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Studies presenting visible-light-induced desulfurization of peptides containing a cysteine residue have been carried out. This transformation driven by light-emitting-diode-type light proceeds with high efficiency in an aqueous solution at room temperature and involves the use of a catalytic amount of photosensitizer, Rose Bengal. The procedure has been tested on model synthetic peptides, lysozyme C and α-crystallin, and successfully applied to a one-pot native chemical ligation (NCL)-desulfurization protocol.

We report the synthesis of N-capped peptides under mild conditions using the oxidative aminocarbonylation of aryl iodides and peptide esters as nucleophiles in the solution phase. Ex situ chloroform in chamber A generates CO, which diffuses to chamber B, which contains other reactants. This method offers N-capped peptides at 80 °C for 12 h. We synthesized 36 N-capped peptides using this method, including an anticancer drug bortezomib analogue, with an isolated yield ranging from 52 to 91%. The present method gives easy access to previously inaccessible N-capping groups, including heteroaromatic ring-capped groups, which enable robust analogue designs in peptide-based drug discovery.

In the realm of biology, peptide bonds are formed via reactive phosphate-containing intermediates, facilitated by compartmentalized environments that ensure precise coupling and folding. Herein, we use aminoacyl phosphate esters, synthetic counterparts of biological aminoacyl adenylates, that drive selective peptide bond formation through side chain-controlled reactivity and self-assembly. This strategy results in the preferential incorporation of positively charged amino acids from mixtures containing natural and non-natural amino acids during the spontaneous formation of amide bonds in water. Conversely, aminoacyl phosphate esters that lack assembly and exhibit fast reactivity result in random peptide coupling. By introducing structural modifications to the phosphate esters (ethyl vs. phenyl) while retaining aggregation, we are able to tune the selectivity by incorporating aromatic amino acid residues. This approach enables the synthesis of sequences tailored to the specific phosphate esters, overcoming limitations posed by certain amino acid combinations. Furthermore, we demonstrate that a balance between electrostatic and aromatic stacking interactions facilitates covalent self-sorting or co-assembly during oligomerization reactions using unprotected N-terminus aminoacyl phosphate esters. These findings suggest that self-assembly of abiotic aminoacyl phosphate esters can activate a selection mechanism enabling the departure from randomness during the autonomous formation of amide bonds in water., Competing Interests: Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

ADP-ribosylation is a complex post-translational modification involved in key physiological processes and associated with various health and disease states. The growing interest in ADP-ribosylation necessitates straightforward and efficient synthetic methods for the preparation of ADP-ribosylated peptides/proteins. In this study, we report a facile reaction between nicotinamide adenine dinucleotide (NAD + ) and alcohols promoted by a combination of ionic liquids, yielding up to 94 % with α : β ratios ranging from 88 : 12 to 99 : 1 and a switchable configuration selectivity. This method significantly simplifies the production of ADP-ribosylated peptides and proteins, enabling diverse applications. It allows detailed investigation of side-chain structure-activity relationships, facilitates two-step clickable conjugation of ADP-ribosyl groups to proteins, and, for the first time, enables non-enzymatic synthesis of well-defined ADP-ribosylated peptides/proteins from natural counterparts and NAD + ., (© 2025 Wiley-VCH GmbH.)

Chemical synthesis of complex peptides and proteins continues to play increasingly important roles in industry and academia, where strategies for covalent ligation of two or more peptide fragments to produce longer peptides and proteins in convergent manners have become critical. In recent decades, efficient and site-selective ligation strategies mediated by exploiting the biocatalytic capacity of nature's diverse toolkit (i.e., enzymes) have been widely recognized as a powerful extension of existing chemical strategies. In this review, we present a chronological overview of the development of proteases, transpeptidases, transglutaminases, and ubiquitin ligases. We survey the different properties between the ligation reactions of various enzymes, including the selectivity and efficiency of the reaction, the ligation "scar" left in the product, the type of amide bond formed (natural or isopeptide), the synthetic availability of the reactants, and whether the enzymes are orthogonal to another. This review also describes how the inherent specificity of these enzymes can be exploited for peptide and protein ligation., (© 2024 European Peptide Society and John Wiley & Sons Ltd.)

Interactions between aromatic side chains of amino acids stabilize the fold and assembly of short peptides. The aromatic π…π and C-H…π interactions have been widely explored in the design of short peptides with specific folding and aggregation patterns. In the present study, we investigated the effect of homologated phenylalanine side chains on the conformation and assembly of peptide helices through X-ray crystallographic structure determination and analysis of five pentapeptides. The parent peptide Boc-Phe-Aib-Aib-Leu-Phe-NHiPr (1) and its four variations were synthesized, in which either one or both of the Phe side chains have been modified by inserting one (homophenylalanine, hPhe; -CH 2 -CH 2 -C 6 H 5 ) or two (h 2 Phe; -CH 2 -CH 2 -CH 2 -C 6 H 5 ) additional CH 2 groups in the side chain, and their crystal structures were analyzed. The results show that intramolecular aromatic interactions are not present in the parent peptide but are present in the peptides containing the higher homologs of Phe. In peptides that did not show intramolecular aromatic interactions, the effect of increased length of the side chain of Phe residues manifested as intermolecular interactions leading to ordered packing in crystals. The results indicate the potential of hPhe and h 2 Phe residues to have aromatic interactions that could induce preferential folding and aggregation of peptides containing them., (© 2024 European Peptide Society and John Wiley & Sons Ltd.)

Protein-protein interactions (PPIs) are pivotal in regulating cellular functions and life processes, making them promising therapeutic targets in modern medicine. Despite their potential, developing PPI inhibitors poses significant challenges due to their large and shallow interfaces that complicate ligand binding. This study focuses on mimicking peptide loops as a strategy for PPI inhibition, utilizing synthetic peptide loops for replicating critical binding regions. This work explores turn-inducing elements and highlights the importance of proline in promoting favorable conformations for lactamization, yielding high-purity cyclic peptides. Notably, our one-pot method offers enhanced versatility and represents a robust strategy for efficient and selective macrolactamization, expanding the scope of peptide synthesis methodologies. This approach, validated through the synthesis of AAV capsid-derived loops, offers a robust platform for developing peptide-based therapeutics and highlights the potential of peptide macrocycles in overcoming PPI drug discovery challenges and advancing the development of new therapeutics.

