scholarly journals Direct Measurement of the Affinity between tBid and Bax in a Mitochondria-like Membrane

2021 ◽  
Vol 22 (15) ◽  
pp. 8240
Author(s):  
Markus Rose ◽  
Martin Kurylowicz ◽  
Mohammad Mahmood ◽  
Sheldon Winkel ◽  
Jose M. Moran-Mirabal ◽  
...  
Keyword(s):  
Single Particle ◽  
Lipid Membrane ◽  
Molecular Model ◽  
Supported Lipid Bilayer ◽  
Cross Correlation Analysis ◽  
Particle Level ◽  
Order Of Magnitude ◽  
Physical Interactions ◽  
Transient Interactions ◽  
Multiple Conformations

The execution step in apoptosis is the permeabilization of the outer mitochondrial membrane, controlled by Bcl-2 family proteins. The physical interactions between the different proteins in this family and their relative abundance literally determine the fate of the cells. These interactions, however, are difficult to quantify, as they occur in a lipid membrane and involve proteins with multiple conformations and stoichiometries which can exist both in soluble and membrane. Here we focus on the interaction between two core Bcl-2 family members, the executor pore-forming protein Bax and the truncated form of the activator protein Bid (tBid), which we imaged at the single particle level in a mitochondria-like planar supported lipid bilayer. We inferred the conformation of the proteins from their mobility, and detected their transient interactions using a novel single particle cross-correlation analysis. We show that both tBid and Bax have at least two different conformations at the membrane, and that their affinity for one another increases by one order of magnitude (with a 2D-KD decreasing from ≃1.6/m2 to ≃0.1/m2) when they pass from their loosely membrane-associated to their transmembrane form. We conclude by proposing an updated molecular model for the activation of Bax by tBid.

Colloidal Plasmonic Nanostar Antennas with Wide Range Resonance Tunability

2019 ◽  
Author(s):  
Theodoros Tsoulos ◽  
Supriya Atta ◽  
Maureen Lagos ◽  
Michael Beetz ◽  
Philip Batson ◽  
...  
Keyword(s):  
Single Particle ◽  
Structural Complexity ◽  
Field Enhancement ◽  
Hot Electron ◽  
Structure Property ◽  
Plasmon Band ◽  
Gold Nanostars ◽  
Wide Range ◽  
Particle Level ◽  
Spectrally Resolved

<div>Gold nanostars display exceptional field enhancement properties and tunable resonant modes that can be leveraged to create effective imaging tags or phototherapeutic agents, or to design novel hot-electron based photocatalysts. From a fundamental standpoint, they represent important tunable platforms to study the dependence of hot carrier energy and dynamics on plasmon band intensity and position. Toward the realization of these platforms, holistic approaches taking into account both theory and experiments to study the fundamental behavior of these</div><div>particles are needed. Arguably, the intrinsic difficulties underlying this goal stem from the inability to rationally design and effectively synthesize nanoparticles that are sufficiently monodispersed to be employed for corroborations of the theoretical results without the need of single particle experiments. Herein, we report on our concerted computational and experimental effort to design, synthesize, and explain the origin and morphology-dependence of the plasmon modes of a novel gold nanostar system, with an approach that builds upon the well-known plasmon hybridization model. We have synthesized monodispersed samples of gold nanostars with finely tunable morphology employing seed-mediated colloidal protocols, and experimentally observed narrow and spectrally resolved harmonics of the primary surface plasmon resonance mode both at the single particle level (via electron energy loss spectroscopy) and in ensemble (by UV-Vis and ATR-FTIR spectroscopies). Computational results on complex anisotropic gold nanostructures are validated experimentally on samples prepared colloidally, underscoring their importance as ideal testbeds for the study of structure-property relationships in colloidal nanostructures of high structural complexity.</div>

scholarly journals Role of Single-Particle Energies in Microscopic Interacting Boson Model Double Beta Decay Calculations

Universe ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 66
Author(s):  
Jenni Kotila
Keyword(s):  
Beta Decay ◽  
Single Particle ◽  
Field Potential ◽  
Double Beta Decay ◽  
Interacting Boson Model ◽  
Model Calculations ◽  
Single Particle Level ◽  
Particle Level ◽  
Boson Model

Single-particle level energies form a significant input in nuclear physics calculations where single-particle degrees of freedom are taken into account, including microscopic interacting boson model investigations. The single-particle energies may be treated as input parameters that are fitted to reach an optimal fit to the data. Alternatively, they can be calculated using a mean field potential, or they can be extracted from available experimental data, as is done in the current study. The role of single-particle level energies in the microscopic interacting boson model calculations is discussed with special emphasis on recent double beta decay calculations.

