X-ray spectromicroscopy study of competitive adsorption of protein and peptide onto polystyrene-poly(methyl methacrylate)
ABSTRACT A synchrotron-based x-ray photoemission electron microscope (X-PEEM) was used to investigate the coadsorption of a mixture of human albumin serum and SUB-6, a synthetic antimicrobial peptide, to a phase-segregated polystyrene/poly(methyl methacrylate) (PMMA) substrate at varying concentrations and pH. The authors show that X-PEEM could detect the peptide adsorbed from solution at concentrations as low as 5.5 x 10(-9)M and could differentiate the four components via near-edge x-ray absorption fine structure spectromicroscopy. At neutral pH the SUB-6 peptide adsorbed preferentially to PMMA. At a pH of 11.8 where the charge on the peptide was neutralized, there was a more balanced adsorption of both species on the PMMA domains. The authors interpret these observations as indicative of the formation of an electrostatic complex between positive peptide and negative protein at pH of 7.0. This solution complex had an adsorption behavior that depended on the polarity of the substrate domains, and favored adsorption to the electronegative PMMA regions. At a pH of 11.8 the complex formation was suppressed and a more competitive adsorption process was observed.
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ABSTRACT: Synchrotron-based X-ray photoemission electron microscopy (X-PEEM) is used to characterize the near surface composition of polyethylene oxide (PEO) combined with 1.5, 5, and 10 wt.-% pentaerythritol triacrylate (PETA) crosslinker. It is found that as the concentration of PETA increases, it becomes the dominant component in the top 10 nm of the film surface. The same surfaces are also exposed to human serum albumin (HSA) and the distributions of the protein relative to PEO and PETA measured with X-PEEM. A positive correlation is found between levels of PETA and HSA at the surface. Above PETA concentrations of 5 wt.-%, HSA adsorption is significant, which suggests high levels of PETA (often used to immobilize PEO by crosslinking) can significantly reduce the non-fouling properties of PEO.Advanced Engineering Materials 05/2010; 12(5). DOI:10.1002/adem.200980050 · 1.51 Impact Factor
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ABSTRACT: Near-edge x-ray absorption fine structure (NEXAFS) spectroscopy provides detailed information about the orientation and alignment of thin films. NEXAFS is a synchrotron based technique - the availability of beam-time per user is typically limited to no more than a few weeks per year. The limited availability is currently a true barrier for using NEXAFS in combinatorial studies of molecular alignment. We have recently demonstrated how large area full field NEXAFS imaging allows users to pursue combinatorial studies of surface chemistry. Now we report an extension of this approach which allows the acquisition of orientation information from a single NEXAFS image. An array with 80 elements (samples) containing eight series of different surface modifications was mounted on a curved substrate allowing the collection of NEXAFS spectra with a range of orientations with respect to the x-ray beam. Images collected from this array show how hyperspectral NEXAFS data collected from curved surfaces can be used for high-throughput molecular orientation analysis.ACS Combinatorial Science 07/2014; 16(9). DOI:10.1021/co5001162 · 3.40 Impact Factor
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ABSTRACT: Understanding competitive adsorption-desorption of proteins onto surfaces is an important area of research in food processing and biomedical engineering. Here, we demonstrate, how electrospray-differential mobility analysis that has been traditionally used for characterizing bionanoparticles, can be used for quantifying complex competitive adsorption-desorption of oligomeric proteins or multiprotein systems using monomers and dimers of IgM as a model example onto silica and modified silica surfaces. Using ES-DMA, we show that IgM dimers show a preference to stay adsorbed to different surfaces although monomers adsorb more easily and desorption rates of monomers and dimers of IgM are surface-type-dependent and are not significantly affected by shear. We anticipate that this demonstration will make ES-DMA a popular "label-free" method for studying multicomponent multi-oligomeric protein adsorption to different surfaces in the future.Journal of Colloid and Interface Science 03/2013; 402. DOI:10.1016/j.jcis.2013.02.050 · 3.55 Impact Factor