In situ preparation of the nuclear matrix of Physarum polycephalum: ultrastructural and biochemical analysis of different matrix isolation procedures.

A novel method for in situ preparation of nuclear matrix from whole plasmodia of Physarum polycephalum without isolation of nuclei is presented. Plasmodia are encapsulated in agarose beads and after solubilization of the cytoplasm the nuclear matrix is prepared. With this quick and easy technique nuclear matrix can be reproducibly prepared with perfect recovery. We compared the ultrastructural and biochemical properties of the matrix after three different matrix isolation procedures: preparation with high salt, ammonium sulphate and lithium diiodosalicylic acid. The results show that the ultrastructure and protein composition of the three types of matrix are very similar or even identical. We conclude that many of the conflicting results on nuclear matrix in the literature are due to perturbations of nuclear integrity during the isolation of nuclei. For this reason the new in situ method is an important approach in the standardization of nuclear matrix isolation.