Peptide Conjugates Research Articles

Photochemical and Collision-Induced Cross-Linking in Stereochemically Distinct Scaffolds of Peptides and Nitrile Imines in Gas-Phase Ions.

Intramolecular cross-linking between peptides and nitrile-imine intermediates was studied in stereochemically distinct conjugates in which the reacting components were mounted on cis-1,2-cyclohexane and trans-1,4-cyclohexane scaffolds that we call 1,2-s-peptides and 1,4-s-peptides, respectively. The nitrile-imine intermediates were generated by N2 loss from 2,5-diaryltetrazole tags upon UV-photodissociation at 213 and 250 nm or by collision-induced dissociation, and further interrogated by CID and UVPD-MS3. Peptide fragment ion series originating from linear structures and macrocyclic cross-links were distinguished and used to quantify the cross-linking yields. The yields in MS2 varied between 27% for AAAG conjugates to 78% for GAAAK conjugates, depending on the peptide sequence. The CID-MS3 yields were in a 57-97% range, depending on the peptide sequence. Structures of 1,2-s-peptide and 1,4-s-peptide ions as well as several of their nitrile-imine intermediates and cross-links were investigated by high-resolution cyclic ion mobility in combination with Born-Oppenheimer molecular dynamics and density functional theory calculations. Matches between the experimental and calculated collision cross sections and ion relative Gibbs energies were used to assign peptide structures. Peptide conjugates C-terminated with Gly and Lys residues underwent cross-linking by the carboxyl group, as established by MS3 sequencing and corroborated by carboxyl blocking experiments that lowered the cross-linking yields. Peptide conjugates C-terminated with Arg also cross-linked via the side-chain guanidine group. A notable feature of the 1,4-s-peptide ions was the participation of low-energy twist-boat cyclohexane conformers that was enforced by strong hydrogen bonds between the peptide and nitrile imine.

Design and investigation of novel iridoid-based peptide conjugates for targeting EGFR and its mutants L858R and T790M/L858R/C797S: an in silico study.

In this work, we designed novel peptide conjugates with plant-based iridoid and lichen-derived depside derivatives to target the wild-type EGFR (WT) and its mutants, L858R and T790M/L858R/C797S triple mutant. These mutations are often expressed in multiple cancers, particularly lung cancer. Specifically, the iridoids included 7-deoxyloganetic acid (7-DGA) and loganic acid (LG), while the depside derivative was sekikaic acid (SK). These compounds are known for their innate anticancer properties and were conjugated with two separate peptide sequences KLPGWSG (K) and YSIPKSS (Y). These sequences have been shown to target EGFR in previous phage display library screening, although the mechanism is unknown. Thus, we created the di-conjugates for dual targeting and investigated their interactions of the di-conjugates and that of the neat peptides with the kinase domain of EGFR (WT) and the two mutants using molecular docking, molecular dynamics (MD) simulations, and MM-GBSA analysis. Docking studies revealed that the (7-DGA)2-K showed the highest binding affinity at - 9.3kcal/mol with the L858R mutant, while (LG)2-Y displayed the highest binding affinity at - 9.0kcal/mol for the triple mutant receptor. Our results indicated that several of the conjugates interacted with crucial residues of the kinase domain, including ASP855 and THR854 (activation loop), MET793 and PRO794 (hinge region), ARG841 (catalytic loop), and LYS728 and LEU718 of the glycine-rich P-loop. Interestingly, strong hydrophobic interactions were also observed with the C-terminal tail residues, such as PHE997 and ALA1000 as well as with ARG999 for the YSIPKSS peptide and most of the conjugates. The hydroxyl group of the cyclopentane ring and the oxygen of the pyran ring of the (7-DGA)2-peptide conjugates contributed to binding particularly in the hinge region, while the peptide components formed an extended structure that bound well into the C-lobe. The (SK)2-Y di-conjugate and KLPGWSG peptide formed hydrogen bonds with the SER797 residue of the triple mutant. Overall, our results show that the (7-DGA)2-K, di-conjugate, the (7-DGA)2-Y di-conjugate, and the neat YSIPKSS demonstrated strong and stable binding with the L858R mutant and the highly resistant triple mutant EGFR, respectively. The novel designed conjugates demonstrate potential for further optimization for laboratory studies aimed at developing new therapeutics for targeting specific EGFR mutant expressing cells.

