Cyclic Peptide Research Articles

Tackling Undruggable Targets with Designer Peptidomimetics and Synthetic Biologics.

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

Binding Mode of Cyclic Chemerin-9 Peptide and ChemerinS157 Protein at CMKLR1.

The chemokine-like receptor 1 (CMKLR1) is activated by the adipokine and chemoattractant protein chemerin. Cryo-EM structures of chemerin-9-CMKLR1-Gi have been published, where chemerin-9 is the nonapeptide of the C terminus of chemerinS157. Chemerin-9 is as active as the full-length protein in Ca2+-release but shows differences in equilibrium read-outs. An equally potent cyclic chemerin-9 variant (cC9) was reported previously. Now, we have built a computational model of CMKLR1 to investigate the binding mode of cC9 and chemerinS157 in comparison to chemerin-9. Differences were investigated using CMKLR1 variants. Double-mutant cycle analysis identified CMKLR1-F2.53 as the relevant position for Phe8-binding of cC9. Energy contribution revealed slight differences in Phe8-binding to CMKLR1-F2.53 and space for larger residues. This was confirmed as the chemerin-9 variant with 1-naphthyl-L-alanine at position 8 showed a 4-fold increased potency of 2 nM (pEC50=8.6±0.15). While chemerin-9 and cC9 share their interactions at the CMKLR1, chemerinS157 tolerates most mutations of CMKLR1 in the deep binding site. The computational model of chemerinS157 suggests a β-sheet interaction between the N-terminal CMKLR1-segment I25VVL28 and the β-sheet D108KVLGRLVH116 of ChemS157, which was confirmed experimentally. Our data add to the knowledge by identifying the binding mode of chemerinS157 and cC9 at CMKLR1, facilitating the future structure-based drug design.

Long-Range Proton Channels Constructed via Hierarchical Peptide Self-Assembly.

The quest to understand and mimic proton translocation mechanisms in natural channels has driven the development of peptide-based artificial channels facilitating efficient proton transport across nanometric membranes. It is demonstrated here that hierarchical peptide self-assembly can form micrometers-long proton nanochannels. The fourfold symmetrical peptide design leverages intermolecular aromatic interactions to align self-assembled cyclic peptide nanotubes, creating hydrophilic nanochannels between them. Titratable amino acid sidechains are positioned adjacent to each other within the channels, enabling the formation of hydrogen-bonded chains upon hydration, and facilitating efficient proton transport. Moreover, these chains are enriched with protons and water molecules by interacting with immobile counter ions introduced into the channels, increasing proton flow density and rate. This system maintains proton transfer rates closely resembling those in natural protein channels over micrometer distances. The functional behavior of these inherently recyclable and biocompatible systems opens the door for their exploitation in diverse applications in energy storage and conversion, biomedicine, and bioelectronics.

Allelopathic activity of cyanobacteria isolated from Lake Tuzkol.

Allelopathy plays a crucial role in shaping phytoplankton community dynamics and diversity. It influences competition between photoautotrophs for resources and affects species succession in aquatic ecosystems. This article evaluates the allelopathic activity of cyanobacteria isolated from Lake Tuzkol, Kazakhstan. The allelopathic effects, including growth inhibition or stimulation, were assessed by adding cell-free filtrates of the cyanobacteria Oscillatoria sp. SS-9, Nostoc sp. CZS 2205, Synechococcus sp. SS-5, or Anabaena sp. SS-8 to the tested microalgae. The most pronounced effect was observed with Nostoc sp. CZS 2205, which reduced the cell counts of Chlorella vulgaris SP BB-2 and Chlamydomonas reinhardtii CC-124 by 60% and 57%, respectively, and Scenedesmus quadricauda CC-1 and Ankistrodesmus falcatus CB-2 by 55% and 53%, respectively. Synechococcus sp. SS-5, in contrast, stimulated the growth of Chlorella vulgaris SP BB-2 and Scenedesmus quadricauda CC-1 by 11% and 8.8%, respectively. Filtrates from Oscillatoria sp. SS-9 and Anabaena sp. SS-8 had no significant impact on microalgal growth. Considering the significant allelopathic activity of Nostoc sp. CZS 2205, an agar diffusion test using biomass extracts confirmed a significant inhibitory effect, with the biomass extracts showing stronger activity than cell-free filtrates. A detailed analysis of the cell-free filtrates revealed eight compounds, including methyl heptadecanoate, methyl eicosanoate, tricosane, methyl octadeca-9,12-dienoate, methyl 13,16-octadecadienoate, and 2,2-dimethoxybutane. Additionally, nostocyclamide, a cyclic peptide, was identified in the biomass extract. The detection of nostocyclamide emphasizes its ecological importance and potential evolutionary role. These results enhance our understanding of the role of cyanobacteria in aquatic ecosystems and lay the groundwork for future research into their ecological applications.

