Abstract
An oscillatory molecular adsorption pattern of the protein neutravidin from aqueous solution onto gold, in presence of a pre-deposited self assembled mono-molecular biotin film, is reported. Real time surface Plasmon resonance sensing was utilized for evaluation of the adsorption kinetics. Two different fractions were identified: in the initial phase, protein molecules attach irreversibly onto the Biotin ligands beneath towards the jamming limit, forming a neutravidin-biotin fraction. Afterwards, the growth rate exhibits distinct, albeit damped adsorption-desorption oscillations over an extended time span, assigned to a quasi reversibly bound fraction. These findings agree with, and firstly confirm a previously published model, proposing macro-molecular adsorption with time delay. The non-linear dynamic model is applicable to and also resembles non-damped oscillatory binding features of the hetero-catalytic oxidation of carbon monoxide molecules on platinum in the gas phase. An associated surface residence time can be linked to the dynamics and time scale required for self-organization.
Highlights
An oscillatory molecular adsorption pattern of the protein neutravidin from aqueous solution onto gold, in presence of a pre-deposited self assembled mono-molecular biotin film, is reported
A well known example in the gas phase is the hetero-catalytic oxidation of CO to CO2 on (110) oriented platinum surfaces at elevated temperature, in presence of oxygen
The inset to (a) exhibits a molecular structure model of the avidin-biotin complex taken from Fig. 4A of ref
Summary
An oscillatory molecular adsorption pattern of the protein neutravidin from aqueous solution onto gold, in presence of a pre-deposited self assembled mono-molecular biotin film, is reported. Electro-catalytically driven oscillations have been recorded at the Pt-aqueous electrolyte interface for various organic molecules that are usable as oxidation reactants, especially in fuel cell applications[2,3]. These initially poorly understood effects were occasionally noticed before, but wrongly attributed to experimental flaws. Adsorption is driven by electrostatic/electrochemical, van-der-Waals, Lewis acid/base, hydrogen bonding and covalent/chemical interaction forces It varies with all: pH of the solvent/buffer, substrate material, hydrophobic or hydrophilic surface conditions, ionic strength, protein type and molecular www.nature.com/scientificreports/. A weak repulsive interfacial force is acting onto the proteins
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