Radiopaque organic-inorganic hybrids based on poly(D,L-lactide).

Hybrid organic-inorganic nanocomposites were prepared starting from alpha,omega-triethoxysilane-terminated poly(d,l-lactic acid) (PDLLA) to be used as potential radiopaque biocompatible coatings for medical devices. The synthesis of the organic phase precursors of given chain length was achieved via anionic polymerization of d,l-lactide using a bifunctional initiator and subsequent triethoxysilane functionalization of the end groups. PDLLA-based ceramers (ceramic polymers) were then synthesized by the sol-gel process at room temperature (rt) in the presence of different amounts of tetraethoxysilane.

Single molecule studies of RNA secondary structure: AFM of TYMV viral RNA.

Nowadays, the development of experimental procedures for the determination of the secondary structure of RNA molecules is taking advantage of the novel single-molecule probing and imaging techniques. We report a method for the mapping of the secondary structure of RNA molecules spread on a flat surface by means of the atomic force microscope. Globular domains comprising groups of RNA secondary and tertiary structure elements separated by unstructured domains can be discerned in the micrographs and their position along the molecule contour can be measured directly on unstained specimens.

Sequence-dependent DNA dynamics by scanning force microscopy time-resolved imaging.

Scanning force microscopy was used to study in fluid the conformational fluctuations of two double-stranded DNA molecules resulting from differently cut pBR322 circular DNAs. A new approach was conceived to monitor the thermodynamic equilibrium of the chain dynamics on different scale lengths. This method made it possible to demonstrate that both the observed DNA molecules were allowed to equilibrate only on their local small-scale dynamics during the time of the experiment.

Plzf mediates transcriptional repression of HoxD gene expression through chromatin remodeling.

The molecular mechanisms that regulate coordinated and colinear activation of Hox gene expression in space and time remain poorly understood. Here we demonstrate that Plzf regulates the spatial expression of the AbdB HoxD gene complex by binding to regulatory elements required for restricted Hox gene expression and can recruit histone deacetylases to these sites. We show by scanning forced microscopy that Plzf, via homodimerization, can form DNA loops and bridge distant Plzf binding sites located within HoxD gene regulatory elements.

Recognition of the DNA sequence by an inorganic crystal surface.

The sequence-dependent curvature is generally recognized as an important and biologically relevant property of DNA because it is involved in the formation and stability of association complexes with proteins. When a DNA tract, intrinsically curved for the periodical recurrence on the same strand of A-tracts phased with the B-DNA periodicity, is deposited on a flat surface, it exposes to that surface either a T- or an A-rich face. The surface of a freshly cleaved mica crystal recognizes those two faces and preferentially interacts with the former one.