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Biomedical subjects

J Havel

Publications and source records attributed to J Havel.

At least 19 recordsLinked to original sources
PubMed2005

Analysis of polyphenols in wines: correlation between total polyphenolic content and antioxidant potential from photometric measurements. Prediction of cultivars and vintage from capillary zone electrophoresis fingerprints using artificial neural network.

The polyphenols (some of them are also called phytoalexins, flavonols, flavanons, flavanonols, flavons, flavanols, and anthocyanines) are usually marked as potent antioxidants or radical scavengers which assist the body cells against oxidation. Polyphenols in wine are also considered to explain so called French paradox (long life aging and low number of coronary diseases despite of high alcohol and fat consumption). The total polyphenolic content (TPC) and total antioxidant potential (TAP) were determined by photometry and found strongly correlated. This finding suggests that the determination of TAP can be replaced by a more simple procedure of TPC determination. Capillary zone electrophoresis (CZE) with preconcentration by solid phase extraction (SPE) was applied for some polyphenols determination and for obtaining electropherograms of the SPE extracts (fingerprints). From mathematical evaluation of the fingerprints, prediction of cultivars and vintage using artificial neural networks (ANN) was done with more than 90% correct prediction. The study was performed on a set of 47 samples of young wines (vintage 1999-2002) from south Moravia (Czech Republic) and New South Wales (Australia).

Antioxidants↗
PubMed2004

Advantages of derivatization by osmium tetroxide and 2,2'-bipyridine for matrix-assisted laser desorption/ionization post-source decay fragment ion analysis of peptides.

Matrix-assisted laser desorption/ionization--post-source decay (MALDI-PSD) fragment ion analysis is frequently used for peptide sequence determination. PSD fragmentation is often changed or improved in terms of, e.g., sequence coverage, after derivatization. In this work, the influence of modification by an osmium tetroxide-bipyridine reagent (Os,bipy) on the MALDI-PSD behaviour of peptides is studied. The reagent modifies peptides specifically at tryptophan residues and oxidizes methionine to methionine sulfone and cysteine to cysteic acid. As a result the masses of some of the fragments are specifically shifted in case of peptides containing a methionine by +32 Da and, in cases of peptides containing a cysteine residue, by +48 Da. In addition, due to the change in protonation properties of a peptide after oxidation, fragments containing cysteic acid are in most cases totally suppressed. This effect significantly facilitates peptide sequence determination. Improvement of MALDI-TOFMS and PSD analysis after the reaction with Os,bipy is demonstrated for examples involving derivatives of humanin, a novel neuroprotective peptide.

2,2'-Dipyridyl↗
PubMed2004

Content of aliphatic hydrocarbons in limpets as a new way for classification of species using artificial neural networks.

It is demonstrated that biological species like limpets can be classified according to their level of n-alkanes when artificial neural networks are applied. Marine intertidal and subtidal limpets of the Canary Islands (Spain), Patella piperata, Patella candei crenata and Patella ulyssiponensis aspera were selected as bioindicator organisms. Samples were collected at four stations on the coasts of Fuerteventura. Concentration of n-alkanes in the soft tissues of the limpets has been determined by gas chromatography. Data were treated with artificial neural networks (ANNs) and it was found that using suitable architecture of a supervised artificial neural network, the limpets can be successfully distinguished (classified) up to 98%.

Alkanes↗
PubMed2004

Validation of a capillary zone electrophoresis method for determination of rimantadine hydrochloride in Rimantadin100 tablets and the method application to dissolution test monitoring.

A capillary zone electrophoretic method with indirect UV-detection for determination of rimantadine, an antiviral drug against influenza A, in tablets was validated. Instrumental precision, the method precision, accuracy, calibration curve linearity, selectivity, robustness, and time stability of the sample and the standard were tested. The method was also applied to monitor dissolution tests of the tablets. The possibility of addition of an internal standard for improvement of the method precision was discussed.

Electrophoresis, Capillary↗
PubMed2003

Supramolecular interactions of humic acids with organic and inorganic xenobiotics studied by capillary electrophoresis.

Methodology based on capillary electrophoresis (CE) to study humic acids (HAs)-xenobiotics interactions is proposed. The interactions of HAs with organic and inorganic xenobiotics like paraquat, diquat, p,p(')-DDE, p,p(')-DDT, potassium ferrocyanide, potassium ferricyanide, chloride, 4-nitrocatechol and other organic compounds were studied. They were found to be of different kind depending on the structure of the xenobiotic molecule and on its charge (neutral, positive or negative). Ion binding, hydrogen bonding, van der Waals forces, ligand exchange, hydrophobic and hydrophilic adsorption, charge-transfer complexes and sequestration are some of the different mechanisms proposed to bind inorganic and organic compounds to HAs. It was also observed that some of the pollutants are strongly complexed (bound) only with some of the HA fractions forming quite stable entities of supramolecular kind, which can migrate independently. In addition, the stability constant of HA-Cl (negatively charged species) was estimated to be logk=3.1+/-0.95. In order to explain the interaction between negatively charged HAs and inorganic anions (like Cl(-), [Fe(CN)(6)](3-) and [Fe(CN)(6)](4-)), it is proposed that macropolycyclic polyamine structures are present in HA supramolecules, and that they are responsible for such strong binding.