Investigating Ligand-Mediated Conformational Dynamics of Pre-miR21: A Machine-Learning-Aided Enhanced Sampling Study.

MicroRNAs (miRs) are short, noncoding RNA strands that regulate the activity of mRNAs by affecting the repression of protein translation, and their dysregulation has been implicated in several pathologies. miR21 in particular has been implicated in tumorigenesis and anticancer drug resistance, making it a critical target for drug design. miR21 biogenesis involves precise biochemical pathways, including the cleavage of its precursor, pre-miR21, by the enzyme Dicer. The present work investigates the conformational dynamics of pre-miR21, focusing on the role of adenine29 in switching between Dicer-binding-prone and inactive states. We also investigated the effect of L50, a cyclic peptide binder of pre-miR21 and a weak inhibitor of its processing. Using time series data and our novel collective variable-based enhanced sampling technique, OneOPES, we simulated these conformational changes and assessed the effect of L50 on the conformational plasticity of pre-miR21. Our results provide insight into peptide-induced conformational changes and pave the way for the development of a computational platform for the screening of inhibitors of pre-miR21 processing that considers RNA flexibility, a stepping stone for effective structure-based drug design, with potentially broad applications in drug discovery.

DDDR-18. TARGETTING GLIOBLASTOMA MULTIFORME USING A MULTIACTION ANTICANCER ANTI-INFLAMMATORY THERAPEUTIC STRATEGY

Abstract Glioblastoma multiforme (GBM) represents a significant challenge in adult brain tumor management, characterized by its aggressive nature and poor prognosis despite multimodal therapies. Current standard chemotherapy, Temozolomide (TMZ), offers limited survival benefits. In a recent breakthrough, the cyclic peptide cyclo-((2-Nal)-Leu-Ser-(2-Nal)-Arg) acetate (c2), initially developed for prostate cancer, demonstrates remarkable promise against GBM. By selectively inhibiting the inflammatory phospholipase enzyme sPLA2IIA, c2 significantly impedes GBM cell proliferation, surpassing TMZ efficacy in multiple resistant cell lines. Moreover, c2 exhibits potential to inhibit tumor growth and metastasis, confirmed in 3D tumoroid and wound healing assays. Mechanistic insights reveal modulation of crucial cellular pathways, including viral entry, cytoskeletal structure, and signaling cascades. Preclinical investigations demonstrate c2’s ability to penetrate the blood-brain barrier and attenuate tumor progression markers. At multiple levels, c2 is shown to target inhibition of ERBB2 and EGFR signalling and also have impacts on HIF1-NF-kB axis. This study proposes c2 as a potent anti-GBM candidate, warranting evaluations for its pharmacological profile, safety, and efficacy. With its potential to address the urgent need for effective GBM therapies, c2 holds promise as a significant advancement in GBM treatment, offering hope for improved patient outcomes.

A cyclic peptide toolkit reveals mechanistic principles of peptidylarginine deiminase IV regulation.

Peptidylarginine deiminase IV (PADI4, PAD4) deregulation promotes the development of autoimmunity, cancer, atherosclerosis and age-related tissue fibrosis. PADI4 additionally mediates immune responses and cellular reprogramming, although the full extent of its physiological roles is unexplored. Despite detailed molecular knowledge of PADI4 activation in vitro, we lack understanding of its regulation within cells, largely due toa lack of appropriate systems and tools. Here, we develop and apply a set of potent and selective PADI4 modulators. Using the mRNA-display-based RaPID system, we screen >1012 cyclic peptides for high-affinity, conformation-selective binders. We report PADI4_3, a cell-active inhibitor specific for the active conformation of PADI4; PADI4_7, an inert binder, which we functionalise for the isolation and study of cellular PADI4; and PADI4_11, a cell-active PADI4 activator. Structural studies with PADI4_11 reveal an allosteric binding mode that may reflect the mechanism that promotes cellular PADI4 activation. This work contributes to our understanding of PADI4 regulation and provides a toolkit for the study and modulation of PADI4 across (patho)physiological contexts.

