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Theory of cold denaturation of proteins  [PDF]
Arieh Ben-Naim
Advances in Biological Chemistry (ABC) , 2013, DOI: 10.4236/abc.2013.31005
Abstract:

A new approach to the problem of cold denaturation is presented. It is based on solvent-induced effects operating on hydrophilic groups along the protein. These effects are stronger than the corresponding hydrophobic effects, and they operate on the hydrophilic groups which are plentiful than hydrophobic groups. It is shown that both heat and cold denaturation can be explained by these hydrophilic effects.

Albumen protein and functional properties of gelation and foaming
Alleoni, Ana Cláudia Carraro;
Scientia Agricola , 2006, DOI: 10.1590/S0103-90162006000300013
Abstract: hen eggwhite proteins have been extensively utilized as ingredients in food processing because of their unique functional properties, such as gelling and foaming. this work reviews the molecular basis of the eggwhite proteins targeting the development of these functional properties during processing.
Interaction of Cationic and Anionic Phthalocyanines with Adenosine Deaminase, Molecular Dynamics Simulation and Docking Studies  [PDF]
Davood Ajloo, Seyyed Morteza Fazeli, Farhad Janbaz Amirani
Computational Molecular Bioscience (CMB) , 2013, DOI: 10.4236/cmb.2013.34010
Abstract: Interactions of anionic, cationic and metal phthalocyanine with adenosine deaminase were studied by molecular dynamics and docking simulation. Structural parameters such as solvent accessible surface area (SAS), mid-point of transition temperature (Tm), radial distribution function (RDF) and hydrogen bond, helix, coil, beta percentage and other physical parameters were obtained. The denaturation of adenosine deaminase (ADA) by heat, anionic and cationic phthalocyanines was compared. A series of 20 ns simulation performed at temperatures ranging from 275 to 450 K, starting from the ADA native structure. Results of radial distribution functions (RDFs) showed that metallic derivative at low concentration behaves the same as osmolytes that increases the beta form and increases the enzyme stability. Molecular docking studies have been carried out to confirm the simulation results. Investigation of binding site and free energy confirmed that the efficiency of interaction with adenosine deaminase depends on metal core. Binding energy of non-metallic form is more negative than metallic form and it significantly decreases for phthalocyanine. Self-aggregation of anionic phthalocyanine decreases in comparison with cationic derivative, therefore enzyme denaturation in the presence of anionic form is higher than the other. Furthermore, thermal stability of the enzyme also depends on temperature in presence of phthalocyanine. Binding site of phthalocyanine on the enzyme has been identified by docking analysis.
Pressure- and Urea-Induced Denaturation of Bovine Serum Albumin: Considerations about Protein Heterogeneity  [PDF]
Douglas Ricardo Norberto, Joelma Mauricio Vieira, Ancelmo Rabelo de Souza, Jose Ailton Conceicao Bispo, Carlos Francisco Sampaio Bonafe
Open Journal of Biophysics (OJBIPHY) , 2012, DOI: 10.4236/ojbiphy.2012.21002
Abstract: Urea denatures proteins at different concentrations, depending on the experimental conditions and the protein. We in-vestigated the pressure-induced denaturation of bovine serum albumin (BSA) in the presence of subdenaturing concen-trations of urea based on a two-state equilibrium. Pressure-induced denaturation was enhanced at urea concentrations ([U]) of 3.5 M to 8.0 M, with the free energy of denaturation at atmospheric pressure ranging from +5.0 to –2.5 kJ/mol of BSA. The m values appeared to be biphasic, with m1 and m2 of 0.92 and 2.35 kJ mol–1?M–1, respectively. Plots of versus ln[U] yielded values of u, the apparent stoichiometric coefficient, of 1.68 and 6.67 mol of urea/mol of BSA for m1 and m2, respectively. These values were compared with the m and u values of other monomeric proteins reported in or calculated from the literature. The very low values of u systematically observed for proteins were suggestive of heterogeneity in the free energy of denaturation. Thus, a u value of 140 mol of urea/mol of BSA may indicate the existence of a heterogeneous molecular population with respect to the free energy of dena-turation.
