Octenylsuccinylation strategy to construct high-amylose maize starch-myristic acid complexes with high thermal stability, complexation efficiency and anti-retrogradation ability.

Gelatinizing high-amylose maize starch (HAMSt) requires high temperatures to allow complexation with lipids, making it a challenging process. An octenylsuccinylation method was examined as a part of a strategy to decrease the gelatinization temperature of HAMSt, thereby promoting the complexation between HAMSt and myristic acid (MAc). Octenyl succinic anhydride (OSA) modification of HAMSt reduces the onset gelatinization temperature of HAMSt from 71.63 °C to 66.97 °C. Moreover, as the OSA concentration increased from 2 % to 11 %, the degree of substitution and molecular weights of the esterified HAMSt gradually increased from 0.0069 to 0.0184 and from 0.97 × 106 to 1.17 × 106 g/mol, respectively. Fourier transform infrared analysis indicated that the octenyl-succinate groups were grafted onto the HAMSt chains. The formation of HAMSt-MAc complexes improved the thermal stability of OSA-treated HAMSt (peak temperature increased by 0.11 °C-13.95 °C). Moreover, the diffraction intensity of the V-type peak of the 11 % sample was greater than that of other samples. Finally, the anti-retrogradation ability was in the order of OSA-HAMSt-MAc complexes > HAMSt-MAc complexes > HAMSt. Overall, our results indicate that octenylsuccinylation can be an effective strategy to promote the formation of OSA-HAMSt-MAc complexes and delay starch retrogradation.

Citrus oil gland and cuticular wax inspired multifunctional gelatin film of OSA-starch nanoparticles-based nanoemulsions for preserving perishable fruit.

Inspired by the citrus oil gland and cuticular wax, a multifunctional material that stably and continuously released the carvacrol and provided physical defenses was developed to address issues of fresh-cut fruits to microbial infestation and moisture loss. The results confirmed that low molecular weight and loose structure of starch nanoparticles prepared by the ultrasound-assisted Fenton system were preferable for octenyl succinic anhydride modification compared to native starch, achieving a higher degree of substitution (increased by 18.59 %), utilizing in preparing nanoemulsions (NEs) for encapsulating carvacrol (at 5 % level: 81.58 %). Furthermore, the NEs-based gelatin (G) film improved with surface hydrophobic modification by myristic acid (MA) successfully replicated the citrus oil gland and cuticular wax, providing superior antioxidant (enhanced by 3-4 times) and antimicrobial properties (95.99 % and 84.97 % against Staphylococcus aureus and Escherichia coli respectively), as well as the exceptional UV shielding (nearly 0 transmittance in the UV region), mechanical (72 % increase in tensile strength), and hydrophobic (WCA 133.63°). Moreover, the 5%NE-G@MA film inhibited foodborne microbial growth (reduced by 50 %) and water loss (controlled below 15 %), extending the shelf life of fresh-cut navel orange and kiwi. Thus, the multifunctional film was a potential shield for preserving perishable fresh-cut products.

Structural and mechanistic insights into the transport of aristolochic acids and their active metabolites by human serum albumin.

Aristolochic acids I and II (AA-I/II) are carcinogenic principles of Aristolochia plants, which have been employed in traditional medicinal practices and discovered as food contaminants. While the deleterious effects of AAs are broadly acknowledged, there is a dearth of information to define the mechanisms underlying their carcinogenicity. Following bioactivation in the liver, N-hydroxyaristolactam and N-sulfonyloxyaristolactam metabolites are transported via circulation and elicit carcinogenic effects by reacting with cellular DNA. In this study, we apply DNA adduct analysis, X-ray crystallography, isothermal titration calorimetry, and fluorescence quenching to investigate the role of human serum albumin (HSA) in modulating AA carcinogenicity. We find that HSA extends the half-life and reactivity of N-sulfonyloxyaristolactam-I with DNA, thereby protecting activated AAs from heterolysis. Applying novel pooled plasma HSA crystallization methods, we report high-resolution structures of myristic acid-enriched HSA (HSAMYR) and its AA complexes (HSAMYR/AA-I and HSAMYR/AA-II) at 1.9 Å resolution. While AA-I is located within HSA subdomain IB, AA-II occupies subdomains IIA and IB. ITC binding profiles reveal two distinct AA sites in both complexes with association constants of 1.5 and 0.5 · 106 M-1 for HSA/AA-I versus 8.4 and 9.0 · 105 M-1 for HSA/AA-II. Fluorescence quenching of the HSA Trp214 suggests variable impacts of fatty acids on ligand binding affinities. Collectively, our structural and thermodynamic characterizations yield significant insights into AA binding, transport, toxicity, and potential allostery, critical determinants for elucidating the mechanistic roles of HSA in modulating AA carcinogenicity.

