Protein uptake at the interface of a millimeter-sized air bubble in water is investigated by a recently developed differential interferometric technique. The technique allows the study of capillary waves with amplitudes around 10-9 m, excited at the surface of the bubble by an electric field of intensity on the order of 10 V/cm. When one studies the resonant modes of the bubble (radial and shape modes), it is possible to assess variations of interfacial properties and, in particular, of the net surface charge as a function of bulk protein concentration. Sensing the interfacial charge, the technique enables us to follow the absorption process in conditions of low concentrations, not easily assessable by other methods. We focus on bovine serum albumin (BSA) and lysozyme as representatives of typical globular proteins. To provide comprehensive insight into the novelty of the technique, we also investigated the equilibrium adsorption of sodium dodecyl sulfate (SDS) ionic surfactant for bulk concentrations at hundreds of times lower than the Critical Micelle Concentration (CMC). Results unveil how the absorption of charged molecules affects the amplitudes of the bubble resonant modes even before affecting the frequencies in a transition-like fashion. Different adsorption models are proposed and developed. They are validated against the experimental findings by comparing frequency and amplitude data. By measuring the charging rate of the bubble interface, we have followed the absorption kinetics of BSA and lysozyme recognizing a slow, energy barrier limited phenomena with characteristic times in agreement with data in the literature. The evaluation of the surface excess concentration (Γ) of BSA and SDS at equilibrium is obtained by monitoring charge uptake. At the investigated low bulk concentrations, reliable comparisons with literature data from equilibrium surface tension isotherm models are reported.

Protein Adsorption at the Air-Water Interface by a Charge Sensing Interferometric Technique / P. Brocca, A. Saponaro, B. Introini, V. Rondelli, M. Pannuzzo, D. Raciti, M. Corti, A. Raudino. - In: LANGMUIR. - ISSN 0743-7463. - 35:49(2019 Dec), pp. 16087-16100. [10.1021/acs.langmuir.9b02201]

Protein Adsorption at the Air-Water Interface by a Charge Sensing Interferometric Technique

P. Brocca
;
A. Saponaro;B. Introini;V. Rondelli;M. Corti;
2019

Abstract

Protein uptake at the interface of a millimeter-sized air bubble in water is investigated by a recently developed differential interferometric technique. The technique allows the study of capillary waves with amplitudes around 10-9 m, excited at the surface of the bubble by an electric field of intensity on the order of 10 V/cm. When one studies the resonant modes of the bubble (radial and shape modes), it is possible to assess variations of interfacial properties and, in particular, of the net surface charge as a function of bulk protein concentration. Sensing the interfacial charge, the technique enables us to follow the absorption process in conditions of low concentrations, not easily assessable by other methods. We focus on bovine serum albumin (BSA) and lysozyme as representatives of typical globular proteins. To provide comprehensive insight into the novelty of the technique, we also investigated the equilibrium adsorption of sodium dodecyl sulfate (SDS) ionic surfactant for bulk concentrations at hundreds of times lower than the Critical Micelle Concentration (CMC). Results unveil how the absorption of charged molecules affects the amplitudes of the bubble resonant modes even before affecting the frequencies in a transition-like fashion. Different adsorption models are proposed and developed. They are validated against the experimental findings by comparing frequency and amplitude data. By measuring the charging rate of the bubble interface, we have followed the absorption kinetics of BSA and lysozyme recognizing a slow, energy barrier limited phenomena with characteristic times in agreement with data in the literature. The evaluation of the surface excess concentration (Γ) of BSA and SDS at equilibrium is obtained by monitoring charge uptake. At the investigated low bulk concentrations, reliable comparisons with literature data from equilibrium surface tension isotherm models are reported.
Settore FIS/07 - Fisica Applicata(Beni Culturali, Ambientali, Biol.e Medicin)
dic-2019
Article (author)
File in questo prodotto:
File Dimensione Formato  
acs.langmuir.pdf

accesso riservato

Tipologia: Publisher's version/PDF
Dimensione 3.2 MB
Formato Adobe PDF
3.2 MB Adobe PDF   Visualizza/Apri   Richiedi una copia
possible green_manuscript.pdf

accesso aperto

Tipologia: Pre-print (manoscritto inviato all'editore)
Dimensione 1.66 MB
Formato Adobe PDF
1.66 MB Adobe PDF Visualizza/Apri
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/704744
Citazioni
  • ???jsp.display-item.citation.pmc??? 0
  • Scopus 7
  • ???jsp.display-item.citation.isi??? 4
social impact