Virus-like particle (VLP) of murine polyomavirus (MPV) is a T = 7d icosahedral capsid that self-assembles from 72 capsomeres (Caps), each of which is a pentamer of major coat protein VP1. VLP has great potential in vaccinology, gene therapy, drug delivery, and materials science. However, its application is hindered by high cost downstream processes, leading to an urgent demand of a highly efficient affinity ligand for the separation and purification of Cap by affinity chromatography. Herein a biomimetic design strategy of an affinity peptide ligand of Cap has been developed on the basis of the binding structure of the C-terminus of minor coat protein (VP2-C) on the inner surface of Cap. The molecular interactions between VP2-C and Cap were first examined using all-atom molecular dynamics (MD) simulations coupled with the molecular mechanics/Poisson–Boltzmann surface area (MM/PBSA) method, where V283, P285, D286, W287, L289, and Y296 of VP2-C were identified as the hot spots. An affinity peptide library (DWXLXLXY, X denotes arbitrary amino acids except cysteine) was then constructed for virtual screening sequently by docking with AUTODOCK VINA, binding structure comparison, and final docking with ROSETTA FlexPepDock. Ten peptide candidates were selected and further confirmed by MD simulations and MM/PBSA, where DWDLRLLY was found to have the highest affinity to Cap. In DWDLRLLY, six residues are favorable for the binding, including W2, L4, L6 and Y8 inheriting from VP2-C, and R5 and L7 selected in the virtual screening. This confirms the high efficiency and accuracy of the biomimetic design strategy. DWDLRLLY was then experimentally validated by a one-step purification of Cap from crude cell lysate using affinity chromatography with the octapeptide immobilized on Sepharose gel. The purified Caps were observed to self-assemble into VLP with consistent structure of authentic MPV.

Immobilization of silver nanoparticles (Ag NPs) to improve monodispersity and recyclability is crucial for applications in nanocatalysts. Herein, a novel protocol for stabilizer-free, effective, and in situ synthesis of Ag NPs on sulfhydryl-functionalized poly(glycidyl methacrylate) microspheres (PGMA-SH) was proposed. Ag NPs of 16.97 ± 3.15 nm were successfully grown on PGMA-SH, and remained monodisperse and stable even after sonication, washing, and long-term storage. Moreover, the Ag NPs on PGMA-SH (Ag NPs@PGMA-SH) composite exhibited excellent catalytic activity with an average normalized activity parameter of 4.38 × 10–3 L·mg–1·s–1 toward the reduction of 4-nitrophenol, which was 1.3–132 times higher than reported in literature. The composite can be easily recycled and showed excellent reusability as a conversion higher than 92% was achieved after 10 cycles. Thus, the preparation of Ag NPs@PGMA-SH has been proven a feasible, straightforward, and effective protocol, which would facilitate the applications of Ag NPs in environmental control.

Fabrication of highly efficient silver nanoparticle (Ag NP) catalysts supported on polyacrylamide (PAM)-modified poly(glycidyl methacrylate) (PGMA) microspheres was reported herein, for where PAM was used as the robust anchors because of its abundant amide groups. Well-dispersed Ag NPs with an average diameter of 9.7 nm were obtained on the PGMA–PAM microspheres (Ag NPs@PGMA–PAM). Excellent catalytic activity of Ag NPs@PGMA–PAM was observed in the reduction of 4-nitrophenol using sodium borohydride in water at room temperature, indicated by an activity parameter that was 6–1725 times higher than those reported in the literature. In addition, easy regulation on the size of Ag NPs was achieved through the adjustment on the concentration of the Ag precursor, AgNO3. Therefore, the synthetic method proposed herein was confirmed as being effective for the synthesis of the highly efficient catalyst Ag NPs@PGMA–PAM. This would contribute to the preparation of highly efficient catalyst of supported noble metals and then facilitate their applications in environmental protection.

A green and size-controlled synthesis of silver nanoparticles (Ag NPs) in aqueous solution with the assistance of L-cysteine is presented. The size of Ag NPs decreases with the increase of L-cysteine concentration, and thus can be controlled by adjusting L-cysteine concentration. TEM analysis shows that Ag NPs with an average size of 3 nm can be produced in the presence of 1.0 mmol/L L-cysteine, about one sixth of the size of Ag NPs obtained in the absence of L-cysteine (17 nm). The assynthesized silver colloidal solution is stable and can be stored at room temperature for at least two months without any precipitation. This L-cysteine assisted method is simple, feasible and efficient, and would facilitate the production and application of Ag NPs.

