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: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.
Interactions of anionic surfactant sodium dodecyl sulphate (SDS) with vesicles formed by synthetic dialkyldimethylammonium
bromides i.e. didodecyldimethylammonium bromide (DDAB), ditetradecyldimethylammonium bromide (DTAB), dihexadecyldimethylammonium
bromide (DHAB) have been examined by using differential scanning microcalorimetry and electron transmission microscopy. The
temperatures and standard enthalpies characterising gel to liquid-crystal transitions increase significantly with increase
of SDS concentration for all investigated systems. It means that incorporation of SDS monomers in these vesicular bilayers
significantly stabilises their gel states. Moreover, in case of DDAB and DTAB vesicle systems added SDS limits kinetic features
of recorded isobaric heat capacity dependencies on temperature observed earlier for the pure vesicular solutions.
Authors:A. Goryunov, G. Sukhanova, A. Borisova, and S. Rozhkov
Differential scanning microcalorimetry and equilibrium thermohemolysis procedure were used to study the effect of acclimation
temperature on thermally induced transitions and thermoresistivity of fish (trout) erythrocyte membranes. Strong correlation
has been found between the rates and activation energies of erythrocyte thermohemolysis and acclimation temperature. Transition
temperatures of five thermodynamically irreversible and one partially reversible transitions at about 87C as well as the
overall shape of microcalorimetric curves of the erythrocyte ghosts do not vary with acclimation temperature. The results
suggest an essential conservation of phospholipid microenvironment of membrane skeleton proteins despite the compensatory
response in lipid composition of erythrocyte membrane bilayer.
Authors:Vera de Oliveira Tiera, Françoise Winnik, and Márcio Tiera
The interaction of chitosan and its N-dodecyl and poly(ethylene glycol) derivatives with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) vesicles was studied
to evaluate the influence of molecular architecture of the polymers on the liposomes. The study was carried out in aqueous
solution using differential scanning microcalorimetry (DSC) and dynamic light scattering. The interaction of these polymers
with DPPC vesicles altered the gel–liquid crystalline phase transition temperature and decreased both the enthalpy (ΔH) and cooperativity of the phase transition. The results obtained indicate that perturbations in the vesicles surface and
the incorporation of chitosan and its derivatives into the lipid bilayer upon polysaccharides interaction are responsible
for the formation of large vesicles.
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.