DSC study of cold and heat denaturation of β-lactoglobulin A with urea
Bangning Wang,Fu Tan
Chinese Science Bulletin , 1997, DOI: 10.1007/BF03182783
Abstract:
DSC study of cold and heat denaturation of β-lactoglobulin A with urea
科学通报(英文版) , 1997,
Abstract:
Tratamiento Térmico de Leche: Influencia del pH y CaCl2 en la Elaboración de Queso Cuartirolo
Sbodio,Oscar A; Tercero,Esteban J; Zannier,Mirta S; Revelli,Germán R;
Información tecnológica , 2010, DOI: 10.4067/S0718-07642010000500014
Abstract: the effect of ph (6.2-6.6) and cacl2 addition (200 - 600 mg l-1) was studied, with the objective of improving the coagulation properties of whole milk treated under mild condition of temperature, 10 min at 73 °c. the hot wire method to monitor rennet coagulation induced through acidification with glucono-5-lactone was employed. at ph 6.4 and 6.6 the coagulum of heated milk presented lower coagulation time (p<0.05), increased máximum voltage and time where they reach máximum voltage, and a decreased in whey separation, compared to those of coagulum produced by unheated milk. the selected conditions of ph 6.4 and cacl2 added 400 mg l-1, used in the process of cuartirolo cheese proved to be the best condition to increase the yield in 8.9% on a dry basis, without loosing consumer's acceptance.
Effect of urea on biomimetic aggregates
Brazilian Journal of Medical and Biological Research , 1997, DOI: 10.1590/S0100-879X1997000200004
Abstract: the effect of urea on biomimetic aggregates (aqueous and reversed micelles, vesicles and monolayers) was investigated to obtain insights into the effect of the denaturant on structured macromolecules. direct evidence obtained from light scattering (static and dynamic), monolayer maximum isothermal compression and ionic conductivity measurements, together with indirect evidence from fluorescence photodissociation, fluorescence suppression, and thermal reactions, strongly indicates the direct interaction mechanism of urea with the aggregates. preferential solvation of the surfactant headgroups by urea results in an increase in the monomer dissociation degree (when applied), which leads to an increase in the area per headgroup and also in the loss of counterion affinities
Effect of Heat Treatment on Buffalo (Bubalus bubalis) Lactoperoxidase Activity in Raw Milk
H. Tayefi-Nasrabadi,R. Asadpour
Journal of Biological Sciences , 2008,
Abstract: Inactivation kinetics of buffalo milk lactoperoxidase toward thermal processes was studied at isothermal condition over a range of 67 to 71°C. The analysis of inactivation rate constant data for the process of thermal denaturation of lactoperoxidase showed good agreement with a first-order reaction. Based on the thermal death time model, which describes first-order heat inactivation kinetics in the area of food processing and preservation, D-values and z-value (2.45°C) were obtained. Thermodynamic parameters were also calculated. The high values obtained for activation energy (920.43 kJ mol-1) and change in enthalpy of activation (~917 kJ mol-1) indicate that lactoperoxidase is one of the most heat stable enzymes in buffalo milk which high amount of energy is needed to initiate its denaturation. The mean buffalo lactoperoxidase activity in raw milk also was found 16.84 U mL-1.
Effect of urea on biomimetic aggregates
Florenzano F.H.,Politi M.J.
Brazilian Journal of Medical and Biological Research , 1997,
Abstract: The effect of urea on biomimetic aggregates (aqueous and reversed micelles, vesicles and monolayers) was investigated to obtain insights into the effect of the denaturant on structured macromolecules. Direct evidence obtained from light scattering (static and dynamic), monolayer maximum isothermal compression and ionic conductivity measurements, together with indirect evidence from fluorescence photodissociation, fluorescence suppression, and thermal reactions, strongly indicates the direct interaction mechanism of urea with the aggregates. Preferential solvation of the surfactant headgroups by urea results in an increase in the monomer dissociation degree (when applied), which leads to an increase in the area per headgroup and also in the loss of counterion affinities
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