What vibrations tell about proteins

1. Introduction 370 2. Infrared (IR) spectroscopy – general principles 372 2.1 Vibrations 372 2.2 Information that can be derived from the vibrational spectrum 372 2.3 Absorption of IR light 375 3. Protein IR absorption 376 3.1 Amino-acid side-chain absorption 376 3.2 Normal modes of the amide group 381 4. Interactions that shape the amide I band 382 4.1 Overview 382 4.2 Through-bond coupling 383 4.3 Hydrogen bonding 383 4.4 Transition dipole coupling (TDC) 383 5. The polarization and IR activity of amide I modes 387 5.1 The coupled oscillator system 387 5.2 Optically allowed transitions 388 5.3 The infinite parallel β-sheet 388 5.4 The infinite antiparallel β-sheet 389 5.5 The infinite α-helix 390 6.…