Peptide Adsorption Research Articles

Dual Role of Anionic Lipids in Amyloid Aggregation.

Neurodegenerative diseases, such as Alzheimer's, Parkinson's, and Huntington's, affect millions worldwide and share a common feature: the aggregation of intrinsically disordered proteins into toxic oligomers that interact with cell membranes. In Alzheimer's disease (AD), amyloid-beta (Aβ) peptides accumulate and bind to plasma membranes, potentially disrupting cellular function. The complex interplay between amyloidogenic peptides and lipid membranes, particularly the role of anionic lipids, is crucial in disease pathogenesis but challenging to characterize experimentally. The literature presents conflicting results on the influence of anionic lipids on peptide aggregation kinetics, highlighting a knowledge gap. To address this, we used coarse-grained molecular dynamics (CG-MD) simulations to study interactions between a model amyloidogenic peptide, amyloid-β's K16LVFFAE22 fragment (Aβ16-22), and mixed lipid bilayers. We used phosphatidylserine (PS) and phosphatidylcholine (PC) as representative anionic and zwitterionic lipids, respectively, examining the mixed bilayer compositions of 0% PS-100% PC, 10% PS-90% PC, and 30% PS-70% PC. Our simulations revealed that membranes enriched in anionic lipids enhance peptide adsorption and interaction kinetics. The aggregation dynamics was modulated by two competing factors: increased local peptide concentration near negatively charged membranes, which promoted aggregation, and peptide-lipid interactions, which slowed it down. Higher percentages of anionic lipids led to smaller and more ordered aggregates and enhanced lipid demixing, leading to the formation of PS clusters. These findings contribute to understanding membrane-mediated peptide aggregation in neurodegenerative disorders, potentially guiding new therapeutic strategies targeting the early stages of protein aggregation in various neurodegenerative diseases.

Air-water interfacial and foaming properties of nanoparticles based on commercial and lab-scale isolated maize (Zea mays L.) zein

Maize zein based nanoparticles (ZNPs) can have applications as food dispersion stabilizers. It has not been documented to what extent the used zein isolation method and conditions thereof impact the structure and functionality of nanoparticles (NPs) based thereupon. Here, zein extracted from maize flour on lab scale (LS-zein) was compared with a commercial zein powder (CS-zein). On a dry matter basis, CS-zein contained 96.5% protein, while LS-zein contained 74.5% protein, 12.7% lipid, 2.9% ash, and a residual fraction, likely starch remnants. SE-HPLC analysis showed that 27.8% of CS-zein protein occurred in an aggregated and insoluble form, while LS-zein mainly contained mono-/dimeric proteins but also approximately 30% hydrophilic peptides. These differences resulted in notably different behavior in the functionality of ZNPs based on CS- and LS-zein (CS-ZNPs and LS-ZNPs, respectively) produced via liquid antisolvent precipitation. CS-ZNPs had poor foaming properties regardless of the pH, in line with their low interfacial dilatational moduli (12.9–15.0 mN/m). The foaming properties of LS-ZNPs were notably better. The high LS-ZNP foam stability (FS) at pH 8.0 and 10.0 was attributed to electrostatic repulsive effects between interfaces of adjacent air bubbles due to the adsorption of peptides and to synergistic protein-lipid interaction effects at the air–water interface. The LS-ZNP FS at pH 4.0 was low despite a high interfacial dilatational modulus (52.6 mN/m). It is hypothesized that intact LS-ZNPs in the liquid thin films between gas bubbles negatively affect FS by a bridging de-wetting effect. Overall, it can be concluded that the (partial) co-isolation of lipids with zein may positively influence foaming properties of NPs based thereupon, while extensive zein purification as applied in industrial zein isolation leads to (partial) zein aggregation and overall low foaming capacity of the obtained CS-ZNPs.