Introducing Chemoselective Peptide Conjugation via N-Alkylation of Pyridyl-alanine: Solution and Solid Phase Applications.

A novel chemoselective peptide conjugation via late-stage N-alkylation of pyridyl-alanine (PAL) in the solution and solid phase, namely, NAP, is demonstrated. The method constructs functionally diverse and highly stable N-alkylated conjugates with various peptides. Notably, conjugations in the solid phase offered a more economical process. The method can provide the opportunity for dual labeling along with a cysteine handle in a peptide chain. Finally, we showcased that the antiproliferative activities of the p53 peptide (MDM2 inhibitor) could be 2-fold enhanced via NAP conjugation with the RGD peptide (selective integrin binder).

Peptide-mediated targeting of Quantum Dots in a 3D model of head and neck cancer

BackgroundOral squamous cell carcinoma (OSCC) treatment mainly relies on surgery. The status of surgical margin is a major prognostic factor for patients as positive margins are associated with lower survival. However, the anatomical particularities of this area complicate margin establishment. Fluorescence guided surgery (FGS) could be employed as an intraoperative technique to improve tumor resection and margin investigation. Quantum dots (QDs) serve as ideal contrast agents in this technique due to their brightness and stability. Since αVβ6 integrin is overexpressed in OSCC, coupling QDs with A20FMDV2 peptide (QDs-A20) targeting the αVβ6 integrin constitute a real opportunity. This study investigates the accumulation of QDs-A20 in 2D and 3D tongue cancer models, as well as QDs coupled to a scrambled version of this peptide (QDs-Scr) or without peptide (QDs-SPP), for imaging purposes. MethodsCdSeCdS/ZnS quantum dots were coated with sulfobetaine polymers (QDs-SPP) and conjugated to A20FMDV2 peptide (QDs-A20) or its scrambled version (QDs-Scr). Two-dimensional (2D) and three-dimensional (3D) tongue cancer cells HSC-3 were employed to test the effectiveness of intracellular accumulation of all types of QDs. Targeting ability of each QDs was assessed by flow cytometry, while the depth of penetration into cancerous spheroids was assessed by fluorescence microscopy. ResultsQDs coating with sulfobetaines polymers (QDs-SPP) completely prevented their internalization by HSC-3 cells in 2D and 3D models, making QDs stealthy and preventing their non-specific accumulation. Conversely, peptides conjugated QDs (QDs-A20 & QDs-Scr) labeled HSC-3 monolayers and managed to label spheroid periphery up to 23 µm deep. However, no difference in accumulation was found between these two QDs whereas only A20 peptide could potentially target αVβ6 integrin. It appears that peptide conjugation increased QDs zeta potential, promoting their adsorption and subsequent endocytosis by cells, independently from αVβ6 integrin. ConclusionsThe present study highlighted the impact of peptide conjugation on QDs internalization in 2D and 3D tongue cancer cell models. QDs-SPP were stealthy and did not accumulate in cells. Peptides conjugated QDs could be used as contrast agents, but in a passive targeting approach. Modifications to surface chemistry are required to target αVβ6 integrin through active targeting. This study also highlights the need for controls such as scrambled peptides, the absence of which can lead to misinterpretation of results.

Biological Activities of Soy Protein Hydrolysate Conjugated with Mannose and Allulose.

