Time-resolved cross-correlation spectroscopy with incoherent light for studying inter- and intramolecular processes

1995 ◽  
Author(s):  
Pavel A. Apanasevich ◽  
Valery P. Kozich ◽  
Valentin A. Orlovich ◽  
A. I. Vodchitz
Keyword(s):  
Cross Correlation ◽  
Correlation Spectroscopy ◽  
Incoherent Light ◽  
Time Resolved

scholarly journals Fluorescence Cross-Correlation Spectroscopy Yields True Affinity and Binding Kinetics of Plasmodium Lactate Transport Inhibitors

2021 ◽  
Vol 14 (8) ◽  
pp. 757
Author(s):  
Iga Jakobowska ◽  
Frank Becker ◽  
Stefano Minguzzi ◽  
Kerrin Hansen ◽  
Björn Henke ◽  
...  
Keyword(s):  
Rate Constants ◽  
Cross Correlation ◽  
Fluorescent Protein ◽  
Correlation Spectroscopy ◽  
Confocal Imaging ◽  
Binding Kinetics ◽  
Acceptor Site ◽  
Lactate Transport ◽  
Entry Site ◽  
Hydrogen Bond Acceptor

Blocking lactate export in the parasitic protozoan Plasmodium falciparum is a novel strategy to combat malaria. We discovered small drug-like molecules that inhibit the sole plasmodial lactate transporter, PfFNT, and kill parasites in culture. The pentafluoro-3-hydroxy-pent-2-en-1-one BH296 blocks PfFNT with nanomolar efficiency but an in vitro selected PfFNT G107S mutation confers resistance against the drug. We circumvented the mutation by introducing a nitrogen atom as a hydrogen bond acceptor site into the aromatic ring of the inhibitor yielding BH267.meta. The current PfFNT inhibitor efficiency values were derived from yeast-based lactate transport assays, yet direct affinity and binding kinetics data are missing. Here, we expressed PfFNT fused with a green fluorescent protein in human embryonic kidney cells and generated fluorescent derivatives of the inhibitors, BH296 and BH267.meta. Using confocal imaging, we confirmed the location of the proposed binding site at the cytosolic transporter entry site. We then carried out fluorescence cross-correlation spectroscopy measurements to assign true Ki-values, as well as kon and koff rate constants for inhibitor binding to PfFNT wildtype and the G107S mutant. BH296 and BH267.meta gave similar rate constants for binding to PfFNT wildtype. BH296 was inactive on PfFNT G107S, whereas BH267.meta bound the mutant protein albeit with weaker affinity than to PfFNT wildtype. Eventually, using a set of PfFNT inhibitor compounds, we found a robust correlation of the results from the biophysical FCCS binding assay to inhibition data of the functional transport assay.

Electron Correlation Microscopy: A New Technique for Studying Local Atom Dynamics Applied to a Supercooled Liquid

2015 ◽  
Vol 21 (4) ◽  
pp. 1026-1033 ◽  
Author(s):  
Li He ◽  
Pei Zhang ◽  
Matthew F. Besser ◽  
Matthew Joseph Kramer ◽  
Paul M. Voyles
Keyword(s):  
Electron Correlation ◽  
Supercooled Liquid ◽  
Scanning Transmission Electron Microscope ◽  
Correlation Spectroscopy ◽  
New Technique ◽  
Time Resolved ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
A New Technique ◽  
Correlation Microscopy

AbstractElectron correlation microscopy (ECM) is a new technique that utilizes time-resolved coherent electron nanodiffraction to study dynamic atomic rearrangements in materials. It is the electron scattering equivalent of photon correlation spectroscopy with the added advantage of nanometer-scale spatial resolution. We have applied ECM to a Pd40Ni40P20 metallic glass, heated inside a scanning transmission electron microscope into a supercooled liquid to measure the structural relaxation time τ between the glass transition temperature Tg and the crystallization temperature, Tx. τ determined from the mean diffraction intensity autocorrelation function g2(t) decreases with temperature following an Arrhenius relationship between Tg and Tg+25 K, and then increases as temperature approaches Tx. The distribution of τ determined from the g2(t) of single speckles is broad and changes significantly with temperature.

Assessing Convergence in Predictions of Periodic-Unsteady Flowfields

2006 ◽  
Author(s):  
J. P. Clark ◽  
E. A. Grover
Keyword(s):  
Cross Correlation ◽  
Unsteady Flows ◽  
Digital Signal ◽  
Design Decisions ◽  
Time Resolved ◽  
Design Engineers ◽  
Cross Correlations ◽  
Parseval’S Theorem ◽  
Hot Streak

Predictions of time-resolved flowfields are now commonplace within the gas-turbine industry, and the results of such simulations are often used to make design decisions during the development of new products. Hence it is necessary for design engineers to have a robust method to determine the level of convergence in design predictions. Here we report on a method developed to determine the level of convergence in a predicted flowfield that is characterized by periodic-unsteadiness. The method relies on fundamental concepts from digital signal processing including the discrete Fourier transform, cross-correlation, and Parseval’s theorem. Often in predictions of vane-blade interaction in turbomachines, the period of the unsteady fluctuations is expected. In this method, the development of time-mean quantities. Fourier components (both magnitude and phase), cross-correlations, and integrated signal power are tracked at locations of interest from one period to the next as the solution progresses. Each of these separate quantities yields some relative measure of convergence that is subsequently processed to form a fuzzy set. Thus the overall level of convergence in the solution is given by the intersection of these sets. Examples of the application of this technique to several predictions of unsteady flows from two separate solvers are given. These include a prediction of hot-streak migration as well as more typical cases. It is shown that the method yields a robust determination of convergence. Also, the results of the technique can guide further analysis and/or post-processing of the flowfield. Finally, the method is useful for the detection of inherent unsteadiness in the flowfield, and as such it can be used to prevent design escapes.

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