1978 - graduated from the Institute of Chemical Technology, Prague 1984 - PhD degree in biochemistry (Institute of Chemical Technology, Prague) 1993 - Assoc. Prof. degree in biochemistry (Institute of Chemical Technology, Prague) 2001 - DSc degree in biochemistry 2002 - Editor-in-Chief of the journal "BioMagnetic Research and Technology"
Abstract: A magnetically responsive composite material based on lignocellulose and magnetic nanoparticles has been prepared. Spruce sawdust was magnetically modified by contact with water-based magnetic fluid stabilised with perchloric acid. Electron spin resonance and transmission electron microscopy measurements indicated the presence of both individual magnetic nanoparticles and clusters precipitated on the surface of sawdust particles. The material prepared was used to study the adsorption of selected water-soluble organic dyes. The adsorption isotherms followed Langmuir, generalised Freundlich, generalised Langmuir, and Langmuir-Freundlich adsorption patterns. Maximum adsorption capacities for acridine orange, Bismarck brown, crystal violet, malachite green, methyl green, Nile blue, safranin 0 and Saturn blue LBRR 200 ranged between 34 and 59 mg g(-1) dry adsorbent. A change in pH value can increase the dye adsorption. Ferrofluid-modified sawdust is thus an interesting material for further study and potential applications.
Abstract: Two magnetic macroporous, cellulose cation exchangers (Iontosorb MG CM 100 and Iontosorb MG SHP 100) were used for one-step isolation of lysozyme from native, undiluted hen egg white. Highly purified lysozyme (purity >96%) with specific activity similar to that of commercial lysozyme preparations was obtained in both cases. Carboxymethyl-based cation exchanger exhibited substantially higher capacity for lysozyme; maximum adsorption capacity was 138 mg/mL. The lysozyme-depleted egg white can be used in the same way as the routinely used egg white because no dilution of this material was necessary during the purification process.
Abstract: Magnetic solid phase extraction (MSPE) is proposed as a simple and fast method for the preconcentration of free middle oxyethylated nonylphenols (NPs) from water. Middle oxyethylated NPs were extracted by MSPE from different water samples (10 and 500 ml samples of distilled, potable, well, river and pond water in concentrations of 30 and 0.6 mu g ml(-1)) using magnetically modified polyphenyleneoxide, Tenax TA and Tenax GR as magnetic adsorbents. Recoveries were 80-100% and relative standard deviations were less than 10%. (C) 2006 Elsevier B.V. All rights reserved.
Abstract: Spruce sawdust (lignocellulose material) was magnetically modified after contact with a water-based magnetic fluid containing maghemite nanoparticles. This procedure allows one to use the prepared material as a new magnetic affinity adsorbent in magnetic separation techniques. The magnetic sawdust was investigated by means of electron spin resonance spectroscopy and conventional magnetic methods over the temperature range 4-300 K. The experimental results clearly show that the magnetic behaviour of the sample is determined by two distinct magnetic contributions. One of them is connected to the presence of isolated single domain maghemite nanoparticles of similar to 11 nm in diameter, which exhibit superparamagnetic behaviour at T > 280 K. The other one is related to the presence of agglomerates of particles coupled by magnetic dipolar interactions.
Abstract: Fodder yeast (Kluyveromyces fragilis) cells were magnetically modified by a contact with the water-based magnetic fluid in order to prepare a new type of magnetically responsive biocomposite material. This procedure enabled a simple separation of modified cells by means of commercially available magnetic separators or strong permanent magnets. It allows using the prepared material as a new inexpensive magnetic affinity adsorbent for the removal of water-soluble dyes. Magnetically modified cells were characterized by means of magnetic and microscopy methods. Both isolated magnetic nanoparticles and aggregates of particles were present on the cell surface. The prepared material displayed a superparamagnetic behavior at room temperature, with a transition to a blocked state at T-B similar to 180 K for the applied magnetic field H = 50 Oe. Seven dyes (crystal violet, amido black 10B, congo red, Saturn blue LBRR, Bismarck brown, acridine orange and safranin O) were used to study the adsorption process. The dyes adsorption could be described with the Langmuir isotherm. The maximum adsorption capacities ranged between 29.9 (amido black 10B) and 138.2 (safranin O) mg of dye per g of dried magnetically modified cells. (C) 2006 Elsevier Inc. All rights reserved.