Palmitoylation enhances short polar peptide permeation across stratum corneum lipid bilayer: A molecular dynamics study

Designing chemical molecules that target the skin for non-invasive transdermal drug delivery is of significant interest for both wound healing and skincare applications. These skin-targeting molecules must permeate the outermost protective layer of the skin, the stratum corneum (SC), which consists of dead corneocytes embedded in a lipid matrix, to fulfill their biological functions. Adsorption onto and diffusion through the lipid matrix in the SC represent two key steps for the successful permeation of a skin-targeting molecule across the SC into the underlying skin layers. Here we compare the effects of cyclization and palmitoylation on the adsorption and diffusion of a short polar peptide across a model SC lipid bilayer using molecular dynamics simulations. The cyclized peptide showed slightly better binding to the SC lipid bilayer and similar interaction energies with SC lipids compared to the unmodified peptide. In contrast, the palmitoylated peptide exhibited much stronger interaction with SC lipids via insertion of its attached fatty acid tail into the SC lipid bilayer. The average diffusivity of the cyclized peptide across the SC lipid bilayer was approximately twice that of the unmodified peptide, whereas the palmitoylated peptide’s diffusivity was about 2.7 times higher. Thus, palmitoylation appears to be a promising strategy for enhancing the binding and permeability of short polar peptides across the SC lipid matrix.

Innovation of nano-hydrogels loaded with amelogenin peptide and hydroxyapatite nano-particles for remineralisation of artificially induced white spot lesions

BackgroundWhite spot lesions are a common side effect of fixed orthodontics. This study investigates chitosan-based hydrogels using amelogenin peptide as a scaffold to facilitate hydroxyapatite nanoparticle attachment, assembly, and organisation, aiding in enamel remineralisation. Materials and methodsThree groups were prepared to carry out remineralisation experiments after creating artificial white spot lesions on extracted 1st premolars. The first group served as a control with no treatment, while the experimental groups were treated with either amelogenin peptide/chitosan hydrogel or amelogenin peptide + hydroxyapatite/chitosan hydrogel. Remineralisation was conducted for three weeks. The interaction between amelogenin peptide and hydroxyapatite nanoparticles was evaluated using TEM, UV–Vis, FTIR, zeta potential, and Raman spectroscopy. Remineralisation potential was assessed through enamel microhardness, fluorescence, and XRD. Surface characteristics of demineralised and remineralised enamel were examined by SEM at different magnifications, and chemical compositions were analysed using an EDX analyser. one-way ANOVA and Tukey HSD post hoc multi-comparison tests were performed to find statistical differences between groups. A pairwise comparison was performed to examine if there were significant differences within each group. Significant differences were considered at a P < 0.05. ResultsThe results demonstrated that amelogenin peptide adsorbs onto hydroxyapatite. TEM images revealed the self-assembly of peptide nanoparticles and their adsorption onto hydroxyapatite nanoparticles. UV–Vis spectroscopy, FTIR spectroscopy, Zeta Potential, and Raman Spectroscopy confirmed the binding between amelogenin peptide and hydroxyapatite. The novel hydrogel significantly improved the microhardness and fluorescence values of demineralised enamel. Energy-dispersive X-ray Spectroscopy and X-ray diffractometry revealed the formation of new hydroxyapatite crystals on demineralised enamel, with a calcium-to-phosphorus ratio comparable to natural enamel hydroxyapatite. Structural analysis via SEM showed improved surface texture with the occlusion of demineralised surface porosities. Overall, the hydrogel enhanced hardness, fluorescence, morphology, and chemical composition compared to demineralised enamel. ConclusionsChitosan-based hydrogels provide a promising remineralising strategy that bio-mimics natural enamel regrowth.

Understanding Aβ Peptide Binding to Lipid Membranes: A Biophysical Perspective.

Aβ peptides are known to bind neural plasma membranes in a process leading to the deposit of Aβ-enriched plaques. These extracellular structures are characteristic of Alzheimer's disease, the major cause of late-age dementia. The mechanisms of Aβ plaque formation and deposition are far from being understood. A vast number of studies in the literature describe the efforts to analyze those mechanisms using a variety of tools. The present review focuses on biophysical studies mostly carried out with model membranes or with computational tools. This review starts by describing basic physical aspects of lipid phases and commonly used model membranes (monolayers and bilayers). This is followed by a discussion of the biophysical techniques applied to these systems, mainly but not exclusively Langmuir monolayers, isothermal calorimetry, density-gradient ultracentrifugation, and molecular dynamics. The Methodological Section is followed by the core of the review, which includes a summary of important results obtained with each technique. The last section is devoted to an overall reflection and an effort to understand Aβ-bilayer binding. Concepts such as Aβ peptide membrane binding, adsorption, and insertion are defined and differentiated. The roles of membrane lipid order, nanodomain formation, and electrostatic forces in Aβ-membrane interaction are separately identified and discussed.

