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Comprehensive Summary TAG‐assisted peptide synthesis technology enables optimal conservation of Fmoc amino acid raw materials and chemical solvents while eliminating the need for intricate chromatographic purification processes. This work presents a 4,4'‐diphenylphosphonoxy diphenylcarbinol tag‐mediated liquid‐phase synthesis approach for preparing side‐to‐tail cyclopeptides macolacin which has strong activity against gram‐negative bacteria, and its 15 analogues containing four N‐methylation modified cyclopeptides, as well as an investigation of their structure‐activity relationship (SAR). The synthesis of macolacin analogues primarily focuses on the modifications of the N‐methylation group of Ile‐7 and the tail fatty acyl chain of macolacin. The incorporation of N‐methylation for Ile‐7, along with the dihalogenated or monohalogenated benzoic acids for tail modification, exhibited remarkable antibacterial efficacy and minimal hepatocellular toxicity in vitro. The present study identified an N‐methylation‐modified antimicrobial cyclopeptide Ma14 that exhibits rapid bactericidal efficacy against A. baumanii, etc., while showing reduced hepatocellular toxicity. Molecular docking simulations were conducted to investigate the binding of cyclopeptides to the outer membrane protein BamA of A. baumannii. The findings demonstrated the stable binding interactions of the cyclopeptides with the BamA protein and then presented a novel approach to explain the bacteriostatic mechanism of macolacin‐based cyclopeptide antibiotics. [ABSTRACT FROM AUTHOR]

The salt ammonium 2‐aminomalonate (systematic name: ammonium 2‐azaniumylpropanedioate), NH4+·C3H4NO4−, was synthesized in diethyl ether from the starting materials malonic acid, ammonia and bromine. The salt was recrystallized from water as colourless blocks. In the solid state, intramolecular medium–strong N—H...O, weak C—H...O and weak C—H...N hydrogen bonds build a three‐dimensional network. [ABSTRACT FROM AUTHOR]

In recent years, a few asparaginyl endopeptidases (AEPs) from certain higher plants have been identified as efficient peptide ligases with wide applications in protein labeling and cyclic peptide synthesis. Recently, we developed a NanoLuc Binary Technology (NanoBiT)‐based peptide ligase activity assay to identify more AEP‐type peptide ligases. Herein, we screened 61 bamboo species from 16 genera using this assay and detected AEP‐type peptide ligase activity in the crude extract of all tested bamboo leaves. From a popular bamboo species, Bambusa multiplex, we identified a full‐length AEP‐type peptide ligase candidate (BmAEP1) via transcriptomic sequencing. After its zymogen was overexpressed in Escherichia coli and self‐activated in vitro, BmAEP1 displayed high peptide ligase activity, but with considerable hydrolytic activity. After site‐directed mutagenesis of its ligase activity determinants, the mutant zymogen of [G238V]BmAEP1 was normally overexpressed in E. coli, but failed to activate itself. To resolve this problem, we developed a novel protease‐assisted activation approach in which trypsin was used to cleave the mutant zymogen and was then conveniently removed via ion‐exchange chromatography. After the noncovalently bound cap domain was dissociated from the catalytic core domain under acidic conditions, the recombinant [G238V]BmAEP1 displayed high peptide ligase activity with much lower hydrolytic activity and could efficiently catalyze inter‐molecular protein ligation and intramolecular peptide cyclization. Thus, the engineered bamboo‐derived peptide ligase represents a novel tool for protein labeling and cyclic peptide synthesis. [ABSTRACT FROM AUTHOR]

Background: The therapeutic potential of relaxin for heart failure and renal disease in clinical trials is hampered by the short half‐life of serelaxin. Optimization of fatty acid‐acetylated single‐chain peptide analogues of relaxin culminated in the design and synthesis of R2R01, a potent and selective RXFP1 agonist with subcutaneous bioavailability and extended half‐life. Experimental Approach: Cellular assays and pharmacological models of RXFP1 activation were used to validate the potency and selectivity of R2R01. Increased renal blood flow was used as a translational marker of R2R01 activity. Human mastocytes (LAD2 cells) were used to study potential pseudo‐allergic reactions and CD4+ T‐cells to study immunogenicity. The pharmacokinetics of R2R01 were characterized in rats and minipigs. Key Results: In vitro, R2R01 had comparable potency and efficacy to relaxin as an agonist for human RXFP1. In vivo, subcutaneous administration of R2R01 increased heart rate and renal blood flow in normotensive and hypertensive rat and did not show evidence of tachyphylaxis. R2R01 also increased nipple length in rats, used as a chronic model of RXFP1 engagement. Pharmacokinetic studies showed that R2R01 has a significantly extended terminal half‐life. The in vitro assays with LAD2 cells and CD4+ T‐cells showed that R2R01 had low potential for pseudo‐allergic and immunogenic reactions, respectively. Conclusion and implications: R2R01 is a potent RXFP1 agonist with an extended half‐life that increases renal blood flow in various settings including normotensive and hypertensive conditions. The preclinical efficacy and safety data supported clinical development of R2R01 as a potential new therapy for renal and cardiovascular diseases. [ABSTRACT FROM AUTHOR]

We discuss the diverse functions of proteases in the context of their biotechnological and medical significance, as well as analytical approaches used to determine the functional activity of these enzymes. An insight into modern approaches to studying the kinetics and specificity of proteases, based on spectral (absorption, fluorescence), mass spectrometric, immunological, calorimetric, and electrochemical methods of analysis is given. We also examine in detail electrochemical systems for determining the activity and specificity of proteases. Particular attention is given to exploring innovative electrochemical systems based on the detection of the electrochemical oxidation signal of amino acid residues, thereby eliminating the need for extra redox labels in the process of peptide synthesis. In the review, we highlight the main prospects for the further development of electrochemical systems for the study of biotechnologically and medically significant proteases, which will enable the miniaturization of the analytical process for determining the catalytic activity of these enzymes. [Display omitted] • Proteases find wide applications in biotechnology and medicine. • Droplet microfluidics is applicable for directed evolution of proteases. • A lot of different physico-chemical methods are used for investigation of proteases. • Electrochemical methods are promising for protease activity determination. [ABSTRACT FROM AUTHOR]

ABSTRACT This review examines the potential applications of peptides in biotechnology, medicine, and pharmacy, while highlighting the important antibacterial and antiviral properties of peptides. Peptides and chemical peptide synthesis have become a field of study that is gaining great momentum today. Some of the main reasons for this are high specificity, biodegradability and versatility of peptides. Peptides also have some specific properties that make them attractive for pharmaceutical development. As a case study, it can be used to create peptides that can be used to replace or fix damaged proteins in the body by mimicking the action of naturally occurring proteins. Delivering drugs or other therapeutic agents to specific cells or tissues is another method that can help increase the effectiveness of treatment and reduce unwanted effects. Various types of antimicrobial peptides (AMPs), such as defensins and cathelicidins, and their anti‐infective properties are also discussed. Finally, peptides (melittin, lactoferricin, etc.) can be used to trigger an immune response against certain infections, such as COVID‐19 and Zika virus, by acting as vaccines. In our study, a comprehensive review was made on antiviral and AMPs, and especially peptides containing arginine and lysine were mentioned. The properties of these peptides, examples of these peptides and their developments in the pharmaceutical field are emphasized. [ABSTRACT FROM AUTHOR]