Global analysis of N-myristoylation and its heterogeneity by combining N-terminomics and nanographite fluoride-based solid-phase extraction.

N-myristoylation is one of the most widespread and important lipidation in eukaryotes and some prokaryotes, which is formed by covalently attaching various fatty acids (predominantly myristic acid C14:0) to the N-terminal glycine of proteins. Disorder of N-myristoylation is critically implicated in numerous physiological and pathological processes. Here, we presented a method for purification and comprehensive characterization of endogenous, intact N-glycine lipid-acylated peptides, which combined the negative selection method for N-terminome and the nanographite fluoride-based solid-phase extraction method (NeS-nGF SPE). After optimizing experimental conditions, we conducted the first global profiling of the endogenous and heterogeneous modification states for N-terminal glycine, pinpointing the precise sites and their associated lipid moieties. Totally, we obtained 76 N-glycine lipid-acylated peptides, including 51 peptides with myristate (C14:0), 10 with myristoleate (C14:1), 6 with tetradecadienoicate (C14:2), 5 with laurate (C12:0) and 4 with lauroleate (C12:1). Therefore, our proteomic methodology could significantly facilitate precise and in-depth analysis of the endogenous N-myristoylome and its heterogeneity.

Application of Liquid-Liquid Extraction for N-terminal Myristoylation Proteomics.

Proteins can be modified by lipids in various ways, for example, by myristoylation, palmitoylation, farnesylation, and geranylgeranylation-these processes are collectively referred to as lipidation. Current chemical proteomics using alkyne lipids has enabled the identification of lipidated protein candidates but does not identify endogenous lipidation sites and is not readily applicable to in vivo systems. Here, we introduce a proteomic methodology for global analysis of endogenous protein N-terminal myristoylation sites that combines liquid-liquid extraction of hydrophobic lipidated peptides with liquid chromatography-tandem mass spectrometry using a gradient program of acetonitrile in the high concentration range. We applied this method to explore myristoylation sites in HeLa cells and identified a total of 75 protein N-terminal myristoylation sites, which is more than the number of high-confidence myristoylated proteins identified by myristic acid analog-based chemical proteomics. Isolation of myristoylated peptides from HeLa digests prepared with different proteases enabled the identification of different myristoylated sites, extending the coverage of N-myristoylome. Finally, we analyzed in vivo myristoylation sites in mouse tissues and found that the lipidation profile is tissue-specific. This simple method (not requiring chemical labeling or affinity purification) should be a promising tool for global profiling of protein N-terminal myristoylation.

Small-angle x-ray scattering investigation of the integration of free fatty acids in polysorbate 20 micelles.

A critical quality attribute for liquid formulations is the absence of visible particles. Such particles may form upon polysorbate hydrolysis resulting in release of free fatty acids into solution followed by precipitation. Strategies to avoid this effect are of major interest for the pharmaceutical industry. In this context, we investigated the structural organization of polysorbate micelles alone and upon addition of the fatty acid myristic acid (MA) by small-angle x-ray scattering. Two complementary approaches using a model of polydisperse core-shell ellipsoidal micelles and an ensemble of quasiatomistic micelle structures gave consistent results well describing the experimental data. The small-angle x-ray scattering data reveal polydisperse mixtures of ellipsoidal micelles containing about 22-35 molecules per micelle. The addition of MA at concentrations up to 100 µg/mL reveals only marginal effects on the scattering data. At the same time, addition of high amounts of MA (>500 µg/mL) increases the average sizes of the micelles indicating that MA penetrates into the surfactant micelles. These results together with molecular modeling shed light on the polysorbate contribution to fatty acid solubilization preventing or delaying fatty acid particle formation.

Structural and Large-scale Analysis Unveil the Intertwined Paths Promoting NMT-catalyzed Lysine and Glycine Myristoylation.

