共查询到20条相似文献,搜索用时 421 毫秒
1.
Georgi E. Chernev Bisserka I. Samuneva Petar R. Djambaski Isabel M. M. Salvado Helena V. Fernandes 《Central European Journal of Chemistry》2006,4(1):81-91
In this work we present experimental results about the formation, properties and structure of sol — gel silica based biocomposite
containing Calcium alginate as an organic compound. Two different types of silicon precursors have been used in the synthesis:
tetramethylortosilicate (TMOS) and ethyltrimethoxysilane (ETMS). The samples have been prepared at room temperature. The hybrids
have been synthesized by replacing different quantitis of the inorganic precursor with alginate. The structure of the obtained
hybrid materials has been studied by XRD, IR Spectroscopy, EDS, BET and AFM. The results proved that all samples are amorphous
possessing a surface area from 70 to 290 m2/g. It has also been established by FT IR spectra that the hybrids containing TMOS display Van der Walls and Hydrogen bonding
or electrostatic interactions between the organic and inorganic components. Strong chemical bonds between the inorganic and
organic components in the samples with ETMS are present. A self-organized nanostructure has been observed by AFM. In the obtained
hybrids the nanobuilding blocks average in size at about 8–14 nm for the particles. 相似文献
2.
The selection of sol compositions, conditions of preparation and storage of gels are an important aspects for encapsulating
biomolecules in gel matrix for applications in biosensor. In the present investigation, fluorescence spectroscopic measurements
(emission and fluorescence lifetimes) were carried out in bulk gel and thin films prepared from sols with water and tetraethyl-orthosilicate
(TEOS) containing different fluorescent probes viz Hoechst 33258 (H258), Pyranine (Py), and 7-Azaindole (7-AI) in different
sols. Sols were prepared with addition of water, HCl and surfactant Triton X-100, and stored at room temperature (RT) and
low temperature (4 °C). The spectral characteristics have been compared for two different storage conditions as a function
of aging. The results of the present study clearly suggested that the internal environment of gels specifically the content
of water inside the pores of the sol–gel matrix can be controlled by storage at 4 °C as compared to RT. 相似文献
3.
A procedure is described for the immobilization of benzylpenicillin acylase from Escherichia coli within uniformly spherical, porous polyacrylamide gel beads. Aqueous solutions of the enzyme and sodium alginate and of acrylamide monomer, N,N'-methylene-bis-acrylamide, N,N,N,N'-tetramethylethylenediamine (TEMED) and sodium alginate are cooled separately, mixed, and dropped immediately into ice-cold, buffered calcium formate solution, pH 8.5, to give calcium alginate-coated beads. The beads are left for 30-60 min in the cold calcium formate solution for polyacrylamide gel formation. The beads are then treated with a solution of glutaraldehyde and the calcium alginate subsequently leached out with a solution of potassium phosphate. Modification of the native enzyme with glutaraldehyde results in a slight enhancement in the rate of hydrolysis of benzylpenicillin at pH 7.8 and 0.05M substrate concentration. The enzyme entrapped in porous polyacrylamide gel beads shows no measurable diffusional limitation in stirred reactors, catalyzing the hydrolysis of the substrate at a rate comparable to that of the glutaraldehyde-modified native enzyme. The immobilized enzyme preparation has been used in batch mode over 90 cycles without any apparent loss in hydrolytic activity. 相似文献
4.
M. Valach M. Navrátil V. Horváthová J. Zigová E. Šturdík E. Hrabárová P. Gemeiner 《Chemical Papers》2006,60(2):154-159
Ethanol-tolerant and thermo-tolerant yeast strain Saccharomyces cerevisiae C11-3 cells immobilized in calcium pectate and calcium alginate gels were used for ethanol fermentation in a three-reactor
system with a gradient temperature control. The fermentation process has been tested in a fixed-bed and a gas-lift arrangement.
The gas-lift system was more efficient due to a better mass transport between the phases. Abrasion was more evident in calcium
alginate particles, while calcium pectate beads were not significantly damaged. Two different concentrations of alginate were
tested and calcium pectate gel was demonstrated to be more suitable as an immobilization material in comparison with calcium
alginate due to its mechanical resistance and favourable diffusion parameters, providing an ethanol production of more than
7.5 g dm−3 h−1 over a period of 630 h. 相似文献
5.
