Single-Molecule Resonance Energy Transfer and Fluorescence Correlation Spectroscopy of Calmodulin in Solution†

2004 ◽  
Vol 108 (29) ◽  
pp. 10388-10397 ◽  
Author(s):  
Brian D. Slaughter ◽  
Michael W. Allen ◽  
Jay R. Unruh ◽  
Ramona J. Bieber Urbauer ◽  
Carey K. Johnson
Keyword(s):  
Energy Transfer ◽  
Single Molecule ◽  
Fluorescence Correlation Spectroscopy ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Correlation Spectroscopy ◽  
Fluorescence Correlation

Evidence that GPVI is Expressed as a Mixture of Monomers and Dimers, and that the D2 Domain is not Essential for GPVI Activation

2021 ◽  
Author(s):  
Joanne C. Clark ◽  
Raluca A. I. Neagoe ◽  
Malou Zuidscherwoude ◽  
Deirdre M. Kavanagh ◽  
Alexandre Slater ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Single Molecule ◽  
Fluorescence Correlation Spectroscopy ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Correlation Spectroscopy ◽  
Fluorescence Correlation ◽  
Glycoprotein Vi ◽  
D2 Domain ◽  
Microscopy Techniques

AbstractCollagen has been proposed to bind to a unique epitope in dimeric glycoprotein VI (GPVI) and the number of GPVI dimers has been reported to increase upon platelet activation. However, in contrast, the crystal structure of GPVI in complex with collagen-related peptide (CRP) showed binding distinct from the site of dimerization. Further fibrinogen has been reported to bind to monomeric but not dimeric GPVI. In the present study, we have used the advanced fluorescence microscopy techniques of single-molecule microscopy, fluorescence correlation spectroscopy (FCS) and bioluminescence resonance energy transfer (BRET), and mutagenesis studies in a transfected cell line model to show that GPVI is expressed as a mixture of monomers and dimers and that dimerization through the D2 domain is not critical for activation. As many of these techniques cannot be applied to platelets to resolve this issue, due to the high density of GPVI and its anucleate nature, we used Förster resonance energy transfer (FRET) to show that endogenous GPVI is at least partially expressed as a dimer on resting and activated platelet membranes. We propose that GPVI may be expressed as a monomer on the cell surface and it forms dimers in the membrane through diffusion, giving rise to a mixture of monomers and dimers. We speculate that the formation of dimers facilitates ligand binding through avidity.

scholarly journals Mechanism of DNA surface exploration and operator bypassing during target search

2020 ◽  
Author(s):  
E. Marklund ◽  
B. van Oosten ◽  
G. Mao ◽  
E. Amselem ◽  
K. Kipper ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Real Time ◽  
Single Molecule ◽  
Time Scale ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Fluorescence Signal ◽  
Target Search ◽  
Fluorescence Correlation ◽  
Speed Accuracy

SummaryMany proteins that bind specific DNA sequences search the genome by combining three dimensional (3D) diffusion in the cytoplasm with one dimensional (1D) sliding on non-specific DNA1–5. Here we combine resonance energy transfer and fluorescence correlation measurements to characterize how individual lac repressor (LacI) molecules explore DNA during the 1D phase of target search. To track the rotation of sliding LacI molecules on the microsecond time scale during DNA surface search, we use real-time single-molecule confocal laser tracking combined with fluorescence correlation spectroscopy (SMCT-FCS). The fluorescence signal fluctuations are accurately described by rotation-coupled sliding, where LacI traverses ~40 base pairs (bp) per revolution. This distance substantially exceeds the 10.5-bp helical pitch of DNA, suggesting that the sliding protein frequently hops out of the DNA groove, which would result in frequent bypassing of target sequences. Indeed, we directly observe such bypassing by single-molecule fluorescence resonance energy transfer (smFRET). A combined analysis of the smFRET and SMCT-FCS data shows that LacI at most hops one to two grooves (10-20 bp) every 250 μs. Overall, our data suggest a speed-accuracy trade-off during sliding; the weak nature of non-specific protein-DNA interactions underlies operator bypassing but also facilitates rapid sliding. We anticipate that our SMCT-FCS method to monitor rotational diffusion on the microsecond time scale while tracking individual molecules with millisecond time resolution will be applicable to the real-time investigation of many other biological interactions and effectively extends the accessible time regime by two orders of magnitude.

Monitoring the Structural Dynamics of U2 snRNA Via Single-Molecule Förster Resonance Energy Transfer

2018 ◽  
Author(s):  
Alexander Carl DeHaven
Keyword(s):  
Energy Transfer ◽  
Structural Dynamics ◽  
Single Molecule ◽  
Conformational Dynamics ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Förster Resonance Energy Transfer ◽  
U2 Snrna ◽  
Folding Dynamics ◽  
The Impact

This thesis contains four topic areas: a review of single-molecule microscropy methods and splicing, conformational dynamics of stem II of the U2 snRNA, the impact of post-transcriptional modifications on U2 snRNA folding dynamics, and preliminary findings on Mango aptamer folding dynamics.

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