Biomedical subjects

E Forgács

Publications and source records attributed to E Forgács.

At least 19 recordsLinked to original sources

PubMed2004

Effect of pH and salts on the binding of free amino acids to the corn protein zein studied by thin-layer chromatography.

The interaction of free amino acids with the corn protein zein was studied by thin-layer chromatography carried out on cellulose layers covered with zein and the effect of pH and salts on the strength of interaction was elucidated. Only the binding of Arg, His, Lys, Orn and Trp to zein was verified, other amino acids were not retained. Retention of Arg, His, Lys and Orn decreased linearly with increasing concentration of salts the mobile phase indicating the hydrophilic character of amino acid-zein interaction. Both alkaline and acidic pH influenced the strength of binding. Principal component analysis indicated the different character of the influence of pH and salts on the interaction. The results suggest that these amino acid residues may account for the binding of other peptides and proteins to zein.

Amino Acids↗

PubMed2004

Capillary electrophoretic separation of proteins and peptides by ion-pairing with heptanesulfonic acid.

Heptanesulfonic acid as ion-pairing agent was used for the separation of mixtures of low and high molecular mass peptides/proteins by capillary electrophoresis. The separation conditions used were: capillary 37 cm (30 cm to the detector) x 75 microm i.d., voltage 10 kV, phosphate buffer 50 mmol/l, ion-pairing agent heptanesulfonic acid at three different concentrations, namely, 0, 20 or 100 mmol/l, pH 2.5. The separation reflected the ion-pairing equilibria between the ion-pairing agent and the peptide/protein analytes. The influence of ion-pairing on sample mobility (running time) was more pronounced in case of the higher-molecular peptides as compared to the low molecular ones. This difference offers the possibility to separate low and high molecular peptides/proteins that under the absence of the ion-pairing agent would co-migrate. The principle of this approach was demonstrated on a randomly selected set of peptides/proteins; the practical applicability was demonstrated on a set of CNBr peptides arising from a naturally occurring mixture of collagen types I and III.

Animals↗

PubMed2003

Quantification of the ratio of positional isomer dilinoleoyl-oleoyl glycerols in vegetable oils.

The distribution of fatty acids in a triacylglycerol is of great importance from nutritional, biochemical, quality and technological points of view. The ratio of triacylglycerol positional isomers containing two linoleic acid (18:2) and one oleic acid (18:1) moieties--namely, 1(3),2-dilinoleoyl-3(1)-oleoyl glycerol (LLO) and 1,3-dilinoleoyl-2-oleoyl glycerol (LOL)--were quantified in grape seed, olive, pumpkin seed, soybean, sunflower and wheat germ oils by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (HPLC/APCI-MS) in selected ion monitoring (SIM) mode. Relative LOL contents (LOL/(LLO+LOL)) of the oils were calculated from the mass abundances of the [LL]+ and [LO]+ diacylglycerol fragment ions ([M+H-RCOOH]+) using a calibration curve. The calibration curve of the relative diacylglycerol mass abundances was measured in SIM mode. The relative LOL contents were found to be relatively consistent for each oil variety. The relative LOL content in grape seed, sunflower, pumpkin seed, soybean and wheat germ oils accounted for 44.2 +/- 2.6, 26.8 +/- 3.2, 16.7 +/- 4.6, 15.9 +/- 2.9 and 13.9 +/- 4.3%, respectively. Only olive oils contained practically 100% of the LLO isomer. These results indicate that the unsaturated fatty acids such as linoleic and oleic acids have 'non-random' distribution patterns in various oils.

Cucurbita↗

PubMed2003

Effect of monovalent cations on the binding of amino acids to cholesterol.

The nature of the interaction between amino acids and cholesterol was shown by reversed-phase thin-layer chromatography (RP-TLC) in the presence of monovalent cations of different concentration. The degree of interaction between amino acids and cholesterol was affected by different salt solutions and by applying cholesterol to the chromatographic plates at higher concentration. The relative strength of interaction was determined by statistical evaluation of the results in each case. The objectives of the investigations were to study the retention behaviour of biologically active amino acids on alumina supports impregnated with cholesterol and to characterize the effects of monovalent cations on the interaction between amino acids and cholesterol.

