X-ray spectromicroscopy study of competitive adsorption of protein and peptide onto polystyrene-poly (methacrylate)

BIMR, TuesduesMcMaster University, Hamilton, Ontario, Canada L8S 4M1.
Biointerphases (Impact Factor: 3.37). 06/2008; 3(2):FB27. DOI: 10.1116/1.2956637
Source: PubMed


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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    • "* C=O transition of the peptide amide backbone. Compared to other biomolecules such as human serum albumin (HSA) protein or the arginine-rich cationic peptide SUB-6 (Leung 2009a, b; Stewart-Ornstein et al. 2007; Leung et al. 2008), the amino acid sequence of anoplin does not contain aromatic residues, and thus there is no C 1s ! * C=C transition at 285.2 eV, which only exists if there are carbon–carbon double bonds. "
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