N-myristoyltransferases (NMTs) catalyze protein myristoylation, a lipid modification crucial for cell survival and a range of pathophysiological processes. Originally thought to modify only N-terminal glycine α-amino groups (G-myristoylation), NMTs were recently shown to also modify lysine ε-amino groups (K-myristoylation). However, the clues ruling NMT-dependent K-myristoylation and the full range of targets are currently unknown. Here we combine mass spectrometry, kinetic studies, in silico analysis, and crystallography to identify the specific features driving each modification. We show that direct interactions between the substrate's reactive amino group and the NMT catalytic base promote K-myristoylation but with poor efficiency compared to G-myristoylation, which instead uses a water-mediated interaction. We provide evidence of depletion of proteins with NMT-dependent K-myristoylation motifs in humans, suggesting evolutionary pressure to prevent this modification in favor of G-myristoylation. In turn, we reveal that K-myristoylation may only result from post-translational events. Our studies finally unravel the respective paths towards K-myristoylation or G-myristoylation, which rely on a very subtle tradeoff embracing the chemical landscape around the reactive group.

A metabolic labeling protocol to enrich myristoylated proteins from Caenorhabditis elegans.

Myristoylation is a type of lipidation with important functions. Owing to the lack of high-quality antibodies against myristoylation, developing alternative methods for profiling myristoylated proteins is important. Here, we provide a protocol for metabolic labeling using click chemistry to profile myristoylated proteins in C. elegans. Our approach improves the signal/noise ratio by covalently linking the myristoylated proteins to the beads. This protocol provides a highly specific and reproducible way for enriching myristoylated proteins, which could be modified to analyze other types of lipidations. For complete details on the use and execution of this protocol, please refer to Tang et al. (2021).

Protein N-myristoylation: functions and mechanisms in control of innate immunity.

Protein N-myristoylation is an important fatty acylation catalyzed by N-myristoyltransferases (NMTs), which are ubiquitous enzymes in eukaryotes. Specifically, attachment of a myristoyl group is vital for proteins participating in various biological functions, including signal transduction, cellular localization, and oncogenesis. Recent studies have revealed unexpected mechanisms indicating that protein N-myristoylation is involved in host defense against microbial and viral infections. In this review, we describe the current understanding of protein N-myristoylation (mainly focusing on myristoyl switches) and summarize its crucial roles in regulating innate immune responses, including TLR4-dependent inflammatory responses and demyristoylation-induced innate immunosuppression during Shigella flexneri infection. Furthermore, we examine the role of myristoylation in viral assembly, intracellular host interactions, and viral spread during human immunodeficiency virus-1 (HIV-1) infection. Deeper insight into the relationship between protein N-myristoylation and innate immunity might enable us to clarify the pathogenesis of certain infectious diseases and better harness protein N-myristoylation for new therapeutics.

Erythorbyl fatty acid ester as a multi-functional food emulsifier: Enzymatic synthesis, chemical identification, and functional characterization of erythorbyl myristate.

Erythorbyl myristate (EM), a potential multi-functional food emulsifier, was newly synthesized by immobilized lipase-catalyzed esterification between antioxidative erythorbic acid and antibacterial myristic acid. The yield and productivity of EM were 56.13 ± 2.51 mg EM/g myristic acid and 1.76 ± 0.08 mM/h, respectively. The molecular structure of EM was identified as (R)-2-((R)-3,4-dihydroxy-5-oxo-2,5-dihydrofuran-2-yl)-2-hydroxyethyl tetradecanoate using HPLC-ESI/MS and 2D [1H-1H] NMR COSY. The hydrophilic-lipophilic balance of EM was 11.5, suggesting that EM could be proper to stabilize oil-in-water emulsions. Moreover, isothermal titration calorimetry demonstrated the micellar thermodynamic behavior of EM and determined its critical micelle concentration (0.36 mM). In terms of antioxidative property, EM exhibited the radical scavenging activity against DPPH (EC50: 35.47 ± 0.13 µM) and ABTS (EC50: 36.45 ± 1.98 µM) radicals. Finally, EM showed bacteriostatic and bactericidal activities against Gram-positive foodborne pathogens (minimum inhibitory concentration: 0.06-0.60 mM; minimum bactericidal concentration: 0.07-0.93 mM).

