Actin complexes in the cell nucleus: new stones in an old field.

Actin is a well-known protein that has shown a myriad of activities in the cytoplasm. However, recent findings of actin involvement in nuclear processes are overwhelming. Actin complexes in the nucleus range from very dynamic chromatin-remodeling complexes to structural elements of the matrix with single partners known as actin-binding proteins (ABPs). This review summarizes the recent findings of actin-containing complexes in the nucleus. Particular attention is given to key processes like chromatin remodeling, transcription, DNA replication, nucleocytoplasmic transport and to actin roles in nuclear architecture. Understanding the mechanisms involving ABPs will definitely lead us to the principles of the regulation of gene expression performed via concerting nuclear and cytoplasmic processes.

Structure analysis of intercalated layer silicates: combination of molecular simulations and experiment.

Na(+)-montmorillonite type Wyoming, cloisite Na(+) from Southern Clay Products, Inc., was intercalated (i) with octadecylammonium cations and subsequently intercalated with octadecylamine molecules, (ii) with dodecylamine molecules, and (iii) with octylamine molecules to determine the applicability of these intercalates for nanocomposite materials on the base of polymer/clay. The structures were determined on the basis of a combination of results from X-ray diffraction and molecular simulations. The calculated values of basal spacings are in good agreement with experimental basal spacings when experimental samples were prepared. The interlayer space of intercalated montmorillonite shows a monolayer or bilayer arrangement of alkyl chains in dependence on the concentration of the intercalation solution. The values of the total sublimation energy, interaction energy, and exfoliation energy were calculated for all investigated samples. Low values of exfoliation energies lead to better exfoliation of intercalated silicate layers and this material appears suitable for use as a precursor for polymer/clay nanocomposites. The values of exfoliation energy for the investigated samples show that montmorillonite intercalated with dodecylamine or octadecylamine molecules is suitable for exfoliation of silicate layers.