Differential Scanning Calorimetry Profiles Research Articles

Consequences of a six residual deletion from the N-terminal of rabbit muscle creatine kinase

A mutant of dimeric rabbit muscle creatine kinase (CK), in which six residues (residues 2–7) at the N-terminal were removed by the PCR method, was studied to assess the role of these residues in dimer cohesion and to determine the structural stability of the protein. The specific activity of the mutant was 70.39% of that of the wild-type CK, and the affinity for Mg-ATP and CK substrates was slightly reduced compared with the wild-type protein. The structural stability of the mutant was investigated by a comparative equilibrium urea denaturation study and a thermal denaturation study. The data acquired by intrinsic fluorescence and far-UV circular dichroism (CD) during urea unfolding indicated that, the secondary and tertiary structures of the mutant were more stable than those of wild-type CK. Furthermore, results of 8-anilino-1-naphthalene-sulfonic acid (ANS) fluorescence demonstrated that the hydrophobic surface of the mutant CKND 6 was more stable during urea titration. Data from size exclusion chromatography (SEC) experiments indicated that deletion of the six N-terminal residues resulted in a relatively loose molecular structure, but the dissociation of the mutant CKND 6 occurred later during the unfolding process than for wild-type CK. Consistent with this result, the differential scanning calorimetry (DSC) profiles demonstrated that the thermal stability of the enzyme was increased by removal of the six N-terminal residues. We conclude that a more stable quaternary structure was obtained by deletion of the six residues from the N-terminal of wild-type CK.

Use of DSC to detect the heterogeneity of hydrothermal stability in the polyphenol-treated collagen matrix.

The hydrothermal stability of the collagen matrixes treated with plant polyphenols (tannins) depends on not only the strength of the polyphenol-collagen interactions but also the distribution uniformity of polyphenolic molecules within the collagen fibrils. Traditional methods of uniformity tests rely heavily on the expertise of workers and are thus subjective. This paper describes a differential scanning calorimetry (DSC) study of the sheepskin collagen samples treated with hydrolyzable tannins, including two commercial tannins' extracts (chestnut and valonea), two pure ellagitannins (vescalagin and castalagin), and six synthetic gallotannins (di-galloyl-ethylene glycol (DGE), tri-galloyl-glycerol, tetra-galloyl-meso-erythritol, penta-galloyl-adonitol, penta-galloyl-glucose, and hexa-galloyl-ducitol). The collagen sample without polyphenol treatment and the sample treated with DGE showed a single sharp peak in their DSC thermogram with a full peak width at half height (fwhh) of 3-4 degrees C. The samples treated with other tannins all showed multiple peak DSC profiles with the fwhh of each peak at about 3-4 degrees C. These multiple peak profiles imply that in these polyphenol-treated samples, there is a distribution of collagen molecules having different hydrothermal stability. The results have demonstrated that DSC offers an objective method to detect the stability heterogeneity of collagen matrixes in the solid state, providing a useful tool for the leather industry to evaluate the uniformity of leather tanning.

Calorimetric evidence for conformational transitions of RNase A in the presence of cytidine 2′,3′-cyclic phosphate

Thermal denaturation of ribonuclease A (RNase A) complex with cytidine 3′-monophosphate (3′CMP) was studied by differential scanning calorimetry (DSC). The kinetic and binding studies of RNase A with cytidine 2′,3′-cyclic phosphate (cCMP) as a substrate, and 3′CMP as a ligand were also investigated by difference spectrophotometry. The obtained kinetic saturation curve reveals the occurrence of an anomalous non-hyperbolic shape at high substrate concentrations, and a biphasic binding isotherm. These phenomena indicate that a conformational change is occurring with RNase A during the hydrolysis of cCMP. A combination of kinetic and thermodynamic studies tends to elucidate the reasons for the formation of a non-hyperbolic behavior in a kinetic saturation curve. The thermal profile of the enzyme-3′CMP complexes shows a splitting of two distinct peaks with different structural stabilities of melting points ( T m) of 325 and 337 K. The bifurcate appearance of DSC profile of RNase A-3′CMP complexes manifests a physical view of a light kinetic structural transition. It is worthy to note, the direct binding (not via enzymatic reaction) of enzyme with 3′CMP indicates single DSC profile and monophasic binding isotherm.

