Differential Scanning Calorimetry Patterns Research Articles

Mechanical Properties and Crystallization Behavior of Polycarbonate/Polypropylene Blends

The mechanical properties, morphology, and crystallization behavior of polycarbonate (PC)/polypropylene (PP) blends, with and without compatibilizer, were studied by tensile and impact tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The tensile and impact strengths of PC/PP blends decreased with increasing the PP content due to poor compatibility between the two phases. But the addition of compatibilizer improved the mechanical properties of the PC/PP blends, and the maximum value of the mechanical properties, such as tensile and impact strengths of PC/PP (80/20 wt%) blends, were obtained when the compatibilizer was used at the amount of 4 phr. The SEM indicated that the compatibility and interfacial adhesion between PC and PP phases were enhanced. DSC results that showed the crystallization and melting peak temperatures of PP increased with the increase of the PP content, which indicated that the amorphous PC affected the crystallization behavior. However, both the PC and compatibilizer had little effect on the crystallinity of PP in PC/PP blends based on both the DSC and XRD patterns.

Solid state of aceclofenac: characterization, transformation

The objective of this work was to investigate the existence of polymorphs and pseudopolymorphs of aceclofenac which is a peripherally acting, non-steroidal anti-inflammatory analgesic with anti-inflammatory, antiarthritic and antipyretic activities. Three crystal forms of aceclofenac have been isolated by recrystallization and characterized by differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD) and thermogravimetric analysis. The DSC and PXRD patterns of the three crystal forms of aceclofenac were different respectively. After storage of 1 month at 0 % RH (silica gel, 20 °C), 52 % RH (saturated solution of Na2Cr2O7·2H2O/20 °C) and 95 % RH (saturated solution of Na2HPO4/20 °C), Form 1 and Form 3 (from methylethyl ketone) were not transformed, but Form 2 (from DMSO) was transformed to Form 1 at 95 % RH.

Preparation of Zaleplon Microparticles Using Emulsion Solvent Diffusion Technique

Zaleplon is a BCS class II drug suffering from poor solubility. In a trial to improve its dissolution, emulsion solvent diffusion method (ESD) was used to prepare zaleplon microparticles using sodium lauryl sulfate (SLS) as surfactant. Optimization of drug system was achieved. Particle size values of the prepared microparticles were ranged from 6.57 μm to 20.30 μm with narrow particle size distribution range. Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) were used for the characterization of the prepared systems. DSC and XRD patterns showed that the zaleplon microparticles possessed decreased crystallinity. Dissolution studies demonstrated that the systemized zaleplon microparticles exhibited significantly enhanced dissolution rate when compared to pure zaleplon. A correlation could be observed between the microparticle morphology and the dissolution rate, where zaleplon microparticles that exhibited the fastest dissolution profiles had a distinctive rod shape compared to the other systems. In contrast, pure zaleplon powder appeared as irregularly-shaped particles. In conclusion, the dissolution rate of zaleplon can be enhanced to a great extent by ESD technique.

Formulation of a Poorly Water-Soluble Drug Sirolimus in Solid Dispersions to Improve Dissolution

An attempt has been made to enhance solubility and dissolution of sirolimus by solid dispersion and complexation technique using various hydrophilic excipients. Sirolimus an immunosuppressant agent has low bioavailability due to its low aqueous solubility. Solid dispersion of sirolimus in PEG-6000, Poloxamer-188, and Mannitol were prepared by fusion and solvent evaporation method. Beta-CD complexation of sirolimus was prepared by kneading method. In vitro dissolution studies were carried out in 0.4% SLS in water, which showed that the solid dispersion containing PEG 6000 (1:1), which was prepared by solvent evaporation method, showed faster dissolution rate than the other formulations and β-cyclodextrin complex. Solid dispersions containing PEG 6000 was further investigated by x-ray powder diffraction, differential scanning calorimetry (DSC), and FTIR. X-ray powder diffraction and DSC patterns suggested that the drug state changed from crystalline to amorphous form in the formulation.

