Myoglobin is a protein that binds to oxygen. Thus, O2 is the ligand for myoglobin. The equation below works the same way as equation 5.8. However, the O2 concentration is measured in partial pressures of the O2 in the air above the myoglobin solution. Thus, instead of Kd, we have P50 (the partial pressure of O2 at which 50% of the myoglobin has bound O2), and the O2 is measured in kilopascals (kPa).
Use the default values to draw a curve, clicking on New Plot. Change the P50 to 5, and draw a new curve. Manipulate the values for P50 and the range of O2 partial pressures until you are comfortable with how this equation works.
Up to 5 plots can be displayed at one time. The Clear button will remove all plots. To see P50 for each plot hit the Legend button. The Redraw button will refresh the graph. This is useful when the function domain (i.e., pO2) has been changed. To see the value of each plot at a given point, move your cursor to the desired location then click and hold.
Original material from Lehninger Principles of Biochemistry, 5a edición, de D. Nelson and M. Cox; 2009. ISBN: 0-7167-7108-X.
Dr. José Antonio Encinar. (IBMC-UMH)