Dominik L. Jürgen-Lohmann Christoph Nacke Raymond L. Legge Leonardo C. Simon 《Journal of Sol-Gel Science and Technology》2009,50(1):77-86
Sol–gels are seeing widespread interest as suitable materials for the immobilization of biomolecules in applications ranging
from optical coatings to specialty biocatalysts. Although there are numerous studies that have characterized these materials
in terms of their macroscopic properties, few studies have examined and correlated these properties at the microscopic level.
This study describes a spin-coating technique for the preparation of aluminum-supported sol–gel thin films containing immobilized
lysozyme [E.C. 3.2.1.17] that are suitable for chemical mapping using FTIR microscopy operating in reflectance mode. This
type of information can then be used to understand a variety of aspects of these materials which can be used for optimal engineering
of these materials, as well as insightful design and modeling. A data analysis method was developed to extract information
on chemical speciation and domain information on the materials from FTIR data matrices. Results from these studies indicated
that, contrary to what might be expected, these sol–gels are not homogeneous on the microscopic level. Instead, they are heterogeneous
in both the distribution of lysozyme and hydrophobic monomers at the scale investigated (20 μm resolution). The method described
here has promise in terms of providing a non-invasive approach of chemically mapping concentrations of proteinaceous and related
substances as well as chemical domains in situ in sol–gel thin films. 相似文献
6.
Effective diffusion coefficients (De) have been determined for lactose, glucose, galactose, and ethanol in calcium alginate gel with varying yeast cell concentration. The measurements have been performed in a diffusion cell, and the results evaluated with the quasisteady-state method. An ultrasonic meter was used for gel thickness determination with an accuracy of 1.5% and a new method for the reproducible preparation of gel plates was developed. It was found thatD e in pure alginate gel decreased to about 90% of the diffusivity in water and did not vary with alginate concentration.D e decreased considerably with increasing yeast cell concentration. For the solutes studied, the effective diffusion coefficient can be estimated according to the equationD e =D eo (1 - ?)/[1+(?/2)], whereD eo is the effective diffusivity in pure gel and ? is the volume fraction of yeast cells. 相似文献
7.
A crude preparation of Aspergillus niger β-glucosidase (27.5 cello-biase U/mg protein at 40°C, pH 5.0) was immobilized on
concanavalin A-Sepharose (CAS). The cellobiase activity of the immobilized enzyme was 1334 U/mg dried CAS or 108 U/mL CAS
gel. The β-glucosidase-CAS complex was entrapped within crosslinked propylene glycol alginate/bone-geletin gel spheres that
possessed between 0.67 and 2.35 cellobiase U/mL spheres, depending on their size. The effect of cellobiose concentration (10–300
mM) on the activity of native, immobilized, and gel-entrapped enzyme was determined. It was shown that concentrations of cellobiose
between 10 and 180 mM were not inhibitory to the entrapped enzyme, although inhibition was found to occur with the native
and immobilized enzyme. Exogenous ion addition was not necessary to maintain the structural integrity of the spheres, which
were stable for 4 d at 40°C. 相似文献
8.
Dominik L. Jürgen-Lohmann Christoph Nacke Leonardo C. Simon Raymond L. Legge 《Journal of Sol-Gel Science and Technology》2009,52(3):370-381
Although the use of silica sol–gels for protein entrapment has been studied extensively our understanding of the interactions
between the immobilization matrix and the entrapped biomolecules is still relatively poor. Non-invasive in situ spectroscopic
characterization is a promising approach to gain a better understanding of the fundamentals governing sol–gel immobilization
of biomolecules. This work describes the application of Fourier transform infrared (FTIR) microscopy to determine the influence
of modifying the sol–gel hydrophobicity, by varying the content of the organically modified precursor propyltrimethoxysilane
(PTMS), on the distribution and structure of three model proteins (lysozyme [EC 3.2.1.17], lipase [EC 3.1.1.3] and bovine
serum albumin (BSA)) in silica sol–gel thin films. FTIR analysis of the overall immobilized protein positional distribution
showed a Gaussian type distribution. FTIR microscopic mapping however, revealed that the spatial distribution of proteins
was heterogeneous in the sol–gel thin films. When this positional information provided by FTIR microscopy was taken into account,
areas of high protein concentration (clusters) were found and were not found to be homogeneously distributed. The shape of
these clusters was found to depend on the type of protein entrapped, and in some cases on the composition of the sol–gel.