Solid state of CG-400549, a novel FabI inhibitor: Characterization, dissolution, transformation

The polymorphic and pseudopolymorphic forms of CG-400549, a novel FabI inhibitor with potent in vivo activity were prepared and characterized by differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD) and thermogravimetric analysis (TG). Seven crystal forms of CG-400549, one anhydrate and six solvates, have been isolated by recrystallization and the DSC and PXRD patterns of the seven crystal forms of CG-400549 were different respectively. The dissolution patterns of these seven crystal forms of CG-400549 were studied and they showed significant differences in the dissolution rate. After storage of 1 month at 0% RH (silica gel, 20°C), 52% RH (saturated solution of Na(2)Cr(2)O(7)2H(2)O/20°C) and 95% RH (saturated solution of Na(2)HPO(4)/20°C), all crystal forms were not transformed.

Assessing the progress of degradation in polyurethanes by chemiluminescence and thermal analysis. II. Flexible polyether- and polyester-type polyurethane foams

The thermooxidative and thermal stability of polyether- and polyester-type polyurethane foams were investigated by non-isothermal chemiluminescence (CL), differential scanning calorimetry (DSC) and thermogravimetry (TG). In the presence of air and humidity, the effect of various routes and conditions of polyurethane ageing (induced thermally or by light) on the chemiluminescence, DSC and thermogravimetry patterns was assessed. The rate constants determined from non-isothermal thermogravimetry and chemiluminescence measurements at 250 °C and their not very pronounced dependence on the atmosphere of degradation indicated that depolymerisation of the polyurethane containing the aliphatic polyester and aromatic polyisocyanate moieties preceded or occurred in parallel with thermal oxidation. Under conditions of 50% relative humidity, samples of the polyester-type polyurethane, aged either by light or thermally, as well as specimens of the polyether-type polyurethane, aged by light, gave increased amounts of carbonaceous residue when heated in nitrogen to 550 °C.

Solid State of Tulobuterol : Characterization, Dissolution, Transformation

The objective of this work was to investigate the existence of new crystal forms of tulobuterol which is used to prevent morning asthma attacks by agonist and the transformation of crystal forms. Three crystal forms of tulobuterol have been isolated by recrystallization and Form 2 was transformed to Form 4 at 52% RH and 95% RH and these four crystal forms are characterized by differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD) and thermogravimetric analysis (TG). The DSC and PXRD patterns of four crystal forms of tulobuterol were different respectively. The dissolution patterns of these three crystal forms of tulobuterol were studied and they showed significant differences in the dissolution rate. After storage of 2 months at 0% RH (silica gel, ), 52% RH (saturated solution of ) and 95% RH (saturated solution of ), Form 1 and Form 3 were not transformed. But Form 2 was transformed to Form 4 at 52% RH and 95% RH.

Crystal forms of atorvastatin

The objective of this work was to investigate the existence of new polymorphs and pseudopolymorphs of atorvastatin and the transformation of crystal forms. Three crystal forms of atorvastatin have been isolated by recrystallization and characterized by powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TG). The PXRD and DSC patterns of the three crystal forms were different respectively and it was confirmed that Form 3 is a new crystal form. After storage of 2 years at room temperature, this new crystal form was not transformed and it was shown to have a good physical stability.

