Human serum albumin unfolding in ethanol/water mixtures was studied
by use of differential scanning calorimetry. Ethanol-induced changes in DSC
curves of defatted and non-defatted albumin were markedly different. In the
presence of ethanol, bimodal denaturation transition for fatty acid free albumin
was observed while that for albumin containing endogenous fatty acids was
single and more sharpen than in aqueous solution. Ethanol was found to decrease
the thermal stability of albumin due to the binding to the unfolded state
to a higher degree than to the native state, thus favouring unfolding. The
binding with different affinities has been suggested depending on ethanol
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.
The effect of ethanol on human serum albumin stability in aqueous solution
was studied by use of differential scanning calorimetry. A deconvolution of
DSC traces in 2-state model with ΔCp=0
was performed and analysed to obtain information on the interaction of ethanol
with different parts of albumin molecule both fatty acid containing and fatty
acid free. The differences in ethanol binding affinity for both kinds of albumin
were found. At very low concentrations ethanol was observed to be a stabilizer
of the folded state of albumin contrary to the higher concentration where
its binding to the unfolded protein predominates.
Authors:Katarzyna Michalik, Zofia Drzazga, and Anna Michnik
A study of 2′,3′-dideoxyinosine (ddI) stability and its interaction with human serum albumin (HSA) was carried out by differential
scanning microcalorimetry DSC. Scan rate dependent and irreversible endothermic thermal degradation of ddI was analyzed with
use of kinetic approach. Observed process could be interpreted in terms of simple first-order one step kinetic model. Moreover
it was shown that ddI bound weakly to the human serum albumin and stabilized this protein.
Authors:Anna Michnik, Aleksandra Kłos, and Zofia Drzazga
Protein unfolding events were studied by differential scanning calorimetry (DSC) for bovine serum albumin (BSA) aqueous solutions
exposed to radio-frequency radiation. No immediate effect of this radiation on thermal unfolding of BSA was observed. The
differences between irradiated and control samples have appeared during the storage of BSA solution. The irradiated samples
changed faster than non-irradiated. Our results indicated that the age-related changes were stronger for 3.5 and 5 MHz than
for 247 MHz frequency and dependent on energy power of radiation. Deconvolution of DSC traces allowed to study the effect
of radio-frequency radiation on each component transition.
Authors:Anna Michnik, Katarzyna Michalik, and Zofia Drzazga
Summary The effect of pH on the thermal denaturation of BSA containing fatty acids was studied by use of differential scanning calorimetry (DSC). Thermal scanning of BSA aqueous solutions gave various types of DSC curves depending on the protein concentration and on the pH. The broad bimodal endothermic transition was suggested to be connected with loose protein structure in contradistinction to single peak for compact molecule structure. The propensity toward precipitation at pH conditions ranging from 3.8 to 5 was observed. A scan-rate independent and partly reversible behavior of the thermal heating of BSA was found. Deconvolution of DSC traces in non-two-state model with assumption of two- or three-component transition allowed to study the effect of pH on different parts of BSA molecule.
Authors:Katarzyna Michalik, Zofia Drzazga, Anna Michnik, and M. Kaszuba
and kinetic analysis of two protease inhibitors: nelfinavir mesylate and atazanavir
sulfate, were carried out to find their thermal stability. DSC curves of both
drugs showed exothermic transition. This observed process resulted in two
steps. Obtained apparent activation energy pointed at low stability of studied
protease inhibitors in water solutions.
Authors:Zofia Drzazga, Katarzyna Michalik, Tomasz Halat, Anna Michnik, and Henryk Trzeciak
Differential scanning microcalorimetry (DSC) and UV–VIS absorption spectroscopy were used to obtain the characteristics of
blood serum from newborn rat’ after maternal treatment with cyclophosphamide in comparison with control. The obtained DSC
curves reveal a complex endothermic peak due to the unfolding process of various serum proteins. Thermal profiles and absorption
spectra of blood serum are sensitive to the age of newborns as well as to effect of maternal administration of cyclophosphamide.
The most significant disturbances in serum proteome were observed for 14-day old newborns. The thermodynamic parameters: enthalpy
change (∆H), the normalized first moment (M1) of the thermal transition with respect to the temperature axis and the ratio of Cpex at 70 and 60 °C describing denaturation contributions of globulin forms in respect to unliganded albumin with haptoglobin
was estimated. Moreover, the second derivative spectroscopy in the UV region was used to resolve the complex protein spectrum.
The differences in blood serum detected by DSC and UV–VIS confirm a potential usefulness of these methods for diagnostic and
monitoring changes with age as well as the pathological state of blood serum.
Authors:K. Michalik, Zofia Drzazga, Anna Michnik, and M. Kaszuba
scanning calorimetry study of the thermal behavior of nevirapine and azidothymidine
in water solution was carried out. For nevirapine scan rate dependent and
irreversible endothermic peak were found. Thermal degradation of nevirapine
as well as NVP – AZT mixture is relatively well described by the model
involving only one irreversible step determined by a first-order rate constant.
The estimated kinetic constants and activation energies indicate that the
degradation process proceeds slower for nevirapine in presence of AZT ligands
than without them.
Authors:Anna Michnik, K. Michalik, A. Kluczewska, and Zofia Drzazga
The thermal denaturation process of bovine and human
both fatty acid containing and fatty acid free albumins in aqueous solution
was studied by use of differential scanning calorimetry. Human serum albumins
were found to be more stable than their bovine counterparts. Fatty acid free
albumins were characterized as generally less stable, more susceptible to
aggregation, their unfolding endothermic transition was less cooperative and
with the smaller degree of reversibility. Deconvolution analysis with using
a non-two-state model with two component transitions showed essential differences
in the thermodynamic parameters between all studied albumins, particularly
regarding the high-temperature component transition.