Insights into the mechanism of peptide fibril growth on gold surface

Understanding the formation of β-fibrils over the gold surface is of paramount interest in nano-bio-medicinal Chemistry. The intricate mechanism of self-assembly of neurofibrillogenic peptides and their growth over the gold surface remains elusive, as experiments are limited in unveiling the microscopic dynamic details, in particular, at the early stage of the peptide aggregation. In this work, we carried out equilibrium molecular dynamics and enhanced sampling simulations to elucidate the underlying mechanism of the growth of an amyloid-forming sequence of tau fragments over the gold surface. Our results disclose that the collective intermolecular interactions between the peptide chains and peptides with the gold surface facilitate the peptide adsorption, followed by integration, finally leading to the fibril formation.

Comparison of the adsorption of linear and cyclic antimicrobial peptides onto cellulosic compounds-reinforced poly(vinyl alcohol) films using QCM-D

Understanding peptide adsorption kinetics onto biomaterial surfaces is crucial for developing wound treatments. This study aims to explore the influence of cellulose acetate (CA) and cellulose nanocrystals (CNC) on peptide adsorption via quartz crystal microbalance with dissipation monitoring (QCM-D), using a cyclic peptide, Tiger 17, and a linear, Pexiganan. PVA was reinforced with 10 and 20% w/v of CA and CNC, spin-coated onto QCM-D sensors, and crosslinked with glutaraldehyde. Films containing higher percentages of cellulosic compounds promoted the highest peptide adsorption, with CNC-containing films being the most effective. While C80/20 PVA/CNC films achieved adsorption masses of ≈199 and ≈150 ng/cm2 for Tiger 17 and Pexiganan, respectively, the C80/20 PVA/CA films attained ≈168 and ≈122 ng/cm2. The peptides’ structure also influenced adsorption, with Tiger 17 reaching greater frequency drops (ΔF) than Pexiganan. Sequential adsorption studies corroborated these findings. Even though the tendency was for PVA/CNC to promote the highest peptide binding, it was the PVA/CA films that reached the greatest peptide loading amount with the sequence Pexiganan + Tiger 17. Data are encouraging for developing new wound therapies reinforced with cellulosic compounds and modified with Tiger 17 and Pexiganan.

Confinement and Polarity Effects on the Peptide Packing Density on Mesoporous Silica Nanoparticles.

The adsorption of cationic peptide JM21 onto different mesoporous silica nanoparticles (MSNs) from an aqueous solution was studied as a function of pH. In agreement with the literature, the highest loading degrees could be achieved at pH close to the isoelectric point of the peptide where the peptide-peptide repulsion is minimum. However, mesopore size, mesopore geometry, and surface polarity all had an influence on the peptide adsorption in terms of both affinity and maximum loading at a given pH. This adsorption behavior could largely be explained by a combination of pH-dependent electrostatic interactions and confinement effects. It is demonstrated that hydrophobic interactions enhance the degree of peptide adsorption under pH conditions where the electrostatic attraction was absent in the case of mesoporous organosilica nanoparticles (MONs). The lower surface concentration of silanol groups for MON led to a lower level of peptide adsorption under optimum pH conditions compared to all-silica particles. Finally, the study confirmed the protective role of MSNs in preserving the biological activity of JM#21 against enzymatic degradation, even for large-pore MSNs, emphasizing their potential as nanocarriers for therapeutic peptides. By integrating experimental findings with theoretical modeling, this research elucidates the complex interplay of factors that influence peptide-silica interactions, providing vital insights for optimizing peptide loading and stabilization in biomedical applications.

Insights into the Adsorption Mechanisms of the Antimicrobial Peptide CIDEM-501 on Membrane Models.

CIDEM-501 is a hybrid antimicrobial peptide rationally designed based on the structure of panusin and panulirin template peptides. The new peptide exhibits significant antibacterial activity against multidrug-resistant pathogens (MIC = 2-4 μM) while conserving no toxicity in human cell lines. We conducted molecular dynamics (MD) simulations using the CHARMM-36 force field to explore the CIDEM-501 adsorption mechanism with different membrane compositions. Several parameters that characterize these interactions were analyzed to elucidate individual residues' structural and thermodynamic contributions. The membrane models were constructed using CHARMM-GUI, mimicking the bacterial and eukaryotic phospholipid compositions. Molecular dynamics simulations were conducted over 500 ns, showing rapid and highly stable peptide adsorption to bacterial lipids components rather than the zwitterionic eucaryotic model membrane. A predominant peptide orientation was observed in all models dominated by an electric dipole. The peptide remained parallel to the membrane surface with the center loop oriented to the lipids. Our findings shed light on the antibacterial activity of CIDEM-501 on bacterial membranes and yield insights valuable for designing potent antimicrobial peptides targeting multi- and extreme drug-resistant bacteria.

