Chromatographic separation by RPLC-ESI-MS of all hydroxyproline isomers for the characterization of collagens from different sources.

During collagen biosynthesis, proline is post-translationally converted to hydroxyproline by specific enzymes. This amino acid, unique to collagen, plays a crucial role in stabilizing the collagen triple helix structure and could serve as an important biomarker for collagen content and quality analysis. Hydroxyproline has four isomers, depending on whether proline is hydroxylated at position 4 or 3 and on whether the cis- or trans- conformation is formed. Moreover, as extensive hydrolysis of collagen is required for its amino acid analysis, epimerization may also occur, although to a lesser extent, giving a total of eight possible isomers. The aim of the present study was to develop a reversed-phase high-performance liquid chromatography-UV-mass spectrometry (RPLC-UV-MS) method for the separation and quantification of all eight hydroxyproline isomers. After the chiral derivatization of the hydroxyproline isomers with Nα-(2,4-dinitro-5-fluorophenyl)-L-valinamide (L-FDVA), to enable their UV detection, the derivatized diastereoisomers were separated by testing different C18 column technologies and morphologies and optimizing operative conditions such as the mobile phase composition (solvent, additives), elution mode, flow rate and temperature. Baseline resolution of all eight isomers was achieved on a HALO® ES-C18 reversed-phase column (150×1.5 mm, 2.7 µm, 160 Å) using isocratic elution and MS-compatible mobile phase. The optimized method was validated for the quantification of hydroxyproline isomers and then applied to different collagen hydrolysates to gain insight and a deeper understanding of hydroxyproline abundances in different species (human, chicken) and sources (native, recombinant).

Effect of glycosylation on the affinity of the MTB protein Ag85B for specific antibodies: towards the design of a dual-acting vaccine against tuberculosis.

BACKGROUND: To create a dual-acting vaccine that can fight against tuberculosis, we combined antigenic arabino-mannan analogues with the Ag85B protein. To start the process, we studied the impact of modifying different parts of the Ag85B protein on its ability to be recognized by antibodies. RESULTS: Through our research, we discovered that three modified versions of the protein, rAg85B-K30R, rAg85B-K282R, and rAg85B-K30R/K282R, retained their antibody reactivity in healthy individuals and those with tuberculosis. To further test the specificity of the sugar AraMan for AraMan antibodies, we used Human Serum Albumin glycosylated with AraMan-IME and Ara3Man-IME. Our findings showed that this specific sugar was fully and specifically modified. Bio-panning experiments revealed that patients with active tuberculosis exhibited a higher antibody response to Ara3Man, a sugar found in lipoarabinomannan (LAM), which is a major component of the mycobacterial cell wall. Bio-panning with anti-LAM plates could eliminate this increased response, suggesting that the enhanced Ara3Man response was primarily driven by antibodies targeting LAM. These findings highlight the importance of Ara3Man as an immunodominant epitope in LAM and support its role in eliciting protective immunity against tuberculosis. Further studies evaluated the effects of glycosylation on the antibody affinity of recombinant Ag85B and its variants. The results indicated that rAg85B-K30R/K282R, when conjugated with Ara3Man-IME, demonstrated enhanced antibody recognition compared to unconjugated or non-glycosylated versions. CONCLUSIONS: Coupling Ara3Man to rAg85B-K30R/K282R could lead to the development of effective dual-acting vaccines against tuberculosis, stimulating protective antibodies against both AraMan and Ag85B, two key tuberculosis antigens.

Combination of a solid phase extraction and a two-dimensional LC-UV method for the analysis of vitamin D3 and its isomers in olive oil.

