Investigation of the automated solid-phase synthesis of a 38mer peptide with difficult sequence pattern under different synthesis strategies

Preparation, design, identification and application of self-assembly peptides from seafood: A review

Hydrogels formed by self-assembling peptides with low toxicity and high biocompatibility have been widely used in food and biomedical fields. Seafood contains rich protein resources and is also one of the important sources of natural bioactive peptides. The self-assembled peptides in seafood have good functional activity and are very beneficial to human health. In this review, the sequence of seafood self-assembly peptide was introduced, and the preparation, screening, identification and characterization. The rule of self-assembled peptides was elucidated from amino acid sequence composition, amino acid properties (hydrophilic, hydrophobic and electric), secondary structure, interaction and peptide properties (hydrophilic and hydrophobic). It was introduced that the application of hydrogels formed by self-assembled peptides, which lays a theoretical foundation for the development of seafood self-assembled peptides in functional foods and the application of biological materials.

Molecular farming for sustainable production of clinical-grade antimicrobial peptides

Antimicrobial peptides (AMPs) are emerging as next-generation therapeutics due to their broad-spectrum activity against drug-resistant bacterial strains and their ability to eradicate biofilms, modulate immune responses, exert anti-inflammatory effects and improve disease management. They are produced through solid-phase peptide synthesis or in bacterial or yeast cells. Molecular farming, i.e. the production of biologics in plants, offers a low-cost, non-toxic, scalable and simple alternative platform to produce AMPs at a sustainable cost. In this review, we discuss the advantages of molecular farming for producing clinical-grade AMPs, advances in expression and purification systems and the cost advantage for industrial-scale production. We further review how 'green' production is filling the sustainability gap, streamlining patent and regulatory approvals and enabling successful clinical translations that demonstrate the future potential of AMPs produced by molecular farming. Finally, we discuss the regulatory challenges that need to be addressed to fully realize the potential of molecular farming-based AMP production for therapeutics.

Automated Solid-Phase Peptide Synthesis

The development of solid-phase peptide synthesis by Bruce Merrifield paved the way for a synthesis carried out by machines. Automated peptide synthesis is a fast and convenient way of synthesizing many peptides simultaneously. This chapter tries to give a general guidance for the development of synthesis protocols for the peptide synthesizer. It also provides some suggestions for the modification of the synthesized peptides. Additionally, many examples of possible challenges during and after the synthesis are given in order to support the reader in finding the best synthesis strategy. Numerous references are given to many of the described matters.

Heterologous expression of the novel α-helical hybrid peptide PR-FO in Bacillus subtilis

PR-FO is a novel α-helical hybrid antimicrobial peptide (AMP) with strong antimicrobial activities and high stability, and the potential to develop into a new generation of antimicrobial agents. In this study, the encoded gene sequence of SMT3-PR-FO was designed and transformed into B. subtilis WB800N. Fusion proteins with concentrations of 16 mg L^-1 (SP_amyQ) and 23 mg L^-1 (SP_sacB) were obtained after purification by a Ni-NTA resin column. A total of 3 mg (SP_amyQ) and 4 mg (SP_sacB) of PR-FO with a purity of 90% was obtained from 1 L fermentation cultures. Recombinant PR-FO exhibited high inhibition activities against both gram-negative bacteria and gram-positive bacteria, and low haemolytic activity against human red blood cells. These results indicated that the rSMT3-PR-FO could be expressed under the guidance of SP_amyQ and SP_sacB, and the maltose-induced expression strategy might be a safe and efficient method for the soluble peptides production in B. subtilis.

Reprogramming biological peptides to combat infectious diseases

With the rapid spread of resistance among parasites and bacterial pathogens, antibiotic-resistant infections have drawn much attention worldwide. Consequently, there is an urgent need to develop new strategies to treat neglected diseases and drug-resistant infections. Here, we outline several new strategies that have been developed to counter pathogenic microorganisms by designing and constructing antimicrobial peptides (AMPs). In addition to traditional discovery and design mechanisms guided by chemical biology, synthetic biology and computationally-based approaches offer useful tools for the discovery and generation of bioactive peptides. We believe that the convergence of such fields, coupled with systematic experimentation in animal models, will help translate biological peptides into the clinic. The future of anti-infective therapeutics is headed towards specifically designed molecules whose form is driven by computer-based frameworks. These molecules are selective, stable, and active at therapeutic doses.

