Mengfan Wang

Rational Design of Chiral Nanostructures from Self-Assembly of a Ferrocene-Modified Dipeptide

We report a new paradigm for the rational design of chiral nanostructures that is based on the hierarchical self-assembly of a ferrocene (Fc)-modified dipeptide, ferrocene-L-Phe-L-Phe-OH (Fc-FF). Compared to other chiral self-assembling systems, Fc-FF is unique because of its smaller size, biocompatibility, multiple functions (a redox center), and environmental responsiveness. X-ray and spectroscopic analyses showed that the incorporation of counterions during the hierarchical self-assembly of Fc-FF changed the conformations of the secondary structures from flat β sheets into twisted β sheets. This approach enables chiral self-assembly and the formation of well-defined chiral nanostructures composed of helical twisted β sheets. We identified two elementary forms for the helical twist of the β sheets, which allowed us to create a rich variety of rigid chiral nanostructures over a wide range of scales. Furthermore, through subtle modulations in the counterions, temperature, and solvent, we are able to precisely control the helical pitch, diameter, and handedness of the self-assembled chiral nanostructures. This unprecedented level of control not only offers insights into how rationally designed chiral nanostructures can be formed from simple molecular building blocks but also is of significant practical value for the use in chiroptics, templates, chiral sensing, and separations.

Porous-CLEAs of papain: application to enzymatic hydrolysis of macromolecules.

Porous cross-linked enzyme aggregates (p-CLEAs) were prepared by adding starch as a pore-making agent, which facilitates CLEAs in cases where the substrates of enzyme are macromolecules. This novel strategy for preparation of p-CLEAs involves co-precipitation, cross-linking and removal of starch by α-amylase. The resulting papain p-CLEAs were characterized by scanning electron microscope (SEM) images, showing a porous structure. The 95.9% and 90.4% increased catalytic efficiencies of p-CLEAs than conventional CLEAs on bovine serum albumin (BSA) and ovalbumin verified the feasibility of this protocol.

Synthesis of silver nanoparticles within cross-linked lysozyme crystals as recyclable catalysts for 4-nitrophenol reduction

For the first time, we demonstrated the fabrication of silver nanoparticles (NPs) in cross-linked protein crystal hybrid material with catalytic properties using a facile chemical reduction method. The macroscopic porous lysozyme crystals can be used as excellent templates for the incorporation of Ag nanoparticles. The resulting AgNP-in-lysozyme crystal composites exhibited a good catalytic activity toward nitrophenol reduction. Notably, these catalysts could be easily recovered and reused for at least five successive cycles with almost constant activity and conversion efficiency.

Preparation of β-mannanase CLEAs using macromolecular cross-linkers

Cross-linked enzyme aggregates (CLEAs) of β-mannanase were prepared by precipitation and subsequent cross-linking. The macromolecular cross-linkers (dialdehyde starch and dextran polyaldehyde) with different molecular weight were developed instead of traditional glutaraldehyde so as to improve the activity of CLEAs toward macromolecular substrates. Scanning electron microscopy revealed that CLEAs prepared using linear dextran polyaldehyde (MW = 2000 kDa) presented a porous structure with low steric hindrance, and thus exhibited excellent activity toward macromolecular substrates, which was 16 times higher than that prepared using glutaraldehyde.

Enhancement of activity of cross-linked enzyme aggregates by a sugar-assisted precipitation strategy: technical development and molecular mechanism.

The precipitation of enzyme causes the major activity loss in the conventional protocol for CLEAs preparation. Herein, a sugar-assisted strategy was developed to minimize the activity loss in the step of enzyme precipitation by adding sugar as the stabilizer, which contributed to improve the activity yield of resulting CLEAs. Penicillin G acylase (PGA) was employed as a model enzyme. The effects of glucose, sucrose and trehalose on the activity yields of CLEAs were investigated. The highest activity was obtained in the case of adding trehalose. Confocal laser scanning microscopy and Fourier transform infrared spectroscopy showed that the polar microenvironment and the secondary structure of native enzyme were preserved to some extent when PGA was prepared as sugar-assisted CLEAs, resulting in PGAs higher activity than sugar-free CLEAs. Scanning electron microscope revealed the different inner morphologies, and the kinetic studies showed the higher affinity and resist-inhibition capacity of sugar-assisted CLEAs. Furthermore, stability experiments demonstrated that CLEAs prepared in sugar-assisted strategy remained higher thermal stability when it was incubated at high temperature.