The current HPLC methods for the quantification of vitamin D3 (VitD3) and its two isomers previtamin D3 (PreVitD3) and trans-vitamin D3 (trans-VitD3) in olive oil preparations present some limitations mainly due to peak overlapping of the oily matrix components with the compounds of interest. The use of two-dimensional liquid chromatography (2D-LC) with different retention mechanism can reach higher resolving power thus allowing the analysis of complex samples. The present paper proposes a new alternative method including a solid phase extraction sample preparation step and a two-dimensional liquid chromatographic analysis using routine instrumentation, fitting the needs of quality assurance and quality control laboratories of pharmaceutical companies. The extraction protocol was demonstrated to provide a clean-up of the sample and a quantitative recovery of the species of interest. The 2D method proved its suitability in the isolation of vitamins from oil components in the first dimension and the separation and quantification of the analytes in the second dimension thanks to the orthogonal selectivities of phenyl and porous graphitic carbon (PGC) stationary phases. The method was validated following ICH guidelines and possesses an adequate sensitivity to quantify the impurity trans-VitD3 in pharmaceuticals considering the limits imposed by regulatory agencies. The applicability of the phenyl x PGC 2D-LC-UV method to quality control of medicinal products based on VitD3 in olive oil was confirmed by the successful quantification of vitamins in olive oil formulations.

Glycovaccine Design: Optimization of Model and Antitubercular Carrier Glycosylation via Disuccinimidyl Homobifunctional Linker.

Conjugation via disuccinimidyl homobifunctional linkers is reported in the literature as a convenient approach for the synthesis of glycoconjugate vaccines. However, the high tendency for hydrolysis of disuccinimidyl linkers hampers their extensive purification, which unavoidably results in side-reactions and non-pure glycoconjugates. In this paper, conjugation of 3-aminopropyl saccharides via disuccinimidyl glutarate (DSG) was exploited for the synthesis of glycoconjugates. A model protein, ribonuclease A (RNase A), was first considered to set up the conjugation strategy with mono- to tri- mannose saccharides. Through a detailed characterization of synthetized glycoconjugates, purification protocols and conjugation conditions have been revised and optimized with a dual aim: ensure high sugar-loading and avoid the presence of side reaction products. An alternative purification approach based on hydrophilic interaction liquid chromatography (HILIC) allowed the formation of glutaric acid conjugates to be avoided, and a design of experiment (DoE) approach led to optimal glycan loading. Once its suitability was proven, the developed conjugation strategy was applied to the chemical glycosylation of two recombinant antigens, native Ag85B and its variant Ag85B-dm, that are candidate carriers for the development of a novel antitubercular vaccine. Pure glycoconjugates (≥99.5%) were obtained. Altogether, the results suggest that, with an adequate protocol, conjugation via disuccinimidyl linkers can be a valuable approach to produce high sugar-loaded and well-defined glycovaccines.

Development of a rapid, efficient, and reusable magnetic bead-based immunocapture system for recombinant human procollagen type II isolation from yeast fermentation broth.

Recombinant collagen production, especially using yeasts as expression systems, could represent a promising alternative over traditional extractive methods from animal sources, offering controllable, scalable, and high-quality products. Monitoring the efficiency and efficacy of procollagen/collagen expression, especially in the initial fermentation phases, can be difficult and time consuming, as biological matrices necessitate purification and commonly used analytical methods are only partially informative. We propose a straightforward, efficient, and reusable immunocapture system able to specifically isolate human procollagen type II from fermentation broths and to release it in few experimental steps. A recovered sample allows for a detailed characterization providing information on structural identity and integrity, which can strongly support the monitoring of fermentation processes. The immunocapture system relies on the use of protein A-coated magnetic beads which have been functionalized and cross-linked with a human anti-procollagen II antibody (average immobilization yield of 97.7%) to create a stable and reusable support for the specific procollagen fishing. We set up the binding and release conditions ensuring specific and reproducible binding with a synthetic procollagen antigen. The absence of non-specific interaction with the support and binding specificity was demonstrated, and the latter was also confirmed by a peptide mapping epitope study in reversed-phase liquid chromatography high-resolution mass spectrometry (RP-LC-HRMS). The bio-activated support proved to be reusable and stable over 21 days from the initial use. Finally, the system was successfully tested on a raw yeast fermentation sample to provide a proof of concept of the applicability within recombinant collagen production.