Power function setting in charged aerosol detection for the linearization of detector response - optimization strategies and their application.

Charged aerosol detection (CAD) is an universal technique in liquid chromatography that is increasingly used for the quality control of drugs. Consequently, it has found its way into compendial monographs promoted by its simple and robust application. However, the response of CAD is inherently nonlinear due to its principle of function. Thus, easy and rapid linearization procedures, in particular regarding compendial applications, are highly desirable. One effective approach to linearize the detector's signal makes use of the built-in power function value (PFV) setting of the instrument. The PFV is basically a multiplication factor to the power law exponent of the equation describing the CAD's response, thereby altering the detector's signal output to optimize the quasi-linear range of the response curve. The experimental optimization of the PFV for a series of analytes is a time-consuming process, limiting the practicability of this approach. Here, two independent approaches for the determination of the optimal PFV based on an empirical model and a mathematical transformation in each case, are evaluated. Both approaches can be utilized to predict the optimal PFV for each analyte solely based on the experimental results of a series of calibration standards obtained at a single PFV. The approaches were applied to the HPLC-UV-CAD impurity analysis of the drug gabapentin to improve the observed nonlinear response of the impurities in the range of interest. The predicted optimal PFV of both approaches were in good agreement with the experimentally obtained optimal PFV of the analytes. As a result, the accuracy of the method was significantly improved when using the optimal PFV (90 - 105% versus 81 - 115% recovery rate for quantitation by either single-point calibration or linear regression) for the majority of the analytes. The final method with a PFV adjusted to 1.30 was validated with respect to ICH guideline Q2(R1).

Thiol-ene enabled preparation of S-lipidated anti-HBV peptides.

Despite significant efforts made towards treatments for Hepatitis B virus (HBV), a long-term curative treatment has thus far eluded scientists. Recently, the Sodium Taurocholate Co-Transporting Polypeptide (NTCP) receptor has been identified as the entry pathway of HBV into hepatocytes. Myrcludex B, an N-terminally myristoylated 47-mer peptide mimic of the preS1 domain of the Hepatitis B virion, was identified as a potent protein-protein interaction (PPI) inhibitor blocking HBV fusion (IC50 = 140 pM). Herein we report an optimised chemical synthesis of Myrcludex B and a series of novel analogues. Employing a small modification to the Cysteine Lipidation of a Peptide or Amino acid (CLipPA) thiol-ene reaction, a library of S-lipidated Myrcludex B and truncated (21-mer) analogues were prepared, providing novel chemical space to probe for the discovery of novel anti-HBV peptides. The S-lipidated analogues showed an equivalent or a slight decrease (∼2-fold) in binding effectiveness to NTCP expressing hepatocytes compared to Myrcludex B. Three S-lipidated analogues were highly potent HBV inhibitors (IC50 0.97-3.32 nM). These results demonstrate that incorporation of heteroatoms into the lipid 'anchor' is tolerated by this antiviral scaffold and to the best of our knowledge constitutes the first report of potent S-lipidated antiviral peptides. Interestingly, despite only moderate reductions in binding effectiveness, truncated analogues possessed dramatically reduced inhibitory activity thus providing new insights into the structure activity relationship of these hitherto unreported antiviral S-lipopeptides.

Green synthesis, antimicrobial, antibiofilm and antitumor activities of superparamagnetic γ-Fe2O3 NPs and their molecular docking study with cell wall mannoproteins and peptidoglycan.

Fatty acids-assisted superparamagnetic maghemite (γ-Fe2O3) NPs was biologically synthesized using extract of polyherbal drug Liv52 (L52E). The NPs were characterized by UV-vis spectroscopy, FT-IR, SEM, TEM, EDX, XRD and VSM. The major biological molecules present in L52E analysed by GC-MS were saturated fatty acids (palmitic acid 21.95%; stearic acid 13.99%; myristic acid 1.14%), monounsaturated fatty acid (oleic acid 18.43%), polyunsaturated fatty acid (linoleic acid 20.45%), and aromatic phenol (cardanol monoene 11.92%) that could imply in bio-fabrication and stabilization of γ-Fe2O3 NPs. The FT-IR spectra revealed involvement of carboxylic group of fatty acids, amide group of proteins and hydroxyl group of phenolic compounds that acts as reducing and capping agents. The synthesized NPs were used to investigate their antimicrobial, antibiofilm activity against P. aeruginosa, MRSA and C. albicans and anticancer activity on colon cancer cells (HCT-116) for biomedical applications. Further, molecular docking study was performed to explore the interaction of Fe2O3 NPs with major cell wall components i.e., peptidoglycan and mannoproteins. The docking studies revealed that Fe2O3 interacted efficiently with peptidoglycan and mannoproteins and Fe2O3 get accommodated into catalytic cleft of mannoprotein. Due to magnetic property, the biological activity of γ-Fe2O3 can be further enhanced by applying external magnetic field alone or in amalgamation with other therapeutics drugs.