Calorimetric evidence for conformational transitions of RNase A in the presence of cytidine 2′,3′-cyclic phosphate

Thermal denaturation of ribonuclease A (RNase A) complex with cytidine 3′-monophosphate (3′CMP) was studied by differential scanning calorimetry (DSC). The kinetic and binding studies of RNase A with cytidine 2′,3′-cyclic phosphate (cCMP) as a substrate, and 3′CMP as a ligand were also investigated by difference spectrophotometry. The obtained kinetic saturation curve reveals the occurrence of an anomalous non-hyperbolic shape at high substrate concentrations, and a biphasic binding isotherm. These phenomena indicate that a conformational change is occurring with RNase A during the hydrolysis of cCMP. A combination of kinetic and thermodynamic studies tends to elucidate the reasons for the formation of a non-hyperbolic behavior in a kinetic saturation curve. The thermal profile of the enzyme-3′CMP complexes shows a splitting of two distinct peaks with different structural stabilities of melting points (Tm) of 325 and 337 K. The bifurcate appearance of DSC profile of RNase A-3′CMP complexes manifests a physical view of a light kinetic structural transition. It is worthy to note, the direct binding (not via enzymatic reaction) of enzyme with 3′CMP indicates single DSC profile and monophasic binding isotherm.

Propranolol hydrochloride–anionic polymer binding interaction

Three different anionic polymers namely Eudragit S 100, Eudragit L 100-55 (methacrylic acid copolymers), and sodium carboxymethylcellulose (NaCMC) were used to evaluate the propranolol hydrochloride–anionic polymer interaction. The physical and chemical properties of propranolol hydrochloride and anionic polymer complex were investigated using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The DSC profiles demonstrated that the characteristic peak of propranolol hydrochloride cannot be found in the heating curve of the complexes, indicating that complex is different in physicochemical properties from the physical mixture of drug–polymer. The FTIR spectra also confirmed that there is an interaction between propranolol hydrochloride and methacrylic acid copolymers. The binding of the drug to the polymers was due to the existence of preferential hydrogen bonding between the amino group of the propranolol hydrochloride and the carboxylic functions of the polymers and that pH conditions can influence this binding.

Effect of storage conditions on differential scanning calorimetry profiles from thawed cod muscle

Differential scanning calorimetry (DSC) was used for measuring thermal denaturation (30–80°C) in cod fillets stored at −20°C and −30°C for up to 12 months and subsequently from 0 to 21 days in modified atmosphere at +2°C. The denaturation profiles were subjected to multivariate data analysis in order to extract the effects of the various storage conditions. The main effect of the storage conditions was the difference in the denaturation profiles between short time chill storage for all samples and long time chill storage for samples stored at −30°C. There was also a smaller effect due to the difference between short time frozen storage and long time frozen storage for samples stored at −20°C. The variation in the thermograms was primarily due to changes in size and position of the myosin, sarcoplasmatic protein and actin denaturation peaks, where variation in position could be related to changes in pH. Frozen storage at both temperatures and chill storage for samples previously stored at −30°C caused a decrease in the myosin denaturation peak. The relationship between the denaturation profiles and the water distribution (determined by low-field NMR relaxation) was found to involve mainly the two fastest relaxing populations (named III and IV), where IV is expected to contain the water most tightly bound to protein. The amount of water in pool III and IV appeared to be directly correlated to the changes in the denaturation profile during storage: the amount of M IV increased and M III decreased when myosin and sarcoplasmatic proteins denatured and the actin denaturation peak shifted to a lower temperature.

Domain analysis of human apotransferrin upon interaction with sodium n-dodecyl sulphate: differential scanning calorimetry and circular dichroism approaches

The domain analysis of human apotransferrin (apo hTF) upon interaction with sodium n-dodecyl sulphate (SDS) was studied by differential scanning calorimetry (DSC) and circular dichroism (CD) using Hepes buffer, 100 mM, at pH=7. The DSC profile for apo hTF depicts two distinct peaks, while when interacted with SDS, the DSC peaks are shifted to the left as well as the area under the peaks are reduced. The DSC profile without the presence of SDS has two dissimilar peaks including two melting points ( T m=60 °C, T m=70 °C). This profile in the presence of low concentrations of SDS shows two nearly similar peaks and decrement of T m values about 5 °C relative to profile in the absence of SDS. The DSC excess heat capacity was deconvoluted for apo hTF in the presence of SDS. The interaction of SDS with apo hTF induced two dissimilar subdomains for each domain, but each domain having two subdomains similar to each other. The CD experiment of apo hTF–SDS complexes shows the decrement of α-helix content and the increment of β-sheet structure relative to protein in the absence of SDS. The α-helix tendency calculation shows more α-helix content for N domain relative to C domain. Here SDS at low concentration plays a role as a good probe to define the electrostatic moiety for N domain relative to C domain that is initiated from dissimilarity of α-helicity of two domains.

