Comparative study on heat stability of camel and bovine apo and holo α-lactalbumin

The stability of camel α-lactalbumin (α-la) against heat denaturation was measured, using circular dichroism (CD) and fluorescence spectroscopy, as well as differential scanning calorimetry (DSC). The experiments were performed in the presence of saturating concentrations of calcium as well as in the presence of EDTA, yielding to the apo form of α-la. The change in heat capacity (ΔCp) suggests a greater contribution of hydrophobic interactions to the stability of holo camel α-la than in its bovine counterpart. Overall the results obtained in this study suggest a greater stability of camel α-la than the bovine protein in both holo and apo states. Also CD experiments showed similar secondary structure for camel and bovine α-la and secondary structure of camel α-la was better preserved than that of bovine α-la during heat denaturation. The differences in thermal stability between the proteins from two species can be primarily ascribed to the difference in the quantity of hydrophobic interactions involved in their folding.

Download Full-text

Effects of physicochemical factors on the secondary structure of β-lactoglobulin

Journal of Dairy Research ◽

10.1017/s0022029900031575 ◽

1996 ◽

Vol 63 (1) ◽

pp. 97-109 ◽

Cited By ~ 97

Author(s):

Joyce I. Boye ◽

Ashraf A. Ismail ◽

Inteaz Alli

Keyword(s):

Thermal Stability ◽

Differential Scanning Calorimetry ◽

Fourier Transform ◽

Secondary Structure ◽

Random Coil ◽

Scanning Calorimetry ◽

Effects Of Ph ◽

Complementary Techniques ◽

The Fourier Transform ◽

Β Lactoglobulin

SummaryFourier transform infrared spectroscopy and differential scanning calorimetry were used as complementary techniques to study changes in the secondary structure of β-lactoglobulin under various physicochemical conditions. The effects of pH (3–9), NaCl (0–2 M), and lactose, glucose and sucrose (100–500 g/l) in the temperature range 25–100 °C on the conformation sensitive amide I band in the i.r. spectrum of β-lactoglobulin in D2O solution were examined. The 1692 cm−1 band in the amide I band profile had not been definitively assigned in previous studies of the i.r. spectrum of β-lactoglobulin. The decrease in this band at ambient temperature with time or upon mild heating was attributed to slow H-D exchange, indicating that it was due to a structure buried deep within the protein. The disappearance of the 1692 cm−1 band on heating was accompanied by the appearance of two bands at 1684 and 1629 cm–1, assigned to β-sheets. The 1692 cm−1 band was therefore attributed to a β-type structure. β-Lactoglobulin showed maximum thermal stability at pH 3 and was easily denatured at pH 9. On denaturation, the protein unfolded into more extensive random coil structures at pH 9 than at pH 3. After 10 h at pH 9 (25 °C), β-lactoglobulin was partly denatured. Heating to 60–80 °C generally resulted in the loss of secondary structure. At all pH values studied, two new bands at 1618 and 1684 cm−1, characteristic of intermolecular β-sheet structure and associated with aggregation, were observed after the initial denaturation. Differential scanning calorimetry studies indicated that the thermal stability of β-lactoglobulin was enhanced in the presence of sugars. The Fourier transform i.r. results obtained provide evidence that sugars promoted the unfolding of β-lactoglobulin via multiple transition pathways leading to a transition state resisting aggregation.

Download Full-text

Thermal Stability and Optical Properties of Er3+ Doped BaTi2O5 Glasses

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.39-40.243 ◽

2008 ◽

Vol 39-40 ◽

pp. 243-246 ◽

Cited By ~ 16

Author(s):

A. Masuno ◽

H. Inoue ◽

J. Yu ◽

Yasutomo Arai ◽

Fumiaki Otsubo

Keyword(s):

Thermal Stability ◽

Differential Scanning Calorimetry ◽

Refractive Indices ◽

High Solubility ◽

Containerless Processing ◽

Scanning Calorimetry ◽

Substitution Ratio ◽

Aerodynamic Levitation ◽

The Stability ◽

Crystallization Onset

Er3+ doped BaTi2O5 spherical glasses were prepared using a containerless processing with an aerodynamic levitation furnace. These glasses were found to have high solubility of Er3+ and the substitution ratio of Er3+ for Ba2+ reached 30 %. Differential scanning calorimetry measurements revealed that the glass transition temperature Tg and the crystallization onset temperature Tx shifted to high temperatures and the value of T (= Tx – Tg) increased with substitution of Er3+, indicating that the stability against crystallization improved. We found that these glasses had high refractive indices exceeding 2.1 with low Abbe numbers of approximately 20.

