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Physicochemical Changes of Antioxidant Peptides Hydrolyzed From Porcine Plasma Protein Subject to Free Hydroxyl Radical System
Hehong Yang,Yanqing Li,Peijun Li,Qian Liu
Advance Journal of Food Science and Technology , 2013,
Abstract: Antioxidant peptides have attracted much attention for potential application as natural food ingredients but the fate of them, as well as oxidized proteins in foods during processing, is still poorly understood. Physicochemical changes in antioxidant peptides hydrolysated from porcine plasma protein were discussed in a free hydroxyl radical-mediated oxidation system. Porcine Plasma Protein Hydrolysates (PPH) was prepared by hydrolyzing porcine plasma protein with Alcalase for 5 h at pH 8.0, 55°C. The content of carbonyl groups increased significantly at various degrees when PPH exposed to free radical-mediated oxidation for different time and different concentrations of H2O2, while total sulfhydryls, reactive sulfhydryls and free amines contents decreased. It was concluded that PPH played an antioxidant role in the radical-mediated oxidation system. This provides a potential way for antioxidation in food production.
Effect of glutamate receptor activation on free radical scavenger system in C6 glioma cultures
Jaspreet SINGH,Gurcharan KAUR
Journal of Neurological Sciences , 2004,
Abstract: Glutamate, a major excitatory neurotransmitter in CNS is also a potent neurotoxin and administration of micromolar concentrations of glutamate may lead to both immediate and delayed cell death. Apart from its well-established role in neurotoxicity, glutamate also exerts important neurotrophic activity. Pre-exposure to subtoxic concentration of NMDA has been shown to protect cerebellar neurons against subsequent toxic dose of glutamate or MPTP and this protection requires new protein synthesis. Until recently, the role of glial cells in integrity and degeneration of the central nervous system has not been well elucidated. Increasing evidence suggests an important role for astrocytes in neuronal survival and recovery following a variety of insults. The present study explored the protective effect of subtoxic dose of glutamate in retinoic acid differentiated C6 glioma cell cultures by studying the free radical scavenger system profile. The findings of the present study clearly demonstrate that subtoxic dose of glutamate in retinoic acid differentiated C6 glioma cell cultures leads to a robust antioxidant scavenger system with significant increase in the activities of copper zinc superoxide dismutase and glutathione peroxidase and higher levels of glutathione and increased survival rate of the cells. The data also reports astrocytic sprouting in response to a subtoxic dose of glutamate. Glial cells synthesize trophic factors essential for neuronal survival and selective glial sprouting during stress can directly effect the establishment of regeneration state in CNS.
Free Entropy  [PDF]
Dan Voiculescu
Mathematics , 2001,
Abstract: Free entropy is the analogue of entropy in free probability theory. The paper is a survey of free entropy, its applications to von Neumann algebras, connections to random matrix theory and a discussion of open problems.
The Peroxidase/H2O2 System as a Free Radical-Generating Agent for Gelling Maize Bran Arabinoxylans: Rheological and Structural Properties  [PDF]
Ana L. Martínez-López,Elizabeth Carvajal-Millan,Jaime Lizardi-Mendoza,Yolanda L. López-Franco,Agustín Rascón-Chu,Erika Salas-Mu?oz,Cécile Barron,Valérie Micard
Molecules , 2011, DOI: 10.3390/molecules16108410
Abstract: The oxidative gelation of maize bran arabinoxylans (MBAX) using a peroxidase/H2O2 system as a free radical-generating agent was investigated. The peroxidase/H2O2 system led to the formation of dimers and trimer of ferulic acid as covalent cross-link structures in the MBAX network. MBAX gels at 4% (w/v) presented a storage modulus of 180 Pa. The structural parameters of MBAX gels were calculated from swelling experiments. MBAX gels presented a molecular weight between two cross-links (Mc), a cross-linking density (ρc) and a mesh size (x) of 49 × 103 g/mol, 30 × 10?6 mol/cm3 and 193 nm, respectively.
Effect of glutamate receptor activation on free radical scavenger system in SH-SY5Y neuroblastoma cultures
Jaspreet SINGH,Gurcharan KAUR
Journal of Neurological Sciences , 2004,
Abstract: Glutamate, a major excitatory amino acid neurotransmitter is also an endogenous excitotoxin. Excessive levels of glutamate induce cellular damage to neurons. Apart from its well-established role in neurotoxicity, glutamate also exerts important neurotrophic activity. Glutamate receptors are also implicated in the remodeling of neuronal shunts related to learning and memory processes and activation of glutamate receptors, especially the NMDA subtype. Glutamate exposure and the subsequent influx of Ca2+ results in the production of reactive oxygen species (ROS) and the cell has an elaborate system of antioxidant enzymes and antioxidant substances to counteract ROS. The present study explored the role of subtoxic and toxic dose of glutamate in retinoic acid differentiated SH-SY5Y neuroblastoma cultures. Subtoxic dose of glutamate lead to an increased activity of the major antioxidant enzymes (catalase, CuZnSOD and GPx) and increased survival of the cells as assessed by dye exclusion method. The results of the present study clearly demonstrate that subtoxic dose of glutamate leads to robust antioxidant system and increased survival of SH-SY5Y neuroblastoma cells while toxic dose of glutamate lead to decreased viability in these cultures.