COMPARATIVE STUDY OF THE DSC PATTERN, COLOR, TEXTURE AND WATER-BINDING CAPACITY OF RAINBOW TROUT MUSCLE DURING HEATING

ABSTRACT The effect of heating the muscle of rainbow trout at different temperatures ranging from 30 to 70C on thermal stability, texture, water-holding ability and color was investigated with regard to the possibility of discriminating between thermally treated and untreated fish muscle. Including the skin of fish it was possible to differentiate heat-treated fish in 5C steps in the range of 35–65C by means of their differential scanning calorimetry (DSC) patterns. Heating the fish muscle resulted in a marked increase in lightness with rising temperature as well as significant changes in hardness (increase) and water-holding capacity (decrease). Heating effects were compared with those of pressure treatments at 100 and 200 MPa for 20 min. The DSC patterns of both trout muscle and skin were comparable for samples that were pressure treated at 200 MPa or heated at 40C. PRACTICAL APPLICATIONS Differential scanning calorimetric (DSC) patterns of both muscle proteins and skin proteins of rainbow trout preheated at temperatures ranging from 30 to 70C show a gradual denaturation of protein fractions, with myosin being the most susceptible and almost completely denatured in samples preheated at 50C. In samples preheated at 70C, the actin peak also disappeared and proteins available in muscle and skin were fully denatured. This offers the possibility of checking whether heat treatment has been performed (e.g., in the case of illegal tariff savings) or whether minimum cooking temperatures have been met (e.g., in the case of hot smoking).

Differential scanning calorimetry study of glycerinated rabbit psoas muscle fibres in intermediate state of ATP hydrolysis

BackgroundThermal denaturation experiments were extended to study the thermal behaviour of the main motor proteins (actin and myosin) in their native environment in striated muscle fibres. The interaction of actin with myosin in the highly organized muscle structure is affected by internal forces; therefore their altered conformation and interaction may differ from those obtained in solution. The energetics of long functioning intermediate states of ATP hydrolysis cycle was studied in muscle fibres by differential scanning calorimetry (DSC).ResultsSETARAM Micro DSC-II was used to monitor the thermal denaturation of the fibre system in rigor and in the presence of nucleotide and nucleotide analogues. The AM.ADP.Pi state of the ATP hydrolysis cycle has a very short lifetime therefore, we mimicked the different intermediate states with AMP.PNP and/or inorganic phosphate analogues Vi and AlF4 or BeFx. Studying glycerol-extracted muscle fibres from the rabbit psoas muscle by DSC, three characteristic thermal transitions were detected in rigor. The thermal transitions can be assigned to myosin heads, myosin rods and actin with transition temperatures (Tm) of 52.9 ± 0.7°C, 57.9 ± 0.7°C, 63.7 ± 1.0°C. In different intermediate states of the ATP hydrolysis mimicked by nucleotide analogues a fourth thermal transition was also detected which is very likely connected with nucleotide binding domain of myosin and/or actin filaments. This transition temperature Tm4 depended on the mimicked intermediate states, and varied in the range of 66°C – 77°C.ConclusionAccording to DSC measurements, strongly and weakly binding states of myosin to actin were significantly different. In the presence of ADP only a moderate change of the DSC pattern was detected in comparison with rigor, whereas in ADP.Pi state trapped by Vi, AlF4 or BeFx a remarkable stabilization was detected on the myosin head and actin filament which is reflected in a 3.0 – 10.0°C shift in Tm to higher temperature. A similar effect was observed in the case of the nonhydrolyzable AMP.PNP analogue. Differential DSC measurements suggest that stabilization actin structure in the intermediate states of ATP hydrolysis may play an additional role in actin-myosin interaction.

Catalytic properties of bimetallic NiCoB nanoalloy catalysts for hydrogenation of p-chloronitrobenzene