This article discusses the importance of peptides in various scientific disciplines and their growing demand in medicine. It explores new strategies, such as metal-mediated amidation, to improve the efficiency of peptide synthesis. The article focuses on the synthesis of mono-Boc-DKPs, a key building block for peptide synthesis, and the development of a regioselective protection method using trialkylaluminum. The authors conducted experiments to optimize the reaction conditions and found that the use of trialkylaluminum in combination with silicon reagents yielded the desired results. This method offers practical simplicity, scalability, and broad functional group tolerance, and it has the potential to facilitate the synthesis of regioselective mono-amide-NH-protected DKPs incorporating two amino acids with differing alkyl side chains. [Extracted from the article]

To fill the need for environmentally sensitive fluorescent unnatural amino acids able to operate in the red region of the spectrum, we have designed and synthesized Alared, a red solvatochromic and fluorogenic amino acid derived from the Nile Red chromophore. The new unnatural amino acid can be easily integrated into bioactive peptides using classical solid‐phase peptide synthesis. The fluorescence quantum yield and the emission maximum of Alared‐labeled peptides vary in a broad range depending on the peptide's environment, making Alared a powerful reporter of biomolecular interactions. Due to its red‐shifted absorption and emission spectra, Alared‐labeled peptides could be followed in living cells with minimal interference from cellular autofluorescence. Using ratiometric fluorescence microscopy, we were able to track the fate of the Alared‐labeled peptide agonists of the apelin G protein‐coupled receptor upon receptor activation and internalization. Due to its color‐shifting environmentally sensitive emission, Alared allowed for distinguishing the fractions of peptides that are specifically bound to the receptor or unspecifically bound to different cellular membranes. [ABSTRACT FROM AUTHOR]

The identification of novel drug targets in plant-parasitic nematodes (PPNs) is imperative due to the loss of traditional nematicides and a lack of replacements. Chemosensation, which is pivotal for PPNs in locating host roots, has become a focus in nematode behavioral research. However, its underlying molecular basis is still indistinct in such a diverse group of PPNs. To characterize genes participating in chemosensation in the Javanese root-knot nematode Meloidogyne javanica, RNA-sequencing of the second-stage juveniles (J2s) treated with tomato root exudate (TRE) for 1 h and 6 h was performed. Genes related to chemosensation in M. javanica mainly responded to TRE treatment at 1 h. Moreover, a gene ontology (GO) analysis underscored the significance of the neuropeptide G protein-coupled receptor signaling pathway. Consequently, the repertoire of putative neuropeptides in M. javanica, including FMRFamide-like peptides (FLPs), insulin-like peptides (ILPs), and neuropeptide-like peptides (NLPs), were outlined based on a homology analysis. The gene Mjflp-14a, harboring two neuropeptides, was significantly up-regulated at 1 h TRE treatment. Through peptide synthesis and J2 treatment, one of the two neuropeptides (MjFLP-14-2) was proven to influence the J2 chemotaxis towards tomato root tips. Overall, our study reinforces the potential of nematode neuropeptides as novel targets and tools for root-knot nematode control. [ABSTRACT FROM AUTHOR]

Hydrocarboxylation of methyl 2‐octynoate, a chemical commercially available at a low cost, with N‐protected amino acids was developed with a gold‐zinc cooperative catalyst constructed with a 5‐[(2,2′‐bipyridin)‐5‐yl]imidazo[1,5‐a]pyridin‐3‐ylidene to prepare α‐methoxycarbonyl enol esters as acylating reagents. The α‐methoxycarbonyl enol esters were isolable through silica‐gel column chromatography and storable without precautions regarding moisture. Acylation of free amines with the α‐methoxycarbonyl enol esters proceeded without epimerization of the stereogenic center derived from the enol esters, affording analytically pure dipeptide compounds through filtration and hexane‐washing. [ABSTRACT FROM AUTHOR]

Peptidols were prepared through the reductive cleavage of benzotriazole intermediates obtained from the on‐bead activation of 3,4‐diaminobenzoyl linkers. Remarkably, this method used commercially available amino acid residues and resins without further modification. Pure peptidols were collected with only filtration in 49%–87% yield. Only the derivatives with aspartic acid as the first C‐terminal residue required sophisticated chromatography purification. Esters and carboxylic acids were identified as side products and were suppressed by additional reduction or reduction in DMF. Remarkably, the reduction of peptides with the first aspartic acid residue at the C‐terminal afforded a C‐terminal lactone, which could be reduced by deprotection at 0 °C. For the synthesis of branched peptidols, the bulky wedge structures of the branched peptides resulted in low total yields, which were improved to 23%–28% by using peripheral Boc groups and SPPS on the Tental gel resin. In addition, this method gave two peptaibols, SPF‐5506‐A4 and Ac‐Gramicidin A, in 11% and 46% yields, respectively. [ABSTRACT FROM AUTHOR]

A relaxin‐like gonad‐stimulating peptide (RGP), Aso‐RGP, featuring six cysteine residues, was identified in the Crown‐of‐Thorns Starfish (COTS, Acanthaster cf. solaris) and initially produced through recombinant yeast expression. This method yielded a single‐chain peptide with an uncleaved C‐peptide (His Tag) and suboptimal purity. Our objective was to chemically synthesize Aso‐RGP in its mature form, comprising two chains (A and B) and three disulfide bridges, omitting the C‐peptide. Furthermore, we aimed to synthesize a newly identified relaxin‐like peptide, Aso‐RLP2, from COTS, which had not been previously synthesized. This paper reports the first total chemical synthesis of Aso‐RGP and Aso‐RLP2. Aso‐RGP synthesis proceeded without major issues, whereas the A‐chain of Aso‐RLP2, in its reduced and unfolded state with two free thiols, presented considerable challenges. These were initially marked by "messy" RP‐HPLC profiles, typically indicative of synthesis failure. Surprisingly, oxidizing the A‐chain significantly improved the RP‐HPLC profile, revealing the main issue was not synthesis failure but the peptide's aggregation tendency, which initially obscured analysis. This discovery highlights the critical need to account for aggregation in peptide synthesis and analysis. Ultimately, our efforts led to the successful synthesis of both peptides with purities exceeding 95 %. [ABSTRACT FROM AUTHOR]

