Molecular Cutoff Research Articles

Process optimization and identification of antioxidant peptides from enzymatic hydrolysate of bovine bone extract, a potential source in cultured meat

Bone protein is a significant secondary product of the meat industry, comprising a substantial quantity of protein. These proteins could be broken down through enzymatic hydrolysis to generate antioxidant peptides. This study aimed to produce antioxidant peptides from bovine bone extract by enzymatic hydrolysis utilizing Flavourzyme and Protamex by optimizing enzyme amounts and time using the Box–Behnken design. The final optimized conditions obtained through the model were as follows: The amount of Flavourzyme was 1,100 U, the amount of Protamex was 2,814 U, and the time was 3.77 (h). Bovine bone extract hydrolysate (BBEH) was purified stepwise using ultrafiltration membranes with molecular cutoffs of 5, 3, and 1 kDa. To assess the antioxidant capacity of the fractions, several methods were used, including radical scavenging activity “1,1-diphenyl-2-picrylhydrazyl (DPPH),” “2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS),” metal chelating activity (MCA), reducing power (RP), and thiobarbituric acid assay (TBA). The results indicated that the ultrafiltration fraction with a molecular weight of less than 1 kDa showed significant antioxidant activity, with 48, 42, and 50% inhibition rates for DPPH, ABTS, and metal chelating, respectively. Using size exclusion chromatography, the fraction with a molecular weight less than 1 kDa was further separated into five sub-fractions: Frac-I, Frac-II, Frac-III, Frac-IV, and Frac-V. Sub-Frac-III, which exhibits significant DPPH radical scavenging activity (55%) and a reducing power of 0.8 at 700 nm, was separated into six sub-sub-fractions using reversed-phase HPLC (RP-HPLC) based on molecular weight and hydrophobicity. The sub-sub-fraction with the highest value for DPPH radical scavenging activity was sub-Fra-III-6, which exhibited approximately 69.45% activity. The sub-Fra-III-6 was analyzed using LC–MS/MS, which identified two specific peptides: Ala-Pro-Phe with a mass of 333.12 Da and Asp-His-Val with a mass of 369.14 Da. These two peptides are likely the primary peptides that might have a crucial role in antioxidant capacity. It can be concluded that BBEH is a valuable source of natural antioxidants and has the potential to serve as a viable resource in the cultured meat industry.

Unraveling the relationship between molecular properties and rapid diffusion in smooth nanopores

Synthetic materials designed to enable rapid and finely tuned diffusion through semi-permeable nano and microscale pores have generally fallen short when compared to their biological counterparts. As a result, applications such as hemodialysis, drug delivery, and biomolecule purifications often require extensive run times and produce imperfect permeate solutions. Towards bridging this gap, we have recently demonstrated that, under a concentration gradient, a wide range of ions diffuse through atomically smooth carbon nanotube pores at rates more than an order of magnitude above those seen in bulk. This observation comes in a pore/molecule size regime where hindered diffusion was previously thought to apply. Here, we extend these results to include more complex and biologically relevant molecules and study how transport rates driven by diffusion depend on molecular properties such as size and flexibility. Further, we work to understand how the unique nanofluidic phenomena occurring in our pores may enable improved performance in dialysis applications by impacting selectivity, permeability, and molecular cutoff profiles. These results help to shed light on mechanisms governing diffusive transport in certain nanoscale pores that remain only partially understood and bring us closer to harnessing them in future separation technologies.

Zingiber officinale mediated aflatoxins cleanup in aqueous medium: Kinetics, toxicity and cytoprotective effect

Aflatoxins contaminate a variety of food and feeds and have a serious health concern to humans and animals. The present work investigated the effect of Zingiber officinale (ginger) for the reduction of aflatoxin B1, G1, B2, and G2. Ginger juice reduced 70.2 ± 0.1%, 99.76 ± 0.0%, 56.8 ± 0.5%, and 98.6 ± 0.0% of aflatoxin B1, G1, B2, and G2, respectively. The ginger-mediated aflatoxin reduction conditions were optimized and the most convincing results were observed at 45 °C and 55 °C where almost 100% reduction of aflatoxins was observed. The aflatoxin reduction efficiency of ginger juice was significantly declined after dialysis (12,000–14,000 Da molecular cutoff) and heating. The degraded products were analyzed by liquid chromatography–mass spectroscopy and revealed the vulnerability of furan and lactone rings of aflatoxin towards the components of ginger. Furthermore, the degraded products showed a slightly reduced toxicity towards embryos of zebrafish compared to the aflatoxins. Ginger exhibited cytoprotection against aflatoxin B1-induced toxicity in HaCaT cells by blocking DNA fragmentation, apoptotic cell death, and reactive oxygen species generation. Also, ginger upregulated the cellular antioxidant markers, catalase, glutathione reductase, superoxide dismutase-1 (SOD-1), and superoxide dismutase-2 (SOD-2) thus balancing the redox status and rescuing cells from aflatoxin B1 induced stress.

