Stepwise Frontal Analysis Coupled with Affinity Chromatography: A Fast and Reliable Method for Potential Ligand Isolation and Evaluation from Mahuang-Fuzi-Xixin Decoction.

Mahuang-Fuzi-Xixin Decoction (MFXD) is widely used in the treatment of asthma, however, the functional components in the decoction targeting beta2-adrenoceptor (ß2 -AR) remain unclear. Herein, we immobilized the haloalkane dehalogenase (Halo)-tagged ß2 -AR on the 6-chlorocaproic acid-modified microspheres. Using the affinity stationary phase, the interactions of four ligands with the receptor were analyzed by stepwise frontal analysis. The association constants were (4.75±0.28)×104  M-1 for salbutamol, (2.93±0.15)×104  M-1 for terbutaline, (1.23±0.03)×104  M-1 for methoxyphenamine, (5.67±0.38)×104  M-1 for clorprenaline at high-affinity binding site, and (2.73±0.05)×103  M-1 at low-affinity binding site. These association constants showed the same rank order as the radioligand binding assay, demonstrating that immobilized ß2 -AR had capacity to screen bioactive compounds binding to the receptor while stepwise frontal analysis could predict their binding affinities. Application of the immobilized receptor in analysis of MFXD by chromatographic method revealed that ephedrine, aconifine, karakoline, and chasmanine were the bioactive compounds targeting ß2 -AR. Among them, ephedrine and chasmanine exhibited association constants of (2.94±0.02)×104 M-1 and (4.60±0.15)×104  M-1 to the receptor by stepwise frontal analysis. Molecular docking analysis demonstrated that ephedrine, chasmanine, and the other two compounds interact with ß2 -AR through the same pocket involving the key amino acids such as Asn312, Asp113, Phe289, Trp286, Tyr316, and Val114. As such, we reasoned that the four compounds dominate the therapeutic effect of MFXD against asthma through ß2 -AR mediating pathway. This work shed light on the potential of immobilized ß2 -AR for drug discovery and provided a valuable methodology for rapid screening.

Covalent Inhibitor-Based One-Step Method for Endothelin Receptor A Immobilization: from Ligand Recognition to Lead Identification.

Protein immobilization is particularly significant in proteomics, interactomics, and in vitro drug screening. It is an essential primary step for numerous biological techniques that rely on immobilized proteins with controlled orientation, high conformational stability, and high activity (CHH). These have challenged the current immobilization strategy and demanded increasing efforts for an efficient method to meet the CHH immobilization in a single step. Herein, we proposed a covalent inhibitor-based, one-step method for G protein-coupled receptor (GPCR) immobilization inspired by the covalent reaction between an epidermal growth factor receptor (EGFR)-tag and its inhibitor ibrutinib. We immobilized endothelin receptor A (ETA) containing a fusion EGFR tag onto an ibrutinib-coated macroporous silica gel. The immobilized ETA proved to have demonstrable ligand-binding activity and specificity, thus resulting in a chromatographic technology allowing receptor-ligand interaction analysis and lead identification. Such immobilization method is attractable, owing to the properties of mild reacting conditions, fast rate, high yield, and good stability of the conjugated protein. It will be applicable to biochips, biosensors, and biocatalysts.

Identifying potential ligands specifically binding to beta1-adrenoceptor from Radix Aconiti Lateralis Praeparata extract by affinity chromatographic method.

As expressed predominantly in cardiac tissue, beta1-adrenoceptor (ß1-AR) is broadly accepted as one of the main targets for drugs against cardiovascular ailments. However, the discovery of ß1-AR ligand is gravely challenged due to the lack of efficient screening method. This work developed a general strategy for pursuing ß1-AR ligands from the herbal extract by immobilizing haloalkane dehalogenase (Halo)-tagged ß1-AR onto microspheres coated with 6-chlorohexanoic acid, and applying the immobilized ß1-AR in the analysis of ligand-receptor interaction. The morphology was characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The chromatographic specificity of the immobilized receptor column was evaluated by determining the association constants of atenolol, esmolol and metoprolol using stepwise frontal analysis plus injection amount-dependent method. The potential ligands binding to ß1-AR was screened by collecting the peak with retention time longer than the void time, and identified the collection by reverse phase liquid chromatography coupled with tandem mass spectrometry. The association constants of the three drugs to ß1-AR were (3.33 ± 0.29)× 106 M-1, (2.33 ± 0.23)× 106 M-1 and (2.06 ± 0.03)× 106 M-1, indicating a desired specificity of the immobilized receptor for recognizing its ligands. Molecular docking showed that van der Waals, hydrogen bonds, and hydrophobic interactions were the principal interaction forces for the receptor-drug complexes. Benzoylmesaconine was screened as the potential ligand of ß1-AR in Radix Aconiti Lateralis Praeparata extract. The association constant of the ligand was (1.06 ± 0.02)× 105 M-1, hinting structural modification may be required before clinical application. The immobilized ß1-AR is possible to provide a rapid method for screening potential ligands in herbal extract.