The non-enzymatic conjugation of peptides through the Maillard reaction has gained attention as an effective method to enhance biological functions. This study focuses on two conjugate mixtures: crude soy protein hydrolysate (SPH) conjugated with mannose (SPHM) and crude soy protein hydrolysate conjugated with allulose (SPHA). These two mixtures were products of the Maillard reaction, also known as non-enzymatic glycation. In vitro experiments were conducted to evaluate the antioxidant, anti-pancreatic lipase, inhibition of Bovine Serum Albumin (BSA) denaturation, and anti-angiotensin converting enzyme (ACE) activities of these conjugated mixtures. The results indicate that conjugated mixtures significantly enhance the antioxidant potential demonstrated via the DPPH and FRAP assays. SPHA exhibits superior DPPH scavenging activity (280.87 ± 16.39 µg Trolox/mL) and FRAP value (38.91 ± 0.02 mg Trolox/mL). Additionally, both conjugate mixtures, at a concentration of 10 mg/mL, enhance the BSA denaturation properties, with SPHM showing slightly higher effectiveness compared to SPHA (19.78 ± 2.26% and 5.95 ± 3.89%, respectively). SPHA also shows an improvement in pancreatic lipase inhibition (29.43 ± 1.94%) when compared to the SPHM (23.34 ± 3.75%). Furthermore, both the conjugated mixtures and rare sugars exhibit ACE inhibitory properties on their own, effectively reducing ACE activity. Notably, the ACE inhibitory effects of the individual compounds and their conjugate mixtures (SPHM and SPHA) are comparable to those of positive control (Enalapril). In conclusion, SPHM and SPHA demonstrate a variety of bioactive properties, suggesting their potential use in functional foods or as ingredients in supplementary products.

Acid-activatable photosensitizers for photodynamic therapy using self-aggregates of chlorophyll‒peptide conjugates

AbstractPhotodynamic therapy is useful due to its high antitumor efficacy, spatiotemporal selectivity, and noninvasiveness and has garnered significant attention in the field of cancer treatment. When photoexcited by light irradiation, photosensitizers produce reactive oxygen species (ROS) that damage tumor tissues. However, photosensitizers can also accumulate in normal tissues, leading to side effects such as skin photosensitivity. To mitigate these side effects, we report the development of chlorophyll‒peptide conjugates as tumor-selective photosensitizers. These conjugates bearing histidine and lysine residues self-assemble into nanoparticles that are expected to accumulate selectively in tumors and reduce ROS generation through self-quenching under the neutral conditions typical of normal tissues. In contrast, these aggregated conjugates partially disassemble under weakly acidic conditions, such as those found in tumor tissues, resulting in phototoxicity. We anticipate that these acid-activatable conjugates have the potential to serve as cancer-selective photosensitizers, thereby reducing phototoxicity in normal tissues.

Combination of the amide-to-triazole substitution strategy with alternative structural modifications for the metabolic stabilization of tumor-targeting, radiolabeled peptides.

Radiolabeled peptides play a key role in nuclear medicine to selectively deliver radionuclides to malignancies for diagnosis (imaging) and therapy. Yet, their efficiency is often compromised by low metabolic stability. The use of 1,4-disubstituted 1,2,3-triazoles (1,4-Tzs) as stable amide bond bioisosteres can increase the half-life of peptides in vivo while maintaining their biological properties. Previously, the amide-to-triazole substitution strategy was used for the stabilization of the pansomatostatin radioligand [111In]In-AT2S, resulting in the mono-triazolo-peptidomimetic [111In]In-XG1, a radiotracer with moderately enhanced stability in vivo and retained ability to bind multiple somatostatin receptor (SSTR) subtypes. However, inclusion of additional 1,4-Tz led to a loss of affinity towards SST2R, the receptor overexpressed by most SSTR-positive cancers. To enhance further the stability of [111In]In-XG1, alternative modifications at the enzymatically labile position Thr10-Phe11 were employed. Three novel 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-peptide conjugates were synthesized with a 1,4-Tz (Asn5-Ψ[Tz]-Phe6) and either a β-amino acid (β-Phe11), reduced amide bond (Thr10-Ψ[NH]-Phe11), or N-methylated amino acid (N-Me-Phe11). Two of the new peptidomimetics were more stable in blood plasma in vitro than [111In]In-XG1. Yet none of them retained high affinity towards SST2R. We demonstrate for the first time the combination of the amide-to-triazole substitution strategy with alternative stabilization methods to improve the metabolic stability of tumor-targeting peptides.

