Conformation change intramolecular

The current understanding on activation of Tec kinases fits into a two-step model. In the first step an intramolecular interaction between the SH3 domain and aproline-rich region in the TH domain is disrupted by binding ofthe PH domain to phosphoinositides, G protein subunits, or the FERM domain of Fak. These interactions lead to conformational changes of Tec and translocation to the cytoplasmic membrane where, in a second step, Src kinases phosphorylate a conserved tyrosine residue in the catalytic domain thereby increasing Tec kinase activity. Autophosphorylation of a tyrosine residue in the SH3 domain further prevents the inhibitory intramolecular interaction resulting in a robust Tec kinase activation. 

Lehrer, S. S. (1997). Intramolecular pyrene excimer fluorescence A probe of proximity and protein conformational change. Fluorescence Spectroscopy 278, 286-295. 

No evidence has yet been obtained in support of such a mechanism in the present context, and it is unlikely that it has general applicability. NMR measurements for example provide no support for a conformational change of PCu(I) on association with Cr(III) complexes (13). Moreover it has in one case been demonstrated that ket in (4) is not dependent on ionic strength, consistant with an intramolecular as opposed to intermolecular process (11). Although caution is required, particularly as isolated examples of (7) - (8) may exist, the invoking of such a mechanism seems to be a case of looking for greater complexity than may actually exist. A reasonable stance, and one which we have adopted, is that discussion should proceed in terms of (5) -(6) until evidence in support of (7) - (8) is obtained. 

The authors believe that electron exchange occurs at every intramolecular collision . Thus, their work should provide the first quantitative measurements of the frequency of intramolecular collision between end-groups attached to flexible chains. According to these authors such frequency reflects an intrinsic property of chain molecules, referred to as the dynamic flexibility, which is a measure of the rate of conformational change. It should be distinguished from the static flexibility, which depends on the multitude of... 

The viscosity dependence of intramolecular excimer formation is complex. As in the case of molecular rotors (Section 8.2), most of the experimental observations can be interpreted in terms of free volume. However, compared to molecular rotors, the free volume fraction measured by intramolecular excimers is smaller. The volume swept out during the conformational change required for excimer formation is in fact larger, and consequently these probes do not respond in frozen media or polymers below the glass transition temperature. 

For many years, intramolecular reactions such as conformational changes, bond cleavage, bond formation, and valence isomerizations have been observed only when hydrocarbons were reduced with alkali metals in ethereal solvents. In most electrochemical experiments, these reactions were dominated by the electrophilic processes already described. However, progress in experimental techniques [8, 9, 27-29] has made these reactions accessible to electroanalytical investigations, providing new mechanistic insight. 

PC3P is a sensitive probe for local viscosity measurement by forming an intramolecular excimer [35,36]. The extent of excimer emission depends upon the rate of conformational change of the chain linking the two... 

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