Lead-free Sn-Ag and Sn-Ag-Bi solder powders prepared by mechanical alloying

A mechanical alloying (MA) process was used to produce lead-free solder pastes of Sn-3.5Ag and the Sn-3.5Ag-4Bi system. Because of the high energy induced by repeated fracturing and welding, the grinding media played an important role during the MA process. A ceramic container was used to provide stronger impact force, which could induce phase transformation better than a Teflon container. In addition, it was found that 1-cm balls could fracture Bi particles and promote their dissolution into the Sn matrix. On the contrary, the milling process tended to achieve homogeneous mixing when using 3-mm balls. The MA powders, after milling with 3-mm balls, showed a small endothermic peak from the differential scanning calorimetry (DSC) profile at around 138°C, which was the eutectic temperature of Sn-Bi. The melting points of the MA powders in the ceramic container were measured to be 221°C and 203°C, respectively, for Sn-3.5Ag and Sn-3.5Ag-4Bi from the DSC curves. The reduced melting point ensured the complete melting during reflow with a peak temperature of 240°C. The formation of Ag3Sn was also observed from the x-ray diffraction peaks, indicating successful alloying by MA. The solder pastes could, thus, be produced by adding flux into the MA powders. The wetting property of the solder joint was also evaluated. The as-prepared solder pastes on electroless Ni-P/Cu/Si showed good metallurgical bonding with a contact angle less than 20°.

Physical Characterization and Macrophage Cell Uptake of Mannan-Coated Nanoparticles

Previously, we reported on a cationic nanoparticle-based DNA vaccine delivery system engineered from warm oil-in-water microemulsion precursors. In these present studies, the feasibility of lyophilizing the nanoparticles and their thermal properties were investigated. Also, the binding and uptake of the nanoparticles by a macrophage cell line were studied. The nanoparticles (prior to pDNA coating) were freeze-dried with lactose or sucrose as cryoprotectants. The stability of lyophilized nanoparticles at room temperature was monitored and compared to that of the aqueous nanoparticle suspension. The thermal properties of the nanoparticles were investigated using differential scanning calorimetry (DSC). The nanoparticles, coated or uncoated with mannan as a ligand, were incubated with a mannose receptor positive (MR+) mouse macrophage cell line (J774E), at either 4°C or 37°C to study the binding and uptake of the nanoparticles by the cells. It was found that lactose or sucrose (1–5%, w/v) was required for successful lyophilization of the nanoparticles. After 4 months of storage, the size of lyophilized nanoparticles did not significantly increase while those in aqueous suspension grew by over 900%. Unlike its individual components, emulsifying wax (m.p., ˜55°C) and hexadecyltrimethyl ammonium bromide, the nanoparticles showed a melting point of ˜90°C. Moreover, the DSC profile of the nanoparticles was different from that of the physical mixture of emulsifying wax and CTAB. After 1 hour incubation at 37°C, the uptake of mannan-coated nanoparticles was 50% higher than that of the uncoated nanoparticles. At 4°C and after one hour, the binding of the mannan-coated nanoparticles by J774E was over 2-fold higher than that of the uncoated nanoparticles. This increase in J774E binding could be abolished by preincubating the cells with free mannan, suggesting that the binding and uptake were receptor-mediated. In conclusion, the nanoparticles were lyophilizable, and lyophilization was shown to enhance the stability of the nanoparticles. DSC provided evidence that the nanoparticles were not a physical mixture of their individual components. Finally, cell binding and uptake studies demonstrated that the nanoparticles have potential application for cell-specific targeting.

