Search results for "Single-molecule experiment"

Studying RNA Using Single Molecule Fluorescence Resonance Energy Transfer

2014

GFP-mut2 Proteins in Trehalose-Water Matrixes: Spatially Heterogeneous Protein-Water-Sugar Structures

2007

We report investigations on the properties of nanoenvironments around single-GFP-mut2 proteins in trehalose-water matrixes. Single-GFPmut2 molecules embedded in thin trehalose-water films were characterized in terms of their fluorescence brightness, bleaching dynamics, excited state lifetime, and fluorescence polarization. For each property, sets of approximately 100-150 single molecules have been investigated as a function of trehalose content and hydration. Three distinct and interconverting families of proteins have been found which differ widely in terms of bleaching dynamics, brightness, and fluorescence polarization, whose relative populations sizably depend on sample hydration. The r…

Protein Conformational Landscapes and Catalysis. Influence of Active Site Conformations in the Reaction Catalyzed by L-Lactate Dehydrogenase

2015

In the past decade, L-Lactate Dehydrogenase (LDH) has become an extremely useful marker in both clinical diagnosis and in monitoring the course of many human diseases. It has been assumed since the 1980s that the full catalytic process of LDH starts with the binding of the cofactor and the substrate followed by the enclosure of the active site by a mobile loop of the protein before the reaction takes place. In this paper, we show that the chemical step of the LDH-catalyzed reaction can proceed within the open loop conformation, and the different reactivity of the different protein conformations would be in agreement with the broad range of rate constants measured in single-molecule spectrom…

Rotational Correlation Functions of Single Molecules

2004

Single molecule rotational correlation functions are analyzed for several reorientation geometries. Even for the simplest model of isotropic rotational diffusion our findings predict non-exponential correlation functions to be observed by polarization sensitive single molecule fluorescence microscopy. This may have a deep impact on interpreting the results of molecular reorientation measurements in heterogeneous environments.

Statistical analysis of time resolved single molecule fluorescence data without time binning

2010

We depict two algorithms to calculate correlation functions from two different time resolved single molecule fluorescence experiments without the need of time binning. Our first procedure allows to calculate the reduced linear dichroism from polarization resolved fluorescence data. Since we process single photon counts instead of time binned data, considerably faster fluctuations of the dichroism can be analyzed than with conventional methods. With our second procedure time resolved fluorescence obtained with a time correlated single photon counting setup can be analyzed with respect to fluorescence lifetime fluctuations. Again this new algorithm processes single photon events making time b…

Demonstration of Single-Barium-Ion Sensitivity for Neutrinoless Double-Beta Decay Using Single-Molecule Fluorescence Imaging

2018

[EN] A new method to tag the barium daughter in the double-beta decay of Xe-136 is reported. Using the technique of single molecule fluorescent imaging (SMFI), individual barium dication (Ba++) resolution at a transparent scanning surface is demonstrated. A single-step photobleach confirms the single ion interpretation. Individual ions are localized with superresolution (similar to 2 nm), and detected with a statistical significance of 12.9 sigma over backgrounds. This lays the foundation for a new and potentially background-free neutrinoless double-beta decay technology, based on SMFI coupled to high pressure xenon gas time projection chambers.

Force-clamp spectroscopy of reversible bond breakage.

2008

We consider reversible breaking of adhesion bonds or folding of proteins under the influence of a constant external force. We discuss the stochastic properties of the unbinding/rebinding events and analyze their mean number and their variance in the framework of simple two-state models. In the calculations, we exploit the analogy to single molecule fluorescence and particularly between unbinding/rebinding and photon emission events. Environmental fluctuation models are used to describe deviations from Markovian behavior. The second moment of the event-number distribution is found to be very sensitive to possible exchange processes and can thus be used to identify temporal fluctuations of th…

Photoblinking and photobleaching of rylene diimide dyes.

2010

We investigate photoblinking and photobleaching of perylene diimide (PDI) and its higher homologue terrylene diimide (TDI). Single molecule fluorescence trajectories of the dye molecules embedded in PMMA under ambient conditions exhibit "on"-"off" blinking in the time range from ms to s. Due to the limited statistics of individual trajectories we construct ensemble distributions of "on" and "off" times which follow power laws with similar power law coefficients (m(on) ≈ 1.18, m(off) ≈ 1.31). The blinking is attributed to reversible formation of radical cations which are presumably created by electron transfer from higher excited triplet states T(n) of the molecules to acceptor levels in the…