Molecular persistence length

As discussed in the last 3 years, polysaccharides behave in solution under a worm like chain [26] the local stiffness of the chain is characterized by a persistance length (Ip) the larger Ip is, the larger the chain deviates from the gaussian behaviour in the usual molecular weight range of these natural polymers [27], This makes difficult to use the relations given in litterature for synthetic... 

For many polymers K and a values can be found in the Polymer Handbook [23]. In a recent study by Vanhee et al. [30] the universal calibration has been applied using the polystyrene (PS) calibration curve to characterize rigid rod poly(p-phenylenes) (PPP). It turned out that due to its larger persistence length, PPP with a certain mass requires a much larger volume than PS for the same molecular weight. Ron et al. employed universal calibration for the characterization of erodible copolymers [58]. 

Region I here the molecular chains partly assume helical (stiff) conformation from random coils where the persistence length gradually increases. 

All this leads to the question of how DNA affects nucleosomal stability at the molecular level. DNA bendability has been repeatedly put forward as a candidate to play an important role [280-282]. This property is related to the persistence length of DNA [283]. A study on the characterization of nucleosomes reconstituted onto methylated DNA [poly(dG-m dC) poly (dG-m dC)] [284] provides support to this hypothesis. Poly(dG-m dC) poly (dG-m dQ DNA can be induced to change from its B to its Z conformation in the presence of millimolar amounts of divalent ions [285] such as MgCl2. The persistence length of poly(dG-m dC) poly (dG-m dC) in the Z form in high salt was found to be 208 nm (ca. 612 bp) [286], a value much lower than that of the same polymer in the B form (93.8 nm, 276 bp) at... 

A theoretical approach is applied to elucidate the molecular conformations, associated flexibility, and dynamics of polylp-hydroxybenzoic acid) esters, pHB. Properties such as the radius of gyration and persistence length which are characteristic for the stiffness of a macromolecule are calculated on the basis of two different theoretical methods (a) Molecular dynamics and (b) the RIS model augmented by the more recent scheme for the matrix computations. The analysis of the results obtained by the latter method reflects a strong dependence on the choice of the structural parameters of the system. 

A theoretical analysis of the possible conformations of polylp-phenylene terephthalate) (PPTA) and polylp-phenylene isophthalate) (PPIA) is performed on the basis of molecular mechanics and molecular dynamics trajectories. The dependence of the persistence length on the fluctuations of the torsional angle around the ester bond is discussed for PPTA in the frame of the RIS model. Realistic parameters like bond length and bond angles are provided by computer simulations using MD. 

One remark must be made As the molecules of cellulose tricarbanilate possess such a large persistence length, the Gaussian range is only reached at considerable molecular weights, where reduced shear rate exceeds the value one. This value has been found to be critical with respect to... 

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