Bleaching of chlorophylls by UV irradiation in vitro: The effects on chlorophyll organization in acetone and n-hexane

Abstract

The stability of chlorophylls toward UV irradiation was studied by Vis spectrophotometry in extracts containing mixtures of photosynthetic pigments in acetone and n-hexane. The chlorophylls underwent destruction (bleaching) obeying first-order kinetics. The bleaching was governed by three major factors: the energy input of the UV photons, the concentration of the chlorophylls and the polarity of the solvent, implying different molecular organizations of the chlorophylls in the two solvents.

Zinc(II) and copper(II) complexes with pheophytin and mesoporphyrin and their stability to UV-B irradiation: Vis spectroscopy studies

“…24,25 The UV-induced changes of chlorophylls were already detected in various solvents, such as acetone and n-hexane, using the Q-band as a sensitive indicator. 10 Similar to this, in the present study, it was found that UV-B irradiation induced a gradual decrease of the absorption over the whole measured spectral range (300-750 nm), e.g., a hypochromic effect was clearly observed for irradiated pheophytin, and the Zn-and Cu-Pheo complexes in 95 % ethanol, as shown in Figs. 2A-2C. In addition, it was also found that UV-B irradiation of mesoporphyrin and its Zn-or Cu-MP complexes induced a clear decrease of the Soret band intensity (A Soret-max ), as shown in Fig.…”

“…Treatment of chlorophyll with strong UV and visible light in solutions and in isolated photosynthetic organelles results in irreversible breakdown of chlorophyll, i.e., bleaching. [10][11][12] This work deals with the stability of two porphyrin derivatives, i.e., pheophytin and mesoporphyrin, and their heavy metal complexes to continuous UV-B irradiation. The irradiation was performed in 95 % ethanol for different irradiation periods, providing possibilities for kinetic analysis.…”

Fundamental molecules of life are pigments which arose and co-evolved as a response to the thermodynamic imperative of dissipating the prevailing solar spectrum

“…Isolated chlorophylls are susceptible to bleaching (the opening up of the tetrapyrrole ring) particularly at 350 nm, where there is significant absorption. However, at high concentration they form aggregates that are particularly rapid quenchers from the UV-C to the UV-A and therefore stable against photoreactions and break-up (Zvezdanović and Marković, 2008). These same authors demonstrated that an accessory pigment environment has rather little effect on chlorophyll bleaching independent of the wavelength of the light, and therefore the assignation of accessory pigments as protectors of the photosynthetic system may be misguided.…”

Nanosilver Could Usher in Next‐Generation Photoprotective Agents for Magnesium Porphyrins

“…The XPS peaks corresponding to Ag 3d (5/3) and Ag 3d (2/3) appeared at binding energies of about 368.3 and 374.3 eV, respectively, in good agreement with bulk silver metallic values. [ 21 ] Transmission electron microscopy (TEM) confi rmed the existence of spherical Ag nanoparticles (as illustrated in [ 22 ] and that Chl a is present in monomeric form. Photodegradation is characterized by the decrease in the intensity of both Soret and Q bands on exposure of Chl a to red light.…”