Rapid Microfluidic Biosensor for Point-of-Care Determination of Rheumatoid Arthritis via Anti-Cyclic Citrullinated Peptide Antibody Detection

Rheumatoid arthritis (RA) is a chronic autoimmune disorder that causes extensive damage to multiple organs and tissues and has no known cure. This study introduces a microfluidic detection platform that combines a microfluidic reaction chip with a micro-spectrometer to accurately detect the anti-cyclic citrullinated peptide antibody (anti-CCP Ab) biomarker, commonly associated with arthritis. The surface of the microfluidic reaction chip is functionalized using streptavidin to enable the subsequent immobilization of biotinylated-labeled cyclic citrullinated peptide (biotin–CCP) molecules through a streptavidin–biotin reaction. The modified chip is then exposed to anti-CCP Ab, second antibody conjugated with horseradish peroxidase (HRP) (2nd Ab-HRP), 3,3′,5,5′-tetramethylbenzidine (TMB), and a stop solution. Finally, the concentration of the anti-CCP Ab biomarker is determined by analyzing the optical density (OD) of the colorimetric reaction product at 450 nm using a micro-spectrometer. The detection platform demonstrated a strong correlation (R2 = 0.9966) between OD and anti-CCP Ab concentration. This was based on seven control samples with anti-CCP Ab concentrations ranging from 0.625 to 100 ng/mL. Moreover, for 30 artificial serum samples with unknown anti-CCP Ab concentrations, the biosensor achieves a correlation coefficient of (R2 = 0.9650). The proposed microfluidic detection platform offers a fast and effective method for accurately identifying and quantifying the anti-CCP Ab biomarker. Thus, it offers a valuable tool for the early diagnosis and monitoring of RA and its progression in point-of-care settings.

A platform for mapping reactive cysteines within the immunopeptidome

The major histocompatibility complex class I antigen presentation pathways play pivotal roles in orchestrating immune responses. Recent studies have begun to explore the therapeutic potential of cysteines within the immunopeptidome, such as the use of covalent ligands to generate haptenated peptide neoepitopes for immunotherapy. In this work, we report a platform for mapping reactive cysteines on MHC-I-bound peptide antigens. We develop cell-impermeable sulfonated maleimide probes capable of capturing reactive cysteines on these antigens. Using these probes in chemoproteomic experiments, we discover that cysteines on MHC-I-bound antigens exhibit various degrees of reactivity. Moreover, interferon-gamma stimulation enhances the reactivity of cysteines at position 8 of 9-mer MHC-I-bound antigens. Finally, we demonstrate that targeting reactive cysteines on MHC-I-bound antigens with a maleimide-conjugated Fc-binding cyclic peptide contributes to the induction of antibody-dependent cellular phagocytosis.

Diastereoselective Anomeric C(sp3)-H Cyclization Towards the Design of New Cyclophane-Braced Glycopeptides.

Here we report a macrocyclization route towards the synthesis of glycophane peptides by a selective C-H arylation of the anomeric bond. This approach demonstrates the power of Pd-catalysis C-H activation to access unusual cyclic peptides.

Diastereoselective Anomeric C(sp3)‐H Cyclization Towards the Design of New Cyclophane‐Braced Glycopeptides

Here we report a macrocyclization route towards the synthesis of glycophane peptides by a selective C‐H arylation of the anomeric bond. This approach demonstrates the power of Pd‐catalysis C‐H activation to access unusual cyclic peptides.

Mirror-Image Random Nonstandard Peptides Integrated Discovery (MI-RaPID) Technology Yields Highly Stable and Selective Macrocyclic Peptide Inhibitors for Matrix Metallopeptidase 7.

Matrix metallopeptidase 7 (MMP7) plays a crucial role in cancer metastasis and progression, making it an attractive target for therapeutic development. However, the development of selective MMP7 inhibitors is challenging due to the conservation of active sites across various matrix metalloproteinases (MMPs). Here, we have developed mirror-image random nonstandard peptides integrated discovery (MI-RaPID) technology to discover innate protease-resistant macrocyclic peptides that specifically bind to and inhibit human MMP7. One identified macrocyclic peptide against D-MMP7, termed D20, was synthesized in its mirror-image form, D'20, consisting of 12 D-amino acids, one cyclic β-amino acid, and a thioether bond. Notably, it potently inhibited MMP7 with an IC50 value of 90 nM, and showed excellent selectivity over other MMPs with similar substrate specificity. Moreover, D'20 inhibited the migration of pancreatic cell line CFPAC-1, but had no effect on the cell proliferation and viability. D'20 exhibited excellent stability in human serum, as well as in simulated gastric and intestinal fluids. This study highlights that MI-RaPID technology can serve as a powerful tool to develop in vivo stable macrocyclic peptides for therapeutic applications.