Engineering poly(dehydroalanine)-based gels via droplet-based microfluidics: from bulk to microspheres.

Biomedical applications such as drug delivery, tissue engineering, and functional surface coating rely on switchable adsorption and desorption of specialized guest molecules. Poly(dehydroalanine), a polyzwitterion containing pH-dependent positive and negative charges, shows promise for such reversible loading, especially when integrated into a gel network. Herein, we present the fabrication of poly(dehydroalanine)-derived gels of different size scales and evaluate them with respect to their practical use in biomedicine. Already existing protocols for bulk gelation were remodeled to derive suitable reaction conditions for droplet-based microfluidic synthesis. Depending on the layout of the microfluidic chip, microgels with a size of approximately 30 μm or 200 μm were obtained, whose crosslinking density can be increased by implementing a multi-arm crosslinker. We analyzed the effects of the crosslinker species on composition, permeability, and softness and show that the microgels exhibit advantageous properties inherent to zwitterionic polymer systems, including high hydrophilicity as well as pH- and ionic strength-sensitivity. We demonstrate pH-regulated uptake and release of fluorescent model dyes before testing the adsorption of a small antimicrobial peptide, LL-37. Quantification of the peptide accommodated within the microgels reveals the impact of size and crosslinking density of the microgels. Biocompatibility of the microgels was validated by cell tests.

Electrochemical Biosensors Composed of Polyethylenimine (PEI) and Graphene Derivatives for Rapid Detection of Alzheimer’s Disease

Graphene materials can be used as nanofillers in polymers to take advantage of graphene's suitable properties. Graphene-PEI composites are materials that combine the unique properties of graphene and PEI. These composites are made by combining graphene with PEI through physical or chemical method. The resulting material is characterized by enhanced mechanical properties, improved electrical conductivity and increased stability. By incorporating graphene into biosensor platforms, it can improve overall’s performance, including sensitivity, specificity and response. In this work, the detection of anti-βA40 biomarker was tested. Beta-amyloid peptide (βA1-40) was incorporated into liposomes of Dipalmitoyl Phosphatidylglycerol (DPPG) and was immobilized using Layer-by-Layer self-assembling technique on PEI_graphene derivatives composites. To obtain these composites it was utilized graphene oxide (GO) from Hummers’ method, it’s thermally reduced form (rGO) and also electrochemically exfoliated graphene (EEG). MilliQ water was added to the PEI to obtain a concentration of 2mg/mL and stirred for 30 min at room temperature for complete dissolution of the PEI. Then EEG, GO and rGO were added to PEI solution and subjected to ultrasonication in a Hielscher UP400ST sonicator, using the H14 probe for 30 minutes to obtain a homogeneous and stable dispersion.Carbon microelectrodes modified with PEI-graphene derivatives composites and (DPPG +Aβ-40) were used as biosensors platforms to detect anti-Aβ40 related to Alzheimer's disease. The assembly of the biosensors is shown in Figure 1. Cyclic Voltammetry was performed in three cycles, at a potential of -0.6 V to 0.6 V and scan rate of 0.05 V s-1 to evaluate the sensory response. The electrochemical measurements were performed with saline phosphate buffer solution (PBS). The morphology of PEI and PEI_graphene oxide can be seen in Figure 2. The large surface area of graphene allows for increased binding sites for bioreceptors, which may favor the adsorption of Aβ-40 peptide, improving signal transduction and sensitivity of the biosensor. The wettability of the composites was obtained through measurements of the static contact angle using the Ramé-Hart Contact Angle Goniometer (model 100-25-A). Figure 3 presents the contact angle for a film layer of the composites. All PEI_graphene derivative composites showed hydrophilic behavior (θ < 90°), PEI_EEG composite stood out as less hydrophilic (θ = 68°) among all composites. Hydrophilicity is essential in biosensors because it affects the interactions between the biological recognition elements and the target analytes, as well as the overall stability and reliability of the biosensor. Figure 4 presents the calibration curves using the normalized area obtained from cyclic voltammetry of the biosensors manufactured with 2 bilayers (PEI_graphene derivative/DPPG+Aβ40) and anti-Aβ40 biomarker in concentrations ranging from 1 ng mL to 5 µg mL-1. Among the tested PEI_graphene derivatives composites, the ones with EEG and RGO stood out in relation to pure PEI. Table 1 presents the adjusted R-square of the data in Figure 4. All composites, except PEI_GO, showed excellent linear fit, adjusted R-square close to 1 in the detection range between 1 and 1000 ng mL-1. The PEI_graphene oxide composite can be used in biosensors to enable rapid and efficient transduction of the binding signal, leading to improved detection performance. Figure 1

