Invertase immobilized on spacer‐arm attached poly(hydroxyethyl methacrylate) membrane: Preparation and properties

Microporous poly(2‐hydroxyethyl methacrylate) (pHEMA) membrane was prepared by UV‐initiated photopolymerization. The spacer arm (i.e., hexamethylene diamine) was attached covalently and then invertase was immobilized by the condensation reaction of the amino groups of the spacer arm with carboxyl groups of the enzyme in the presence of carbodiimides. The values of the Michael's constant K_m of invertase were significantly larger (ca. 2.5 times) upon immobilization, indicating decreased affinity by the enzyme for its substrate, whereas V_max was smaller for the immobilized invertase. Immobilization improved the pH stability of the enzyme as well as its temperature stability. Thermal stability was found to increase with immobilization and at 70°C the half times for the activity decay were 12 min for the free enzyme and 41 min for the immobilized enzyme. The immobilized enzyme activity was found to be quite stable in repeated experiments. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1685–1692, 2000     

Biological activity of Boswellia serrata Roxb. oleo gum resin essential oil: effects of extraction by supercritical carbon dioxide and traditional methods

The findings of this study suggests that chemical composition, essential oil yield, antioxidant and antimicrobial activity of Boswellia serrata oleo gum resin essential oils extracted by hydro distillation, steam distillation and supercritical fluid carbon dioxide methods vary greatly from each other. The optimum essential oil yield was obtained using hydro distillation method (8.18 ± 0.15 %). The essential oils isolated through different extraction methods contained remarkable amounts of total phenolics and total flavonoids. Essential oil isolated through supercritical fluid carbon dioxide extraction exhibited better antioxidant activity with highest free radical scavenging potential (96.16 ± 1.57 %), inhibition of linoleic acid oxidation (94.18 ± 1.47 %) and hydrogen peroxide free radical scavenging potential (68.25 ± 1.02 %). Moreover, the antimicrobial activity of essential oils was performed through well diffusion, resazurin microtiter plate and micro dilution broth assay assays. The essential oil isolated through steam distillation method revealed highest antimicrobial activity with maximum inhibition zone (24.21 ± 0.34 to12.08 ± 0.30 mm) and least MIC values (35.18 ± 0.77 to 281.46 ± 7.03 µg/mL). The comparison of chemical composition of essential oils isolated at different extraction methods have shown that the concentration of α-thujene, camphene, β-pinene, myrcene, limonene, m-cymene and cis-verbenol was higher in steam distilled essential oil as compared to hydro and supercritical fluid carbon dioxide extracted essential oils. These compounds may be responsible for the higher antimicrobial activity of Boswellia serrata oleo gum resin steam distilled essential oil.     

In vitro cadmium removal from human serum by Cibacron Blue F3GA–thionein‐complex conjugated affinity membranes

A new membrane affinity biosorbent carrying thionein has been developed for selective removal of cadmium ions from human serum. Microporous poly(2‐hydroxyethyl methacrylate) (pHEMA) membranes were prepared by photopolymerization of HEMA. The pseudo dye ligand Cibacron Blue F3GA (CB) was covalently immobilized on the pHEMA membranes. Then, the cysteine‐rich metallopeptide thionein was conjugated onto the CB‐immobilized membrane. The maximum amounts of CB immobilized and thionein conjugated on the membranes were 1.07 µmol cm⁻² and 0.92 µmol cm⁻², respectively. The hydrophilic pHEMA membrane had a swelling ratio of 58% (w/w) with a contact angle of 45.8 °. CB‐immobilized and CB‐immobilized–thionein‐conjugated membranes were used in the Cd(II) removal studies. Cd(II) ion adsorption appeared to reach equilibrium within 30 min and to follow a typical Langmuir adsorption isotherm. The maximum capacity (q _m) of the CB‐immobilized membranes was 0.203 (µmol Cd(II)) cm⁻² membrane and increased to 1.48 (µmol Cd(II)) cm⁻² upon CB–thionein‐complex conjugation. The pHEMA membranes retained their cadmium adsorption capacity even after 10 cycles of repeated use. © 2000 Society of Chemical Industry     