Gas Separation Membranes with Atom-Thick Nanopores: The Potential of Nanoporous Single-Layer Graphene.

Gas separation is one of the most important industrial processes and is poised to take a larger role in the transition to renewable energy, e.g., carbon capture and hydrogen purification. Conventional gas separation processes involving cryogenic distillation, solvents, and sorbents are energy intensive, and as a result, the energy footprint of gas separations in the chemical industry is extraordinarily high. This has motivated fundamental research toward the development of novel materials for high-performance membranes to improve the energy efficiency of gas separation. These novel materials are expected to overcome the intrinsic limitations of the conventional membrane material, i.e., polymers, where a longstanding trade-off between the separation selectivity and the permeance has motivated research into nanoporous materials as the selective layer for the membranes. In this context, atom-thick materials such as nanoporous single-layer graphene constitute the ultimate limit for the selective layer. Gas transport from atom-thick nanopores is extremely fast, dependent primarily on the energy barrier that the gas molecule experiences in translocating the nanopore. Consequently, the difference in the energy barriers for two gas molecules determines the gas pair selectivity. In this Account, we summarize the development in the field of nanoporous single-layer graphene membranes for gas separation. We start by discussing the mechanism for gas transport across atom-thick nanopores, which then yields the crucial design elements needed to achieve high-performance membranes: (i) nanopores with an adequate electron-density gap to sieve the desired gas component (e.g., smaller than 0.289, 0.33, 0.346, 0.362, and 0.38 nm for H2, CO2, O2, N2, and CH4, respectively), (ii) narrow pore size distribution to limit the nonselective effusive transport from the tail end of the distribution, and (iii) high density of selective pores. We discuss and compare the state-of-the-art bottom-up and top-down routes for the synthesis of nanoporous graphene films. Mechanistic insights and parameters controlling the size, distribution, and density of nanopores are discussed. Fundamental insights are provided into the reaction of ozone with graphene, which has been successfully used by our group to develop membranes with record-high carbon capture performance. Postsynthetic modifications, which allow the tuning of the transport by (i) tailoring the relative contributions of adsorbed-phase and gas-phase transport, (ii) competitive adsorption, and (iii) molecular cutoff adjustment, are discussed. Finally, we discuss practical aspects that are crucial in successfully preparing practical membranes using atom-thick materials as the selective layer, allowing the eventual scale-up of these membranes. Crack- and tear-free preparation of membranes is discussed using the approach of mechanical reinforcement of graphene with nanoporous carbon and polymers, which led to the first reports of millimeter- and centimeter-scale gas-sieving membranes in the year 2018 and 2021, respectively. We conclude with insights and perspectives highlighting the key scientific and technological gaps that must be addressed in the future research.

Exploitation of Amine Groups Cooped up in Polyamide Nanofiltration Membranes to Achieve High Rejection of Micropollutants and High Permeance of Divalent Cations.

To enhance the use of nanofiltration in the production of quality drinking water, particularly through the efficient removal of micropollutants yet still preserving essential minerals, the targeted nanofiltration membranes (NFMs) are required to have small pore dimensions coupled with a high, net-negative charge density. Herein, after the formation of a separation layer using piperazine interfacially polymerized with trimesoyl chloride, the exploitation of residual amine groups was systematically investigated by different diacyl chlorides in an organic milieu, which caused the upper part of the final separation layer to be denser and highly negatively charged. Hence, this protocol offers a novel means to fabricate NFMs simultaneously endowed with a low molecular cutoff (MWCO) of 145-238 Da and a reduced rejection of MgCl2 (48%-80%) as well as a competitive water permeance. Those features are ideally applicable to the goal of removing small micropollutants while preserving mineral ions, as needed for the energy-efficient production of safe, quality drinking water. Furthermore, an attempt was made to correlate MWCO with MgCl2 rejection, which provides some insights on the nexus of the electrostatic effects constrained by size exclusion. The significance of residual amine groups and the modification environment was unveiled, and this method paves a new avenue for designing functional NFMs.

