%   Figure 4.11, comparison of open probabililty for IP3 receptor 
%        for different concentrations of IP3
%   Carol Lucas

d1=0.027; d2=0.94; d3=0.2;
k12=20;k21=1.64;k15=400;k51=52;
k85=0.21;
K1=k51/k15;
K2=k21/k12;

c=(.001:.001:1000);

IPRAY=[.5 .75 1];

figure(1);clf;

for k=1:3
    IP3=IPRAY(k);
    yinf=(d1+k85*IP3)./(d1+k85*IP3+d2*d3*c+IP3*d3*c);
    x03(k,:)=((IP3*yinf.*c)./((K1+IP3)*(K2+c))).^3;  %% puts each graph in a row
    
end

plot(log10(c),x03);xlabel('log[Ca2+]');ylabel('Popen');