Mirror‐Image Random Nonstandard Peptides Integrated Discovery (MI‐RaPID) Technology Yields Highly Stable and Selective Macrocyclic Peptide Inhibitors for Matrix Metallopeptidase 7

AbstractMatrix metallopeptidase 7 (MMP7) plays a crucial role in cancer metastasis and progression, making it an attractive target for therapeutic development. However, the development of selective MMP7 inhibitors is challenging due to the conservation of active sites across various matrix metalloproteinases (MMPs). Here, we have developed mirror‐image random nonstandard peptides integrated discovery (MI‐RaPID) technology to discover innate protease‐resistant macrocyclic peptides that specifically bind to and inhibit human MMP7. One identified macrocyclic peptide against D‐MMP7, termed D20, was synthesized in its mirror‐image form, D’20, consisting of 12 D‐amino acids, one cyclic β‐amino acid, and a thioether bond. Notably, it potently inhibited MMP7 with an IC50 value of 90 nM, and showed excellent selectivity over other MMPs with similar substrate specificity. Moreover, D’20 inhibited the migration of pancreatic cell line CFPAC‐1, but had no effect on the cell proliferation and viability. D’20 exhibited excellent stability in human serum, as well as in simulated gastric and intestinal fluids. This study highlights that MI‐RaPID technology can serve as a powerful tool to develop in vivo stable macrocyclic peptides for therapeutic applications.

Electrochemical Determination of B-Type Natriuretic Peptide with an Epitope-Imprinted Polymer-Based Sensor

B-type natriuretic peptides (BNP) are produced and secreted by the myocardium to reduce blood pressure and cardiac load. They cause vasodilation, natriuresis, growth suppression, and inhibition of the sympathetic nervous system and the renin–angiotensin–aldosterone system. The measurement of plasma BNP levels provides clinically useful information concerning the diagnosis and management of left ventricular dysfunction and heart failure, complementing other diagnostic testing procedures. In this work, three epitopes from the N-terminal (BNPnt), C-terminal (BNPct), and the cystine-bridged cyclic peptides (BNPr) of B-type natriuretic peptides were synthesized as templates for molecular imprinting. These peptides were doped into aniline (AN) and m-aminobenzenesulfonic acid (MSAN) for electropolymerization, thus forming epitope-imprinted poly(AN-co-MSAN) conductive films (EIPs). The monomer ratio was optimized using the electrochemical signals during polymerization. The optimized films were then characterized using a scanning electron microscope (SEM), atomic force microscope (AFM), and AC impedance. The electrochemical response of the films to the target peptides and to BNP was then measured. The sensing range of the EIPs-coated electrodes was from 0.001 to 1000 pg/mL for BNP. Finally, the BNP concentration in diluted serum samples was measured with the BNPrIP-coated electrode, giving 3.15 ± 0.07 pg/mL. By spiking the sample with known BNP concentrations, the accuracy was determined to be better than ±5%.

Effect of reduced flaxseed cyclic peptide [1–9-NαC]-linusorb B2 (CLB) and its oxidized form on the oxidative stability of flaxseed oil

This study aimed to explore the antioxidant capacity and mechanism of cyclic peptide [1–9-NαC]-linusorb B2 (CLB) and its oxidized form ([1–9-NαC],[1-MetO]-linusorb B2 (CLC),[1–9-NαC],[1-MetO2]-linusorb B2 (CLK)) in flaxseed oil (FSO). The results showed that CLB delayed the oxidation of FSO (containing Cu2+) in the initial stage of accelerated oxidation, whereas CLK accelerated the oxidation, leading to an increase of 25 % in AV and 33 % in POV (P < 0.05). In molecular docking, the binding ability of cyclic peptides to metal ions and intermediate oxidative products such as aldehydes tends to decrease when CLB oxidized to CLC, then CLK. CLK had the poorest binding capacity with the most serious oxidation on FSO. In conclusion, the antioxidant capacities of CLB and its oxidized form were contributed by their reducing ability as well as their binding ability to metal ions and intermediate oxidative products of fatty acids.

