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31.
Aho AJ Hautamäki M Mattila R Alander P Strandberg N Rekola J Gunn J Lassila LV Vallittu PK 《Cell and tissue banking》2004,5(4):213-221
The aim of this study was to describe and evaluate the significance of a porous surface with bioactive glass granules (S53P4)
covering an artificial bulk material based on polymethylmetacrylate (PMMA) and fibre-reinforced composite (FRC) technology.
Effort was focused particularly on characters of the porous surface and biomechanical properties of the material in vitro, and test in vivo the implant in reconstruction in an experimental long bone segment defect model. The defect, 10 mm in length, created in
the shaft of rabbit tibia, was reconstructed by the implant and fixed by intramedullary K-wires. The implant was incorporated
within 4 weeks by new bone growth from the host bone covering particularly its posterior surface and cortex/implant junctions
with bridging trabecular bone. Later, at 8 weeks, new bone was found also at the cortex/implant interface and in the medullary
canal of the implant. Histometric measurements revealed direct bone/implant surface contact in 34% at the interface. Bioactive
glass granules in the porous surface evoked the most direct contact with bone. The implants manufactured from PMMA only served
as a control group, and showed significantly lower osteoconductive properties. Biomechanical measurements in vitro of fibre-reinforced PMMA specimens revealed values for bending strength and the flexural modulus to match them to human bone.
This artificial bulk bone material based on PMMA/FRC technology seems to have proposing properties to be used as a bone substitute
on load-bearing conditions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
32.
The processes by which protein side chains reach equilibrium during a folding reaction are investigated using both lattice and all-atom simulations. We find that rates of side-chain relaxation exhibit a distribution over the protein structure, with the fastest relaxing side chains located in positions kinetically important for folding. Traversal of the major folding transition state corresponds to the freezing of a small number of side chains, belonging to the folding nucleus, whereas the rest of the protein proceeds toward equilibrium via backbone fluctuations around the native fold. The postnucleation processes by which side chains relax are characterized by very slow dynamics and many barrier crossings, and thus resemble the behavior of a glass. 相似文献
33.
Evaluation of effective diffusion coefficient and intrinsic kinetic parameters on azo dye biodegradation using PVA-immobilized cell beads 总被引:3,自引:0,他引:3
An immobilized mixed culture (Aeromonas hydrophila, Comamonas testosteroni, and Acinetobacter baumannii) was prepared by entrapment into phosphorylated polyvinyl alcohol (PVA) gel beads. The unsteady-state diffusion mechanism in a gel bead was applied to estimate the effective diffusion coefficients (D(e)) and the partition coefficients (K(p)) of azo dye. In addition, a simple method was developed to determine the intrinsic kinetic parameters of immobilized cells from observed reaction rates and the intrinsic kinetic parameters were then verified by fitting the experimental data into the reaction-diffusion model in a batch reactor running at a well-stirred state. The calculated effectiveness factor (eta(cal)) approached unity at Thiele modulus (Phi) < 0.3 (i.e., d(p) < 0.475 mm). The experimental effectiveness factor (eta(exp)) was in the range of 0.71-0.45 for a corresponding sphere diameter (d(p)) of 1.91 +/- 0.16 to 4.43 +/- 0.07 mm at an initial dye concentration of 200 mg/L. The results show that intraparticle diffusion resistance has a significant effect on the azo dye biodegradation rate. 相似文献
34.
