32 research outputs found
Graphene-protein bioelectronic devices with wavelength-dependent photoresponse
We implemented a nanoelectronic interface between graphene field effect
transistors (FETs) and soluble proteins. This enables production of
bioelectronic devices that combine functionalities of the biomolecular and
inorganic components. The method serves to link polyhistidine-tagged proteins
to graphene FETs using the tag itself. Atomic Force Microscopy and Raman
spectroscopy provide structural understanding of the bio/nano hybrid;
current-gate voltage measurements are used to elucidate the electronic
properties. As an example application, we functionalize graphene FETs with
fluorescent proteins to yield hybrids that respond to light at wavelengths
defined by the optical absorption spectrum of the proteinComment: 10 pages, 3 figures; To appear in Applied Physics Letter
Liquid-Crystalline Collapse of Pulmonary Surfactant Monolayers
During exhalation, the surfactant film of lipids and proteins that coats the alveoli in the lung is compressed to high surface pressures, and can remain metastable for prolonged periods at pressures approaching 70 mN/m. Monolayers of calf lung surfactant extract (CLSE), however, collapse in vitro, during an initial compression at ∼45 mN/m. To gain information on the source of this discrepancy, we investigated how monolayers of CLSE collapse from the interface. Observations with fluorescence, Brewster angle, and light scattering microscopies show that monolayers containing CLSE, CLSE-cholesterol (20%), or binary mixtures of dipalmitoyl phosphatidylcholine(DPPC)-dihydrocholesterol all form bilayer disks that reside above the monolayer. Upon compression and expansion, lipids flow continuously from the monolayer into the disks, and vice versa. In several respects, the mode of collapse resembles the behavior of other amphiphiles that form smectic liquid-crystal phases. These findings suggest that components of surfactent films must collapse collectively rather than being squeezed out individually