Design of carbon–ceramic composite membranes with tunable molecular cut-offs from a carboxylic benzoxazine ligand chelated to silica–zirconia

This study presents a concept that focuses on the structure design of preceramic resin precursors by the sol–gel method for fabricating carbon–ceramic molecular sieving membranes.

High harmonic generation in fullerene molecules

Using dynamical Hartree-Fock mean-field theory, we study the high harmonic generation (HHG) in the fullerene molecules ${\mathrm{C}}_{60}$ and ${\mathrm{C}}_{70}$ under strong pump wave driving. We consider a strong-field regime and show that the output harmonic radiation exhibits multiple plateaus, whose borders are defined by the molecular excitonic lines and cutoff energies within each plateau scale linearly with the field strength amplitude. In contrast to atomic cases for the fullerene molecule, with the increase of the pump wave photon energy the cutoff harmonic energy is increased. We also show that with the increase of the electron-electron interaction energy overall the HHG rate is suppressed. We demonstrate that the ${\mathrm{C}}_{70}$ molecule shows richer HHG spectra and a stronger high harmonic intensity than the ${\mathrm{C}}_{60}$.

Mechanistic Study on Thermally Induced Lattice Stiffening of ZIF-8.

The flexibility of the ZIF-8 aperture, which inhibits a molecular cutoff of 3.4 Å, can be reduced by rapid heat treatment to obtain CO2-selective membranes. However, the early stages of the structural, morphological, and chemical changes responsible for the lattice rigidification remain elusive. Herein, using ex situ and in situ experiments, we determine that a small shrinkage of the unit-cell parameter, ∼0.2%, is mainly responsible for this transformation. Systematic gas permeation studies show that one needs to achieve this shrinkage without a disproportionately large shrinkage in the grain size of the polycrystalline film to avoid the formation of cracks. We show that this condition is uniquely achieved in a short time by exposure of ZIF-8 to a mildly humid environment where lattice parameter shrinkage is accelerated by the incorporation of linker vacancy defects, while the shrinkage in grain size is limited. The water-vapor-led incorporation of linker vacancy defects takes place with an energy barrier of 123 kJ mol–1, much higher than that for the thermal degradation of ZIF-8, <80 kJ mol–1. The latter is promoted by heat treatment in a dry environment at a relatively higher temperature; however, this condition does not shrink the lattice parameters at short exposure time.

Sweet chestnut standardized fractions from sustainable circular process and green tea extract: In vitro inhibitory activity against phytopathogenic fungi for innovative applications in green agriculture.

In the present study, the antifungal activities of two commercial tannins-rich dry fractions towards different filamentous fungi of agronomical and food interest were evaluated. In particular, a standardized fraction from sweet chestnut (Castanea sativa Mill.) wood by-products and a commercial green tea (Camellia sinensis L.) leaf extract were tested at different concentrations (0.1-5.0% and 0.2% w/v respectively). The Sweet Chestnut Wood fraction was produced in an industrial plant through an environmentally and economically sustainable process, involving hot-water extraction and a sequence of membrane filtration steps with different molecular cut-offs for fractionation and concentration of the active principles. The Sweet Chestnut Wood and Green Tea Leaf extracts were characterised via HPLC/DAD/MS quali-quantitative analysis. The first extract showed a polyphenolic content of 20.5% w/w, 100% hydrolysable tannins; the second one showed a polyphenolic content of 87.5% w/w, of which 96.2% epigallocatechin gallate and 3.8% epicatechin gallate. The antifungal activity of the Sweet Chestnut fraction in aqueous solutions was evaluated towards different filamentous fungi, in particular telluric phytopathogens (Fusarium oxysporum f. sp. radicis-lycopersici; Fusarium solani; Rhizoctonia solani; Sclerotium rolfsii) and post harvest pathogens (Botrytis cinerea, that can also attack field plants; Penicillium digitatum; Penicillium italicum), and compared to the activity of Green Tea Leaf extract solutions. The experimental results evidenced, for almost all tested fungi, inhibition of the mycelial growth rate in presence of tannins. The lowest inhibitions were observed for B. cinerea (7.5%, to 28.9%) and P. italicum (53.8% in 5.0% w/v Sweet Chestnut extract substrate). A proportional inhibitory effect to tannin concentration was observed for F. oxysporum f. sp. radicis-lycopersici and F. solani (from 33.7% to 56.6%), R. solani (from 29.7% to 68.8%) and P. digitatum (64.7% to 87.0%). The highest effect resulted for S. rolfsii, (5.0% to 100%).