Algorithms↗

PubMed2002

Effect of ascorbic acid on the stability of beta-carotene and capsanthin in paprika (Capsicum annuum) powder.

The effect of ascorbic acid, light, and storage on the stability of the pigments beta-carotene and capsanthin in red pepper (Capsicum annuum) powder has been elucidated by determining the amount of pigment in samples treated by various concentrations of ascorbic acid. Determination of pigment concentration has been performed after different storage times using high-performance liquid chromatography. The dependence of the concentration of pigments on the concentration of ascorbic acid, presence of light and the storage time has been assessed by stepwise regression analysis. The concentration of pigments decreased at longer storage time and increased at higher concentration of ascorbic acid, beta-carotene being more sensitive towards storage time and concentration of ascorbic acid than capsanthin. Interaction between the effects of light and storage time, and light and concentration of ascorbic acid has been established.

Antioxidants↗

PubMed2002

Differentiation of vegetable oils by mass spectrometry combined with statistical analysis.

The main triacylglycerol (TAG) composition of different plant oils (almond, avocado, corn germ, grape seed, linseed, mustard seed, olive, peanut, pumpkin seed, sesame seed, soybean, sunflower, walnut and wheat germ) were analyzed using two different mass spectrometric techniques: HPLC/APCI-MS (high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry) and MALDI-TOFMS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry).Linear discriminant analysis (LDA) as a multivariate mathematical statistical method was successfully used to distinguish different plant oils based on their relative TAG composition. With LDA analysis of either APCI-MS or MALDI-MS data, the classification among the almond, avocado, grape seed, linseed, mustard seed, olive, sesame seed and soybean oil samples was 100% correct. In both cases only 6 different oil samples from a total of 73 were not classified correctly.

Chromatography, High Pressure Liquid↗

PubMed2001

Effects of fluorescent light and vacuum packaging on the rate of decomposition of pigments in paprika (Capsicum annuum) powder determined by reversed-phase high-performance liquid chromatography.

The effect of storage time, the presence of light and oxygen on the decomposition rate of carotenoid pigments in paprika (Capsicum annuum) powders was determined by reversed-phase high-performance liquid chromatography (RP-HPLC). The similarities and dissimilarities of pigment composition of samples under various storage conditions was elucidated by principal component analysis (PCA) and stepwise regression analysis (SRA). Calculations proved that the overall decomposition rate of pigment sections equally depended on the storage time and on the presence of light and oxygen, the effect of storage time being the most decisive factor while the impact of oxygen was the lowest. The selectivity of decomposition also depended on the storage time and on the presence of oxygen the influence of storage time being the most important. RP-HPLC followed by PCA and SRA can be successfully used for the study of the impact of environmental conditions on the decomposition of carotenoid pigments of paprika powders.

Capsicum↗

PubMed2001

Liquid chromatographic separation of terpenoid pigments in foods and food products.

The newest achievements in the use of various liquid chromatographic techniques such as adsorption and reversed-phase thin-layer chromatography and HPLC employed for the separation and quantitative determination of terpenoid-based color substances in foods and food products are reviewed. The techniques applied for the analysis of individual pigments and pigments classes are surveyed and critically evaluated. Future trends in the separation and identification of pigments in foods and food products are delineated.

Chromatography, High Pressure Liquid↗

PubMed2001

Evaluation of peptide electropherograms by multivariate mathematical-statistical methods. I. Principal component analysis.

Depository effects in slowly metabolised proteins, typically glycation or the estimation of products arising from the reaction of unsaturated long-chain-fatty acid metabolites (possessing aldehydic groups) are very difficult to assess owing to their extremely low concentration in the protein matrix. In order to reveal such alterations we applied deep enzymatic fragmentation resulting in a set of small peptides, which, if modified, are likely to change their electrophoretic properties and can be visualised on the resulting profile. Peptide maps of collagen (a mixture of collagen types I and III digested by bacterial collagenase) were applied as the model protein structure for detecting the nonenzymatic posttranslational changes originating during various physiological conditions like high fructose diet and hypertriglyceridemic state. Capillary electrophoresis in acidic media (sodium phosphate buffer, pH 2.5) was used as the separation method capable of (partial) separation of over 60 peptide peaks. Two to 13 changes were revealed in the profiles obtained reflecting the physiological conditions of the animals tested. Combination of peptide profiling with subsequent t-test evaluation of individual peak areas and principal component analysis based on cumulative peak areas of individual sections of the electropherograms allowed to determine in which section (part) of the electropherogram the physiological state indicating changes occurred. Simultaneously it was possible to reveal the qualitative differences between the four physiological regimes investigated (i.e., which regime affects the collagen molecules most and which affects them least). The approach can be used as guidance for targeted preseparation of the very complex peptide mixture.

