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Non-photochemical quenching (NPQ) is a mechanism employed by plants and algae to protect themselves from the adverse effects of high light intensity.It involves the quenching of singlet excited state chlorophylls (Chl) via enhanced internal conversion to the ground state (non-radiative decay), thus harmlessly dissipating excess excitation energy as heat through molecular vibrations.
This light (preferably near infrared frequency as this allows for the penetration of the skin without acute toxicity) excites the photosensitizer's electrons into the triplet state. Upon excitation, the photosensitizer begins transferring energy to neighboring ground state triplet oxygen to generate excited singlet oxygen. The resulting excited ...
Examples of atoms in singlet, doublet, and triplet states. In quantum mechanics, a triplet state, or spin triplet, is the quantum state of an object such as an electron, atom, or molecule, having a quantum spin S = 1. It has three allowed values of the spin's projection along a given axis m S = −1, 0, or +1, giving the name "triplet".
In a triplet state the excited electron is no longer paired with the ground state electron; that is, they are parallel (same spin). Since excitation to a triplet state involves an additional "forbidden" spin transition, it is less probable that a triplet state will form when the molecule absorbs radiation. Singlet and triplet energy levels.
Excited triplet-state photosensitisers can react via Type-I and Type-II processes. Type-I processes can involve the excited singlet or triplet photosensitiser (1Psen*, S1; 3Psen*, T1), however due to the short lifetime of the excited singlet state, the photosensitiser can only react if it is intimately associated with a substrate.
Upon absorption of light, carotenoids transfer excitation energy to and from chlorophyll. The singlet-singlet energy transfer is a lower energy state transfer and is used during photosynthesis. [7] The triplet-triplet transfer is a higher energy state and is essential in photoprotection. [7]
The result are multiple following reactions. First triplet-state chlorophyll reacts with oxygen to form singlet oxygen. Both chlorophyll and singlet oxygen then remove hydrogen ions from the unsaturated lipids present in de cells and the organelle membranes, forming lipid radicals. These radicals will oxidize other lipids and proteins ...
Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. [2] Its name is derived from the Greek words χλωρός (khloros, "pale green") and φύλλον (phyllon, "leaf"). [3] Chlorophyll allows plants to absorb energy from light.
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