Electrophoresis, Capillary↗
PubMed2003

[Energy-dispersive x-ray fluorescence spectrometry--a forensic chemistry method for determination of shooting distance].

The article follows up the experiences Energo-dispersive X-ray fluorescence spectrometry (EDXRF) as the forensic necrochemical method as the tool for detection of metals (gunshot residues--GSR) in connection with gunshot-wounds of persons--authors: dipl. Ing. J. Havel and dipl. Ing. K. Zelenka and Energo-dispersive X-ray fluorescence spectrometry (EDXRF) as the forensic method as the tool for identification of inlets (gunshot--entries) and outlets (gunshot--exits)--author: dipl. Ing. J. Havel.

Forensic Ballistics↗
PubMed2002

Capillary zone electrophoresis and artificial neural networks for estimation of the post-mortem interval (PMI) using electrolytes measurements in human vitreous humour.

Determination of electrolyte concentrations (mainly potassium) in vitreous humour has long been considered an important tool in human death investigations for the estimation of the post-mortem interval (PMI). On the basis of its well known potential in ion analysis, capillary zone electrophoresis (CZE) has recently been applied to achieve a rapid and simultaneous determination of inorganic ions in this extracellular fluid. In the present work, artificial neural networks (ANN) were applied for modelling of the relationship of multicomponent CZE analysis of K+, NH4+, Na+, and Ba2+ ions in vitreous humour with PMI. In a study based on 61 cases with different causes of death and a known PMI ranging from 3 to 144 h, the use of ANNs considering all inorganic ion data from the human vitreous humour, achieved a substantial improvement of post-mortem interval prediction. Good linear correlation was observed (r2 = 0.98) and in comparison to the traditional linear least squares (LLS) method applied only to K+ levels in the vitreous humour, the prediction of PMI with ANN was improved by a factor of 5 from approximately +/- 15 h to less than 3 h.

Autopsy↗
PubMed2001

Determination of esmolol in serum by capillary zone electrophoresis and its monitoring in course of heart surgery.

A new Capillary Zone Electrophoresis (CZE) procedure for determination of esmolol, an ultra-short-acting beta-blocker, in serum was developed. Dichloromethane was applied as a deproteination agent and it was used also for the inactivation of erythrocytal esterase and in the same time for the extraction of esmolol from blood. The re-extraction of esmolol from organic phase to water phase was performed by 0.01 M HCl. An aliquot of 200 ml of acid aqueous phase was used for the injection and analysis. CZE determination was done in 50 mM phosphate buffer (pH=8.0) with detection at 222 nm. The concentration detection limit of esmolol in serum was 0.051 microg/ml. This method was applied in an extensive heart surgery experiment on pigs (Sus scrofa).

Adrenergic beta-Antagonists↗
PubMed2001

High-performance liquid chromatographic determination of deoxycytidine monophosphate and methyldeoxycytidine monophosphate for DNA demethylation monitoring: experimental design and artificial neural networks optimisation.

The optimal conditions for the separation of 2'-deoxycytidine-5'-monophosphate and 5-methyl-2'-deoxycytidine-5'-moncphosphate in the matrix of other natural occurring nucleotides after digest of DNA were investigated. Using experimental design combined with artificial neural networks, efficient optimisation of the HPLC separation conditions was performed. The mobile phase composition was optimised on the basis of its three components (concentration of phosphate, content of methanol and pH). The best separation was obtained with a mobile phase containing 50 mM phosphate, pH 5.5 and 6% methanol. The final resolution achieved between 2'-deoxycytidine-5'-monophosphate and 5-methyl-2'-deoxycytidine-5'-monophosphate was equal to 2.78. Finally, the optimised system was successfully tested on the nucleotide mixture solution to determine the methylation state of 2'-deoxycytidine-5'-monophosphate in DNA in the search for FMR1 gene changes.

Chromatography, High Pressure Liquid↗
PubMed2001

Prediction of retention times for anions in linear gradient elution ion chromatography with hydroxide eluents using artificial neural networks.