Aggregation Behavior, Antibacterial Activity and Biocompatibility of Catanionic Assemblies Based on Amino Acid-Derived Surfactants.

The surface activity, aggregates morphology, size and charge characteristics of binary catanionic mixtures containing a cationic amino acid-derived surfactant N(π), N(τ)-bis(methyl)-L-Histidine tetradecyl amide (DMHNHC14) and an anionic surfactant (the lysine-based surfactant Nα-lauroyl-Nεacetyl lysine (C12C3L) or sodium myristate) were investigated for the first time. The cationic surfactant has an acid proton which shows a strong pKa shift irrespective of aggregation. The resulting catanionic mixtures exhibited high surface activity and low critical aggregation concentration as compared with the pure constituents. Catanionic vesicles based on DMHNHC14/sodium myristate showed a monodisperse population of medium-size aggregates and good storage stability. According to Small-Angle X-Ray Scattering (SAXS), the characteristics of the bilayers did not depend strongly on the system composition for the positively charged vesicles. Negatively charged vesicles (cationic surfactant:myristate ratio below 1:2) had similar bilayer composition but tended to aggregate. The DMHNHC14-rich vesicles exhibited good antibacterial activity against Gram-positive bacteria and their bactericidal effectivity declined with the decrease of the cationic surfactant content in the mixtures. The hemolytic activity and cytotoxicity of these catanionic formulations against non-tumoral (3T3, HaCaT) and tumoral (HeLa, A431) cell lines also improved by increasing the ratio of cationic surfactant in the mixture. These results indicate that the biological activity of these systems is mainly governed by the cationic charge density, which can be modulated by changing the cationic/anionic surfactant ratio in the mixtures. Remarkably, the incorporation of cholesterol in those catanionic vesicles reduces their cytotoxicity and increases the safety of future biomedical applications of these systems.

The Effect of Olive Fruit Fly Bactrocera oleae (Rossi) Infestation on Certain Chemical Parameters of Produced Olive Oils.

Olives affected by active and damaging infestation (olive fruit fly Bactrocera oleae (Rossi)) were assayed for their chemical composition. Biophenols were determined by HPLC, sterols, triterpenic dialcohols, and fatty acids by gas chromatography analysis. The acquired data were statistically analyzed. Oils produced from "Istrska belica" fruit affected by active infestation compared to the oils made from fruit affected by damaging infestation showed higher amounts of total oleuropein biofenols (377.3 versus (vs.) 106.6 mg/kg), total biophenols (755 vs. 377 mg/kg), lignans (85.3 vs. 32.9 mg/kg), the dialdehydic form of decarboxymethyl oleuropein aglycone (DMO-Agl-dA) (148.3 vs. 49.0 mg/kg), its oxidized form (DMO-Agl-dA)ox (35.2 vs. 8.5 mg/kg), the dialdehydic form of oleuropein aglycone (O-Agl-dA) (61.1 vs. 8.0 mg/kg), the dialdehydic form of ligstroside aglycone (L-Agl-dA) (63.5 vs. 28.0 mg/kg), the aldehydic form of oleuropein aglycone (O-Agl-A) (40.6 vs. 8.4 mg/kg), and lower amounts of tyrosol (Tyr) (6.0 vs. 13. 9 mg/kg) and the aldehydic form of ligstroside aglycone (L-Agl-A) (13.8 vs. 40.3 mg/kg). Higher values of stigmasterol (2.99%) and lower values of campesterol (2.25%) were determined in oils affected by damaging infestation; an increase in triterpenic dialcohols was also observed (3.04% for damaging and 1.62% for active infestation). Oils affected by damaging infestation, compared to active infestation, showed lower amounts of oleic acid (73.89 vs. 75.15%) and higher amounts of myristic (0.013 vs. 0.011%), linoleic (7.27 vs. 6.48%), and linolenic (0.74 vs. 0.61%) acids.