Exploring structure-directed immunogenic cytotoxicity of arginine-rich peptides for cytolysis-induced immunotherapy of cancer

The same cells can die with varied immunological consequences. For the purpose of cancer therapy, stronger immunogenic death of cancer cells is considered favorable. Membrane disruptive peptides are cytotoxic agents with tunable structures capable of not just killing heterogeneous cancer cells, but also inducing immunogenic death. However, the chemo-structural principles that underlie their immunogenic cytotoxicity remain elusive. Here we investigated a series of arginine-rich amphipathic peptides with representative structures on the relationship between the mode of cell death and the immunogenic potency. Among several hydrophobic motif-appended cyclic octaarginine peptides, FC-14 was found to induce cell stress and necroptotic death, unlike apoptotic peptide RL2 and membrane-dissolving peptide RL1. Their differing abilities to release immunogenic death markers correlated well with their potential to activate innate immunity and protective vaccinal effect in a prophylactic model, with FC-14 being the most potent. FC-14 can be pre-opsonized with albumin into nanoparticles (PopAN-FC-14) using PopAN technology to improve its pharmacokinetic properties for intravenous injection. In a syngeneic mouse model of subcutaneous breast cancer, PopAN-FC-14 showed superior therapeutic effect and safety profile than the albumin formulated nanomedicine Nab-paclitaxel (Nab-PTX). Boost injections of PopAN-FC-14 significantly enhanced tumor-specific cellular and humoral immunities, acting similarly as in-situ cancer vaccine. Overall, this work demonstrates a novel focus on the immunogenic cytotoxicity of peptides and a practical approach for effective systemic therapy of cancer.

The occurrence of remitting seronegative symmetrical synovitis with pitting edema (RS3PE) after arthroplasty mimicking a periprosthetic joint infection: A case report and literature review.

As the elderly population grows, the number of joint arthroplasty surgeries is also increasing. Periprosthetic joint infection (PJI) is a postoperative complication that occurs in 1%-2% of the arthroplasties. Once it occurs, PJI is refractory to treatment. Similar symptoms of PJI, including joint synovitis and elevated body temperature, sometimes arise because of crystal arthritis, rheumatoid arthritis, or other inflammatory diseases. Precise diagnosis is essential for determining the optimal treatment strategy. An 81-year-old female patient with a history of bilateral knee arthroplasty presented with a high fever of 38 °C and was unable to walk due to swelling and pain in the bilateral lower extremities. Infectious conditions, such as cellulitis or PJI, were suspected. Imaging findings revealed bilateral knee joint synovitis with pitting edema around the lower extremities, and cultures of bilateral joint fluids were negative. No crystals were observed in the joint fluid. Laboratory data revealed highly elevated levels of inflammatory marker; however, antinuclear antibodies, including rheumatoid factor and cyclic citrullinated peptide, were not detected. Based on bilateral synovitis with pitting edema in the lower extremities, in addition to negative culture findings and normal antinuclear antibodies, the diagnosis of remitting seronegative symmetrical synovitis with pitting edema (RS3PE) was made. Steroid therapy was performed. The dose was gradually reduced, with the improvement of the symptoms. The inflammatory reaction promptly decreased and then normalized. With improved inflammation, the symptoms of pitting edema, pain in the bilateral lower extremities, and fluid effusion of the knee joints were reduced. She was able to walk without a cane, and her activities of daily living fully recovered. High fever and synovitis after joint arthroplasty do not necessarily indicate an infectious condition. Clinicians should be familiar with the occurrence of RS3PE, regardless of whether arthroplasty is performed.

Astragaloside IV Protects Against IL-1β-Induced Chondrocyte Damage via Activating Autophagy.

