Cyclol theory

Globular Proteins. Despite their importance, globular proteins are not as thoroughly studied as fibrous ones. They include, for example, albumin and hemoglobin. There have been some suggestions which, with one exception, have involved H bonds. This exception, Wrinch s cyclol theory (see, for example, 2202-2204), is of only p2issing interest, but its lack of conformity witK tha observed H bonding (as indicated by IR spectra) was one factor in its rejection. See 1602 for a criticism of the cyclol theory. 

It has been recognized that energy relations present some difficulty for the cyclol theory (although the seriousness of the difficulty seems not to have been appreciated), and various suggestions have been made in the attempt to avoid the difficulty. In her latest communication Wrinch writes, The stability of the globular pro-... 

The Cyclol Theory.—Protein molecules are composed largely, if not entirely, of amino acid residues, and contain many — NH—CO— linkages but few free — NHg groups, apart from those found in side-chains. The general uniformity of the protein type su ests a uniformity of general structure. Many proteins are easily denatured, and when spread on a suitable surface spontaneously form insoluble monolayers. 

To put an end to what he saw as a distraction from more valuable lines of inquiry, Pauling and fellow protein researcher Carl Niemann in 1939 published a paper marshaling all the chemical evidence in favor of their chain theory of protein structure and against Wrinch s arguments. Its impact was devastating. After it appeared, no one would take Wrinch s cyclols seriously again. 

Globular proteins in alkaline solution tend to aggregate. Protein ciystals show a high trigonal symmetry. These and other observations have led Wrinch (1936) to discard the peptide chain theory in favour of a structure in which the unit is a cyclol made up of six amino acid residues. Each cyclol is further stabilised by cro union between a peptide nitrogen and an adjacent carbon atom, the result being called a cyclol 6, which reoccurs throughout the protein fabric. 

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