Intra-molecular mobility

The kinetics of tribochemical transformations. The role of mechanical stresses consists of not only the initiation of radical processes but in kinetic changes of the elemental stages of the chemical reactions with the participation of macromolecules as well. Plastic deformations increase reaction velocities that have been limited by travel of the reacting particles in the material bulk. Shear and tension accelerate the decay of the radicals with a free valence in the chain center. Chemical reactions are also affected by variations in the intra-molecular mobility and permolecular structure during pol3Tner deformation. 

Many suitable molecules can be designed, with end-groups chosen for SAM formation with dissimilar metal electrodes. For instance, two Au and one A1 electrode could be used. The molecule 0 2A would have two -SH terminations to bond to Au, and one -COOH end group (on D2) to bond to Al. The electron path between the two Au electrodes would traverse a donor moiety Dj with low IPD and an acceptor moiety A, while the path from the Al electrode to the second Au electrode would traverse a weaker donor moiety D2 (with larger IPd) and the common acceptor moiety A. The larger electron current would flow between the two Au electrodes, because the intra-molecular electron mobility would be larger Dj —> A, while the smaller electron current would flow D2 —> A. The smaller... 

The formation of disulfide bonds in proteins synthesized in vitro can be followed by measuring enzymatic activity or by an increased mobility compared to the reduced protein during SDS-PAGF. This increased mobility arises from the fact that, as disulfide-bonded proteins are intra-molecularly cross-linked, they form a more compact structure and occupy a smaller hydrodynamic volume compared to the reduced protein (Gold-enberg and Creighton, 1984). An illustration of this increase in mobility is shown in Fig. 2. Here the mRNA for preprolactin was translated in a cell-free system optimized for the formation of disulfide bonds, and then analyzed by SDS-PAGF. The translocated protein forms disulHde bonds under these conditions whereas the protein synthesized under the same conditions but in the absence of microsomal membranes does not form disulfide bonds. Thus the nascent protein must be translocated into microsomal vesicles for disulfide bond formation to occur. 

Figure 19.9 shows the result of the lineshape analysis for the spectrum of the crystalline component of A-PVA with a water content of 18% [33], which was carried out in the same way as for dried PVA films. Although an additional Gaussian curve must be introduced upheld for line III, the composite curve of the four lines, which is described by a broken line, reproduces well the experimental spectrum of the crystalline component. The additional upheld line can be assigned to the component free from the intra- and intermolecular hydrogen bonds, which may probably appear as a result of the enhancement in molecular mobility by water. In Fig. 19.8 the integrated fractions of lines I, II and III are also shown. The fractions of lines I and II signihcantly increase compared with those for the dry sample shown in Fig. 

Thomas, C.L.P., Mohammad, A., Examination of the effects of inter- and intra-molecular ion interactions in differential mobility spectrometry (DMS). Int. J. Ion Mobility Spectrom. 2006, 9. 

We have seen, on the other hand, that there is a second type of internal motions particularly in very large and mobile molecules, which do not arise from the action of intra-molecular forces but which, on the contrary, are so disposed that during their execution, the potential of the molecule remains constant. These motions are caused by the thermal energy of the individual parts of the large molecule and can best be compared to the chaotic motion of the molecules in a perfect gas. It is natural, therefore, in studying this kind of internal molecular motion, to employ methods similar to those that have proved useful in the theoretical treatment of... 

By using NFS, information on both rotational and translational dynamics can be extracted. In many cases, it would be favorable to obtain separate information about either rotational or translational mobility of the sensor molecule. In this respect, two other nuclear scattering techniques using synchrotron radiation are of advantage. Synchrotron radiation-based perturbed angular correlations (SRPAC) yields direct and quantitative evidence for rotational dynamics (see Sect. 9.8). NIS monitors the relative influence of intra- and inter-molecular forces via the vibrational density of states (DOS) which can be influenced by the onset of molecular rotation (see Sect. 9.9.5). 

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