scholarly journals Differential-scanning-calorimetric study of the irreversible thermal denaturation of 8 kDa cytotoxin from the sea anemone Radianthus macrodactylus

1994 ◽  
Vol 299 (3) ◽  
pp. 731-733 ◽  
Author(s):  
G G Zhadan ◽  
V L Shnyrov
Keyword(s):  
Thermal Denaturation ◽  
Kinetic Constant ◽  
Sea Anemone ◽  
Differential Scanning Calorimetric ◽  
Calorimetric Study ◽  
Order Kinetic ◽  
Experimental Conditions ◽  
Rate Dependent ◽  
Scan Rate ◽  
State Kinetic

A differential-scanning-calorimetric study of the thermal denaturation of a sea-anemone (Radianthus macrodactylus) 8 kDa cytolytic toxin was carried out. The calorimetric traces were found to be irreversible and scan-rate-dependent under the experimental conditions employed. Scan-rate-dependent thermograms were explained in terms of a two-state kinetic model N k -->D, where k is a first-order kinetic constant that changes with temperature as given by the Arrhenius equation, N is the native state of the toxin, and D the denatured one.

Thermal Activation of Brazilian Smectite Clay (Primavera) and its Application for the Removal of Cadmium from Aqueous Solution

2020 ◽  
Vol 07 ◽  
Author(s):  
Marta Lígia Pereira da Silva ◽  
Tellys Lins Almeida Barbosa ◽  
Meiry Gláucia Freire Rodrigues
Keyword(s):  
Aqueous Solution ◽  
Kinetic Constant ◽  
Second Order ◽  
Order Kinetic ◽  
Experimental Conditions ◽  
X Ray ◽  
Thermally Activated ◽  
Study Results ◽  
Water Cleaning ◽  
Pseudo Second Order

Background: Region-based solutions for water cleaning could be critical to tackle the water challenges faced in enhancing the in the future. Brazilian Primavera clay is cheap, abundant, and an untested material that has the potential to be used for water cleaning. Objective: the objective of the present work was to thermally activate and characterize the Brazilian clay and then determine the potential to remove Cd2+ from an aqueous solution. Methods: Primavera clay was thermally activated at 300 oC and characterized using X ray diffraction, X-ray Spectroscopy Energy Dispersive, and N2 adsorption. Sorption equilibrium was determined using the following experimental conditions: constant pH 4.5, 5 h, and 27 oC. Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherms models were applied in order to determine the efficiency of clay used as an adsorbent. Adsorption kinetics was analyzed using the pseudo-second-order kinetic model. Results: In this study, results revealed that even though the heat treatment did not cause profound alterations on the clay structure(smectite) and surface area (78 m2 /g), a pseudo-second-order kinetic constant of 0.5563 mg/g/min was found for the cadmium removal. Conclusion: The mathematical models of the Langmuir and Temkin showed a better fit to the experimental data. A high affinity between the cadmium and the thermally activated Primavera clay was found up to 88 % with removal efficiencies.

scholarly journals Calorimetric Study of Helix aspersa Maxima Hemocyanin Isoforms

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Svetla Todinova ◽  
Yuliana Raynova ◽  
Krassimira Idakieva
Keyword(s):  
Thermal Denaturation ◽  
Irreversible Process ◽  
Arrhenius Equation ◽  
Helix Aspersa ◽  
Thermal Unfolding ◽  
Calorimetric Study ◽  
Scanning Calorimetry ◽  
Scan Rate ◽  
Annealing Procedure ◽  
Helix Aspersa Maxima

The thermal unfolding of hemocyanin isoforms, β-HaH and αD+N-HaH, isolated from the hemolymph of garden snails Helix aspersa maxima, was studied by means of differential scanning calorimetry (DSC). One transition, with an apparent transition temperature (Tm) at 79.88°C, was detected in the thermogram of β-HaH in 20 mM HEPES buffer, containing 0.1 M NaCl, 5 mM CaCl2, and 5 mM MgCl2, pH 7.0, at scan rate of 1.0°C min−1. By means of successive annealing procedure, two individual transitions were identified in the thermogram of αD+N-HaH. Denaturation of both hemocyanins was found to be an irreversible process. The scan-rate dependence of the calorimetric profiles indicated that the thermal unfolding of investigated hemocyanins was kinetically controlled. The thermal denaturation of the isoforms β-HaH and αD+N-HaH was described by the two-state irreversible model, and parameters of the Arrhenius equation were calculated.

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