Gas-sieving zeolitic membranes fabricated by condensation of precursor nanosheets.

The synthesis of molecular-sieving zeolitic membranes by the assembly of building blocks, avoiding the hydrothermal treatment, is highly desired to improve reproducibility and scalability. Here we report exfoliation of the sodalite precursor RUB-15 into crystalline 0.8-nm-thick nanosheets, that host hydrogen-sieving six-membered rings (6-MRs) of SiO4 tetrahedra. Thin films, fabricated by the filtration of a suspension of exfoliated nanosheets, possess two transport pathways: 6-MR apertures and intersheet gaps. The latter were found to dominate the gas transport and yielded a molecular cutoff of 3.6 Å with a H2/N2 selectivity above 20. The gaps were successfully removed by the condensation of the terminal silanol groups of RUB-15 to yield H2/CO2 selectivities up to 100. The high selectivity was exclusively from the transport across 6-MR, which was confirmed by a good agreement between the experimentally determined apparent activation energy of H2 and that computed by ab initio calculations. The scalable fabrication and the attractive sieving performance at 250-300 °C make these membranes promising for precombustion carbon capture.

MALDI-TOF analysis of a novel extremophile peptide purified from Halarchaeum acidiphilum ASDL78 with antiarchaeal and antibacterial activities.

In hypersaline environments, halophilic archaea synthesize antimicrobial substances called halocins. There is a promise to make new drugs for antibiotic-resistant strains. Here, we report the antibacterial activity of a new haloarchaea selected from Lut Desert, Iran. A total of 38 isolated halophilic bacteria and archaea were screened for the antagonistic activity test of each strain against other bacterial and archaeal strains. Finally, a strain, recognized as Halarchaeum acidiphilum, with a fast grown strain and high antagonistic potential against different strains was identified by morphological, physiological, and molecular characteristics. The halocin was produced in a semisolid submerge medium and partially purified by heat treatments and molecular weight ultrafiltration cutoff (3, 50, and 10 kDa). It was a cell-free, heat-resistant (85°C for 2 h) protein with a molecular mass near to 20 kDa produced at the endpoint of logarithmic growth. The molecular weight of halocin was 17 kDa, and indicated no apparent homology with known halocins, suggesting that this might be a new halocin. Therefore, a new strain belonging to Halarchaeum genus was isolated and characterized here that produced an antimicrobial and anti-haloarchaea halocin.

Self-standing permselective CMS membrane from melt extruded PVDC

All previous polyvinylidene chloride (PVDC) carbon molecular sieve (CMS) membranes reported in the literature have been in supported form. Those CMS membranes have large non-selective molecular cutoff pores. We have made self-standing PVDC CMS membrane for the first time using a facile melt extrusion-pyrolysis process. Unlike the supported membranes, the new CMS membranes are very selective for CO2/CH4 and C2H4/C2H6 separations. The new PVDC CMS membranes have about 46% larger micropore volume and 54% higher Young's modulus than those derived from Matrimid® polyimide. The 45 μm thick PVDC CMS membrane has 6–20 times higher H2 and CO2 permeance than Matrimid® CMS membranes of similar thickness. The new membranes also showed stable separation performance after storage under nitrogen for one month.

Single-layer BSA-NH&lt;sub&gt;2&lt;/sub&gt;/PNIPAAm membrane with modulated lipase biocatalytic reaction

Biocatalysis, utilizing enzymes or live microbial cultures to catalyze or speed up specific or cascade reactions, has broad applications in the manufacturing of fine chemicals, pharmaceuticals, and agrochemical intermediates. However, how to effectively adjust the biocatalytic process and the dose of enzymes during the reaction becomes one intriguing issue to be addressed. Smart porous membranes are desirable candidates for regulating substance permeability, which provides the possibility to adjust the biocatalysis. Herein, inspired by the temperature-sensitive stomatal size of plant leaves, we prepare a free-standing single-layer membrane through the self-assembly at oil-water interface, which is composed of thermosensitive amphiphilic protein-polymer conjugates, i.e., BSA-NH2/PNIPAAm (poly(N-isopropylacrylamide)). The membrane thickness is only about 4 nm, with a wide range of molecular cut-offs by tuning the molecular weight of PNIPAAm. Moreover, by virtue of the property of PNIPAAm, the pore size of the membrane could be tunable by changing temperature, through which the catalytic reaction of triglyceride by lipase was successfully controlled. Taken together, this work not only provides a simple method for preparing single-layer protein hybrid membranes, but also offers great potential applications in the controlled biocatalysis, smart gating systems and molecular separation.

