space) that constitute the peptide pharmacophore is equally important. Control of χ-space utilizes conformationally constrained amino acids that favor, disfavor, or exclude the gauche (-), the gauche (+), or the trans conformation.

Conformationally Constrained Peptidomimetics as Inhibitors of the Protein Arginine Methyl Transferases.

Protein arginine N-methyl transferases (PRMTs) belong to a family of enzymes that modulate the epigenetic code through modifications of histones. In the present study, peptides emerging from a phage display screening were modified in the search for PRMT inhibitors through substitution with non-proteinogenic amino acids, N-alkylation of the peptide backbone, and incorporation of constrained dipeptide mimics. One of the modified peptides (23) showed an increased inhibitory activity towards several PRMTs in the low μm range and the conformational preference of this peptide was investigated and compared with the original hit using circular dichroism and NMR spectroscopy.

Effects of zinc supplementation and zinc chelation on in vitro β-cell function in INS-1E cells.

Background: Zinc is essential for the activities of pancreatic β-cells, especially insulin storage and secretion. Insulin secretion leads to co-release of zinc which contributes to the paracrine communication in the pancreatic islets. Zinc-transporting proteins (zinc-regulated transporter, iron-regulated transporter-like proteins [ZIPs] and zinc transporters [ZnTs]) and metal-buffering proteins (metallothioneins, MTs) tightly regulate intracellular zinc homeostasis.