Radiation-induced grafting of diallyldimethylammonium chloride onto acrylic acid grafted polyethylene

Diallyldimethylammonium chloride (DADMAC) was grafted onto polyethylene (PE) films by a double grafting procedure. The PE film was initially modified by grafting acrylic acid (AA), through a mutual irradiation method. AA-g-PE film, thus obtained was subjected to subsequent radiation grafting reaction of DADMAC, to give a DADMAC-g-AA-g-PE film having a comb-type structure. The influence of different conditions, such as the extent of AA grafting, DADMAC concentration, absorbed dose and dose rate, on the grafting yield of DADMAC was investigated. A maximum DADMAC grafting of 30% was achieved. The equilibrium degree of swelling (EDS) of the grafted films were gravimetrically determined. TGA and FT-IR techniques were employed to characterize the grafted PE films.     

Synthesis and morphology of polyethylene chains grafted onto the surface of crosslinked polystyrene microspheres

The bifunctional comonomer 4‐(3‐butenyl) styrene was used to synthesize crosslinked polystyrene microspheres (c‐PS) with pendant butenyl groups on their surface via suspension copolymerization. Polyethylene chains were grafted onto the surface of c‐PS microspheres (PS‐g‐PE) via ethylene copolymerizing with the pendant butenyl group on the surface of the c‐PS microspheres under the catalysis of metallocene catalyst. The composition and morphology of the PS‐g‐PE microspheres were characterized by means of Fourier transform infrared spectroscopy, Fourier transform Raman spectroscopy, X‐ray photoelectron spectroscopy, and field‐emission scanning electron microscopy. It is possible to control the content of PE grafted onto the surface of c‐PS microspheres by varying the polymerization time or the initial quantity of pendant butenyl group on the surface of c‐PS microspheres. Investigation on the morphology and crystallization behavior of grafted PE chains showed that different surface patterns could be formed under various crystallization conditions. Moreover, the crystallization temperature of PE chains grafted on the surface of c‐PS microspheres was 6 °C higher than that of pure PE. The c‐PS microspheres decorated by PE chains had a better compatibility with PE matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4477–4486, 2007     

Immobilization of trypsin onto multifunctional meso-/macroporous core-shell microspheres: A new platform for rapid enzymatic digestion

A simple, fast, efficient, and reusable microwave-assisted tryptic digestion system which was constructed by immobilization of trypsin onto porous core-shell Fe₃O₄@fTiO₂ microspheres has been developed. The nanostructure with magnetic core and titania shell has multiple pore sizes (2.4 and 15.0 nm), high pore volume (0.25 cm³ g⁻¹), and large surface area (50.45 m² g⁻¹). For the proteins, the system can realize fast and efficient microwave-assisted tryptic digestion. Various standard proteins (e.g., cytochrome c (cyt-c), myoglobin (MYO), β-lactoglobulin (β-LG), and bovine serum albumin (BSA)) used can be digested in 45 s under microwave radiation, and they can be confidently identified by mass spectrometry (MS) analysis; even the concentration of substrate is as low as 5 ng μL⁻¹. Furthermore, the system for the 45 s microwave-assisted tryptic digestion is still effective after the trypsin-immobilized microspheres have been reused for 5 times. Importantly, 1715 unique proteins from 10 μg mouse brain proteins can be identified with high confidence after treatment of 45 s microwave-assisted tryptic digestion.     

Immobilization of bovine serum albumin onto porous polyethylene membranes using strongly attached polydopamine as a spacer

Based on the self-polymerization and strong adhesion characteristics of dopamine in aqueous solution, a novel and convenient approach was developed to immobilize protein onto porous polyethylene (PE) membranes. A thin polydopamine (pDA) layer was formed and tightly coated onto PE membrane by dipping simply the membrane into dopamine aqueous solution for a period of time. Subsequently, bovine serum albumin (BSA) was bound onto the obtained PE/pDA composite membranes via the coupling between BSA and the reactive polydopamine layer. The firm immobilization of polydopamine layer and BSA was verified by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The results of water contact angle measurement showed that the hydrophilicity of PE membrane was significantly improved after coating polydopamine and binding BSA. The experiments of blood platelet adhesion indicated that BSA-immobilized PE membrane had better blood compatibility than the unmodified PE and the PE/pDA composite membranes. The investigations on hepatocyte cultures and cell viability revealed that the polydopamine coating endowed PE membrane with significantly improved cell compatibility. Compared to BSA surface, polydopamine surface is more favorable for cell adhesion, growth, and proliferation.     

Immobilization of a protease on grafted polyethylenes

It has been shown that when the protease ofBacillus mesentericus is immobilized on polyethylene with grafted-on polyacrylic acid by the carbodiimide method there is a considerable retention of its activity and an increase in its thermal stability, and the immobilized preparations are active on repeated use.Institute of Physical Chemistry, Academy of Sciences of the Ukrainian SSR, Odessa. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 512–516, July–August, 1983.     

