Biocompatible multishell architecture for iron oxide nanoparticles.

The coating of super-paramagnetic iron oxide nanoparticles (SPIONs) with multiple shells is demonstrated by building a layer assembled from carboxymethyldextran and poly(diallydimethylammonium chloride). Three shells are produced stepwise around aggregates of SPIONs by the formation of a polyelectrolyte complex. A growing particle size from 96 to 327 nm and a zeta potential in the range of +39 to -51 mV are measured.

Oligomerization and binding of the Dnmt3a DNA methyltransferase to parallel DNA molecules: heterochromatic localization and role of Dnmt3L.

Structural studies showed that Dnmt3a has two interfaces for protein-protein interaction in the heterotetrameric Dnmt3a/3L C-terminal domain complex: the RD interface (mediating the Dnmt3a-3a contact) and the FF interface (mediating the Dnmt3a-3L contact). Here, we demonstrate that Dnmt3a-C forms dimers via the FF interface as well, which further oligomerize via their RD interfaces. Each RD interface of the Dnmt3a-C oligomer creates an independent DNA binding site, which allows for binding of separate DNA molecules oriented in parallel.

Formation of nucleoprotein filaments by mammalian DNA methyltransferase Dnmt3a in complex with regulator Dnmt3L.

The C-terminal domains of Dnmt3a and Dnmt3L form elongated heterotetramers (3L-3a-3a-3L). Analytical ultracentrifugation confirmed the Dnmt3a-C/3L-C complex exists as a 2:2 heterotetramer in solution. The 3a-3a interface is the DNA-binding site, while both interfaces are essential for AdoMet binding and catalytic activity.

The M.EcoRV DNA-(adenine N6)-methyltransferase uses DNA bending for recognition of an expanded EcoDam recognition site.

The M.EcoRV DNA methyltransferase recognizes GATATC sites. It is related to EcoDam, which methylates GATC sites.