Tag Archive for: flow cell

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Quartz crystal microbalance with dissipation monitoring for studying soft matter at interfaces

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Authors: Diethelm Johannsmann & Ilya Reviakine

Journal: Nature Reviews Methods Primers

Abstract: Quartz crystal microbalance with dissipation monitoring (QCM-D) probes interfaces by subjecting them to a periodic shear stress exerted by an acoustic resonator. The changes in the resonance frequency, Δf, and the half-width at half-maximum of the resonance, ΔΓ (closely related to the changes in the dissipation, ΔD), measured with the QCM-D are proportional to the in-phase and out-of-phase components of the area-averaged transverse stress at the resonator surface, respectively. Amounts, organization and properties of soft matter at an interface between the resonator and a liquid or a gas are derived from the measurements of Δf and ΔΓ on multiple overtones at megahertz frequencies. The properties include viscoelasticity and stress relaxation dynamics on the timescale of the oscillation period. This Primer offers guidelines on instrument design, experimental procedures and data analysis for interpreting frequency and bandwidth changes in terms of structure and dynamics of the sample. There is a focus on recent progress in the analysis of the acoustic ratio, ΔΓ/(−Δf), and numerical methods of modelling. Limitations of the existing approaches for data analysis are discussed. Challenges and possible future developments are formulated in an outlook.

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C60-based Multivalent Glycoporphyrins Inhibit SARS-CoV-2 Specific Interaction with the DC-SIGN Transmembrane Receptor

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Authors: Jennifer Patino-Alonso, Justo Cabrera-González, Javier Merino, Gema Nieto-Ortiz, Fátima Lasala, Jouma Katati, Carlos H. Bezerra da Cruz, Ajay K. Monnappa, Pablo Mateos-Gil, Ángeles Canales, Iván López-Montero, Beatriz M. Illescas, Rafael Delgado, and Nazario Martín

Journal: Small (2023)

 

Abstract

Since WHO has declared the COVID-19 outbreak a global pandemic, nearly seven million deaths have been reported. This efficient spread of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is facilitated by the ability of the spike glycoprotein to bind multiple cell membrane receptors. Although ACE2 is identified as the main receptor for SARS-CoV-2, other receptors could play a role in viral entry. Among others, C-type lectins such as DC-SIGN are identified as efficient trans-receptor for SARS-CoV-2 infection, so the use of glycomimetics to inhibit the infection through the DC-SIGN blockade is an encouraging approach. In this regard, multivalent nanostructures based on glycosylated [60]fullerenes linked to a central porphyrin scaffold have been designed and tested against DC-SIGN-mediated SARS-CoV-2 infection. First results show an outstanding inhibition of the trans-infection up to 90%. In addition, a deeper understanding of nanostructure-receptor binding is achieved through microscopy techniques, high-resolution NMR experiments, Quartz Crystal Microbalance experiments, and molecular dynamic simulations.

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Surface Acoustic Wave Immunosensor for Detection of Botulinum Neurotoxin

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Authors: Michał Grabka, Krzysztof Jasek and Zygfryd Witkiewicz

Journal: Sensors (2023)

 

Abstract

A Love-type acoustic wave sensor (AT-cut quartz substrate, SiO2 guiding layer) with a center frequency of approximately 120 MHz was used to detect a simulant of pathogenic botulinum neurotoxin type A—recombinant of BoNT-A light chain—in liquid samples. The sensor was prepared by immobilizing monoclonal antibodies specific for botulinum neurotoxin via a thiol monolayer deposited on a gold substrate. Studies have shown that the sensor enables selective analyte detection within a few minutes. In addition, the sensor can be used several times (regeneration of the sensor is possible using a low pH buffer). Nevertheless, the detectability of the analyte is relatively low compared to other analytical techniques that can be used for rapid detection of botulinum neurotoxin. The obtained results confirm the operation of the proposed sensor and give hope for further development of this label-free technique for detecting botulinum neurotoxin.

Surface Acoustic Wave (Love-SAW) immunosensor for detection of botulinum neurotoxin. Source: Sensors 2023, 23(18), 7688

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Modifying last layer in polyelectrolyte multilayer coatings for capillary electrophoresis of proteins

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Authors: Sébastien Roca, Laurent Leclercq, Philippe Gonzalez, Laura Dhellemmes, Laurent Boiteau, Gaulthier Rydzek, and Hervé Cottet

Journal: Journal of Chromatography A (2023)

 

Abstract

Protein adsorption on the inner wall of the fused silica capillary wall is an important concern for capillary electrophoresis (CE) analysis since it is mainly responsible for separation efficiency reduction. Successive Multiple Ionic-polymer Layers (SMIL) are used as capillary coatings to limit protein adsorption, but even low residual adsorption strongly impacts the separation efficiency, especially at high separation voltages. In this work, the influence of the chemical nature and the PEGylation of the polyelectrolyte deposited in the last layer of the SMIL coating was investigated on the separation performances of a mixture of four model intact proteins (myoglobin (Myo), trypsin inhibitor (TI), ribonuclease a (RNAse A) and lysozyme (Lyz)). Poly(allylamine hydrochloride) (PAH), polyethyleneimine (PEI), ε-poly(L-lysine) (εPLL) and α-poly(L-lysine) (αPLL) were compared before and after chemical modification with polyethyleneglycol (PEG) of different chain lengths. The experimental results obtained by performing electrophoretic separations at different separation voltages allowed determining the residual retention factor of the proteins onto the capillary wall via the determination of the plate height at different solute velocities and demonstrated a strong impact of the polycationic last layer on the electroosmotic mobility, the separation efficiency and the overall resolution. Properties of SMIL coatings were also characterized by quartz microbalance and atomic force microscopy, demonstrating a glassy structure of the films.

