Authors:Lee-Ann Briere, Jan-M. Brandt, and John Medley
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.
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
(ΔHapp =ΔHø +nwCp,wT ). Experimental solubility and calorimetric data of a large number of non-polar substances nicely agree with the expected
function. The specific contribution of nw solvent molecules depends on the size of solute and is related to destructuring (nw >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, ΔHden , increasing with T . A portion of reaction enthalpy is absorbed by a number nw of water molecules (nw >0) relaxed in space around the denatured moieties. In micellization, an opposite process takes place with negative number
of restructured water molecules (nw <0) because the hydrophobic moieties of the molecules joined by hydrophobic affinity occupy a smaller cavity.
Authors:Michele Iafisco, Ismaela Foltran, Michele Di Foggia, Sergio Bonora, and Norberto Roveri
valuable information on the overall mechanism of proteindenaturation, 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
Authors:A. Michnik, Z. Drzazga, K. Michalik, A. Barczyk, I. Santura, E. Sozańska, and W. Pierzchała
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.
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 proteindenaturation in the samples treated at 600 MPa caused a small amount of
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.
Authors:K. Török, L. Hajas, V. Horváth, E. Schall, Zs. Bugyi, and S. Tömösközi
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.
Authors:R. Briones-Martínez, M. Juárez-Juárez, M. Oliver-Salvador, and M. Cortés-Vázquez
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.
Authors:Xiaomin Cao, Yun Tian, Zhiyong Wang, Yuwen Liu, and Cunxin Wang
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 (Tm), apparent activation energy (Ea), 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.