Stopped Flow Spectrofluorimetry
Stopped Flow Spectrofluorimetry - Related Videos
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Developing a Cerebral Blood Flow Atlas for Blood Flow Mapping
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Source: Tan, Z., et al., Construction and Application of Cerebral Functional Region-Based Cerebral Blood Flow Atlas Using Magnetic Resonance Imaging-Arterial Spin Labeling. J. Vis. Exp. (2024).This video demonstrates the method to construct a cerebral blood flow atlas by integrating magnetic resonance imaging or MRI-arterial spin labeling data with segmented brain regions, visualizing blood flow patterns, and quantifying flow levels across functional areas.
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Measuring Turbulent Flows
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Source: Ricardo Mejia-Alvarez and Hussam Hikmat Jabbar, Department of Mechanical Engineering, Michigan State University, East Lansing, MI Turbulent flows exhibit very high frequency fluctuations that require instruments with high time-resolution for their appropriate characterization. Hot-wire anemometers have a short enough time-response to fulfill this requirement. The purpose of this experiment is to demonstrate the use of hot-wire anemometry to characterize a turbulent jet. In this...
FAQs
The critical measurement begins immediately after mixing. Reactants are driven into an observation cell, and the flow is halted so fluorescence can be followed without continued displacement of the sample. Excitation and emission are recorded as a time-dependent trace, preserving kinetic information that could be obscured when measurements are collected only at separated manual time points.
Fluorescence traces are interpreted as changes over time rather than single intensity values. Their shape and time dependence can be analyzed to estimate reaction rates and identify transitions associated with conformational changes, binding events, or intermediate states. This analysis links an optical signal to both the speed and molecular character of the process being studied.
Fluorescent molecules or probes provide the signal that can be tracked after mixing. Their time-dependent emission gives the experiment a way to monitor molecular behavior as it develops, rather than relying only on a final observation. In biological studies, this supports analysis of binding, conformational rearrangements, and reaction progress on rapid timescales.
Stopped Flow Spectrofluorimetry is most valuable when a biological event occurs too quickly for conventional, manually sampled measurements. Manual sampling produces observations at separated time points, whereas the stopped-flow fluorescence trace follows changes immediately after mixing. This distinction enables researchers to characterize rapid processes that might otherwise be missed between sampling intervals.
A typical experiment drives two or more solutions into an observation cell, mixes them rapidly, and halts the flow. Excitation light is then applied to fluorescent molecules or probes, while emitted light is collected over time. The resulting fluorescence trace is analyzed for reaction rates, molecular transitions, binding events, or intermediate states.
Applications include enzyme catalysis, protein folding, ligand interactions, and nucleic-acid processes. Across these systems, the method can reveal how rapidly a reaction proceeds, whether binding or structural changes occur, and whether transient intermediate states appear. These measurements help characterize molecular behavior in biological systems rather than recording only a starting and ending condition.