Team:Valencia/StochasticApproach

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== '''Stochastic approach''' ==
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=='''Stochastic approach'''==
<span style="color:black; align:justify; font-size:10pt; font-family: Verdana">
<span style="color:black; align:justify; font-size:10pt; font-family: Verdana">
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<span style="color:black; align:justify; font-size:11pt; font-family:Verdana">At this point, we are going to use stochastic methods in order to study the activation/inactivation  of VDCCs. Unlike deterministic model, the voltage-dependent conductance for the calcium channels is now given by:
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At this point, we are going to use stochastic methods in order to study the activation/inactivation  of VDCCs. Unlike deterministic model, the voltage-dependent conductance for the calcium channels is now given by:
[[Image:Stoc1.jpg|center]]
[[Image:Stoc1.jpg|center]]
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<span style="color:black; align:justify; font-size:11pt; font-family:Verdana">Where the quotient <i>Q<sub>Ca</sub>/N<sub>Ca</sub></i> (number of calcium channels in open state / total number of calcium channels) means the activation variable and [[Image:Gca.jpg]] is the maximum calcium conductance. Each calcium channel is a Markov process with some voltage-dependent transition rates. The kinetic scheme is the following:
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Where the quotient <i>Q<sub>Ca</sub>/N<sub>Ca</sub></i> (number of calcium channels in open state / total number of calcium channels) means the activation variable and [[Image:Gca.jpg]] is the maximum calcium conductance. Each calcium channel is a Markov process with some voltage-dependent transition rates. The kinetic scheme is the following:
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<div align="justify" style="position:relative; top:-5px; left:-30px; width:600px"> [[Image:Markov3.jpg|700px]]</div>
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[[Image:Markov3.jpg|750px|center]]
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As it is shown, each calcium gate has four closed states (C<sub>i</sub>), five inactivated states (I<sub>i</sub>) and one open state (O<sub>5</sub>). Calcium influx occurs only when the gate is in the open state. k<sub>ij</sub> are the different transition rates (voltage-dependent in red and voltage-independent in black) between two states.
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Taking into account how voltage-dependent rates change in time and considering the probability of each transition (given by its transition rate), we have been able to select which transition happens and determine how many calcium gates are in open state (<i>Q<sub>Ca</sub></i>) at any time. Therefore, knowing the total number of calcium channels in the plasma membrane (<i>N<sub>Ca</sub></i> = 1000) we can calculate the activation variable for each time.
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<span style="color:black; align:justify; font-size:11pt; font-family:Verdana">As it is shown, each calcium gate has four closed states (C<sub>i</sub>), five inactivated states (I<sub>i</sub>) and one open state (O<sub>5</sub>). Calcium influx occurs only when the gate is in the open state. k<sub>ij</sub> are the different transition rates (voltage-dependent in red and voltage-independent in black) between two states.
 
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<span style="color:black; align:justify; font-size:11pt; font-family:Verdana">Taking into account how voltage-dependent rates change in time and considering the probability of each transition (given by its transition rate), we have been able to select which transition happens and determine how many calcium gates are in open state (<i>Q<sub>Ca</sub></i>) at any time. Therefore, knowing the total number of calcium channels in the plasma membrane (<i>N<sub>Ca</sub></i> = 1000) we can calculate the activation variable for each time.
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<div align="justify" style="position:relative; top:-5px; left:-30px; width:600px">[[Image:comparation.jpg|700px]]</div>
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[[Image:comparation.jpg|750px|center]]
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Revision as of 17:02, 19 October 2009



Stochastic approach

At this point, we are going to use stochastic methods in order to study the activation/inactivation of VDCCs. Unlike deterministic model, the voltage-dependent conductance for the calcium channels is now given by:

Stoc1.jpg

Where the quotient QCa/NCa (number of calcium channels in open state / total number of calcium channels) means the activation variable and Gca.jpg is the maximum calcium conductance. Each calcium channel is a Markov process with some voltage-dependent transition rates. The kinetic scheme is the following:

Markov3.jpg

As it is shown, each calcium gate has four closed states (Ci), five inactivated states (Ii) and one open state (O5). Calcium influx occurs only when the gate is in the open state. kij are the different transition rates (voltage-dependent in red and voltage-independent in black) between two states.

Taking into account how voltage-dependent rates change in time and considering the probability of each transition (given by its transition rate), we have been able to select which transition happens and determine how many calcium gates are in open state (QCa) at any time. Therefore, knowing the total number of calcium channels in the plasma membrane (NCa = 1000) we can calculate the activation variable for each time.


Comparation.jpg