Nanosized NiCoB amorphous alloy catalysts with Co/Ni ratios varying from 0 to 3 were prepared by chemical reduction of nickel acetate and cobalt acetate with sodium borohydride in methanolic solution at room temperature under N 2 gas with vigorous stirring. The catalysts were characterized by nitrogen sorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and X-ray photoelectron spectroscopy (XPS). NiCoB catalysts were tested for liquid-phase hydrogenation of p-chloronitrobenzene ( p-CNB). The liquid-phase hydrogenation of p-CNB was carried out at 1.2 MPa hydrogen pressure, 373 K reaction temperature, methanol as reaction medium, 500 rpm stirring speed, 0.2 M p-CNB and 2 mmol Ni catalysts. The molar ratios of Co/Ni in the starting materials affected the concentrations of boron bounded to the nickel and cobalt metals, resulting in the change of surface area, electronic structures of the metals and catalytic activities of the catalysts. Nickel is enriched on the surface. Doping Co in NiB decreased the particle size and increased the stability of the NiCoB amorphous alloys. Doping Co in NiB increased the boron content, which in turn increased the electron density of Ni. The sample NiCoB(1:0.1) (the value in the bracket is the Ni:Co ratio in bulk) had the highest surface area of 23.5 m 2/g and the smallest particle size. TEM micrographs show that Co can reduce the particle size of NiB catalyst. DSC patterns demonstrated that the addition of cobalt suppressed the growth of crystalline structure of NiB. Adding small amount of cobalt to the NiB catalyst increased the surface area and reaction activity, but decreased the selectivity for the desired product, p-chloroaniline ( p-CAN). However, overdosed cobalt had an opposite effect on Ni catalyst, i.e., reduced the reaction activity and increased the selectivity for p-CAN. The Co-dopant could weaken the extent of electron donation from the Ni atoms to the aromatic ring in p-CAN, which would further suppress the hydrodechlorination of p-CAN. The selectivity for p-CAN was also a function of conversion of p-CNB. Based on the electron transfer between elemental nickel and boron, NiCoB(1:0.1) had the most d-band electrons and the highest activities in hydrogenation of nitro group and dechlorination. The results can be interpreted by the electronegativity of the functional groups.

パーム油の晶出温度が結晶化に及ぼす効果 ＩＩ １，３‐ジパルミトイル‐２‐オレオイル‐グリセロール（ＰＯＰ）及び１，２‐ジオレイル‐３‐パルミトイル‐グリセロール（ＰＯＯ）の２成分系（原標題は英語）

The crystallization of Palm Oil and the thermal features of this process were examined. The manner in which Palm Oil crystals melted was noted to differ significantly with temperature, particularly in the case of crystallization at 10°C. Triacylglycerin in Palm Oil is comprised of POP (1,3-dipalmitoyl-2-oleoyl-glycerol) at 30% and POO (1,2-dioleoyl-3-palmitoyl-glycerol) at 20%. Examination was thus made of the crystallization of pure POP and POO and a mixture of these by differential scanning calorimetry (DSC) and X-ray diffractometry (XRD). DSC patterns of the POP/POO (60/40) mixture and Palm Oil crystallized at 10°C were noted to be essentially the same. The mixture crystallized at 10°C showed 64 A and 43 A spacings by XRD, thus indicating triple-chain length and double-chain length structures to be present only in crystals formed at 10°C while only the double-chain length structure to be present in crystals produced of other temperatures. These findings would possible be explanation for variation in triacylglycerin content in crystals and why the POP/POO (60/40) mixture behaves in the manner of Palm Oil.

Exothermic thermal reaction of dopamine with 3,5‐dinitrobenzoic acid

AbstractPyrolysis of the crystalline 1 : 1 molecular complex DAċdnba, which was prepared from cocrystallization of dopamine (DA) and 3,5‐dinitrobenzoic acid (dnba), was studied. This cocrystal decomposed violently at the melting‐point, leading to the formation of a black solid along with a tiny amount of 3‐amino‐5‐nitrobenzoic acid (1). The pyrolysis reaction was followed by differential scanning calorimetry (DSC) and one large exothermic peak was observed at the decomposition temperature. In view of the DSC patterns for cocrystal DAċdnba and other compounds, it seems that both a catechol moiety and an amino group of DA in addition to a strong electron acceptor such as dnba are required for the appearance of the exothermic peak. On the basis of (a) elemental analysis of the black solid and (b) other pyrolysis experiments for cocrystals PAċdnba (PA: β‐phenylethylamine), BAċdnba (BA: benzylamine), DMDAċdnba (DMDA: O,O′‐dimethyldopamine) and DHBAċdnba (DHBA: 3,4‐dihydroxybenzylamine), it is assumed that the black solid was formed mainly through elimination of more than one molecule of water from one molecule of DAċdnba. Copyright © 2003 John Wiley & Sons, Ltd.

Effect of gamma-sterilization process on PLGA microspheres loaded with insulin-like growth factor-I (IGF-I).