Effect of mobile phase pH on liquid chromatography retention of mepartricin related compounds and impurities as support to the structural investigation by liquid chromatography-mass spectrometry.

Mepartricin is a semisynthetic polyene macrolide with antifungal and anti-protozoal activities, and it is widely used for the treatment of benign prostatic hyperplasia. Mepartricin is produced by synthetic methyl esterification of the more toxic partricin, and its activity is due to a complex of related compounds. Among them, the main ones are mepartricin B and mepartricin A which are characterized by the presence of a primary and a secondary amine group, respectively. In this work a previously reported HPLC-UV method was properly modified to make it MS-compatible. The selected conditions entail the use of a C18 reverse phase column, and a mobile phase composed by ammonium formate and acetonitrile, with the addition of heptafluorobutyric acid as modifier. The developed method was applied to the characterization of a mepartricin reference standard and a mepartricin experimental batch. All the UV responding peaks, 30 for the standard and 21 for the experimental batch, were successfully detected by MS, allowing to define their m/z values and acquire their fragmentation spectra. For the structural elucidation of isobaric species and, in particular, the identification of toxic partricin-related impurities, the presence of differently ionisable chemical groups was considered, as partricins contain free caboxy-groups, while mepartricins represent their estherified counterparts. A deep study of the effect of mobile phase pH on the chromatographic retention of partricin and mepartricin related compounds was performed in the pH range 2.5-6.5. This study allowed to successfully cluster all the detected species and asses, in the considered batch, the absence of other partricin-related impurities in addition to partricin B and partricin A.

Multi-approach LC-MS methods for the characterization of species-specific attributes of monoclonal antibodies from plants.

In this work, an analytical platform based on the use of chromatography and mass spectrometry (MS), has been applied to the characterization of Rituximab (RTX) obtained from two plant expression systems (rice and tobacco) in comparison to the mammalian cell-derived reference monoclonal antibody (mAb). Different chromatographic approaches, hyphenated to high resolution MS (HRMS), were applied to RTX structural investigation both at middle- and peptide level. In particular, cation exchange chromatography (CEX), size exclusion chromatography (SEC), reversed phase (RPLC) and hydrophilic interaction liquid chromatographic (HILIC) methods were developed and applied on intact mAbs, IdeS-, and trypsin digests in order to address critical attributes such as primary structure, glycan composition, species-related heterogeneity, glycosylation degree, charge variants, aggregation tendency and enzymatic stability. All the collected data highlight the features and criticalities of each production approach. Production in rice results in a heterogeneous but stable product over time, suggesting the absence of proteases in seeds; while tobacco expression system leads to more homogeneous glycosylation, but protein stability seems to be a critical issue probably due to the presence of proteases. This analytical strategy represents a robust support to scientists in the selection and optimization of the best plant expression system to produce recombinant humanized mAbs.

Monolithic Papain-Immobilized Enzyme Reactors for Automated Structural Characterization of Monoclonal Antibodies.

The characterization of monoclonal antibodies (mAbs) requires laborious and time-consuming sample preparation steps before the liquid chromatography-mass spectrometry (LC-MS) analysis. Middle-up approaches entailing the use of specific proteases (papain, IdeS, etc.) emerged as practical and informative methods for mAb characterization. This work reports the development of immobilized enzyme reactors (IMERs) based on papain able to support mAb analytical characterization. Two monolithic IMERs were prepared by the covalent immobilization of papain on different supports, both functionalized via epoxy groups: a Chromolith® WP 300 Epoxy silica column from Merck KGaA and a polymerized high internal phase emulsion (polyHIPE) material synthesized by our research group. The two bioreactors were included in an in-flow system and characterized in terms of immobilization yield, kinetics, activity, and stability using Nα-benzoyl-L-arginine ethyl ester (BAEE) as a standard substrate. Moreover, the two bioreactors were tested toward a standard mAb, namely, rituximab (RTX). An on-line platform for mAb sample preparation and analysis with minimal operator manipulation was developed with both IMERs, allowing to reduce enzyme consumption and to improve repeatability compared to in-batch reactions. The site-specificity of papain was maintained after its immobilization on silica and polyHIPE monolithic supports, and the two IMERs were successfully applied to RTX digestion for its structural characterization by LC-MS. The main pros and cons of the two supports for the present application were described.