Abstract: Brewer's yeast (bottom yeast, Saccharomyces cerevisiae subsp. uvarum) cells were magnetically modified using water based magnetic fluid stabilized perchloric acid. The magnetically modified yeast cells were characterized by scanning electron microscopy (SEM) and electron spin resonance (ESR). Hg2+ biosorption-desorption properties of magnetically modified yeast cells from synthetic solutions were utilized in batch system. The biosorption process was fast; 80% of biosorption occured within 60 min and equilibrium was achieved at around 90 min. The maximum Hg2+ biosorption capacity was obtained to be 114.6 mg/g at 35 degrees C. The suitability of the Langmuir, Freundlich and Redlich-Peterson adsorption models to the equilibrium data was investigated for mercury-biosorbent system. The results were well fitted to the Langmuir isotherm. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. Results suggest that chemisorption processes could be the rate-limiting step in the biosorption process. The yeast biomass can be easily regenerated by 0.1 M HNO3 with higher effectiveness. Biosorption of heavy metal ions from artificial wastewater was also studied. The biosorption capacities are 29.9 mg/g for Cu2+, 76.2 mg/g for Hg2+, 14.1 mg/g for Ni2+ and 11.8 mg/g for Zn2+. (c) 2006 Elsevier B.V. All rights reserved.
Abstract: Brewer's yeast (bottom yeast, Saccharomyces cerevisiae subsp. uvarum) cells were magnetically modified using water based magnetic fluid stabilized with perchloric acid. Magnetically modified yeast cells efficiently adsorbed various water soluble dyes. The dyes adsorption can be described by the Langmuir adsorption model. The maximum adsorption capacity of the magnetic cells differed substantially for individual dyes; the highest value was found for aniline blue (approx. 220 mg per g of dried magnetic adsorbent).
Abstract: Spruce sawdust was magnetically modified after contact with water-based magnetic fluid. Magnetic and microscopy characterization of the prepared material was performed. Magnetic sawdust was efficiently used for the adsorption of water-soluble organic dyes (maximum adsorption capacity reached 50mg g(-1)) and purification of hen egg white lysozyme (96% purity achieved in a single step). (c) 2005 Elsevier B.V. All rights reserved.
Abstract: Magnetic solid phase extraction was tested for the preconcentration of non-ionic surfactants based on oxyethylated nonylphenol, aliphatic alcohols and hydrogenated fatty acid methyl esters from water. Magnetic hydrophobic adsorbents exhibited the best extraction characteristics. Surfactants with the middle oxyethylation level were extracted efficiently while the extraction of surfactants with low and high oxyethylation levels was very low. (c) 2005 Elsevier B.V. All rights reserved.
Abstract: In this study, the interaction of DMSA-coated magnetite nanoparticles (5 and 10 nm core-size) with Saccharomyces cerevisae was investigated using magnetic resonance (MR) and transmission electron microscopy (TEM). The TEM micrographs revealed magnetite nanoparticles attached externally to the cell wall. The MR data support the strong interaction among the nanoparticles supported by the cells. A remarkable shift in the resonance field was used as signature of particle attachment to the cell wall. (C) 2003 Elsevier B.V. All rights reserved.
Abstract: Isolation and separation of specific molecules is used in almost all areas of biosciences and biotechnology. Diverse procedures can be used to achieve this goal. Recently, increased attention has been paid to the development and application of magnetic separation techniques, which employ small magnetic particles. The purpose of this review paper is to summarize various methodologies, strategies and materials which can be used for the isolation and purification of target proteins and peptides with the help of magnetic field. An extensive list of realised purification procedures documents the efficiency of magnetic separation techniques.
