Metal Ion Coordination Interactions Research Articles

Construction of multiple crosslinked networks for the preparation of high-performance lignin-containing cellulose nanofiber reinforced polyvinyl alcohol films

Polyvinyl alcohol (PVA) film, a promising alternative to non-biodegradable plastic packaging films for food and medical packaging, is limited by poor water resistance. In this work, a simple solvent evaporation self-assembly was used to construct a nanophase separation structure to establish dense interfacial hydrogen bonding, covalent bonding and iron metal ion coordination interactions between lignin-containing cellulose nanofibers (LCNFs) and PVA matrix to improve the interfacial force and solve the problem of poor compatibility of LCNFs in PVA. The iron ion (Fe3+) coordination tended to combine with the more active lignin phenolic hydroxyl group to construct the nanophase separation structure. Covalent crosslinking of glutaraldehyde (GA) improved the interfacial compatibility of PVA/LCNF films, enhanced the interfacial bonding and formed a homogeneous structure. The multi-nanophase structures improved the strength and elastic modulus of the PVA/LCNF film and provided the films with extremely low water absorption, water vapor transmission rate and excellent UV-shielding. Compared with pure PVA film, PVA-10L-5Fe-3GA film had about 106.9 % higher tensile strength, 93.9 % lower water absorption and 93.4 % lower mass loss, 69.8 % lower water vapor transmission coefficient, and was able to shield UV at 200–400 nm, which is highly expected to be used in packaging films.

The Ribosome-Binding Mode of Trichothecene Mycotoxins Rationalizes Their Structure-Activity Relationships.

Trichothecenes are the most prevalent mycotoxins contaminating cereal grains. Some of them are also considered as the virulence factors of Fusarium head blight disease. However, the mechanism behind the structure-activity relationship for trichothecenes remains unexplained. Filling this information gap is a crucial step for developing strategies to manage this large family of mycotoxins in food and feed. Here, we perform an in-depth re-examination of the existing structures of Saccharomyces cerevisiae ribosome complexed with three different trichothecenes. Multiple binding interactions between trichothecenes and 25S rRNA, including hydrogen bonds, nonpolar pi stacking interactions and metal ion coordination interactions, are identified as important binding determinants. These interactions are mainly contributed by the key structural elements to the toxicity of trichothecenes, including the oxygen in the 12,13-epoxide ring and a double bond between C9 and C10. In addition, the C3-OH group also participates in binding. The comparison of three trichothecenes binding to the ribosome, along with their binding pocket architecture, suggests that the substitutions at different positions impact trichothecenes binding in two different patterns. Moreover, the binding of trichothecenes induced conformation changes of several nucleotide bases in 25S rRNA. This then provides a structural framework for understanding the structure-activity relationships apparent in trichothecenes. This study will facilitate the development of strategies aimed at detoxifying mycotoxins in food and feed and at improving the resistance of cereal crops to Fusarium fungal diseases.

Protein depletion with bacterial cellulose nanofibers

In this study, we have reported a novel fabrication technique for human serum albumin (HSA) imprinted composite bacterial cellulose nanofibers (MIP-cBCNFs) used for the depletion of HSA selectively from artificial blood plasma for proteomic applications. Molecular imprinting was achieved by using metal ion coordination interactions of N‑methacryloyl‑(l)‑histidinemethylester (MAH) monomer and Cu(II) ions. MAH-Cu(II)-HSA complex was polymerized with bacterial cellulose nanofibers (BCNFs) under constant stirring at room temperature. The characterization of the MIP-cBCNFs was carried out by FTIR-ATR, SEM, contact angle measurements and surface area measurements. The adsorption experiments of HSA onto the MIP-BCNFs and NIP-BCNFs from aqueous HSA solutions were investigated in a batch system. The selectivity of the MIP-cBCNFs was investigated by using non-template human transferrin (HTR), and myoglobin (Myo). The relative selectivity coefficients of the MIP-cBCNFs were calculated as 4.73 and 3.02 for HSA/HTR and HSA/Myo molecules, respectively. In addition, the depletion of HSA from artificial human plasma was confirmed by SDS-PAGE and 2-D gel electrophoresis. As a result, it has been shown that metal ion coordination interactions contribute to specific binding of template when preparing MIP-cBCNFs for the depletion of HSA with a high adsorption capacity, significant selectivity and reusability.