The Influence of Ripeness on the Phenolic Content, Antioxidant and Antimicrobial Activities of Pumpkins (Cucurbita moschata Duchesne).

Cucurbita moschata Duchesne (Cucurbitaceae) is a plant food highly appreciated for the content of nutrients and bioactive compounds, including polyphenols and carotenoids, which contribute to its antioxidant and antimicrobial capacities. The purpose of this study was to identify phenolic acids and flavonoids of Cucurbita moschata Duchesne using high-performance liquid chromatography-diode array detection-electrospray ionization tandem mass spectrometry (HPLC-DAD-ESI-MS) at different ripening stages (young, mature, ripened) and determine its antioxidant and antimicrobial activities. According to the results, phenolic acids and flavonoids were dependent on the maturity stage. The mature fruits contain the highest total phenolic and flavonoids contents (97.4 mg GAE. 100 g-1 and 28.6 mg QE. 100 g-1).A total of 33 compounds were identified. Syringic acid was the most abundant compound (37%), followed by cinnamic acid (12%) and protocatechuic acid (11%). Polyphenol extract of the mature fruits showed the highest antioxidant activity when measured by DPPH (0.065 µmol TE/g) and ABTS (0.074 µmol TE/g) assays. In the antimicrobial assay, the second stage of ripening had the highest antibacterial activity. Staphylococcus aureus was the most sensitive strain with an inhibition zone of 12 mm and a MIC of 0.75 mg L-1. The lowest inhibition zone was obtained with Salmonella typhimurium (5 mm), and the MIC value was 10 mg L-1.

Bio-Guided Fractionation of Stem Bark Extracts from Phyllanthus muellarianus: Identification of Phytocomponents with Anti-Cholinesterase Activity.

A combination of flash chromatography, solid phase extraction, high-performance liquid chromatography, and in vitro bioassays was used to isolate phytocomponents endowed with anticholinesterase activity in extract from Phyllanthus muellarianus. Phytocomponents responsible for the anti-cholinesterase activity of subfractions PMF1 and PMF4 were identified and re-assayed to confirm their activity. Magnoflorine was identified as an active phytocomponent from PMF1 while nitidine was isolated from PMF4. Magnoflorine was shown to be a selective inhibitor of human butyrylcholinesterase-hBChE (IC50 = 131 ± 9 µM and IC50 = 1120 ± 83 µM, for hBuChE and human acetylcholinesterase-hAChE, respectively), while nitidine showed comparable inhibitory potencies against both enzymes (IC50 = 6.68 ± 0.13 µM and IC50 = 5.31 ± 0.50 µM, for hBChE and hAChE, respectively). When compared with the commercial anti-Alzheimer drug galanthamine, nitidine was as potent as galanthamine against hAChE and one order of magnitude more potent against hBuChE. Furthermore, nitidine also showed significant, although weak, antiaggregating activity towards amyloid-ß self-aggregation.

Hovenia dulcis Thumberg: Phytochemistry, Pharmacology, Toxicology and Regulatory Framework for Its Use in the European Union.