Bismuth-Cyclized Cell-Penetrating Peptides.

Intracellular delivery of biological cargos, which would yield new research tools and novel therapeutics, remains an active area of research. A convenient and potentially general approach involves the conjugation of a cell-penetrating peptide to a cargo of interest. However, linear CPPs lack sufficient cytosolic entry efficiency and metabolic stability, while previous backbone cyclized CPPs have several drawbacks including the necessity for chemical synthesis and posttranslational conjugation to peptide/protein cargos and epimerization during cyclization. We report here a new class of bismuth cyclized CPPs with excellent cytosolic entry efficiencies, proteolytic stability, and potential compatibility with genetic encoding and recombinant production.

Enhanced tumor targeting and penetration of fluorophores via iRGD peptide conjugation: a strategy for the precision targeting of lung cancer.

Accurate real-time tumor delineation is essential for achieving curative resection (R0 resection) during non-small cell lung cancer (NSCLC) surgery. The unique characteristics of lung tissue structure significantly challenge the use of video-assisted thoracoscopic surgery in the identification of lung nodules. This difficulty often results in an inability to discern the margins of lung nodules, necessitating either an expansion of the resection scope, or a transition to open surgery. Due to its high spatial resolution, ease of operation, and capacity for real-time observation, near-infrared fluorescence (NIRF) navigation in oncological surgery has emerged as a focal point of clinical research. Targeted NIRF probes, which accumulate preferentially in tumor tissues and are rapidly cleared from normal tissues, enhance diagnostic sensitivity and surgical outcomes. The imaging effect of the clinically approved NIRF probe indocyanine green (ICG) varies significantly from person to person. Therefore, we hope to develop a new generation of targeted NIRF probes targeting lung tumor-specific targets. First, the peptide iRGD (sequence: CRGDKGPDC) fluorescent tracer was synthesized, and characterized through mass spectrometry (MS), proton nuclear magnetic resonance (1H NMR), and high-performance liquid chromatography (HPLC). Fluorescence properties were tested subsequently. Safety was performed in vitro using both human normal liver cells and human normal breast cells. Second, Metabolism and optimal imaging time were determined by tail vein injection of iRGD fluorescent tracer. Finally, Orthotopic and metastatic lung tumor models were used to evaluate the targeting properties of the iRGD fluorescent tracer. We successfully synthesized an iRGD fluorescent tracer specifically designed to target NSCLC. The molecular docking analyses indicated that this tracer has receptor affinity comparable to that of iRGD for αvβ3 integrin, with a purity ≥98%. Additionally, the tracer is highly soluble in water, and its excitation and emission wavelengths are 767 and 799 nm, respectively, positioning it within the near-infrared spectrum. The cellular assays confirmed the tracer's minimal cytotoxicity, underscoring its excellent biosafety profile. In vivo studies further validated the tracer's capacity for specific NSCLC detection at the cellular level, alongside a prolonged imaging window of 6 days or more. Notably, the tracer demonstrated superior specificity in localizing very small lung nodules, which are otherwise clinically indiscernible, outperforming non-targeted ICG. Fluorescence intensity analyses across various organs revealed that the tracer is predominantly metabolized by the liver and kidneys, with excretion via bile and urine, and exhibits minimal toxicity to these organs as well as the lungs. The iRGD fluorescent tracer selectively accumulates in NSCLC tissues by specifically targeting αvβ3 receptors, which are overexpressed on the surface of tumor cells. This targeted approach facilitates the real-time intraoperative localization of NSCLC, presenting an improved strategy for intraoperative tumor identification with significant potential for clinical application.

