795 research outputs found
The experimental study of the relation between the Alpha rhythm of the electroencephalogram and intelligence
During in the year 1808, Gall was assessing a person\u27s intellectual attributes by means of bumps in their heads. He held the opinion that an intellectual trait, as well as any other trait, would show the degree of its development by exerting a local pressure, pressing outward and finally appearing as a bump
Commentaire d\u27Arret: Le Procureur General du Canada c. Patrick Francis Ward
The following article is a case comment on Attorney General of Canada v. Patrick Francis Ward, a recent decision of the Federal Court of Appeal. A summary of the facts and issues involved will be provided, followed by an analysis of the majority and dissenting judgments. Particular emphasis will be directed toward the definition of Convention refugee and how the majority decision has dealt with it. This will be contrasted with previous doctrine and jurisprudence. Finally certain problematic aspects of both the majority and dissenting judgments will be examined as well as the possible implications of this case for future refugee claimants in Canada
Commentaire d\u27Arret: Le Procureur General du Canada c. Patrick Francis Ward
The following article is a case comment on Attorney General of Canada v. Patrick Francis Ward, a recent decision of the Federal Court of Appeal. A summary of the facts and issues involved will be provided, followed by an analysis of the majority and dissenting judgments. Particular emphasis will be directed toward the definition of Convention refugee and how the majority decision has dealt with it. This will be contrasted with previous doctrine and jurisprudence. Finally certain problematic aspects of both the majority and dissenting judgments will be examined as well as the possible implications of this case for future refugee claimants in Canada
Thermodynamic and Kinetic Analysis of Sensitivity Amplification in Biological Signal Transduction
Based on a thermodynamic analysis of the kinetic model for the protein
phosphorylation-dephosphorylation cycle, we study the ATP (or GTP) energy
utilization of this ubiquitous biological signal transduction process. It is
shown that the free energy from hydrolysis inside cells,
(phosphorylation potential), controls the amplification and sensitivity of the
switch-like cellular module; the response coefficient of the sensitivity
amplification approaches the optimal 1 and the Hill coefficient increases with
increasing . We discover that zero-order ultrasensitivity is
mathematically equivalent to allosteric cooperativity. Furthermore, we show
that the high amplification in ultrasensitivity is mechanistically related to
the proofreading kinetics for protein biosynthesis. Both utilize multiple
kinetic cycles in time to gain temporal cooperativity, in contrast to
allosteric cooperativity that utilizes multiple subunits in a protein.Comment: 19 pages, 7 figure
Thresholds, long delays and stability from generalized allosteric effect in protein networks
Post-transductional modifications tune the functions of proteins and regulate
the collective dynamics of biochemical networks that determine how cells
respond to environmental signals. For example, protein phosphorylation and
nitrosylation are well-known to play a pivotal role in the intracellular
transduction of activation and death signals. A protein can have multiple sites
where chemical groups can reversibly attach in processes such as
phosphorylation or nitrosylation. A microscopic description of these processes
must take into account the intrinsic probabilistic nature of the underlying
reactions. We apply combinatorial considerations to standard enzyme kinetics
and in this way we extend to the dynamic regime a simplified version of the
traditional models on the allosteric regulation of protein functions. We link a
generic modification chain to a downstream Michaelis-Menten enzymatic reaction
and we demonstrate numerically that this accounts both for thresholds and long
time delays in the conversion of the substrate by the enzyme. The proposed
mechanism is stable and robust and the higher the number of modification sites,
the greater the stability. We show that a high number of modification sites
converts a fast reaction into a slow process, and the slowing down depends on
the number of sites and may span many orders of magnitude; in this way
multisite modification of proteins stands out as a general mechanism that
allows the transfer of information from the very short time scales of enzyme
reactions (milliseconds) to the long time scale of cell response (hours).Comment: 5 figures, submitted to Physica
Assessment of oxidative metabolism
Oxidative metabolism is one of the central physiological processes that regulate multiple functions in a cell including cell death and survival, proliferation, gene transcription, and protein modification. There are multitudes of techniques that are used to evaluate oxidative activity. Here, we summarize how to measure oxidative activity by flow cytometry. This versatile technique allows the evaluation of the level of oxidative activity within heterogeneous populations of cells and in cell culture. Flow cytometry is a quick method that yields highly reproducible results with small sample volumes. Therefore, it is an ideal technique for evaluating changes in oxidative activity in samples from mice
Validation of protein carbonyl measurement:a multi-centre study
Protein carbonyls are widely analysed as a measure of protein oxidation. Several different methods exist for their determination. A previous study had described orders of magnitude variance that existed when protein carbonyls were analysed in a single laboratory by ELISA using different commercial kits. We have further explored the potential causes of variance in carbonyl analysis in a ring study. A soluble protein fraction was prepared from rat liver and exposed to 0, 5 and 15 min of UV irradiation. Lyophilised preparations were distributed to six different laboratories that routinely undertook protein carbonyl analysis across Europe. ELISA and Western blotting techniques detected an increase in protein carbonyl formation between 0 and 5 min of UV irradiation irrespective of method used. After irradiation for 15 min, less oxidation was detected by half of the laboratories than after 5 min irradiation. Three of the four ELISA carbonyl results fell within 95% confidence intervals. Likely errors in calculating absolute carbonyl values may be attributed to differences in standardisation. Out of up to 88 proteins identified as containing carbonyl groups after tryptic cleavage of irradiated and control liver proteins, only seven were common in all three liver preparations. Lysine and arginine residues modified by carbonyls are likely to be resistant to tryptic proteolysis. Use of a cocktail of proteases may increase the recovery of oxidised peptides. In conclusion, standardisation is critical for carbonyl analysis and heavily oxidised proteins may not be effectively analysed by any existing technique
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