Hovenia dulcis Thunberg is an herbal plant, belonging to the Rhamnaceae family, widespread in west Asia, USA, Australia and New Zealand, but still almost unknown in Western countries. H. dulcis has been described to possess several pharmacological properties, such as antidiabetic, anticancer, antioxidant, anti-inflammatory and hepatoprotective, especially in the hangover treatment, validating its use as an herbal remedy in the Chinese Traditional Medicine. These biological properties are related to a variety of secondary metabolites synthesized by the different plant parts. Root, bark and leaves are rich of dammarane-type triterpene saponins; dihydrokaempferol, quercetin, 3,3',5',5,7-pentahydroflavone and dihydromyricetin are flavonoids isolated from the seeds; fruits contain mainly dihydroflavonols, such as dihydromyricetin (or ampelopsin) and hovenodulinol, and flavonols such as myricetin and gallocatechin; alkaloids were found in root, barks (frangulanin) and seeds (perlolyrin), and organic acids (vanillic and ferulic) in hot water extract from seeds. Finally, peduncles have plenty of polysaccharides which justify the use as a food supplement. The aim of this work is to review the whole scientific production, with special focus on the last decade, in order to update phytochemistry, biological activities, nutritional properties, toxicological aspect and regulatory classification of H. dulcis extracts for its use in the European Union.

Design of epidermal growth factor immobilization on 3D biocompatible scaffolds to promote tissue repair and regeneration.

Exogenous application of human epidermal growth factor (hEGF) stimulates epidermal wound healing. The aim of this study was to develop bioconjugates based on hEGF mimicking the protein in its native state and thus suitable for tissue engineering applications, in particular for treating skin-related disorders as burns. Ribonuclease A (RNase A) was used to investigate a number of different activated-agarose carriers: cyanogen bromide (CNBr)-activated-agarose and glyoxyl-agarose showed to preserve the appropriate orientation of the protein for receptor binding. EGF was immobilized on these carriers and immobilization yield was evaluated (100% and 12%, respectively). A peptide mapping of unbound protein regions was carried out by LC-MS to take evidence of the residues involved in the immobilization and, consequently, the flexibility and surface accessibility of immobilized EGF. To assess cell proliferative activities, 10, 25, 50, and 100 ng/mL of each immobilized EGF sample were seeded on fibroblast cells and incubated for 24, 48 and 72 h. The immobilized growth factor showed significantly high cell proliferative activity at 50 and 100 ng/mL compared to control and soluble EGF. Although both of the immobilized samples show dose-dependency when seeded with high number of fibroblast cells, CNBr-agarose-EGF showed a significantly high activity at 100 ng/mL and 72 h incubation, compared to glyoxyl-agarose-EGF.

Nature-derived compounds modulating Wnt/ ß -catenin pathway: a preventive and therapeutic opportunity in neoplastic diseases.

The Wnt/ß-catenin signaling is a conserved pathway that has a crucial role in embryonic and adult life. Dysregulation of the Wnt/ß-catenin pathway has been associated with diseases including cancer, and components of the signaling have been proposed as innovative therapeutic targets, mainly for cancer therapy. The attention of the worldwide researchers paid to this issue is increasing, also in view of the therapeutic potential of these agents in diseases, such as Parkinson's disease (PD), for which no cure is existing today. Much evidence indicates that abnormal Wnt/ß-catenin signaling is involved in tumor immunology and the targeting of Wnt/ß-catenin pathway has been also proposed as an attractive strategy to potentiate cancer immunotherapy. During the last decade, several products, including naturally occurring dietary agents as well as a wide variety of products from plant sources, including curcumin, quercetin, berberin, and ginsenosides, have been identified as potent modulators of the Wnt/ß-catenin signaling and have gained interest as promising candidates for the development of chemopreventive or therapeutic drugs for cancer. In this review we make an overview of the nature-derived compounds reported to have antitumor activity by modulating the Wnt/ß-catenin signaling, also focusing on extraction methods, chemical features, and bio-activity assays used for the screening of these compounds.

Chromatographic profiling of silk sericin for biomedical and cosmetic use by complementary hydrophylic, reversed phase and size exclusion chromatographic methods.