Positional analysis of the distribution of the organically modified precursor PTMS in relation to the protein distribution
was also conducted. The localized concentration of PTMS was found to positively correlate with the protein concentration in
the case of lipase and negatively correlate in the case of lysozyme and BSA. These results indicate that lysozyme and BSA
concentration was higher in areas of low hydrophobicity, while lipase concentration was higher in areas of high hydrophobicity
within the sol–gel. Additionally, as determined by peak shape analysis of the amide I peak a higher PTMS content appeared
to conserve protein structure in high concentration clusters for lipase. In contrast, lysozyme and BSA, appeared to retain
their structure in high concentration clusters better at lower PTMS contents. A hypothesis speculating on the nature of the
hydrophobic/hydrophilic interactions between the proteins and the sol–gel domains as the reason for these differences is presented. 相似文献
9.
Sandu Peretz Otilia Cinteza 《Colloids and surfaces. A, Physicochemical and engineering aspects》2008,319(1-3):165-172
Biopolymers such as alginates are commonly used to remove the cationic contaminants from wastewaters. The major component of the alginate is the alginic acid, a linear, binary heteropolymer of β-d-mannuronate and -l-guluronate residues. In this study the fundamental aspects in the preparation of alginate beads and the effects of salt, sodium alginate concentrations and two cationic surfactants (dodecyltrimethylammonium bromide, cetyltrimethylammonium bromide) on the domains of binding isotherms were investigated. The alginate cross-link complexes with metal ions can exist either as homogeneous clear solutions or precipitates or as spherical beads. The applicability of the calcium and calcium–iron alginate gel beads for removal of some nitrophenols from aqueous solutions was studied. The sorption and kinetic experiments were conducted under different values of pH, initial concentration of nitrophenols and the amount of alginate gel beads. The removal efficiency of contaminant increases with the increasing of the pH and the quantity of alginate beads and decreases with the increasing of initial contaminant concentration. The uptake of nitrophenols occurs rapidly in the first 12 h, followed by a slow process that takes about 72 h. According to the egg-box model of gelation mechanism the cavities formed in the alginate gel capture the cationic contaminants. The adsorption equilibrium data obtained for nitrophenols derivatives at various pH and initial solid sorbent amount were applied to the two classical models, i.e. Langmuir and Freundlich, and the isotherm parameters were calculated. 相似文献
10.
Lidia Armelao Gregorio Bottaro Laura Bovo Chiara Maccato Eugenio Tondello Francesca Anselmi Sara Bersani Paolo Caliceti 《Journal of Sol-Gel Science and Technology》2011,60(3):352-358
The conjugation between probe biomolecules and inorganic nanoparticles has been studied. Three different and biologically
relevant proteins, bovine serum albumin (BSA), lysozyme (LSZ) and Ribonuclease A (RNAseA), have been selected as model systems
because of their difference in size and isoelectric point. Zinc oxide nanoparticles, synthesized via sol–gel, have been thoroughly
characterized by X-ray Photoelectron Spectroscopy, Scanning Electron Microscopy and X-ray Diffraction, and subsequently used
as platforms for immobilization of the biomolecules. The interaction of the three proteins with the ZnO surface was performed
in phosphate buffer solutions at pH 7.2 in order to mimic physiological fluids and was investigated through fluorescence experiments.
The obtained results indicate that conjugation of BSA, LZS and RNAseA on the oxide nanoparticles was mostly dictated by the
overall charge of the different proteins. Electrostatic bonds dominate the formation of the protein/ZnO conjugates, whereas
the size of the proteins seems to play a negligible role under the adopted experimental conditions. 相似文献
11.
Devika Sil Rimlee Deb Roy Sunirmal Jana Rabibrata Mukherjee Shyamal Kumar Bhadra Prasanta Kumar Biswas 《Journal of Sol-Gel Science and Technology》2011,59(1):117-127
Patterning of sol gel based silica and silica–titania films has been developed at room temperature by soft lithographic technique.
Corresponding metal alkoxides have been utilized for the preparation of precursor sols. Elastomeric stamps of polydimethylsiloxane
(PDMS) are used to emboss patterns of a master grating on the as-prepared silica and silica–titania films obtained by sol
gel process. Pressure-less capillary force lithography has been used to fabricate both 1-D and 2-D ordered structures of simple
stripe patterns. A modified solvent assisted lithography and micro-molding in capillaries yielded stable and high fidelity
1-D structures for silica and silica–titania films over a large area. 相似文献
12.