 

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Nanoporous Metal–Organic Framework Thin Films Prepared Directly from Gaseous Precursors by Atomic and Molecular Layer Deposition: Implications for Microelectronics

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Authors: Jenna Multia, Dmitry E. Kravchenko, Víctor Rubio-Giménez, Anish Philip, Rob Ameloot, and Maarit Karppinen

Journal: ACS Appl. Nano Mater. (2023)

 

Abstract

Atomic/molecular layer deposition (ALD/MLD) allows for the direct gas-phase synthesis of crystalline metal–organic framework (MOF) thin films. Here, we show for the first time using krypton and methanol physisorption measurements that ALD/MLD-fabricated copper 1,4-benzenedicarboxylate (Cu-BDC) ultrathin films possess accessible porosity matching that of the corresponding bulk MOF.

 

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V. cholerae MakA is a cholesterol-binding pore-forming toxin that induces non-canonical autophagy

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Authors: Xiaotong Jia, Anastasia Knyazeva, Yu Zhang, Sergio Castro-Gonzalez, Shuhei Nakamura, Lars-Anders Carlson, Tamotsu Yoshimori, Dale P. Corkery, Yao-Wen Wu

Journal: J Cell Biol (2022)

 

Abstract

Pore-forming toxins (PFTs) are important virulence factors produced by many pathogenic bacteria. Here, we show that the Vibrio cholerae toxin MakA is a novel cholesterol-binding PFT that induces non-canonical autophagy in a pH-dependent manner. MakA specifically binds to cholesterol on the membrane at pH < 7. Cholesterol-binding leads to oligomerization of MakA on the membrane and pore formation at pH 5.5. Unlike other cholesterol-dependent cytolysins (CDCs) which bind cholesterol through a conserved cholesterol-binding motif (Thr-Leu pair), MakA contains an Ile-Ile pair that is essential for MakA-cholesterol interaction. Following internalization, endosomal acidification triggers MakA pore-assembly followed by ESCRT-mediated membrane repair and V-ATPase-dependent unconventional LC3 lipidation on the damaged endolysosomal membranes. These findings characterize a new cholesterol-binding toxin that forms pores in a pH-dependent manner and reveals the molecular mechanism of host autophagy manipulation.

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Aerosol Jet Printing of the Ultramicroporous Calcium Squarate Metal–Organic Framework

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Authors: Dmitry E. Kravchenko, Aleksander Matavž, Víctor Rubio-Giménez, Hanne Vanduffel, Margot Verstreken, Rob Ameloot

Journal: Chem. Mater. (2022)

 

Abstract

Efficient methods to deposit thin layers of metal–organic frameworks (MOFs) are needed to integrate these microporous materials into microelectronics, sensing devices, and membranes. Herein, we report for the first time the direct aerosol jet printing of a MOF material. The ultramicroporous MOF [Ca(C4O4) (H2O)] (UTSA-280) was deposited from an aqueous precursor solution. In addition to blanket coatings, aerosol jet printing provides direct access to patterned coatings with a resolution of 100 μm via a digital, maskless approach. Moreover, by enabling spatial control over the layer thickness via the number of passes of the nozzle, this direct-write approach presents a more accessible alternative to advanced patterning techniques such as grayscale lithography.

 

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Membrane insertion mechanism of the caveola coat protein Cavin1

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Authors: Liu, K.-C., Pace, H., Larsson, E., Hossain, S., Kabedev, A., Shukla, A., Jerschabek, V., Mohan, J., Bergström, C. A. S., Bally, M., Schwieger, C., Hubert, M., & Lundmark, R.

Journal: PNAS (2022)

 

Abstract

Caveolae are small plasma membrane invaginations, important for control of membrane tension, signaling cascades, and lipid sorting. The caveola coat protein Cavin1 is essential for shaping such high curvature membrane structures. Yet, a mechanistic understanding of how Cavin1 assembles at the membrane interface is lacking. Here, we used model membranes combined with biophysical dissection and computational modeling to show that Cavin1 inserts into membranes. We establish that initial phosphatidylinositol (4, 5) bisphosphate [PI(4,5)P2]–dependent membrane adsorption of the trimeric helical region 1 (HR1) of Cavin1 mediates the subsequent partial separation and membrane insertion of the individual helices. Insertion kinetics of HR1 is further enhanced by the presence of flanking negatively charged disordered regions, which was found important for the coassembly of Cavin1 with Caveolin1 in living cells. We propose that this intricate mechanism potentiates membrane curvature generation and facilitates dynamic rounds of assembly and disassembly of Cavin1 at the membrane.

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