Abstract:  As their names suggest, membrane proteins reside in the membranes of cells. They form an important class of proteins, because they have several important biological functions like regulation of flow of ions through the membrane, anchoring enzymes, regulating the shape of cells, etc. As the functionality of these proteins is largely due to its three-dimensional structure in space, it is important to obtain high-resolution structural information of these proteins in their native lipid environment. However, due to several experimental restrictions presented by this lipid environment, few membrane protein structures have been reported so far. In the last few years, nuclear magnetic resonance (NMR) has emerged as an alternate experimental technique in determining the structures of these proteins in the membrane environment. Structural information in NMR comes indirectly from measuring inter-nuclear interactions between different nuclei in the protein. This yields distance information between the nuclei, and in some cleverly designed experiments, orientation information of the inter-nuclear vector with respect to a fixed magnetic field. Mathematically, obtaining information in NMR can be described in terms of solving inverse problems involving the Schrodinger equation. We will describe the theory of some recent experiments which can provide new structural information for proteins.