Sustainability Challenges in Peptide Synthesis and Purification: From R&D to Production

In recent years, there has been a growing interest in therapeutic peptides within the pharmaceutical industry with more than 50 peptide drugs on the market, approximately 170 in clinical trials, and >200 in preclinical development. However, the current state of the art in peptide synthesis involves primarily legacy technologies with use of large amounts of highly hazardous reagents and solvents and little focus on green chemistry and engineering. In 2016, the ACS Green Chemistry Institute Pharmaceutical Roundtable identified development of greener processes for peptide API as a critical unmet need, and as a result, a new Roundtable team formed to address this important area. The initial focus of this new team is to highlight best practices in peptide synthesis and encourage much needed innovations. In this Perspective, we aim to summarize the current challenges of peptide synthesis and purification in terms of sustainability, highlight possible solutions, and encourage synergies between academia, the pharmaceutical industry, and contract research organizations/contract manufacturing organizations.

Synthesis, 18F-labelling and radiopharmacological characterisation of the C-terminal 30mer of Clostridium perfringens enterotoxin as a potential claudin-targeting peptide

The cell surface receptor claudin-4 (Cld-4) is upregulated in various tumours and represents an important emerging target for both diagnosis and treatment of solid tumours of epithelial origin. The C-terminal fragment of the Clostridium perfringens enterotoxin cCPE_290-319 appears as a suitable ligand for targeting Cld-4. The synthesis of this 30mer peptide was attempted via several approaches, which has revealed sequential SPPS using three pseudoproline dipeptide building blocks to be the most efficient one. Labelling with fluorine-18 was achieved on solid phase using N-succinimidyl 4-[¹⁸F]fluorobenzoate ([¹⁸F]SFB) and 4-[¹⁸F]fluorobenzoyl chloride as ¹⁸F-acylating agents, which was the most advantageous when [¹⁸F]SFB was reacted with the resin-bound 30mer containing an N-terminal 6-aminohexanoic spacer. Binding to Cld-4 was demonstrated via surface plasmon resonance using a protein construct containing both extracellular loops of Cld-4. In addition, cell binding experiments were performed for ¹⁸F-labelled cCPE_290-319 with the Cld-4 expressing tumour cell lines HT-29 and A431 that were complemented by fluorescence microscopy studies using the corresponding fluorescein isothiocyanate-conjugated peptide. The 30mer peptide proved to be sufficiently stable in blood plasma. Studying the in vivo behaviour of ¹⁸F-labelled cCPE_290-319 in healthy mice and rats by dynamic PET imaging and radiometabolite analyses has revealed that the peptide is subject to substantial liver uptake and rapid metabolic degradation in vivo, which limits its suitability as imaging probe for tumour-associated Cld-4.

Soluble expression, purification and functional characterization of a coil peptide composed of a positively charged and hydrophobic motif

A de novo heterodimeric coiled-coil system formed by the association of two synthetic peptides, the Ecoil and Kcoil, has been previously designed and proven to be an excellent and versatile tool for various biotechnology applications. However, based on the challenges encountered during its chemical synthesis, the Kcoil peptide has been designated as a "difficult peptide". In this study, we explore the expression of the Kcoil peptide by a bacterial system as well as its subsequent purification. The maximum expression level was observed when the peptide was fused to thioredoxin and the optimized purification process consisted of three chromatographic steps: immobilized-metal affinity chromatography followed by cation-exchange chromatography and, finally, a reverse-phase high-performance liquid chromatography. This entire process led to a final volumetric production yield of 1.5 mg of pure Kcoil peptide per liter of bacterial culture, which represents a significant step towards the cost-effective production and application of coiled-coil motifs. Our results thus demonstrate for the first time that bacterial production is a viable alternative to the chemical synthesis of de novo designed coil peptides.