. Biophysical science. Biophysics. COOH. (b) Figure II. Kendrew's model of myoglobin, (a) General shape of the polypeptide chain. The gray area is the heme group. The round dark atom represents a heavy atom attached for isomorphous replacements. The tilt of the heme group is incorrect, (b) Course of the polypeptide chain as deter- mined by a three-dimensional fourier synthesis with 2 A resolu- tion. After J. C. Kendrew, et al., "Structure of Myoglobin," Nature 185: 422 (1960). into one globular molecule, it must be bent and twisted at various corners. Where this occurs, the a-helical
. Biophysical science. Biophysics. COOH. (b) Figure II. Kendrew's model of myoglobin, (a) General shape of the polypeptide chain. The gray area is the heme group. The round dark atom represents a heavy atom attached for isomorphous replacements. The tilt of the heme group is incorrect, (b) Course of the polypeptide chain as deter- mined by a three-dimensional fourier synthesis with 2 A resolu- tion. After J. C. Kendrew, et al., "Structure of Myoglobin," Nature 185: 422 (1960). into one globular molecule, it must be bent and twisted at various corners. Where this occurs, the a-helical form is lost usually for 3 or 4 amino acid residues. There is also one group of about 13-18 amino acid residues not in the form of an a-helix. Figure 11a shows a photograph of Kendrew's model of myoglobin, built to represent the structure which would give the 400 diffraction spots used. In addition, electron spin resonance measurements were used to locate the iron atoms in the heme group (see Chapter 28). However, the latter data were misinterpreted so that the heme group was tilted at the wrong angle. Figure lib, for comparison, shows the form of the polypeptide chain revealed by the 9,600 diffraction spot study. Although not illustrated in the figure, all of the chains are shown by the latter study to be hollow, cylindrical tubes of the form. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ackerman, Eugene, 1920-. Englewood Cliffs, N. J. , Prentice-Hall
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