Conjugation of CRAMP18-35 Peptide to Chitosan and Hydroxypropyl Chitosan via Copper-Catalyzed Azide-Alkyne Cycloaddition and Investigation of Antibacterial Activity.

We developed a synthesis strategy involving a diazo transfer reaction and subsequent click reaction to conjugate a murine cathelicidin-related antimicrobial peptide (CRAMP18-35) to chitosan and hydroxypropyl chitosan (HPC), confirmed the structure, and investigated the antimicrobial activity. Chitosan azide and HPC-azide were prepared with a low degree of azidation by reacting the parent chitosan and HPC with imidazole sulfonyl azide hydrochloride. CRAMP18-35 carrying an N-terminal pentynoyl group was successfully grafted onto chitosan and HPC via copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The chitosan-peptide conjugates were characterized by IR spectroscopy and proton NMR to confirm the conversion of the azide to 1,2,3-triazole and to determine the degree of substitution (DS). The DS of the chitosan and HPC CRAMP18-35 conjugates was 0.20 and 0.13, respectively. The antibacterial activity of chitosan-peptide conjugates was evaluated for activity against two species of Gram-positive bacteria, Staphylococcus aureus (S. aureus) and Enterococcus faecalis (E. faecalis), and two species of Gram-negative bacteria, Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa). The antimicrobial peptide conjugates were selectively active against the Gram-negative bacteria and lacking activity against Gram-positive bacteria.

Investigation of the cytotoxic and antimicrobial properties of new quinoline peptide conjugates

Background: Cancer is one of the most important health problems causing deaths in Turkey and the world. Nowadays, many treatment methods such as radiotherapy and chemotherapy are applied in cancer patients. Quinoline and its derivatives, which belong to heterocyclic compounds, have many biological activities for drug development. Quinoline compounds play a crucial role in the development of antitumor drugs due to their anticancer activity. Materials and Methods: In this study, the cytotoxic effects of synthesized seven different quinoline derivatives on lung cancer (A549) and healthy lung epithelial cell (BEAS2B), liver cancer (Hep 3B), and endothelial cell (HUVEC) were determined. Different concentrations were applied and IC50 values were calculated at different time courses. The antimicrobial activites of the compounds were also determined. Results: The IC50 values of compound 2 on the A549 cell line were determined to be 10.48 μg/mL, 9.738 μg/mL, and 10.14 μg/mL. IC50 values of compound 6 on the same cell line were determined to be 7.307 µg/mL, 9.888 µg/mL, 10.63 µg/mL. Conclusions: Compounds 2 and 6 had a cytotoxic effect on the BEAS2B cell line. The antimicrobial activity of the compounds was determined by the minimum inhibition concentration method on different strains of bacteria and yeast. The compounds showed no antimicrobial activity on bacteria and yeast.

Dual Antibiotic Approach: Synthesis and Antibacterial Activity of Antibiotic-Antimicrobial Peptide Conjugates.

In recent years, bacterial resistance to conventional antibiotics has become a major concern in the medical field. The global misuse of antibiotics in clinics, personal use, and agriculture has accelerated this resistance, making infections increasingly difficult to treat and rendering new antibiotics ineffective more quickly. Finding new antibiotics is challenging due to the complexity of bacterial mechanisms, high costs and low financial incentives for the development of new molecular scaffolds, and stringent regulatory requirements. Additionally, innovation has slowed, with many new antibiotics being modifications of existing drugs rather than entirely new classes. Antimicrobial peptides (AMPs) are a valid alternative to small-molecule antibiotics offering several advantages, including broad-spectrum activity and a lower likelihood of inducing resistance due to their multifaceted mechanisms of action. However, AMPs face challenges such as stability issues in physiological conditions, potential toxicity to human cells, high production costs, and difficulties in large-scale manufacturing. A reliable strategy to overcome the drawbacks associated with the use of small-molecule antibiotics and AMPs is combination therapy, namely the simultaneous co-administration of two or more antibiotics or the synthesis of covalently linked conjugates. This review aims to provide a comprehensive overview of the literature on the development of antibiotic-AMP conjugates, with a particular emphasis on critically analyzing the design and synthetic strategies employed in their creation. In addition to the synthesis, the review will also explore the reported antibacterial activity of these conjugates and, where available, examine any data concerning their cytotoxicity.

