Conformational transitions of a diblock polyampholyte in 2 and 3 dimensions

• Published in: Physics letters. A 1999-07, Vol.258 (2), p.92-98
• Main Authors: Imbert, J.B., Victor, J.M., Tsunekawa, N., Hiwatari, Y.
• Format: Article
• Language: English
• ISSN: 0375-9601; 1873-2429
• DOI: 10.1016/S0375-9601(99)00341-2

We report here the first extensive study of the conformational transitions of a diblock polyampholyte (made of two symmetric blocks, one positively, the other negatively charged). Results are obtained by means of a Monte Carlo simulation on a square (resp. cubic) lattice in 2 (resp. 3) dimensions, using the Bond Fluctuation algorithm together with a Multiple Histogram method. In both dimensions, an early (i.e. high temperature) transition is observed which is shown to correspond to the pairing of both blocks together, resulting in a `super-coil', each `super-monomer' being a dipole made of one positive and one negative monomer. Phenomenological characteristics of this pairing transition are given and its specificity is outlined. A second transition is also observed at a lower temperature in both dimensions. However, whereas it is a mere coil-globule transition of the `super-coil' in three dimensions, it happens to be rather a folding in two dimensions because of topological constraints.