Structure Determination of Peptides by simple 2D NMR Spectroscopy

Determining the three dimensional structure of biological molecules is an important step towards understanding the structure-function relationship. Structure determination of peptides or proteins is based on the Nuclear Overhauser effect (NOE) observed between two protons that may be less than 5- 6 Å apart (through space). The large number of protons present in a protein makes it almost impossible to assign them by a 1D spectrum. 2D NMR spectrum gives correlations between two atoms that may be separated through bond (TOCSY, HSQC, etc) or through space (NOESY). The TOCSY and HSQC spectra along with NOESY spectrum are used for sequential resonance assignment. The peak intensities in the NOESY spectrum also depend on the distance between the two protons, thereby giving important structural information. A brief introduction about the basic principle and Instrumentation of NMR followed by the important steps involved in determining the structure of peptides will be discussed in detail.