Specific protein dynamics near the solvent glass transition assayed by radiation-induced structural changes 总被引:1,自引:0,他引:1 下载免费PDF全文
Weik M Ravelli RB Silman I Sussman JL Gros P Kroon J 《Protein science : a publication of the Protein Society》2001,10(10):1953-1961
The nature of the dynamical coupling between a protein and its surrounding solvent is an important, yet open issue. Here we used temperature-dependent protein crystallography to study structural alterations that arise in the enzyme acetylcholinesterase upon X-ray irradiation at two temperatures: below and above the glass transition of the crystal solvent. A buried disulfide bond, a buried cysteine, and solvent exposed methionine residues show drastically increased radiation damage at 155 K, in comparison to 100 K. Additionally, the irradiation-induced unit cell volume increase is linear at 100 K, but not at 155 K, which is attributed to the increased solvent mobility at 155 K. Most importantly, we observed conformational changes in the catalytic triad at the active site at 155 K but not at 100 K. These changes lead to an inactive catalytic triad conformation and represent, therefore, the observation of radiation-inactivation of an enzyme at the atomic level. Our results show that at 155 K, the protein has acquired--at least locally--sufficient conformational flexibility to adapt to irradiation-induced alterations in the conformational energy landscape. The increased protein flexibility may be a direct consequence of the solvent glass transition, which expresses as dynamical changes in the enzyme's environment. Our results reveal the importance of protein and solvent dynamics in specific radiation damage to biological macromolecules, which in turn can serve as a tool to study protein flexibility and its relation to changes in a protein's environment. 相似文献
35.
Calcium-alginate beads were found to bind a variety of enzymes in a nonspecific fashion. However, alpha amylases from porcine pancreas, Bacillus subtilis (BAN 240L) and wheat germ bound at a significant level and B. subtilis and wheat germ amylases could be eluted with 1M maltose. The wheat germ alpha amylase could be purified 45 fold with 70% recovery. The SDS - PAGE pattern showed significant purification by this single step strategy. 相似文献
36.
K D Chapatwala G R V Babu O K Vijaya K P Kumar J H Wolfram 《Journal of industrial microbiology & biotechnology》1998,20(1):28-33
Pseudomonas putida utilizes cyanide as the sole source of carbon and nitrogen. Agar, alginate, and carrageenan were screened as the encapsulating
matrices for P. putida. Alginate-immobilized cells of P. putida degraded sodium cyanide (NaCN) more efficiently than non-immobilized cells or cells immobilized in agar or carrageenan. The
end products of biodegradation of cyanide were identified as ammonia (NH3) and carbon dioxide (CO2). These products changed the medium pH. In bioreactors, the rate of cyanide degradation increased with an increase in the
rate of aeration. Maximum utilization of cyanide was observed at 200 ml min−1 of aeration. Immobilized cells of P. putida degraded cyanides, cyanates and thiocyanates to NH3 and CO2. Use of Na[14C]-CN showed that 70% of carbon of Na[14C]-CN was converted into 14CO2 and only 10% was associated with the cell biomass. The substrate-dependent kinetics indicated that the K
m and V
max values of P. putida for the substrate, NaCN were 14 mM and 29 nmol of oxygen consumed mg protein−1 min−1 respectively.
Received 29 January 1996/ Accepted in revised form 19 September 1997 相似文献
37.
《Harmful algae》2015
The filamentous cyanobacterium Planktothrix rubescens produces secondary metabolites called microcystins (MC) that are potent toxins for most eukaryotes, including zooplankton grazers, cattle and humans. P. rubescens occurs in many deep and thermally stratified lakes throughout Europe. In Lake Zurich (Switzerland), it re-appeared in the 1970s concomitant with decreasing eutrophication. Since then, P. rubescens has become the dominant species in this major drinking water reservoir, where it forms massive metalimnetic blooms during late summer. These cyanobacteria harbor subpopulations of non-MC producers, but little is known about the environmental factors affecting the success of such genotypes. The non-MC-producing subpopulation of P. rubescens was studied using a quantitative real-time PCR (qPCR) assay on the MC synthetase (mcy) gene cluster that targets a deletion on the mcyH and mcyA genes, which inactivates MC biosynthesis. Two complementary qPCR assays were used to assess the total population abundance (based on the 16S rDNA gene) and the mcy gene copy number (based on a conserved region in the adenylation domain of the mcyB gene). The objective was to evaluate the seasonal patterns of the share of non-MC-producing filaments in the total P. rubescens population. The mcyHA mutants were present in low proportions (up to 14%) throughout the year. Their highest relative abundances occurred during the winter mixis, when total concentrations of P. rubescens were minimal. The MC deficient mutants seemed to better survive in sparse populations, possibly because of lower grazing pressure and a consequently reduced need for MC-mediated protection. Alternatively, the mutants might cope better with the sub-optimal, stressful pressure and light conditions during the winter mixis. Altogether, our results suggest that subtle trade-offs might seasonally determine the proportions of non-MC producers within P. rubescens populations. 相似文献
38.
