Chemical and Biomolecular Engineering

Preparative affinity chromatography of proteins based on pseudoaffinity adsorbents has ability to purify proteins to high purity at low cost. Design of relatively inexpensive amino acid based pseudobioaffinity adsorbent for single step chromatographic purification of immunoglobulins (IgGs) based on molecular recognition was carried out using molecular modeling techniques. Molecular libraries such as small peptides and amino acids were screened using molecular simulation based screening and docking softwares to determine the molecules with high affinity towards the immunoglobulins. This work finally resulted in a construction of a pseudoaffinity adsorbent for IgGs based on covalently grafted hydrophobic amino acid derivatives such as those based on propionic acid and was named AbSep. AbSep was then exploited for the purification of Immunoglobulins (IgGs) directly from human plasma. Investigation of the specificity demonstrated by AbSep towards IgGs indicated that IgGs bind to AbSep through residues on the hinge region of IgGs. Column runs showed that AbSep has a binding capacity for immunoglobulins of about 50mg/ml and exhibits the ability to purify IgG to more than 90% in a single step from blood plasma with recovery of > 85% without formation of any aggregates.

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inside the carbon nanotubes at temperatures ranging from 298 to 683 K. The structural characteristics of the coordination shells of ions are studied, including the ion-oxygen radial distribution functions, the coordination numbers, and the orientation distributions of the water molecules. Simulation results show that the first coordination shells of the five ions still exist in the nanoscale confinement. Nevertheless, the first coordination shell structures of cations change more significantly than those of anions because of the preferential orientation of the water molecules induced by the carbon nanotube. The first coordination shells of cations are considerably less ordered in the nanotube than in the bulk solution, whereas the change of the first coordination shell structures of the anions is minor. Furthermore, the confinement induces the anomalous behavior of the coordination shells of the ions with temperature. The first coordination shell of K + are found to be more ordered as the temperature increases only in the carbon nanotube with the effective diameter of 1.0 nm, implying the enhancement of the ionic hydration with temperature. This is contrary to that in the bulk solution. The coordination shells of the other four ions do not have such behavior in the carbon nanotube with the effective diameter ranging from 0.73 to 1.00 nm. The easier distortion of the coordination shell of K + and the match of the shell size and the nanotube size may play roles in this phenomenon. The exchange of water molecules in the first coordination shells of the ions with the solution and the ion diffusion along the axial direction of the nanotube are also investigated. The mobility of the ions and the stability of the coordination shells are greatly affected by the temperature in the nanotube as in the bulk solutions. These results help to understand the biological and chemical processes at the high temperature.

Equilibrium molecular dynamics simulations have been performed to investigate the structural characteristics of ethanol molecules confined in single-walled, pristine armchair carbon nanotubes with a length of 2.5 nm and diameters ranging from 0.68 to 1.35 nm in an open ethanol reservoir at 298.0 K and 100.0 kPa by all-atom and united-atom models. Both models present similar results. Structural properties of confined ethanol molecules are analyzed in terms of the average number of hydrogen bonds, radial density distributions of methyl and hydroxyl groups, orientation distributions of the methyl-methylene bond, oxygen-hydrogen bond and dipole moment, and molecular conformations as a function of the diameter of carbon nanotubes.

We report experimental results on the melting behavior of a dipolar substance, bromobenzene, adsorbed in multiwalled carbon nanotubes (MWNTs) of (2.4, 4.0, and 10) nm inner diameter. Dielectric relaxation spectroscopy (DRS) and differential scanning calorimetry (DSC) methods have been used to show a solid-liquid transition of confined C 6 H 5 Br. The C 6 H 5 Br melting point in pores has been found to increase with decreasing pore diameter. This result is in qualitative agreement with that obtained in molecular simulation for CCl 4 in similar MWNTs, where the adsorbate-wall interactions are strong compared to the adsorbate-adsorbate interactions (see Jazdzewska et al., Phys. Chem. Chem. Phys. 2005, 7, 3884-3887).

