Radiationless energy transfer through a polypeptide chain

Electronic excitation spectra were measured on a donor‐acceptor pair which was separated by oligomers of L‐proline of gradually increasing lengths. The logarithmic plot of the transfer efficiency versus the donor‐acceptor separation, for (pro)n oligomers with n⩾5, yielded a slope of 5.8 ± 0.3 in good agreement with the theoretical value of 6, predicted by Forster. The above method is suggested as a tool for the estimation of distances between certain chromophoric groups, covalently bound to macromolecules. The use of any stereoregular polymer for calibrating a certain energy donor‐acceptor pair is discussed.