Ion imprinted beads embedded cryogels for in vitro removal of iron from β-thalassemic human plasma

Molecular recognition based Fe³⁺ imprinted poly(GMA-MAC) (MIP) beads embedded PHEMA composite cryogel was prepared for selective removal of Fe³⁺ ions from β-thalassemia patient plasma. The precomplexation was achieved by the coordination of Fe³⁺ ions with N-methacryloyl-(L )-cysteine methyl ester (MAC-Fe³⁺). MIP beads were prepared by dispersion polymerization in the presence of MAC-Fe³⁺ complex and glycidyl methacrylate (GMA) monomer. Then the MIP beads were embedded into poly(hydroxyethyl methacrylate) (PHEMA) cryogel. The specific surface area and the swelling degree of the PHEMA-MIP composite cryogel were found to be 76.8 m²/g and 7.7 g H₂O/g cryogel, respectively. The maximum adsorption amount of Fe³⁺ ions was 2.23 mg/g. The relative selectivity of PHEMA-MIP composite cryogel towards the Fe³⁺ ions was 135.0, 61.4, and 57.0 times greater than that of the PHEMA-NIP cryogel as compared with the Ni²⁺, Zn²⁺, and Fe²⁺ ions, respectively. PHEMA-MIP composite cryogel was recovered and reused many times without any significant decrease in its adsorption capacity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Cu(II)‐incorporated,histidine‐containing,magnetic‐metal‐complexing beads as specific sorbents for the metal chelate affinity of albumin

N‐Methacryloyl‐(L )‐histidine methyl ester (MAH) was synthesized from metharyloyl chloride and histidine. Spherical beads with an average size of 150–250 μm were obtained by the suspension polymerization of ethylene glycol dimethacrylate and MAH in an aqueous dispersion medium. Magnetic poly(ethylene glycol dimethacrylate‐co‐N‐Methacryloyl‐(L )‐histidine methyl ester) [m‐p(EGDMA‐co‐MAH)] microbeads were characterized with swelling tests, electron spin resonance, elemental analysis, and scanning electron microscopy. The specific surface area of the beads was 80.1 m²/g. m‐p(EGDMA‐co‐MAH) microbeads with a swelling ratio of 40.2% and 43.9 μmol of MAH/g were used for the adsorption of bovine serum albumin (BSA) in a batch system. The Cu(II) concentration was 4.1 μmol/g. The adsorption capacity of BSA on the Cu(II)‐incorporated beads was 19.2 mg of BSA/g. The BSA adsorption first increased with the BSA concentration and then reached a plateau, which was about 19.2 mg of BSA/g. The maximum adsorption was observed at pH 5.0, which was the isoelectric point of BSA. The BSA adsorption increased with decreasing temperature, and the maximum adsorption was achieved at 4°C. High desorption ratios (>90% of the adsorbed BSA) were achieved with 1.0M NaSCN (pH 8.0) in 30 min. The nonspecific adsorption of BSA onto the m‐p(EGDMA‐co‐MAH) beads was negligible. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2669–2677, 2004     

New Modified Controlled Bat Algorithm for Numerical Optimization Problem

Bat algorithm (BA) is an eminent meta-heuristic algorithm that has been widely used to solve diverse kinds of optimization problems. BA leverages the echolocation feature of bats produced by imitating the bats’ searching behavior. BA faces premature convergence due to its local search capability. Instead of using the standard uniform walk, the Torus walk is viewed as a promising alternative to improve the local search capability. In this work, we proposed an improved variation of BA by applying torus walk to improve diversity and convergence. The proposed. Modern Computerized Bat Algorithm (MCBA) approach has been examined for fifteen well-known benchmark test problems. The finding of our technique shows promising performance as compared to the standard PSO and standard BA. The proposed MCBA, BPA, Standard PSO, and Standard BA have been examined for well-known benchmark test problems and training of the a.pngicial neural network (ANN). We have performed experiments using eight benchmark datasets applied from the worldwide famous machine-learning (ML) repository of UCI. Simulation results have shown that the training of an ANN with MCBA-NN algorithm tops the list considering exactness, with more superiority compared to the traditional methodologies. The MCBA-NN algorithm may be used effectively for data classification and statistical problems in the future.     