Facile Synthesis of Robust and Pore-Size-Tunable Nanoporous Covalent Framework Membrane by Simultaneous Gelation and Phase Separation of Covalent Network/Poly(methyl methacrylate) Mixture.

We report a facile route toward the preparation of organic-solvent-resistant and three-dimensionally continuous nanoporous covalent framework membrane. The membrane was prepared from the blend of linear poly(methyl methacrylate) and the cross-linked polyurea-based organic network, followed by selective removal of the linear polymer part. The pore morphologies, porosity, and solvent permeation properties of the membrane could be simply modified by the initial composition of the poly(methyl methacrylate) added to a sol of the organic network. The pore was three-dimensionally continuous with pore size ranging from 5 nm to tens of nanometers. Despite the broad pore size distribution, ultrafiltration of sub-10 nm solutes was realized with a molecular size cutoff near 5 nm thanks to the bicontinuous pore structure of the membrane. The nanoporous structure exhibited long-term resistance to organic solvents as well as thermal stability and mechanical strength. The separation performance remained unchanged in organic-rich medium for a prolonged time. Our strategy provides a synthetic route to a structurally robust, three-dimensionally continuous nanoporous polymeric membrane for potential application that necessitates the use of organic solvent.

Effect of Anisotropic Aggregates Comprising Pegylated Block Copolymers on Cell Growth and Aggregation

In recent years, effects of shape of nanomaterials on biological response has attracted attention. For example, rod or fibrous polymeric micelles show a longer circulation time in blood and preferential accumulation to tumor cells than a spherical counterpart.1) On the other hand, fibrous cationic molecular assemblies exhibit higher or/and broader spectrum of antimicrobial activity than a spherical counterpart2). In addition, nano/micro-topology of substrates for tissue engineering is now recognized as a tool of regulating cellular responses such as adhesion, extension, aggregation, and differentiation. However, there have not been active systems to control such cellular responses by shape of molecular assemblies. Previously, we have developed amphiphilic pegylated diblock copolymers conjugating poly(L-lactide) (PLLA), poly(e-caprolactone) (PCL), or poly(trimethylene carbonate) (PTMC), forming anisotropic aggregates in water by introduction of a supramolecular assembling motif in the block junction. The size and length of the anisotropic aggregates are varied depending on the type of polymer used in hydrophobic segments. In this context, we explore cell culture of normal human dermal fibroblasts (NHDFs) in the presence of these anisotropic rod/fiber-like aggregates to evaluate the effect of shape of aggregates in culture media on cellular responses. The polymer aggregates were formulated by membrane dialysis. Typically, the block copolymer (40 mg) was dissolved in DMF (1 mL) and stirred overnight at room temperature. Nile red (NR) as a fluorescent probe was dissolved in DMF to have the concentration of 0.02 mg/mL. Then, the DMF solution of NR (1 mL) was added to the block copolymer solution and stirred for 2 hours. After that, the solution was transferred to a dialysis tube (Spectra/Por®7 Dialysis Membrane) with molecular cut off (MWCO) of 2,000 and dialyzed against ultrapure water for two days. Finally, the suspension was diluted to have the polymer concentration of 10 mg/mL (1.0 wt%) NHDFs were seeded on poly(ethylene terephthalate) (PET) plates embedded in a 24-well polystyrene plate at a cell density of 0.5 × 104 cells/cm2 in a cell culture medium (950 µL). The polymer suspension (50 µL) was then added to adjust the final polymer concentration to 0.05 wt%. The cells were incubated at 37 °C in 5% CO2 for 24 h and 48 h. At a certain time of incubation, cells were washed and stained with phalloidin and DAPI to visualize actin and nuclei in the observation by a confocal laser scanning microscope (CLSM). Furthermore, as three-dimension cell culture, NHDFs were first treated with CellTrackerTM to stain cytoplasm. Then, the cell suspension with a density of 1.6 × 104 cells/well including 0.05 wt% of the polymer aggregates was loaded in PrimeSurface\U0001f12c a round-bottom 96-well plates. The cells were incubated at 37 °C in 5% CO2 for 2, 6, and 12 h. Afterwards, cells were washed, stained with DAPI, and observed on a CLSM and a phase-contrast microscope. References 1)D. Li et al., Adv. Funct. Mater., 2016, 26, 66–79. 2)K.Fukushima et al., ACS Nano, 2012, 6, 9191-9199.