Abstract: Spherical magnetic alginate microparticles (25-60 mum in diameter) were prepared using the microemulsion system, with water-saturated 1-pentanol as the organic phase. The limited solubility of 1-pentanol in water enabled simple removal of the organic solvent from the prepared beads with water solution. The prepared alginate microparticles were used as magnetic affinity adsorbents for specific purification of alpha-amylases. Enzyme activity was eluted by 1.0 M maltose. alpha-Amylases from Bacillus amyloliquefaciens and porcine pancreatic acetone powder were purified 9- and 12-fold with 88 and 96% activity recovery, respectively. (C) 2003 Elsevier B.V. All rights reserved.
Abstract: This paper shows that Saccharomyces cerevisiae efficiently interact with magnetite-based ionic magnetic fluid, leading to the formation of magnetically labeled cells which could be easily separated from the system using an appropriated field-gradient-based magnetic separator. Scanning and transmission electron microscopies were used to investigate the interaction of Saccharomyces cerevisiae cells with magnetite nanoparticles. The high-resolution microscopy data suggested that particle incorporation occurs via an active process. Further, the microscopy data shows that the particles did not reach the cell cytoplasm, staying in the periplasmatic space.
Abstract: A simple procedure for the detection of low concentrations of malachite green and crystal violet in wa ter is presented. The dyes were preconcentrated from 1000 ml of water samples with magnetic solid phase extraction using magnetic affinity adsorbent (magnetite with immobilized copper phthalocyanine dye). Due to the magnetic properties of the adsorbent the preconcentration process can also be performed in water samples containing suspended solids, After elution of the captured dyes, their presence in eluates was detected spectrophotometrically. Concentrations of both clues in the range 0.5-1.0 mug l(-1) of water could be reproducibly detected. The dyes can be detected not only in potable water, but also in river ones. (C) 2001 Elsevier Science Ltd. All rights reserved.
Abstract: Magnetic nanoparticles represent an interesting material both present in various living organisms and usable for a variety of bioapplications. This review paper will summarize the information about biogenic magnetic nanoparticles, the ways to synthesize biocompatible magnetic nanoparticles and complexes containing them, and the applications of magnetic nanoparticles in various areas of biosciences and biotechnologies.
Abstract: Ferrofluid-modified trypsin has been used for the detection and determination of selected xenobiotics that inhibit trypsin activity. The procedure is useful especially when colored samples or samples containing suspended solid impurities are to be assayed. Ferrofluid-modified trypsin was inhibited by Ag+ and Pb2+, selected dyes (safranin, thionin), bacitracin and 4-aminobenzamidine. Enzymes immobilized on magnetic particles can form a basis of new automated assay procedures for the determination of xenobiotics.
Abstract: Aims: Raw fruits and vegetables have been increasingly associated with human infections caused by Shiga toxin-producing Escherichia coli. This study evaluates the isolation and detection of E. coli O26, O111 and O157 from vegetable samples using immunomagnetic particles. Methods and Results: Standard cultivation and immunomagnetic separation (IMS) procedures were compared. It was found that immunomagnetic particles could efficiently concentrate E. coli cells, detecting significantly more bacteria than with standard cultivation procedures. Conclusions: Bacteria were detected in 93-100% of the inoculated samples using the IMS procedure, but only 36-93% samples tested by standard cultivation procedures were found to be positive. Significance and Impact of the Study: The results indicate that E. coli O26, O111 and O157 immunomagnetic particles can be a very useful and efficient tool for the detection of E. coli strains in raw vegetables, and could probably be used with samples of animal origin.
Abstract: A Davis tube (a matrix-free, flow-through magnetic separator used mainly in mineral processing) has been tested for separation of magnetic affinity biopolymer adsorbents from larger volumes of suspensions. Both magnetic chitosan and magnetic cross-linked erythrocytes could be efficiently separated from litre volumes of suspensions. Up to 90% adsorbent recovery was achieved under optimised separation conditions.
