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  <title>A Model For Circadian PER Oscillations In Drosophila</title>
  <author>
    <firstname>Catherine</firstname>
          <surname>Lloyd</surname>
    <affiliation>
      <shortaffil>Auckland Bioengineering Institute, The University of Auckland</shortaffil>
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  <section id="sec_status">
    <title>Model Status</title>
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               This CellML model runs in both OpenCell and COR to reproduce Figure 2 in the original published paper by Goldbeter in the 1995 model 'A Model For Circadian PER Oscillations In Drosophila', as referenced as the gerard_gonze_goldbeter_2009 model .  The units have been checked and they are consistent.
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<title>Model Structure</title>

<para>
ABSTRACT: The mechanism of circadian oscillations in the period protein (PER) in Drosophila is investigated by means of a theoretical model. Taking into account recent experimental observations, the model for the circadian clock is based on multiple phosphorylation of PER and on the negative feedback exerted by PER on the transcription of the period (per) gene. This minimal biochemical model provides a molecular basis for circadian oscillations of the limit cycle type. During oscillations, the peak in per mRNA precedes by several hours the peak in total PER protein. The results support the view that multiple PER phosphorylation introduces times delays which strengthen the capability of negative feedback to produce oscillations. The analysis shows that the rhythm only occurs in a range bounded by two critical values of the maximum rate of PER degradation. A similar result is obtained with respect to the rate of PER transport into the nucleus. The results suggest a tentative explanation for the altered period of per mutants, in terms of variations in the rate of PER degradation.
</para>

<para>
The original paper reference is cited below:
</para>

<para>
A Model for Circadian Oscillations in the Drosophila Period Protein (PER), Albert Goldbeter, 1995, <emphasis>Proceedings of the Royal Society of London, Series B, Biological Sciences</emphasis>, 261, 319-324.  <ulink url="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&amp;db=PubMed&amp;list_uids=8587874&amp;dopt=Abstract">PubMed ID: 8587874</ulink>
</para>

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<caption>Schematic diagram of the model for circadian oscillations in PER protein and <emphasis>per</emphasis> mRNA.</caption>
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xml:lang="en">c.lloyd@auckland.ac.nz</rdf:value></rdf:Description><rdf:Description rdf:about="rdf:#ed2f1fc4-8bfd-46f0-a269-416512bddcdc"><FN xmlns="http://www.w3.org/2001/vcard-rdf/3.0#" xml:lang="en">Catherine Lloyd</FN></rdf:Description><rdf:Description rdf:about="rdf:#513b0ea2-4294-40ef-b637-0a4a4f7e30b1"><FN xmlns="http://www.w3.org/2001/vcard-rdf/3.0#" xml:lang="en"></FN></rdf:Description><rdf:Description rdf:about="rdf:#86de7cde-102d-48f8-8bfe-1896008703b9"><rdf:value xml:lang="en">added cmeta:id's to variables, changed documentation</rdf:value><modified xmlns="http://purl.org/dc/terms/"><rdf:Description rdf:about="rdf:#f5b66493-dd69-4452-80c3-b6dd27cee9c4"/></modified><cmeta:modifier><rdf:Description rdf:about="rdf:#38d906e3-f162-4f96-982c-f2039aeae211"/></cmeta:modifier></rdf:Description><rdf:Description rdf:nodeID="n1"><rdf:type><rdf:Description rdf:about="http://www.w3.org/1999/02/22-rdf-syntax-ns#Bag"/></rdf:type><rdf:_1 xml:lang="en">cell cycle</rdf:_1><rdf:_4 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xml:lang="en">keyword</subject_type></rdf:Description><rdf:Description rdf:about="rdf:#703537de-0aeb-4f3e-bda9-dbfb52e0d349"><creator xmlns="http://purl.org/dc/elements/1.1/"><rdf:Description rdf:about="rdf:#ed2f1fc4-8bfd-46f0-a269-416512bddcdc"/></creator><rdf:value xml:lang="en">This is the CellML description of Albert Goldbeter's 1995 model for circadian oscillations in the Drosophila period protein (PER).</rdf:value></rdf:Description><rdf:Description rdf:about="rdf:#b1a09ab6-b20b-4bf1-b653-d5961630981d"><rdf:type><rdf:Description rdf:about="http://www.cellml.org/bqs/1.0#Person"/></rdf:type><N xmlns="http://www.w3.org/2001/vcard-rdf/3.0#"><rdf:Description rdf:about="rdf:#231a0fec-5ff9-4296-8921-56dded0a6134"/></N></rdf:Description><rdf:Description rdf:about="rdf:#cd5bc920-4ac1-4aa8-b8b3-021f33e21d2f"><rdf:type><rdf:Description rdf:about="http://www.w3.org/1999/02/22-rdf-syntax-ns#Seq"/></rdf:type><rdf:_1><rdf:Description 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xml:lang="en">P0</title><alternative xmlns="http://purl.org/dc/terms/" xml:lang="en">PER protein</alternative></rdf:Description><rdf:Description rdf:about="rdf:#231a0fec-5ff9-4296-8921-56dded0a6134"><Family xmlns="http://www.w3.org/2001/vcard-rdf/3.0#" xml:lang="en">Goldbeter</Family><Given xmlns="http://www.w3.org/2001/vcard-rdf/3.0#" xml:lang="en">Albert</Given></rdf:Description><rdf:Description rdf:about="#P1"><title xmlns="http://purl.org/dc/elements/1.1/" xml:lang="en">P1</title><alternative xmlns="http://purl.org/dc/terms/" xml:lang="en">phosphorylated PER protein</alternative></rdf:Description><rdf:Description rdf:about="rdf:#38d906e3-f162-4f96-982c-f2039aeae211"><N xmlns="http://www.w3.org/2001/vcard-rdf/3.0#"><rdf:Description rdf:about="rdf:#d39e3397-9918-4486-824c-de80ec3b7d33"/></N></rdf:Description><rdf:Description rdf:about="rdf:#b8e2ae00-3ec9-4594-8225-402b99d22338"><W3CDTF xmlns="http://purl.org/dc/terms/" 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xml:lang="en">Lawson</Family><Given xmlns="http://www.w3.org/2001/vcard-rdf/3.0#" xml:lang="en">James</Given><Other xmlns="http://www.w3.org/2001/vcard-rdf/3.0#" xml:lang="en">Richard</Other></rdf:Description><rdf:Description rdf:about="rdf:#e7066ccb-da27-4fb2-87ff-342ca9f1170b"><W3CDTF xmlns="http://purl.org/dc/terms/" xml:lang="en">2003-10-30T00:00:00+00:00</W3CDTF></rdf:Description></rdf:RDF></model>