The crystalline phase of dimyristoylphosphatidylethanolamine (DMPE)-water system was obtained by annealing the gel phase at
around −5°C for periods up to 30 days. It was investigated by differential scanning calorimetry and negative-stain electron
microscopy, particularly focusing on the behavior of water molecules. The crystalline phase showed a two-dimensional ribbonlike
structure composed of regularly-stacked lamellae with an interlamellar spacing narrower than that of the gel phase. The conversion
of the gel to crystalline phases on annealing was accompanied by a change in the bonding model of water molecules from a loosely-bound
interlamellar water to a more loosely-bound water outside the lamellae. Ice-melting curves were deconvoluted using a computer
program and different structures of water were estimated from enthalpy changes of each deconvoluted component. In accordance
with a micrograph, only the loosely-bound water of one molecule of H2O per lipid was shown to be located between lamellae of the crystalline phase.
Authors:M. Kiss, F. Könczöl, N. Farkas, D. Lőrinczy, and J. Belagyi
The effect of free radicals obtained in hydroxyl and cerium(IV)-nitrilotriacetic acid free radical generating systems on contractile
proteins (actin, myosin and their complexes in glycerinated muscle fibres) was studied using differential scanning calorimetry
and spin trapping electron paramagnetic resonance technique. The analysis of spectra showed that selective attack of thiol
groups – Cys-257 and Cys-374 residues of actin, and among others Cys-707 residue of myosin – and random attack of sidechains
of the main proteins of muscle tissue produced structural and functional changes, which affected the ATP hydrolysis cycle
and very likely the dynamics of actin. The melting curves obtained on protein systems support the view that global conformational
changes accompany the local damage of free radicals.
Authors:Y. Kawasaki, A. Kuboki, S. Ohira, and M. Kodama
properties of lipid bilayer systems are compared for symmetric chain sphingomyelin
(N-palmitoylsphingomyelin) and asymmetric chain sphingomyelin (N-lignoceroylsphingomyelin).
These sphingomyelins were semisynthesized by a deacylation- reacylation process
with a natural sphingomyelin used as a starting material. The number of differently
bound water molecules was estimated by a deconvolution analysis of the ice-melting
curves obtained by a differential scanning calorimetry (DSC) and was used
to construct a water distribution diagram for these water molecules. Similarly
to a natural sphingomyelin used for comparison, the asymmetric chain sphingomyelin
was found to form small size vesicles having an internal cavity and incorporate
15 water molecules per molecule of lipid into its cavity, in contrast with
5 H2O/lipid for freezable interlamellar water observed
for large size multilamellar vesicles formed by the symmetric chain sphingomyelin.
The thermal denaturation of β-lactoglobulin in the presence of urea and alkylurea solutions were measured. In the presence
of a high concentration of urea this protein shows not only heat but also cold denaturation. For studying the effect of temperature
two methods were used, differential scanning calorimetry (DSC) and UV-spectroscopy. DSC provides direct model-independent
determination of the transition enthalpy in comparison with UV-spectroscopy, which gives only apparent or van't Hoff enthalpy
of transition. The UV-melting curves were analyzed on the basis of a two-state approximation. The apparent standard enthalpies
of thermal denaturation, ΔHapp.o
, were compared with calorimetric ones.
The intermolecular interactions of molecules within the bilayer are responsible for the lipid organisation, e.g. domain formation, and the interaction and stabilisation of proteins within the lipid matrix. The mixing behaviour of lipids, which reflects the intrinsic molecular interactions, can be deduced from the shape of the phase diagram (temperature vs. mole fraction diagram), which is constructed from the analysis of heat capacity curves obtained by DSC. However, there are no objective procedures to determine the temperatures corresponding to the border lines of the coexistence region, i.e. the liquidus and solidus curves of the phase diagram. The main challenge to overcome is to develop an objective method for the correct determination of the onset and offset temperatures of the melting curve for every single transition curve in a standardized manner. The presented paper describes a procedure for the simulation of heat capacity curves. In a second step, based on the results from the heat capacity curve simulation, a phase diagram is calculated using a non-ideal, non-symmetric mixing model. The non-ideality parameters obtained from the calculation describe the intermolecular interaction of both components in a single phase region. Using this procedure, examples of the mixing behaviour of various binary phospholipid systems are analysed and it is shown how the mixing behaviour is influenced by external factors like e.g. the pH or ionic strength.
Authors:J. Rouland, A. Thorén, J. Fournival, and R. Céolin
A theoretical temperature-specific volume-molar fraction (T-v-x) phase diagram of the binary systemA-H2O presenting a hydrateH with congruent melting is studied. The phase diagram is divided into two subsystems by the one-component phase diagram of
the hydrateH. The eutectic invariant planes which occur in both subsystems are described. The relationships between the invariants are
Isochoric and isoplethal theoretical sections are given. The one-component phase diagram of the hydrateH is described. It is pointed out that the triple line solid-liquid-vapour which relates the congruent melting is not necessarily
perpendicular to the molar fraction axis. The means that the three phases, solid, liquid and vapour, have not necessarily
the same composition.
TheT-v-x representation gives an explanation to the deviation between the maximum of the melting curve and the stoichiometric composition
of the hydrate which is often observed in theT-x binary diagramA-H2O.
Authors:P. P. Fedorov, Yu. G. Sizganov, B. P. Sobolev, and M. Shvanner
A phase diagram of the system CaF2-GdF3 was studied by thermal and X-ray analysis. Two wide domains of solid solutions based on CaF2 and a high-temperature modification of α-GdF3 (LaF3-structural type) are present in this system. Two maxima were found on the melting curves of the Ca1−xGdxF2+x and α-(Gd1−yCayF3−y solid solutions, at 1428 ± 10‡ (5 mole % GdF3) and 1282 ± 5‡ (85 mole % GdF3), respectively. The coordinates of the eutectic are 60 mole % GdF3 and 1233 ± 5‡.
Authors:Alfréd Menyhárd, Gábor Dora, Zsuzsanna Horváth, Gábor Faludi, and József Varga
meltingcurve. We have to remark here that polymorphic composition can be evaluated from meltingcurves only if the samples were not cooled below T R ∗ (step 3), because βα-recrystallization occurs below T R ∗ . This process disturbs the melting profile
Authors:Fumina Sasaoka, Jin Suzuki, Toh-Ichi Hirata, Toshihiro Ichijo, Kazuhisa Furuhama, Ryô Harasawa, and Hiroshi Satoh
. , Sato , S. and Harasawa , R. ( 2010 ): Differential detection of hemotropic Mycoplasma species in cattle by meltingcurve analysis of PCR products . J. Vet. Med. Sci. 72 , 77 – 79 (Erratum, J. Vet. Med. Sci. 72 , 1704
Authors:B. Mayr, M. Holzheu, G. Schaffner, and et al.
. and Bartram, C. R. 2000: Rapid and reliable detection of Nras mutations in acute lymphoblastic leukemia by meltingcurve analysis using LightCycler technology. Leukemia 14 , 312-315.
Rapid and reliable detection of Nras