Animals↗

PubMed2001

Mixtures of nonionic and anionic surfactants: interactions with low-molecular-mass homopeptides.

The interaction between low molecular-mass homopeptides and mixtures of nonionic and anionic surfactants has been assessed by using reversed-phase thin-layer chromatography. The relative strength of interaction for mixtures of sodium dodecylsulfate and tridecylalcohol diglycolate (GNX) at the molar ratios of 8:2, 6:4, 4:6 and 2:8 has been calculated and its relationship with the physicochemical parameters (number of amino acid units, hydrophobicity, side chain bulkiness, electronic characteristics) of peptides has been computed by stepwise regression analysis. Each peptide interacted with each surfactant mixture the strength of interaction markedly depending on both the character of the peptide and the composition of the surfactant mixture. The hydrophobicity and electronic properties of the amino acid units exerted the highest influence on the strength of interaction at the highest concentration of the nonionic surfactant (GNX) whereas the number of amino acid units in the peptide molecule and the bulkiness of the amino acid side chain governed the strength of interaction at the lowest concentration of GNX.

Anions↗

PubMed2001

Profiling of colour pigments of chili powders of different origin by high-performance liquid chromatography.

The colour pigments of five chili powders of different origins were separated and quantified by reversed-phase high-performance liquid chromatography (RP-HPLC). The similarities and dissimilarities of pigment composition of chili powders were elucidated by principal component analysis (PCA). RP-HPLC separated 50-100 pigment fractions depending on the detection wavelength and on the origin of chili powder. It was found that the pigment composition of chili powders from Malaysia and China and from India and Pakistan show marked similarities while the composition of colour pigments of chili powder from Thailand was different. It was further established that the chromatograms are similar in the first 5-35 min of development, they are highly different between 35 and 75 min and moderately different at the end of the chromatograms. It was concluded that RP-HPLC followed by PCA can be successfully used for the identification of chili powders according to the composition of their colour pigments.

Capsicum↗

PubMed2001

Binding of substituted phenol and aniline derivatives to the corn protein zein studied by high-performance liquid chromatography.

The interaction of 12 substituted phenol, three aminophenol and four substituted aniline derivatives with the corn protein zein was studied on zein-coated silica and alumina stationary phases by high-performance liquid chromatography using bidistilled water as mobile phase. Solutes were eluted from the zein-coated supports with different retention times indicating that they bind to the protein with different forces. They were more strongly retained on silica-based than on alumina-based support proving that the original adsorptive character of the support remains even after impregnation. The retention of solutes on both zein-coated stationary phases significantly depended on the steric and electronic parameters of solutes and was independent of the calculated and measured lipophilicity parameters, indicating that hydrophobic forces are not included in the interaction of zein with these class of solutes. It has been concluded that the interaction is governed by steric and electrostatic forces.

Aniline Compounds↗

PubMed2001

Effect of molecular parameters on the binding of phenoxyacetic acid derivatives to albumins.

The interaction of 12 phenoxyacetic acid derivatives with human and serum albumin as well as with egg albumin was studied by charge-transfer reversed-phase (RP) thin-layer chromatography (TLC) and the relative strength of interaction was calculated. Each phenoxyacetic acid derivative interacted with human and bovine serum albumins whereas no interaction was observed with egg albumin. Stepwise regression analysis proved that the lipophilicity of the derivatives exert a significant impact on their capacity to bind to serum albumins. This result supports the hypothesis that the binding of phenoxyacetic acid derivatives to albumins may involve hydrophobic forces occurring between the corresponding apolar substructures of these derivatives and the amino acid side chains.

Acetates↗

PubMed2001

Interaction of surfactants with homologous series of peptides studied by reversed-phase thin-layer chromatography.

