Related Experiment Video
Updated: Dec 30, 2025
11:03
How to Quantify the Fraction of Photoactivated Fluorescent Proteins in Bulk and in Live Cells
Published on: January 7, 2019
7.0K
Variable fluorescence of closed photochemical reaction centers
1Institute of Technology, University of Tartu, Nooruse st. 1, 50411, Tartu, Estonia. agu.laisk@ut.ee.
Photosynthesis Research
|January 22, 2020
Summary
This study reveals that the quantum yield of oxygen evolution in Photosystem II (PSII) remains constant even as adjacent centers close during light induction. An electric field aids excitation energy transfer, explaining fluorescence changes in closed centers.
Area of Science:
- Plant Physiology
- Photosynthesis Research
- Biophysics
Background:
- Understanding chlorophyll fluorescence induction is crucial for assessing photosynthetic efficiency.
- Photosystem II (PSII) photochemistry dynamics are complex and influenced by light intensity and antenna interactions.
Purpose of the Study:
- To investigate the quantum yield of oxygen evolution during multiple-turnover pulse (MTP) induction.
- To correlate oxygen evolution with the number of open PSII centers and analyze fluorescence changes.
Main Methods:
- Measurement of chlorophyll fluorescence induction using MTP (0.4–200 ms).
- Parallel measurement of O2 evolution induced by MTP and saturating single-turnover flashes (STF).
- Calculation of quantum yield and determination of open PSII centers.
Main Results:
- A direct proportionality was observed between the number of open PSII centers and their photochemical activity.
- The quantum yield of open PSII remained constant, irrespective of adjacent center closure.
- Fluorescence yield of closed centers increased during induction, approaching Fm, explained by an electric field facilitating energy transfer.
Conclusions:
- The quantum yield of open PSII centers is stable during light induction.
- An electric field within the antenna/radical pair equilibrium model explains fluorescence rise in closed centers.
- This provides insights into energy transfer mechanisms and PSII regulation under changing light conditions.
More Related Videos
Related Concept Videos
01:29The Photochemical Reaction Center
5.1K
Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...
5.1K
01:26Variables Affecting Phosphorescence and Fluorescence
1.2K
Fluorescence and phosphorescence are essential phenomena in fields like analytical chemistry, biological imaging, and materials science, where they detect molecular properties and visualize cellular structures. Understanding the variables that influence these luminescent behaviors is crucial for maximizing accuracy and efficiency in their applications. These variables can broadly be grouped into chemical structure, solvent properties, and external conditions, each playing a distinct role in...
1.2K
01:15The Antenna Complex
7.4K
Plants and other photosynthetic organisms comprise pigments capable of absorption of direct sunlight. These pigments are present in the reaction center - the main site of photochemical reactions as well as in the antenna complex. Under average light conditions, the rate at which reaction center pigments absorb light is far below the electron transport chain's capacity. As a result, the reaction center alone cannot provide enough energy to drive photosynthesis. The photosynthetic efficiency can...
7.4K
01:37Super-resolution Fluorescence Microscopy
12.1K
Super-resolution fluorescence microscopy (SRFM) provides a better resolution than conventional fluorescence microscopy by reducing the point spread function (PSF). PSF is the light intensity distribution from a point that causes it to appear blurred. Due to PSF, each fluorescing point appears bigger than its actual size, and it is the PSF interference of nearby fluorophores that causes the blurred image. Various approaches to achieving higher resolution through SRFM have recently been...
12.1K
01:23Photoluminescence: Fluorescence and Phosphorescence
3.3K
Photoluminescence is a process where a molecule absorbs light energy and re-emits it in the form of light. This phenomenon occurs when a substance absorbs photons, promoting its electrons to higher energy level excited states, followed by a relaxation process in which the electrons return to their original ground state energy levels and emit light. Photoluminescence is widely observed in various materials, including semiconductors, and organic and inorganic compounds.
A pair of electrons in a...
A pair of electrons in a...
3.3K
01:25Fluorescence and Phosphorescence: Instrumentation
1.3K
Fluorometers and spectrofluorometers are two types of instruments used for measuring molecular fluorescence. These instruments differ in how they select excitation and emission wavelengths and the type of light sources they utilize. Fluorometers use absorption interference filters to choose excitation and emission wavelengths. The excitation source in a fluorometer is typically a low-pressure mercury vapor lamp that emits intense lines distributed throughout the ultraviolet and visible regions.
1.3K