Long-range participation

Long-range participation of Cl auxiiiary to direct cr-siaiyiation... 

Despite the wealth of experimental and theoretical investigations of CT in DNA assemblies designed by chemists and physicists, the role of DNA CT in biology remains to be discovered. Does long-range DNA CT occur in vivo If so, why, and how is it regulated How do proteins influence and/or participate in DNA-mediated CT We have initiated a variety of experiments to address these fundamental questions. 

Intramolecular interaction is a powerful factor that controls molecular architecture, particularly in the case of geometrically flexible molecular systems. The existence and energies of intramolecular classical hydrogen bonds and their role in chemistry and biochemistry are well known. They stabilize molecular conformations, promote short- and long-range proton transfers, participate in the creation of three-dimensional structures of large molecules and play a fundamental role in the phenomenon of molecular recognition. 

However, the use of techniques which analyze both the short and the long range orders of the VPO materials, like RED of X-Rays (2 ), and W MAS-NMR (3,4 ), showed the possible participation of some V (V) structures to the reaction. Previously, there has been some ambiguity insofar as these structures should be a consequence of the reoxidation of the starting VOHPO4, 0.5 H2O precursor or of the basic (VO)2P207 matrix and hence do not intervene directly in the reaction mechanism of butane oxidation to maleic anhydride. The possible role of a limited amount of V(V) sites to control the selectivity to maleic anhydride was previously postulated (5). 

The peroxynitrate CH3C0CH200N02 formed from the N02 reaction thermally decomposes, with a rate constant of 3 s-1 at 700 Torr and 295 K. Sehested et al. (1998b) suggest that its lifetime with respect to thermal decomposition is sufficiently small even at the lower temperatures of the upper troposphere that this species cannot participate in long-range transport of NOx, as is the case for PAN, and that in the upper troposphere, reaction of CH3C0CH200N02 with OH and photolysis will be major fates. 

The generator matrix treatment of simple chains with excluded volume described earlier S 010) properly reproduces the known chain length dependence of the mean-square dimensions in the limit of infinite chains. The purpose of this paper is to compare the behaviour of finite generator matrix chains with that of Monte-Carlo chains in which atoms participating in long-range interactions behave as hard spheres. The model for the unperturbed chain is that developed by Flory et at. for PE (S 027). 

Expansion of subchains in a linear PE chain with excluded volume is evaluated by two methods. (1) Monte-Carlo chains with methylene groups participating in long-range interactions behave as impenetrable spheres with a diameter of 300 pm, and (25 generator matrix calculations in which expansion is produced without any effect on the probability of a trans placement in an infinitely long chain. 

Response of the mean square dipole moment, < J2>, to excluded volume is evaluated for several chains via Monte-Carlo methods. The chains differ in the manner in which dipolar moment vectors are attached to the local coordinate systems for the skeletal bonds. In the unperturbed state, configurational statistics are those specified by the usual RIS model for linear PE chains. Excluded volume is introduced by requiring chain atoms participating in long-range interactions to behave as hard spheres. 

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