The feasibility of using an artificial neural network (ANN) to predict the retention times of anions when eluted from a Dionex AS11 column with linear hydroxide gradients of varying slope was investigated. The purpose of this study was to determine whether an ANN could be used as the basis of a computer-assisted optimisation method for the selection of optimal gradient conditions for anion separations. Using an ANN with a (1, 10, 19) architecture and a training set comprising retention data obtained with three gradient slopes (1.67, 2.50 and 4.00 mM/min) between starting and finishing conditions of 0.5 and 40.0 mM hydroxide, respectively, retention times for 19 analyte anions were predicted for four different gradient slopes. Predicted and experimental retention times for 133 data points agreed to within 0.08 min and percentage normalised differences between the predicted and experimental data averaged 0.29% with a standard deviation of 0.29%. ANNs appear to be a rapid and accurate method for predicting retention times in ion chromatography using linear hydroxide gradients.

Anions↗
PubMed2000

Highly reproducible capillary zone electrophoresis of humic acids in cyclodextrin- or oligosaccharide-modified background electrolytes.

Capillary zone electrophoresis has been used for the characterization and separation of humic acids. It was found that addition of saccharides like alpha-, beta-, gamma-cyclodextrins, maltose, hydroxyethylcellulose or dextran sulfate in the background electrolyte (50 mM Na2 B4 O7, pH 9.6) yields better separation patterns and highly reproducible electropherograms. Electropherograms with higher numbers of peaks and high reproducibility were obtained with alpha- and beta-cyclodextrins or with a mixture of alpha- + gamma-cyclodextrin-modified background electrolytes. Separation was carried out with the cathode at the detector end of the column. Adsorption of humic acids to the capillary wall was diminished using an epoxy-coated capillary tube.

Cyclodextrins↗
PubMed2000

Separation of polyphenols in Canary Islands wine by capillary zone electrophoresis without preconcentration.

A method for separation and determination of polyphenols in wine by capillary zone electrophoresis (CZE) without any preconcentration step is described. The sensitivity and limits of detection for gentisic and p-coumaric acid are better than those previously published. The effect of a possible C18 solid-phase extraction prior to the CZE analysis was examined. The developed optimized method (without any extraction step) was applied to the analysis of wines from Tenerife, Canary Islands.

Electrophoresis, Capillary↗
PubMed2000

Reactive dye ostazine black V-B: determination in the dye-bath and hydrolysis monitoring by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry.

Monitoring the hydrolysis of Ostazine Black V-B reactive dye was found to be possible by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS). All the desired substances were identified in a mixture of the dye-bath. The process of the substrate reactive dye hydrolysis was qualified with hydrolysis rate constants k(1) (2.0 +/- 0.3 h(-1)) and k(2) (0.6 +/- 0.1 h(-1)). The method developed is important for the dyeing industry and for following the colouration process.

Coloring Agents↗
PubMed2000

Data evaluation for soft drink quality control using principal component analysis and back-propagation neural networks.

This work describes an alternative for chemical data research, with the aim of evaluating finished product quality. Analytical data for additives in soft drinks are interpreted by the use of multivariate data analysis: principal component analysis (PCA), factor analysis, cluster analysis, and artificial neural networks. Taking into account various chemical components like sorbic, benzoic, and ascorbic acids; saccharose; caffeine; Na, K, Ca, Mg, Fe, Zn, Cu, P, and B, soft drinks were characterized and classified. The ratios of Na, K, Ca + Mg, P, and K/Na have been studied. The application of PCA, cluster analysis, and artificial neural networks showed that combination of these chemometric tools offers effective means for modeling and classifying soft drinks in accordance with their contents in additives and heavy metals.

Beverages↗
PubMed1999

Artificial neural networks for computer-aided modelling and optimisation in micellar electrokinetic chromatography.

The separation process in capillary micellar electrochromatography (MEKC) can be modelled using artificial neural networks (ANNs) and optimisation of MEKC methods can be facilitated by combining ANNs with experimental design. ANNs have shown attractive possibilities for non-linear modelling of response surfaces in MEKC and it was demonstrated that by combining ANN modelling with experimental design, the number of experiments necessary to search and find optimal separation conditions can be reduced significantly. A new general approach for computer-aided optimisation in MEKC has been proposed which, because of its general validity, can also be applied in other separation techniques.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed1999

Determination of platinum (II,IV) and palladium(II) as thiocyanate complexes by capillary zone electrophoresis analysis of carboplatin and similar drugs.

The thiocyanate complexes of Pd(II), Pt(II) and Pt(IV) were studied by capillary zone electrophoresis. Pd(II) can be detected in the form of the thiocyanate complex at 305 nm with higher sensitivity than in the form of its chloro complex (absorption maximum 214 nm). A detection limit equal to 5 ppb for Pd has been finally achieved. The possibility of simultaneous determination of Pd(II) and Pt(IV) in the form of thiocyanate complexes has also been demonstrated. When the method optimized for the determination of Pt(II) was applied to the drugs Cykloplatin and Ribocarbo (containing carboplatin) and Platidiam (containing cisplatin), good agreement of the platinum content with the declared value was obtained. Samples of vehicle exhaust particulates (National Institute for Environmental Studies, Japan, No. 8 reference material) were also analyzed.

Antineoplastic Agents↗