Optimization and Application of Reflective LSPR Optical Fiber Biosensors Based on Silver Nanoparticles

In this study, we developed a reflective localized surface plasmon resonance (LSPR) optical fiber sensor, based on silver nanoparticles (Ag NPs). To enhance the sensitivity of the LSPR optical sensor, two key parameters were optimized, the length of the sensing area and the coating time of the Ag NPs. A sensing length of 1.5 cm and a 1-h coating time proved to be suitable conditions to produce highly sensitive sensors for biosensing. The optimized sensor has a high refractive index sensitivity of 387 nm/RIU, which is much higher than that of other reported individual silver nanoparticles in solutions. Moreover, the sensor was further modified with antigen to act as a biosensor. Distinctive wavelength shifts were found after each surface modification step. In addition, the reflective LSPR optical fiber sensor has high reproducibility and stability.

Capillary Force‐Driven, Hierarchical Co‐Assembly of Dandelion‐Like Peptide Microstructures

The wetting and drying of drops on flexible fibers occurs ubiquitously in nature, and the capillary force underlying this phenomenon has motivated our great interest in learning how to direct supramolecular self-assembly. Here, the hierarchical co-assembly of two aromatic peptides, diphenylalanine (FF) and ferrocene-diphenylalanine (Fc-FF), is reported via sequential, combinatorial assembly. The resulting dandelion-like microstructures have highly complex architectures, where FF microtube arrays serve as the scapes and the Fc-FF nanofibers serve as the flower heads. Homogeneous FF microtubes with diameters tailored between 1 and 9 μm and wall thickness ranging from 70 to 950 nm are initially formed by controlling the degree of supersaturation of the FF and the water content. Once the FF microtubes are formed, the growth of the dandelion-like microstructures is then driven by the capillary force, derived from the wetting and drying of the Fc-FF solution on the FF microtubes. This simple and ingenious strategy offers many opportunities to develop new and creative methods for controlling the hierarchical self-assembly of peptides and thus building highly complex nano and microstructures.

Enhancing the Activity of Peptide-Based Artificial Hydrolase with Catalytic Ser/His/Asp Triad and Molecular Imprinting

In this study, an artificial hydrolase was developed by combining the catalytic Ser/His/Asp triad with N-fluorenylmethoxycarbonyl diphenylalanine (Fmoc-FF), followed by coassembly of the peptides into nanofibers (CoA-HSD). The peptide-based nanofibers provide an ideal supramolecular framework to support the functional groups. Compared with the self-assembled catalytic nanofibers (SA-H), which contain only the catalytic histidine residue, the highest activity of CoA-HSD occurs when histidine, serine, and aspartate residues are at a ratio of 40:1:1. This indicates that the well-ordered nanofiber structure and the synergistic effects of serine and aspartate residues contribute to the enhancement in activity. Additionally, for the first time, molecular imprinting was applied to further enhance the activity of the peptide-based artificial enzyme (CoA-HSD). p-NPA was used as the molecular template to arrange the catalytic Ser/His/Asp triad residues in the proper orientation. As a result, the activity of imprinted coassembled CoA-HSD nanofibers is 7.86 times greater than that of nonimprinted CoA-HSD and 13.48 times that of SA-H.

Physicochemical Strategies for Inhibition of Amyloid Fibril Formation: An Overview of Recent Advances

Protein aggregation and amyloid fibrillation can lead to several serious human diseases and protein drug ineffectiveness. The complexity and dynamics of protein folding present unique challenges for elucidating the molecular mechanisms involved in protein aggregation and designing effective amyloid inhibitors. Continuous development of creative approaches to identify an ultimate solution for controlling protein aggregation in biopharmaceuticals and clinical pathology is clearly required. This review describes and discusses the most recent advances on the physicochemical strategies for inhibiting protein aggregation and amyloid fibrillation, with emphasis on giving a brief overview of creative approaches and chemistries used. Physical strategies for inhibiting amyloid fibril formation, including high hydrostatic pressure, low temperature, and laser irradiation, are critically evaluated. Recent advances in chemical strategies including small molecules, metal chelators, and nanomaterials, as well as in the use of biomolecules (peptide, protein, nucleic acid, and saccharide) as amyloid inhibitors, are also highlighted.

Cinnamyl acetate synthesis by lipase-catalyzed transesterification in a solvent-free system.

Cinnamyl acetate was synthesized using immobilized lipase through transesterification between ethyl acetate and cinnamyl alcohol. In the solvent‐free system, ethyl acetate acted as not only the acyl donor but also as the solvent of cinnamyl alcohol. Conversion (90.06%) was achieved after 3 H when transesterification was carried out at ethyl acetate/cinnamyl alcohol 15:1, 2.67 g L of lipase (Novozym 435) loading, and 40°C. Excellent stability and reusability of the enzyme resulted from the moderate reaction system. Kinetic studies showed that the Michaelis constants for ethyl acetate and cinnamyl alcohol and the inhibition constant of cinnamyl alcohol were 2.241, 206.82, and 0.461 mmol L−1, respectively, which indicated that the reaction complied with the Ping–Pong Bi–Bi mechanism, with the inhibition of cinnamyl alcohol on lipase.