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Results for “Metallocenes”

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At least 289 records · Page 16Linked to original sources
PubMed1989

Sensitive ferrocene reagents for derivatization of amines for high-performance liquid chromatography with electrochemical detection.

Six reagents possessing ferrocene as an electrophore were prepared and evaluated for pre-column derivatization of amino compounds for their determination by high-performance liquid chromatography with electrochemical detection. The utility of these reagents was investigated employing phenethylamine as a model compound. Among these six, N-succinimidyl 3-ferrocenylpropionate was the best with respect to reactivity, stability and electrochemical properties. The developed method was applied to the determination of putrescine formed from ornithine by ornithine decarboxylase.

Amines↗
PubMed2002

Determination and pharmacokinetic study of ferrocene-A in blood serum of rabbits.

Ferrocene-A (ferrocenyl-1-phenyl-1-dioxy-1,4-butin-2) has significant antitumour and antibacterial properties. This study was designed to estimate main pharmacokinetic parameters of ferrocene-A (FC-A). These parameters are very important from the standpoint to elucidate the mechanism of pharmacological action of ferrocene-A. Examined substance was administrated intramuscularly and orally to rabbits. For determination of small quantities of ferrocene-A in a blood plasma liquid-liquid extraction and reversed-phase high performance liquid chromatography (HPLC) method was applied. Kinetic parameters were estimated using the one-compartment linear pharmacokinetic model.

Administration, Oral↗
PubMed2000

Ferrocene-avidin conjugates for bioelectrochemical applications.

Coupling of ferrocene moieties to avidin via a flexible spacer molecule yields a conjugate which combines the unique biotin-binding properties of avidin with the reversible redox characteristics of ferrocenes. Synthesis of the conjugate has been optimised and the conjugates were characterised bio- and electrochemically. Covalent immobilisation of the conjugate on gold electrodes in a dense monolayer results in electrodes with a high binding capacity for biotinylated molecules as well as good electron transfer properties. The application potential of such electrodes for bioelectrochemical systems is demonstrated by electrochemical reduction of hydrogen peroxide under mild conditions catalysed by a bound biotin-microperoxidase MP11 conjugate.

Avidin↗
PubMed2001

Construction of electrochemical flow immunoassay system using capillary columns and ferrocene conjugated immunoglobulin G for detection of human chorionic gonadotrophin.

In this paper is reported a miniaturized flow immunoassay system. Ferrocenecarboxylic acid (Fc) conjugated with anti-HCG immunoglobulin G (IgG) antibody (Fc-IgG) was prepared, and used as a novel analytical reagent. The system consists of the immunoreaction section, the capillary column packed with cation exchange resin, and the flow cell for electrochemical detection of Fc-IgG. Antibody-antigen complexes were separated from their free conjugate on the basis of differences in isoelectric point (pI) using a cation exchange capillary column. The assay yielded a linear relationship between signal and HCG concentration in the range 0-2000 mIU/ml. This simple technique enables the assay of HCG within 2 min. The cation exchange capillary column was regenerated by occasional elution with malonate buffer (pH 6.0) containing 0.5 M NaCl, to remove free conjugate. Free conjugate recovered in this manner could be reused up to eight times without significant decreases in the sensitivity of the immunoassay. This electrochemical flow immunoassay requires only minute quantities of serum and generates highly reproducible results.

Antigen-Antibody Complex↗
PubMed2003

Amperometric glucose sensors based on ferrocene containing polymeric electron transfer systems-a preliminary report.

In this paper we introduce a preliminary work in which a redox mediator containing polyvinylferrocene immobilized on silica gel particles is synthesized. Carbon paste electrodes prepared with this polymeric mediator were studied for their stability in aqueous media for a month. The results indicated that approximately 70% of the initial activity was retained after a month. A steady state amperometric measurement of this carbon paste electrode containing this mediator and glucose oxidase at different potentials showed a linear relationship at elevated glucose concentration.

Adsorption↗
PubMed2003

Graphite-Teflon composite bienzyme amperometric biosensors for monitoring of alcohols.