Silk sericin (SS) is, together with silk fibroin (SF), one of the two proteins forming the silkworm cocoon. SS is ideal ingredient for cosmetic applications in the formulation of specific products for skin care and hair due to its peculiar physical-chemical composition. SS also showed a great potential in different pharmacological and biotechnological applications, as anticancer drug, anticoagulant, cell culture additive, wound healing agent and drug delivery carrier. Reasons for SS use in biomedical applications derive from its physical-chemical composition. As a consequence, a detailed characterization of SS in terms of average molecular weight, molecular weight distribution and hydro/lipophilic character is crucial to properly address and assess its quality, cosmetic or pharmacological use. In this study, the application of different and complementary chromatographic modes allows a detailed investigation of SS protein isolated from wastewater using two diverse extraction methods. Hydrophilic interaction liquid chromatography (HILIC using an AdvanceBio Glycan Map column) and reverse phase (RP using Symmetry300 C18 column) were applied to intact protein characterization to derive data on protein hydrophilicity and on hydrophobic components of the two SS preparations (SS#1 and SS#2). A higher hydrophilic character of SS#1 was observed by HILIC trace, coherently with the preparation method used, while no significant differences in hydrophobicity were detectable in the RPLC separations. Size distribution was also defined by using a SEC-UV-MS method (using TSKgel SuperSW2000 column) properly optimized to maximize both the size selectivity and the method sensitivity. Taken together, the chromatographic data allowed to better characterize the SS samples obtained by different extraction methods, and the structural properties were correlated to their biological activities.

Chromatographic tools for plant-derived recombinant antibodies purification and characterization.

In the last two decades, plants became an interesting alternative for the production of recombinant proteins for human therapy and several antibodies expressed in plants have reached the clinical development stage. Plants are capable of post-translational modifications (PTMs) necessary for protein activity and pharmacokinetics, such as glycosylation. However, there are important kingdom-specific modifications that have to be considered when expressing recombinant proteins. Therefore, there is a need for efficient analytical methods for deep protein characterization starting from the expression platform design until the product approval to guarantee product authenticity, quality and efficacy. Literature lacks of reviews dealing with plant-derived proteins purification and characterization by chromatographic methods, thus the focus of the present review is on this topic for the most representative biotechnological drugs i.e. monoclonal antibodies (mAbs). In the first part, a comprehensive discussion of the methods applied in dowstream processes (extraction and clarification) and a detailed overview of the chromatographic techniques useful for the purification of plant-made mAbs are reported. Among purification techniques, Protein A affinity chromatography, ion-exchange chromatography, hydrophobic interaction chromatography, hydrophobic charge induction chromatography or mixed mode chromatography are described. In the second part, we will discuss analytical platforms based on chromatographic techniques (reverse phase, size exclusion chromatography, ion-exchange chromatography, hydrophilic interaction liquid chromatography) coupled with different detection systems (UV, Fluorescence, MS) used at protein, peptide and glycan level to characterize plant-made mAbs with their unique features.

Application of an HPLC-MS/MS method for Teicoplanin drug substance and related impurities, part 2: Identity assignment of related impurities.

A liquid chromatographic MS-compatible method was applied to the structural elucidation of Teicoplanin for identification CRS components. The method, previously developed by our group, involves the use of LiChrospher 100 RP-18 column with a mobile phase composed of ammonium formate 25 mM at pH 6.00 and acetonitrile (ACN). All the peaks with a 0.10% UV area, largely above the disregard limit of 0.15% as fixed by EMA, were considered and submitted to MS/MS fragmentation experiments. The study of MS/MS spectrum collected for Teicoplanin complex major component (namely A2-2) allowed to elucidate the fragmentation pathway and enabled the successful identity assignment of all the 42 detected species. Elution order was also rationalized. An in house batch sample of Teicoplanin was analyzed and, while the 86% of the detected species were structurally identical to those in Teicoplanin for identification CRS, five new derivatives were revealed and structurally characterized. In both the Teicoplanin samples, all the considered species were found to have a Teicoplanin-like structure that allows their classification as closely related impurities, with a significant implication in their qualification threshold.

