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PubMed2005

Properties of normal and glycated human hemoglobin in presence and absence of antioxidant.

We present a novel approach to study properties of normal (HbA) and nonenzymatically glycated (HbA(Ic), HbA(Ia+b)) human hemoglobin using absorption spectroscopy and differential scanning calorimetry. The effect of the presence of the antioxidant fisetin on glycation of HbA is studied. Here, absorption spectroscopy has been fruitfully exploited to observe the formation of the glycated hemoglobin. With the differential scanning calorimetry, we studied the thermal unfolding of the protein hemoglobin at various conditions. The thermogram of the pure HbA showed two transition regions, with the occurrence of a partially unfolded intermediate state (the formation of which is mainly reversible) prior to complete denaturation (irreversible process). The denaturation temperature of HbA was found to be strongly dependent on the heating rate. Furthermore, there is a significant cooperativity between the two transition regions in pure HbA. The overall denaturation for the glycated hemoglobin takes place at a lower temperature, suggesting a decrease in the stability of the protein when it is glycated. In presence of fisetin, glycation is inhibited to a certain extent and the thermograms match well with that of normal HbA. Implications of the results are discussed.

Antioxidants↗
PubMed2006

Length and pH-dependent energetics of (CCG)n and (CGG)n trinucleotide repeats.

Trinucleotide repeats are involved in a number of debilitating diseases such as fragile-X syndrome and myotonic dystrophy. Eighteen to 75 base-long (CCG)(n) and (CGG)(n) oligodeoxynucleotides were analysed using a combination of biophysical (UV-absorbance, differential scanning calorimetry) and biochemical methods (non-denaturing gel electrophoresis, enzymatic footprinting). All oligomers formed stable intramolecular structures under near physiological conditions with a melting temperature which was only weakly dependent on oligomer length. Thermodynamic analysis of the denaturation process by UV-melting and calorimetric experiments revealed a length-dependent discrepancy between the enthalpy values deduced from model-dependent (UV-melting) and model-independent experiments (calorimetry), as recently shown for CTG and CAG trinucleotides (Nucleic Acids Res. 33 (2005) 4065). Evidence for non-zero molar heat capacity changes was also derived from the analysis of the Arrhenius plots. Such behaviour is analysed in the framework of an intramolecular "branched" or "broken" hairpin model, in which long oligomers do not fold into a simple long hairpin-stem intramolecular structure, but allow the formation of several independent folding units of unequal stability. These results suggest that this observation may be extended to various trinucleotide repeats-containing sequences.

Base Sequence↗
PubMed2006

Arsenite interactions with phospholipid bilayers as molecular models for the human erythrocyte membrane.

There are scanty reports concerning the effects of arsenic compounds on the structure and functions of cell membranes. With the aim to better understand the molecular mechanisms of the interaction of arsenite with cell membranes we have utilized bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. The capacity of arsenite to perturb the bilayer structures was determined by X-ray diffraction and fluorescence spectroscopy, whilst the modification of their thermotropic behaviour was followed by differential scanning calorimetry (DSC). The experiments carried out by X-ray diffraction and calorimetry clearly indicated that NaAsO(2) interacted with DMPE and modified its thermotropic behaviour. No such information has been so far reported in the literature.

Arsenites↗
PubMed2005

Starch crystal solubility and starch granule gelatinisation.

The solubility and dissolution behaviour of A- and B-type crystals of short chain amylose were measured both directly and using differential scanning calorimetry in the temperature range 30-110 degrees C. Dissolution in the calorimeter was affected by super-heating to the extent of 24-28 degrees C. Following trends previously found by calorimetry the B-type crystal polymorph was more soluble than the A-type. Analysis of the chain composition of the dissolved material revealed a preferential solubilisation of the short chains at the lower temperatures. The solubility of both crystal polymorphs and the magnitude of the preferential solubilisation effect was reduced in the presence of 30% w/w sucrose. A comparison of calorimetric measurements of crystal dissolution and the gelatinisation of native granular waxy maize and potato starches found some broad similarities, such as transition temperatures and their composition dependence, and some differences, such as the relatively narrow temperature range of granular gelatinisation, which reflects its cooperative nature.

Amylose↗
PubMed2005

Analytical performances of two liquid crystals and their mixture as stationary phases in capillary gas chromatography.

