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Abstract  

Differential scanning calorimetry (DSC) was used to evaluate the thermal transitions associated with protein constituents of synovial fluid samples from three individuals with osteoarthritis. Analysis of the multi-component DSC curves revealed that major endothermic transitions of synovial fluid occur between 60 and 80 °C and can be resolved into three peaks, likely due to the unfolding of human serum albumin and immunoglobulins, and that the enthalpies of these transitions can be quantified in terms of their relative contribution to the total system enthalpy. DSC was also used to analyze a solution of bovine calf serum, a lubricant used in simulator wear testing of joint replacement implants, and the resulting endothermic transitions occurred in a temperature range relevant to that produced by frictional heat during such wear simulator testing. Results of this study indicate a new application for DSC as a direct method for studying thermal stabilities of both bovine calf serum and synovial fluid. The use of DSC is proposed as a diagnostic tool to detect altered thermal properties or protein concentrations indicative of a diseased or injured state, and as a development tool to test the efficacy of additives in controlling protein denaturation associated with increased wear in joint replacement implants.

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Abstract  

The 'hydrophobic effect' of the dissolution process of non-polar substances in water has been analysed under the light of a statistical thermodynamic molecular model. The model, based on the distinction between non-reacting and reacting systems explains the changes of the thermodynamic functions with temperature in aqueous systems. In the dissolution of non-polar substances in water, it follows from the model that the enthalpy change can be expressed as a linear function of the temperature (ΔH appH ø +n w C p,w T ). Experimental solubility and calorimetric data of a large number of non-polar substances nicely agree with the expected function. The specific contribution of n w solvent molecules depends on the size of solute and is related to destructuring (n w >0) of water molecules around the solute. Then the study of 'hydrophobic effect' has been extended to the protein denaturation and micelle formation. Denaturation enthalpy either obtained by van't Hoff equation or by calorimetric determinations again depends linearly upon denaturation temperature, with denaturation enthalpy, ΔH den , increasing with T . A portion of reaction enthalpy is absorbed by a number n w of water molecules (n w >0) relaxed in space around the denatured moieties. In micellization, an opposite process takes place with negative number of restructured water molecules (n w <0) because the hydrophobic moieties of the molecules joined by hydrophobic affinity occupy a smaller cavity.

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Journal of Thermal Analysis and Calorimetry
Authors: Michele Iafisco, Ismaela Foltran, Michele Di Foggia, Sergio Bonora, and Norberto Roveri

valuable information on the overall mechanism of protein denaturation, on its reversibility as well as on its cooperativity by studying temperature and enthalpy changes associated to the thermal transitions. Figure 1a and b shows the

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Abstract  

Differential scanning calorimetry (DSC) has been applied for studies of blood serum from patients sick with chronic obstructive pulmonary disease (COPD). The denaturation of serum proceeds as endothermic process over the temperature range 45–85 °C. Distinct changes in the shape of DSC curves have been observed for serum from patients with severe stage of COPD (treated with inhaled corticosteroids) relative to serum from healthy individuals. The first moment of the thermal transition with respect to the temperature axis shifts from the normal value of 63.9 ± 0.3 to 65.3 ± 0.7 °C and to 67.6 ± 1.6 °C for early and advanced stages of disease, respectively. The results of our studies suggest age dependence of blood serum denaturation transition.

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Acta Alimentaria
Authors: B. Csehi, B. Salamon, T. Csurka, E. Szerdahelyi, L. Friedrich, and K. Pásztor-Huszár

in the order of magnitude of the values. The proteins coagulate due to high hydrostatic pressure treatment, causing to the blood to flow more densely. Presumably the protein denaturation in the samples treated at 600 MPa caused a small amount of

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Abstract  

Differential scanning calorimetry (DSC) has been employed to study the thermal denaturation processes of the main protein fractions of blood serum. These processes have been compared for albumins (nondefatted (HSA) and fatty acid free (HSAf)), α,β-globulins, γ-globulins, and their mixtures in aqueous (pH 6.5) and buffer (pH 7.2) solutions. The results have indicated that α,β-globulins inhibit γ-globulins’ aggregation in buffer solutions. The decrease of stability of HSA and HSAf aqueous solutions has been observed in the presence of γ-globulins. The mixtures of albumins and γ-globulins have revealed the tendency to ready aggregation in water. Moreover, the results have suggested that neither γ-globulins nor albumins severely change the stability of α,β-globulins.

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The weaker performance of generally used analytical methods for allergen analysis in processed foods can be connected to protein denaturation. To understand the nature of protein denaturation processes, experimental but realistic model matrices (corn starch based mixture, hydrated dough, and heat treated cookies) were developed that contain a defined amount of milk, egg, soy, and wheat proteins individually or in combination. The protein subunit composition was investigated in every processing phase, i.e. after mixing, dough formation, and baking. SDS-PAGE measurements were carried out to monitor the protein distribution of sample food matrices in non-reducing and reducing gels. The results clearly show that the highly decreased protein solubility is caused by denaturation, aggregation, or complex formation, which are the most significant factors in poorer analytical performances. Solubility can only partly be improved with the application of reducing agents or surfactants, and the rate of improvement is depending on the proteins and the matrices.

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Journal of Thermal Analysis and Calorimetry
Authors: R. Briones-Martínez, M. Juárez-Juárez, M. Oliver-Salvador, and M. Cortés-Vázquez

Abstract  

DSC was used to study the extent of denaturation of hemisphaericin and mexicain hydrolysates from corn gluten, soybean and sunflower meals. It was observed that the defatted meals studied exhibited only one broad peak transition. The data obtained demonstrated that the partial protein denaturation found with hemisphaericin or mexicain is correlated to modifications of functional properties. The two enzymes display different modes of action, according to the protein source.

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Abstract  

The kinetics of bovine serum albumin (BSA) denaturation in the absence and the presence of urea was studied by the iso-conversional method and the master plots method using differential scanning calorimetry (DSC). The observed denaturation process was irreversible and approximately conformed to the simple order reaction, and the denaturation did not follow rigorously first-order kinetic model or other integral order reaction models. The denaturation temperature (T m), apparent activation energy (E a), approximate order of reaction (n), and pre-exponential factor (A) all distinctly decreased as the 2 mol L−1 urea was added, which indicated that the urea accelerated the denaturation process of BSA and greatly reduced thermal and kinetic stability of BSA. This study also demonstrated that the iso-conversional method, in combination with the master plots method, provides a valuable and useful approach to the study of the kinetic process of protein denaturation.

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