Conformational change coupled with

On benzene and some other aromatic systems, the donor or acceptor nature of a substituent is critical for the MCD sign, whereas on others such as pyridine it is not, at least for weak substituents. Further, the MCD is helpful for the analysis of a wide field of chemical events such as conformational changes coupled with substitutions, proton tautomerism, proton dissociation on aromatics, or through-space interaction in bicyclic aromatic systems 299-318>. 

Conformational Changes Coupled with the Isotropic-Nematic Transition... 

The conformation changes coupled with the four-electron reduction processes for the PMI-containing catenanes are summarized in Fig. 9.6. 

The 3 isozymes are activated by G protein-coupled receptors through two different mechanisms [2]. The first involves activated a-subunits of the Gq family of heterotrimeric G proteins (Gq, Gn, Gi4, G15/16). These subunits activate the (31, (33 and (34 PLC isozymes through direct interaction with a sequence in the C terminus. The domain on the Gqa-subunit that interacts with the (3 isozymes is located on a surface a-helix that is adjacent to the Switch III region, which undergoes a marked conformational change during activation. The second mechanism of G protein activation of PLC 3 isozymes involves (3y-subunits released from Gi/0 G proteins by their pertussis toxin-sensitive activation by certain receptors. The 3y-subunits activate the 32 and 33 PLC isozymes by interacting with a sequence between the conserved X and Y domains. 

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