We describe the design, synthesis, and activity of a potent thiourea-bridged backbone cyclic peptidomimetic known as Clarstatin, comprising a 5-amino acid sequence (Q/D)1-(R/K)2-X3-X4-A5-(Gln/Asp)1-(Arg/Lys)2-AA3-AA4-Ala5-based on a motif called "shared epitope (SE)", specifically present in specific alleles of the HLA-DRB1 gene. This SE binds to a particular site within the proline reach domain (P-domain) of the cell surface-calreticulin (CS-CRT). CS-CRT is a multifunctional endoplasmic reticulum (ER) calcium-binding protein that is located on the cell surface of T cells and triggers innate immune signaling, leading to the development of inflammatory autoimmune diseases. The development of Clarstatin was based on the parent peptide W-G-D1-K2-S3-G4-A5- derived from the active region of the SE. Following the design based on the cycloscan method, the synthesis of Clarstatin was performed by the Fmoc solid phase peptide synthesis (SPPS) method, purified by HPLC to 96% homogeneity, and its structure was confirmed by LC-MS. Clarstatin reduced calcium levels in Jurkat lymphocyte cultures, ameliorated uveitis in vivo in the experimental autoimmune uveitis (EAU) mice model, and was safe upon acute toxicity evaluation. These findings identify Clarstatin as a promising lead compound for future drug development as a novel class of therapeutic agents in the therapy of uveitis. [ABSTRACT FROM AUTHOR]

(1) Background: Antimicrobial resistance is growing at an extreme pace and has proven to be an urgent topic, for research into alternative treatments. Such a prospective possibility is hidden in antimicrobial peptides because of their low to no toxicity, effectiveness at low concentrations, and most importantly their ability to be used for multiple treatments. This work was focused on the study of the effect of the modification in position 7 of Temporin A on its biological activity; (2) Methods: The targeted peptides were synthesized using Fmoc/Ot-Bu SPPS. The antibacterial activity of the analogs was determined using the broth microdilution method and disk-diffusion method. In vitro tests were performed to determine the cytotoxicity, phototoxicity, and antiproliferative activity of the peptide analogs on a panel of tumor and normal cell lines; (3) Results: All analogs except DTCit showed good antibacterial activity, with DTDab having the best activity according to the disk-diffusion method. However, DTCit had an acceptable cytotoxicity, combined with good selectivity against the test MCF-7 cell line; (4) Conclusions: The obtained results revealed the importance of the basicity and length of the side chain at position 7 in the Temporin A sequence for both tested activities. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance threatens the effective prevention and treatment of an increasingly broad spectrum of infections caused by pathogenic microorganisms. This pressing challenge has intensified the search for alternative antibiotics with new pharmacological properties. Due to the chemical synergy between the biological activity of antimicrobial peptides (AMPs) and the different modes of action, catalytic properties, and redox chemistry of metal complexes, metallopeptides have emerged in recent years as an alternative to conventional antibiotics. In the present investigation, peptide ligands conjugated with 5-carboxy-1,10-phenanthroline (Phen) were prepared by solid-phase peptide synthesis (SPPS), and the corresponding copper(II) metallopeptides, Cu-PhenKG and Cu-PhenRG (where K = lysine, R = arginine, and G = glycine), were synthesized and characterized. The antimicrobial activities of these compounds toward Gram-positive and Gram-negative bacteria, evaluated by the broth microdilution technique, indicate that the metal center in the metallopeptides increases the antimicrobial activity of the complexes against the conjugated peptide ligands. Minimum inhibitory concentration (MIC) values of 0.5 μg/mL for S. aureus with the Cu-PhenKG complex and 0.63 μg/mL for S. typhimurium with the Cu-PhenRG complex were obtained. The MIC values found for the conjugated peptides in all microorganisms tested were greater than 1.5 μg/mL. The interactions of the conjugated peptides and their metallopeptides with plasmid DNA were evaluated by agarose gel electrophoresis. Alterations on the replication machinery were also studied by polymerase chain reaction (PCR). The results indicate that the complexes interact efficiently with pBR322 DNA from E. coli, delaying the band shift. Furthermore, the resulting DNA–metallopeptide complex is not a useful template DNA because it inhibits PCR, since no PCR product was detected. Finally, molecular dynamics and molecular docking simulations were performed to better understand the interactions of the obtained compounds with DNA. The Cu-PhenRG complex shows a significantly higher number of polar interactions with DNA, suggesting a higher binding affinity with the biopolymer. [ABSTRACT FROM AUTHOR]

Peptides displaying antimicrobial properties are being regarded as useful tools to evade and combat antimicrobial resistance, a major public health challenge. Here we have addressed dendrimers, attractive molecules in pharmaceutical innovation and development displaying broad biological activity. Triazine-based dendrimers were fully synthesized in the solid phase, and their antimicrobial activity and some insights into their mechanisms of action were explored. Triazine is present in a large number of compounds with highly diverse biological targets with broad biological activities and could be an excellent branching unit to accommodate peptides. Our results show that the novel peptide dendrimers synthesized have remarkable antimicrobial activity against Gram-negative bacteria (E. coli and P. aeruginosa) and suggest that they may be useful in neutralizing the effect of efflux machinery on resistance. [ABSTRACT FROM AUTHOR]

The present study aims at understanding the effect of organic solvents on the specific proteolytic activity and operational stability of asclepain cI in aqueous-organic media, using correlations between geometrical and structural parameters of asclepain cI. These correlations were determined by molecular dynamics (MD) simulations and the secondary structure of the enzyme validated by Fourier-transform Infrared (FTIR) spectroscopy. Asclepain cI exhibited significantly higher catalytic potential in 29 of the 42 aqueous-organic media tested, composed by 0.1 mM TRIS hydrochloride buffer pH 8 (TCB) and an organic solvent, than in buffer alone. Asclepain cI in water-organic miscible systems showed high FTIR spectral similarity with that obtained in TCB, while in immiscible systems the enzyme acquired different secondary structures than in buffer. Among the conditions studied, asclepain cI showed the highest catalytic potential in 50% v/v ethyl acetate in TCB. According to MD simulations, that medium elicited solvation and flexibility changes around the active center of asclepain cI and conducted to a new secondary structure with the active center preserved. These results provide valuable insights into the elucidation of the molecular mechanism of asclepain cI tolerance to organic solvents and pave the way for its future application for the synthesis of peptides in aqueous-organic media. [ABSTRACT FROM AUTHOR]

Peptide-like foldamers controlled by normal amide backbone hydrogen bonding have been extensively studied, and their folding patterns largely rely on configurational and conformational constraints induced by the steric properties of backbone substituents at appropriate positions. In contrast, opportunities to influence peptide secondary structure by functional groups forming individual hydrogen bond networks have not received much attention. Here, peptide-like foldamers consisting of alternating α,β,γ-triamino acids 3-amino-4-(aminomethyl)-2-methylpyrrolidine-3-carboxylate (AAMP) and natural amino acids glycine and alanine are reported, which were obtained by solution phase peptide synthesis. They form ordered secondary structures, which are dominated by a three-dimensional bridged triazaspiranoid-like hydrogen bond network involving the non-backbone amino groups, the backbone amide hydrogen bonds, and the relative configuration of the α,β,γ-triamino and α-amino acid building blocks. This additional stabilization leads to folding in both nonpolar organic as well as in aqueous environments. The three-dimensional arrangement of the individual foldamers is supported by X-ray crystallography, NMR spectroscopy, chiroptical methods, and molecular dynamics simulations. Peptide-like foldamers are known to be controlled by amide backbone hydrogen bonding, however, the influence of functional groups forming individual hydrogen-bond networks remains underexplored. Here, the authors report peptide-like α-γ heterofoldamers consisting of alternating α,β,γ-triamino acids, forming ordered secondary structures and folding in both organic and aqueous environments. [ABSTRACT FROM AUTHOR]