Takeo Saegusa 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):817-829
In this article I describe two of our discoveries. The first is the preparation of a transparent solid material composed of an organic polymer and silica gel. A novel material called a “hybrid” has successfully been prepared by the sol-gel reaction of ethyl orthosilicate in the presence of an organic polymer consisting of repeating units having an N-alkylamide group. The molecular-level dispersion of the organic polymer in the framework of silica gel has been established, which is due to the hydrogen-bond interaction between the organic polymer and silanol group of silica gel. The second discovery is the preparation of porous silica gel, which has been achieved by calcination of the organic polymer-silica gel hybrid at 600°C. Pore sizes ranging from 10 to 20 Å have been attained. A method of controlling pore size has been proposed. 相似文献
13.
The rate of gel growth for spherical ionotropic metal alginate gel complexes has been measured. The experimental results show that the stability of these complexes increases in the order Mn相似文献
14.
J.-M. Nedelec L. Courtheoux E. Jallot C. Kinowski J. Lao P. Laquerriere C. Mansuy G. Renaudin S. Turrell 《Journal of Sol-Gel Science and Technology》2008,46(3):259-271
Several examples of sol–gel preparation of doped materials are taken to illustrate the various situations where the doping
elements are responsible for the main function of the material or govern its structure. Other examples are used to illustrate
that sometimes unexpected effects can be observed like structural modification and the appearance of new properties. Rare
earth doped scintillators demonstrate higher homogeneity for materials prepared via sol–gel chemistry when compared with classical
solid state reaction. The XRD study of rare earth doped orthoborates shows that doping can affect the vaterite to calcite
phase transition observed in these compounds. A Raman spectroscopic study has been performed on doped silica xerogels and
it has been shown that doping ions can modify greatly the densification process in these amorphous materials. Finally, it
has been evidenced that sol–gel chemistry allows the preparation of bioactive ceramics with enhanced properties. In particular
Zn-doped HAP with anti inflammatory properties has been prepared and Sr-doped bioactive glasses have demonstrated superior
in-vitro bioactivity as evidenced by PIXE-RBS study. 相似文献
15.
The catalase (fromAspergillus niger) has been immobilized by a chemical method on the pous SiO2 modified with γ-aminopropyltrietoxysilane, followed with glutaraldehyde and by a physical method in alginate and γ-carrageenan
gel. Optimum support:enzyme ratios and pH values were determined for modified SiO2 in a series of immobilization reactions of catalase in the presence of the crosslinking agent glutaraldehyde, and for alginate
and γ-carrageenan in the presence of hemoglobin and bovine serum albimine. pH and temperaturedependent activity variations
and the stability properties of immobilized catalase preparations were investigated. Rate constants for H2O2 decomposition and catalase deactivation were determined. The decomposition rate of H2O2 used in the cold pasteurizatioan of milk were investigated in a discontinuous batch type reactor system. Activity half-lives
of immobilized catalase were determined. 相似文献
16.
Formation of hybrid gels from an aqueous mixture of alginate and alkoxysilanes has been applied to immobilization of whole cells ofPichia pastoris catalyzing oxidation of benzyl alcohol in organic solvent. The amount of benzaldehyde produced after a prolonged reaction period was 1.2 and 1.8 times greater with the hybrid gels of alginate + silicate and alginate + methyl-substituted silicate, respectively, than with the alginate single gel. This was ascribed to a facilitated release rate of aldehyde, which acted as a strong inhibitor against the enzyme alcohol oxidase, from the inside of the cells to organic medium through hydrophobic gel matrix. 相似文献
17.
Mário A. P. Nunes Hélder Vila-Real Pedro C. B. Fernandes Maria H. L. Ribeiro 《Applied biochemistry and biotechnology》2010,160(7):2129-2147
A synthetic polymer, polyvinyl alcohol (PVA), a cheap and nontoxic synthetic polymer to organism, has been ascribed for biocatalyst
immobilization. In this work PVA–alginate beads were developed with thermal, mechanical, and chemical stability to high temperatures
(<80 °C). The combination of alginate and bead treatment with sodium sulfate not only prevented agglomeration but produced
beads of high gel strength and conferred enzyme protection from inactivation by boric acid. Naringinase from Penicillium decumbens was immobilized in PVA (10%)–alginate beads with three different sizes (1–3 mm), at three different alginate concentrations
(0.2–1.0%), and these features were investigated in terms of swelling ratio within the beads, enzyme activity, and immobilization
yield during hydrolysis of naringin. The pH and temperature optimum were 4.0 and 70 °C for the PVA–alginate-immobilized naringinase.
