fig=plt.figure()
ax=fig.add_subplot(111)
ax.plot(np.log10(x+1e-2),y,'bo')
params,params_cov=optimize.curve_fit(gfp_fit_v1,x,y,p0=[92000.0,20.0,0.0,0.0],bounds=([0,0,0,0],[np.inf,np.inf,np.inf,y[-1]]))
ax.plot(np.log10(x+1e-2),gfp_fit_v1(x,params[0],params[1],params[2],params[3]),ls='--')
plt.show()
print params