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Djakovic-Sekulic T.,University of Novi Sad | Lozanov-Crvenkovic Z.,University of Novi Sad | Mandic A.,Institute for Food Technology | Uscumlic G.,University of Belgrade | Keleman S.,University of Novi Sad
Chromatographia | Year: 2011

In this study 18 hydantoin derivatives were investigated by means of reversed-phase LC on C-18 stationary phase and methanol-water eluent. Quantitative structure-retention relationship study has been applied in order to understand factors that affect the chromatographic behavior which is closely correlated to the activity (ED50 values). A multiple linear regression procedure was used to model the relationships between molecular descriptors and retention of the hydantoin derivatives. The best quantitative structure-activity relationship (QSAR) models were further validated by a leave-one-out technique as well as by the calculation of statistical parameters for the established theoretical models. High agreement between experimental and predicted data obtained in the validation procedure indicated good quality of the derived QSAR models. © 2011 Springer-Verlag. Source

Djakovic-Sekulic T.,University of Novi Sad | Mandic A.,Institute for Food Technology
Current Computer-Aided Drug Design | Year: 2012

In the study, 18 antiepileptic hydantoin analogues were investigated by means of reversed-phase HPLC on C-18 stationary phase and eluent acetonitrile-water. Quantitative structure-retention relationship (QSRR) study has been applied in order to understand factors that affect the retention which is closely correlated to the activity (ED 50 values). To overview the compounds for similarities and dissimilarities principal component analysis (PCA) has been applied. Six multiple linear regression models based on the most relevant descriptors were developed. Descriptors for MLR were selected according to variable importance calculated by partial least squares (PLS) analysis. Besides ALOGP the most important is aromatic ratio for mobile phases with more than 45% of acetonitrile, as well as electrotopological states when the % of acetonitrile is less than 40%. High agreement between experimental and predicted retention, obtained in the validation procedure, indicated the good quality of the derived QSRR models. For individual linear models, crossvalidation squared correlation coefficients (Q 2) ranging from 0.697 to 0.837 were obtained. The residual values (difference between observed and calculated) agreed well within experimental error. Additionally, models were compared in terms of the smallest residual value by recently developed method of ranking based on the sum of ranking differences (SRD). © 2012 Bentham Science Publishers. Source

Filipovic J.,Institute for Food Technology | Filipovic N.,University of Novi Sad | Filipovic V.,Mlinpek Institute
Journal of the Serbian Chemical Society | Year: 2010

The daily intake of dietary fibres in highly industrialized countries is at a low level and, therefore, adversely affecting human health. The objective of this research was to analyze the influence of different commercial fibres (originating from sugar beet pulp fibrex, and Jerusalem artichoke inulin HPX and GR) in yeast dough at a level of 5 %, on the rheological properties of dough and the quality of bread during frozen storage. Frozen dough characteristics were determined using a Brabender maturograph and test baking was followed according the AACC procedure. The dough was frozen at-18 °C and stored over a period of 60 days. The results concerning the dough (proving time and stability) and bread quality (volume and crumb quality) were statistically analyzed by multivariance Manova and discriminative analysis, which indicated that there was a significant difference between dough without fibres and dough with different fibres (fibrex, inulin HPX and GR). The discrimination coefficient points that the greatest influence of fibres on the final proof and proving stability is after 30 days (6.250) and after 0 days (6.158), respectively, but the greatest influence of fibres on bread volume and bread crumb quality (15.488 and 3.638, respectively) can be expected on non frozen dough, due to above mention their adverse the effect on gluten network. Source

Brouwers J.F.,University Utrecht | Boerke A.,University Utrecht | Silva P.F.N.,University Utrecht | Garcia-Gil N.,University Utrecht | And 5 more authors.
Biology of Reproduction | Year: 2011

We report on the presence and formation of cholesterol oxidation products (oxysterols) in bovine sperm. Although cholesterol is the most abundant molecule in the membrane of mammalian cells and is easily oxidized, this is the first report on cholesterol oxidation in sperm membranes as investigated by state-of-the-art liquid chromatographic and mass spectrometric methods. First, oxysterols are already present in fresh semen samples, showing that lipid peroxidation is part of normal sperm physiology. After chromatographic separation (by high-performance liquid chromatography), the detected oxysterol species were identified with atmospheric pressure chemical ionization mass spectrometry in multiple-reaction-monitoring mode that enabled detection in a broad and linear concentration range (0.05-100 pmol for each oxysterol species detected). Second, exposure of living sperm cells to oxidative stress does not result in the same level and composition of oxysterol species compared with oxidative stress imposed on reconstituted vesicles from protein-free sperm lipid extracts. This suggests that living sperm cells protect themselves against elevated oxysterol formation. Third, sperm capacitation induces the formation of oxysterols, and these formed oxysterols are almost completely depleted from the sperm surface by albumin. Fourth, and most importantly, capacitation after freezing/thawing of sperm fails to induce both the formation of oxysterols and the subsequent albumin-dependent depletion of oxysterols from the sperm surface. The possible physiological relevance of capacitationdependent oxysterol formation and depletion at the sperm surface as well as the omission of this after freezing/thawing semen is discussed. © 2011 by the Society for the Study of Reproduction, Inc. Source

Pojic M.,Institute for Food Technology | Mastilovic J.,Institute for Food Technology | Majcen N.,Metrology Institute of the Republic of Slovenia
Food Chemistry | Year: 2012

The robustness assessment is a part of a method validation protocol, during which several characteristics of an analytical method are also evaluated (e.g. accuracy, repeatability, reproducibility, linearity, intermediate precision, measurement uncertainty) in order to assess its fitness for purpose. The purpose of robustness assessment of the near infrared spectroscopy method (NIRS) is to indicate which factor significantly influence the obtained results, as well as to point to the potential problems that might occur in the routine application of the method. The assessment of robustness of the NIRS method included variation of certain operational and environmental factors at three level (-1, 0, 1) by applying univariate (one-variable-at-a-time, OVAT) and multivariate (multivariate-at-a-time, MVAT) approach to the experimental design. Operational and environmental factors that were varied included the number of subsamples to be measured in the NIRS measurement (1), environmental temperature (2), sample temperature (3), environmental air humidity (4), instrument voltage (5) and lamp aging (6). Regardless the applied experimental design, external factors with significant influence on obtained NIRS results were indicated, as well as pointed the potential problems that might occur in the routine application of the method. In order to avoid them, every effort should be made to stabilize instrument and sample temperature and to standardize the homogeneity and number of subsamples to be measured in NIRS measurement. Moreover, the obtained results highlighted the necessity that the NIRS instruments should work through a voltage regulator. © 2012 Elsevier Ltd. All rights reserved. Source

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