Global conformation

DG was primarily developed as a mathematical tool for obtaining spahal structures when pairwise distance information is given [118]. The DG method does not use any classical force fields. Thus, the conformational energy of a molecule is neglected and all 3D structures which are compatible with the distance restraints are presented. Nowadays, it is often used in the determination of 3D structures of small and medium-sized organic molecules. Gompared to force field-based methods, DG is a fast computational technique in order to scan the global conformational space. To get optimized structures, DG mostly has to be followed by various molecular dynamic simulation. 

The CP MAS NMR spectroscopy has been also extensively used for studies of proteins containing retinylidene chromophore like proteorhodopsin or bacteriorhodopsin. Bacteriorhodopsin is a protein component of purple membrane of Halobacterium salinarium.71 7 This protein contains 248 amino acids residues, forming a 7-helix bundle and a retinal chromophore covalently bound to Lys-216 via a Schiff base linkage. It is a light-driven proton pump that translocates protons from the inside to the outside of the cell. After photoisomerization of retinal, the reaction cycle is described by several intermediate states (J, K, L, M, N, O). Between L and M intermediate states, a proton transfer takes place from the protonated Schiff base to the anionic Asp85 at the central part of the protein. In the M and/or N intermediate states, the global conformational changes of the protein backbone take place. 

Correlation Between Global Conformation and Optical Characteristics of Polysilanes... 

As shown in Figure 4.17, these absorption properties mainly depend on the polysilane global conformation (from a shrunk random coil to an extended... 

Solution Studies Global Conformation, Solvato- and Thermochromism 591... 

Also important to the correlation between global conformation and optoelectronic properties are the investigations of single molecules of polysilanes by AFM, by which molecules could be directly imaged, and their contour lengths, diameters, and general shapes studied. These studies are dealt with in Section 3.11.5.3. 

X-Ray diffraction data give the atomic coordinates and thereby the conformations of molecules in the crystalline phase. If many structures of a given type are known, which unfortunately is rarely the case for medium rings, it is likely that an excellent picture of the global conformational energy minimum will be obtained as lattice effects should be more or less random. 

---