SOLUTION CONFORMATIONS OF PENTA AND HEPTAPEPTIDES CONTAINING REPETITIVE α-AMINOISOBUTYRYL-L-ALANYL AND α-AMINOISOBUTYRYL-L-VALYL SEQUENCES

Article abstract of DOI:10.1016/S0040-4020(01)91984-2

The presence of folded solution conformations in the peptides Boc-Ala-(Aib-Ala)2-OMe, Boc-Val-(Aib-Val)2-OMe, Boc-Ala-(Aib-Ala)3-OMe and Boc-Val-(Aib-Val)3-OMe has been established by 270 MHz 1H NMR.Intramolecularly H-bonded NH groups have been identified using temperature and solvent dependence of NH chemical shifts and paramagnetic radical induced broadening of NH resonances.Both pentapeptides adopt 3₁₀ helical conformations possessing 3 intramolecular H-bonds in CDCl3 and (CD3)2SO.The heptapeptides favour helical structures with 5 H-bonds in CDCl3.In(CD3)2SO only 4 H-bonds are readily detected.