Organic molecules with light‐modifiable reactivity are important in many fields because they can serve as the “switch” for light to trigger chemical processes. Herein, we disclose a new type of stable non‐twisted amides, the reactivity of which can be turned on by light as acyl transfer reagents. Upon photo‐activation, these amides react with various nucleophiles including amines, phenols, hydroxide, thiols, boronic acids, and alkynes either under metal‐free or metal‐catalysis conditions. This reactivity hinges on the design and synthesis of a photo‐activatable reagent (7‐nitro‐5,6‐dihydrophenanthridine), which undergoes self‐aromatization enabled by an internal oxidant under light. This masked acyl donor group is anticipated to be useful in scenarios where light is preferred to trigger a chemical process. [ABSTRACT FROM AUTHOR]

Peripheral editing of complex molecules via C−H functionalization removes the pervasive retrosynthetic bias toward pre‐functionalization and taps into the innate, often subtle, stereoelectronic differences between C−H linkages. Using this approach, bioactive molecules and residues can be modified without being beholden to lengthy sequences, thus allowing biochemical hypotheses to be interrogated on accelerated timelines. Herein, the C−H functionalization paradigm is leveraged to tackle C7 C−H functionalization of the biologically important tryptophan core. The devised process, which was expanded to indolyl (and related) systems, utilizes an N‐bound unsymmetrical "designer" phosphine to direct C−H functionalization to the desired position while maintaining operational ease of directing group installation/removal. Quantum mechanically calculated steric properties and activation free energies suggest that this phosphine is hindered enough for favoring C−H functionalization over deactivation pathways but is still easily cleaved by nucleophiles. In addition, the process enables the direct C−H methylation, cyclopropanation, and arylation of tryptophan to yield unnatural amino acid (UAA) building blocks. As a testament to the versatility of this method, a solid phase peptide synthesis (SPPS)‐ready phosphinated tryptophan was incorporated into a pentapeptide and the C−H functionalization/dephosphination sequence was executed with ease. The utility of "on‐peptide" editing was exhibited through the late‐stage functionalization of several pentapeptides with a diverse set of C7 substituents on‐ and off‐resin. [ABSTRACT FROM AUTHOR]

ABSTRACT Liraglutide, developed by Novo Nordisk, is applied in Type 2 diabetes and obesity treatment. Several solid‐phase peptide synthesis protocols were designed for its production. However, current protocols are expensive and many of them are difficult to scale‐up. In this study, a novel alternative for liraglutide production was developed. The peptide was elongated by Fmoc/tBu solid‐phase peptide synthesis on 4‐hydroxymethylbenzoyl–ChemMatrix (HMBA‐CM) resin using the chaotropic agent LiCl as an additive to prevent peptide aggregation. After elongation, removal of side‐chain protecting groups and peptide cleavage from the resin was performed by a two‐stage procedure. Side‐chain protecting groups were removed with 92.5% TFA, leaving the unprotected peptide attached to the solid support. The resin was thoroughly washed to eliminate the contaminants. Next, peptide release was achieved by treating the peptidyl resin with NaOH 0.1 N. This two‐stage procedure assures a high‐purity product without the need of using a large amount of ether as in previous protocols. Finally, liraglutide was purified by hydrophobic interaction with low‐pressure liquid chromatography (HI‐LPLC) instead of using the expensive RP‐HPLC applied in reported methods. This simple and economic method resulted in a high yield and a purity product while overcoming the high cost and difficulties of current processes. [ABSTRACT FROM AUTHOR]

The problem of antimicrobial resistance is becoming a daunting challenge for human society and healthcare systems around the world. Hence, there is a constant need to develop new antibiotics to fight resistant bacteria, among other important social and economic measures. In this regard, murepavadin is a cyclic antibacterial peptide in development. The synthesis of murepavadin was undertaken in order to optimize the preparative protocol and scale-up, in particular, the use of new activation reagents. In our hands, classical approaches using carbodiimide/hydroxybenzotriazole rendered low yields. The use of novel carbodiimide and reagents based on OxymaPure® and Oxy-B is discussed together with the proper use of chromatographic conditions for the adequate characterization of peptide crudes. Higher yields and purities were obtained. Finally, the antimicrobial activity of different synthetic batches was tested in three Pseudomonas aeruginosa strains, including highly resistant ones. All murepavadin batches yielded the same highly active MIC values and proved that the chiral integrity of the molecule was preserved throughout the whole synthetic procedure. [ABSTRACT FROM AUTHOR]

To develop peptide drugs targeting integrin receptors, synthetic peptide ligands endowed with well-defined selective binding motifs are necessary. The snake venom KTS-containing disintegrins, which selectively block collagen α1β1 integrin, were used as lead compounds for the synthesis and structure–activity relationship of a series of linear peptides containing the KTS-pharmacophore and alternating natural amino acids and 3-aminobenzoic acid (MABA). To ensure a better stiffness and metabolic stability, one, two and three MABA residues, were introduced around the KTS pharmacophore motif. Molecular dynamics simulations determined that the solution conformation of MABA peptide 4 is more compact, underwent larger conformational changes until convergence, and spent most of the time in a single cluster. The peptides' binding affinity has been characterized by an enzyme linked immunosorbent assay in which the most potent peptide 4 inhibited with IC50 of 324 ± 8 µM and 550 ± 45 µM the binding of GST-α1-A domain to collagen IV fragment CB3, and the cell adhesion to collagen IV using α1-overexpressor cells, respectively. Docking studies and MM-GBSA calculations confirmed that peptide 4 binds a smaller region of the integrin near the collagen-binding site and penetrated deeper into the binding site near Trp1. Peptide 4 inhibited tube formation by endothelial cell migration in the Matrigel angiogenesis in vitro assay. Peptide 4 was acutely tolerated by mice, showed stability in human serum, decreased tumor volume and angiogenesis, and significantly increased the survival of mice injected with B16 melanoma cells. These findings propose that MABA-peptide 4 can further serve as an α1β1-integrin antagonist lead compound for further drug optimization in angiogenesis and cancer therapy. [ABSTRACT FROM AUTHOR]

Solid‐phase peptide synthesis (SPPS) is widely used to produce peptides. Since its invention, the solid support has enabled the elongation of the synthetic peptide chain. As technologies have evolved, the length of peptide chains accessible with SPPS has grown to that of single‐domain proteins. Resins for SPPS have advanced to improve synthesis capabilities as well. The functionalization of solid supports with polyethylene glycol (PEG) is commonly employed in a range of commercially available resins to aid in the ability to synthesize long or difficult sequences. A notable example of a widely used PEG‐based solid support is ChemMatrix® resin; however, this and several similar resins have recently been discontinued. Here, we demonstrate and compare the capabilities of OctaGel™, ProTide®, and TentaGel XV® resins in synthesizing sequences ranging from peptides to single domain proteins using automated fast‐flow peptide synthesis. Our studies indicate that each resin performs well for routine peptide synthesis by automated flow, whereas TentaGel XV resin showed the best performance for synthesis of difficult or long peptide sequences when comparing quality using yield, purity, and real‐time UV absorbance monitoring during synthesis. [ABSTRACT FROM AUTHOR]