Melanogenesis is a biochemical process that regulates skin pigmentation, which is crucial role in protecting against ultraviolet radiation. It is also associated with hyperpigmentation conditions such as melasma and age spots, which negatively impact aesthetics and self-confidence. Tyrosinase (TYR), a key enzyme in the melanogenesis pathway, catalyzes the biosynthesis of melanin in the skin. Inhibition of tyrosinase particularly by blocking its active site and preventing the binding of natural substrates such as tyrosine, can reduce melanin production, making it a promising therapeutic target for treating hyperpigmentation. Peptides have emerged as promising therapeutics to regulate melanogenesis by minimizing the side effects associated with conventional skin whitening therapeutics. This review is designed to offer a comprehensive analysis of current strategies in peptide design aimed at optimizing anti-melanogenic activity, by focusing on the role of molecular weight, polarity, and cyclization strategies in enhancing peptide efficacy and stability. It was found that optimal peptide size was within the range of 400-600 Da. The balance between hydrophilic and hydrophobic properties in peptides is crucial for effective TYR inhibition, as higher hydrophilicity enhances affinity for the TYR active site and stronger catalytic inhibition, while hydrophobicity can contribute through alternative mechanisms. Cyclization of peptides enhances their structural stability, serum resistance, and binding affinity while reducing toxicity. This process increases resistance to enzymatic degradation and improves target specificity by limiting conformational flexibility. Additionally, the rigidity and internal hydrogen bonding of cyclic peptides can aid in membrane permeability, making them more effective for therapeutic use. Peptide optimizations through size modification, polarity change, and cyclization strategies have been shown to be promising as reliable and safe agents for melanin inhibition. Future studies exploring specific amino acid in peptide chains are required to improve efficacy and potential clinical applications of these anti-melanogenic peptides as a hyperpigmentation treatment., Competing Interests: The authors declare that there is no conflict of interest in this work., (© 2025 Putri et al.)

Covering: 2016 to 2024Natural products, particularly cyclic peptides, are a promising source of bioactive compounds. Nonribosomal peptide synthetases (NRPSs) play a key role in biosynthesizing these compounds, which include antibiotic and anticancer agents, immunosuppressants, and others. Traditional methods of discovering natural products have limitations including cryptic biosynthetic gene clusters (BGCs), low titers, and currently unculturable organisms. This has prompted the exploration of alternative approaches. Synthetic-bioinformatic natural products ( syn -BNPs) are one such alternative that utilizes bioinformatics techniques to predict nonribosomal peptides (NRPs) followed by chemical synthesis of the predicted peptides. This approach has shown promise, resulting in the discovery of a variety of bioactive compounds including peptides with antibacterial, antifungal, anticancer, and proteasome-stimulating activities. Despite the success of this approach, challenges remain especially in the accurate prediction of fatty acid incorporation, tailoring enzyme modifications, and peptide release mechanisms. Further work in these areas will enable the discovery of many bioactive peptides that are currently inaccessible.

Ice formation poses a significant challenge across various fields, from industrial processes to biological preservation. Developing antifreeze agents and recognizing the antifreeze mechanism have gained considerable attention. Herein, a series of poly(l-methionine) derivatives, poly( S -carboxymethyl-l-methionine sulfonium) (PMetA), poly( S -methyl-l-methionine sulfonium chloride) (PMetM), and poly( S -carbamidomethyl-l-methionine sulfonium chloride) (PMetAM), with carboxyl, methyl, and acetamide groups, respectively, are synthesized and investigated for antifreeze. The relationship between the polymer structure and the ice recrystallization inhibition (IRI) activity is examined, suggesting that zwitterionic PMetA shows the highest IRI activity, about 27.0 ± 3.9% at 10 mg mL -1 relative to that of water. Results of low-field nuclear magnetic resonance and differential scanning calorimetry indicate that the IRI activity is associated with the activation energy for hydrogen bond breakage. PMetA exhibits acceptable cytocompatibility at 10.0 mg mL -1 and a good cryoprotective efficiency. This finding provides a valuable insight into the antifreeze mechanism, contributing to the development of potent cryoprotectants.

Current methods for the macrocyclization of phage-displayed peptides often rely on small molecule linkers that nonspecifically react with targeted amino acid residues. To expand tool kits for more regioselective macrocyclization of phage-displayed peptides, this study explores the unique condensation reaction between an N-terminal cysteine and nitrile along with the reactivity of an internal cysteine. Five 2-cyanopyrimidine derivatives were synthesized for this purpose and evaluated for their selective macrocyclization of a protein-fused model peptide. Among these, two novel linkers, 2-chloro- N -(2-cyanopyrimidin-5-yl)acetamide (pCAmCP) and 2-chloro- N -(2-cyanopyrimidin-4-yl)acetamide (mCAmCP), emerged as efficient molecules and were demonstrated to macrocyclize phage-displayed peptide libraries flanked by an N-terminal and an internal cysteine. Using these linkers to generate macrocyclic peptide libraries displayed on phages, peptide ligands for the ZNRF3 extracellular domain were successfully identified. One of the identified peptides, Z27S1, exhibited potent binding to ZNRF3 with a K D value of 360 nM. Notably, the selection results revealed distinct peptide enrichment patterns depending on whether mCAmCP or pCAmCP was used, underscoring the significant impact of linker choice on macrocyclic peptide identification. Overall, this study validates the development of two novel regioselective, small molecule linkers for phage display of macrocyclic peptides and highlights the benefits of employing multiple linkers during phage selections.

Inspired by biosynthetic peptides, we investigate the chiral recognition properties of adenylate amidate ( N -aa-AMP, a potential analog of 5'-aa-AMP) in prebiotic peptide formation. Our findings demonstrate that N -L-aa-AMP preferentially binds to L-aa, facilitating the formation of homochiral peptides, while N -D-aa-AMP shows a preference for D-aa, thereby achieving homochirality in peptide synthesis. Collectively, these results enhance our understanding of the evolutionary origins of homochirality on prebiotic Earth.

