Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0267964 (PAA)
 2,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We use small-angle x-ray scattering (SAXS) as a tool to study the binding of proteins to spherical polyelectrolyte brushes (SPB) in situ. The SPB consists of a solid core of approximately 100 nm diam onto which long polyelectrolyte chains [poly(styrene sulfonic acid, PSS) and poly(acrylic acid, PAA)] have been densely grafted. The proteins used in this investigation, Bovine Serum Albumine (BSA) and Bovine Pancreatic Ribonuclease A (RNase A), adsorb strongly to these SPB if the ionic strength is low despite their negative charge. Virtually no adsorption takes place at high ionic strength. SAXS demonstrates that both proteins are distributed within the brush. The findings reported here give further evidence that the strong adsorption of proteins to SPB is due to the "counterions release forces": The patches of positive charge on the surface of the proteins become multivalent counterions of the polyelectrolyte chains. Thus, a concomitant number of co- and counterions is thereby released and the entropy of the entire system is increased. The repulsive Coulombic interaction as well as the steric repulsion between the proteins and the brush layer are counterbalanced by this effect. The data discussed here demonstrate that the adsorption of proteins in SPB presents a new principle for the immobilization of proteins.
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PMID:Interaction of proteins with spherical polyelectrolyte brushes in solution as studied by small-angle x-ray scattering. 1569 58

The ability to immobilize proteins with high binding capacities on surfaces while maintaining their activity is critical for protein microarrays and other biotechnological applications. We employed poly(acrylic acid) (PAA) brushes as templates to immobilize ribonuclease A (RNase A), which is commonly used to remove RNA from plasmid DNA preparations. The brushes are grown by surface-anchored atom-transfer radical polymerization (ATRP) initiators. RNase A was immobilized by both covalent esterification and a high binding capacity metal-ion complexation method to PAA brushes. The polymer brushes immobilized 30 times more enzyme compared to self-assembled monolayers. As the thickness of the brush increases, the surface density of the RNase A increases monotonically. The immobilization was investigated by ellipsometry, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). The activity of the immobilized RNase A was determined using UV absorbance. As much as 11.0 microg/cm(2) of RNase A was bound to PAA brushes by metal-ion complexation compared to 5.8 microg/cm(2) by covalent immobilization which is 30 and 16 times the estimated mass bound in a monolayer. The calculated diffusion coefficient D was 0.63 x 10(-14) cm(2)/s for metal-ion complexation and 0.71 x 10(-14) cm(2)/s for covalent immobilization. Similar values of D indicate that the binding kinetics is similar, but the thermodynamic equilibrium coverage varies with the binding chemistry. Immobilization kinetics and thermodynamics were characterized by ellipsometry for both methods. A maximum relative activity of 0.70-0.80 was reached between five and nine monolayers of the immobilized enzyme. However, the relative activity for covalent immobilization was greater than that of metal-ion complexation. Covalent esterification resulted in similar temperature dependence as free enzyme, whereas metal-ion complexation showed no temperature dependence indicating a significant change in conformation.
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PMID:Polymeric brushes as functional templates for immobilizing ribonuclease A: study of binding kinetics and activity. 1807 97