Comparative gas chromatographic applications of two new liquid crystals called LCa and LCb and their equimolar mixture LC(a+b) were investigated. The thermal properties of LCa, LCb and LC(a+b) were established with differential scanning calorimetry (DSC) and polarizing microscopy. Differential scanning calorimetry of LC(a+b) showed that the melting or clearing temperature was intermediate between the corresponding temperatures of the pure compounds. Polarizing microscopy showed that the liquid crystal phase of A + B was nematic. The chromatographic separation abilities LCa, LCb and LC(a+b) were studied using fused silica capillary columns. Interesting analytical performances were obtained: isomeric separation of aromatics, polyaromatics, phenols.

Calorimetry, Differential Scanning↗
PubMed2005

Differences in glycaemic status do not predict weight loss in response to hypocaloric diets in obese patients.

OBJECTIVE: The aim of our study was to detect differences in weigth loss with a hypocaloric diet in obese patients depending on their glycaemic status. SUBJECTS AND METHODS: A population of 76 obesity outpatients was analysed in a prospective way. The following variables were specifically recorded at basal time and after 3 months of hypocaloric diet (1200 kcal/day): weight, blood pressure, body mass index (BMI), waist circumference, and waist-hip ratio. Basal glucose, insulin, fibrinogen, cortisol, c-reactive protein, total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides blood levels were measured. HOMA was calculated. An indirect calorimetry, tetrapolar electrical bioimpedance and a serial assessment of nutritional intake with 3 days written food records were performed. RESULTS: The mean age was 46.9 +/- 17.1 years and the mean BMI 34.6 +/- 5.3. All subjects were weight stable during the 2 weeks period preceding the study (body weight change, 0.3 +/- 0.1 kg). Anthropometric measurements showed an average waist circumference (108.7 +/- 15.7 cm), waist-to-hip ratio (0.93 +/- 0.11), and average weight (88.7 +/- 16.9 kg). Bipolar body electrical bioimpedance showed a fat mass of 37 +/- 12.3 kg. Indirect calorimetry showed a resting metabolic rate (RMR) (1674.3 +/- 392 kcal/day). Patients were divided in to two groups by glycaemic status (group I: normal glycaemic metabolism, fasting glucose levels <109 mg/dl; n = 50) and (group II: impaired glycaemic metabolism, fasting glucose levels >110 mg/dl, n = 26). Waist circumference (I: 108 +/- 17.1cm vs. 104.6 +/- 16.7 cm; P < 0.05) and (II: 113.6 +/- 9.8 cm vs. 110.9 +/- 8.9 cm; P < 0.05), weight (I: 90.6 +/- 19.2 kg vs. 86.3 +/- 18.6 kg:P < 0.05) and (II: 89.2 +/- 11.3 kg vs. 86.4 +/- 11.6 kg: P < 0.05) and BMI (I: 34.2 +/- 5.6 vs. 33.7 +/- 5.5; P < 0.05) and (II: 34.8 +/- 4.2 vs. 34.2 +/- 4.6; P < 0.05) improved in both groups with hypocaloric diet. Blood systolic pressure, total cholesterol and LDL cholesterol improved in both groups, without statistical differences. In group II improved glucose levels and HOMA index, too. Patients of group II had higher systolic blood pressure, glucose, total cholesterol, LDL cholesterol, triglycerides, lipoprotein (a), RCP levels and HOMA index than patients in group I. ANOVA analysis did not show differences among weight loss in tertiles of HOMA and glucose. CONCLUSION: Ability to lose weight on a hypocaloric diet over a 3-month time period does not vary in obese patients as a function of glycaemic status. Improvement in cardiovascular risk factors is not related with glycaemic status, too.

Analysis of Variance↗
PubMed2006

The use of a new hydrophilic polymer, Kollicoat IR, in the formulation of solid dispersions of Itraconazole.

Kollicoat IR, a new pharmaceutical excipient developed as a coating polymer for instant release tablets, was evaluated as a carrier in solid dispersions of Itraconazole. The solid dispersions were prepared by hot stage extrusion. Modulated temperature differential scanning calorimetry and X-ray powder diffraction were used to evaluate the miscibility of the drug and the carrier. The pharmaceutical performance was evaluated by dissolution experiments, performed in simulated gastric fluid without pepsin (SGF(sp)). In the X-ray diffractograms no Itraconazole peaks were visible; the polymer on the other hand appeared to be semi-crystalline. Moreover, its crystallinity increased during the extrusion process due to exposure to heat and shear forces. Modulated temperature differential scanning calorimetry analysis showed that the drug and the polymer formed a two phase system. Separate clusters of glassy Itraconazole were present for drug loads of 40% or higher, indicating further phase separation. Dissolution measurements demonstrated a significantly increased dissolution rate for the solid dispersions compared to physical mixtures. Interestingly the physical mixture made up of glassy Itraconazole and Kollicoat IR (20/80, w/w) showed a dissolution rate and maximum that was much higher than that of the physical mixture made up of crystalline Itraconazole and that of pure glassy Itraconazole. The results of this study show that Kollicoat IR is a promising excipient for the formulation of solid dispersions of Itraconazole prepared by hot stage extrusion.

Antifungal Agents↗
PubMed2004

Glass transitions and viscoelastic properties of carbopol and noveon compacts.

Glass transitions of five varieties of Carbopol (acrylic acid polymers cross-linked with allyl sucrose or allyl pentaerythritol) and two varieties of Noveon (calcium salts of acrylic acid polymer cross-linked with divinylglycol) differing in cross-linking density and nature and content in residual solvents, were analysed (as compressed probes) by differential scanning calorimetry (DSC), modulated temperature differential scanning calorimetry (MTDSC), and oscillatory rheometry. All carbopol compacts showed a main glass transition, at a temperature between 130 and 140 degrees C, Tg, independently of their cross-linking degree and molecular weight. Additionally two batches of Carbopol 971P, which had greater contents in residual solvents, also presented a secondary transition at 65-70 degrees C. Sorption of water during storage of carbopol compacts at different relative humidity environments caused the Tg to strongly decrease. Compacts stored at 97.5% relative humidity have Tg below 0 degrees C and behave, at room temperature, as flexible hydrogels. The Gordon-Taylor/Kelley-Bueche equation only fit the dependence of Tg on water content well for carbopol compacts containing less than 15% water. The plasticizing effect of water was clearly evidenced in the considerable decrease in the storage and loss moduli of the compacts. Although the energy associated to the glass transitions of carbopol polymers, 0.40-0.50 Jg(-1) degrees C(-1), is high enough to be clearly detected by DSC, in some cases the evaporation of residual solvents may make it difficult to observe the Tg. This inconvenience is overcome using MTDSC or oscillatory rheometry. The decrease in Tg of carbopol caused by water sorption when compacts were stored at 97.5% R.H. explains why their loss (G") and storage (G') moduli at room temperature decreased four orders of magnitude. In contrast, in noveon varieties, calcium ions act as ionic cross-linkers of the carboxylic groups, providing rigid networks with much higher Tg, and storage and loss moduli. This explains that despite sorbing similar amounts of water to carbopol, the changes on the mechanical properties of noveon compacts were much less important (i.e., G' and G" decreased up to one order of magnitude).

Acrylic Resins↗
PubMed2006

Crystal modification of dipyridamole using different solvents and crystallization conditions.

Dipyridamole crystals having different types of habits, improved dissolution rate were prepared by recrystallization from selected solvents, such as acetonitrile, benzene and methanol (Method I); crystals have also been made by solvent change using methanolic solution of dipyridamole in the presence of 2% solutions of Tween-80, Povidone K30 and polyethylene glycol (PEG) 4000 (Method II). Scanning electron microscopy, X-ray powder diffractometry, IR spectrometry and differential scanning calorimetry were used to investigate the physicochemical characteristics of the crystals. The comparative dissolution behavior of the newly developed crystals and that of the untreated dipyridamole were also studied. It was found that the newly developed crystals were different from each other with respect to physical properties but are chemically identical. The crystals, obtained (Method I) from benzene and acetonitrile, produced needle shaped crystals and that obtained from methanol produced rectangular shaped crystals. But the crystals obtained (Method II) with the methanolic solution of the drug in the presence of Tween-80, Povidone K30 and PEG-4000 produced smooth needle shaped crystals. X-ray diffraction spectra and differential scanning calorimetry study of the newly developed crystals, clearly indicate that dipyridamole exist in different crystal modification. The dissolution rate of newly developed crystals was found to be greater than the pure drug dipyridamole. Stability studies at 40 degrees C (75% RH) for 1 month for the modified crystals as well as the pure drug did show some changes in the XRD and DSC but not in IR studies.

Calorimetry, Differential Scanning↗
PubMed2006

Study of thermal behaviour of sugar esters.

Sugar esters (SEs) are widely used in the pharmaceutical and food industries. They have a wide range of HLB values (1-16), and hence they can be applied as surfactants, or as solubility or penetration enhancers. SEs can be employed in hot-melt technology, because their melting points are low and they decompose only above 220 degrees C. The aims of this work were to study the thermal properties of SEs and to demonstrate differences between SEs with various HLB values. The results revealed that SEs with high or medium HLB values were vitrified by melting. Their glass transitions (T(g)) were determined by modulated differential scanning calorimetry. To visualize the changes in the samples during heating, hot-stage microscopy was used. Hydrophilic SEs were only softened, while lipophilic SEs were melted by heating. After melting and solidification, SEs have partially amorphous layered structures which slowly crystallize in time. Time-dependent solid-state changes (crystalline and amorphous phases) were observed, and analysed by means of differential scanning calorimetry and X-ray powder diffraction.

Calorimetry, Differential Scanning↗
PubMed2004

Solubilization of negatively charged DPPC/DPPG liposomes by bile salts.

The interactions of the bile salts sodium cholate (NaC) and sodium deoxycholate (NaDC) in 0.1 M NaCl (pH 7.4) with membranes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phosphatidylglycerol (DPPG) and mixtures of DPPC and DPPG at molar ratios of 3:1 and 1:1 were studied by means of high-sensitivity isothermal titration calorimetry (ITC), dynamic light scattering (DLS), and differential scanning calorimetry (DSC). The partition coefficients and the transfer enthalpies for the incorporation of bile salt molecules into the phospholipid membranes were determined by ITC. The vesicle-to-micelle transition was investigated by ITC, DLS, and DSC. The phase boundaries for the saturation of the vesicles and their complete solubilization established by ITC were in general agreement with DLS data, but systematic differences could be seen due to the difference in detected physical quantities. Electrostatic repulsion effects between the negatively charged bile salt molecules and the negatively charged membrane surfaces are not limiting factors for the vesicle-to-micelle transition. The membrane packing constraints of the phospholipid molecules and the associated spontaneous curvature of the vesicles play the dominant role. DPPG vesicles are transformed by the bile salts into mixed micelles more easily or similarly compared to DPPC vesicles. The saturation of mixed DPPC/DPPG vesicles requires less bile salt, but to induce the solubilization of the liposomes, significantly higher amounts of bile salt are needed compared to the concentrations required for the solubilization of the pure phospholipid systems. The different solubilization behavior of DPPC/DPPG liposomes compared to the pure liposomes could be due to a specific "extraction" of DPPG into the mixed micelles in the coexistence region.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2005

Concentration, temperature, and salt-induced micellization of a triblock copolymer Pluronic L64 in aqueous media.

The effect of copolymer concentration, temperature, and sodium halides (NaI, NaBr, NaCl, and NaF) on micellization and micellar properties of a poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) amphiphilic copolymer (Pluronic L64: EO13PO30EO13), was examined by different methods such as dye spectral change, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), small angle neutron scattering (SANS), dynamic light scattering (DLS), viscosity, and cloud point (CP). Temperature/polymer concentration/salt dependent aggregation behavior of L64 was observed. The data on critical micelle concentration (CMC), critical micelle temperature (CMT), (CP), micelle size, and shape are reported. The Fourier transform infrared (FTIR) showed temperature dependent changes in C-O-C stretching variation band towards higher wave numbers and broadening of band width during the micellization process; this was attributed to increase in proportion of the anhydrous methyl groups, while the proportion of the hydrated methyl groups was decreased. Differential scanning calorimetry (DSC) provides CMTs and CPs from the same experiment. CMC values derived from dye spectral change, decrease significantly with the addition of salt. The increases in salt/copolymer concentration lower the onset temperature of micellization (CMT). Halide anions influence both CMT and CP in the order of F- > Cl- > Br- > I- when total salt and copolymer concentration kept constant. SANS results show the increase of inter-micellar interaction due to the increase in temperature/salt concentration; this is supported by viscosity data.

Calorimetry, Differential Scanning↗
PubMed2004

Study of condition-dependent decomposition reactions; Part I. The thermal behaviour and decomposition of 2-nitrobenzoyl chloride.

The risks associated with batch processing in the manufacture of chemicals and pharmaceuticals via highly exothermic reactions are of special interest due to the possibility of runaway reactions. o-Nitrated benzoyl chlorides are intermediates in the production of agrochemicals and are produced via the reaction of o-nitrated carboxylic acids with thionyl chloride in a solvent mixture. ortho-Nitrated acyl chlorides have exploded violently on attempted distillation on numerous occasions. An inadequate investigation of the process prior to large-scale operation is the most likely cause. Here we present preliminary results of studies on the decomposition of 2-nitrobenzoyl chloride. This study has revealed that the decomposition reaction is strongly condition dependent. The heating rate of the sample plays a preponderant role in the course of the decomposition reaction. That renders the interpretation of differential scanning calorimetry (DSC) or adiabatic calorimetry measurements, which are routinely used to assess the thermochemistry and safety of the large-scale reactions, problematic. Following this on-going study, we report here key features of the system that have been identified.

Benzoates↗
PubMed2006

Calorimetric studies on the thermal hazard of methyl ethyl ketone peroxide with incompatible substances.

In Taiwan, Japan, and China, methyl ethyl ketone peroxide (MEKPO) has caused many severe thermal explosions owing to its thermal instability and reactivity originating from the complexity of its structure. This study focused on the incompatible features of MEKPO as detected by calorimetry. The thermal decomposition and runaway behaviors of MEKPO with about 10wt.% incompatibilities, such as H(2)SO(4), HCl, NaOH, KOH, FeCl(3), and FeSO(4), were analyzed by dynamic calorimeter, differential scanning calorimetry (DSC) and adiabatic calorimeter, vent sizing package 2 (VSP2). Thermokinetic data, such as onset temperature, heat of decomposition, adiabatic temperature rise, and self-heat rate, were obtained and assessed. Experimental data were used for determining the incompatibility rating on hazards. From the thermal curves of MEKPO with assumed incompatible substances detected by DSC, all the onset temperatures in the other tests occurring earlier advanced, especially with alkaline or ferric materials. In some tests, significant incompatible reactions were found. Adiabatic runaway behaviors for simulating the worst case scenario were performed by using VSP2. These calorimetric data led to the same results that the alkaline or ferric solution was the most incompatible with MEKPO.

Butanones↗
PubMed2005

The salt-dependence of a protein-ligand interaction: ion-protein binding energetics.

Using the binding of a nucleotide inhibitor (guanosine-3'-monophosphate) to a ribonuclease (ribonuclease Sa) as a model system, we show that the salt-dependence of the interaction arises due to specific ion binding at the site of nucleotide binding. The presence of specific ion-protein binding is concluded from a combination of differential scanning calorimetry and NMR data. Isothermal titration calorimetry data are then fit to determine the energetic profile (enthalpy, entropy, and heat capacity) for both the ion-protein and nucleotide-protein interactions. The results provide insight into the energetics of charge-charge interactions, and have implications for the interpretation of an observed salt-dependence. Further, the presence of specific ion-binding leads to a system behavior as a function of temperature that is drastically different from that predicted from Poisson-Boltzmann calculations.

Binding Sites↗
PubMed2006

A thermally induced phase transition in a viral capsid transforms the hexamers, leaving the pentamers unchanged.

