No abstract

No abstract

Silica surfaces modified with nitrilotriacetic acid (NTA)-polyethylene glycol (PEG) derivatives were used for immobilizing hexahistidine-tagged green fluorescent oprotein (his 6 -GFP), biotin/ streptavidin-AlexaFluor555 (his 6 -biotin/SA-AF) and gramicidin A-containing vesicles (his 6 -gA). Three types of surface-reactive PEG derivatives-NTA-PEG3400-Si(OMe) 3 , NTA-PEG3400-vinylsulfone, and mPEG5000-Si(OMe) 3 (control)-were grafted onto silica and tested for their ability to capture his 6 -tag species via his 6 :Ni 2+ :NTA chelation.The composition and thicknesses of the PEG-modified surfaces were characterized using x-ray photoelectron spectroscopy, contact angle, and ellipsometry. Protein capture efficiencies of the NTA-PEG-grafted surfaces were evaluated by measuring fluorescence intensities of these surfaces after exposure to his 6 -tag species. XPS and ellipsometry data indicate that surface adsorption occurs via specific interactions between the his 6 -tag and the Ni 2+ :NTA-PEG-grafted surface. Protein immobilization was most effective for NTA-PEG3400-Si(OMe) 3 -modified surfaces, with maximal areal densities achieved at 45 pmol/cm 2 for his 6 -GFP and 95 fmol/cm 2 for his 6 -biotin/SA-AF. Lipid vesicles containing his 6 -gA in a 1:375 gA:lipid ratio could also be immobilized on Ni 2+ :NTA-PEG3400-Si(OMe) 3 -modified surfaces at 0.5 mM total lipid. Our results suggest that NTA-PEG-Si (OMe) 3 conjugates may be useful tools for immobilizing his 6 -tag proteins on solid surfaces to produce protein-functionalized surfaces.

No abstract

Fibrinogen (FB) and other serum proteins leak into the aqueous alveolar lining layer due to lung injuries. The adsorption of these serum proteins at the air/aqueous interface can produce higher surface tensions than the pulmonary lipids, and acute respiratory distress syndrome (ARDS) can ensue. By having a molecular adsorption mechanism, as compared to a particulate adsorption mechanism of other longer chain lipids, dilauroylphosphatidylcholine (DLPC) lipid can expel FB from the air/aqueous interface at 25 degrees C, in water or in phosphate-buffered saline, as proven by tensiometry (also at 37 degrees C), ellipsometry, and infrared reflection-absorption spectroscopy. Moreover, before FB is displaced by DLPC at the interface, there is a substantial initial enhancement in the FB adsorption, consistent with some interaction or binding of DLPC with FB to produce a more hydrophobic protein surface. After the FB molecules have been displaced by DLPC, or when DLPC has already adsorbed at the interface, FB molecules are less favored to adsorb near the DLPC monolayer with the lecithin headgroups facing toward them. The results have implications for possible uses of DLPC lipid in potential lung surfactant formulations in treating patients with ARDS.