Thermal stability of Li xCoO 2 cathode for lithium ion battery

It is well known that charged Li x CoO 2 ( x<1) is metastable, and that oxygen evolution has been observed at temperatures above 200 °C. Li x CoO 2, delithiated by a chemical method using H 2SO 4, was investigated by means of differential scanning calorimetry (DSC) with/without an electrolyte (1 M LiPF 6/ethylene carbonate (EC)+dimethyl carbonate (DMC)). The lithium content x in the delithiated Li x CoO 2 was determined by atomic absorption spectroscopy. The DSC profile of Li 0.49CoO 2 showed two exothermic peaks, one beginning at 190 °C and the other beginning at 290 °C. From high-temperature X-ray diffraction (XRD), it was found that the first peak, from 190 °C, was the phase transition from a monoclinic ( R3̄ m) to a spinel structure ( Fd3 m). The DSC measurements of Li 0.49CoO 2 with the electrolyte at various mixing ratios showed two exothermic peaks, one beginning at 190 °C and the other at 230 °C. The exothermic heat of each peak was proportional to the amount of Li 0.49CoO 2. The peak starting at 190 °C probably resulted from the decomposition of solvent due to an active cathode surface, and the peak starting at 230 °C was electrolyte oxidation caused by released oxygen from Li 0.49CoO 2. The exothermic heat from 190 to 230 °C based on cathode weight was 420±120 J/g, and that from 230 to 300 °C was 1000±250 J/g.

The thermal analysis of nonezymatic glycosylation of human serum albumin: differential scanning calorimetry and circular dichroism studies

The stability of human serum albumin (HSA) is studied before and after incubation with glucose utilizing differential scanning Calorimetry (DSC) and circular dichroism (CD) techniques. The incubation of HSA with glucose results in its nonenzymatic glycosylation that is glycosylated HSA (GHSA) formed in glucose concentrations (8.25, 16.5 and 27.5 mM) in a temperature dependent manner. The DSC profiles of GHSA samples, which indicate changes in heat capacity C p and C p excess versus temperature, were obtained and the thermal denaturation reversibility of each sample was assessed up to 80 °C. The melting point ( T m), the change of enthalpy, and the heat capacity for GHSA at different glucose concentrations were obtained. The results showed that glucose at lower concentrations induces the destabilization of HSA while at higher concentrations induces its stabilization. In addition, considerable conformational changes in HSA were observed after incubation with glucose. This was demonstrated through deconvolution of DSC profiles that imply the formation of new energetic domains, which were further confirmed by the presence of α-helices in the CD spectrum.

Acid-induced changes in thermal stability and fusion activity of influenza hemagglutinin.

The conformational and thermal stability of full-length hemagglutinin (HA) of influenza virus (strain X31) has been investigated using a combination of differential scanning calorimetry (DSC), analytical ultracentrifugation, fluorescence, and circular dichroism (CD) spectroscopy as a function of pH. HA sediments as a rosette comprised of 5-6 trimers (31-35 S) over the pH range of 7.4-5.4. The DSC profile of HA in the native state at pH 7.4 is characterized by a single cooperative endotherm with a transition temperature (Tm) of 66 degrees C and unfolding enthalpy (DeltaH(cal)) of 800 kcal x (mol of trimer)(-1). Upon acidification to pH 5.4, there is a significant decrease in the transition temperature (from 66 to 45 degrees C), unfolding enthalpy [from 800 to 260 kcal x (mol of trimer)(-1)], and DeltaH(cal)/DeltaH(vH) ratio (from 3.0 to approximately 1.3). Whereas the far- and near-UV ellipticities are maintained over this pH range, there is an acid-induced increase in surface hydrophobicity and decrease in intrinsic tryptophanyl fluorescence. The major contribution to the DSC endotherm arises from unfolding HA1 domains. The relationship between acid-induced changes in thermal stability and the fusion activity of HA has been examined by evaluating the kinetics and extent of fusion of influenza virus with erythrocytes over the temperature and pH range of the DSC measurements. Surprisingly, X31 influenza virus retains its fusion activity at acidic pH and temperatures significantly below the unfolding transition of HA. This finding is consistent with the notion that the fusion activity of influenza virus may involve structural changes of only a small fraction of HA molecules.