Synthetic Strategies to Prepare Bioactive Lysine and Peptide Conjugates With Triazolium Derivatives

AbstractPeptides conjugated with organic molecules can be useful tools for the development of novel bioactive compounds. The lysine side‐chain is an interesting functional group to act as a linker to connect small molecules in peptide conjugates. Herein we present the design and synthesis of four Safirinium derivatives, their facile conjugation to lysine in solid phase, and incorporation in peptides. The compounds differing in the functionalization of nitrogen N2 of the condensed triazolyl moiety are novel building blocks to design conjugates to perform structure‐activity relationship studies of elastase inhibitors. Consequently, structural investigations of the lysine building blocks and of the corresponding peptide conjugates were performed. We present herein the potential of the Safirinium analogs to act as elastase inhibitors in assays performed on porcine pancreas elastase.

Anti-Inflammatory, Cytotoxic, and Genotoxic Effects of Soybean Oligopeptides Conjugated with Mannose.

Soy protein is considered to be a high-quality protein with a range of important biological functions. However, the applications of soy protein are limited due to its poor solubility and high level of allergenicity. Its peptides have been of interest because they exert the same biological functions as soy protein, but are easier to absorb, more stable and soluble, and have a lower allergenicity. Moreover, recent research found that an attachment of chemical moieties to peptides could improve their properties including their biodistribution, pharmacokinetic, and biological activities with lower toxicity. This study therefore aimed to acquire scientific evidence to support the further application and safe use of the soybean oligopeptide (OT) conjugated with allulose (OT-AL) or D-mannose (OT-Man). The anti-inflammation, cytotoxicity, and genotoxicity of OT, OT-AL, and OT-Man were investigated. The results showed that OT, AL, Man, OT-AL, and OT-Man at doses of up to 1000 µg/mL were not toxic to HepG2 (liver cancer cells), HEK293 (kidney cells), LX-2 (hepatic stellate cells), and pre- and mature-3T3-L1 (fibroblasts and adipocytes, respectively), while slightly delaying the proliferation of RAW 264.7 cells (macrophages) at high doses. In addition, the oligopeptides at up to 800 µg/mL were not toxic to isolated human peripheral blood mononuclear cells (PBMCs) and did not induce hemolysis in human red blood cells (RBCs). OT-Man (200 and 400 µg/mL), but not OT, AL, Man, and OT-AL, significantly reduced the production of NO and the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX2) stimulated by lipopolysaccharide (LPS) in RAW 264.7 cells, suggesting that the mannose conjugation of soy peptide had an inhibitory effect against LPS-stimulated inflammation. In addition, the secretion of interleukin-6 (IL-6) stimulated by LPS was significantly reduced by OT-AL (200 and 400 µg/mL) and OT-Man (400 µg/mL). The tumor necrosis factor-α (TNF-α) level was significantly decreased by OT (400 µg/mL), AL (400 µg/mL), OT-AL (200 µg/mL), and OT-Man (200 and 400 µg/mL) in the LPS-stimulated cells. The conjugation of the peptides with either AL or Man is likely to be enhance the anti-inflammation ability to inhibit the secretion of cytokines. As OT-Man exhibited a high potential to inhibit LPS-induced inflammation in macrophages, its mutagenicity ability was then assessed in bacteria and Drosophila. These findings showed that OT-Man did not trigger DNA mutations and was genome-safe. This study provides possible insights into the health advantages and safe use of conjugated soybean peptides.

