Chain skeleton effect

Methods are presented for calculating mean-square dipole moments, , of polypeptide chains, averaged over all configurations of the chain skeleton. They are applicable to chains of any number (x+ U of residues, the residues being In any specified sequence. Dipole moments of glycine peptides are calculated and compared with experimental determinations. The effects of stereosequence on the dipole moment are well reproduced by the calculations. Ip is taken to be 380 pm. 

Using chemical or protonic doping, the electric charges on the polymer chains are compensated by counterion injection. In the case of protonic doping (essentially in polyaniline), the addition of protons does not change the overall number of electrons in the chain skeleton. But one of the two electrons of the nitrogen doublet become caught in the N—H bond, and then the effective number of electrons available for the tt system is modified. 

The overall biosynthetic pathway to the tetracychnes has been reviewed (74). Studies (75—78) utilising labeled acetate and malonate and nmr analysis of the isolated oxytetracycline (2), have demonstrated the exclusive malonate origin of the tetracycline carbon skeleton, the carboxamide substituent, and the folding mode of the polyketide chain. Feeding experiments using [1- 02] acetate and analysis of the nmr isotope shift effects, led to the location of... 

By covalently attaching reactive groups to a polyelectrolyte main chain the uncertainty as to the location of the associated reactive groups can be eliminated. The location at which the reactive groups experience the macromolecular environment critically controls the reaction rate. If a reactive group is covalently bonded to a macromolecular surface, its reactivity would be markedly influenced by interfacial effects at the boundary between the polymer skeleton and the water phase. Those effects may vary with such factors as local electrostatic potential, local polarity, local hydrophobicity, and local viscosity. The values of these local parameters should be different from those in the bulk phase. 

Introduction of FCH2 and F3C groups into the side chain of 1-alkylsilatranes increases the toxicity more effectively than introduction of trifluoromethyl groups into the silatrane skeleton (Table 6). 

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