Antioxidant and Ace Inhibitor Potential of Stripe Trevally Fish (Selaroides leptolepis) Hydrolysate

This study aimed to investigate the potency of fish protein hydrolysates (FPH) of stripe trevally fish (Selaroides leptolepis) as antioxidant and ACE inhibitor. The FPH was produced through enzymatically hydrolysis using protease produced by Bacillus licheniformis, a collection of Research and Development Center for Marine and Fisheries Product Processing and Biotechnology (RDCMFPPB). The FPH was fractionated using ultrafiltration membranes with molecular weight cut off (MWCO) of 10, 5 and 3 kDa. The hydrolysis degree, protein content, peptide content, antioxidant activity and Angiotensin-converting enzyme (ACE) inhibitor were observed. The result showed that FPH had maximum hydrolysis degree of 63.91% reached after 6 hours hydrolysis with protein content of 27.43 mg/mL and peptide content of 223.32 mg/mL. That FPH showed antioxidant activity (IC50) of 1941.06 ppm and ACE inhibitor of 87.82% at test concentration of 10 mg/mL. In the ultrafiltration step, the higher molecular cut off used, the higher protein content and peptide content. The lower molecular weight of the hydrolysate, the better antioxidant and ACE inhibitor activity. The best fractionation that produce potential product to be used as anti-hypertension was in mixture peptides between 3-5 kDa. The IC50 antioxidant activity was 1336.96 ppm and percentage of ACE inhibitor was 97.15% % (with a concentration of 10 mg/mL). From the results, protein hydrolysate of stripe trevally fish produced by enzymatic hydrolysis using local protease was potential as a functional ingredient, particularly as antihypertensive agent.

Charge‐assisted ultrafiltration membranes for monovalent ions separation in electrodialysis

ABSTRACTSelectivity for monovalent ions is a very important feature of ion exchange membranes in view of a further expansion of the scope of electrodialysis (ED). An efficient one‐step chemical process to graft a thin polyaniline (PANI) layer on the surface and pores of an ultrafiltration (UF) membrane is reported. The existence of a PANI layer on such modified UF membrane was confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy images. These membranes were extensively characterized by studying their properties such as water uptake, ion‐exchange capacity, contact angle, and performance in diffusion dialysis. ED experiments were conducted by comparing desalting of sodium chloride and magnesium chloride solutions. During the desalting procedure, the driving force has two contributions, the electrical field and the salinity‐gradient. Initially, transport of ions by the electrical field is dominant, while at the end of the experiment, diffusion dialysis by the salinity gradient plays a larger role in ion transport. The presence of PANI can hinder Mg2+ transport from the concentrate to the diluate compartment because of the electrostatic effect, while there is no obvious effect on Na+ ions. The ability of such a surface modification layer to improve the membrane selectivity for Na+/Mg2+ was confirmed by means of ED in a mixed solution. The flux of Na+ was slightly increased to 13.21 × 10−8 mol/L/min while the flux of Mg2+ was reduced to 3.32 × 10−8 mol/L/min, so that the permselectivity is almost doubled. The protonation reaction of the PANI layer creates positive charges, thus leading to an electrical repulsion barrier, which may reduce the penetration of divalent cations with respect to monovalent ions. Polyacrylonitrile‐based UF membranes with different molecular cutoff was used to determine the influence of the permselectivity. Results showed that the membrane permselectivity of smaller molecular cutoff UF membranes is higher. It can be concluded that this method is suitable for preparing membranes based on UF membranes for efficient separation of monovalent ions by electro‐driven separation techniques. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45692.

