Cyclol

The cyclol hypothesis is the first structural model of a folded, globular protein. It was developed by Dorothy Wrinch in the late 1930s. The hypothesis assumes that two peptide groups can be crosslinked by a cyclol reaction. It also assumes that globular proteins have a tertiary structure corresponding to Platonic solids.

About Cyclol in brief

The cyclol hypothesis is the first structural model of a folded, globular protein. It was developed by Dorothy Wrinch in the late 1930s and was based on three assumptions. The hypothesis assumes that two peptide groups can be crosslinked by a cyclol reaction. It also assumes that globular proteins have a tertiary structure corresponding to Platonic solids and semiregular polyhedra formed of cyclol fabrics with no free edges. These cyclol molecules and fabrics have never been observed. The cyclol model stimulated many scientists to research questions in protein structure and chemistry, and was a precursor of the more accurate models hypothesized for the DNA double helix and protein secondary structure. The most accepted hypothesis was that proteins are linear polypeptides, i.e. unbranched polymers of amino acids linked by peptide bonds. However, a typical protein is remarkably long—hundreds of amino-acid residues—and several distinguished scientists were unsure whether such long, linear macromolecules could be stable in solution. The process of protein denaturation had been discovered in 1910 by Harriette Chick and Charles Martin, but its nature was still mysterious. In 1929, Hsien Wu hypothesized correctly that denaturation corresponded to a conformational change that resulted in the exposure of side chains to solvent. In 1936, Mirsky Linus Pauling advanced independently to a purely a purely chemical change that led to a protein structure that was considered a possibility until the 1950s. In 1934, Dorothy Crowfoot Hodgkin solved the small protein structure of the insulin X-ray crystallography, although the structure of other proteins and other proteins were not solved on the same basis until the 1940s.

However even the smallest proteins have their structure determined over 1000 atoms, which makes their structure far more complex. The structure of proteins was not solved until 1950s, although that was not taken on the basis of crystallographic data on the small proteins, such as insulin and other salt crystals, and other complex molecules such as salt crystals to cholesterol. The protein structure was still under debate at that time, and it was difficult to determine the exact molecular weight and number of amino amino acids in a protein. In the mid-1930s, analytical ultracentrifugation studies by Theodor Svedberg had shown that proteins had a well-defined chemical structure, and were not aggregations of small molecules. The same studies appeared to show that a change in solution conditions could cause a protein to disassemble into small subunits, now known as achange in quaternary structure. As clarified by Linderstrøm-Lang, these proteolysis data showed that denatured proteins were polypepides, but no data had yet been obtained about theructure of folded proteins; thus, denaturation could involve a chemical change that converted folded proteins into polypeps. This led to the creation of the protein structure hypothesis. In 1950, scientists could not exclude the possibility that denaturation was a possibility.