Heat Treatment Adaptations in Clostridium perfringens Vegetative Cells

Vegetative cells of Clostridium perfringens enterotoxigenic strains NCTC 8679, NCTC 8238, and H6 were grown at 37°C followed by a 60-min exposure to 28°C or 46°C. D10-values, as a measure of thermal resistance at 60°C, were significantly lower for 28°C exposures as compared with cultures given 37 and 46°C exposures. Following refrigeration at 4°C for 24 h, D10-values for the 37 and 46°C samples could not be differentiated from 28°C samples. Western immunoblot analyses of lysates from heat-adapted cells also detected the increased expression of proteins reacting with antiserum directed against the molecular chaperonins from Escherichia coli; GroEL, DnaJ, and the small acid soluble protein from Bacillus subtilis, SspC. Differential scanning calorimetry (DSC) identified thermal transitions corresponding to ribosomal protein denaturations at 72.1 ± 0.5°C. Any cellular heat adaptations in the DSC profiles were lost following refrigeration for several days to simulate minimally processed food storage conditions. Further analyses of high-speed pellets from crude cell extract fractions using two-dimensional gel electrophoresis detected the differential gene expression of at least four major proteins in heat-adapted vegetative cells of C. perfringens. N-terminal amino acid analyses identified two of the proteins as glyceraldehyde3-phosphate dehydrogenase and rubrerythrin. Both appear to have roles in this anaerobe under stressful conditions.

Assessment of the State of Water in Reconstituted Milk Protein Dispersions by Nuclear Magnetic Resonance (NMR) and Differential Scanning Calorimetry (DSC)

DSC profiles and relaxation NMR 1H signals were used to characterise highly hydrated milk protein dispersion (3 to 20 g per 100 g DM) with various micellar casein concentrations (3–15 g per 100 g of dispersion), whey protein concentrations (0–3 g per 100 g of dispersion), lactose concentrations (0–7.5 g per 100 g of dispersion), CaCl2concentration (0–2 mM) and pH (6.2–6.6). Results obtained with both techniques showed the predominant effect of micellar casein and lactose concentrations on the water state. Heat of fusion of water and amount of unfreezable water (0.49 g/g for dispersions without lactose and 0.60 g/g for lactose containing dispersions) measured by DSC varied mainly in lactose and native phosphocaseinate (NPC) content. Furthermore, NMR water relaxation behaviour was consistent with a three site relaxation model. Because of fast diffusive exchange, the relaxation rate observed was the sum of the free water relaxation rate, the hydration water relaxation rate and the exchangeable protons relaxation rate, weighted by their relative proportions. Analysis of the variation in relaxation rate with the sample composition confirmed that the hydration water was mainly influenced by the casein concentration and that the chemical exchange effect, such as the lactose effect, could be attributed to soluble macromolecules. NMR versus DSC results were also discussed.

Thermal Characterization of Sexithiophenes Regioselectively Functionalized with Electron Donor Methylsulfanyl Groups

The Differential Scanning Calorimetry (DSC) profile of a homogeneous series of regioregular β-methylsulfanyl sexithiophenes, with different substitution patterns and number of substituents, is reported. The DSC data show that the thermal characteristics of these compounds strongly depend on the regiochemistry of substitotion.

DSC Application in the Conservation Field

Differential scanning calorimetry (DSC) has been scarcely used in conservation field and in particular, in the study of painting layers. However DSC is a micro-destructive technique (sample from .05 to 1 mg can be analysed) because no pre-treatment of the sample is required and so it can give rapid and useful information. The aim of the present work is, in fact, to describe useful applications of DSC on the study of materials used in art. The analyses have been conducted under oxygen flow in order to register the thermo-oxidative reactions of the organic binder or protective. In the first part of the paper, materials of different chemical composition have been analysed to build up a data base of DSC profiles. Standard painting layers artificially degraded by treatment with ultraviolet light (365 nm) for 21 days and with NOx (5 ppm)have be en analysed. Comparing the behaviour of the treated to the reference sample, it is useful to study what kind of changes the treatments have produced on the sample. Another possible application of DSC is the study of the formation of the film; analysing the raw,liquid binders and the different naturally aged films an evolution of the chemical structure canbe registered.

Calorimetric characterization of critical targets for killing and acquired thermotolerance in yeast.