Epitope and affinity determination of recombinant Mycobacterium tuberculosis Ag85B antigen towards anti-Ag85 antibodies using proteolytic affinity-mass spectrometry and biosensor analysis.

Tuberculosis (TB) is the first cause of death from infectious diseases worldwide. Only a single anti-TB vaccine is currently available for clinical use, but its efficacy is not achieved with certainty. The aim of this work is to provide a basis for the rational design of a neo-glycoconjugate vaccine against TB. Structural characterization of recombinant antigenic proteins from Mycobacterium tuberculosis (MTB) Ag85B (rAg85B, variants, and semi-synthetic glycoconjugates) was initially carried out. Identification of antibody epitope analyses by proteolytic affinity-mass spectrometry and surface plasmon resonance (SPR) biosensor analyses were performed in order to qualitatively identify and quantitatively characterize interaction structures of the antigens with antibodies from different sources. A commercial monoclonal antibody and polyclonal antibodies from different sources (patients with active TB, vaccinated individuals, and a healthy control) were employed to analyze antigen-antibody interactions. These combined approaches provided the identification of different assembled epitope regions on the recombinant MTB antigens, their affinity binding constants in the interactions with specific antibodies, and revealed the importance of protection from excessive glycosylation. The identified epitope peptides should constitute a suitable basis for the design of new specific target vaccines. Graphical abstract ᅟ.

A new MS compatible HPLC-UV method for Teicoplanin drug substance and related impurities, part 1: Development and validation studies.

Teicoplanin is a glycopeptide antibiotic prepared by fermentation from cultures of Actinoplanes teichomyceticus, used as drug of last resort for the treatment of bacterial infections in humans. This study, which is the first in a series of two parts, describes the development of a LC method for the separation of Teicoplanin drug substance and its related impurities compatible with MS detection. The separation conditions for Teicoplanin were set on a LiChrospher 100 RP-18 column under gradient elution with a mobile phase composed of ammonium formate 25 mM at pH 6.00 and ACN. The new method was shown equivalent in terms of selectivity to the one reported in the European Pharmacopoeia Teicoplanin monograph, and was validated according to ICH Q2 R1 guidelines for the drug substance assay. The new method offers similar performance to the compendial one but has the advantage of being fully compatible with MS and it can be proposed as a useful tool also for controlling the quality of Teicoplanin fermentation batches and the occurrence of potential impurities.

Surface Plasmon Resonance as a Tool for Ligand Binding Investigation of Engineered GPR17 Receptor, a G Protein Coupled Receptor Involved in Myelination.

The aim of this study was to investigate the potential of surface plasmon resonance (SPR) spectroscopy for the measurement of real-time ligand-binding affinities and kinetic parameters for GPR17, a G protein-coupled receptor (GPCR) of major interest in medicinal chemistry as potential target in demyelinating diseases. The receptor was directly captured, in a single-step, from solubilized membrane extracts on the sensor chip through a covalently bound anti-6x-His-antibody and retained its ligand binding activity for over 24 h. Furthermore, our experimental setup made possible, after a mild regeneration step, to remove the bound receptor without damaging the antibody, and thus to reuse many times the same chip. Two engineered variants of GPR17, designed for crystallographic studies, were expressed in insect cells, extracted from crude membranes and analyzed for their binding with two high affinity ligands: the antagonist Cangrelor and the agonist Asinex 1. The calculated kinetic parameters and binding constants of ligands were in good agreement with those reported from activity assays and highlighted a possible functional role of the N-terminal residues of the receptor in ligand recognition and binding. Validation of SPR results was obtained by docking and molecular dynamics of GPR17-ligands interactions and by functional in vitro studies. The latter allowed us to confirm that Asinex 1 behaves as GPR17 receptor agonist, inhibits forskolin-stimulated adenylyl cyclase pathway and promotes oligodendrocyte precursor cell maturation and myelinating ability.