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MbO2

Model for Oxygen binding to myoglobin, single site first order binding.

Model number: 0026

Description

 Binding of a ligand is a function of the affinity of 
the site for the ligand, The ratio of the off-rate, k_1, to the on-rate, k1, is the 
Kd = k_1/k1. The binding of oxygen O2 to myoglobin Mb is given by the reaction:
                   k1
                  --->
          O2 + Mb <--- MbO2 , where one O2 molecule binds to the site on Mb.
                   k_1
To translate from physiological measures of partial pressure of O2 in mmHg,
the solubility of O2 in water for the particular temperature has to be used,
alphO2. The PO2 at 50% saturation, i.e. 50% of Mb bound to O2, is called p50Mb, 
and is the PO2 at which the molar concentration of O2 equals Kd.
    In this model, the PO2 is raised gradually in order to run it through a 
wide range of concentrations from well below Kd to well above Kd. If the rate
of binding is slow, the binding will not be a t equilibrium, and saturation 
will be below the equilibrium level when PO2 is rising fast.
Change the "rateO2" at which the pO2 is raised: at low on-rates, k1, the SMb, 
the myoglobin saturation, will lag behind the curve for instantaneous equilibration, SMbeq.
 SMbeq = 1/(1+ Kd / pO2),  where Kd is the dissociation constant.

Equations

Schenkman KA, Marble DR, Burns DH, and Feigl EO: Myoglobin oxygen 
 dissociation by multiwavelength spectroscopy. J Appl Physiol 82: 86-92, 1997.

Schenkman KA, Beard DA, Ciesielski WA, and Feigl EO: Comparison of buffer 
 and red blood cell perfusion of guinea pig heart oxygenation. 
 Am J Physiol Heart Circ Physiol 285: H1819-H1825, 2003.

Schenkman KA: Cardiac performance as a function of intracellular oxygen 
 tension in buffer-perfused hearts. Am J Physiol Heart Circ Physiol 
 281: H2463-H2472, 2001.