Authors:J. Canotilho, F. Costa, A. Sousa, J. Redinha, and M. Leitão
Several samples of terfenadine prepared by crystallization from different solvents under different experimental conditions
were studied. The DSC curves obtained at a heating rate of 1C min−1 afforded the temperature of melting and the mole fractions of the components of each sample. Certain of the samples were
composed of two solid phases mixed in molar ratios varying between nearly one and a single structural form. Three polymorphic
forms were identified.
Authors:M. Leităo, J. Canotilho, M. Cruz, J. Pereira, A. Sousa, and J. Redinha
Terfenadine samples prepared by crystallization in different media and supersaturation conditions were used to investigate
the polymorphism of the substance. The study was based on DSC melting curves. An empirical parametric equation was used for
modelling the experimental data. The signal recorded was resolved into the corresponding overlapping peak components by fitting
analysis. Four polymorphic phases were identified.
The example of polyethylene of low density (PELD) crystallization in ethylbenzene and some other alkylbenzenes presence demonstrates
the unsufficiency of formal liquidus curve knowledge for the description of phase equilibrium in amorphous-crystalline polymer-liquid
system. Experimental data affirming polymorphous structure of PELD crystalline phase and influence of the solvent on the order
of various regular structures formation in it are being reported.
It is shown that for porous systems filled with a solvent, if the temperature domains of crystallization and melting of the
solvent are well separated, DSC technique, combined with suitably chosen thermal cycles, provides crystallization and melting
curves which are independent of a) the mass of the material, b) the thermal contact between DSC pan and material and c) the
thermal conductivity of the material. This method called DSC fractionation is applied to butyl rubber containing small water
nodules. Thermoporosimetry is then applied to get the size distribution of mesoscopic solvent droplets.
Comparative analysis of several methods for purity determination using DSC is presented. This is based on a mathematical model including the construction of theoretical melting curves for two-component systems and the calculation of recorded melting curves with the help of a set of equations describing the formation of a DSC output signal. It is shown that the true accuracy of purity determinations in the range of impurity concentrations ¯x=0.005–0.02 does not exceed 30–50%.
Authors:Erika Orosz, Katalin Perkátai, Beatrix Kapusinszky, Ágnes Farkas, and István Kucsera
Simple real-time PCR assay with one set of primer and probe for rapid, sensitive qualitative and quantitative detection of Entamoeba histolytica has been used. Consensus sequences were used to amplify a species-specific region of the 16S rRNA gene, and fluorescence resonance energy transfer hybridization probes were used for detection in a LightCycler platform (Roche). The anchor probe sequence was designed to be a perfect match for the 16S rRNA gene of Entamoeba species, while the acceptor probe sequence was designed for Entamoeba histolytica, which allowed differentiation. The performed characteristics of the real-time PCR assay were compared with ELISA antigen and microscopical detection from 77 samples of individuals with suspected clinical diagnosis of imported E. histolytica infection. Stool and liver abscess pus samples were examined with analytical sensitivity of 5 parasites per PCR reaction. The melting curve means Tms (standard deviation) in clinical isolates were 54°C. The real-time assay was 100% sensitive and specific for differentiation of Entamoeba histolytica, compared with conventional ELISA or microscopy. This real-time PCR assay with melting curve analysis is rapid, and specific for the detection and differentiation of Entamoeba histolytica. The suitability for routine use of this assay in clinical diagnostic laboratories is discussed.
The physical–chemical properties and fatty acid composition of sheep subcutaneous, tallow, intestinal, and tail fats were
determined. Sheep fat types contained C16:0, C18:0, and C18:1 as the major components of fatty acid composition (19.56–23.40, 20.77–29.50, 32.07–38.30%, respectively). Differential scanning
calorimetry (DSC) study revealed that two characteristic peaks were detected in both crystallization and melting curves. Major
peaks (Tpeak) of tallow and intestinal fats were similar and determined as 31.25–24.69 and 7.44–3.90 °C, respectively, for crystallization
peaks and 15.36–13.44 and 45.98–44.60 °C, respectively, for melting peaks in DSC curves; but those of tail fat (18.29 and
−2.13 °C for crystallization peaks and 6.56 and 33.46 °C for melting peaks) differed remarkably from those of other fat types.
Authors:M. Kiss, F. Könczöl, N. Farkas, D. Lőrinczy, and J. Belagyi
The effect of free radicals obtained in hydroxyl and cerium(IV)-nitrilotriacetic acid free radical generating systems on contractile
proteins (actin, myosin and their complexes in glycerinated muscle fibres) was studied using differential scanning calorimetry
and spin trapping electron paramagnetic resonance technique. The analysis of spectra showed that selective attack of thiol
groups – Cys-257 and Cys-374 residues of actin, and among others Cys-707 residue of myosin – and random attack of sidechains
of the main proteins of muscle tissue produced structural and functional changes, which affected the ATP hydrolysis cycle
and very likely the dynamics of actin. The melting curves obtained on protein systems support the view that global conformational
changes accompany the local damage of free radicals.
The melting process of constrained nylon 6 fibers has been studied to estimate the true melting point of its original crystals.
The melting peak became simpler in shape and shifted to higher temperature with increasing fiber-axis restricting force. When
heating rate, β, was increased, the temperature where the melting curve initially departs from its baseline, Tsm, decreased
steeply in the range of 45 to 60C min-1, and increased linearly with increasing β above 60C min-1. By linear extrapolation of Tsm to 0C min-1, the temperature of ca 190C was obtained for the melting temperature of the original nylon 6 crystals. This seems to correspond
to the zero-entropy-production melting of the most imperfect crystallites of the nylon 6 fabric.