Conformation, stacked

A bisignate spectrum is characteristic of exciton coupling between identical chromophores on one molecule (144), an impossibility with the 1 1 heme-hemopexin complex. Bisignate CD spectra have been observed with bilirnbin-albnmin however, bilirubin, nnlike the planar molecnle heme, can adopt an extended, helical stacked conformation... 

The red component of the dimer Soret band is ascribed to a twisted conformer "A" and the blue component to a stacked conformer "B". Computer calculations can predict two conformations A and B with dihedral angles of the porphyrin moieties of 80 and 56 ,respectively. S2 emission was detected for 0,0 -C (TPPZn)2 and o,o -C (TPP-... 

To further characterize the mobility of the IRE loop, time-resolved isotropic fluorescence emission decay components of the IRE RNAs were determined as a function of temperature. Some details of the measurements and data assessment will be necessary here to appreciate both the utility of the information and caveats about its literal interpretation. Considering first the TCSPC instrument itself, some uncertainty in the measurements arise from its intrinsic parameters. With 300 nm incident light, the IRF of the photomultiplier tube ranged from 190 to 276 ps full-width at half-height (FWHH). The width of the IRF and the time resolution (32.5 ps/channel) limit the short components that can be reliably extracted from the fit, and certainly those <200 ps will have large errors on their amplitudes and lifetimes. Fluorescence emission decay components as short as 9—20 ps (Larsen et al., 2001) and 30—70 ps (Guest el al., 1991) (and much shorter by Wan et al., 2000) have been measured for 2AP in a stacked conformation, but in our instrument, a fit to such a short lifetime would be inaccurate. 

Stancik, A. L., and Brauns, E. B. (2008). Rearrangement of partially ordered stacked conformations contributes to the rugged energy landscape of a small ma hairpin. Biochemistry 47, 10834—10840. 

NADH is highly fluorescent, with absorption and emission maxima located at 340 and 450 nm, respectively, while NAD+ and NADH+ are not fluorescent (Figures 7.14 and 7.15). Schauenstein et al. (1980) explained the spectral modification of NADH+ by a higher percentage of the stacked conformation at a lower pH. 

Hoshino, T. (1991). An approximate estimate of self-association constants the self-stacking conformation of malvin quinoidal bases studied by IH NMR. Phytochemistry, 30, 2049-2055. 

Figure 6. Polymorphic forms of fat crystals, including the possible polymorphic transitions, subcell packing structures, stability characteristic, and triacylglycerol stacking conformations.

The adequacy of the GGA97 set of approximate functionals in describing relative energetics of conformers of a weakly bound intermolecular complex was tested also for the benzene dimer124. The T-shaped conformer was found to be the most stable (Eint =-2.09 kcal/mol). The slipped parallel arrangement was found to be slightly less stable (Ejnj=-1.95 kcal/mol). The stacked conformers were found to be less stable by about 0.5 kcal/mol, whereas the planar conformers were the least stable (Eint = -0.5-0.6 kcal/mol). 

---