Sodium persulfate based PVDF membrane for concurrent advanced oxidation and ultrafiltration of ofloxacin in water

Flat Na2S2O8@PVDF-g-PDMAEMA/PVDF inorganic–organic composite membrane was prepared by sequential use of atom transfer radical polymerization (ATRP), non-solvent induced phase inversion separation (NIPS) and post-dipping treatment. The membrane was tested in a membrane chemical reactor (MCR) system for concurrent advanced oxidation and ultrafiltration of ofloxacin (OFLX) under UV irradiation. Results indicated that the production of sulfate radicals (SO4−) from persulfate can achieve 54% removal efficiency of OFLX, outperforming single advanced oxidation processes (AOPs) or ultrafiltration treatment. The best performance, was secondary to the combination of high redox potential of the SO4−, hydrophilicity of N,N-dimethylaminoethyl methacrylate (DMAEMA) and molecular cutoff of polyvinylidene fluoride (PVDF) ultrafiltration membrane. This study also identified factors related to successfully preparing composite membranes with concurrent positive charges and hydrophilicity. Characterization using XRD, FTIR and EDS showed that introducing PDMAEMA into the polymer mixture and post-dipping were both required to obtain a multifunctional membrane, which can electrostatically attract negative S2O82− species. Judging from SEM results, the formation mechanisms of the composite membrane structure were derived from instantaneous liquid–liquid demixing.

N-tuple topological/geometric cutoffs for 3D N-linear algebraic molecular codifications: variability, linear independence and QSAR analysis

Novel N-tuple topological/geometric cutoffs to consider specific inter-atomic relations in the QuBiLS-MIDAS framework are introduced in this manuscript. These molecular cutoffs permit the taking into account of relations between more than two atoms by using (dis-)similarity multi-metrics and the concepts related with topological and Euclidean-geometric distances. To this end, the kth two-, three- and four-tuple topological and geometric neighbourhood quotient (NQ) total (or local-fragment) spatial-(dis)similarity matrices are defined, to represent 3D information corresponding to the relations between two, three and four atoms of the molecular structures that satisfy certain cutoff criteria. First, an analysis of a diverse chemical space for the most common values of topological/Euclidean-geometric distances, bond/dihedral angles, triangle/quadrilateral perimeters, triangle area and volume was performed in order to determine the intervals to take into account in the cutoff procedures. A variability analysis based on Shannon’s entropy reveals that better distribution patterns are attained with the descriptors based on the cutoffs proposed (QuBiLS-MIDAS NQ-MDs) with regard to the results obtained when all inter-atomic relations are considered (QuBiLS-MIDAS KA-MDs – ‘Keep All’). A principal component analysis shows that the novel molecular cutoffs codify chemical information captured by the respective QuBiLS-MIDAS KA-MDs, as well as information not captured by the latter. Lastly, a QSAR study to obtain deeper knowledge of the contribution of the proposed methods was carried out, using four molecular datasets (steroids (STER), angiotensin converting enzyme (ACE), thermolysin inhibitors (THER) and thrombin inhibitors (THR)) widely used as benchmarks in the evaluation of several methodologies. One to four variable QSAR models based on multiple linear regression were developed for each compound dataset following the original division into training and test sets. The results obtained reveal that the novel cutoff procedures yield superior performances relative to those of the QuBiLS-MIDAS KA-MDs in the prediction of the biological activities considered. From the results achieved, it can be suggested that the proposed N-tuple topological/geometric cutoffs constitute a relevant criteria for generating MDs codifying particular atomic relations, ultimately useful in enhancing the modelling capacity of the QuBiLS-MIDAS 3D-MDs.

Synthesis, characterization and antioxidant activity of selenium polysaccharide from Cordyceps militaris

A purified selenium-containing derivatives of Cordyceps militaris polysaccharide synthesized using H2SeO3/HNO3 and BaCl2 as a catalyst was investigated in this paper. The reaction condition was optimized by selecting different reaction temperature and period. Afterward, the one with the highest Se content was purified by ultra-filtration device with a molecular cut off size of 10KDa. Followed by its structural characterizations. Results of IFR and 13C NMR spectroscopy indicated that C-6 substitution was predominant in selenized polysaccharide. The modified polysaccharide with molecular weight of 1998 KDa was mainly consisted of mannose, glucose and galactose in the mole ratios of with the mole ratios of 1:28.63:1.41. Thermogravimetric and morphological analyses of the samples were carried out by AFS, SEM and AFM. In addition, the in vitro antioxidant results suggested that selenium-containing polysaccharide should be applied as a novel selenium source in dietary supplements, with potent antioxidant properties.