New generation polymeric nanospheres for lysozyme adsorption

Novel hydrophobic nanospheres with an average size of 100 nm utilizing N‐methacryloyl‐(l)‐tryptophan methyl ester (MAT) as a hydrophobic monomer were prepared by surfactant free emulsion polymerization of 2‐hydroxyethyl methacrylate (HEMA) and MAT. MAT was synthesized using methacryloyl chloride and l‐tryptophan methyl ester. Specific surface area of the nonporous nanospheres was found to be 1914 m²/g. Poly(HEMA–MAT) nanospheres were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Average particle size, size distribution, and surface charge measurements were also performed. Elemental analysis of MAT for nitrogen was estimated as 1.95 mmol/g polymer. Then, poly(HEMA–MAT) nanospheres were used in the adsorption of lysozyme in batch system. Using an optimized adsorption protocol, a very high loading of 1075 mg lysozyme/g nanosphere was obtained. The adsorption phenomena appeared to follow a typical Langmuir isotherm. It was observed that enzyme could be repeatedly adsorbed and desorbed without significant loss in adsorption amount or enzyme activity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fractal dimension of Apollonian packing of spherical particles

Three-dimensional Apollonian packing with random distribution of initially prepacked spheres is investigated. The computer simulation model with specially designed changing range genetic algorithm was developed to estimate the fractal dimensions of Apollonian packing of spherical particles. The fractal dimensions corresponding to the packing degree and porosity were calculated for a large range of spherical particles (in the order of millions). The result obtained provides an experimental proof of a lower bound of the fractal dimension analytically found by [3] (Aste, Phys. Rev. E, 1996; 53: 2571).     

Electron‐Induced Dynamics of Heptathioether β‐Cyclodextrin Molecules

Variable‐temperature scanning tunneling microscopy (STM) and spectroscopy (STS) measurements are performed on heptathioether β‐cyclodextrin (β‐CD) self‐assembled monolayers (SAMs) on Au. The β‐CD molecules exhibit very rich dynamical behavior, which is not apparent in ensemble‐averaged studies. The dynamics are reflected in the tunneling current–time traces, which are recorded with the STM feedback loop disabled. The dynamics are temperature independent, but increase with increasing tunneling current and sample bias, thus indicating that the conformational changes of the β‐CD molecules are induced by electrons that tunnel inelastically. Even for sample biases as low as 10 mV, well‐defined levels are observed in the tunneling current–time traces. These jumps are attributed to the excitations of the molecular vibration of the macrocyclic β‐CD molecule. The results are of great importance for a proper understanding of transport measurements in SAMs.     

TACO-miner: An ant colony based algorithm for rule extraction from trained neural networks

Extracting classification rules from data is an important task of data mining and gaining considerable more attention in recent years. In this paper, a new meta-heuristic algorithm which is called as TACO-miner is proposed for rule extraction from artificial neural networks (ANN). The proposed rule extraction algorithm actually works on the trained ANNs in order to discover the hidden knowledge which is available in the form of connection weights within ANN structure. The proposed algorithm is mainly based on a meta-heuristic which is known as touring ant colony optimization (TACO) and consists of two-step hierarchical structure. The proposed algorithm is experimentally evaluated on six binary and n-ary classification benchmark data sets. Results of the comparative study show that TACO-miner is able to discover accurate and concise classification rules.