2‐DPC Mediated Effective Synthesis of Peptide Conjugates, their Antifungal and Antibacterial Properties

AbstractThe present work demonstrates the effective synthesis of amide derivatives of Nα‐protected amino acids and aryl/heteroaryl amines using di‐2‐pyridyl carbonate (2‐DPC) and cat. DMAP mediated coupling reaction. Several coupling methods were employed for the screening of the amides using EDC, HATU, mixed anhydride, T3P, CDI, COMU, DPTC, and 2‐DPC, where 2‐DPC/cat. DMAP method furnished amides with better yields and purity in shorter durations. Seventeen amide derivatives (3 a–3 q) were successfully synthesized using the present protocol and were characterized by NMR, mass and IR spectroscopy. Further, we performed the in‐silico and in‐vitro studies on the synthesized molecules on antifungal and antibacterial activity. Molecular docking studies reveal the binding affinity of protein‐ligand interactions ranging from −6.2 to −11.0 kcal/mol (Aspergillus Niger Esta), −5.9 to −9.9 kcal/mol (DNA gyrase subunit B) and −6.4 to −13.4 kcal/mol (CYP51B). Compounds like 3 d, 3 e, 3 h, 3 i, 3 j and 3 l exhibit the highest antibacterial and antifungal activity when compared to the standards delafloxacin, ketoconazole, and bifonazole in in‐silico studies. Whereas the in‐vitro studies also unveiled good antimicrobial activity with peptide conjugates. The results of antimicrobial activity exhibits in antifungal species show the good activity concentrations in compounds 3 j is 11.2±3.54 μg/mL and 3 l is 10.3±2.76 μg/mL. The anti‐bacterial species exhibit the compound 3 g showing good activity in different concentrations 12±3.08 μg/mL, 12.2±3.04 μg/mL, 12.6±2.78 μg/mL and 12.5±2.98 μg/mL.

Breaking Down the Barriers of Drug Resistance and Corneal Permeability with Chitosan-Poly(ethylene glycol)-LK13 Peptide Conjugate to Combat Fungal Keratitis.

Fungal keratitis (FK) is a leading cause of preventable blindness and eye loss. The poor antifungal activity, increased drug resistance, limited corneal permeability, and unsatisfactory biosafety of conventional antifungal eye drops are among the majority of the challenges that need to be addressed for currently available antifungal drugs. Herein, this study proposes an effective strategy that employs chitosan-poly(ethylene glycol)-LK13 peptide conjugate (CPL) in the treatment of FK. Nanoassembly CPL can permeate the lipophilic corneal epithelium in the transcellular route, and its hydrophilicity surface is a feature to drive its permeability through hydrophilic stroma. When encountering fungal cell membrane, CPL dissembles and exposes the antimicrobial peptide (LK13) to destroy fungal cell membranes, the minimum inhibitory concentration values of CPL against Fusarium solani (F. solani) are always not to exceed 8 μg peptide/mL before and after drug resistance induction. In a rat model of Fusarium keratitis, CPL demonstrates superior therapeutic efficacy than commercially available natamycin ophthalmic suspension. This study provides more theoretical and experimental supports for the application of CPL in the treatment of FK.

Peptide-IR820 Conjugate: A Promising Strategy for Efficient Vascular Disruption and Hypoxia Induction in Melanoma.

Photothermal therapy (PTT) has emerged as a noninvasive and precise cancer treatment modality known for its high selectivity and lack of drug resistance. However, the clinical translation of many PTT agents is hindered by the limited biodegradability of inorganic nanoparticles and the instability of organic dyes. In this study, a peptide conjugate, IR820-Cys-Trp-Glu-Trp-Thr-Trp-Tyr (IR820-C), was designed to self-assemble into nanoparticles for both potent PTT and vascular disruption in melanoma treatment. When co-assembled with the poorly soluble vascular disrupting agent (VDA) combretastatin A4 (CA4), the resulting nanoparticles (IR820-C@CA4 NPs) accumulate efficiently in tumors, activate systemic antitumor immune responses, and effectively ablate melanoma with a single treatment and near-infrared irradiation, as confirmed by our in vivo experiments. Furthermore, by exploiting the resulting tumor hypoxia, we subsequently administered the hypoxia-activated prodrug tirapazamine (TPZ) to capitalize on the created microenvironment, thereby boosting therapeutic efficacy and antimetastatic potential. This study showcases the potential of short-peptide-based nanocarriers for the design and development of stable and efficient photothermal platforms. The multifaceted therapeutic strategy, which merges photothermal ablation with vascular disruption and hypoxia-activated chemotherapy, holds great promise for advancing the efficacy and scope of cancer treatment modalities.