Single-Particle Identification of Encoded Nanospheres

2010 ◽  
Vol 15 (2) ◽  
pp. 218-223 ◽  
Author(s):  
Hendrik Hippchen ◽  
Wiebke H. Pohl ◽  
Peter J. Walla
Keyword(s):  
Single Particle ◽  
Correlation Spectroscopy ◽  
Particle Identification ◽  
Carbohydrate Binding ◽  
Binding Affinities ◽  
Focal Volume ◽  
Receptor Ligand ◽  
Ligand Interactions ◽  
Particle Level ◽  
20 Nm

Recently, it has been shown that 2-photon fluorescence correlation spectroscopy of single glycosylated 20-nm fluorescent spheres allows measurement of the relative carbohydrate binding affinities of unlabeled proteins and that these modified spheres can mimic the glycocalix of cell or virus surfaces. An especially useful extension would be the analysis of mixtures of nanospheres that each contain different fluorescent labels and are thus differentially “encoded.” If the surfaces of these encoded nanospheres are modified with various receptors, many different biomolecule-surface interactions and concurrent reactions can be measured quickly and simultaneously in a single-reaction vessel. An essential prerequisite for this general assay principle is the ability to identify with an accuracy of nearly 100% any encoded nanosphere present in a mixture on a single-particle level. Here the authors present a method that indeed allows certain identification of differently encoded nanospheres during single transits through the focal volume of a microscope objective (ø~200-500 nm) in aqueous solution. This opens the way for using the encoded nanospheres in 1-well measurements of a large variety of biomolecular receptor-ligand interactions, inhibition and concurrent reactions, and thus either for testing the behavior of ligands in a mimicked complex biomolecular environment or for a fast simultaneous measurement of a multitude of receptor-ligand interactions.

The influence of diffusion phenomena on catalysis: A study at the single particle level using fluorescence microscopy

2010 ◽  
Vol 157 (1-4) ◽  
pp. 236-242 ◽  
Author(s):  
Gert De Cremer ◽  
Evelyne Bartholomeeusen ◽  
Paolo P. Pescarmona ◽  
Kaifeng Lin ◽  
Dirk E. De Vos ◽  
...  
Keyword(s):  
Fluorescence Microscopy ◽  
Single Particle ◽  
Single Particle Level ◽  
Particle Level ◽  
Diffusion Phenomena

scholarly journals Local Substrate Heterogeneity Influences Electrochemical Activity of TEM Grid-Supported Battery Particles

2021 ◽  
Vol 9 ◽  
Author(s):  
Christina Cashen ◽  
R. Colby Evans ◽  
Zach N. Nilsson ◽  
Justin B. Sambur
Keyword(s):  
Single Particle ◽  
Electrochemical Behavior ◽  
Electrochemical Activity ◽  
Ex Situ ◽  
Structure Property ◽  
Structure Property Relationships ◽  
Single Particle Level ◽  
Particle Level ◽  
Tem Grid ◽  
Ion Insertion

Understanding how particle size and morphology influence ion insertion dynamics is critical for a wide range of electrochemical applications including energy storage and electrochromic smart windows. One strategy to reveal such structure–property relationships is to perform ex situ transmission electron microscopy (TEM) of nanoparticles that have been cycled on TEM grid electrodes. One drawback of this approach is that images of some particles are correlated with the electrochemical response of the entire TEM grid electrode. The lack of one-to-one electrochemical-to-structural information complicates interpretation of genuine structure/property relationships. Developing high-throughput ex situ single particle-level analytical techniques that effectively link electrochemical behavior with structural properties could accelerate the discovery of critical structure-property relationships. Here, using Li-ion insertion in WO3 nanorods as a model system, we demonstrate a correlated optically-detected electrochemistry and TEM technique that measures electrochemical behavior of via many particles simultaneously without having to make electrical contacts to single particles on the TEM grid. This correlated optical-TEM approach can link particle structure with electrochemical behavior at the single particle-level. Our measurements revealed significant electrochemical activity heterogeneity among particles. Single particle activity correlated with distinct local mechanical or electrical properties of the amorphous carbon film of the TEM grid, leading to active and inactive particles. The results are significant for correlated electrochemical/TEM imaging studies that aim to reveal structure-property relationships using single particle-level imaging and ensemble-level electrochemistry.

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