The highest naringinase activity yield in PVA (10%)–alginate (1%) beads of 2 mm was 80%, at pH 4.0 and 70 °C. The Michaelis
constant (K
Mapp) and the maximum reaction velocity (V
maxapp) were evaluated for both free (K
Mapp = 0.233 mM; V
maxapp = 0.13 mM min−1) and immobilized naringinase (K
Mapp = 0.349 mM; V
maxapp = 0.08 mM min−1). The residual activity of the immobilized enzyme was followed in eight consecutive batch runs with a retention activity
of 70%. After 6 weeks, upon storage in acetate buffer pH 4 at 4 °C, the immobilized biocatalyst retained 90% of the initial
activity. These promising results are illustrative of the potential of this immobilization strategy for the system evaluated
and suggest that its application may be effectively performed for the entrapment of other biocatalysts. 相似文献
18.
Neutron diffraction studies of hydrogen positions in small molecules of biological interest at Trombay have provided valuable
information that has been used in protein and enzyme structure model-building and in developing hydrogen bond potential functions.
The new R-5 reactor is expected to provide higher neutron fluxes and also make possible smallangle neutron scattering studies
of large biomolecules and bio-aggregates. In the last few years infrastructure facilities have also been established for macromolecular
x-ray crystallography research. Meanwhile, the refinement of carbonic hydrases’ and lysozyme structures have been carried
out and interesting results obtained on protein dynamics and structure-function relationships. Some interesting presynaptic
toxin phospholipases have also been taken up for study. 相似文献
19.
Pooja Sawant S. Varma B. N. Wani S. R. Bharadwaj 《Journal of Thermal Analysis and Calorimetry》2012,107(1):189-195
In this article, the role of the preparation route and calcinations temperature on the thermal expansion and conductivity
of BaCe0.8Y0.2O3−δ (BCY) has been studied. In particular, the samples were synthesized by means of the solid-state reaction and by a sol–gel
route. BCY has been suggested as proton conducting electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs).
Proton conductivity strongly depends on the densification of the material as well as the crystal structure, which is generally
influenced by the preparation procedure. It was found that a single phase material could be achieved at 1000 °C for the samples
prepared through the sol–gel route with ~96% packing density. In case of ceramic route, single phase could be obtained at
higher temperatures (1200 °C) and does not lead to good density values. The ceramic synthesis produces BCY material in cubic
symmetry where as the gel–citrate complexation route leads to homogenous orthorhombic BCY. The conductivity measurements of
sample synthesized by two different routes were investigated by means of impedance spectroscopy and electron microscopy. A
comparative study of thermal expansion behavior of BCY synthesized by different route was carried out. 相似文献
20.
Shape-controlled production of biodegradable calcium alginate gel microparticles using a novel microfluidic device 总被引:1,自引:0,他引:1
Liu K Ding HJ Liu J Chen Y Zhao XZ 《Langmuir : the ACS journal of surfaces and colloids》2006,22(22):9453-9457
In this paper we describe a novel method of manufacturing shape-controlled calcium alginate gel microparticles in a microfluidic device. Both manufacturing shape-controlled microparticles and synthesizing hydrogel microparticles could be performed simultaneously in the microfluidic device. The novel microfluidic device comprised of two individual flow-focusing channels and a synthesizing channel was successfully applied as a continuous microfluidic reactor to synthesize gel microparticles with size and shape control. By passive control based on the microchannel geometric confinement and liquid-phase flow rates, we succeeded in producing monodisperse sodium alginate microparticles with diverse shapes (such as plugs, disks, microspheres, rods, and threads) in the flow-focusing channels of the microfluidic device. The shape and size of the sodium alginate microparticles could be tuned by adjusting the flow rates of the various streams. Further stages of the chemical reaction could be initiated by mixing sodium alginate microparticles and calcium chloride (CaCl2) solution in the synthesizing channel. The shapes of the sodium alginate microparticles could be permanently preserved by the synthesis of calcium alginate gel microparticles. The preparation conditions of size- and shape-controlled calcium alginate microparticles and influence factors were studied. 相似文献