Team:Paris/Modeling/Others prog

complexes

function complexes = complexes(x,y,K,n)
% amount of complexes n*x + y = x_-_y in function of x, y
 
% x, y = initial amounts of binding molecules
% K = dissociation constant
% n = stoechiometric coefficient of x
 
syms z; % to treat z as a symbolic variable
Eqn = ( ( x - n*z )^n )*( y - z ) - K*z; % to define the equation in whose
                                          % the amount of complexes is a root  
 
S = eval(solve( Eqn, 'z' )); % the vector of the roots
 
Index = find ((0 < S) & (n*S < x) & (S < y) & (imag(S) == 0)); % determine  
                                                                % which
                                                                % root is  
                                                                % acceptable
 
complexes = S(Index(1)); % the result
 
end

hill

function compl = hill(x,K,n)
% complexation nx + Y = x_-_Y when x is in large excess :
% gives the ratio (x_-_Y)/(Ytotal) in function of x
 
% x = molecule that binds to Y
% K^n = dissociation constant
% n = stoechiometric coefficient of x ; also known as 'cooperativity'
 
compl = x^n/(K^n + x^n);
 
end

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