Impact of Silicone Oil on Free Fatty Acid Particle Formation due to Polysorbate 20 Degradation.

PURPOSE: Polysorbate 20 (PS20), a commonly used surfactant in biopharmaceutical formulations, can undergo hydrolytic degradation resulting in free fatty acids (FFAs) that precipitate to form particles. This work investigates the ability for silicone oil (si-oil) coated on the interior walls of prefilled syringes (PFSs) to act as a sink for FFAs and potentially delay FFA particle formation. METHODS: Myristic acid distribution coefficient was measured in a two-phase system containing si-oil and formulation buffer at a range of aqueous conditions. An empirical model was built from these data to predict distribution coefficient based on aqueous conditions. To verify the model, PS20 was degraded using model lipases side-by-side in glass vials and PFSs while monitoring sub-visible particles. RESULTS: The empirical model demonstrates that the partitioning of myristic acid into si-oil is maximized at low pH and low PS20 concentration. The model predicts that the presence of si-oil at levels typical in PFSs provides at most an 8.5% increase in the total carrying capacity for myristic acid compared to a non-coated glass vial. The time to onset of FFA particles was equivalent between degradations performed in two PFS models coated with differing levels of silicone oil and in non-coated glass vials. CONCLUSION: Herein, we demonstrate that FFAs partition from aqueous solution into si-oil. However, the extent of the partitioning effect is not large enough to delay PS20-related FFA particle formation at typical formulation conditions (pH 5.0-7.5, 0.01% - 0.1% w/v PS20) filled in typical PFSs (<1.0 mg si-oil/mL aqueous fill).

Improving Prediction of Free Fatty Acid Particle Formation in Biopharmaceutical Drug Products: Incorporating Ester Distribution during Polysorbate 20 Degradation.

Polysorbate 20 (PS20) is a commonly used surfactant in biopharmaceutical formulations. It is a heterogeneous surfactant containing a distribution of fatty acid esters, which are subject to hydrolytic degradation, generating free fatty acids (FFAs). The FFAs can form visible or subvisible particles in drug product on stability. A previous FFA solubility model, developed by our group, predicts solubility limits for the three most prevalent FFA degradation products of PS20: lauric, myristic, and palmitic acid. The model takes into account two formulation parameters, pH and PS20 concentration, and their effect on FFA solubility. This work identifies a third parameter that has an impact on FFA solubility: PS20 ester distribution. When PS20 is hydrolytically degraded, the ester distribution of the remaining surfactant changes on stability. Ester distribution is known to influence the critical micelle concentration (CMC) of PS20 such that the monoesters have a much higher CMC compared to the higher-order esters (HOE). We hypothesize that as PS20 degrades, the CMC changes, affecting the proportion of PS20 that is present in micelles and capable of sequestering and solubilizing FFAs in these micelles. Here, PS20 was separated into monoester, HOE, and polyol fractions. The monoester and HOE fractions were mixed together to generate the mock degradation profiles of hydrolytically degraded PS20. FFA solubility was measured as a function of the concentration of these mock-degraded (MD) PS20s. The results indicate that ester distribution does have an impact on FFA solubility, especially at higher MD PS20 concentrations. HOEs solubilize up to 30 µg/mL more lauric acid than an equivalent amount of monoesters at a MD PS20 level of 0.06% w/v. With the addition of % HOE peak area fraction as a third parameter representing the ester distribution of PS20, the refined FFA solubility model more accurately predicts FFA solubility in protein formulations at 5 °C. The refined model suggests that drug products containing trace levels of host cell proteins (HCPs) that preferentially degrade HOEs of PS20 are at a higher risk of particle formation.

Preformulation Studies of a Stable PTEN-PDZ Lipopeptide Able to Cross an In Vitro Blood-Brain-Barrier Model as a Potential Therapy for Alzheimer's Disease.