We report experimental results on the structure and melting behavior of ice confined in multi-walled carbon nanotubes and ordered mesoporous carbon CMK-3, which is the carbon replica of a SBA-15 silica template. The silica template has cylindrical mesopores with micropores connecting the walls of neighboring mesopores. The structure of the carbon replica material CMK-3 consists of carbon rods connected by smaller side-branches, with quasi-cylindrical mesopores of average pore size 4.9 nm and micropores of 0.6 nm. Neutron diffraction and differential scanning calorimetry have been used to determine the structure of the confined ice and the solid-liquid transition temperature. The results are compared with the behavior of water in multi-walled carbon nanotubes of inner diameters of 2.4 nm and 4 nm studied by the same methods. For D 2 O in CMK-3 we find evidence of the existence of nanocrystals of cubic ice and ice IX; the diffraction results also suggest the presence of ice VIII, although this is less conclusive. We find evidence of cubic ice in the case of the carbon nanotubes. For bulk water these crystal forms only occur at temperatures below 170 K in the case of cubic ice, and at pressures of hundreds or thousands of MPa in the case of ice VIII and IX. These phases appear to be stabilized by the confinement.

Elevated solar UV-B radiation associated with stratospheric ozone reduction may exert effects on terrestrial ecosystems through actions on plants, microbes, and perhaps on some animals. At the ecosystem level, the effects are less well understood than at the molecular and organismal levels. Many of the most important, yet less predictable, consequences will be indirect effects of elevated UV-B acting through changes in the chemical composition and form of plants and through changes in the abiotic environment. These indirect effects include changes in the susceptibility of plants to attack by insects and pathogens in both agricultural and natural ecosystems; the direction of these changes can result in either a decrease or an increase in susceptibility. Other indirect effects of elevated UV-B include changes in competitive balance of plants and nutrient cycling. The direct UV-B action on plants that results in changes in form or function of plants appears to occur more often through altered gene activity rather than damage. The yield of some crop varieties can be decreased by elevated UV-B, but other varieties are not affected. Plant breeding and genetic engineering efforts should be able to cope with the potential threats to crop productivity due to elevated UV-B. For forest trees, this may be more difficult if effects of elevated UV-B accumulate over several years. All effects of elevated UV-B radiation must be considered in the context of other climate changes such as increased temperature and levels of carbon dioxide, which may alter the UV-B responses, especially for plants. The actions of elevated carbon dioxide and UV-B appear to be largely independent, but interactions occur between changes in UV-B and other factors. Other ecosystem-level consequences of elevated UV-B radiation are emerging and their magnitude and direction will not be easily predicted.

We demonstrate the specificity, regenerability, and excellent storage stability of short peptide-based systems for detection of immunoglobulin G (IgG). The bioactive component consisted of acetylated-HWRGWVA (Ac-HWRGWVA), a peptide with high IgG binding affinity, which was immobilized onto copolymer matrixes of poly(2aminoethyl methacrylate hydrochloride-co-2-hydroxyethyl methacrylate) (poly(AMA-co-HEMA)). Surface plasmon resonance (SPR) and quartz crystal microgravimetry (QCM) were utilized with other complementary techniques to systematically investigate interfacial activities, mainly IgG binding performance as a function of the graft density and degree of polymerization of the poly(AMA-co-HEMA) support layer. Results from sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorescence microscopy indicate that the bioactive system is highly specific to IgG and resistant to nonspecific interactions when tested in mixed protein solutions.

