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Interaction of heme proteins with poly(propyleneimine) dendrimers in layer‐by‐layer assembly films under different pH conditions
Author(s) -
He Pingli,
Li Min,
Hu Naifei
Publication year - 2005
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.20359
Subject(s) - quartz crystal microbalance , chemistry , dendrimer , layer by layer , cyclic voltammetry , isoelectric point , ultraviolet visible spectroscopy , adsorption , point of zero charge , ellipsometry , analytical chemistry (journal) , surface charge , aqueous solution , layer (electronics) , crystallography , inorganic chemistry , thin film , chromatography , polymer chemistry , organic chemistry , electrochemistry , nanotechnology , electrode , materials science , enzyme
With the isoelectric point at pH 7.4, hemoglobin (Hb) has net positive surface charges at pH 5.0 and overall negative charges at pH 9.0, and is essentially neutral at pH 7.0. The fifth‐generation poly(propyleneimine) (PPI) dendrimer is usually positively charged in aqueous solution. The {PPI/Hb} n films under different pH conditions have been successfully fabricated on various solid surfaces by the layer‐by‐layer assembly technique, and the growth of films was monitored by ultraviolet‐visible (UV‐vis) spectroscopy, quartz crystal microbalance (QCM), and cyclic voltammetry (CV). Not only was the negatively charged Hb at pH 9.0 alternately adsorbed with positively charged PPI onto solid substrates by electrostatic attraction between them, but the positively charged Hb at pH 5.0 was also successfully assembled with like charged PPI into layer‐by‐layer {PPI/Hb(pH 5.0)} n films. For the latter, the localized electrostatic interaction or the charge reversal of proteins on PPI surface may be the main driving force. For {PPI/Hb(pH 7.0)} n films, however, the hydrophobic/hydrophilic interaction may play a more important role in the assembly, making the amount of adsorbed Hb even less than that of {PPI/Hb(pH 5.0)} n films. For comparison, negatively charged catalase (Cat) at pH 8.0 was used to assemble layer‐by‐layer films with positive PPI, but {PPI/Cat} n films showed quite different properties from {PPI/Hb} n films. UV‐vis and infrared (IR) spectroscopy, QCM, ellipsometry, and voltammetry were utilized to characterize the {PPI/protein} n films. The results suggest that the proteins in the multilayer films retain their near‐native structure and display good voltammetric response for heme Fe(III)/Fe(II) redox couples at underlying pyrolytic graphite (PG) electrodes. Electrocatalysis of oxygen and hydrogen peroxide based on direct electrochemistry of heme proteins at {PPI/protein} n film electrodes was also demonstrated. © 2005 Wiley Periodicals, Inc. Biopolymers 79: 310–323, 2005 This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com