We characterized thermal behaviours of cellular components by differential scanning calorimetry (DSC) in order to investigate how Saccharomyces cerevisiae cells acquire thermotolerance after heat shock or in stationary phase. Whole-cell DSC profiles consisted of at least five endothermic components over the range 45-75 degrees C for exponentially growing, heat-shocked and stationary-phase cells. In these profiles, we attempted to localize the endothermic profiles due to denaturation of the two critical targets which were predicted by using the Arrhenius parameters of hyperthermic killing of the cells (Obuchi et al., 1998). This prediction indicated that (a) the heat shock stabilized one family of targets and destabilized the other, while (b) arrest in stationary phase stabilized both targets. Therefore, the heat-shock response does not stabilize all cellular components, and arrest in stationary phase appears to stabilize cellular components in a different manner from the heat-shock response. It was not possible unambiguously to resolve the profiles of the critical targets in the DSC scans of whole cells. Components I (T(m)=49.7 degrees C) and II (T(m)=56.1 degrees C) may both include denaturations of critical targets 1 (T(m)=55.4 degrees C) and 2 (T(m)=53.0 degrees C) in exponential cells. Components I and II were both stabilized (T(m)=53.5 and 57.2 degrees C, respectively) in heat-shocked cells. Sub-cellular fractions suspended in 1.2 M trehalose solution, which mimics the cytosol in tolerant cells, were more stable than those in 0.6 M KCl, which mimics the cytosol in sensitive cells. The microsomal fractions in KCl and trehalose had endothermic profiles in similar temperature ranges to those predicted for sensitive and tolerant cells, respectively. This agreement suggests that the microsomal fraction may contain critical targets, and that trehalose accumulation in the heat-shocked and in the stationary phase yeast cells is a stabilizer of cellular components.

Dsc Evaluations in F.c.c. Solid Solutions of Short-range-order Kinetics As Influenced by Bound Vacancies

A modified first order kinetic law, which describes the roles of bound and unbound vacancies, is proposed in order to predict defect decay and short-range-order kinetics of quenched binary alloys during linear heating experiments. The model has been applied to differential scanning calorimetry (DSC) curves of Cu–5 at%Zn quenched from different temperatures. Activation energy for migration of solute-vacancy complexes was also assessed from the kinetics of short-range-order using DSC traces. A value of 89.5±0.32 kJ mol–1 was obtained. The relative contribution of bound and unbound vacancies to the ordering process as influenced by quenching temperature was determined. In conjunction, a parametric study of the initial total defect concentration and effective energy for defect migration was performed in order to envisage their influence on the calculated DSC profiles.

Novel features in solid phase transition behavior of TlI

Novel features in solid phase transition behavior in TlI are reported. These features include transition temperature T t = 181 ± 2°C and transition enthalpy Δ H t = 1180 ± 50 J/mol in contrast with the accepted 172°C and 875 J/mol, respectively. Differential scanning calorimetry (DSC) profiles exhibit endothermic peak broadness and doublets in contrast to the earlier reported single sharp endotherm. These results are interpreted in terms of possible polytypism arrangement in β-TlI and/or β-TlI particle size below the critical value required for transition singularity.

MEARA sequence repeat of human CstF-64 polyadenylation factor is helical in solution. A spectroscopic and calorimetric study.

The primary structure of the human CstF-64 polyadenylation factor contains 12 nearly identical repeats of a consensus motif of five amino acid residues with the sequence MEAR(A/G). No known function has yet been ascribed to this motif; however, according to secondary structure prediction algorithms, it should form a helical structure in solution. To validate this theoretical prediction, we synthesized a 31 amino acid residue peptide (MEARA(6)) containing six repeats of the MEARA sequence and characterized its structure and stability by circular dichroism (CD) spectroscopy and differential scanning calorimetry (DSC). No effects of concentration on the CD or DSC properties of MEARA(6) were observed, indicating that the peptide is monomeric in solution at concentrations up to 2 mM. The far UV-CD spectra of MEARA(6) indicates that at a low temperature (1 degrees C) the MEARA(6) peptide has a relatively high helical content (76% at pH 2.0 and 65% at pH 7.0). The effects of pH and ionic strength on the CD spectrum of MEARA(6) suggest that a number of electrostatic interactions (e.g., i, i + 3 Arg/Glu ion pair, charge-dipole interactions) contribute to the stability of the helical structure in this peptide. DSC profiles show that the melting of MEARA(6) helix is accompanied by positive change in the enthalpy. To determine thermodynamic parameters of helix-coil transition from DSC profiles for this peptide, we developed a new, semiempirical procedure based on the calculated function for the heat capacity of the coiled state for a broad temperature range. The application of this approach to the partial molar heat capacity function for MEARA(6) provides the enthalpy change for helix formation calculated per amino acid residue as 3.5 kJ/mol.