Effects of alloferon and its analogues on reproduction and development of the Tenebrio molitor beetle

As the most numerous group of animals on Earth, insects are found in almost every ecosystem. Their useful role in the environment is priceless; however, for humans, their presence may be considered negative or even harmful. For years, people have been trying to control the number of pests by using synthetic insecticides, which eventually causes an increased level of resistance to applied compounds. The effects of synthetic insecticides have encouraged researchers to search for alternatives and thus develop safe compounds with high specificity. Using knowledge about the physiology of insects and the functionality of compounds of insect origin, a new class of bioinsecticides called peptidomimetics, which are appropriately modified insect analogues, was created. One promising compound that might be successfully modified is the thirteen amino acid peptide alloferon (HGVSGHGQHGVHG), which is obtained from the hemolymph of the blue blowfly Calliphora vicinia. Our research aimed to understand the physiological properties of alloferon and the activity of its peptidomimetics, which will provide the possibility of using alloferon or its analogues in the pharmaceutical industry, as a drug or adjuvant, or in agriculture as a bioinsecticide. We used alloferon and its three peptidomimetics, which are conjugates of the native peptide with three unsaturated fatty acids with various chain lengths: caprylic, myristic, and palmitic. We tested their effects on the morphology and activity of the reproductive system and the embryogenesis of the Tenebrio molitor beetle. We found that the tested compounds influenced the growth and maturation of ovaries and the expression level of the vitellogenin gene. The tested compounds also influenced the process of egg laying, embryogenesis, and offspring hatching, showing that alloferon might be a good peptide for the synthesis of effective bioinsecticides or biopharmaceuticals.

Enhanced native chemical ligation by peptide conjugation in trifluoroacetic acid.

Chemical ligation of peptides is increasingly used to generate proteins not readily accessible by recombinant approaches. However, a robust method to ligate "difficult" peptides remains to be developed. Here, we report an enhanced native chemical ligation strategy mediated by peptide conjugation in trifluoroacetic acid (TFA). The conjugation between a carboxyl-terminal peptide thiosalicylaldehyde thioester and a 1,3-dithiol-containing peptide in TFA proceeds rapidly to form a thioacetal-linked intermediate, which is readily converted into the desired native amide bond product through simple postligation treatment. The effectiveness and practicality of the method was demonstrated by the successful synthesis of several challenging proteins, including the SARS-CoV-2 transmembrane Envelope (E) protein and nanobodies. Because of the ability of TFA to dissolve virtually all peptides and prevent the formation of unreactive peptide structures, the method is expected to open new opportunities for synthesizing all families of proteins, particularly those with aggregable or colloidal peptide segments.

Imparting Stability to Chiral Helical Gold Nanoparticle Superstructures.

Realizing the promise of chiral inorganic nanomaterials hinges on improving their structural stability under various chemical and environmental conditions. Here, we examine the stability of 1-D gold nanoparticle (Au NP) single helices prepared using the amphiphilic peptide conjugate Cx-(PEPAuM-ox)2 (PEPAuM-ox = AYSSGAPPMoxPPF; x = 16-22). We present a general template-independent strategy of tuning helix stability that relies on controlling the dimensions of constituent NPs. As NP dimensions increase, Au NP single helices become both more thermally stable and more stable in the presence of chemical denaturants and protein digestion agents (e.g., urea and proteinase K, respectively). We use this strategy for imparting helix stability to create colloidal suspensions of thermally robust Au NP single helices which maintain their plasmonic chiroptical activity up to ∼80 °C.