IFEG   20353
INSTITUTO DE FISICA ENRIQUE GAVIOLA
Unidad Ejecutora - UE
artículos
Título:
Surface coverage dictates the surface bio-activity of d-amino acidoxidase
Autor/es:
ELISA HERRERA; CARLA E. GIACOMELLI
Revista:
COLLOIDS AND SURFACES B-BIOINTERFACES
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Año: 2014 vol. 117C p. 296 - 302
ISSN:
0927-7765
Resumen:
This work presents a systematic study on the relationship between the adsorptionmechanism and the surface bio-activity of D-amino acid oxidase (pkDAAO). Thisrational approach is based on measuring the characteristic filling and relaxation timesunder different experimental conditions. With such a goal, real-time adsorptiondesorptionexperiments at different degrees of surface coverage were performed tuningthe electrostatic and hydrophobic interactions by changing the pH condition for theadsorption and the substrate properties (silica or gold). Surface bio-activity wasmeasured in situ by amperometry using the bio-functional surface as the workingelectrode and ex situ by spectrophotometry. On both solid substrates, pkDAAOadsorption is a transport-controlled process, even under unfavorable electrostaticinteractions (charged protein and substrate with the same sign) due to the highpercentage of basic amino acids in the enzyme. On silica, the relaxation step iselectrostatic in nature and occurs in the same time-scale as filling the surface when thesubstrate and the enzyme are oppositely charged at low surface coverage. Underunfavorable electrostatic conditions, the relaxation (if any) occurs at long time.Accordingly, the bio-activity of the native pkDAAO is preserved at any surfacecoverage. On gold, this step is driven by hydrophobic interactions (pH-independent)and the surface bio-activity is highly dependent on the degree of surface coverage.Under these conditions, the surface bio-activity is preserved only at high surfacescoverage. Our results clearly indicate that pKDAAO bio-functionalized surfaces cannotbe coupled to ampereometry because the analyte interferes the electrochemical signal.However, this simple bio-functionalized strategy can be joined to other detectionmethods.