The evolution of the translation system is a fundamental issue in the quest for the origin of life. A feasible evolutionary scenario necessitates the autonomous emergence of a protoribosome capable of catalyzing the synthesis of the initial peptides. The peptidyl transferase center (PTC) region in the modern ribosomal large subunit is believed to retain a vestige of such a prebiotic non-coded protoribosome, which would have self-assembled from random RNA chains, catalyzed peptide bond formation between arbitrary amino acids, and produced short peptides. Recently, three research groups experimentally demonstrated that several distinct dimeric constructs of protoribosome analogues, derived predicated on the approximate 2-fold rotational symmetry inherent in the PTC region, possess the ability to spontaneously fold, dimerize, and catalyze the formation of peptide bonds and of short peptides. These dimers are examined, aiming at retrieving information concerned with the characteristics of a prebiotic protoribosome. The analysis suggests preconditions for the laboratory re-creation of credible protoribosome analogues, including the preference of a heterodimer protoribosome, contradicting the common belief in the precedence of homodimers. Additionally, it derives a dynamic process which possibly played a role in the spontaneous production of the first bio-catalyzed peptides in the prebiotic world. [ABSTRACT FROM AUTHOR]

The polymerization of unactivated amino acids (AAs) is an important topic because of its applications in various fields including industrial medicinal chemistry and prebiotic chemistry. Silica as a promoter for this reaction, is of great interest owing to its large abundance and low cost. The amide/peptide bond synthesis on silica has been largely demonstrated but suffers from a lack of knowledge regarding its reaction mechanism, the key parameters, and surface features that influence AA adsorption and reactivity, the selectivity of the reaction product, the role of water in the reaction, etc. The present review addresses these problems by summarizing experimental and modeling results from the literature and attempts to rationalize some apparent divergences in published results. After briefly presenting the main types of silica surface sites and other relevant macroscopic features, we discuss the different deposition procedures of AAs, whose importance is often neglected. We address the possible AA adsorption mechanisms including covalent grafting and H‐bonding and show that they are highly dependent on silanol types and density. We then consider how the adsorption mechanisms determine the occurrence and outcome of AA condensation (formation of cyclic dimers or of long linear chains), and outline some recent results that suggest significant polymerization selectivity in systems containing several AAs, as well as the formation of specific elements of secondary structure in the growing polypeptide chains. [ABSTRACT FROM AUTHOR]

Human leukocyte antigen (HLA) recognizes foreign threats and triggers immune responses by presenting peptides to T cells. Computationally modeling the binding patterns between peptide and HLA is very important for the development of tumor vaccines. However, it is still a big challenge to accurately predict HLA molecules binding peptides. In this paper, we develop a new model TripHLApan for predicting HLA molecules binding peptides by integrating triple coding matrix, BiGRU + Attention models, and transfer learning strategy. We have found the main interaction site regions between HLA molecules and peptides, as well as the correlation between HLA encoding and binding motifs. Based on the discovery, we make the preprocessing and coding closer to the natural biological process. Besides, due to the input being based on multiple types of features and the attention module focused on the BiGRU hidden layer, TripHLApan has learned more sequence level binding information. The application of transfer learning strategies ensures the accuracy of prediction results under special lengths (peptides in length 8) and model scalability with the data explosion. Compared with the current optimal models, TripHLApan exhibits strong predictive performance in various prediction environments with different positive and negative sample ratios. In addition, we validate the superiority and scalability of TripHLApan's predictive performance using additional latest data sets, ablation experiments and binding reconstitution ability in the samples of a melanoma patient. The results show that TripHLApan is a powerful tool for predicting the binding of HLA-I and HLA-II molecular peptides for the synthesis of tumor vaccines. TripHLApan is publicly available at https://github.com/CSUBioGroup/TripHLApan.git. [ABSTRACT FROM AUTHOR]

This article discusses the synthesis of amides and peptides using a new acid activator called [4-(acetylamino)phenyl]imidodisulfuryl difluoride (AISF). The authors optimized the reaction conditions and found that the method was suitable for various carboxylic acids, amines, and amino acids. The protocol was demonstrated to be racemization-free and suitable for gram-scale reactions. The article also provides detailed information about the chemical properties and characterization of various compounds, including their yields, physical properties, and spectroscopic data. The supporting information for the article is available online. [Extracted from the article]

Suppressor tRNAs, notable for their capability of reading through the stop codon while maintaining normal peptide synthesis, are promising in treating diseases caused by premature termination codons (PTC). However, the lack of effective engineering methods for suppressor tRNAs has curtailed their application potential. Here, we introduce a directed evolution technology that employs phage-assisted continuous evolution (PACE), combined with gradient biosensors featuring various PTCs in the M13 gene III. Utilizing this novel methodology, we have successfully evolved tRNATrp (UGG) reading through the UGA stop codon in Escherichia coli. Massively parallel sequencing revealed that these mutations predominantly occurred in the anticodon loop. Finally, two suppressor tRNATrp (UGA) mutants exhibited over fivefold increases in readthrough efficiency. [Display omitted] • A directed evolution technology for suppressor tRNAs was developed in E. coli. • Suppressor tRNA mutations mainly occurred in the anticodon loop. • Two suppressor tRNATrp (UGA) exhibited over fivefold increase in efficiency. [ABSTRACT FROM AUTHOR]

Aspartic proteases play a vital role in diverse biological processes, with microbial variants garnering considerable attention for their commercial potential across various industries. This comprehensive review delves into the intricate aspects of microbial aspartic proteases, encompassing their biosynthesis, genetic regulation, secretion mechanisms, post - translational modifications, characteristics, and emerging applications. The biosynthesis of these proteases involves the translation of corresponding genes into precursor proteins, which undergo a series of processing steps culminating in the formation of mature enzymes. The efficiency of aspartic protease production and commercialization relies heavily on understanding the mechanisms governing their secretion. Notably, post -translational modifications, such as glycosylation and phosphorylation, play a significant role in influencing the activity and stability of these enzymes. The review further explores the substrate specificity and catalytic properties of microbial aspartic proteases, along with their potential applications in the food industry, pharmaceuticals, and biotechnology sectors. In the food industry, these proteases find utility in enhancing flavor, texture, and nutritional value. In the pharmaceutical realm, they contribute to drug discovery and development. Additionally, in biotechnology, microbial aspartic proteases exhibit versatility in applications such as protein engineering, peptide synthesis, and bioremediation. This comprehensive examination provides valuable insights into the multifaceted nature of these enzymes, shedding light on their biosynthesis, genetic regulation, secretion mechanisms, post -translational modifications, characteristics, and promising commercial applications. [ABSTRACT FROM AUTHOR]

