Related Experiment Video
Updated: May 7, 2026
10:40
High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy
Published on: June 28, 2016
The spectroscopic ruler revisited at 77 K
Verena Hirschfeld1, Hauke Paulsen, Christian G Hübner
1University of Lübeck, Institute of Physics, Ratzeburger Allee 160, 23562 Lübeck, Germany. hirschfeld@physik.uni-luebeck.de.
Physical Chemistry Chemical Physics : PCCP
|September 18, 2013
Summary
Single-molecule FRET experiments on polyproline in amorphous ice reveal insights into molecular ruler behavior. Measured transfer efficiencies deviate from theoretical predictions, particularly at low efficiencies.
Area of Science:
- Biophysics
- Physical Chemistry
Background:
- Polyproline serves as a molecular ruler, a tool for measuring distances at the nanoscale.
- Understanding polymer behavior in non-crystalline environments is crucial for various applications.
Purpose of the Study:
- To investigate single-molecule Förster Resonance Energy Transfer (smFRET) in polyproline.
- To examine the influence of amorphous ice on polyproline conformation and FRET efficiency.
- To compare experimental results with theoretical simulations.
Main Methods:
- Single-molecule FRET measurements using confocal scanning microscopy.
- Utilizing Alexa Fluor 488 (donor) and Alexa Fluor 594 (acceptor) dyes.
- Experiments conducted on polyproline immersed in amorphous ice at 77 K.
Main Results:
- Observed broad distributions of transfer efficiencies due to fixed dipole orientations in amorphous ice.
- Experimental transfer efficiency distributions largely matched simulated distributions.
- A significant deviation was noted, with low transfer efficiencies absent in experimental data, contrary to theory.
Conclusions:
- Amorphous ice influences polyproline conformation and FRET efficiency.
- Current theoretical models may need refinement to fully explain experimental observations, especially concerning low transfer efficiencies.
Related Concept Videos
01:16IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
A covalently bonded heteronuclear diatomic molecule can be modeled as two vibrating masses connected by a spring. The vibrational frequency of the bond can be expressed using an equation derived from Hooke's law, which describes how the force applied to stretch or compress a spring is proportional to the displacement of the spring. In this case, the atoms behave like masses, and the bond acts like a spring.
According to Hooke's law, the vibrational frequency is directly proportional to the...
According to Hooke's law, the vibrational frequency is directly proportional to the...
01:29UV–Vis Spectroscopy: Woodward–Fieser Rules
UV–Visible absorption spectra of conjugated dienes arise from the lowest energy π → π* transitions. The light-absorbing part of the molecule is called the chromophore, and the substituents directly attached to the chromophore are called auxochromes. A strong correlation exists between the absorption maxima, λmax, and the structure of a conjugated π system. The Woodward–Fieser rules predict the value of λmax for a given structure by adding the contributions...
01:16UV–Vis Spectroscopy: Molecular Electronic Transitions
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this process,...
01:14Molecular Spectroscopy: Absorption and Emission
Molecules possess discrete energy levels called quantum states. Unlike atoms, which have simpler energy levels, molecules possess additional rotational and vibrational energy levels. Each energy level is separated by an energy gap, with the gaps between adjacent electronic, vibrational, and rotational levels varying significantly. The three types of energy levels in a diatomic molecule are shown in Figure 1.
01:27Atomic Spectroscopy: Effects of Temperature
Atomization, converting samples into gas-phase atoms and ions, is essential for atomic spectroscopy. The flame temperature required for atomization affects the efficiency of the atomic spectroscopic methods by increasing the atomization efficiency and the relative population of the excited and ground states.
At thermal equilibrium, the relative populations of excited and ground state atoms can be estimated using the Maxwell–Boltzmann distribution. For example, an increase in temperature from...
At thermal equilibrium, the relative populations of excited and ground state atoms can be estimated using the Maxwell–Boltzmann distribution. For example, an increase in temperature from...
01:09UV–Vis Spectroscopy: Beer–Lambert Law
The Beer-Lambert law describes the relationship between absorbance and concentration, which combines the principles established by scientists Johann Heinrich Lambert and August Beer. Lambert's law states that when light passes through a medium, the loss in intensity is directly proportional to the original intensity and the path length of the light. Beer's law proposed that the transmittance of a solution remains constant if the product of concentration and path length is constant. The modern...