Osteoarthritis (OA) is a chronic inflammatory condition that affects the articular cartilage. Astragaloside IV (AS-IV) constitutes the primary active component of the Chinese herbal medicine Huangqi (Radix Astragali Mongolici). AS-IV demonstrates anti-inflammatory and anti-apoptotic attributes, exhibiting therapeutic potential across various inflammatory and apoptosis-related disorders. Nevertheless, its pharmaceutical effects in OA are yet to be fully defined. This study aimed to investigate the protective impact of AS-IV on rat chondrocytes treated with IL-1β and ascertain whether autophagy plays a role in this effect. Chondrocytes were isolated and cultivated from the knee joints of neonatal SD mice. The study included the blank control group, the model group, and the AS-IV concentration gradient group (50, 100, 200 μmol/L) to intervene with chondrocytes. The MTT assay was employed to assess cell viability at varying culture periods, enabling the determination of suitable concentration and duration. Subsequently, chondrocytes were treated with the optimal AS-IV concentration and divided into three groups: the model group replicated IL-1β-induced inflammatory chondrocyte injury, the AS-IV group received a co-culture of AS-IV and IL-1β, and a blank control group was established. Changes in cell morphology and structure were observed using ghost pen cyclic peptide staining. ELISA was used to measure TNF-α and GAG levels in cell supernatants. RT-qPCR assessed p62 and LC3 mRNA expression, while Western Blot evaluated p62 and LC3Ⅱ/Ⅰ protein expression. AS-IV promoted chondrocyte proliferation and concurrently inhibited cell apoptosis. An optimal AS-IV dose of 200 μmol/L and a suitable reaction time of 48 h were identified. Ghost pen cyclic peptide staining indicated that the model group's cytoskeleton exhibited fusiform changes with reduced immunofluorescence intensity, as opposed to the blank control group. The AS-IV group displayed more polygonal cytoskeletal morphology with increased immunofluorescence intensity. AS-IV reduced TNF-α levels and elevated GAG levels in the culture supernatant. Additionally, AS-IV lowered p62 mRNA and protein expression while increasing LC3 mRNA expression in cultured chondrocytes. Our findings suggest that AS-IV mitigates inflammatory chondrocyte injury, safeguarding chondrocytes through a potential autophagy suppression mechanism. These results imply that AS-IV could offer preventive advantages for OA.

β-Cyclodextrin Derivatives Bind Aromatic Side Chains of the Cyclic Peptide Lanreotide

Cyclodextrin complexation has a potential to modulate the physicochemical properties of peptide drugs. The ability of peptides to form an inclusion complex can be influenced by factors such as size, amino acid sequence of peptide and the size and charge of the cyclodextrin cavity. In this study, the inclusion complexes of cyclic peptide drug lanreotide acetate with two common β-cyclodextrin derivatives, Sulfobutyl ether β-CD (SBEβ-CD) and hydroxypropyl β-CD (HPβ-CD) were investigated. NMR spectroscopy was used to examine the interaction between β-cyclodextrin derivatives and specific residues of lanreotide. It was observed that the hydrophobic side chain of aromatic residues in the lanreotide sequence can be fit into the cavity of both β-cyclodextrin derivatives. Additionally, NMR revealed a lower diffusion coefficient and higher hydrodynamic radius of complex, indicative of binding to the cavities. Each aromatic residue was individually studied by substituting alanine in lanreotide to measure its association binding with both β-cyclodextrin derivatives. The alanine-substitute study indicated a stronger binding of SBEβ-CD to Lanreotide compared to HPβ-CD. Docking studies suggested that the 1:1 inclusion complex is more favorable than higher order complexes due to the steric hindrance and size considerations. The docking analysis indicated the stable conformation of all three aromatic side chains with both β-cyclodextrin derivatives, SBEβ-CDand HPβ-CD.

Small cyclic dipeptide produced by Lactobacillus rhamnosus with anti-biofilm properties against Streptococcus mutans biofilm

The human oral cavity harbors many bacterial species collectively termed the oral microbiome and is integral for maintaining oral health. Dysbiosis of oral microbiota leads to common oral diseases, including dental caries, gingivitis, and periodontitis. Streptococcus mutans is the primary causative agent of dental caries. Studies have explored the use of probiotic Lactobacillus spp. to mitigate S. mutans biofilms. In the present study, we have tested the use of Lactobacillus rhamnosus extracts/metabolites for anti-biofilm properties. A small organic compound/metabolite was isolated from the cell-free supernatant of L. rhamnosus, and this metabolite resulted in a dose-dependent inhibition of S. mutans biofilms. Confocal microscopy revealed that the thickness of S. mutans biofilms was severely reduced upon metabolite treatment. With the help of FTIR spectra and mass spectrometry analysis, the molecular formula (C11H19O2N2) was deduced. The inhibitor compound was further identified as a small cyclic peptide, cyclo (-L-Leu-L-Pro). Our data also revealed that isolated metabolite impedes S. mutans biofilms by modulating gene expression of several essential genes involved in biofilm establishment.