Controlled release of mitomycin C from PHEMAH–Cu(II) cryogel membranes

Molecular imprinting technique was used for the preparation of antibiotic and anti-neoplastic chemotherapy drug (mitomycin C) imprinted cryogel membranes (MMC-ICM). The membranes were synthezied by using metal ion coordination interactions with N-methacryloyl-(l)-histidine methyl ester (MAH) functional monomer and template molecules (i.e. MMC). The 2-hydroxyethyl methacrylate (HEMA) monomer and methylene bisacrylamide (MBAAm) crosslinker were used for the preparation of mitomycin C imprinted cryogel membranes by radical suspension polymerization technique. The imprinted cryogel membranes were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and swelling degree measurements. Cytotoxicity of MMC-ICMs was investigated using mouse fibroblast cell line L929. Time-dependent release of MMC was demonstrated within 150 h from cryogel membranes. Cryogels demonstrated very high MMC loading efficiency (70–80%) and sustained MMC release over hours.

Surface imprinted bacterial cellulose nanofibers for hemoglobin purification

There is a significant need for the development of the novel adsorbents in the field of protein purification. In this study, thin hemoglobin imprinted film (MIP) was fabricated onto the bacterial cellulose nanofibers’ (BCNFs) by surface imprinting method using metal ion coordination interactions with N-methacryloyl–(L)-histidinemethylester (MAH) and copper ions. The hemoglobin surface imprinted bacterial cellulose nanofibers (MIP-BCNFs) was applied to selective recognition of hemoglobin and purification from hemolysate. The characterization of the MIP-BCNFs was carried out by the Fourier Transformed Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), micro-Computerized Tomography (μCT), atomic force microscopy (AFM) and surface area measurements. The adsorption experiments of hemoglobin onto the MIP-BCNFs and NIP-BCNFs from aqueous hemoglobin solutions were investigated in a batch system. The results showed that MIP-BCNFs are promising materials for purification of hemoglobin with high adsorption capacity, significant selectivity and reusability.

Affinity binding of proteins to the modified bacterial cellulose nanofibers.

The potential of the modified bacterial cellulose (BC) nanofibers was determined bearing metal ion coordination interactions to enhance the protein adsorption and binding capacity. Thus, a household synthesized metal chelating monomer, namely N-methacryloyl-l-histidine methylester (MAH), and a commercial metal chelating monomer, namely 4-vinylimidazole (VIm), were used to complex with metal ions Cu(II) and Ni(II) respectively for the synthesis of the modified BC nanofibers. The modified nanofibers were characterized by FT-IR, SEM and EDX measurements. The protein adsorption tests were carried out using hemoglobin as a model protein and it was determined that the maximum adsorption capacity of hemoglobin onto the modified BC nanofibers was found as 47.40mg/g. The novel strategy for the preparation of metal chelated nanofibers was developed.

Surface imprinted bacterial cellulose nanofibers for cytochrome c purification

Molecularly imprinted polymers possessing synthetic recognition sites present great potential for various application areas, which require specific recognition of molecules. However various molecularly imprinted polymers (MIPs) reported previously have low affinity capacity and low binding kinetics due to weak interactions between template molecule and functional monomer in aqueous media and also high mass transfer resistance. The synthesis of MIPs onto nanomaterial surface via metal ion coordination interactions serves as an effective solution. In this work, we prepared thin molecularly imprinted polymer layer on bacterial cellulose nanofiber surface using Cu2+ chelating monomer, N-Methacryloyl-(L)-histidinemethylester (MAH) as a functional monomer orienting cytochrome c molecules. The conditions of polymerization and adsorption were optimized to obtain best affinity performance. Due to unique properties of bacterial cellulose nanofibers such as high surface-to-volume ratio and macro-porosity, the resultant cytochrome c imprinted nanofibers (Cyt c-MIP NFs) reducing diffusional resistances could achieve high recognition capacity and excellent binding kinetics. Cyt c-MIP NFs were also successfully applied to capture template proteins from real sample. This novel procedure presents simple, cheap and stable fabrication strategy for efficient separation of proteins.

Metal ion coordination interactions for biomolecule recognition: a review

Molecular imprinting is an effective method to create selective binding sites in polymeric matrices for biomolecule recognition. This review gives recent improvements of the design and preparation of selective binding sites via metal coordination interactions in molecularly imprinted polymers (MIPs) and focuses on particularly metal coordination bonds between biomolecules such as amino acids, peptides, proteins and templated polymers. The discussion will evaluate key parameters for molecular imprinting in the perspective of metal coordination. Keywords: Metal ion coordination; Molecular imprinting; Metal chelation; Biomolecule recognition DOI: 10.17350/HJSE19030000004 Full Text: