Differential Scanning Calorimetry Profiles Research Articles

COMPOSITION, PHYSICOCHEMICAL AND RHEOLOGICAL PROPERTIES OF FRESH BIGEYE SNAPPER FISH (PRIACANTHUS HAMRUR) MINCE

ABSTRACT Composition and properties of fresh bigeye snapper fish (Priacanthus hamrur) mince has been investigated. The protein content of fish mince was 16.71 g/100 g mince. Amino acid analysis revealed high proportion of glutamic acid, alanine, lysine and leucine. Fatty acid profile indicated high proportion of eicosa pentaenoic acid and decosa hexaenoic acid content. Gel filtration profile of total proteins from fresh bigeye fish mince revealed a major peak (high molecular weight component) and a few minor peaks, which was further confirmed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis pattern. The differential scanning calorimetry profile of fresh bigeye fish mince revealed transitions at 38.35, 47.72 and 63.02C indicating denaturation temperature of different protein fractions. The gel-forming ability of fresh bigeye fish mince was evaluated by both small strain and large strain tests. The flow behavior of total protein solution from fresh bigeye fish mince as a function of protein concentration and temperature showed pseudoplastic behavior. PRACTICAL APPLICATIONS The properties of fish mince including amino acid and fatty acid profile are critical in deciding the nature of processed products to be prepared. Because of lower catch of bigeye snapper in formerly, this fish was not commonly available and hence, it has been regarded as a nonconventional marine fishery resource. Recently, bigeye snapper has assumed significance as an important species in the commercial landings. In the present investigation, composition, thermal and rheological properties of fresh bigeye snapper mince have been assessed. A high proportion of omega 3 fatty acids shows the nutritional importance of this fish whereas its gel-forming ability shows the potential to be utilized as raw material in the surimi industry. Establishing the thermal denaturation profile, measurement of dynamic viscoelstic behavior and assessing the flow behavior of proteins from bigeye snapper will aid in the appropriate processing and design in formulating mince-based products.

Selection and Characterization of Suitable Lipid Excipients for use in the Manufacture of Didanosine-Loaded Solid Lipid Nanoparticles and Nanostructured Lipid Carriers

This research aimed to evaluate the suitability of lipids for the manufacture of solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) loaded with the hydrophilic drug, didanosine (DDI). The crystalline state and polymorphism of lipids with the best-solubulizing potential for DDI was investigated using differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS). DSC and WAXS were also used to determine potential interactions between the bulk lipids and DDI. Precirol® ATO 5 and Transcutol® HP showed the best-solubilizing potential for DDI. Precirol® ATO 5 exists in the β-modification before heating; however, a mixture of both α- and β-modifications were detected following heating. Addition of Transcutol® HP to Precirol® ATO 5 changes the polymorphism of the latter from the β-modification to a form that exhibits coexistence of the α- and β-modifications. DDI exists in a crystalline state when dispersed at 5% (w/w) in Precirol® ATO 5 or in a Precirol® ATO 5/Transcutol® HP mixture. DSC and WAXS profiles of DDI/bulk lipids mixture obtained before and after exposure to heat revealed no interactions between DDI and the lipids. Precirol® ATO 5 and a mixture of Precirol® ATO 5 and Transcutol® HP may be used to manufacture DDI-loaded SLN and NLC, respectively.

Microcalorimetry of Blood Serum Proteome: A Modified Interaction Network in the Multiple Myeloma Case

Hereby we report on a novel approach in the study of multiple myeloma (MM), namely, differential scanning calorimetry (DSC) combined with serum protein electrophoresis. Distinct thermodynamic signatures describe the DSC thermograms of MM blood sera, in contrast to the unique profile found for healthy individuals. The thermal behavior of MM sera reflects a complex interplay between the serum concentration and isotype of the M protein and of albumin, and modified ligand- and/or protein-protein interactions, resulting in stabilization of globulins and at least a fraction of albumin. In all MM cases the 85 °C, transferrin-assigned transition is missing. A distinct feature of IgG isotype (κ and λ) DSC profiles only is the presence of a transition at 82 °C. A DSC-based classification of MM depicts two sets of melting patterns (MMt2 and MMt3 with two or three successive thermal transitions), and subsets within each set (MMt2(i) or MMt3(i), the subscript i = 1, 2 or 3 denotes the main transition being one of the three transitions). The results demonstrate the potential of DSC to monitor MM-related modifications of the serum proteome, even at low M protein concentrations, Bence Jones and importantly nonsecretory multiple myeloma cases, and prove DSC as a versatile tool for oncohematology.

Microstructural characterization and amorphous phase formation in Co40Fe22Ta8B30 powders produced by mechanical alloying

In this work, microstructural evolution and amorphous phase formation in Co40Fe22Ta8B30 alloy produced by mechanical alloying (MA) of the elemental powder mixture under argon gas atmosphere was investigated. Milling time had a profound effect on the phase transformation, microstructure, morphological evolution and thermal behavior of the powders. These effects were studied by the X-ray powder diffraction (XRD) in reflection mode using Cu Kα and in transmission configuration using synchrotron radiation, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The results showed that at the early stage of the milling, microstructure consisted of nanocrystalline bcc-(Fe, Co) phases and unreacted tantalum.Further milling, produced an amorphous phase, which became a dominant phase with a fraction of 96wt% after 200h milling. The DSC profile of 200h milled powders demonstrated a huge and broad exothermic hump due to the structural relaxation, followed by a single exothermic peak, indicating the crystallization of the amorphous phase. Further XRD studies in transmission mode by synchrotron radiation revealed that the crystalline products were (Co, Fe)20.82Ta2.18B6, (Co, Fe)21 Ta2 B6, and (Co, Fe)3B2. The amorphization mechanisms were discussed in terms of severe grain refinement, atomic size effect, the concept of local topological instability and the heat of mixing of the reactants.

Phase Transitions and Spatially Ordered Counterion Association in Ionic-Lipid Membranes: Theory versus Experiment

Aqueous dispersions of phosphatidylglycerol (PG) lipids may present an anomalous chain-melting transition at low ionic strengths, as seen by different experimental techniques such as calorimetry or light scattering. The anomaly disappears at high ionic strengths or for longer acyl-chain lengths. In this article, we use a statistical model for the bilayer that distinguishes both lipid chain and headgroup states in order to compare model and experimental thermotropic and electrical properties. The effective van der Waals interactions among hydrophobic chains compete with the electrostatic repulsions between polar headgroups, which may be ionized (counterion dissociated) or electrically neutral (associated with counterions). Electric degrees of freedom introduce new thermotropic charge-ordered phases in which headgroup charges may be spatially ordered, depending on the electrolyte ionic strength, introducing a new rationale for experimental data on PGs. The thermal phases presented by the model for different chain lengths, at fixed ionic strength, compare well with an experimental phase diagram constructed on the basis of differential scanning calorimetry profiles. In the case of dispersions of DMPG (dimyristoyl phosphatidylglycerol) with added monovalent salt, the model properties reproduce the main features displayed by data from differential scanning calorimetry as well as the characteristic profile for the degree of ionization of the bilayer surface across the anomalous transition region, obtained from the theoretical interpretation of electrokinetic (conductivity and electrophoretic mobility) measurements.

Gelation process in two different squid (Dosidicus gigas) surimis throughout frozen storage as affected by several cryoprotectants: Thermal, mechanical and dynamic rheological properties

Differential scanning calorimetry (DSC) was used to follow the thermal denaturation of two differently processed surimis from giant squid (Dosidicus gigas), A (isoelectric precipitation) and B (acid washing). Both surimis were added with several cryoprotectants (sucrose, sorbitol and trehalose), and kept in frozen storage at −15°C for 6months. DSC profiles and transition enthalpies showed that protein quality was better in B than in A surimis whether fresh or frozen. It was also demonstrated that the sucrose-plus-sorbitol mixture and trehalose were the most efficient for preserving B and A type formulations respectively after frozen storage. Mechanical (puncture), small amplitude oscillatory (SAOS) and dynamic-mechanical thermoanalyses were performed on both gels from A and B series surimis throughout frozen storage. Gels from surimi A (GA) were considerably brittler than gels from surimi B (GB) and presented significantly lower strain amplitudes. Several correlations among different experimental data have been developed.

Unfolding and Targeting Thermodynamics of DNA Hairpins Containing Internal Loops

In this work, we use a set of DNA hairpins as a model to mimic a common motif present in the secondary structures of mRNA, i.e., a stem-loop motif with an internal loop in the stem. Specifically, we used a combination of UV and differential scanning calorimetry (DSC) melting techniques to determine thermodynamic profiles for the unfolding of a set of hairpins with sequence: d(GCGCTnGTAACT5GTTACTnGCGC, where n = 1, 3 or 5,“T5” is an end loop of five thymines. UV melting curves of each hairpin show monophasic transitions with TMs that are independent of strand concentration, confirming their intramolecular formation. Analysis of the DSC profiles indicates that the unfolding of each hairpin results from the typical compensation of a unfavorable enthalpy (breaking of base-pair stacks) and favorable entropy contributions (release of ions and water molecules). The increase in the size of the internal loop from 2 to 10 thymines yielded: a) lower TMs and lower enthalpy contributions, corresponding to free energy contributions of ∼0.7 kcal/mol of thymine; b) lower heat capacity effects that correlated with the lower releases of structural water molecules; and c) higher releases of ions. Furthermore, we used isothermal titration calorimetry to investigate the thermodynamics for the reaction of each hairpin with their partially complementary strands. The overall results showed that all three targeting reactions yielded favorable free energy contributions and were enthalpy driven. This approach works because of the favorable heat contributions resulting from the formation of base-pair stacks involving the unpaired bases of the loops. Supported by Grant MCB-0315746 from the National Science Foundation.

Usefulness of Differential Scanning Calorimetry for Monitoring Ex Vivo the Changes In Responses of CLL Cells to Anti-Cancer Drugs: Development of Personalized Therapy

AbstractAbstract 4635 Objective:Chronic lymphocytic leukemia (CLL) is the most frequent type of leukemia among elderly people in Europe and North America. CLL is considered as a cancer involving mainly deregulated apoptosis. A strong difference between patients in the disease progression, response to anti-cancer therapy, and outcome is a major challenge in elaboration of efficacious treatment. Therefore, it is important to develop personalized therapeutic protocols based on the individual patient's sensitivity to medication. The aim of our ex vivo studies was to monitor the changes in responses of leukemic cells to anti-cancer agent(s) and correlate results obtained by DSC and other supplementary techniques with patients clinical response. Methods:Leukemic cells were obtained from peripheral blood of 14 patients prior to the onset of CC (cladribine + cyclophosphamide) therapy. Primary tumour cell samples were exposed ex vivo to CM or FM, as well as to ROSC alone for 48 hrs. We monitored the induction and progress of apoptosis in CLL cells exposed ex vivo to purine analogs combined with mafosfamide i.e. CM (cladribine + mafosfamide), FM (fludarabine + mafosfamide), and additionally to R-roscovitine (ROSC), an inhibitor of cyclin-dependent kinases, by a few techniques, i.e. cell viability test, apoptosis assay, differential scanning calorimetry (DSC), immunoblotting and determination of caspase-3/7 activity in the culture medium. The characteristic changes in chromatin complex induced upon the above treatments were detected by DSC, a simple thermal technique. This study received approval of the Medical University of Lodz Ethical Committee (RNN/196/07/KE). Informed consent was obtained from all the patients. Results:Marked differences in the individual patients' sensitivity to the agents used were registered. A decrease or even loss of transition at 95±5°C in thermal scans of nuclear fraction preparations occurred in the treated cells in which apoptosis was induced. Remarkably, the changes in thermal profiles coincided with an accumulation of apoptotic cells, a decrease of the number of viable cells, and the changes in cellular levels as well as functional status of apoptosis-related proteins (caspase-9, Mcl-1) and CLL prognostic factor – kinase Zap-70. However, no significant changes were observed in thermal profiles of nuclei originating from CLL cells resistant to the treatment. Our studies revealed that the ex vivo exposure of CLL cells to CM combination, equivalent to clinically used CC regimen, was of prognostic value. Among the DSC profiles of nuclear preparations isolated from leukemic cells treated ex vivo with CM 70% of the cases examined indicated the decrease or loss of transition at about 95 ± 5°C. Moreover, we noticed a statistically significant dependence between the patient's response to CC treatment and thermal transition reduction at 95 ± 5°C (p=0.034). Interestingly, the results of the examined group did not show any correlation between disease advance (Rai stage) or cytogenetic abnormalities versus the clinical patient's response to the used treatment. Conclusion:Our results demonstrate the advantage of DSC in the evaluation of the treatment efficacy and indicate that its application could facilitate the choice of highly effective therapy for individual patients. Disclosures:No relevant conflicts of interest to declare.

Mechanism of aggregation of UV-irradiated βL-crystallin

Thermal denaturation and aggregation of UV-irradiated βL-crystallin from eye lenses of steers have been studied. The data on size-exclusion chromatography and SDS-PAGE indicated that UV irradiation of βL-crystallin at 10 °С resulted in fragmentation of the protein molecule and formation of cross-linked aggregates. Fluorescence data showed that tryptophan fluorescence in the irradiated protein decreased exponentially with the UV dose. Decrease in tryptophan fluorescence is a result of photochemical destruction, but not of conformational changes of protein, because there is no red shift in the fluorescence maximum. The differential scanning calorimetry (DSC) profiles of the samples of UV-irradiated and wild type βL-crystallin were registered. The area under curves, which is proportional to the amount of the native protein, decreased exponentially with increasing the irradiation dose. The shape of the DSC profiles for the samples of UV-irradiated βL-crystallin was identical to that for wild type βL-crystallin. The DSC data allowed estimating the portion of UV-denatured βL-crystallin, which is not registered by DSC, and the portion of the combined fraction consisting of native and UV-damaged molecules retaining the native structure. A conclusion has been made that UV-induced denaturation of βL-crystallin follows the one-hit model. The study of the kinetics of thermal aggregation of UV-irradiated βL-crystallin at 37 °С using dynamic light scattering showed that the initial stage of aggregation was that of formation of the start aggregates with the hydrodynamic radius of 20 nm. Further sticking of the start aggregates proceeded in the regime of reaction-limited cluster–cluster aggregation. Splitting of the aggregate population into two components occurred above a definite point in time.

Thermal Denaturation and Aggregation of Myosin Subfragment 1 Isoforms with Different Essential Light Chains

We compared thermally induced denaturation and aggregation of two isoforms of the isolated myosin head (myosin subfragment 1, S1) containing different “essential” (or “alkali”) light chains, A1 or A2. We applied differential scanning calorimetry (DSC) to investigate the domain structure of these two S1 isoforms. For this purpose, a special calorimetric approach was developed to analyze the DSC profiles of irreversibly denaturing multidomain proteins. Using this approach, we revealed two calorimetric domains in the S1 molecule, the more thermostable domain denaturing in two steps. Comparing the DSC data with temperature dependences of intrinsic fluorescence parameters and S1 ATPase inactivation, we have identified these two calorimetric domains as motor domain and regulatory domain of the myosin head, the motor domain being more thermostable. Some difference between the two S1 isoforms was only revealed by DSC in thermal denaturation of the regulatory domain. We also applied dynamic light scattering (DLS) to analyze the aggregation of S1 isoforms induced by their thermal denaturation. We have found no appreciable difference between these S1 isoforms in their aggregation properties under ionic strength conditions close to those in the muscle fiber (in the presence of 100 mM KCl). Under these conditions kinetics of this process was independent of protein concentration, and the aggregation rate was limited by irreversible denaturation of the S1 motor domain.

Thermal and optical properties of tellurite glasses doped erbium

Er3+-doped tellurite glasses with molar compositions of 75TeO2–20ZnO–(5 − x) Na2O–xEr2O3 (x = 0, 0.5, 1, 2, 3, and 4 mol%) have been elaborated from the melt-quenching method. The effects of Er2O3 concentration on the thermal stability and optical properties of tellurite glasses have been discussed. From the differential scanning calorimetry (DSC) profile, the glass transition temperature T g, and crystallization onset temperature T x are estimated. The thermal stability factor, defined as ∆T = T x − T g, was higher than 100 °C. It suggests that tellurite glass exhibits a good thermal stability and consequently is suitable to be a potential candidate for fiber drawing. Furthermore, the stability factor increases with Er2O3 concentration up to 2 mol% then presents a continue decrease suggesting of beginning of crystallization of highly doped tellurite glasses. The refractive index and extinction coefficient data were obtained by analyzing the experimental spectra of tanΨ and cos∆ measured by spectroscopic ellipsometry (SE). The complex dielectric functions (e = e1 + ie2) of the samples were estimated from regression analysis. The fundamental absorption edge has been identified from the optical absorption spectra and was analyzed in terms of the theory proposed by Davis and Mott. The values of optical band gap for direct and indirect allowed transitions have been determined. An important decrease of the optical band gap was found after Er doping. It was assigned to structural changes induced from the formation of non-bridging oxygen. The absorption coefficient just below the absorption edge varies exponentially with photon energy indicating the presence of Urbach’s tail. The origin of the Urbach energy is associated with the phonon-assisted indirect transitions.

Photoluminescence of Dy 3+ and Sm 3+: SiO 2–Al 2O 3–LiF–CaF 2 glasses

In this paper, we present the absorption and photoluminescence properties of Dy 3+ and Sm 3+ (1.0 mol%) ions doped SiO 2–Al 2O 3–LiF–CaF 2 glasses. The X-ray diffraction (XRD) and differential scanning calorimetry (DSC) profiles of these rare-earth ions doped glasses have been carried out, to confirm their structure and thermal stability. From the DSC thermograms, glass transition temperature ( T g), crystallization temperatures ( T c1 and T c2) and melting temperature ( T m) have been evaluated. These glasses have shown strong emission and absorption bands in ultraviolet and visible region. For Dy 3+ doped glass, a bright fluorescent blue emission at 482 nm ( 4F 9/2→ 6H 15/2) and yellow emission at 574 nm ( 4F 9/2→ 6H 13/2) have been observed, apart from ( 4I 13/2, 4F 7/2)→ 6H 13/2 (454 nm) and 4F 9/2→ 6H 11/2 (662 nm) two comparative weak emission transitions with 348 nm ( 6H 15/2→ 4M 15/2+ 6P 7/2) excitation wavelength. With regard to Sm 3+: glass, emission bands of 4G 5/2→ 6H 5/2 (563 nm), 4G 5/2→ 6H 7/2 (599 nm) and 4G 5/2→ 6H 9/2 (647 nm) have been recorded with an excitation at 6H 5/2→ 4F 7/2 (401 nm). Of them, 4G 5/2→ 6H 7/2 (599 nm) has shown a bright orange emission. Upon exposure to UV radiation, Dy 3+ and Sm 3+ glasses have shown bright blue–yellow and orange colors, respectively, from their surfaces.

Energetic domains analysis of bovine α-lactalbumin upon interaction with copper and dodecyl trimethylammonium bromide

Domain analysis of the dialyzed form of α-lactalbumin (m-α-LA) with varying concentrations of Cu +2 and DTAB has been carried out by differential scanning calorimetry (DSC), circular dichroism (CD) and resonance Rayleigh scattering (RLS) to elucidate the effect of the ligands on the thermal and structural properties of m-α-LA. The DSC profile displayed two dissimilar temperature-induced heat-absorption peaks as well as two melting points ( T m = 305 K, T m = 333 K). The m-α-LA is not a new form of α-LA, but rather contains a mixture of the apo- and holo-forms of α-LA (i.e., a-α-LA and h-α-LA) at low and high temperatures, respectively. The presence of Cu +2 as the metal ion and DTAB as the non-metal ion altered the two heat-absorption peaks in such a manner that, with the addition of Cu +2 to m-α-LA, the excess molar heat capacity profile showed three sub-peaks, i.e., one sub-peak for a-α-LA at 303.2 K and two other sub-peaks for h-α-LA at 325 K and 334 K. The presence of these peaks was due to the molecular population of the a-α-LA form changing into h-α-LA. Contrarily, when it came to the interaction between DTAB and m-α-LA, the DSC thermogram showed two sub-peaks, i.e., one sub-peak for a-α-LA and another sub-peak for h-α-LA, resulting from the molecular population of the h-α-LA form changing into a-α-LA. The CD experiments on m-α-LA upon interaction with Cu +2 and DTAB demonstrated an increment and a decrement, respectively, of the α-helix content relative to that of the protein in the absence of the ligands. However, the α-helix induced by Cu +2 as a metal ion inspired one energetics domain in m-α-LA, wherefore it could be deduced that the helicity content caused an increment of the energetics content of α-LA. Hence, Cu +2 and DTAB at various concentrations played important roles as good probes for defining the electrostatic moiety for domains of m-α-LA initiated through a dissimilarity with regard to the α-helicity of these domains. The RLS intensity of m-α-LA upon interaction with Cu +2 and DTAB determine the DSC and CD results for inducing h-α-LA and a-α-LA respectively.

Phase transitions in Sr 1 + xCo 0.8Fe 0.2O 3 − δ oxides

The phase transitions that take place in Sr 1 + x Co 0.8Fe 0.2O 3 − δ (− 0.2 ≤ x ≤ 0.1) oxides are reported here. Thermogravimetric analysis (TGA) showed that the oxides with − 0.2 ≤ x ≤ 0 were prone to undergo oxygen-vacancy disorder–order phase transitions, while others with x = 0.05, 0.1 had more stable crystal structures during oxygen-desorption processes in nitrogen. These results were further confirmed by high-temperature in-situ X-ray techniques. The changes in activation energies of three typical oxides, Sr 1 + x Co 0.8Fe 0.2O 3 − δ ( x = − 0.2, 0, 0.1), used as oxygen-permeable membranes were investigated. The phase transitions in Sr 1 + x Co 0.8Fe 0.2O 3 − δ ( x = − 0.2, 0) have also been detected in differential scanning calorimetry (DSC) profiles.

Analyzing Protein Folding Cooperativity by Differential Scanning Calorimetry and NMR Spectroscopy

Some marginally stable proteins undergo microsecond time scale folding reactions that involve significant populations of partly ordered forms, making it difficult to discern individual steps in their folding pathways. It has been suggested that many of these proteins fold non-cooperatively, with no significant barriers to separate the energy landscape into distinct thermodynamic states. Here we present an approach for studying the cooperativity of rapid protein folding with a combination of differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) relaxation dispersion experiments, and an analysis of the temperature dependence of amide (1)H and (15)N chemical shifts. We applied this method to the PBX homeodomain (PBX-HD), which folds on the microsecond time scale and produces a broad DSC thermogram with an elevated and steeply sloping native-state heat capacity baseline, making it a candidate for barrierless folding. However, by globally fitting the NMR thermal melt and DSC data, and by comparing these results to those obtained from the NMR relaxation dispersion experiments, we show that the native form of the protein undergoes two-state exchange with a small population of the thermally denatured form, well below the melting temperature. This result directly demonstrates the coexistence of distinct folded and unfolded forms and firmly establishes that folding of PBX-HD is cooperative. Further, we see evidence of large-scale structural and dynamical changes within the native state by NMR, which helps to explain the broad and shallow DSC profile. This study illustrates the potential of combining calorimetry with NMR dynamics experiments to dissect mechanisms of protein folding.

Radiation-induced graft polymerization of styrene into a poly(ether ether ketone) film for preparation of polymer electrolyte membranes

Radiation-induced graft polymerization of styrene into crystalline poly(ether ether ketone) (PEEK) with 32% crystallinity, an aromatic hydrocarbon polymer and so-called “super-engineering plastics”, which has excellent mechanical properties at elevated temperature as well as excellent gas barrier properties, was investigated with differential scanning calorimetry (DSC), thermogravimetry (TGA), X-rays diffraction analysis (XRD), and electron spin resonance spectroscopy (ESR). The endothermic heats of melting of the original and styrene-grafted PEEK (grafted PEEK) films were similar, indicating that the crystallinity was almost completely maintained during the graft polymerization of styrene up to a grafting degree of 51%. Lower glass transition temperature ( T g) of the grafted PEEK film in the DSC profile, and the absence of an extra halo originating from amorphous polystyrene grafts in the XRD strongly indicate that the grafting of styrene to crystalline PEEK films proceeded in the amorphous region of PEEK. This is probably because polystyrene grafts have hydrocarbon structures similar to a base PEEK polymer, resulting in compatibility to the amorphous phase of the PEEK films. The grafted PEEK films can be converted to PEEK-based electrolyte membranes (PEEK-based PEM) by subsequent sulfonation of the polystyrene grafts. The PEEK-based PEM had conductivity of more than 0.01 S/cm and exhibited higher water content above 100%.

Estimation Method for Liquidus Temperature of Lead-Free Solder Using Differential Scanning Calorimetry Profiles

It is usually complicated to analyze the liquidus temperature of lead-free solder, because unlike Sn-Pb eutectic solder, supercooling easily occurs during the cooling process of lead-free solder, and common lead-free solders contain only a small fraction of a primary phase. In order to determine the melting temperature range of lead-free solder easily, an estimation method using differential scanning calorimetry (DSC) profiles is proposed. The purpose of this study is to show the applicability of the newly proposed DSC-based approach. DSC profiles using several heating rates were measured and analyzed. As a result, it was found that the extrapolated onset temperature, the peak temperature, and the extrapolated end temperature of the endothermic peak were proportional to the square root of the DSC heating rate. For lower heating rate, the temperature–axis intercept of the relationship between the square root of the heating rate and the peak temperature can be regarded as the liquidus temperature under equilibrium conditions with better accuracy. For higher heating rate, the temperature–axis intercept of the relationship between the square root of the heating rate and the extrapolated end temperature can be approximately estimated as the liquidus temperature of noneutectic lead-free solder under equilibrium conditions.

Improvement of aqueous solubility of fenretinide and other hydrophobic anti-tumor drugs by complexation with amphiphilic dextrins

This study relates to the preparation of a series of amphiphilic dextrins and their evaluation as complexing agents for anti-tumor hydrophobic drugs such as fenretinide, paclitaxel, etoposide, and camptothecin. The amphiphilic dextrins were obtained by conjugation of low molecular weight dextrin (average molecular weight 1670, average polymerization degree 9.33 glucose monomer) with hydrocarbon chains at substitution degree of about 0.1 mole hydrocarbon chain per mole of glucose monomer, as confirmed by 1H-NMR spectra. The conjugates were highly soluble in water and dissolved with formation of nano-aggregates endowed with hydrophobic inner cores able to host hydrophobic drugs by complexation. Complexation raised hydrophobic drugs aqueous solubility; the best results were obtained with fenretinide. Solid complexes with fenretinide were prepared by using three differents approaches: the kneading method, the co-solubilisation method, and the co-precipitation method. Kneading method provided the complexes endowed with the best functional properties. Thermogravimetric analysis on solid samples suggested a notable thermal stability up to 300°C for both the conjugated dextrins and the solid complexes. In differential scanning calorimetry profiles no significant differences were observed among amphiphilic dextrins and complexed drug, indicating that the guest molecule exists in an amorphous state in the solid matrices. Particle size analysis confirmed the dimensional suitability of the complexes for parenteral administration. Moreover, sustained drug release, in vitro, has been observed from all the complexes analyzed. Regarding the biological effects, the cytotoxicity of complexed fenretinide towards HTLA-230 neuroblastoma cell line was always higher than the free drug, suggesting that complexation increased drug bioavailability. These findings, taken together, indicated that these biodegradable, self-assembling dextrin conjugates may be regarded as new potential complexing agents for hydrophobic drugs and, in particular, for fenretinide, to increase drug solubility, bioavailability, and thus therapeutic efficacy.

Structural, thermal and conductive properties of Bi 4−xM xV 2O 11 (M = La, Gd; 0 ⩽ x ⩽ 0.4) compounds

Bi 4− x M x V 2O 11 (M = La, Gd) was prepared by solid state reactions. The amount of La and Gd in the (Bi 4− x M x V 2O 11) was varied in the range of (0 ⩽ x ⩽ 0.4). The addition of La and Gd to Bi 4V 2O 11 electrolyte was found to stabilize the β crystalline phase for x ⩽ 0.3. In addition, the phase transition corresponding β- to γ-phases are evident in the ionic conductivity plots as well as in XRD, DSC profiles of x ⩾ 0.3 samples. The highest ionic conductivity was observed in Bi 3.9La 0.1V 2O 11 and Bi 3.8Gd 0.2V 2O 11 samples in the range of 10 −3–10 −4 S/cm for 700–500 °C. These results were supported by impedance spectroscopy, X-ray diffraction (XRD) and differential scanning calorimetry (DSC).

Calorimetric study of milk fat/rapeseed oil blends and their interesterification products

AbstractMilk fat (MF) and rapeseed oil (RO) blends were analyzed by differential scanning calorimetry (DSC). It was shown that peak and onset temperatures can be used to determine the percentage of each fat in the blend and that the relative enthalpy of one peak assigned to low‐melting triacylglycerols (TAG) can also be used to determine the percentage of RO in the blend. A linear relation was also established between MF content of the blend and its dropping point (DP), indicating that DP can be linearly related with the above DSC data. A blend of MF/RO 70 : 30 (wt/wt) was then chosen as a model system for enzymatic interesterification (EIE). The applicability of DSC analyses to EIE products was checked and a correct correlation could be established between DSC values and the interesterification degree and DP. Among the data from the DSC profiles, the peak associated with low‐melting TAG was the best indicator of the reaction course. In the same way, a high‐melting MF stearin fraction was interesterified with RO. In that case, onset temperatures and peak “a” were better reaction indicators than for the interesterified MF/RO blend. We therefore suggest that values from DSC endotherms could be used to monitor EIE of fat blends.