Norbornene-chitosan spray-dried microspheres for peptide conjugation using thiol-ene “photoclick” chemistry

The action of bioactive peptides, such as antimicrobial peptides (AMP), in the human body is often compromised by limited residence time and stability in the target site. Bioconjugation of peptides to biomaterial surfaces is one of the strategies that may overcome these limitations. Herein, norbornene-chitosan (NorChit) microspheres were engineered to react with thiolated peptides by thiol-ene “photoclick” chemistry. NorChit microspheres were produced by spray drying and crosslinked with dithiothreitol (DTT) to prevent their solubilization. Microspheres with a diameter of 5 ± 2 µm showed round and smooth morphology with pockets over the surface that could be related with hydrophobic interactions between internal norbornene groups. Thiol-ene bioconjugation carried out using a fluorescent model peptide, showed a yield of 45%, whereas using the peptide but without UV exposure indicated a maximum of peptide adsorption of 30%. Altogether, NorChit microspheres show the potential for carrying bioactive peptides, which may open avenues for AMP activity onto harsh environments in the body. The action of bioactive peptides, such as antimicrobial peptides (AMP), in the human body is often compromised by limited residence time and stability in the target site. Bioconjugation of peptides to biomaterial surfaces is one of the strategies that may overcome these limitations. Herein, norbornene-chitosan (NorChit) microspheres were engineered to react with thiolated peptides by thiol-ene “photoclick” chemistry. NorChit microspheres were produced by spray drying and crosslinked with dithiothreitol (DTT) to prevent their solubilization. Microspheres with a diameter of 5 ± 2 μm showed round and smooth morphology with pockets over the surface that could be related with hydrophobic interactions between internal norbornene groups. Thiol-ene bioconjugation carried out using a fluorescent model peptide, showed a yield of 45%, whereas using the peptide but without UV exposure indicated a maximum of peptide adsorption of 30%. Altogether, NorChit microspheres show the potential for carrying bioactive peptides, which may open avenues for AMP activity onto harsh environments in the body.

Molecular Adhesion of a Pilus-Derived Peptide Involved in Pseudomonas aeruginosa Biofilm Formation on Non-Polar ZnO-Surfaces.

Bacterial colonization and biofilm formation on abiotic surfaces are initiated by the adhesion of peptides and proteins. Understanding the adhesion of such peptides and proteins at a molecular level thus represents an important step toward controlling and suppressing biofilm formation on technological and medical materials. This study investigates the molecular adhesion of a pilus-derived peptide that facilitates biofilm formation of Pseudomonas aeruginosa, a multidrug-resistant opportunistic pathogen frequently encountered in healthcare settings. Single-molecule force spectroscopy (SMFS) was performed on chemically etched ZnO surfaces to gather insights about peptide adsorption force and its kinetics. Metal-free click chemistry for the fabrication of peptide-terminated SMFS cantilevers was performed on amine-terminated gold cantilevers and verified by X-ray photoelectron spectroscopy (XPS) and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). Atomic force microscopy (AFM) and XPS analyses reveal stable topographies and surface chemistries of the substrates that are not affected by SMFS. Rupture events described by the worm-like chain model (WLC) up to 600 pN were detected for the non-polar ZnO surfaces. The dissociation barrier energy at zero force ΔG(0), the transition state distance xb and bound-unbound dissociation rate at zero force koff (0) for the single crystalline substrate indicate that coordination and hydrogen bonds dominate the peptide/surface interaction.

