In vitro dry powder inhaler formulation performance considerations.

It has long been desired to match airflow conditions during formulation evaluation to those of relevance to lung deposition. In this context several strategies have been adopted involving sampling at different: flow rate (without consideration of flow conditions, e.g.

Molecular voids formed from effective attraction in submonolayer DNA deposited on Au(111).

The development of DNA-based biosensors requires a deep understanding of how DNA molecules adsorb and organize on solid state surfaces as well as the electronic properties of individual and aggregates of DNA molecules. Using scanning tunneling microscopy (STM) and atomic force microscopy (AFM), we have successfully characterized an attractive force driven molecular void formation for DNA chemically adsorbed on Au(111) as a function of strand length and deposition conditions. Here we report the observation of these void structures formed on the Au(111) surface by adsorption of both 45 and 90 base pair long, thiolated double-stranded DNA.