Composite graphite-Teflon electrodes, in which the enzymes alcohol oxidase (AOD) and horseradish peroxidase (HRP), as well as the mediator ferrocene, are incorporated into the electrode matrix, are reported for the reliable monitoring of alcohols in food and beverages. The bienzyme electrodes are constructed by simple physical inclusion of the enzymes and the mediator in the bulk of graphite-70% Teflon rigid cylindrical pellets. The composite biosensors are robust and reusable because of the renewability of the electrode surface by polishing. Reproducible amperometric responses at 0.00 V were obtained with different electrodes constructed from the same pellet and from different pellets. No significant loss of the enzymes activities was found after at least 3 months of storage at 0 degrees C. The detection limits obtained by amperometry in stirred solutions can be advantageously compared with those achieved with commercial sensors for alcohols. The bienzyme electrodes are suitable to be used under flow-injection conditions, as well as for amperometric detection in HPLC. The bioelectrodes were employed for the determination of ethanol in beers, wines and liquors, using both batch- and flow-injection modes, and for the determination of methanol in wines and liquors by HPLC with amperometric detection. Only a dilution of the beverages was needed as sample treatment in all cases.

Alcoholic Beverages↗
PubMed2003

Studies on the electrochemical performance of glucose biosensor based on ferrocene encapsulated ORMOSIL and glucose oxidase modified graphite paste electrode.

The electrochemical performance of a new glucose biosensor is reported. The glucose biosensor is developed using glucose oxidase (GOD) and ferrocene encapsulated palladium (Pd)-linked organically modified sol-gel glass (ORMOSIL) material incorporated within graphite paste electrode. The ORMOSIL material incorporated within graphite paste electrode behaves as an excellent electrocatalyst for the oxidation of enzymatically reduced GOD. The electrochemical behavior of new glucose biosensor has been examined by cyclic volammetry and amperometric measurements. The bioelectrocatalysis of ORMOSIL embedded within graphite paste as a function of storage time and varying concentration of ORMOSIL is reported. The initial amperometric response on glucose sensing is recorded to be 145 microA at 15% (w/w) concentration of the ORMOSIL which is decreased to 20 microA at 5% of the same keeping GOD concentration constant. The variation of electrochemical behavior of the ORMOSIL embedded within graphite paste as a function of time has also been studied based on cyclic voltammetry. The voltammograms showing the reversible electrochemistry of ORMOSIL encapsulated ferrocene is changed into a plateau shape as a function of time, however, the electrocatalytic behavior is still retained. The practical usability of new glucose sensor has been compared with earlier developed glucose sensor. The sensitivity, response time and linearity of the new glucose biosensor are found to be excellent over earlier reported glucose biosensor. The amperometric response, calibration curve and practical applications of new glucose sensor are reported.

Biosensing Techniques↗
PubMed2003

Redox labelled avidin for enzyme sensor architectures.

Conjugates of avidin with ferrocene and with microperoxidase 8 have been used as electrochemically active molecular building blocks. Assemblies of the conjugates with biotinylated glucose oxidase or lactate oxidase on gold electrodes were tested as enzyme sensors for glucose and lactate. The electrochemical detection is based either on ferrocene-mediated oxidation of the substrate in oxygen-free solution, or on microperoxidase-catalysed reduction of H2O2 which is enzymatically produced from the substrate and molecular oxygen. Glucose and lactate were detectable with both detection principles in concentrations down to 1 or 0.1 mM, respectively. The molecular architecture concept allows quick adaptation of the sensors to other analytes, and it provides a platform for arrays of sensors with different selectivity.

Avidin↗
PubMed1997

Mediated electrochemistry of peroxidases--effects of variations in protein and mediator structures.

The kinetics of a range of ferrocene derivatives with horseradish peroxidase (HRP), cytochrome c peroxidase (CCP) and 3 charge reversal mutants of cytochrome c peroxidase were measured using cyclic voltammetry. Substantial differences in rate constant (100 fold) were observed between HRP and CCP for the same mediator with smaller differences (4-5 fold) for different mediators with the same enzyme. The rate constant did not seem to be dependent on redox potential differences. Cluster analysis is proposed as a way of classifying mediator reactivity.

Cytochrome-c Peroxidase↗
PubMed2000

Synthesis and antifungal activity of a ferrocene-fluconazole analogue.

A novel ferrocene fluconazole analogue was synthesized and its antifungal properties investigated against yeast strains of medical importance, including those intrinsically resistant to fluconazole. In vitro tests revealed a slight increase in fungal growth and a reversal of the effect of fluconazole at minimal inhibitory concentrations.

Antifungal Agents↗
PubMed2002

Polymer-supported ferrocenyl oxazolines for the catalyzed highly enantioselective phenyl transfer to aldehydes.

A new chiral MeO-PEG-supported ferrocenyl oxazoline was synthesized and successfully employed in the enantioselective phenyl transfer to aldehydes. The products were obtained in high yields and with excellent enantioselectivities (up to 97% ee). Furthermore, the recovery of the ferrocene was facile, and catalyst efficiency was maintained in subsequent reactions.

Benzaldehydes↗
PubMed2002

Antimalarial activity of ferrocenyl chalcones.