Ubiquitin (Ub) is a small, highly conserved protein essential for eukaryotic biology, and is unique in its formation of polyubiquitin chains by conjugation to one of its seven lysine side chains. Here we report that atomic tailoring of Ub side chains – i. e. the insertion, deletion, or replacement of specific atoms – has significant and unexpected consequences on the enzymatic conjugation of Ub oligomers by isopeptide bond formation mediated by E2 conjugating enzymes. These studies employed chemical synthesis and ligation methods to prepare numerous specifically tailored Ub monomers on multi‐milligram scales. While some modifications including N‐terminal acylation and methionine replacement did not affect protein folding or Ub chain formation with Ube2 K, other modifications had a pronounced effect of oligomerization with Ubc13/Mms2. We observed that Ala46Hse mutation obliterates the ability of this Ub monomer to accept another Ub at Lys63 in Ubc13‐mediated conjugations. Exhaustive replacement of all seven lysines with shorter surrogates Orn, Dab, or Dap essentially blocks Ub chain formation, and in the case of Dap, precludes proper folding of the Ub protein. [ABSTRACT FROM AUTHOR]

The formation of protein precursors, due to the condensation of atomic carbon under the low-temperature conditions of the molecular phases of the interstellar medium, opens alternative pathways for the origin of life. We perform peptide synthesis under conditions prevailing in space and provide a comprehensive analytic characterization of its products. The application of 13C allowed us to confirm the suggested pathway of peptide formation that proceeds due to the polymerization of aminoketene molecules that are formed in the C + CO + NH3 reaction. Here, we address the question of how the efficiency of peptide production is modified by the presence of water molecules. We demonstrate that although water slightly reduces the efficiency of polymerization of aminoketene, it does not prevent the formation of peptides. [ABSTRACT FROM AUTHOR]

Alpha-ketoglutaric acid (α-KG), as an intermediate product of the tricarboxylic acid cycle, plays a crucial role in peptide and amino acid synthesis. In order to reduce costs and improve efficiency in the oxidative production of α-ketoglutaric acid, this study successfully synthesized and expressed L-glutamate oxidase (LGOXStr) from Streptomyces viridosporus R111 and catalase (KatGEsc) from Escherichia coli H736. Two immobilization methods and the conditions for one-step whole-cell catalysis of α-ketoglutaric acid were investigated. α-Ketoglutaric acid has broad applications in the pharmaceutical, food, and chemical industries. The specific research results are as follows: (1) By fusing the sfGFP tag, L-glutamate oxidase (LGOXStr r) and catalase (KatGEsc) were successfully anchored to the outer membrane of Escherichia coli cells, achieving one-step whole-cell catalysis of α-ketoglutaric acid with a conversion efficiency of up to 75%. (2) Through the co-immobilization of LGOXStr and KatGEsc, optimization of the preparation parameters of immobilized cells, and exploration of the immobilization method using E.coli@ZIF-8, immobilized cells with conversion rates of over 60% were obtained even after 10 cycles of reuse. Under the optimal conditions, the production rate of α-ketoglutaric acid reached 96.7% in a 12 h reaction, which is 1.1 times that of E. coli@SA and 1.29 times that of free cells. [ABSTRACT FROM AUTHOR]

Pseudoproline derivatives such as Thr(ΨPro)-OH are commonly used in peptide synthesis to reduce the likelihood of peptide aggregation and to prevent aspartimide (Asi) formation during the synthesis process. In this study, we investigate notable by-products such as aspartimide formation and an imine derivative of the Thr(ΨPro) moiety observed in flow peptide chemistry synthesis. To gain insight into the formation of these unexpected by-products, we design a series of experiments. Furthermore, we demonstrate the oxazolidine character of the pseudoproline moiety and provide plausible mechanisms for the two-way ring opening of oxazolidine leading to these by-products. In addition, we present evidence that Asi formation appears to be catalyzed by the presence of the pseudoproline moiety. These observed side reactions are attributed to elevated temperature and pressure; therefore, caution is advised when using ΨPro derivatives under such harsh conditions. In addition, we propose a solution whereby thermodynamically controlled Asi formation can be kinetically prevented. [ABSTRACT FROM AUTHOR]

Cyclen‐peptide bioconjugates are usually prepared in multiple steps that require individual preparation and purification of the cyclic peptide and hydrophilic cyclen derivatives. An efficient strategy is discovered for peptide cyclization and functionalization toward lanthanide probe via three components intermolecular crosslinking on solid‐phase peptide synthesis with high conversion yield. Multifunctionality can be conferred by introducing different modular parts or/and metal ions on the cyclen‐embedded cyclopeptide. As a proof‐of‐concept, a luminescent Eu3+ complex and a Gd3+‐based contrasting agent for in vitro optical imaging and in vivo magnetic resonance imaging, respectively, are demonstrated through utilizing this preparation of cyclen‐embedded cyclic arginylglycylaspartic acid (RGD) peptide. [ABSTRACT FROM AUTHOR]

This article discusses the synthesis of 2-aminopyridine-modified peptide nucleic acids (PNAs) and their potential applications in research and diagnostics. PNAs are known for their high affinity and sequence specificity in binding to nucleic acids. The article describes the chemical modifications made to improve the properties of PNAs, such as replacing cytosine with pseudoisocytosine and using 2-aminopyridine as an alternative. The authors also outline the optimized synthetic route to produce the modified PNA monomers. The article provides detailed procedures and recommendations for the synthesis of PNAs using different synthesizers. Overall, the article offers valuable insights for researchers interested in the synthesis and applications of modified PNAs. [Extracted from the article]

Mirror‐image proteins (D‐proteins) are useful in biomedical research for purposes such as mirror‐image screening for D‐peptide drug discovery, but the chemical synthesis of many D‐proteins is often low yielding due to the poor solubility or aggregation of their constituent peptide segments. Here, we report a Lys‐C protease‐cleavable solubilizing tag and its use to synthesize difficult‐to‐obtain D‐proteins. Our tag is easily installed onto multiple amino acids such as DLys, DSer, DThr, and/or the N‐terminal amino acid of hydrophobic D‐peptides, is impervious to various reaction conditions, such as peptide synthesis, ligation, desulfurization, and transition metal‐mediated deprotection, and yet can be completely removed by Lys‐C protease under denaturing conditions to give the desired D‐protein. The efficacy and practicality of the new method were exemplified in the synthesis of two challenging D‐proteins: D‐enantiomers of programmed cell death protein 1 IgV domain and SARS‐CoV‐2 envelope protein, in high yield. This work demonstrates that the enzymatic cleavage of solubilizing tags under denaturing conditions is feasible, thus paving the way for the production of more D‐proteins. [ABSTRACT FROM AUTHOR]

Nanosized alginate-based particles (NAPs) were obtained in a one-pot solvent-free synthesis procedure, achieving the design of a biocompatible nanocarrier for the encapsulation of IbM6 antimicrobial peptide (IbM6). IbM6 is integrated in the nascent nanosized hydrogel self-assembly guided by electrostatic interactions and by weak interactions, typical of soft matter. The formation of the nanogel is a dynamic and complex process, which presents an interesting temporal evolution. In this work, we optimized the synthesis conditions of IbM6-NAPs based on small-angle X-ray scattering (SAXS) measurements and evaluated its time evolution over several weeks by sensing the IbM6 environment in IbM6-NAPs from photochemical experiments. Fluorescence deactivation experiments revealed that the accessibility of different quenchers to the IbM6 peptide embedded in NAPs is dependent on the aging time of the alginate network. Lifetimes measurements indicate that the deactivation paths of the excited state of the IbM6 in the nanoaggregates are reduced when compared with those exhibited by the peptide in aqueous solution, and are also dependent on the aging time of the nanosized alginate network. Finally, the entrapment of IbM6 in NAPs hinders the degradation of the peptide by trypsin, increasing its antimicrobial activity against Escherichia coli K-12 in simulated operation conditions. [ABSTRACT FROM AUTHOR]