Decorating biomolecular building blocks, such as amino acids, to afford desired and tuneable photophysical/biophysical properties would allow chemical biologists to use them for several biotechnological and biosensing applications. While many synthetic methodologies have been explored in this direction, advantages provided by click-derived triazole moieties are second to none. However, since their discovery, click-mediated triazoles have been majorly utilised as linkers for conjugating biomolecules, creating materials with novel properties, such as polymers or drug conjugates. Despite exploring their profound role as linkers, click-mediated triazoles as an integral part of biomolecular building blocks have not been addressed. 1,2,3-Triazole, a transamide mimic, exhibits high aromatic stacking propensity, high associability with biomolecules through H-bonding, and high stability against enzymatic hydrolysis. Furthermore, triazoles can be considered donors useable for installation/modulation of the photophysics of a fluorophore. Therefore, triazole with a chromophoric unit may rightly be utilised as an integral part of biomolecular building blocks to install microenvironment-sensitive solvofluorochromic properties suitable for biological sensing, studying inter-biomolecular interactions and introducing novel physicochemical properties in a biomolecule. This review mainly focuses on the facets of click-derived triazole in designing novel fluorescent amino acids and peptides with a particular emphasis on those wherein triazole acts as an integral part of amino acids, i.e. the side chain, generating a new class of fluorescent unnatural triazolyl amino acids. Thus, fluorescent triazolyl unnatural amino acids, peptidomimetics with such amino acids and aliphatic/aromatic triazolyl amino acids as scaffolds for peptidomimetics are the central part. However, to start with, a brief history, followed by a discussion on various other relevant facets of triazoles as linkers in various fields ranging from therapeutics, materials science, diagnostics, and bioconjugation to peptidomimetics, is cited. Additionally, the possible roles of CuAAC-mediated triazoles in shaping the future of bioorganic chemistry, medicinal chemistry, diagnostics, nucleoside chemistry and protein engineering are briefly discussed.

The severe acute respiratory syndrome virus 2 (SARS-CoV-2) seriously impacted public health. The evolutionarily conserved viral chymotrypsin-like main protease (M pro ) is an important target for anti-SARS-CoV-2 drug development. Previous studies have shown that the eight N-terminal amino acids (N8) of SARS-CoV M pro are essential for its dimerization, and are used to design inhibitors against SARS-CoV M pro dimerization. Here, we established a simple readout assay using SDS-PAGE and Coomassie blue staining to measure inhibitory activity of N8 peptide derived from SARS-CoV-2 M pro . To optimize its inhibitory effect, we then modified the side-chain length, charge, and hydrophilicity of the N8 peptide, and introduced a mutated M pro recognition sequence. As a result, we obtained a series of potent peptide inhibitors against SARS-CoV-2 M pro , with N8-A24 being the most efficient with an IC 50 value of 1.44 mM. We observed that N8-A24 reduced M pro dimerization with an IC 50 value of 0.86 mM. Molecular docking revealed that N8-A24 formed hydrogen bond interactions with critical dimeric interface residues, thus inhibiting its dimerization and activity. In conclusion, our study not only discovers a series of peptide inhibitors targeting the SARS-CoV-2 M pro dimerization, but also provides a promising strategy for the rational design of new inhibitors against COVID-19., (© 2024 Wiley-VCH GmbH.)

Chemical protein synthesis enables access to proteins that would otherwise be difficult or impossible to obtain with traditional means such as recombinant expression. Chemoselective ligations provide the ability to join peptide segments prepared by solid-phase peptide synthesis. While native chemical ligation (NCL) is widely used, it is limited by the need for C-terminal thioesters with suitable reaction kinetics, properly placed native Cys or thiolated derivatives, and peptide segment solubility at low mM concentrations. Moreover, repetitive purifications to isolate ligated products are often yield-sapping, hampering efficiency and progress. In this work, we demonstrate the use of Controlled Activation of Peptides for Templated NCL (CAPTN). This traceless multi-segment templated NCL approach permits the one-pot synthesis of proteins by harnessing selective thioester activation and orthogonal conjugation chemistries to favor formation of the full-length ligated product while minimizing side reactions. Importantly, CAPTN provides kinetic enhancements allowing ligations at sterically hindered junctions and low peptide concentrations. Additionally, this one-pot approach removes the need for intermediate purification. We report the synthesis of two E. coli ribosomal subunits S16 and S17 enabled by the chemical tools described herein. We anticipate that CAPTN will expedite the synthesis of valuable proteins and expand on templated approaches for chemical protein synthesis., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The history of life's formation and the origin of its stereochemistry are nearly as multifaceted as the life itself. In this review, we focus on analyzing the step-by-step path leading to what we can define as "life" in parallel to what we know about the emergence of enantiomeric imbalance and subsequent transition to full homochirality. We start at the level of assembly of the building blocks of life from inorganic molecules and build up to the polymerization and formation of nucleic acids and peptides. We report and analyze different theories at various stages of this development and try to elucidate the most plausible theory., (© 2024 The Authors. Chemistry - An Asian Journal published by Wiley-VCH GmbH.)

Peptides have attracted great interest as platforms for the design of nanocomposite hydrogels due to their distinct bioactivity, biofunctionality and biocompatibility. Previously, we have reported on a family of peptides that self-assembled to form stabilised three-dimensional hydrogel networks, displaying potent antimicrobial activity. In this paper, we report on the use of these hydrogelator sequences and their analogues as stabilisers and growth controllers to synthesise anisotropic gold nanoparticles (AuNPs) of different sizes and shapes. In particular, hollow spherical nanoparticles were obtained for HG2.81-AuNPs, whereas hexagonal nanoparticles were observed for TOH_1N-AuNPs and PentaOH-AuNPs in their respective hydrogel networks. The PentaOH-AuNPs' hydrogel exhibited excellent results with high antimicrobial potency against Staphylococcus aureus and Pseudomonas aeruginosa ATCC 27853 and negligible cytotoxicity. On the other hand, TOH_1N-AuNPs showed no antibacterial activity and no cytotoxicity, demonstrating the versatility of these peptides. This work gives credence towards the development of these materials towards further applications such as in tissue culture technology and wound dressing materials., (© 2024 The Author(s). Journal of Peptide Science published by European Peptide Society and John Wiley & Sons Ltd.)

