Optical imaging of single protein size, charge, mobility, binding and conformational change

Ma, Guangzhong; Zhu, Hao; Wang, Shaopeng; Yang, Yuanyuan; Wang, Shaopeng; Tao, Nongjian

doi:10.1101/505404

Cited by 2 publications

(2 citation statements)

References 22 publications

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“…For a given AuNP, the FFT image contrast measures the oscillation amplitude (Δ z ), which is related to the charge ( q ) of the AuNP according to where E is the amplitude of the alternating electric field and k is the effective spring constant of the PEG linker (Supporting Information, S3). Equation is valid only at low fields, where the oscillation amplitude is small compared to the PEG length. At a high electric field, the oscillation amplitude reaches a plateau as the PEG linker stretched to its maximum (Figure ).…”

Section: Resultsmentioning

confidence: 99%

Detection of Molecules and Charges with a Bright Field Optical Microscope

Zhu

Wan

et al. 2020

Anal. Chem.

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Charge is a fundamental property of a molecule, and precisely measuring it enables detection of the molecule and helps understand various chemical processes involving charge. Here we show a method to measure the charge of a single nanoparticle and binding of charged molecules to the nanoparticle using a conventional bright field optical microscope. The nanoparticle is tethered to an indium tin oxide surface with a polymer and driven into oscillation with an alternating electric field, which produces scattered light captured by a camera. The weak scattered light is separated from the intense bright field background using a Fourier transform filter, and the image contrast change provides the effective charge of the nanoparticle with precision of a few electron charges or less. This method allows us to detect DNA binding to the nanoparticles, demonstrating a simple method to detect and study molecules with a conventional optical microscope.

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Section: Resultsmentioning

confidence: 99%

Detection of Molecules and Charges with a Bright Field Optical Microscope

Zhu

Wan

et al. 2020

Anal. Chem.

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“…Figure c shows the oscillation amplitude of a nano-oscillator with and without applied field. By recording the nanoparticle-surface distance over 1 s and performing fast Fourier transform (FFT), the oscillation amplitude without modulation was measured to be 1.5 nm, corresponding to 7.5 electron charges according to eq . Considering the size of a nano-oscillator, the detection limit is ∼7.5 electrons per μm 2 , corresponding to 4.0 fg/mm 2 for small molecule 1 (Figure b), which is ∼25-fold better than traditional SPR (0.1 pg/mm 2 ) (Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Quantifying Ligand–Protein Binding Kinetics with Self-Assembled Nano-oscillators

Shan

Wang

et al. 2019

Anal. Chem.

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Measuring ligand–protein interactions is critical for unveiling molecular-scale biological processes in living systems and for screening drugs. Various detection technologies have been developed, but quantifying the binding kinetics of small molecules to the proteins remains challenging because the sensitivities of the mainstream technologies decrease with the size of the ligand. Here, we report a method to measure and quantify the binding kinetics of both large and small molecules with self-assembled nano-oscillators, each consisting of a nanoparticle tethered to a surface via long polymer molecules. By applying an oscillating electric field normal to the surface, the nanoparticle oscillates, and the oscillation amplitude is proportional to the number of charges on the nano-oscillator. Upon the binding of ligands onto the nano-oscillator, the oscillation amplitude will change. Using a plasmonic imaging approach, the oscillation amplitude is measured with subnanometer precision, allowing us to accurately quantify the binding kinetics of ligands, including small molecules, to their protein receptors. This work demonstrates the capability of nano-oscillators as an useful tool for measuring the binding kinetics of both large and small molecules.

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Optical imaging of single protein size, charge, mobility, binding and conformational change

Cited by 2 publications

References 22 publications

Detection of Molecules and Charges with a Bright Field Optical Microscope

Detection of Molecules and Charges with a Bright Field Optical Microscope

Quantifying Ligand–Protein Binding Kinetics with Self-Assembled Nano-oscillators

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