This paper characterizes the potential of novel hexameric peptide ligands for on-line IgG detection in bioprocesses. Surface Plasmon Resonance (SPR) was used to study the binding of human IgG to the hexameric peptide ligand HWRGWV, which was covalently grafted to alkanethiol self-assembled monolayers (SAM) on gold surfaces. Peptide coupling on SAMs was verified, followed by covalent grafting of peptides with a removable Fmoc or acetylated N-termini via their C-termini to produce active peptide SPR sensors that were tested for IgG binding. The dynamics and extent of peptide-IgG binding were compared with results from a conventional system using protein A attached on a gold surface via disulfide monolayers. IgG binding to protein A on disulfide monolayers yielded equilibrium dissociation constants of 1.4 Â 10 -7 M. The corresponding dissociation constant value for the acetylated version of the peptide (Ac-HWRGWV) supported on alkanethiol SAM was 5.8 Â 10 -7 M and that for HWRGWV on the alkanethiol SAM (after de-protection of Fmoc-HWRGWVA) was 1.2 Â 10 -6 M. Maximum IgG binding capacities, Q m of 6.7, 3.8, and 4.1 mg m À 2 were determined for the protein A and the two forms of HWRGWV-based biosensors, respectively. Real-time data for the kinetics of adsorption were used to determine the apparent rate constants for adsorption and desorption. The results were analyzed to understand the mechanism of IgG binding to the protein and peptide ligands. It was found that the peptide-IgG binding was reaction controlled, however the protein A-IgG binding mechanism was partially mass transfer (diffusion) controlled. The adsorption rate constants, k a , for the protein A ligand increased with decreasing concentration of analyte and the peptide ligand k a values was constant at different IgG concentrations and flow rates.

Background e-Waste is a rapidly growing waste stream worldwide, and Bangladesh is a hub of e-waste handling. Informal e-waste recycling operations involve crude methods for dismantling, repairing, sorting, and recycling electronic goods with bare hands and without personal health protections. Direct inhalation or dermal exposure to toxicants during informal recycling is common. Evidence suggests that e-waste–derived toxicants pollute the terrestrial ecosystem and have been linked with adverse health effects. However, e-waste recycling–related occupational health hazards have not been adequately explored in the context of Bangladesh. Objective Our study aims to expand the current understanding of exposure to e-waste. This study will measure the metal concentrations in biological and environmental samples and evaluate the relationship between heavy metals and the biochemical systems of the e-waste workers. Methods The study uses a cross-sectional study design consisting of an exposed ...

Due to their inherent ability to microphase-segregate into well-defined nanostructures, AB diblock copolymers serve as model surfactants to probe complex phase behavior and precursor materials to nanoscale-templated motifs. ^I n the melt, alone or in miscible blends with other (co)polymers, AB molecules can spontaneously self-organize into a variety of nanoscale morphologies, the size and shape of which reflect the packing of A and B repeat units along the interface separating A-and B-rich spatial regions. Interfacial chain packing and, hence, curvature are strongly dictated by factors such as the size, number and incompatibility of the A and B repeat units along the copolymer backbone. Most block copolymer morphologies of fundamental and technological interest are periodic and are generally classified as either classic or complex, depending on topological metrics such as symmetry, coordination and genus. Aperiodic copolymer melt morphologies described as sponges or bicontinuous emulsions are also of contemporary interest. This wealth of block copolymer phase behavior is preserved when copolymer molecules microphase-separate in the presence of one or two selective solvents. In addition to those copolymer nanostructures observed in the melt, however, novel solvated supramolecular aggregates (e.g., crew-cut micelles, nanotubes, "hamburger" micelles, polymersomes and toroids) and network nanostructures likewise develop under favorable conditions. Solvated block copolymer nanostructures and the solvent distribution therein depend on factors such as solvent concentration, selectivity and size. Polyferrocenylsilanes are a class of metal-containing polymers that can be amorphous or semi-crystalline depending on the substituent groups present. These materials are of particular interest in the design of functional materials due to their inherent redox tunability, electronic and other physical properties, as well as their ability to function as precursors to magnetic ceramics or carbon nanotube growth catalysts. Some block copolymers, such as those containing a crystallizable polyferrocenyldimethylsilane (PFS) block, have been found to exhibit unique phase behavior in the presence of a selective solvent. Molten PFS-b-polystyrene copolymers and their blends with polystyrene homopolymer are reported to order into the same classical and complex morphologies established for conventional copolymer blends. When, however, the second, much longer block is polydimethylsiloxane (PDMS) and the resulting asymmetric PFS-b-PDMS diblock copolymer is added at relatively low concentrations to a siloxane-selective solvent such as n-hexane at elevated temperature and subsequently cooled to ambient temperature, the copolymer molecules can order into high-aspect-ratio aggregates that have been previously described as nanotubes composed of a PFS inner shell and PDMS outer shells. Such molecular organization is sensitive to copolymer composition and solution concentration, as well as growth conditions (time and temperature), since the nanotubes typically require several days to fully develop. Precise formation of such nanoscale objects is of considerable interest in the design of functional materials for nanotechnology, in which case the objective of the present study is to elucidate the mechanistic COMMUNICATION