The influence of gamma-sterilization on the physicochemical properties of a controlled release formulation for the insulin-like growth factor-I (IGF-I) was investigated in this study. Recombinant human insulin-like growth factor-I (rhIGF-I) was efficiently entrapped in poly (D,L-lactide-co-glycolide) (PLGA) microspheres by water-in-oil-in-water (W/O/W) solvent evaporation technique. Microspheres were irradiated at a dose of 25kGy and evaluated by means of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The stability of the released protein was investigated by circular dichroism (CD) and sodium dodecyl sulfate polyacrilamide gel electrophoresis (SDS-PAGE). No difference was noticed in microsphere size and morphology before and after irradiation. Drug loading remains essentially the same after the sterilization process. However, rhIGF-I aggregation was detected by electrophoresis. In addition, subtle changes in DSC pattern were noticed for irradiated microspheres. In vitro drug release from irradiated microspheres was also affected, showing an increased burst effect. From this results it can be concluded that gamma-sterilization process causes changes in the properties of rhIGF-I loaded microspheres.

Preformulation compatibility studies of etamsylate and fluconazole drugs with lactose by DSC

Chemical compatibility of two drugs, namely, etamsylate and fluconazole was studied with lactose as excipient, employing differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. The DSC patterns recorded for the mixtures of both the drugs with the common excipient (lactose) indicated that fluconazole as well as etamsylate were incompatible with lactose at high temperatures. X-ray diffraction patterns recorded for pure drugs and lactose and the mixtures of individual drugs with lactose prepared at room temperature by intimate grinding of the components revealed incompatibility of both the drugs with lactose also at room temperature.

Analysis of nucleotide myosin complexes in skeletal muscle fibres by DSC and EPR

The internal dynamics and thermal unfolding of fibre bundles prepared from rabbit psoas muscle has been studied in the presence of nucleotides by differential scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) spectroscopy. Using ADP, adenosine 5′-triphosphate (ATP), AMP.PNP and inorganic phosphate analogue orthovanadate (V i), AlF 4 − and BeF 3 −, three intermediate states of the ATP hydrolysis cycle were simulated in glycerinated muscle fibres. In the main transition of the DSC pattern, three overlapping endotherms were detected in rigor, four in strongly as well as weakly binding state of myosin to actin. Deconvolution procedure showed that the transition temperature of 67.5 °C was the same for rigor and strong binding state of myosin. In contrast, nucleotide binding induced shift of the melting temperatures of 52 °C and 67.5 °C, appeared a new fourth peak at 74 and 77 °C and produced changes in the calorimetric enthalpies. The changes of the parameters of the peak functions suggest global rearrangements of the internal structure in myosin heads in the intermediate states. In the presence of ADP or ATP plus phosphate analogue orthovanadate or beryllium fluoride, aluminium fluoride, the conventional EPR spectra of spin-labeled muscle fibres showed large changes in the ordering of the probe molecules, and a new distribution of spin labels appeared. ATP plus orthovanadate induced the orientation disorder of myosin heads; the random population of spin labels gave evidence of large local conformational and motional changes in the internal structure of myosin heads. Saturation transfer EPR measurements reported increased rotational mobility of spin labels in the presence of ATP plus phosphate analogues corresponding to weakly binding state of myosin to actin.