We report the development of a new electron-rich aniline (ERA)-based cleavable linker. Anilines can be incorporated into peptides during SPPS and are stable to most reaction conditions. ERA-containing peptides can be cleaved rapidly in the presence of oxidants, such as DDQ, CAN, and NaIO 4 , in 30 min at room temperature. The compatibility of these conditions is demonstrated on peptides containing natural and unnatural amino acids. While the cleavages of other oxidatively labile linkers is known to cause decomposition of Tyr and Trp, these sensitive residues are stable to DDQ oxidations. An ERA-linker also enables the capture and release of a biotinylated peptide from immobilized streptavidin. ERA-linkers may serve as an excellent tool for peptide library screening applications., Competing Interests: Declaration of competing interest The authors declare no financial interests or personal relationships that are potential competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Membranes that destroy anticancer peptides can bind to negatively charged cancer cell membranes through electrostatic interactions, destroying their functions and leading to cancer cell necrosis. Temporin-1CEa, obtained from the skin secretions of the Chinese frog Rana chensinensis, is an anticancer peptide with 17 amino acid residues that exhibits concentration-dependent cytotoxicity against a variety of cancer cell lines, although it has no obvious cytotoxicity to normal HUVECs. In this work, we designed and synthesized 12 derivative peptides through double-cysteine scanning of temporin-1CEa-truncated peptides. Most of these peptides had greater anticancer activity than the lead peptide temporin-1CEa. Among these derivative peptides, Nu-7 had the strongest anticancer activity. Nu-7 has a greater α-helicity than does temporin-1CEa. We connected Nu-7 to podophyllotoxin through a reduction-responsive linker to obtain Nu-7-1, which showed better anticancer activity than free podophyllotoxin. Nu-7-1 was less toxic to HUVECs and had low hemolytic activity at therapeutic concentrations (although Nu-7-1 showed hemolytic activity at 100 μM). Nu-7-1 functions through two mechanisms: damage to cell membranes and promotion of cell apoptosis. Nu-7-1 is less toxic to normal HUVECs than is podophyllotoxin and shows better safety. In summary, we carried out a series of modifications on temporin-1CEa, among which the anticancer activity of Nu-7-1 was significantly improved compared with that of the lead peptide temporin-1CEa, providing a useful reference for the structural modification of anticancer peptides., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

One important functional food ingredient today, valued for its health properties and ability to prevent disease, is bee pollen, which comprises a combination of nectar, pollen from plants, and the secretions of bees. In this research, the tyrosinase (TYR) inhibiting abilities of the peptides derived from bee pollen protein hydrolysates are investigated. Various proteases were utilized to generate these peptides, followed by testing at different concentrations. Tyrosinase inhibition activity was detected in all cases, while the hydrolysate drawn from 5.0% w/v neutrase exhibited the best IC 50 value and was thus investigated further via ultrafiltration to separate the active fractions. The highest potential for tyrosinase inhibition was recorded for the fractions below 0.65 kDa. Subsequent purification steps via SEC and RP-HPLC led to the identification of the VDGYPAAGY (named VY-9) peptide via LC-Q-TOF-MS/MS in fraction F 1-2 , known for its non-toxic and hydrophobic characteristics albeit poor water solubility. The synthesized VY-9 peptide demonstrated competitive inhibition, with IC 50 values of 0.55 ± 0.03 µM for mono-phenolase and 2.54 ± 0.06 µM for di-phenolase activities, as confirmed by molecular docking analysis revealing dominant hydrogen bond interactions with TYR. Effective concentrations of 0.2-1.6 µM of VY-9 showed negligible cytotoxicity in B16F10 cells. Melanin synthesis suppression was examined via qRT-PCR, and western blot in MITF, TYR, TRP-1, and TRP-2. Cell death in zebrafish embryos was evaluated in vivo using a toxicity assay which revealed no significant influence from VY-9, while anti-melanogenic effects were observed when the concentration was 4 µM, suggesting bee pollen-derived peptides' potential in cosmetic and pharmaceutical depigmentation applications., Competing Interests: Declarations. Competing interests: The authors declare no competing interests. Ethical approval: We confirm that all methods were carried out in accordance with the relevant guidelines and regulations by including a statement to that effect in the Methods section. Plant experimental research, including plant material collection, complies with relevant institutional, national, and international guidelines and legislation., (© 2024. The Author(s).)

Scorpion venom contains various bioactive peptides, many of which exhibit insecticidal activity. The majority of these peptides have a cystine-stabilized α-helix/β-sheet (CSαβ) motif. In addition to these peptides, scorpion venom also contains those with a cystine-stabilized α-helix/α-helix (CSαα) motif, which are known as κ-KTx peptides. Some of these peptides show weak inhibitory activity on mammal potassium channels, but, in many cases, their biological activity remained unknown. In this study, with the aim of discovering novel insecticidal peptides, we synthesized five peptides, which were predicted to adopt a CSαα motif, identified from the venom of the scorpion Liocheles australasiae , and measured their insecticidal activity. As a result, one of the peptides, named LaIT5, exhibited significant insecticidal activity. To the best of our knowledge, this is the first report of insecticidal peptides with a CSαα motif. Furthermore, we synthesized its analogs based on sequence comparisons with other inactive CSαα-motif peptides to identify amino acid residues important for its insecticidal activity. The results indicate that two consecutive His residues at the central region of LaIT5 are particularly important for the activity. Since LaIT5 did not show any toxicity against mice, it was concluded that its action is selective for insects.

Biologically produced protein drugs are generally susceptible to degradation by proteases and often exhibit immunogenicity. To address this issue, mirror-image peptide/protein binders consisting of D-amino acids have been developed so far through the mirror-image phage display technique. Here, we develop a mirror-image protein binder derived from a monobody, one of the promising protein scaffolds, utilizing two notable technologies: chemical protein synthesis and TRAP display, an improved version of mRNA display. A sequential workflow of initial screening followed by affinity maturation, facilitated by TRAP display, generates an L-monobody with high affinity (K D  = 1.3 nM) against monocyte chemoattractant protein-1 (MCP-1) D-enantiomer. The chemically synthesized D-monobody demonstrates strong and specific binding to L-MCP-1 and exhibits pharmaceutically favorable properties such as proteolytic resistance, minimal immune response, and a potent inhibitory effect on MCP-1-induced cell migration. This study elevates the value of mirror-image peptide/protein binders as an alternative modality in drug discovery., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Peptide modification provides opportunities to afford peptides with designed functions. Among the proteogenic amino acids, tryptophan represents an ideal and attractive target for peptide modification because of the exclusive chemical reactivity of its unique indole structure. Herein, we reported an indole C2 position-selective and transition-metal-free modification approach for indole derivatives and tryptophan-containing peptides by triazine derivatives via triflic acid activation and that the incorporated functional group could act as an orthogonal handle for further bioconjugation via an inverse electron demand Diels-Alder reaction.

