Cyclol
Sign in to savethumb|350px|right|Figure 1: In the classic cyclol reaction, two peptide groups are linked by a N-C' bond, converting the carbonyl oxygen into a hydroxyl group. Although this reaction occurs in a few cyclic peptides, it is disfavored by Thermodynamic free energy|free energy, mainly because it eliminates the [[resonance stabilization of the peptide bond. This reaction was the basis of Dorothy Wrinch's cyclol model of proteins.]]
Article
11 sectionsContents
- Historical context
- Basic theory
- Stabilizing energies
- Steric complementarity
- Hybrid models
- Space-enclosing fabrics
- Predicted protein structures
- Implausibility of the model
- Partial redemption
- References
- Further reading
thumb|350px|right|Figure 1: In the classic cyclol reaction, two peptide groups are linked by a N-C' bond, converting the carbonyl oxygen into a hydroxyl group. Although this reaction occurs in a few cyclic peptides, it is disfavored by Thermodynamic free energy|free energy, mainly because it eliminates the [[resonance stabilization of the peptide bond. This reaction was the basis of Dorothy Wrinch's cyclol model of proteins.]]
The cyclol hypothesis is the now discredited first structural model of a folded, globular protein, formulated in the 1930s. It was based on the cyclol reaction of peptide bonds proposed by physicist Charles Frank in 1936, in which two peptide groups are chemically crosslinked. These crosslinks are covalent analogs of the non-covalent hydrogen bonds between peptide groups and have been observed in rare cases, such as the ergopeptides.