Preparation and characterization of immobilized 5-HT1A receptor stationary phase for high throughput screening of the receptor-binding ligands from complex systems like Curcuma wenyujin Y. H. Chen et C. Ling extract.

The incidence of depression has increased significantly during the COVID-19 pandemic. This disease is closely associated with serotonin 1A (5-HT1A) receptor and often treated by complex prescription containing Curcuma wenyujin Y. H. Chen et C. Ling. Therefore, we hypothesized that this herb contains bioactive compounds specially binding to the receptor. However, the rapid discovery of new ligands of 5-HT1A receptor is still challenging due to the lack of efficient screening methods. To address this problem, we developed and characterized a novel approach for the rapid screening of ligands by using immobilized 5-HT1A receptor as the chromatographic stationary phase. Briefly, haloalkane dehalogenase was fused at the C-terminal of 5-HT1A receptor, and the modified 5-HT1A receptor was immobilized on amino-microspheres by the reaction between haloalkane dehalogenase and 6-chlorohexanoic acid linker. Scanning electron microscope and X-ray photo-electron were used to characterize the morphology and element of the immobilized receptor. The binding of three specific ligands to 5-HT1A receptor was investigated by two different methods. Moreover, we examined the feasibility of 5-HT1A receptor colume in high throughput screening of new ligands from complex systems as exemplified by Curcuma wenyujin Y. H. Chen et C. Ling. Gweicurculactone, 2-hydroxy-1-(3,4-dihydroxybenzene)-7-(4'-hydroxybezene)-heptane and curcuminol F were identified as the ligands of 5-HT1A receptor with the binding energies of -7.06 kcal/mol, -7.77 kcal/mol and -5.26 kcal/mol, respectively. Collectively, these results indicated that the immobilized 5-HT1A receptor was capable of screening bioactive compound from complex system, providing an effective methodology for high throughput screening.

Development of an antimicrobial peptide-loaded mineralized collagen bone scaffold for infective bone defect repair.

The repair of infective bone defects is a great challenge in clinical work. It is of vital importance to develop a kind of bone scaffold with good osteogenic properties and long-term antibacterial activity for local anti-infection and bone regeneration. A porous mineralized collagen (MC) scaffold containing poly(d,l-lactide-co-glycolic acid) (PLGA) microspheres loaded with two antibacterial synthetic peptides, Pac-525 or KSL-W was developed and characterized via scanning electron microscopy (SEM), porosity measurement, swelling and mechanical tests. The results showed that the MC scaffold embedded with smooth and compact PLGA microspheres had a positive effect on cell growth and also had antibacterial properties. Through toxicity analysis, cell morphology and proliferation analysis and alkaline phosphatase evaluation, the antibacterial scaffolds showed excellent biocompatibility and osteogenic activity. The antibacterial property evaluated with Staphylococcus aureus and Escherichia coli suggested that the sustained release of Pac-525 or KSL-W from the scaffolds could inhibit the bacterial growth aforementioned in the long term. Our results suggest that the antimicrobial peptides-loaded MC bone scaffold has good antibacterial and osteogenic activities, thus providing a great promise for the treatment of infective bone defects.

An Antimicrobial Peptide-Loaded Gelatin/Chitosan Nanofibrous Membrane Fabricated by Sequential Layer-by-Layer Electrospinning and Electrospraying Techniques.