Tryptophan-based peptides grafted onto oxidized nanocellulose

Oxidized nanocellulose (ONC) have been synthesized and grafted with tryptophan-based peptides of varying lengths using a two step coupling method. The ONC was first activated by N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide hydrochloride, forming a stable active ester in the presence of N-hydroxysuccinimide. Then, the active ester was reacted with the amino groups of the peptide forming an amide bond between ONC and peptide. Using this method, the intermolecular connection of Trp-based peptides (Trp-Ps) was avoided and uniform coupling of peptides on ONC was achieved. The coupling reaction was very fast in mild conditions and without alteration of the polysaccharide. The obtained products (ONC-Trp-Ps) were characterized by transmission electron microscopy and by different spectroscopic techniques.     

Immobilization ofAzacrown Ligand onto a Fluorophore

Geometric immobilization of azacrown ligand onto a fluorophore is expected to change their binding properties toward ion discrimination. An immobilized azacrown ligand 1 onto anthracene fluorophore senses Al(III), Cu(II) and Ga(III) in ethanol among the metal ions examined. In 100% aqueous solution, ligand 1 shows large CHEF effects with Al(III) and Ga(III) and large CHEQ effect with Hg(II). By comparison, non-immobilized azacrown ligand 2 showed large CHEF effects with Al(III), Ce(III), Ga(III), La(III) and Zn(II) in ethanol.     

Synthesis and characterization of polyethylene chains grafted onto the sidewalls of single‐walled carbon nanotubes via copolymerization

Polyethylene (PE) chains grafted onto the sidewalls of SWCNTs (SWCNT‐g‐PE) were successfully synthesized via ethylene copolymerization with functionalized single‐walled carbon nanotubes (f‐SWCNTs) catalyzed by rac‐(en)(THInd)₂ZrCl₂/MAO. Here f‐SWCNTs, in which α‐alkene groups were chemically linked on the sidewalls of SWCNTs, were synthesized by Prato reaction. The composition and microstructure of SWCNT‐g‐PE were characterized by means of ¹H NMR, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analyses (TGA), field‐emission scanning electron microscope (FESEM), and transmission electron microscope (TEM). Nanosized cable‐like structure was formed in the SWCNT‐g‐PE, in which the PE formed a tubular shell and several SWCNTs bundles existed as core. The formation of the above morphology in the SWCNT‐g‐PE resulted from successfully grafting of PE chains onto the surface of SWCNTs via copolymerization. The grown PE chains grafted onto the sidewall of the f‐SWCNTs promoted the exfoliation of the mass nanotubes. Comparing with pure PE, the physical mixture of PE/f‐SWCNTs and in situ PE/SWCNTs mixture, thermal stability, and mechanical properties of SWCNT‐g‐PE were higher because of the chemical bonding between the f‐SWCNTs and PE chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5459–5469, 2007     

Immobilization of amyloglucosidase onto granular chicken bone

Amyloglucosidase was immobilized onto granular chicken bone (BIOBONE?) by noncovalent interactions. The amount of activity bound relative to an equal amount of free enzyme was 13.6 ?0.4%. The estimated specific activity for amyloglucosidase decreased from 75.3?0.8 to 43.5 ?9.6 U/mg protein upon immobilization. TheKm value of the bone-immobilized enzyme using glycogen as substrate increased from 3.04?0.38 mg/mL (free) to 9.04? 1.51 mg/mL (immobilized), butKm showed no change upon immobilization when starches were used as substrates. A decrease in V_max values occurred upon enzyme immobilization for all substrates, but this largely reflected the percentage of enzyme initially bound to the bone. Immobilization also improved enzyme stability in the presence of various additives (e.g., detergent, KC1, and ethanol) or under low or high pH reaction conditions. Bound amyloglucosidase maintained high activity (>90%) following five cycles of continuous use at moderate (23 ?C) and high (55?C) temperatures. Data derived from Lineweaver-Burk and Arrhenius plots indicated that substrate and product diffusion limitation were minimal.     

Immobilization of hexokinase onto chitosan decorated particles

Chitosan (CH) decorated polystyrene (PS) particles were synthesized within complexes of CH, a polycation under acid conditions, and tiny amounts of sodium dodecylsulfate (SDS). Particle characterization was performed by means of dynamic light scattering, zeta potential measurements, and transmission electron microscopy. All dispersions were stable in the ionic strength of 2.0 mol L-1 NaCl during 2 months. The outstanding colloidal stability was attributed to the presence of a hydrated CH layer around the particles. CH decorated PS particles were attached to atomic force microscopy cantilevers and probed against Si wafers in water and in NaCl 0.01 mol/L. The mean thickness of CH layer amounted to 35 +/- 11 and 16 +/- 6 nm, when the medium was water and NaCl 0.01 mol/L, respectively. Adsorption isotherm of hexokinase (HK) onto PS/CH particles studied by means of spectrophotometry showed three regions: an initial step; adsorption plateau and multilayer formation. Enzymatic activity of free HK and immobilized HK was monitored by means of spectrophotometry as a function of storing time and reuse. After 3 days, storing HK free in solution dramatically lost its catalytic properties. On the contrary, HK-covered PS/CH particles retained enzymatic activity over 1 month. Moreover, HK-covered PS/CH particles could be reused in the determination of glucose two times consecutively, without losing activity. These interesting findings were discussed in light of the role of water in enzyme conformation.     