PURPOSE: Amyloid ß (Aß) drives the accumulation of excess Phosphatase and Tensin Homolog Deleted on Chromosome 10 (PTEN) at synapses, inducing synaptic depression and perturbing memory. This recruitment of PTEN to synapses in response to Aß drives its interaction with PSD95/Disc large/Zonula occludens-1 (PDZ) proteins and, indeed, we previously showed that an oligo lipopeptide (PTEN-PDZ) capable of blocking such PTEN:PDZ interactions rescues the synaptic and cognitive deficits in a mouse model of Alzheimer's disease. Hence, the PTEN:PDZ interaction appears to be crucial for Aß-induced synaptic and cognitive impairment. Here we have evaluated the feasibility of using PTEN-PDZ lipopeptides based on the human/mouse PTEN C-terminal sequence, testing their stability in biological fluids, their cytotoxicity, their ability to self-assemble and their in vitro blood-brain barrier (BBB) permeability. Myristoyl or Lauryl tails were added to the peptides to enhance their cell permeability. METHODS: Lipopeptides self assembly was assessed using electron microscopy and the thioflavin T assay. Stability studies in mouse plasma (50%), intestinal washing, brain and liver homogenates as well as permeability studies across an all human 2D blood-brain barrier model prepared with human cerebral endothelial cells (hCMEC/D3) and human astrocytes (SC-1800) were undertaken. RESULTS: The mouse lauryl peptide displayed enhanced overall stability in plasma, ensuring a longer half-life in circulation that meant there were larger amounts available for transport across the BBB (Papp0-4h: 6.28 ± 1.85 × 10-6 cm s-1). CONCLUSION: This increased availability, coupled to adequate BBB permeability, makes this peptide a good candidate for therapeutic parenteral (intravenous, intramuscular) administration and nose-to-brain delivery. Graphical Abstract.

A Novel Approach to Bacterial Expression and Purification of Myristoylated Forms of Neuronal Calcium Sensor Proteins.

N-terminal myristoylation is a common co-and post-translational modification of numerous eukaryotic and viral proteins, which affects their interaction with lipids and partner proteins, thereby modulating various cellular processes. Among those are neuronal calcium sensor (NCS) proteins, mediating transduction of calcium signals in a wide range of regulatory cascades, including reception, neurotransmission, neuronal growth and survival. The details of NCSs functioning are of special interest due to their involvement in the progression of ophthalmological and neurodegenerative diseases and their role in cancer. The well-established procedures for preparation of native-like myristoylated forms of recombinant NCSs via their bacterial co-expression with N-myristoyl transferase from Saccharomyces cerevisiae often yield a mixture of the myristoylated and non-myristoylated forms. Here, we report a novel approach to preparation of several NCSs, including recoverin, GCAP1, GCAP2, neurocalcin δ and NCS-1, ensuring their nearly complete N-myristoylation. The optimized bacterial expression and myristoylation of the NCSs is followed by a set of procedures for separation of their myristoylated and non-myristoylated forms using a combination of hydrophobic interaction chromatography steps. We demonstrate that the refolded and further purified myristoylated NCS-1 maintains its Са2+-binding ability and stability of tertiary structure. The developed approach is generally suited for preparation of other myristoylated proteins.

Insulin-Sensitizing Activity of Sub-Nanoscaled Polyalkoxyvanadate Clusters.

Sub-nanoscaled polyalkoxyvanadates (PAOVs) functionalized with various aliphatic acids are evaluated for their insulin-sensitizing activity in lowering the blood glucose levels of diabetic mice in typical glucose tolerance tests. All the PAOVs can restore the blood glucose to normal levels after a single oral administration of PAOVs. Among them, the myristic acid-modified PAOVs enable the response of insulin to the repeated glucose challenges, lasting for up to 13 h. The combined administration of PAOVs exerts better glucose control over insulin alone, while the capric acid- and myristic acid-modified ones can enhance the responsiveness of insulin to glucose challenge and is comparable to a clinical-used derivative of insulin. Interestingly, continuous glucose monitoring shows that myristic acid-modified PAOV derivatives sensitize the responsiveness of insulin, almost matching with that of a healthy pancreas. These discoveries open up new opportunities for the application of PAOVs to promote glucose-responsive and long-lasting activity of insulin, which are expected to aid the accurate blood glucose control in insulin therapy while reducing the number of insulin administrations.