Abstract: New magnetic adsorbents for batch isolation and removal of various proteolytic enzymes were prepared by glutaraldehyde cross-linking of bovine, porcine and human erythrocytes in the presence of fine magnetic particles. Trypsin, chymotrypsin, alkaline bacterial protease and proteases present in various commercial enzyme preparations were efficiently adsorbed on these adsorbents; on the contrary, proteins without proteolytic activity were not adsorbed. (C) 2001 Elsevier Science B.V. All rights reserved.
Abstract: Flat magnetic separator was used to separate magnetic bioaffinity adsorbents from litre volumes of suspensions. Both magnetic cross-linked erythrocytes and magnetic chitosan were efficiently separated; at least 95% adsorbent recovery was achieved at maximum flow rate (1680 ml min(-1)). Using this system low amounts of trypsin were concentrated from large sample volumes using magnetic erythrocytes as affinity adsorbent.
Abstract: A one-step procedure for a partial purification of Solanum tuberosum tuber lectin has been developed. Lectin from tuber extract or from potato wastewater was adsorbed to magnetic chitosan particles and eluted with low pH buffer. The specific activity of separated lectin increased 13 times during the purification process and the recovery was 50%.
Abstract: Magnetic solid-phase extraction is a new procedure for the preconcentration of target analytes from large volumes based on the use of magnetic or magnetizable adsorbents. In the experiments reactive copper phthalocyanine dye attached to silanized magnetite, and magnetic charcoal were used as adsorbents and selected organic dyes were used as analytes. Up to 460-fold enrichment of analytes was observed. (C) 1999 Elsevier Science B.V. All rights reserved.
Abstract: A procedure for the determination of proteolytic activity with dyed magnetic gelatine as an insoluble chromolytic substrate is described. The magnetic nature of the substrate enables magnetic separation of unhydrolysed substrate from the hydrolysed dyed peptide fragments. Such type of substrates could enable the development of new automated protease assays based on the principle of Flow Injection Analysis (FIA).
Abstract: The gut of the adult soft ticks Ornithodoros moubata displays high lytic activity against the bacteria Micrococcus luteus. The activity differed in the range of two orders of magnitude among individual animals and increased on average 4 fold during the first week following ingestion. In homogenates of first instar nymphs the activity was much lower increasing exponentially as nymphs neared the first molt. The protein responsible for this activity was purified out of gut contents of adult ticks by means of affinity adsorption on magnetic-chitin followed by two chromatography steps on cation exchange FPLC column MonoS. The homogeneous active protein has a mass of 14006+/-20 Daltons as determined by MALDI-TOF mass spectrometry. The N-terminal amino-acid sequence of this protein is K-V-Y-D-R-C-S-L-A-S-E-L-R with the highest similarity to the lysozyme from liver of rainbow trout and to lysozymes from digestive tracts of several mammals. The motif DRCSLA is specific for the digestive lysozymes of several dipteran insects. Based on this evidence, we have identified the protein as the tick gut lysozyme. The tick gut lysozyme has a pi near 9.7 and retains its full activity after treatment at 60 degrees C for 30 minutes. The pH optimum of the tick lysozyme was in the range from pH 5-7. Only marginal activity could be detected at pH>8 which raises the question about the function of lysozyme in antibacterial defense in the environment of the tick gut. (C) 1999 Elsevier Science Ltd. All rights reserved.
Abstract: Magnetic separation is an emerging technology using magnetism, sometimes in combination with conventional separation or identification methods, to purify cells, cell organelles and biologically active compounds (nucleic acids, proteins, xenobiotics) directly from crude samples. Several magnetic separation procedures have been developed to isolate target cells specifically. The purpose of this short review is to summarize various methodologies, strategies and materials which can be employed for the selection and separation of target cells with the help of magnetic field and thus to help the novices in this field to be able to orient themselves in vast amount of literature available. Immunomagnetic separations employing specific antibodies to label the target cells represent the most often used approach and are discussed in detail. (C) 1999 Elsevier Science BN. All rights reserved.
Abstract: A short review of possible applications of magnetic separation, labelling and targeting techniques in biochemistry and biotechnology (including environmental technology) is presented. These techniques, employing a variety of magnetic sorbents, carriers and modifiers, can be used for the immobilization, isolation, modification, detection, determination and removal of a variety of biologically active compounds, xenobiotics, cellular organelles and cells, both in the laboratory and industrial scale.