The molecular dynamics simulation of peptide-based structure adsorption inside nanochannel with surface roughness

Peptides result from partial hydrolysis of protein polypeptide chains. These atomic structures are the main section of various protein compounds. So, the adsorption process of these structures can be used in various medical applications. The small peptide structure is absorbed using a platinum nanochannel with cubic roughness in an aqueous environment in the present computational examination. Technically, the simulation of the nanochannel- peptide system is done using the Molecular Dynamics (MD) method. The different atoms' interactions in our systems are defined by DREIDING/Universal Force-Field (UFF), TIP3P, and Embedded Atom Model (EAM). Temperature, total energy (TE), Radial Distribution Function (RDF), profiles of density/velocity/temperature, absorption ratio, interaction energy, and volume were presented for t = 30 ns in order to provide a physical description of the peptide adsorption process. Our simulation results show the atomic stability of P-nanochannel system in the attendance of H2O molecules. Moreover, peptide absorption ratio inside the MD box reached a 78 % value. This result shows the appropriate behavior of a metallic nanochannel with rectangular roughness to adsorption of various protein-based structures, such as Ps for medical aims.

Electrospun starch-based nanofiber mats for odor adsorption of oyster peptides: Recyclability and structural characterization

The off-odor of seafood, which negatively affected its flavor and quality, was removed mainly by non-recyclable liquid-phase deodorization methods at present. In this work, octenylsuccinylated starch (OSS)-pullulan (PUL) nanofiber mats were regenerated after physical adsorption and thermal desorption of off-odor compounds in oyster peptides. The mat structure was characterized and the adsorption process was investigated. The regenerated nanofiber mats maintained a favorable appearance and microscopic morphology even after 25 adsorption-desorption cycles, with a reduction in average fiber diameter and average pore area, an increase in hydrophobicity and alterations in surface groups. Their adsorption rate first decreased and then stabilized as the number of cycles increased and was as high as 81.76% after 25 cycles. Correlation analysis revealed that the adsorption efficiency of regenerated nanofiber mats was related to their microstructure, surface groups and hydrophobicity. These findings could provide a theoretical basis for odor removal by electrospun nanofiber mats and their recycling.

Nature-inspired material binding peptides with versatile polyester affinities and binding strengths

Biodegradable polyesters, such as polyhydroxyalkanoates (PHAs), are having a tremendous impact on biomedicine. However, these polymers lack functional moieties to impart functions like targeted delivery of molecules. Inspired by native GAPs, such as phasins and their polymer-binding and surfactant properties, we generated small material binding peptides (MBPs) for polyester surface functionalization using a rational approach based on amphiphilicity. Here, two peptides of 48 amino acids derived from phasins PhaF and PhaI from Pseudomonas putida, MinP and the novel-designed MinI, were assessed for their binding towards two types of PHAs, PHB and PHOH. In vivo, fluorescence studies revealed selective binding towards PHOH, whilst in vitro binding experiments using the Langmuir-Blodgett technique coupled to ellipsometry showed KD in the range of nM for all polymers and MBPs. Marked morphological changes of the polymer surface upon peptide adsorption were shown by BAM and AFM for PHOH. Moreover, both MBPs were successfully used to immobilize cargo proteins on the polymer surfaces. Altogether, this work shows that by redesigning the amphiphilicity of phasins, a high affinity but lower specificity to polyesters can be achieved in vitro. Furthermore, the MBPs demonstrated binding to PET, showing potential to bind cargo molecules also to synthetic polyesters.

Highly selective and pH responsive adsorption of ZIF-8 for angiotensin-converting enzyme (ACE) inhibitory active peptides and its mechanism

Searching adsorbents for high recognition and adsorption capacities of active peptides has become the hotspot of scientific research in the screening and purification of peptides. In this work, we selected MOFs materials with good biocompatibility to systematically investigated for the selective adsorption of highly active ACE inhibitory peptides. Herein, five typical kinds of metal organic frameworks (MOFs) were initially screened for their adsorption capacities towards di-peptide (CW) having ultra-high angiotensin-converting enzyme (ACE) inhibitory activity (IC50 = 0.16 μM). The effects of their pore sizes and surface potentials on CW adsorption capacity were explored in this work. Among these MOFs, ZIF-8 was chosen as a di-peptide adsorbent due to its excellent adsorption capacity of CW (0.382 mmol/g). Besides, the adsorption behavior of ZIF-8 for di-peptides in the mixed solution was systematically explored. Experimental results indicated that ZIF-8 exhibited highly specific adsorption towards CW while showing very low and almost non-adsorption for the two inactive peptides, DD and RR. In their ternary peptide solution (molar ratio: CW/DD/RR = 1/10/10) for simulated protein hydrolysate, ZIF-8 displayed ultra-high adsorption selectivity (α = 46.6) for CW and thus enhanced almost 70.9 times the ACE inhibitory activity for the enriched solution. Meanwhile, molecular simulation revealed that ZIF-8 had high recognition towards CW, which was primarily attributed to synergistic mechanisms of electrostatic attraction, NH/SH···π interaction, and pore size screening of ZIF-8 towards CW. Interestingly, ZIF-8 was discovered for the first time to have a distinct pH-responsive property towards CW enrichment. Based on this property, pH-responsive adsorption was carried out with desorption over ZIF-8, and a stable regeneration process for 5 continuous adsorption/desorption cycles was accomplished. Collectively, this work proved that MOFs have promising application prospects in the field of peptide adsorption.