Mixed homopolymer brushes grafted onto a nanosphere

Microphase separation of mixed A∕B polymer brushes grafted onto a nanosphere with its radius comparable to the size of polymers is investigated by numerical implementation of the self-consistent field theory. The idea is to embed the sphere within a larger cubic computational cell and use a "masking" technique to treat the spherical boundary. The partial differential equations for the chain propagator on the sphere can thus be readily solved with an efficient and high-order accurate pseudospectral method involving fast Fourier transform on a cubic cell. This numerical technique can circumvent the "pole problem" due to the use of a spherical coordinate system in conventional finite difference or finite element grid. We systematically investigate the effect of the total grafting density, composition, chain length asymmetry between two grafted homopolymers as well as spherical radius, i.e., substrate curvature on the formation of island structure with specific arrangement in a regular lattice. A series of island structures with different island numbers representing specific structure symmetry ranging from 2 to 12 except for 11 are found, in contrast to conventional hexagonal arrangement for polymer brushes on a planar substrate. Among these parameters, the spherical radius plays a significant role in determining the type of island structures, i.e., the morphology formed on the sphere.     

Immobilization of cellulase using acrylamide grafted acrylonitrile copolymer membranes

Immobilization of cellulase onto acrylamide grafted acrylonitrile copolymer (PAN) membranes by means of glutaraldehyde has been studied. The bound cellulase was verified by X-ray photoelectron spectroscopy. The activities of free cellulase and immobilized cellulase are determined by measuring the amount of glucose made from carboxymethyl cellulase in the given conditions. Results show that immobilization conditions had some effects on the activity of immobilized cellulase. The immobilized cellulase had a higher K_m than free cellulase (0.02 mg/ml) did. The immobilized cellulase had better stability with respect to pH or temperature than free cellulase.     

固定化人工膜动态固载胰蛋白酶的条件优化

以固定化人工膜为载体研究胰蛋白酶的动态固定化,考察缓冲液种类(硼酸盐、磷酸盐和Tris-HCl)、浓度、pH对胰蛋白酶固载率和酶活性的影响.结果显示,pH=8.0的10mmol/L Tris-HCl缓冲液是胰蛋白酶的优化固载条件.在此条件下,初步研究了动态固定化胰蛋白酶酶解器,发现其具有较高酶活性,且胰蛋白酶抑制剂能对其活性进行特异性抑制.     

Immobilization of glucose isomerase onto granular chicken bone

Glucose isomerase was immobilized onto granular chicken bone (BIOBONE?) by adsorption. The amount of activity bound relative to an equal amount of free enzyme was 32?1%, with the estimated specific activity decreasing from ll.l?0.7 to 3.9?0.5 U/mg protein with immobilization. Compared with the free enzyme, immobilized glucose isomerase showed a threefold increase in theKm for fructose and a fivefold decrease in V_max. High operating temperatures were possible (>55?C), but continuous use and long-term storage studies showed gradual losses of activity. Both the binding and the activity of the bone-immobilized enzyme were highly resistant to treatments with detergent, ethanol, and KC1. Studies to determine mass transfer limitation effects on immobilized glucose isomerase showed that these were insignificant for this system.     

壳聚糖-g-丙烯腈固定化木瓜蛋白酶的研究

接枝共聚物;啤酒;壳聚糖-g-丙烯腈固定化木瓜蛋白酶的研究     

Amplified fluorescence response of chemosensors grafted onto silica nanoparticles

In conventional fluorescent chemosensors, the recognition of the target by the receptor unit affects the fluorescence properties of a single covalently coupled fluorescent moiety. Here we show for the first time that when a suitable TSQ derivative is densely grafted onto the surface of preformed silica nanoparticles electronic interactions between the individual chemosensor units enable the free units to recognize the state of the surrounding complexed ones. As a result, the fluorescence transduction is not limited to the local site where binding occurs, but it involves a wider region of the fluorophore network that is able to transfer its excitation energy to the complexed units. Such behavior leads to an amplification of the fluorescence signal. What we report here is the first example of amplification in the case an off-on chemosensor due to its organization onto the surface of silica nanoparticles. We also describe a simple general model to approach amplification in multifluorophoric systems based on the localization of the excited states, which is valid for assemblies such as the supramolecular ones where molecular interactions are weak and do not significantly perturb the individual electronic states. The introduction of an amplification factor f in particular allows for a simple quantitative estimation of the amplification effects.     

Molecular dynamics of alkyl radicals grafted onto silica surface

Correlation times for≡SiOC·X₂ radicals grafted onto activated silica surface were estimated to be 1.3·10⁻⁸s (X=H) and 2.5·10⁻⁸s (X=Me) at room temperature. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 613–616, April, 1998.