Solid-phase peptide synthesis (SPPS) is the preferred strategy for synthesizing most peptides for research purposes and on a multi-kilogram scale. One key to the success of SPPS is the continual evolution and improvement of the original method proposed by Merrifield. Over the years, this approach has been enhanced with the introduction of new solid supports, protecting groups for amino acids, coupling reagents, and other tools. One of these improvements is the use of the so-called "safety-catch" linkers/resins. The linker is understood as the moiety that links the peptide to the solid support and protects the C-terminal carboxylic group. The "safety-catch" concept relies on linkers that are totally stable under the conditions needed for both α-amino and side-chain deprotection that, at the end of synthesis, can be made labile to one of those conditions by a simple chemical reaction (e.g., an alkylation). This unique characteristic enables the simultaneous use of two primary protecting strategies: tert-butoxycarbonyl (Boc) and fluorenylmethoxycarbonyl (Fmoc). Ultimately, at the end of synthesis, either acids (which are incompatible with Boc) or bases (which are incompatible with Fmoc) can be employed to cleave the peptide from the resin. This review focuses on the most significant "safety-catch" linkers. [ABSTRACT FROM AUTHOR]

Objectives: The objective of the present study was to investigate the effect of Rhubarb anthraquinone (RA) on a high-fat diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD) rat model, and explore potential biomarker and metabolic pathways by using the metabolomics method. Materials and methods: We established HFD rats as the NAFLD model. Forty Sprague–Dawley rats were randomly divided into a control group, model group, RA low-dose group, RA medium-dose group, and RA high-dose group, and evaluated the protective effect of RA on NAFLD by detecting biochemical indicators of serum and pathological changes of liver tissue. Investigating potential biomarkers and metabolic pathways connected with RA's protective effects against NAFLD by UHPLC–Q-TOF-MS untargeted metabolomics. Results: The results showed that RA significantly reversed the increase of TG, TC, ALT, AST, and ALP (P <.05), the decrease of HDL-C (P <.05), and alleviated pathological conditions in NAFLD rats. Based on potential biomarker analysis, RA affected metabolic pathways such as fatty acids biosynthesis, bile acids biosynthesis, and pentose phosphate pathway, delaying the progression of NAFLD. Conclusion: RA improved blood lipid levels, liver function, and pathological conditions of NAFLD rats. Meanwhile, affected the metabolic pathways and regulated the synthesis of fatty acids and bile acids in NAFLD rats. Rhubarb anthraquinone affects the metabolic pathways of fatty acids biosynthesis, bile acids biosynthesis, and pentose phase pathway, thereby regulating the function of synthesis of fatty acids and bile acids in NAFLD rats. Rhubarb anthraquinone has the potential to prevent and treat NAFLD. [ABSTRACT FROM AUTHOR]

Peptide biomolecules have important bioactivities and hence their use in drug design and development studies has increased in recent years. Conotoxins are natural peptides that obtained from cone snail venoms and have the potential to be used for chronic pain treatment, Parkinson's disease, schizophrenia, obesity and cancer due to their effects on the nervous system. However, their use as medicines has been limited as they can be easily broken down by many proteolytic enzymes in the body. Several modification methods are used to overcome these disadvantages. Cyclization of the peptide backbone is one such method and has been used to stabilize various linear peptides. In this study, the N- and C-termini of a-conotoxin TxID with two disulfide bridges were joined using a six amino acid long GGAAGG linker peptide chain to cyclize the peptide backbone and the serum stability of the cyclized peptide was examined. The cyclic TxID peptide remained intact about 50% in human serum after 24 hours. [ABSTRACT FROM AUTHOR]

Heavy and irresponsible use of antibiotics in the last century has put selection pressure on the microbes to evolve even faster and develop more resilient strains. In the confrontation with such sometimes called "superbugs", the search for new sources of biochemical antibiotics seems to have reached the limit. In the last two decades, bioactive antimicrobial peptides (AMPs), which are polypeptide chains with less than 100 amino acids, have attracted the attention of many in the control of microbial pathogens, more than the other types of antibiotics. AMPs are groups of components involved in the immune response of many living organisms, and have come to light as new frontiers in fighting with microbes. AMPs are generally produced in minute amounts within organisms; therefore, to address the market, they have to be either produced on a large scale through recombinant DNA technology or to be synthesized via chemical methods. Here, heterologous expression of AMPs within bacterial, fungal, yeast, plants, and insect cells, and points that need to be considered towards their industrialization will be reviewed. Sources of peptide production and their applications. Some AMPs directly extracted from natural sources, some of them are chemically synthesized either using liquid or solid phase peptides synthesis, and for large scale production, recombinant expression using heterologous expression systems have been used. [ABSTRACT FROM AUTHOR]

The RFamide family of peptides represents an important class of GPCR ligand neuropeptides covering a wide range of biological functions. While many analogues of the highly conserved C‐terminal RFamide motif within this peptide class have been synthesized and their functional significance elucidated, additional exploration of the structure activity relationship is of value. We have developed a novel linker for solid phase peptide synthesis (SPPS) which is able to anchor amine functionalised compounds for further elaboration. The acid labile benzofuranone based amine (ALBA) linker (5‐(3‐aminopropylcarbamoyl)‐2‐[[tert‐butyl(diphenyl)silyl]oxymethyl]benzoic acid) is compatible with Fmoc based SPPS and has two cleavage modes. As a proof of concept, the ALBA linker was used to successfully synthesise a novel analogue of Kisspeptin 10, the natural ligand for GPCR54, whereby the natural RFamide motif was replaced with an RFamine. Biological evaluation of the amine‐containing analogue revealed that the group is not compatible with receptor activation. [ABSTRACT FROM AUTHOR]

Bicyclic peptides exhibit improved metabolic stabilities and target specificities when compared to their linear or mono-cyclic counterparts; however, efficient and straightforward synthesis remains challenging due to their intricate architectures. Here, we present a highly selective and operationally simple one-pot chemoenzymatic tandem cyclization approach to synthesize bicyclic peptides with small to medium ring sizes. Penicillin-binding protein-type thioesterases (PBP-type TEs) efficiently cyclized azide/alkyne-containing peptides in a head-to-tail manner. Successive copper (I)-catalyzed azide-alkyne cycloaddition generated bicyclic peptides in one-pot, thus omitting the purification of monocyclic intermediates. This chemoenzymatic strategy enabled the facile synthesis of bicyclic peptides bearing hexa-, octa-, and undecapeptidyl head-to-tail cyclic scaffolds. Bicyclic peptides exhibit improved metabolic stabilities, membrane permeabilities, and target specificities over their linear and mono-cyclic counterparts, however, efficient bicyclization remains challenging. Here, the authors develop a one-pot tandem chemoenzymatic bicyclization by combination of penicillin-binding protein-type thioesterase-mediated head-to-tail macrolactamization and copper(I)-catalyzed azide–alkyne cycloaddition. [ABSTRACT FROM AUTHOR]