Scanning calorimetry combined with cryo-electron microscopy affords a powerful approach to investigating hierarchical interactions in multi-protein complexes. Calorimetry can detect the temperatures at which certain interactions are disrupted and cryo-EM can reveal the accompanying structural changes. The procapsid of bacteriophage HK97 (Prohead I) is a 450A-diameter shell composed of 60 hexamers and 12 pentamers of gp5, organized with icosahedral symmetry. Gp5 consists of the N-terminal Delta-domain (11kDa) and gp5* (31 kDa): gp5* forms the contiguous shell from which clusters of Delta-domains extend inwards. At neutral pH, Prohead I exhibits an endothermic transition at 53 degrees C with an enthalpy change of 14 kcal/mole (of gp5 monomer). We show that this transition is reversible. To capture its structural expression, we incubated Prohead I at 60 degrees C followed by rapid freezing and, by cryo-EM, observed a capsid species 10% larger than Prohead I. At 11A resolution, visible changes are confined to the gp5 hexamers. Their Delta-domain clusters have disappeared and are presumably disordered, either by unfolding or dispersal. The gp5* hexamer rings are thinned and flattened as they assume the conformation observed in Expansion Intermediate I, a transition state of the normal, proteolysis-induced, maturation pathway. We infer that, at ambient temperatures, the hexamer Delta-domains restrain their gp5* rings from switching to a lower free energy, EI-I-like, state; above 53 degrees, this restraint is overcome. Pentamers, on the other hand, are more stably anchored and resist this thermal perturbation.

Bacteriophages↗
PubMed2005

Adequate feeding and the usefulness of the respiratory quotient in critically ill children.

OBJECTIVE: We determined incidences of underfeeding and overfeeding in children who were admitted to a multidisciplinary tertiary pediatric intensive care and evaluated the usefulness of the respiratory quotient (RQ) obtained from indirect calorimetry to assess feeding adequacy. METHODS: Children 18 y and younger who fulfilled the criteria for indirect calorimetry entered our prospective, observational study and were studied until day 14. Actual energy intake was recorded, compared with required energy intake (measured energy expenditure plus 10%), and classified as underfeeding (<90% of required), adequate feeding (90% to 110% of required), or overfeeding (>110% of required). We also evaluated the adequacy of a measured RQ lower than 0.85 to identify underfeeding, and an RQ higher than 1.0 to identify overfeeding. RESULTS: Ninety-eight children underwent 195 calorimetric measurements. Underfeeding, adequate feeding, and overfeeding occurred on 21%, 10%, and 69% of days, respectively. An RQ lower than 0.85 to identify underfeeding showed low sensitivity (63%), high specificity (89%), and high negative predictive value (90%). An RQ higher than 1.0 to indicate overfeeding showed poor sensitivity (21%), but a high specificity (97%) and a high positive predictive value (93%). Food composition, notably high-carbohydrate intake, was responsible for an RQ exceeding 1.0 in the overfed group. CONCLUSION: Children admitted to the intensive care unit receive adequate feeding on only 10% of measurement days during the first 2 wk of admission. The usefulness of RQ to monitor feeding adequacy is limited to identifying (carbohydrate) overfeeding and excluding underfeeding.

Adolescent↗
PubMed2005

Conformational analysis and crystal structure of {[1-(3-chloro-4-fluorobenzoyl)-4-fluoropiperidin-4yl]methyl}[(5-methylpyridin-2-yl)methyl]amine, fumaric acid salt.

{[1-(3-Chloro-4-fluorobenzoyl)-4-fluoropiperidin-4yl]methyl}[(5-methylpyridin-2-yl)methyl]amine, fumaric acid salt (C(20)H(22)ClF(2)N(3)O, C(4)H(4)O(4)) (1) was synthesized and characterized by the complete (1)H, (13)C and (19)F NMR analyses. The conformation of the piperidin ring, in the solution state, was particularly studied from the coupling constants determined by recording a double-quantum filtered COSY experiment in phase-sensitive mode. (1)H NMR line-shape analysis was used, at temperatures varying between -5 and +60 degrees C, to determine the enthalpy of activation of the rotational barrier around the CN bond. Compound 1 crystallizes in the triclinic space group P1 with a=8.517(3) Angstrom, b=12.384(2) Angstrom, c=12.472(3) Angstrom, alpha=70.88(2) degrees, beta=82.04(2) degrees, gamma=83.58(2) degrees. The results strongly indicate that the solid and solution conformations are similar. Thermal stability and phases transitions were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Furthermore polymorphism screening was studied from recrystallization of 1 performed in seven solvents and by slurry conversion in water. The X-ray powder diffraction (XRPD) and differential scanning calorimetry results suggested that 1 crystallizes into one crystalline form which melts at 157 degrees C (DeltaH=132 J g(-1)).

Calorimetry, Differential Scanning↗