Shannon Bunker Joanna Holeniewska Sauparnika Vijay Annegret Dahlmann-Noor Peng Khaw Yin-Shan Ng David Shima Richard Foxton 《Journal of visualized experiments : JoVE》2015,(96)
Progress in understanding the pathophysiology, and providing novel treatments for glaucoma is dependent on good animal models of the disease. We present here a protocol for elevating intraocular pressure (IOP) in the rat, by injecting magnetic microspheres into the anterior chamber of the eye. The use of magnetic particles allows the user to manipulate the beads into the iridocorneal angle, thus providing a very effective blockade of fluid outflow from the trabecular meshwork. This leads to long-lasting IOP rises, and eventually neuronal death in the ganglion cell layer (GCL) as well as optic nerve pathology, as seen in patients with the disease. This method is simple to perform, as it does not require machinery, specialist surgical skills, or many hours of practice to perfect. Furthermore, the pressure elevations are very robust, and reinjection of the magnetic microspheres is not usually required unlike in some other models using plastic beads. Additionally, we believe this method is suitable for adaptation for the mouse eye. 相似文献
39.
Laura Zuccaro Cinzia Tesauro Barbara Cerroni Alessio Ottaviani Birgitta Ruth Knudsen Kannan Balasubramanian Alessandro Desideri 《Analytical biochemistry》2014
A high-sensitivity assay has been developed for the detection of human topoisomerase I with single molecule resolution. The method uses magnetic sepharose beads to concentrate rolling circle products, produced by the amplification of DNA molecules circularized by topoisomerase I and detectable with a confocal microscope as single and discrete dots, once reacted with fluorescent probes. Each dot, corresponding to a single cleavage–religation event mediated by the enzyme, can be counted due to its high signal/noise ratio, allowing detection of 0.3 pM enzyme and representing a valid method to detect the enzyme activity in highly diluted samples. 相似文献
40.
Sirley V. Pereira Germán A. MessinaJulio Raba 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2010,878(2):253-257
In this paper, we have developed and characterized a microfluidic magnetic immunosensor coupled to a gold electrode for the rapid and sensitive quantification of human serum IgG antibodies to Helicobacter pylori. This microorganism cause peptic ulcers and chronic gastritis, affecting around the 10% of the world population. The sensor was completely automated and the antibodies detection in serum samples was carried out using a non-competitive immunoassay based on the use of purified H. pylori antigens that are immobilized on magnetic microspheres 3-aminopropyl-modified. The magnetic microbeads were injected into microchannel devices and manipulated for an external removable magnet. The IgG antibodies in human serum sample are allowed to react immunologically with the immobilized antigens, and the bounded antibodies are quantified by alkaline phosphatase (AP) enzyme-labeled second antibodies specific to human IgG. The p-aminophenyl phosphate (p-APP) was converted to p-aminophenol (p-AP) by AP and an electroactive product was detected on gold layer electrode at 0.250 V. The response current obtained from the product of enzymatic reaction is directly proportional to the activity of the enzyme and, consequently, to the amount of IgG antibodies to H. pylori in serum samples. The electrochemical detection can be done within 1 min and total assay time was 25 min. The calculated detection limits for electrochemical detection and the ELISA procedure were 0.37 and 2.1 U mL−1, respectively, and the within- and between-assay coefficients of variation were below 5%. Our results indicate the potential usefulness of our fabricated microbiochip for the early assessment of human serum immunoglobulin G (IgG) antibodies to H. pylori. 相似文献