Herein, we report a Rh(III)-catalyzed triple C-H activation-annulation of Phe-based peptides with alkynes for the preparation of fluorescent peptides. The robustness of this protocol is reflected by a broad substrate scope, high atom- and step-economy, and excellent chemo- and site-selectivity. An in situ generated polycyclic aromatic hydrocarbon carbocation as a fluorophore exhibits good fluorescence properties (maximum emission wavelength up to 628 nm) and low cell cytotoxicity. The synthetic utility of this method is further demonstrated by versatile product applications in bioconjugation with the protein BSA and specifically targeting lysosomes and mitochondria of live mammalian cells.

This study focuses on investigating the use of β-cyclodextrin (β-CyD) derivatives as additives in continuous flow peptide synthesis, with particular emphasis on challenging sequences such as the Jung-Redemann decapeptide and the 42-residue amyloid β polypeptide [Aβ(1-42)]. The efficacy of the OH-free β-CyD and two of its derivatives (Ac-β-CyD and HP-β-CyD) is compared with alternative, state-of-the-art synthetic methods, including the widely used and recently improved pseudoproline monomer technique, e.g., Ser(ΨPro). Our results show that the use of β-CyD as an additive results in a significant (8-19%) increase in the purity of the crude polypeptide compared to that determined by our reference method. The chromatograms determined by LC-MS were deconvoluted to estimate the more precise purity of the crude products, and we found that the improvement is greater when the free OH β-CyD is used and moderate when the acetyl-β-CyD or the 2-hydroxypropyl-β-CyD derivatives are used. We have found that the free CyD gives an improvement comparable to that achieved with the Ser(ΨPro) derivative.

Human Immunodeficiency Virus (HIV) has continued to endanger human health for decades and has a substantial impact on global health defence. Peptide-based fusion inhibitors, as an integral part of Highly Active Anti-Retroviral Therapy (HAART), are effective in preventing and controlling the AIDS epidemic. Nevertheless, the current market leader, Enfuvirtide, is facing numerous challenges in clinical application. We herein devised a cutting-edge development strategy leveraging SWISS-MODEL and HDOCK, enabling the design of artificial N-peptides. The most active compound, IZNP02QE, surpassed the positive control by demonstrating remarkable nanomolar-level inhibitory activity against HIV-1. Mechanistic investigations unveiled IZNP02QE's ability to disrupt the crucial endogenous 6-helix bundle (6-HB) by forming heteropolymers, underscoring its potential as a novel anti-HIV-1 agent. This work not only pioneers a novel design methodology for N-peptides but also opens up the possibility of a CADD strategy for designing peptide-based fusion inhibitors.

Fluorescent unnatural amino acids give biochemists, biophysicists, and bioengineers new ways to probe the properties of proteins and peptides. Here, the synthesis of acridon-2-ylalanine (Acd) is optimized for large-scale production to enable ribosomal incorporation through genetic code expansion (GCE), and fluorenylmethoxycarbonyl (Fmoc)-protected Acd is prepared for solid-phase peptide synthesis (SPPS). We demonstrate the utility of Acd in several applications: first, Acd quenching by Tyr is used in the design of fluorescent protease sensors made by SPPS. Second, we demonstrate Acd incorporation into a lanthanide-binding peptide that is generated either by GCE or by SPPS and demonstrate the utility of Acd for sensitizing the emission of Eu 3+ . Finally, Acd is inserted into the intrinsically disordered protein, α-synuclein, using GCE and used to study ion binding and aggregation.

Solid-phase peptide synthesis (SPPS) and native chemical ligation (NCL) are powerful methods for obtaining peptides and proteins that are otherwise inaccessible. Nonetheless, numerous sequences are difficult to prepare via SPPS, and cleaved peptides often have low aqueous solubility. To address these challenges, we developed a "Synthesis Tag" consisting of six arginines connected to the target sequence via a cleavable MeDbz linker. "SynTag" effectively improves batch- and flow-SPPS of "difficult sequences", enhances the solubility of the cleaved peptides, and provides direct access to native sequences by hydrolysis, or peptide thioesters for NCL. We demonstrate its utility in the first chemical synthesis of the MYC transactivation domain with a single NCL. We envisage SynTag to become a broadly applicable tool that enables the synthesis and study of previously unattainable peptides and proteins.

The continuous development of click reactions with new connecting linkage is crucial for advancing the frontiers of click chemistry. Selenium-nitrogen exchange (SeNEx) chemistry, a versatile chemistry in click chemistry, represents an all-encompassing term for nucleophilic substitution events that replace nitrogen at an electrophilic selenium(II) center, enabling the flexible and efficient assembly of linkages around a Se(II) core. Several SeNEx chemistries have been developed inspired by the biochemical reaction between Ebselen and cysteine residue, and demonstrated significant potential in on-plate nanomole-scale parallel synthesis, selenium-containing DNA-encoded library (SeDEL) synthesis, as well as peptide and protein bioconjugation. This concept aims to present the origins, advancements, and applications of selenium(II)-nitrogen exchange (SeNEx) chemistry while also outlining the potential directions for future research in this field., (© 2024 Wiley-VCH GmbH.)

Disulfide-bonded peptides and proteins, including hormones, toxins, growth factors, and others, are abundant in living organisms. These molecules play crucial physiological roles such as regulating cell and organism growth, development, and metabolism. They have also found widespread applications as drugs or tool molecules in biomedical and pharmaceutical research. However, the chemical synthesis of disulfide-bonded proteins is complicated by the challenges associated with their folding. This review focuses on the latest advancements in disulfide-bonded peptide and protein folding technologies. Particularly, it highlights biomimetic folding strategies that emulate the naturally occurring oxidative folding processes in nature. These strategies include chaperone-assisted folding, glycosylation-assisted folding, and organic-based oxidative folding methods. The review also anticipates future directions in folding technology. Such research offers innovative approaches for the chemical synthesis of complex proteins that are otherwise difficult to fold., (© 2024 Wiley-VCH GmbH.)

Adenosine diphosphate (ADP)-ribosylation is a ubiquitous post-translational modification that regulates vital biological processes like histone reorganization and DNA-damage repair through the modification of various amino acid residues. Due to advances in mass-spectrometry, the collection of long-known ADP-ribose (ADPr) acceptor sites, e. g. arginine, cysteine and glutamic acid, has been expanded with serine, tyrosine and histidine, among others. Well-defined ADPr-peptides are valuable tools for investigating the exact structures, mechanisms of action and interaction partners of the different flavors of this modification. This review provides a comprehensive overview of synthetic and chemoenzymatic methodologies that enabled the construction of peptides mono-ADP-ribosylated on various amino acids, and close mimetics thereof., (© 2024 The Authors. ChemBioChem published by Wiley-VCH GmbH.)