Download Full-text

Heat capacity and thermal expansion of yttrium tantalate

Доклады Академии наук ◽

10.31857/s0869-56524842181-183 ◽

2019 ◽

Vol 484 (2) ◽

pp. 181-183

Author(s):

A. V. Khoroshilov ◽

A. A. Ashmarin ◽

V. N. Guskov ◽

E. G. Sazonov ◽

K. S. Gavrichev ◽

...

Keyword(s):

Differential Scanning Calorimetry ◽

Heat Capacity ◽

Thermal Expansion ◽

Heat Capacities ◽

Unit Cell ◽

Unit Cell Parameters ◽

Scanning Calorimetry ◽

Crystal Lattices ◽

Cell Parameters ◽

The Difference

The isobaric heat capacities of two monoclinic (M' and M) modifications of yttrium orthotantalate at temperatures 5–1300 K have been measured by the adiabatic and differential scanning calorimetry methods. It has been demonstrated that the difference in structure between the crystal lattices of M' and M has small effect in the heat capacity, and the difference between the heat capacities of these phases Cp(M)-Cp(M') is small, always positive, and increases in the range of the lowest temperatures. The unit cell parameters of M-YTaO4 have been determined as a function of temperature in the range 300–1173 K.

Download Full-text

Thermal Behavior of Chalcogenide glasses Te90Se10 and Se90Te10

SAMRIDDHI A Journal of Physical Sciences Engineering and Technology ◽

10.18090/samriddhi.v7i2.8636 ◽

2015 ◽

Vol 7 (02) ◽

pp. 113-118

Author(s):

Arvind Kumar Verma ◽

Anchal Srivastava ◽

R. K Shukla ◽

K. C Dubey

Keyword(s):

Thermal Stability ◽

Differential Scanning Calorimetry ◽

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Glass Forming Ability ◽

Scanning Calorimetry ◽

Glass Forming ◽

The Difference ◽

Thermal Stability Of

In the present research work melt quenching method has been adopted to prepare the glassy Te-rich (Te90Se10) and Se-rich (Se90Te10 ) Chalcogenide at a pressure of 10-2 Torr with constant Temperature at 1000°C for 8 hours. Devitrification characteristics of the pure glassy Chalcogenide Te90Se10 and Se90Te90 were investigated by using Differential scanning Calorimetry (DSC) 4000 Perkin Elmer. All the measurements carried out at fixed heating rate 10 0C/min under non-isothermal conditions. The Glass transition temperature (Tg) and other thermal properties were examined by temperature modulated differential scanning Calorimetry at 40 oC to 445 oC. Glass transition temperature (Tg) represents the strength or rigidity of the glass structure. Tg affords valuable information on the thermal stability of the glassy state but Tg alone does not give any information on the glass forming tendency. The difference of the Peak crystallization temperature (Tp) and Glass transition temperature (Tg) is a strong indication of the thermal stability. The higher the value of Tc and Tg the greater is the thermal stability. Glass transition temperature (Tg=2160C) of Tellurium rich (Te90Se10) is more than Glass transition temperature (Tg=730C) of Selenium rich (Se90Te90) due to semi metallic nature of Tellurium. The difference of (Tp-Tg) is a strong indicator of both the thermal stability and Glass forming ability (GFA). Higher the value of (Tp-Tg), higher is the thermal stability and GFA because higher values of this difference indicate more kinetic resistance to the crystallization. Glass forming ability (GFA) and thermal stability of Te90Se10 is greater than Se90Te90. For memory and switching materials, glass thermal stability and GFA parameters are very important. Intensity of Se-rich (Se90Te10) is more than Te-rich (Te90Se10) and both samples are polycrystalline in nature.

Download Full-text

Thermal Stability of N-Heterocycle-Stabilized Iodanes – A Systematic Investigation

10.26434/chemrxiv.8964848 ◽

2019 ◽

Author(s):

Andreas Boelke ◽

Yulia A. Vlasenko ◽

Mekhman S. Yusubov ◽

Boris Nachtsheim ◽

Pavel Postnikov

Keyword(s):

Thermal Stability ◽

Differential Scanning Calorimetry ◽

Thermogravimetric Analysis ◽

Systematic Investigation ◽

Scanning Calorimetry ◽

Thermal Stability Of

The thermal stability of pseudocyclic and cyclic N-heterocycle-stabilized (hydroxy)aryl- and mesityl(aryl)-l3-iodanes (NHIs) through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) is investigated. NHIs bearing N-heterocycles with a high N/C-ratio such as triazoles show among the lowest descomposition temperatures and the highest decomposition energies. A comparison of NHIs with known (pseudo)cyclic benziodoxolones is made and we further correlated their thermal stability with reactivity in a model oxygenation.

Download Full-text