Virus-like particle (VLP) of murine polyomavirus (MPV) is a T = 7d icosahedral capsid that self-assembles from 72 capsomeres (Caps), each of which is a pentamer of major coat protein VP1. VLP has great potential in vaccinology, gene therapy, drug delivery, and materials science. However, its application is hindered by high cost downstream processes, leading to an urgent demand of a highly efficient affinity ligand for the separation and purification of Cap by affinity chromatography. Herein a biomimetic design strategy of an affinity peptide ligand of Cap has been developed on the basis of the binding structure of the C-terminus of minor coat protein (VP2-C) on the inner surface of Cap. The molecular interactions between VP2-C and Cap were first examined using all-atom molecular dynamics (MD) simulations coupled with the molecular mechanics/Poisson–Boltzmann surface area (MM/PBSA) method, where V283, P285, D286, W287, L289, and Y296 of VP2-C were identified as the hot spots. An affinity peptide library (DWXLXLXY, X denotes arbitrary amino acids except cysteine) was then constructed for virtual screening sequently by docking with AUTODOCK VINA, binding structure comparison, and final docking with ROSETTA FlexPepDock. Ten peptide candidates were selected and further confirmed by MD simulations and MM/PBSA, where DWDLRLLY was found to have the highest affinity to Cap. In DWDLRLLY, six residues are favorable for the binding, including W2, L4, L6 and Y8 inheriting from VP2-C, and R5 and L7 selected in the virtual screening. This confirms the high efficiency and accuracy of the biomimetic design strategy. DWDLRLLY was then experimentally validated by a one-step purification of Cap from crude cell lysate using affinity chromatography with the octapeptide immobilized on Sepharose gel. The purified Caps were observed to self-assemble into VLP with consistent structure of authentic MPV.

Molecular interactions between the von Willebrand factor (VWF) A1 domain and glycoprotein Ibα (GPIbα) promote the initial adhesion of platelets and subsequent arterial thrombus formation. However, little is understood about the interactions at a molecular level. Therefore, the binding dynamics and involved molecular interactions between VWF A1 domain and GPIbα in both water and physiological saline are investigated using molecular dynamics simulations and all-atom models. Faster binding is observed in water than that in physiological saline, and patches of opposite charges are observed at the binding interface. Moreover, molecular mechanics-Poisson–Boltzmann surface area analysis indicates that the binding is promoted by the long-range electrostatic interactions and then maintained by hydrophobic interactions. For the initial binding, the hot spots include the residues E14, E128, D175, D83, E151, D106, D63, E5, D18, E225, D235 in GPIbα, and K608, K569, K644, R571, K572, R636, K599 in VWF A1 domain. For the final complex formation, however, 72% of the favorable contributions are from hydrophobic interactions. The results provided molecular insight into the initial platelet adhesion. The hot spots identified would be beneficial for developing novel drugs for thrombotic diseases.Graphical abstract.Highlights► Molecular interactions between VWF A1 domain and GPIbα are investigated. ► Binding is promoted by the long-range electrostatic interactions. ► Final complex formation is maintained by the hydrophobic interactions. ► The hot spots for the initial binding are all charged residues. ► Favorable hydrophobic contribution from M239 is significant for complex formation.

Displacement chromatography is a separation technique with high capacity and high resolving power. Mass transfer kinetics is an essential factor that determines the separation efficiency of displacement chromatography, but few studies have been reported on the kinetics of the displacement process, especially at the particle level. In this work, the kinetics of protein and displacer adsorptions, protein displacement and adsorbent regeneration in hydrophobic charge induction displacement chromatography were studied by both stirred-batch experiments and online visualization with confocal laser scanning microscopy (CLSM). Stirred-batch experiments showed that small-molecule displacers had higher effective diffusivities and mass transfer rates than proteins. For the displacement systems used in this work, the rate of displacement was dependent on the mass transfer and adsorption rate of the displacer. Direct visualization of the displacement process was achieved by labeling the protein with fluorescein isothiocyanate (FITC) and by using a fluorescent displacer, rhodamine 6G. The concentration profiles obtained by CLSM clearly revealed the higher intraparticle mass transfer rate of the displacer and subsequent high rate of displacement. The observations by CLSM were mostly consistent with the results of the stirred-batch processes. However, although the direct visualizations by CLSM has provided valuable information of the microscopic processes in hydrophobic charge induction displacement chromatography, efforts are still needed to develop an improved displacement model system (protein and displacer) that can provide more accurate and quantitative information of displacement processes.Graphical abstractHighlights► Microscopic process of HCIDC was examined by multiple techniques. ► Consistent results were observed in stirred-batch experiment and CLSM observation. ► Valuable information has been provided for the inherent mechanisms of HCIDC.