Effect of phospholipid liposomes on prion fragment (106–128) amyloid formation

Misfolding and aggregation of cellular prion protein (PrPc) is a major molecular process involved in the pathogenesis of prion diseases. Here, we studied the aggregation properties of a prion fragment peptide PrP(106–128). The results show that the peptide aggregates in a concentration-dependent manner in an aqueous solution and that the aggregation is sensitive to pH and the preformed amyloid seeds. Furthermore, we show that the zwitterionic POPC liposomes moderately inhibit the aggregation of PrP(106–128), whereas POPC/cholesterol (8:2) vesicles facilitate peptide aggregation likely due to the increase of the lipid packing order and membrane rigidity in the presence of cholesterol. In addition, anionic lipid vesicles of POPG and POPG/cholesterol above a certain concentration accelerate the aggregation of the peptide remarkably. The strong electrostatic interactions between the N-terminal region of the peptide and POPG may constrain the conformational plasticity of the peptide, preventing insertion of the peptide into the inner side of the membrane and thus promoting fibrillation on the membrane surface. The results suggest that the charge properties of the membrane, the composition of the liposomes, and the rigidity of lipid packing are critical in determining peptide adsorption on the membrane surface and the efficiency of the membrane in catalyzing peptide oligomeric nucleation and amyloid formation. The peptide could be used as an improved model molecule to investigate the mechanistic role of the crucial regions of PrP in aggregation in a membrane-rich environment and to screen effective inhibitors to block key interactions between these regions and membranes for preventing PrP aggregation.

SARS-CoV-2 inhibitory activity of a short peptide derived from internal fusion peptide of S2 subunit of spike glycoprotein

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has posed a great concern in human population. To fight coronavirus emergence, we have dissected the conserved amino acid region of the internal fusion peptide in the S2 subunit of Spike glycoprotein of SARS-CoV-2 to design new inhibitory peptides. Among the 11 overlapping peptides (9-23-mer), PN19, a 19-mer peptide, exhibited a powerful inhibitory activity against different SARS-CoV-2 clinical isolate variants in absence of cytotoxicity. The PN19 inhibitory activity was found to be dependent on conservation of the central Phe and C-terminal Tyr residues in the peptide sequence. Circular dichroism spectra of the active peptide exhibited an alpha-helix propensity, confirmed by secondary structure prediction analysis. The PN19 inhibitory activity, exerted in the first step of virus infection, was reduced after peptide adsorption treatment with virus-cell substrate during fusion interaction. Additionally, PN19 inhibitory activity was reduced by adding S2 membrane-proximal region derived peptides. PN19 showed binding ability to the S2 membrane proximal region derived peptides, confirmed by molecular modelling, playing a role in the mechanism of action. Collectively, these results confirm that the internal fusion peptide region is a good candidate on which develop peptidomimetic anti SARS-CoV-2 antivirals.

Influence of amino acid and N-terminal protection residue structures on peptide p-nitroanilide adsorption on polystyrene-based support.

Polystyrene-based support Bio-Beads® SM-2 was employed for desalting peptide-p-nitroanilides from Oxone®. Neither tosyl, 9-fluorenyl(methoxycarbonyl), p-nitroanilide groups nor indolyl or p-hydroxyphenyl side-chains of Trp and Tyr ensured an efficient adsorption of peptide-p-nitroanilides onto Bio-Beads® SM-2. Only unsubstituted phenyl-containing protection groups (carbobenzoxy or benzoyl) and Phe residues provided the adsorption of peptides on Bio-Beads® SM-2 and their efficient desalting. This support is well suitable for multiple parallel phenyl group-containing peptide derivative separations and high-throughput screenings.