Notes: Hafeli, U xD;International Conference on Scientific and Clinical Applications of Magnetic Carriers xD;SEP 05-07, 1996 xD;ROSTOCK, GERMANY
Abstract: Two types of magnetic biosorbent were prepared by novel protocols from epichlorhydrin-cross-linked Saccharomyces cerevisiae cell walls and their biosorption characteristics were compared to those of non-magnetic cell walls. The magnetic biosorbents I and II were capable of binding Cu2+ maximally to 225 and 50 mu mol/g, Cd2+ to 90 and 25 mu mol/g and Ag+ to 80 and 45 mu mol/g respectively. These values compare with 400, 125 and 75 mu mol/g, respectively, for non-magnetic cell walls.
Abstract: Magnetic charcoal was prepared by entrapment of fine charcoal particles into the structure of magnetic iron oxides. This adsorbent can efficiently adsorb a variety of organic compounds. For the adsorption experiments water soluble organic dyes belonging to the triphenylmethane, heteropolycyclic and azodye groups were used as model compounds. Maximum adsorption capacities ranged between 10 and 20 mg of dyes per 1 cm(3) of the sedimented adsorbent; this corresponds to 132.5-265 mg of dyes per 1 g of the dried adsorbent.
Abstract: Magnetite particles bearing covalently immobilized copper phthalocyanine dye (''blue magnetite'') were prepared and used for the isolation and/or removal of polycyclic dyes from water solutions and suspensions. Binding of these polycyclic dyes occurs by a chemical, equilibrated, and saturatable mechanism, following the Langmuir adsorption model. Nonspecific adsorption of dyes having nonplanar molecular structure was low. The values of maximum adsorption capacity were calculated. The bound dyes were only partially eluted from the adsorbent with methanol and methanol-concentrated ammonia solution (50/1, v/v).
Abstract: Two simple and rapid procedures for removal of fine magnetic particles from large volumes of suspensions are described. One of them is based on the flow of magnetic suspension through the modified glass pipette placed on a flat magnet, in the second one the magnetic suspension is poured on a plastic film covering the magnet.
Abstract: A short review about the possibilities of magnetic separations in biosciences and biotechnologies is given. Magnetic separations can be used e.g. in microbiology (detection of pathogenic microorganisms), cell biology (removal of cancer cells, separation of lymphocytes), molecular biology (isolation of m-RNA), biotechnology (isolation and immobilization of enzymes and other biologically active compounds) and ecology (removal of environmental contaminants). Further progress of these techniques is expected.
Abstract: A procedure for the construction of a cheap and simple flat magnetic separator is described. The separator can be used to remove magnetic carriers and sorbents from up to 500 - 1000 ml of suspension. The properties of this model and commercially available separators are similar.
Abstract: Magnetic chitosan gel particles, bearing covalently immobilized copper phthalocyanine dye (''magnetic blue chitosan''), were prepared and used for the isolation and/or removal of polycyclic dyes from water solutions and suspensions. Binding of these polycyclic dyes occures by a chemical equilibrated and saturatable mechanism, following the Langmuir adsorption model. The values of maximum uptake (maximum adsorption capacity) were calculated. The bound dyes can be eluted from the sorbent with methanol, methanol-conc. ammonia solution (50/1, v/v) and 10% acetic acid.
Abstract: The paper describes the application of magnetic particles for the isolation of target microbial cells directly from crude samples. The separated cells can be used for rapid identification and confirmation.
Abstract: Biospecific magnetic sorbent for lysozyme isolation (magnetic chitin) has been prepared from magnetic chitosan after acetylation with acetic anhydride. The capacity of magnetic chitin was 2.5 mg of lysozyme per 1 ml of sorbent.
Abstract: Magnetic biospecific affinity adsorbents for lysozyme isolation have been prepared. They were obtained by incorporation of fine magnetite particles into the structure of chitin, agar or agarose. Hen egg white lysozyme was obtained in 90 % purity in one step.