The synthetic difficulty of target‐specific lanthanide complexes, despite their unique characteristics, limits their use in in vitro/ in vivo studies and biomedical applications. With commercially available and affordable reagents, a facile synthetic approach is developed to modularly deploy nitrobenzoxadiazole and neodymium complexes onto bioactive peptides. The yielded probes show observable neodymium emission with specific localization to corresponding biotargets in vitro, which became the first example of a stable, water‐soluble, and target‐specific neodymium(III) complex applicable for in vitro imaging with detectable brightness. [ABSTRACT FROM AUTHOR]

The international peptide community rejoiced when one of its most distinguished members, Morten Meldal of Denmark, shared the 2022 Nobel Prize in Chemistry. In fact, the regiospecific solid-phase "copper(I)-catalyzed 1,3-dipolar cycloaddition of terminal alkynes to azides" (CuACC) reaction—that formed the specific basis for Meldal's recognition—was reported first at the 17th American Peptide Symposium held in San Diego in June 2001. The present perspective outlines intertwining conceptual and experimental threads pursued concurrently in Copenhagen and Minneapolis, sometimes by the same individuals, that provided context for Meldal's breakthrough discovery. Major topics covered include orthogonality in chemistry; the dithiasuccinoyl (Dts) protecting group for amino groups in α-amino acids, carbohydrates, and monomers for peptide nucleic acids (PNA); and poly(ethylene glycol) (PEG)-based solid supports such as PEG–PS, PEGA, and CLEAR [and variations inspired by them] for solid-phase peptide synthesis (SPPS), solid-phase organic synthesis (SPOS), and combinatorial chemistry that can support biological assays in aqueous media. [ABSTRACT FROM AUTHOR]

Flaxseed (Linum usitatissimum L.) has been associated with numerous health benefits. The flax plant synthesizes an array of biologically active compounds including peptides or linusorbs (LOs, a.k.a., cyclolinopeptides), lignans, soluble dietary fiber and omega-3 fatty acids. The LOs arise from post-translational modification of four or more ribosome-derived precursors. These compounds exhibit an array of biological activities, including suppression of T-cell proliferation, excessive inflammation, and osteoclast replication as well as induction of apoptosis in some cancer cell lines. The mechanisms of LO action are only now being elucidated but these compounds might interact with other active compounds in flaxseed and contribute to biological activity attributed to other flax compounds. This review focuses on both the biological interaction of LOs with proteins and other molecules and comprehensive knowledge of LO pharmacological and biological properties. The physicochemical and nutraceutical properties of LOs, as well as the biological effects of certain LOs, and their underlying mechanisms of action, are reviewed. Finally, strategies for producing LOs by either peptide synthesis or recombinant organisms are presented. This review will be the first to describe LOs as a versatile scaffold for the action of compounds to deliver physiochemically/biologically active molecules for developing novel nutraceuticals and pharmaceuticals. [ABSTRACT FROM AUTHOR]

Drawing inspiration from the initiating amino acid modification in biosynthetic peptides, we have successfully demonstrated a biomimetic mechanism for N-to-C terminal extension in prebiotic peptide synthesis. This achievement was accomplished by using acetylated amino acid amides as the N-terminal substrate for peptide synthesis and amino acid amides as the C-terminal extension, with the reaction carried out in a dry-wet cycle at 80 °C without requiring any activators. This provides a plausible pathway for the formation of prebiotic peptides. [ABSTRACT FROM AUTHOR]

Using a minimallised approach,we designed and synthesized N‐terminal modified peptides W‐KRGNKWLA‐CONH2 (P1) and W‐ARGDGGNGRGA‐CONH2 (P2) using Fmoc‐Chemistry solid phase peptide synthesis protocol. High‐performance liquid chromatograms and mass spectrometry (LCMS and analytical HPLC) were employed to determine the purity and molecular weight of the peptide. Surface tension measurements are used to evaluate peptide surface activity. The primary structure of the peptideis anlaysed by NMR spectroscopy. Circular dichroism studies demonstrate that the secondary structure of the peptide changes minimally when it attached to anionic lipid bilayers (POPC : POPG). According to a steady‐state fluorescence experiment, peptides P1 and P2 preferentially interact with anionic (POPC : POPG) lipid bilayers rather than zwitterionic (POPC) lipid bilayers. The peptide P2 interacts preferentially with anionic lipid membranes and has an anticancer effect due to RGD and NGR binding motifs. The cytotoxicity of the MTT experiment demonstrated that both normal and cancerous cells could lower peptide concentrations below their IC50 levels. Molecular docking also supports in‐vitro anticancer research. Both peptides P1 and P2 were non‐toxic to vero cells and appeared to be more promising as it demonstrated wide spectrum anticancer activity. [ABSTRACT FROM AUTHOR]

Simple Summary: A protein known as the γδ T-cell receptor is the distinguishing hallmark of a small white blood cell subset known as γδ T-cells. γδ T-cells survey the body for potentially dangerous cells, including cancer. The most common γδ T-cell receptor found in the bloodstream is called Vγ9Vδ2 and this detects attributes of cancer cells called phosphoantigens. To generate large numbers of cells that detect phosphoantigens, the Vγ9Vδ2 T-cell receptor gene can be introduced into a more plentiful white blood cell subset called αβ T-cells. In this study, we have inserted a small additional peptide fragment into the Vγ9Vδ2 T-cell receptor, enabling it to also recognise a second tumour target called αvβ6 integrin. When this modified receptor was expressed in αβ T-cells, they acquired the ability to kill tumour cells that produce either phosphoantigens or αvβ6 integrin. By this means, we have broadened the tumour recognition capacity of these engineered T-cells. γδ T-cells provide immune surveillance against cancer, straddling both innate and adaptive immunity. G115 is a clonal γδ T-cell receptor (TCR) of the Vγ9Vδ2 subtype which can confer responsiveness to phosphoantigens (PAgs) when genetically introduced into conventional αβ T-cells. Cancer immunotherapy using γδ TCR-engineered T-cells is currently under clinical evaluation. In this study, we sought to broaden the cancer specificity of the G115 γδ TCR by insertion of a tumour-binding peptide into the complementarity-determining region (CDR) three regions of the TCR δ2 chain. Peptides were selected from the foot and mouth disease virus A20 peptide which binds with high affinity and selectivity to αvβ6, an epithelial-selective integrin that is expressed by a range of solid tumours. Insertion of an A20-derived 12mer peptide achieved the best results, enabling the resulting G115 + A12 T-cells to kill both PAg and αvβ6-expressing tumour cells. Cytolytic activity of G115 + A12 T-cells against PAg-presenting K562 target cells was enhanced compared to G115 control cells, in keeping with the critical role of CDR3 δ2 length for optimal PAg recognition. Activation was accompanied by interferon (IFN)-γ release in the presence of either target antigen, providing a novel dual-specificity approach for cancer immunotherapy. [ABSTRACT FROM AUTHOR]