THE MECHANISM OF a-HELIX FORMATION BY PEPTIDES

HISTORY ......... .............................................................................................................. 97 A Thermodynamic Model of a-Helix Formation ....................................................... 97 Statistical Mechanical Models of a-Helix Formation................................................ 98 Tests of Helix-Coil Theory and Values for Parameters ............................................. 99 Host-Guest Studies ................................................................................................... 101 HELIX FORMATION BY SEQUENCES FROM PROTEINS......................................................... 102 Early Studies....... ............................... .... ............................................. ....... .... .......... 102 pH Dependence of Helix Formation by C Peptide..................................................... 102 Helix Stop in S Peptide ............................................................................................ 103 Charge-Helix Dipole Interactions ............................................................................. 103 Phe8··· His12+ Interaction in C Peptide .................................................................. 104 Glu2-'" ArgJO+ Interaction in C Peptide................................................................ 105 Studies of Helix Propensities in C Peptide ....................... ........... ...... ........................ 105 The Nascent Helix.................................................................................................... 106