Orphan nuclear estrogen-related receptor γ (ERRγ) has been recognized as a potential therapeutic target for cancer, inflammation and metabolic disorder. The ERRγ contains a regulatory AF2 helical tail linked C-terminally to its ligand-binding domain (LBD), which is a self-binding peptide (SBP) and serves as molecular switch to dynamically regulate the receptor alternation between active and inactive states by binding to and unbinding from the AF2-binding site on ERRγ LBD surface, respectively. Traditional ERRγ modulators are all small-molecule chemical ligands that can be classified into agonists and inverse agonists in terms of their action mechanism; the agonists stabilize the AF2 in ABS site with an agonist conformation, while the inverse agonists lock the AF2 out of the site to largely abolish ERRγ transcriptional activity. Here, a class of ERRγ peptidic antagonists was described to compete with native AF2 for the ABS site, thus blocking the active state of AF2 binding to ERRγ LBD domain. Self-inhibitory peptide was derived from the SBP-covering AF2 region and we expected it can rebind potently to the ABS site by reducing its intrinsic disorder and entropy cost upon the rebinding. Hydrocarbon stapling was employed to do so, which employed an all-hydrocarbon bridge across the [i, i + 4]-anchor residue pair in the N-terminal, middle or C-terminal region of the self-inhibitory peptide. As might be expected, it is revealed that the stapled peptides are good binders of ERRγ LBD domain and can effectively compete with the native AF2 helical tail for ERRγ ABS site, which exhibit a basically similar binding mode with AF2 to the site and form diverse noncovalent interactions with the site, thus conferring stability and specificity to the domain-peptide complexes., (© 2024 Wiley Periodicals LLC.)

Light-controlled triggering of materials requires efficient embedding of molecular photoswitches into larger molecules. We herein present the synthesis of two new building blocks for the synthesis of photoswitchable peptides, embedding spiropyranes as a central unit into peptide-backbones via a novel, yet unreported approach. The synthesis presented here allows us to embed spiropyranes directly into solid-phase peptide synthesis (SPPS), further describing the resulting photophysical properties of the as-prepared photoswitchable peptides.

The ability for amino acid residues to bind metals underpins the functions of metalloproteins to conduct a plethora of critical processes in living organisms as well as unnatural applications in the fields of catalysis, sensing and medicinal chemistry. The capability to access metal-binding peptides heavily relies on the ability to generate appropriate building blocks. This review outlines recently developed strategies for the synthesis of metal binding non-proteinogenic amino acids. The chemistries to access, as well as to incorporate these amino acids into peptides is presented herein.

A biotinylated helical aromatic oligoamide foldamer equivalent in size to a 24mer peptide was designed without any prejudice other than to display various polar and hydrophobic side chains at its surface. It was synthesized on solid phase, its P - and M -helical conformers were separated by HPLC on a chiral stationary phase, and the solid state structure of a non-biotinylated analogue was elucidated by X-ray crystallography. Pull-down experiments from a yeast cell lysate using the foldamer as a bait followed by proteomic analysis revealed potential protein binding partners. Three of these proteins were recombinantly expressed. Biolayer interferometry showed submicromolar binding demonstrating the potential of a given foldamer to have affinity for certain proteins in the absence of design considerations. Yet, binding selectivity was low in all three cases since both P - and M -conformers bound to the proteins with similar affinities.

For protein analysis, the current peptide-based probes rely almost on the specific recognition of the protein while neglecting the potential influence of the environment near the protein. Herein, we propose that to achieve high recognition of transmembrane protein integrin α v β 3 , the interactions from the membrane substrate could be helpful. Moreover, to guarantee the additive effect of different interactions, the cis and trans isomers of peptide-based probes are distinguished. In detail, we synthesized the peptide-conjugated cis / trans isomers ( cis -RTP and trans -RTP) by modifying the Arg-Gly-Asp (RGD)-targeting peptide and palmitic acid-conjugated Arg-Arg-Arg-Arg (Pal-RRRR) peptide to the two ends of the molecular scaffold-tetraphenylethene derivative. Due to the difference in spatial structure, isothermal titration calorimetry and simulation experiments demonstrated that cis -RTP can bind more stably to integrin α v β 3 than trans -RTP. As a result, cis -RTP has shown more excellent properties in inhibiting cell migration and killing cells by regulating actin and extracellular signal-regulated kinase. Unlike the existing probe design for protein, this study provides a concept of microenvironment-helpful recognition and a promising strategy of cis/trans isomers to modulate the interaction between proteins and probes.

Bone diseases are medical conditions caused by the loss of bone homeostasis consecutive to increased osteoclast activity and diminished osteoblast activity. The mevalonate pathway (MVA) is crucial for maintaining this balance since it drives the post-translational prenylation of small guanosine triphosphatases (GTPases) proteins. Farnesyl pyrophosphate synthase (FPPS) plays a crucial role in the MVA pathway. Consequently, in the treatment of bone-related diseases, FPPS is the target of FDA-approved nitrogen-containing bisphosphonates (N-BPs), which have tropism mainly for bone tissue due to their poor penetration in soft tissues. The development of inhibitors targeting the FPPS enzyme has garnered significant interest in recent decades due to FPPS's role in the biosynthesis of cholesterol and other isoprenoids, which are implicated in cancer, bone diseases, and other conditions. In this study, we describe a multidisciplinary approach to designing novel FPPS inhibitors, combining computational modeling, biochemical assays, and biophysical techniques. A series of peptides and phosphopeptides were designed, synthesized, and evaluated for their ability to inhibit FPPS activity. Molecular docking was employed to predict the binding modes of these compounds to FPPS, while Surface Plasmon Resonance (SPR) and Nuclear Magnetic Resonance (NMR) spectroscopy experiments - based on Saturation Transfer Difference (STD) and an enzymatic NMR assay - were used to measure their binding affinities and kinetics. The biological activity of the most promising compounds was further assessed in cellular assays using murine colorectal cancer (CRC) cells. Additionally, genomics and metabolomics profiling allowed to unravel the possible mechanisms underlying the activity of the peptides, confirming their involvement in the modulation of the MVA pathway. Our findings demonstrate that the designed peptides and phosphopeptides exhibit significant inhibitory activity against FPPS and possess antiproliferative effects on CRC cells, suggesting their potential as therapeutic agents for cancer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Nowadays, peptidomimetics are widely studied, being useful tools in drug discovery and medicinal chemistry. The coupling between a carboxylic acid with an amine to form a peptide bond is the most common reaction to obtain peptides/peptidomimetics. In this work, we have investigated an innovative metal-free photoredox-catalyzed carbamoylation to form peptidomimetics thanks to the reaction between dihydropyridines functionalized with amino acids (or peptide sequences) and differently functionalized imines. As the organic photocatalyst, we used 4CzIPN, a donor-acceptor cyanoarene vastly used in photoredox catalysis. By easily modulating the amino acid (or peptide sequence), which is directly attached to the dihydropyridine, we proposed this key-reaction as new valuable method to obtain peptidomimetics, in situ building the not-natural portion of the sequence. Moreover, we successfully employed this methodology in solid phase peptide synthesis, both inserting the new photoredox-generated amino acid at the end or in the middle of the sequence. Peptides with different lengths and secondary structures were prepared, proving the success of this approach, even in sterically hindered environment. Herein, to the best of our knowledge, we describe the first photocatalytic protocol which allows the building of the peptide backbone, with the possibility of simultaneously inserting a non-coded amino acid in the sequence., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