A series of ferrocenyl chalcones were synthesized and evaluated for in vitro antimalarial activity against a chloroquine-resistant strain of Plasmodium falciparum. The most active compounds were 1-(3-pyridyl)-3-ferrocenyl-2-propen-1-one (6) and 1-ferrocenyl-3-(4-nitrophenyl)-2-propen-1-one (28) with IC(50) of 4.5 and 5.1 microM, respectively. Differences in activity were not readily explained by the size and lipophilicity characteristics of these compounds.

Animals↗
PubMed2003

Transient oscillations under strongly mismatched Hartmann-Hahn conditions.

Based on the standard 2D Polarization inversion experiment, a new pulse sequence (PI-TAPF) is proposed. It represents a combination of Polarization Inversion and TAPF (time averaged precession frequency) sequences. The depolarization period consists of phase-alternating intervals of different duration in the I channel. The pulse sequence yields transient oscillations under the strongly mismatched HH conditions where the required power for the dilute spins is reduced by a factor of 5. Experimental results recorded for a sample of ferrocene powder are well reproduced by numerical simulations.

Algorithms↗
PubMed2002

Stabilization of ferrocene leakage by physical retention in a cellulose acetate membrane. The fructose biosensor.

The prevention of ferrocene leakage from an electrode by physical retention of mediator in a matrix of cellulose acetate membrane is reported. Five types of the cellulose acetate membranes were prepared, containing 1.8%, 5.3%, 8.5%, 20.0% of ferrocene and a membrane containing 1.8% of ferrocene and 0.05 % of Nafion in the matrix. Ferrocene embedded membranes were successfully applied in the construction of a fructose biosensor by immobilization of PQQ-dependent fructose dehydrogenase (FDH). The biosensor comprising a cellulose acetate membrane with 1.8% of ferrocene and 0.05% of Nafion had good stability characteristics, retained almost 40% of the initial response after 8 h of continuous use with an initial sensitivity of 226 nA mM(-1) and response time of 75 s.

Biosensing Techniques↗
PubMed1994

Films formed by oxidation of ferrocene at platinum electrodes.

Oxidation of ferrocene in acetonitrile resulted in films on Pt electrodes under voltammetric conditions. Films were more readily formed with tetrabutylammonium tetrafluoroborate as the electrolyte than with perchlorate salts. No films were detected when ferrocene was oxidized in aqueous 0.05 M cetyltrimethylammonium bromide (CTAB). Analysis of the films by FT-IR and Auger spectroscopy confirmed iron-containing oxidation products on Pt, presumably from chemical reactions of ferricinium ions. Oxidation of 50-100 mM ferrocene in acetonitrile on Pt yielded insoluble precipitates. Analyses by MS, FT-IR, and UV-visible (water extract), suggested a mixture of oligomeric material and a small fraction of ferricinium ions. Film formation had much less influence on voltammograms on 12.5-micron-radius Pt microdisks than on 0.5-mm-radius Pt. This is consistent with the smaller sensitivity of microelectrodes to chemical reactions following charge transfer. The smaller apparent heterogeneous rate constants (k zero') found for ferrocene on macroelectrodes than on microelectrodes could possibly be influenced by film formation on larger Pt electrodes. Correlations between macro- and microelectrode kinetic data suggest that macroelectrode k zero' values may be valid in a relative sense when ohmic drop is negligible. Bias in k zero's on conventional-sized electrodes should be small in solutions giving minimal film formation, such as micellar CTAB.

Electrochemistry↗
PubMed1994

Biodegradation of soluble redox polymers. 1. (0.017ferrocene)amylose.

The reaction of amylose with NaH and FcCH2NMe3+I- in dimethyl sulfoxide brought about a redox-labeled polymer with a low degree of modification, viz. 1 ferrocene residue per 60 glucose units. The preparation, (0.017ferrocene)amylose, displays one-electron irreversible behavior at a pyrographite electrode in terms of the Delahay formalism, the formal redox potential E degree' being equal to 0.38 V at pH 6 and 40 degrees C versus SCE. Specific to amylose enzymes endo-depolymerases, which carry out random hydrolysis, accept the labeled amylose providing a significant increase in the peak current on cyclic voltammograms. The absence of potential drifts suggests that the effect is due an increase in the diffusion coefficients of the amylose fragments in the course of enzymatic digestion of (0.017ferrocene)amylose. This proposal was confirmed by the simulation of experimental cyclic voltammograms. Several practical applications of the results of this study for electrochemical assaying the amylolytic activity and evaluation of the mechanisms of the enzymatic catalysis by amylases have been demonstrated.

Amylose↗