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Photoreceptors and Plant Responses to Light02:00

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Light plays a significant role in regulating the growth and development of plants. In addition to providing energy for photosynthesis, light provides other important cues to regulate a range of developmental and physiological responses in plants.
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The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
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At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category,...
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Spectroscopic Analyses of Photoconversion in Phytochromes.

Chengwei Yi1, Stefanie S M Meier1, Maria Kehr1

  • 1Department of Biochemistry, University of Bayreuth, Bayreuth, Germany.

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|October 1, 2025
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Summary

Phytochrome photoreceptors sense light quality to regulate plant and microbial life. This study details absorption spectroscopy methods to quantify phytochrome

Keywords:
BilinChromophoreOptogeneticsPhotobiologyPhotoreceptorPhytochromeQuantum yieldSpectroscopy

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Area of Science:

  • Photochemistry
  • Molecular Biology
  • Spectroscopy

Background:

  • Phytochrome photoreceptors are crucial for sensing red and far-red light, influencing plant, bacterial, and fungal adaptations.
  • Phytochromes cycle between Pr and Pfr states upon light exposure, a process critical for biological responses.

Purpose of the Study:

  • To provide detailed protocols for analyzing phytochrome properties using absorption spectroscopy.
  • To determine key photochemical parameters: molar extinction coefficients, photostationary states, and quantum yields.

Main Methods:

  • Absorption spectroscopy protocols are presented for phytochrome analysis.
  • Methods focus on quantifying molar extinction coefficients and photostationary states under illumination.
  • Quantum yields for the light-driven Pr ⇄ Pfr interconversion are determined.

Main Results:

  • Established protocols for precise measurement of phytochrome photochemical parameters.
  • Quantified molar extinction coefficients, photostationary states, and quantum yields for Pr ⇄ Pfr.

Conclusions:

  • Understanding these phytochrome parameters is essential for elucidating their natural roles.
  • The data supports the application of phytochromes in optogenetics and biotechnology.