The field of electrogenerated chemiluminescence (ECL) biosensing has witnessed remarkable growth, emphasizing the need for precise detection of biomarkers. The synthesis approach of peptide-based signal probe with high recognition ability and high ECL efficiency is a significant issue in the ECL biosensing. Here, a heavily labeled signal probe was synthesized for ECL peptide-based biosensing tactic by using a new aldehyde bearing cyclometalated Ir(III) complex ([Ir(bt) 2 (bpy-CHO)PF 6 (bt=2-phenylbenzothiazole, bpy-CHO=4'-methyl-[2,2'-bipyridine]-4-carbaldehyde, denoted as Ir1) as ECL signal reagent and streptavidin (SA) as carrier protein. One ECL peptide-based biosensing method was exemplified for the detection of matrix metalloproteinase 2 (MMP-2) by using Ir1 labeled SA (SA-Ir1) as heavily labeled signal probe and biotinylated peptide as molecular recognition substrate. MMP-2 was sensitively detected in the range from 5 to 100 ng/mL with a detection limit of 1.5 ng/mL. Importantly, two detection modes differing in the order of cleavage recognition by MMP-2 and signal transduction with SA-Ir1 were compared for the first time. First cleavage and second signal transduction were proposed to be beneficial to sensitive detection of target, which provides some ideas for biomarker diagnostics in disease screening at an early stage., (© 2024 Wiley-VCH GmbH.)

Studies of the structure and dynamics of oligomeric aggregates of amyloidogenic peptides pose challenges due to their transient nature. This concept article provides a brief overview of various nucleation mechanisms with reference to the classical nucleation theory and illustrates the advantages of incubating amyloidogenic peptides in reverse micelles (RMs). The use of RMs not only facilitates size regulation of oligomeric aggregates but also provides an avenue to explore protein-protein interactions among the oligomeric aggregates of various amyloidogenic peptides. Additionally, we envision the feasibility of preparing brain tissue-derived oligomeric aggregates using RMs, potentially advancing the development of monoclonal antibodies with enhanced potency against these pathological species in vivo., (© 2024 Wiley-VCH GmbH.)

Diazo peptides have been described earlier, however, due to their high reactivity have not been broadly used until today. Here, we report the preparation, properties, and applications of chemically stable internal diazo peptides. Peptidyl phosphoranylidene-esters and amides were found to react with triflyl azide primarily to novel 3,4-disubstituted triazolyl-peptides. Nonaflyl azide instead furnished diazo peptides, which are chemically stable from pH 1-14 as amides and from pH 1-8 as esters. Thus, diazo peptides prepared by solid phase peptide synthesis were stable to final deprotection with 95 % trifluoroacetic acid. Diazo peptides with the recognition sequence of caspase-3 were identified as specific, covalent, and irreversible inhibitors of this enzyme at low nanomolar concentrations. A fluorescent diazo peptide entered living cells enabling microscopic imaging and quantification of apoptotic cells via flow cytometry. Thus, internal diazo peptides constitute a novel class of activity-based probes and enzyme inhibitors useful in chemical biology and medicinal chemistry., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Currently non-protein amino acids and synthetic peptides are widely used as blocks in drug design. Many proteases are of great interest for pharmacology due to their key role in various pathologies. Bacterial collagenase (EC 3.4.24.3) is quite an attractive target for drug development as the inhibitors of bacterial collagenolytic protease may stop propagation of diseases caused by infections. The interaction of peptides containing unusual amino acids with Clostridium histolyticum collagenase has been evaluated by molecular docking followed by the measurement of enzyme inhibition by selected compounds. According to the docking analysis, 4 compounds were selected and synthesized for further research. Measurement of enzyme activity revealed that all tested compounds inhibited collagenase activity with IC50 values ranging within 1.45-2.08 μM. The antibacterial activity of synthesized compounds against some resistant strains was characterized by MICs values ranging within 4.6-9.2 μg/ml.

Oligourea foldamers are known to fold into 2.5-helices, stabilized by three-centered hydrogen bonds, which makes them conformationally more rigid than peptides. Nevertheless, the folding propensity and conformational stability in solution depend on the length of the oligomer, as well as the temperature, solvent, and so forth. In the peptide field, there are many approaches known for constraining the backbone in the folded conformation, including the stapling of side chains by disulfide bridges, lactam formation, ring closing metathesis reaction, and others. In this work, we linked side chains by lactam bridges of short oligoureas (four residues), containing Glu- and Lys-like residues. The designed oligoureas differed in the position of the Glu-like residue. Next, the conformational properties of linear and cyclic compounds were studied in protic solvent (methanol) by nuclear magnetic resonance and circular dichroism. Importantly, it was discovered that larger macrocycles (24-membered) are more tolerated with respect to the helical turn than smaller macrocycles (19-membered) under the studied conditions., (© 2024 European Peptide Society and John Wiley & Sons Ltd.)

