Team:Paris/Modeling/Programs
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==Hill Functions== | ==Hill Functions== | ||
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+ | The previous system of complexation applied in particular to the association of the Promoters (''P'') and its Transcription Factor (''TF''). | ||
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+ | Because the promoters on a "low copy plasmid" exists in the cell in ten exemplaries, in contrary to a protein, which, as long as it is produced (even weakly) exists in thousands of exemplaries, we can the quantities of ''TF'' and ''P'' are different by several orders of magnitude. Then, with the previous notations, if ''A'', ''B'' and ''C'' stands respectively for ''TF'', ''P'' and the complex ''TF_-_P'', we will get | ||
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+ | <center> [[Images:approxhill.jpg]] </center> | ||
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+ | that we can easily solve with : | ||
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+ | <center> [[Images:justhill.jpg]] </center> | ||
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+ | Depending to the order ''' ''n'' '' (also called ''cooperativity'', because it correponds to the possibilities of the transcription factor to binds in a group on the promoter), this function is a ''sigmoïd'', known as the ''Hill function''. The parameter ''' ''K'' ''', called ''activation constant'', is often replaced in the previous expression by the following notation | ||
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+ | <center> [[Images:changeK]] </center> | ||
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+ | It simplify the manipulations of the expression ; we can notice that ''' ''K'' ''' represents now the amount of ''TF'' needed to get half of the total ''P'' bound. | ||
==Finding Parameters== | ==Finding Parameters== |
Revision as of 11:34, 16 September 2008
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