β-Sheets Orientation in Physisorbed Protein Layers

Matteo Piscitelli; Diellza Bajrami; Cinzia Di Franco; Lucia Sarcina; Michele Catacchio; Eleonora Macchia; Luisa Torsi; Boris Mizaikoff; Gaetano Scamarcio

doi:10.1002/admi.202400867

β-Sheets Orientation in Physisorbed Protein Layers

Matteo Piscitelli, Diellza Bajrami, Cinzia Di Franco, Lucia Sarcina, Michele Catacchio, Eleonora Macchia, Luisa Torsi, Boris Mizaikoff, Gaetano Scamarcio

Research output: Contribution to journal › Article › Scientific › peer-review

Abstract

Physisorption of antibodies onto surfaces is a low-cost, rapid, and effective approach for immobilizing bioreceptors in applications such as bioelectronic sensors. However, there is a prevailing notion that physisorbed protein layers lack structural order, thus potentially compromising their stability and sensitivity compared to antibody films that are covalently attached to the substrate surface. This study demonstrates the preferential orientation of β-sheets within the secondary structure of protein layers, specifically anti-immunoglobulin G (anti-IgG) and bovine serum albumin (BSA), when physisorbed onto gold (Au) thin films. Using polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and infrared attenuated total reflection (IR-ATR) spectroscopy, it has been confirmed that the β-strands in these protein layers are tilted relative to the surface normal by average angles of 75.3° ± 0.4° for anti-IgG and of 79.3 ± 0.2° for BSA. These results are obtained by analyzing the orientation of the transition dipole moments (TDMs) associated with the amide I molecular vibrations derived from a comparison between experimental and simulated mid-infrared spectra assuming isotropically oriented TDMs. The simulations incorporate refractive and absorption index dispersions obtained from the IR-ATR spectra. Thus obtained findings offer valuable molecular-level insights facilitating the design and optimization of biofunctionalized interfaces in advanced biomedical and biosensing applications.

Original language	English
Number of pages	9
Journal	Advanced Materials Interfaces
Issue number	2400867
DOIs	https://doi.org/10.1002/admi.202400867
Publication status	Published - 16 Dec 2024
Externally published	Yes
MoE publication type	A1 Journal article-refereed

Funding

PNRR MUR project PE0000023-NQSTI – National Quantum Science and Technolgy Institute; MUR – Dipartimenti di Eccellenza 2023–2027 – Quantum Sensing and Modelling for One-Health (QuaSiModO), Centro di Innovazione Regionale Digital Assay, Regione PUGLIA Delibera Regionale n 702 del 08/11/2022 CUP B93C22000840001; NoOne-A binary sensor with single-molecule digit to discriminate biofluids enclosing zero or at least one biomarker, ERC Stg2021, GA:101040383; H2020 – Electronic Smart Systems – SiMBiT: Single-molecule bioelectronic smart system array for clinical testing (Grant agreement ID: 824946), PRIN project prot.2017RHX2E4 ″At the forefront of Analytical ChemisTry: disrUptive detection technoLogies to improve; Italian network of excellence for advanced diagnosis (INNOVA), Ministero della Salute -code PNC-E3-2022-23683266 PNC-HLS-DA, CUP: C43C22001630001; Complementary National Plan PNC-I.1 ″Research initiatives for innovative technologies and pathways in the health and welfare sector″ D.D. 931 of 06/06/2022, DARE – DigitAl lifelong pRevEntion initiative, code PNC0000002, CUP: B53C22006420001; Tecnologie portatili e protocolli innovativi per la diagnosi ultrasensibile di Xylella fastidiosa direttamente in piante e vettori (1LIVEXYLELLA) Ministero dell'agricoltura, della sovranità alimentare e delle foreste – MIPAAF D.M. n.419161 del 13/09/2022; Research actions for reducing the impact on agricultural and natural ecosystems of the harmful plant pathogen Xylella fastidiosa (REACH-XY) – CUP B93C22001920001 are acknowledged for partial financial support.

Keywords

Beta-sheet
Infrared attenuated total reflection spectroscopy
Molecular orientation
Polarization modulation infrared reflection absorption spectroscopy
Protein layers

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abstract = "Physisorption of antibodies onto surfaces is a low-cost, rapid, and effective approach for immobilizing bioreceptors in applications such as bioelectronic sensors. However, there is a prevailing notion that physisorbed protein layers lack structural order, thus potentially compromising their stability and sensitivity compared to antibody films that are covalently attached to the substrate surface. This study demonstrates the preferential orientation of β-sheets within the secondary structure of protein layers, specifically anti-immunoglobulin G (anti-IgG) and bovine serum albumin (BSA), when physisorbed onto gold (Au) thin films. Using polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and infrared attenuated total reflection (IR-ATR) spectroscopy, it has been confirmed that the β-strands in these protein layers are tilted relative to the surface normal by average angles of 75.3° ± 0.4° for anti-IgG and of 79.3 ± 0.2° for BSA. These results are obtained by analyzing the orientation of the transition dipole moments (TDMs) associated with the amide I molecular vibrations derived from a comparison between experimental and simulated mid-infrared spectra assuming isotropically oriented TDMs. The simulations incorporate refractive and absorption index dispersions obtained from the IR-ATR spectra. Thus obtained findings offer valuable molecular-level insights facilitating the design and optimization of biofunctionalized interfaces in advanced biomedical and biosensing applications.",

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β-Sheets Orientation in Physisorbed Protein Layers

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