Antisense oligonucleotides have been developed as therapeutic compounds, with peptide nucleic acid (PNA) emerging as a promising nucleic acid mimic for antimicrobial applications. To be effective, PNAs must be internalized into bacterial cells, as they are not naturally absorbed. A strategy to improve PNA membrane penetration and cellular uptake involves covalently conjugating them to cell-penetrating peptides. However, these membrane-active peptides can exhibit cytotoxicity, and their efficiency as PNA carriers needs to be enhanced. Therefore, we explored new peptide-PNA conjugates and their linkers to understand how they affect PNA uptake into bacteria. We conjugated PNA to two peptides, anoplin and (KFF) 3 K, along with their structurally stabilized hydrocarbon-stapled derivatives, and evaluated their transport into various bacterial strains. The PNA sequence targeted bacterial mRNA encoding the essential acyl carrier protein. As linkages, we used either a non-cleavable 8-amino-2,6-dioxaoctanoyl (ethylene glycol, eg1) linker or a reducible disulfide bridge. We found that the hydrocarbon-stapled peptides did not enhance PNA delivery, despite the strong inner- and outer-membrane-penetrating capabilities of the standalone peptides. Additionally, the disulfide bridge linkage, which is cleavable in the bacterial cytoplasm, decreased the antimicrobial activity of the peptide-PNA conjugates. Notably, we identified anoplin as a new potent PNA carrier peptide, with the anoplin-eg1-PNA conjugate demonstrating antibacterial activity against E. coli and S. Typhimurium strains in the 2-4 µM range., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

In recent decades, peptides have attracted significant attention not only from Academia but also from big Pharma as novel potential therapeutic compounds [...].

Tuberculosis is a major global health problem caused by Mycobacterium tuberculosis and the increase in drug resistance is driving the need for new treatments. Today, various approaches are being applied in the development of drugs for the treatment of tuberculosis. Computer-aided drug design (CADD) enables the prediction of pharmacological efficacy for potential drug molecules during the design process. Thus, new therapeutic compounds can be developed that are more potent, less toxic and have fewer side effects than existing drugs. In this study, we investigated the in vitro activities of AKVUAM-1 and AKVUAM-2 synthetic peptides designed in silico by computer-aided drug design method to inhibit the interaction between M. tuberculosis outer membrane protein Cpn T and macrophage surface receptor CR-1 and Surfactant D protein. Notably, these synthetic peptides do not show cytotoxic effect on normal lung tissue and do not kill M. tuberculosis directly. The MIC values for AKVUAM-1 were higher than 512 μg/ml for all bacterial strains except IST-16 strain (128 μg/ml). According to our results, AKVUAM-1 and AKVUAM-2 synthetic peptides have the potential to be successful candidates for investigating their potential to block macrophage entry of bacilli as targeted., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

A series of isatin derivatives which could inhibit colorectal cancer (CRC) were synthesized. Among those compounds, 5B exhibited good inhibitory activity of CRC through the inhibition of tubulin expression, inducing apoptosis, and causing G2/M phase cell cycle arrest pathway, which suggested that 5B could be a potential tubulin inhibitor. Based on that, a novel peptide-drug conjugate (PDC), which employed the CRC cells related receptor CD44 ligand peptide A6 coupling to 5B to accomplish A6-5B. The in vitro and in vivo studies showed that A6-5B could significantly inhibit the tumor growth and metastasis in CRC cells. Mechanistic studies revealed that both 5B and A6-5B exert their antitumor effects by inhibiting tubulin, demonstrating that 5B might play a payload role and A6 could act as a targeting moiety for selective drug delivery to tumor cells., Competing Interests: Declaration of competing interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work. There is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled., (Copyright © 2025 Elsevier Masson SAS. All rights reserved.)

Cyclin-dependent kinase 9 (CDK9) plays a pivotal role in promoting oncogenic transcriptional pathways, significantly contributing to the development and progression of cancer. Given the unique biostability of d-amino acid, the development of d-amino acid-containing peptides (DAACPs) is a promising strategy for cancer treatment. Currently, no DAACPs inhibitor targeting CDK9-cyclin T1 have been reported. Here, we reported the identification of a novel, highly potent, selective and stable DAACPs inhibitor (peptide-5) targeting CDK9-cyclin T1 interaction. Peptide-5 showed nanomolar inhibitory effect against CDK9-cyclin T1 (IC 50  = 4.16 ± 0.11 nM). Molecular dynamics (MD) simulation exhibited that peptide-5 stably bound to CDK9. Peptide-5 showed good inhibitory activity against multiple types of prostate cancer cells and demonstrated good biostability in mouse serum. Moreover, peptide-5 suppresses the tumor growth in DU145 cell-derived xenografts nude mice. These data suggest that peptide-5 is a potent antitumor candidate for further research., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025. Published by Elsevier Masson SAS.)

In this study, we have identified two novel peptides, 19Ac (comprising residues 91-105) and 20Ac (encompassing residues 96-110), from a systematically designed peptide library based on the Hepatitis B virus (HBV) core protein, that inhibit the assembly of HBV capsid. Peptide 20Ac exhibited about twofold the inhibitory potency of 19Ac and proved effective against both standard and morphothiadin (GLS4)-resistant HBV strains. Molecular dynamics simulations revealed that despite their overlapping sequence, 19Ac and 20Ac bonded to different regions of the core protein, thereby inhibiting capsid assembly through distinct mechanisms. These peptides could serve as valuable seed compounds for the further development of HBV capsid inhibitors, including GLS4-resistant strains., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The development of potent, specific, and pharmacologically viable chemical probes and therapeutics is a central focus of chemical biology and therapeutic development. However, a significant portion of predicted disease-causal proteins have proven resistant to targeting by traditional small molecule and biologic modalities. Many of these so-called "undruggable" targets feature extended, dynamic protein-protein and protein-nucleic acid interfaces that are central to their roles in normal and diseased signaling pathways. Here, we discuss the development of synthetically stabilized peptide and protein mimetics as an ever-expanding and powerful region of chemical space to tackle undruggable targets. These molecules aim to combine the synthetic tunability and pharmacologic properties typically associated with small molecules with the binding footprints, affinities and specificities of biologics. In this review, we discuss the historical and emerging platforms and approaches to design, screen, select and optimize synthetic "designer" peptidomimetics and synthetic biologics. We examine the inspiration and design of different classes of designer peptidomimetics: (i) macrocyclic peptides, (ii) side chain stabilized peptides, (iii) non-natural peptidomimetics, and (iv) synthetic proteomimetics, and notable examples of their application to challenging biomolecules. Finally, we summarize key learnings and remaining challenges for these molecules to become useful chemical probes and therapeutics for historically undruggable targets.