Polymer/clay nanocomposites (NCs) prepared using melt intercalation must be properly formulated and processed to achieve intercalation or exfoliation. Organically modified layered silicates (OMLSs) are often used to permit polymer intercalation and thereby separate the silicate platelets. Prior modeling efforts suggest that high-molecular-weight (HMW) polymers tend to yield immiscible NCs unlike their low-molecular-weight (LMW) analogs, which commonly result in exfoliated or intercalated NCs. Although formulations containing LMW polar additives (e.g., maleic anhydride copolymers) have succeeded in producing at least partially exfoliated rather than immiscible NCs, a need persists for simpler HMW formulations in order to expedite industrial scale-up.

Gels of styrenic triblock copolymers swollen by a low-volatility, midblock-selective oil behave as high-strain, low-field dielectric elastomers in the design of electroactive polymeric actuators. A standard configuration of such devices involves stretching, or ``prestraining,'' ...

Novel protein blends have been prepared by mixing gelatin (G) with Bombyx mori silk fibroin (SF) and using aqueous methanol (MeOH) to post-induce SF crystallization. When co-cast from solution, amorphous blends of these polymers appear homogeneous, as discerned from visual observation, microscopy, and Fourier-transform infrared (FTIR) spectroscopy. Upon subsequent exposure to aqueous MeOH, SF undergoes a conformational change from random coil to sheet. This transformation occurs in pure SF, as well as in each of the G/SF blends, according to X-ray diffractometry and thermal calorimetry. The influence of MeOH-induced SF crystallization on structure and property development has been ascertained in terms of preparation history and blend composition. Thermal gravimetric analysis reveals that the presence of sheets in SF and G/SF blends improves thermal stability, while extensional rheometry confirms that SF crystallization enhances the tensile properties of the blends. By preserving a support scaffold above the G helix-to-coil transition temperature, the formation of crystalline SF networks in G/SF blends can be used to stabilize G-based hydrogels for biomaterial and pharmaceutical purposes. The present study not only examines the properties of G/SF blends before and after SF crystallization, but also establishes the foundation for future research into thermally responsive G/SF bioconjugates. Figure 4. CLSM images acquired from (a,b) pure SF and (c) the G/SF25 blend after exposure to aqueous MeOH for 2 h at 20°C.

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Recent studies have demonstrated that addition of a small quantity of dibenzylidene sorbitol (DBS) to a molten polymer may result in a physical gel if conditions permit the DBS molecules to self-organize into a three-dimensional network composed of highly connected nanofibrils. If the polymer crystallizes, DBS may also serve as a nucleating agent, promoting the formation of spherulites, especially in commercially important polyolefins such as polypropylene. We examine the thermal and mechanical properties, as well as the morphological characteristics, of an isotactic polypropylene copolymer with 3 wt % ethylene upon addition of less than 1 wt % of 1,3:2,4-di-pmethylbenzylidene sorbitol (MDBS). From dynamic rheological measurements, pronounced complex viscosity increases, attributed to MDBS nanofibril network formation, are observed at concentration-dependent temperatures above the melting point of the nucleated copolymer. Transmission electron micrographs of RuO 4 -stained sections confirm the existence of MDBS nanofibrils measuring on the order of 10 nm in diameter and, at higher concentrations, fibrillar bundles measuring up to about 200 nm across and several microns in length. The addition of MDBS at different concentrations is also found to promote increases in optical clarity, yield strength, tensile strength, and ultimate elongation of modified copolymer formulations.