Topological Entropy of Free Product Automorphisms  [PDF]
N. P. Brown,K. Dykema,D. Shlyakhtenko
Mathematics , 2000,
Abstract: Using free probability constructions involving Cuntz-Pimsner C*-algebras we show that the topological entropy of the free product of two automorphisms is equal to the maximum of the individual entropies. As applications we show that general free shifts have entropy zero. We show that any nuclear C*-dynamical system admits an entropy preserving covariant embedding into the Cuntz algebra on infinitely many generators. It follows that any simple nuclear purely infinite C*-algebra admits an automorphism with any given value of entropy. As a final application we show that if two automorphisms satisfy a CNT-variational principle then so does their free product.
Remarks on free entropy dimension  [PDF]
Dimitri Shlyakhtenko
Mathematics , 2005,
Abstract: We prove a technical result, showing that the existence of a closable unbounded dual system in the sense of Voiculescu is equivalent to the finiteness of free Fisher information. This approach allows one to give a purely operator-algebraic proof of the computation of the non-microstates free entropy dimension for generators of groups carried out in an earlier joint work with I. Mineyev. The same technique also works for finite-dimensional algebras. We also show that Voiculescu's question of semi-continuity of free entropy dimension, as stated, admits a counterexample. We state a modified version of the question, which avoids the counterexample, but answering which in the affirmative would still imply the non-isomorphism of free group factors.
Steady State of a Dissipative Flow-Controlled System and the Maximum Entropy Production Principle  [PDF]
Robert K. Niven
Physics , 2009, DOI: 10.1103/PhysRevE.80.021113
Abstract: A theory to predict the steady state position of a dissipative, flow-controlled system, as defined by a control volume, is developed based on the Maximum Entropy (MaxEnt) principle of Jaynes, involving minimisation of a generalised free energy-like potential. The analysis provides a theoretical justification of a local, conditional form of the Maximum Entropy Production (MEP) principle, which successfully predicts the observable properties of many such systems. The analysis reveals a very different manifestation of the second law of thermodynamics in steady state flow systems, which {provides a driving force for} the formation of complex systems, including life.
Exact analytical expressions for entropy production and free energy  [PDF]
Mesfin Asfaw Taye
Physics , 2015,
Abstract: The nonequilibrium thermodynamics feature of a Brownian motor operating between two different heat baths is explored as a function of time $t$. Using the Gibbs entropy and Schnakenberg microscopic stochastic approach, we find exact closed form expressions for the free energy, the rate of entropy production and the rate of entropy flow from the system to the outside. We show that when the system is out of equilibrium, it constantly produces entropy and at the same time extract entropy out of the system. Its entropy production and extraction rates decrease in time and saturate to constant value. In long time limit, the rate of entropy production balances the rate of entropy extraction and at equilibrium both entropy production and extraction rates become zero. Furthermore, via the present model, not only many thermodynamic theories can be checked but also the wrong conclusions that are given due to lack of exact analytic expressions will be corrected.
The Renyi entropy as a "free entropy" for complex systems  [PDF]
A. G. Bashkirov
Physics , 2004,
Abstract: The Boltzmann entropy $S^{(B)}$ is true in the case of equal probability of all microstates of a system. In the opposite case it should be averaged over all microstates that gives rise to the Boltzmann--Shannon entropy (BSE). Maximum entropy principle (MEP) for the BSE leads to the Gibbs canonical distribution that is incompatible with power--low distributions typical for complex system. This brings up the question: Does the maximum of BSE correspond to an equilibrium (or steady) state of the complex system? Indeed, the equilibrium state of a thermodynamic system which exchange heat with a thermostat corresponds to maximum of Helmholtz free energy rather than to maximum of average energy, that is internal energy $U$. Following derivation of Helmholtz free energy the Renyi entropy is derived as a cumulant average of the Boltzmann entropy for systems which exchange an entropy with the thermostat. The application of MEP to the Renyi entropy gives rise to the Renyi distribution for an isolated system. It is investigated for a particular case of a power--law Hamiltonian. Both Lagrange parameters, $\alpha$ and $\beta$ can be eliminated. It is found that $\beta$ does not depend on a Renyi parameter $q$ and can be expressed in terms of an exponent $\kappa$ of the power--law Hamiltonian and $U$. The Renyi entropy for the resulting Renyi distribution reaches its maximal value at $q=1/(1+\kappa)$ that can be considered as the most probable value of $q$ when we have no additional information on behavior of the stochastic process. The Renyi distribution for such $q$ becomes a power--law distribution with the exponent $-(\kappa +1)$. Such a picture corresponds to some observed phenomena in complex systems.
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