A Molecular Model of Myoglobin Constructed for Use as a Teaching Aid One of the primary responsibilities of a department of biophysics in a medical school is the teaching of basic science to medical students and to others interested in medical science problems. Since it is often difficult to convey ideas concerning the relationships which exist between the structure and the function of a biological molecule, it was decided that a maleculer model of myoglobin would be helpful in discussing the molecular differences which exist between normal and sickle cell hemoglobin in the deoxygenated state. A model based on a scale of 2 cm = 1 A was constructed1 from shl-in. brass rod. The cwrdinates of the non-hydrogen atoms and the dihedral angles were kindly furnished by Dr. John K e n d r e ~ The . ~ alpha carhonr were color coded for easv identification and the model was "
Using the model and slides taken from Dickerson and Geis's book3 it was possible to demonstrate to students: (1)the location of the oxygen molecule; (2) the position of the histidine groups nearest the iron atom; (3) the position of the hydrophobic and hydrophilic regions of the moleculc; (4) the importance of the hydrophobic cage in which the heme group resides; (5) the changes which take place upon deoxygenation; (6) the hydrophobicity of certain portions of the surface of the molecule after deoxygenation. Using the theory of Murayamas to show how the N terminal group of the beta chains might be buried, the plausibility of the chain formation of hemoglobin S due to the increase in the hydrophobicity of certain portions of the surface upon deoxygenation was demonstrated. This model with accompanying discussion sheets was displayed, after being used in lectures, for several weeks in one of the laboratories used by medical students and then in the biochemistry graduate student laboratory in order that the students could study the model at their leisure and thus gain understanding of the action of hemoglobin, the difference between hemoglobin S and normal hemoglobin, and some idea of the conformational changes which may take place in proteins as their environment changes. We wish to thank Mr. RaymondRuffinfar his aid in constructing the model. 'Construction details may he obtained from the authors. Kendrew, J., personal communication. 3Dickerson, R. E. and Geis, I., in "The Structure and Action of Proteins," Harper and Row, New York, 1969, p. 44. 'Murayama, M., Olson, R. A., and Jenning, W. H., Bioehem. Biophys. Acto, 94,194, (1965). Department of Biophysics Virginia Commonwealth University Richmond, 23298
628 /Journal of Chemical Education
William E. Keefe Donna-Beth Howe