The relative strength of interaction between anionic (SDS) and nonionic surfactant (octaethoxylated oleyl alcohol, GEN) and homologous series of peptides was determined by reversed-phase thin-layer chromatography (RP-TLC) carried out on alumina layers impregnated with paraffin oil. The relative strength of interaction was calculated and was correlated with the physicochemical parameters of peptides. It was established that each peptide interacted with both surfactants and with their mixture (1:1, m/m). The relative strength of interaction depended on the number of amino acid units in the peptide, side chain bulk and electronic properties and hydrophobicity of the amino acids. The impact of individual parameters highly depended on the character of surfactant. The data prove that the retention order of peptides can be modified by adding different surfactants and surfactant mixtures to the mobile phase resulting in improved separation.

Chromatography, Thin Layer↗

PubMed2001

Separation of strength and selectivity of mobile phase by spectral mapping technique.

The retention behaviour of seven monotetrazolium and nine ditetrazolium salts was studied in seven different mobile phases on alumina and impregnated alumina stationary phases. The strength and selectivity of the components of mobile phases were separately calculated by the spectral mapping technique. It was established that tetrahydrofuran (THF) has the highest solvent strength while the differences among ethanol, 1-propanol, 2-propanol and dioxane were relatively low. The selectivity of THF was also considerably different from those of other solvents. Hydrophobicity and electronic parameters were equally involved in the retention strength and selectivity of tetrazolium salts, indicating the mixed character of their interaction with the alumina stationary phase.

Sensitivity and Specificity↗

PubMed2001

In vitro study on the transfer of volatile oil components.

The following volatile oils were tested in vitro: chamomile (Matricaria recutica L.), peppermint (Mentha piperita L.) and sage (Salvia officinalis L.) to obtain information on which components of volatile oils or minerals are able to pass through the membranes under different conditions. The transfer of chamomile and peppermint oil from aqueous volatile oil to the stomach (pH=1.1) and then to the plasma (pH=7.5) was studied, and the transfer of sage oil through the skin (from pH=5.5 to pH=7.5) was examined. The transfer of some components was more favorable than that of others. The transfer of chamomile oil was faster to buffer pH=1.1 than from buffer pH=1.1 to buffer pH=7.5 and most of the components, except for chamazulene, passed through the membranes. In the case of peppermint the components went through the membranes in the first 15 min although the main components mostly remained in the initial solution. The sage oil transferred showed the same characteristics as the starting oil. A small amount of metal present in the volatile oils also passed through the membranes. The transfer of metals varied, depending on the time, type of the oil, metal quality and the conditions applied.

Hydrogen-Ion Concentration↗

PubMed2001

Quantitative relationship between the chemical structure of antisense nucleosides and their capacity to interact with cyclomalto-octaose.

The interaction of twelve 8-substituted-2'-deoxyadenosine and seventeen 5-substituted-2'-deoxyuridine derivatives (antisense nucleosides) with cyclomalto-octaose (GCD) was determined by charge-transfer chromatography and the relative strength of the interaction was calculated. The majority of antisense nucleosides (14 deoxyuridine and 11 deoxyadenosine derivatives) interacted with GCD, which probably led to inclusion complex formation. Stepwise regression analysis proved that the strength of interaction was related to the length of the apolar alkyl chain of substituents and the bulkiness of the nucleoside ring structure. The effect of double or triple bonds in the chain was negligible.

Cyclodextrins↗

PubMed2001

Solvent strength and selectivity on a porous graphitized carbon column separated by a spectral mapping technique using barbiturates as solutes.

A spectral mapping technique (SPM) was employed for separating the strength and selectivity of the retention of 41 barbituric acid derivatives and 5 organic modifiers on a porous graphitized carbon column (PGC). The potency values calculated by SPM were considered to be indicators of the capacity of drugs to bind to the surface of PGC and the capacity of organic modifiers to remove the drugs from the surface. The dimensionality of the multidimensional selectivity maps was reduced to two by a nonlinear mapping technique. Calculations indicated that molecular lipophilicity plays a negligible role in the strength and selectivity of retention, proving that the retention mechanism of PGC deviates from those of traditional reversed-phase stationary phases. Sterical and electronic parameters exerted the highest influence on the retention, emphasizing the importance of the polar interaction and the sterical correspondence between the surface of PGC and the solute molecules.

Algorithms↗