arXiv subjects

D. W. Heermann

Publications and source records attributed to D. W. Heermann.

3 recordsLinked to original sources

arXiv2007

The influence of the cylindrical shape of the nucleosomes and H1 defects on properties of chromatin

We present a model improving the two-angle model for interphase chromatin (E2A model). This model takes into account the cylindrical shape of the histone octamers, the H1 histones in front of the nucleosomes and the vertical distance $d$ between the in and outgoing DNA strands. Factoring these chromatin features in, one gets essential changes in the chromatin phase diagram: Not only the shape of the excluded-volume borderline changes but also the vertical distance $d$ has a dramatic influence on the forbidden area. Furthermore, we examined the influence of H1 defects on the properties of the chromatin fiber. Thus we present two possible strategies for chromatin compaction: The use of very dense states in the phase diagram in the gaps in the excluded volume borderline or missing H1 histones which can lead to very compact fibers. The chromatin fiber might use both of these mechanisms to compact itself at least locally. Line densities computed within the model coincident with the experimental values.

cond-mat.soft↗

arXiv2005

Modelling and simulation of polycomb-dependent chromosomal interactions in drosophila

The conditions of the chromosomes inside the nucleus in the Rabl configuration have been modelled as self-avoiding polymer chains under restraining conditions. To ensure that the chromosomes remain stretched out and lined up, we fixed their end points to two opposing walls. The numbers of segments $N$, the distances $d_1$ and $d_2$ between the fixpoints, and the wall-to-wall distance $z$ (as measured in segment lengths) determine an approximate value for the Kuhn segment length $k_l$. We have simulated the movement of the chromosomes using molecular dynamics to obtain the expected distance distribution between the genetic loci in the absence of further attractive or repulsive forces. A comparison to biological experiments on \textit{Drosophila Melanogaster} yields information on the parameters for our model. With the correct parameters it is possible to draw conclusions on the strength and range of the attraction that leads to pairing.

q-bio.SC↗

arXiv1995

Large-scale Simulation of the Two-dimensional Kinetic Ising Model

We present Monte Carlo simulation results for the dynamical critical exponent $z$ of the two-dimensional kinetic Ising model using a lattice of size $10^6 \times 10^6$ spins. We used Glauber as well as Metropolis dynamics. The $z$-value of $2.16\pm 0.005$ was calculated from the magnetization and energy relaxation from an ordered state towards the equilibrium state at $T_c$.

cond-mat↗