Thermoanalytical study of polymorphic transformation in Fluconazole drug

Polymorphic transformation in Fluconazole (I) drug has been studied employing differential scanning calorimetry (DSC), X-ray diffraction and FT-IR techniques. Fluconazole (I) exhibited the sharp melting point at 138.4 °C. Considerable under cooling was, however, observed for the drug during cooling. No indication of freezing of molten Fluconazole (I) was evident in the DSC curve recorded up to a temperature of 25 °C in the cooling cycle. Reheating of the sample obtained after cooling, produced the DSC pattern much different compared to that obtained in the first heating and consisted of a sharp exothermic peak beginning at 81 °C preceding the twin endothermic peak with an onset temperature of 135.3 °C. In addition to these two peaks, a small endothermic peak was also observed around 31 °C, which could be attributed to a glass transition with an associated relaxation. The precise glass transition temperature derived from the data collected from six different independent experiments was found to be (31.67±0.13) °C. X-ray diffraction pattern of the Fluconazole (I) indicated that the as received sample was crystalline. The molten Fluconazole on cooling, however, produced a glassy amorphous mass. The amorphous product on heating to temperature >81 °C transformed to Fluconazole (II) which subsequently changed to Fluconazole (I) prior to melting. The split endothermic peak beginning at 135.3 °C recorded for the solidified Fluconazole sample is consistent with the observations made by X-ray diffraction. The observations made by employing DSC and X-ray diffraction were corroborated by FT-IR data on the samples isolated at different stages in the experiments.

Differential scanning calorimetry and circular dichroism spectrometry of walleye pollack myosin and light meromyosin.

The thermodynamic properties of myosin and its C-terminal fragment, light meromyosin (LMM), from walleye pollack, a typical cold-water fish efficiently utilized on an industrial scale, were analyzed by using differential scanning calorimetry (DSC) and circular dichroism (CD) spectrometry. Recombinant walleye pollack LMM expressed in Escherichia coli was also subjected to DSC and CD measurements for reference. The two proteins prepared from frozen surimi showed three endothermic peaks, the transition temperatures (T(m)) of which were quite similar, although overall DSC patterns differed considerably from one another. Their alpha-helical contents determined by CD were low compared to values reported before for other species. On the other hand, recombinant LMM gave four endothermic peaks at 27.4, 30.8, 36.5, and 43.4 degrees C in DSC and showed an alpha-helical content of approximately 80%. The peak at 27.4 degrees C could not be observed in walleye pollack LMM prepared from frozen surimi and thus was possibly attributed to its C terminus, because this extreme C-terminal region is supposedly truncated during preparation of LMM by tryptic digestion.

Nucleotide-induced changes in muscle fibres studied by DSC and TMDSC

Differential scanning calorimetry (DSC) was used in conventional and temperature-modulated mode to study the energetics of myosin in skeletal muscle fibres in different states of the actomyosin ATPase cycle. Psoas muscle fibres from rabbit were used in the experiments with and without the presence of nucleotides (ATP, ADP, AMP–PNP) and ATP or ADP+orthovanadate. In the complex DSC pattern, the higher transition referred to the head region of myosin. The enthalpy of the thermal unfolding depended on the nucleotides, the conversion from a strongly attached state of myosin to actin to a weakly binding state was accompanied with an increase of the transition temperature which was due to the change of the affinity of nucleotide binding to myosin. This was more pronounced in TMDSC mode, indicating that the strong-binding state and rigor state differ energetically from each other. The different transition temperatures indicated alterations in the internal microstructure of myosin head region. The monoton decreasing TMDSC heat capacities show that the C p of biological samples should not be temperature independent.

The effect of nucleotides (ADP and ADP + V i) on the thermal stability of rat uterus

Thermal unfolding of stripes prepared from rat uterus has been studied in the presence of nucleotides by differential scanning calorimetry (DSC). Using ADP, ATP and inorganic phosphate analogue orthovanadate, three intermediate states of the ATP hydrolysis cycle were simulated in the uterus stripes. In the main transition of the DSC pattern at least four overlapping endotherms were detected in rigor (AM), in strongly binding (AM·ADP) and weakly binding state (AM·ADP·V i) of myosin to actin. It was found that nucleotide binding induced a shift of the main melting temperatures (from 60.7 to 61.1°C) and produced changes in the total calorimetric enthalpies (0.45 J/g for rigor, 0.4 J/g for strong binding, and 0.6 J/g for weak binding state). In the Krebs–Ringer bicarbonate buffer containing 100 nM estrogen (Oe) the main transition temperature shifted to 62.4°C and the total enthalpy change was 0.56 J/g. It seems to be an intermediate phase between the strong and weak binding state. The changes of the parameters of the peak functions suggest global rearrangements of the internal structure in myosin heads in the intermediate states.