Biochemistry the Polypeptide Chain Configuration in Hemoglobin

Biochemistry The Polypeptide Chain Configuration in Hemoglobin and other Globular Proteins By Linus Pauling and Robert B. Corey (1951) The article named above describes a continuation in the study of hydrogenbonded planar-amide configurations of polypeptide chains. It also discusses evidence on the possibility of the existence of such chains in fibrous proteins, and in molecules of globular proteins.

The article first notes that globular patterns such as ovalbumin, can "on denaturation be converted into a form showing the B-keratin x-ray pattern." Because of such reactions, there is an observance of the fiber axis distance, which is the same as that of ft keratin, which the authors claim has already been suggested in a previous paper. For this reason as well, the authors here claim that the same structure (observed above) should be represented by denatured proteins, with some modifications, which they claim is quite an important discovery.

Significant data on this subject is subsequently discussed, especially that relating to the structure of globular proteins, such as those found in carbonmonoxyhemoglobin. The reason this data is mentioned is to provide support for the above theory, namely and specifically to "provide some support for the idea that the 3.7-residue helix is a principal feature of the structure of the protein." The authors also quote heavily from previous studies both in order to bolster their own as well as to indicate the variances in the molecules studied.

For instance, they point to Perutz to indicate the dimensions of a hemoglobin molecule and how these an relate to helical configurations in a keratin molecule. This is important, because hemoglobin could thus predict that molecules with such a specific helical configuration, according to the authors, "would be spaced about 11 A apart (from center to center), in agreement with Perutz's conclusion that the rods in hemoglobin are about 10.5 A apart.

(A calculation of this sort at once eliminates the 5.1-residue helix, for which the predicted average spacing of the rods is 14.