Guided bone regeneration (GBR) technique is widely used in the treatment of bone defects caused by peri-implantitis, periodontal disease, etc. However, the GBR membranes commonly used in clinical treatments currently have no antibacterial activity. Therefore, in this study, sequential layer-by-layer electrospinning and electrospraying techniques were utilized to prepare a gelatin (Gln) and chitosan (CS) composite GBR membrane containing hydroxyapatite nanoparticles (nHAp) and antimicrobial peptide (Pac-525)-loaded PLGA microspheres (AMP@PLGA-MS), which was supposed to have osteogenic and antibacterial activities. The scanning electron microscope (SEM) observation showed that the morphology of the nanofibers and microspheres could be successfully produced. The diameters of the electrospun fibers with and without nHAp were 359 ± 174 nm and 409 ± 197 nm, respectively, and the mechanical properties of the membrane were measured according to the tensile stress-strain curve. Both the involvement of nHAp and the chemical crosslinking were able to enhance their tensile strength. In vitro cell culture of rat bone marrow mesenchymal stem cells (rBMSCs) indicated that the Gln/CS composite membrane had an ideal biocompatibility with good cell adhesion, spreading, and proliferation. In addition, the Gln/CS membrane containing nHAp could promote osteogenic differentiation of rBMSCs. Furthermore, according to the in vitro drug release assay and antibacterial experiments, the composite GBR membrane containing AMP@PLGA-MS exhibited a long-term sustained release of Pac-525, which had bactericidal activity within one week and antibacterial activity for up to one month against two kinds of bacteria, S. aureus and E. coli. Our results suggest that the antimicrobial peptide-loaded Gln/CS composite membrane (AMP@PLGA-MS@Gln/CS/nHAp) has a great promise in bone generation-related applications for the unique functions of guiding bone regeneration and inhibiting bacterial infection as well.

[Preparation of immunoaffinity chromatographic column specific to diniconazole and its applications to the pretreatment of samples].

The purified anti-diniconazole antibody was polymerised to hydrolytic tetramethoxysilane (TMOS) to synthesize the immunosorbent for the immunoaffinity chromatographic (IAC) column specific to diniconazole. The optimized conditions of the IAC were as follows: water as equilibrium and adsorbent medium, 30% and 50% (v/v) methanol aqueous solutions as eluents. The results showed that the dynamic column capacity was up to 125.4 microg/g of bed volume. The river water and fruit samples spiked with diniconazole were cleaned up and enriched by the IAC, and the diniconazole in eluant was determined by high performance liquid chromatography. The average recoveries (n = 5) of diniconazole in river water sample were 90.36%-100.14% with relative standard deviations (RSDs) of 2.03%-6.08%, and the average recoveries in fruit samples were 85.55%-94.02% with RSDs of 3.38%-6.78%. The IAC cleanup procedure provided an effective pretreatment method for the determination of diniconazole in sample media such as river water and fruits.

Determination of diniconazole in agricultural samples by sol-gel immunoaffinity extraction procedure coupled with HPLC and ELISA.

BACKGROUND: In the European Union (EU), the use of diniconazole-M is no longer authorized. However, residues of diniconazole-M occur in various plant commodities. METHODOLOGY/PRINCIPAL FINDINGS: A selective and simple analytical method for the trace level determination of diniconazole in soil, fruit, vegetables and water samples was developed based on immunoaffinity extraction followed by Enzyme-linked immunosorbent assay (ELISA) and the high-performance liquid chromatography (HPLC) analysis. The ELISA was based on monoclonal antibodies highly specific to diniconazole and was a fast, cost-effective, and selective screening method for the detection of diniconazole. The results of the ELISA correlated well with gas chromatography (GC) results, with the correlation coefficient of 0.9879 (n = 19). A simple gel permeation chromato- graphy clean-up method was developed to purify extracts from matrices containing high amounts of fat and natural pigments, without the need for a large dilution of the sample. The immunoaffinity column (IAC) capacity was 0.180 mg g(-1). The columns could be re-used approximately 20 times with no significant alteration in capacity. The recoveries from complex samples were in the range of 89.2% to 96.1% with a relative standard deviation (RSD) of 0.770%-6.11% by ELISA. The results were in good agreement with those obtained by HPLC method. CONCLUSION/SIGNIFICANCE: The IAC extraction procedure coupled with HPLC and ELISA analysis could be also used as alternative effective analytical methods for the determination of diniconazole concentrations in complex samples.