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Green light effects on biological systems: a new biophysical phenomenon.

ABSTRACT: This paper reports a new phenomenon connected with the influence of green light (GL) on biological systems. Our experiments have revealed an antioxidant effect of GL on cells subjected to lethal doses of UV at the cellular level and a protective effect of GL on DNA denatured by UV, coupled with a structural modification of DNA macromolecules under GL irradiation, at the molecular level. Mouse melanocyte cultures are subjected to UV irradiations with L(50) fluxes of 16.0 J m(-2) s(-1). GL is obtained from a strontium aluminate pigment, which emits GL under UV activation. Cells grown in GL, prior to UV irradiation, present a clear surprising protective effect with surviving values close to the controls. A GL antioxidant effect is suggested to be mediated through GL influence on cellular water cluster dynamics. To test this hypothesis, reactive oxygen species (ROS) are determined in cell cultures. The results revealed a decrease of cellular ROS generation in the UV-irradiated samples protected by a previous 24 h of GL irradiation. At the DNA level, the same type of GL protection against UV damage is recorded by gel electrophoresis and by UV spectroscopy of the irradiated DNA molecules. Two physical methods, impedance spectroscopy and chronoamperometry, have revealed at the level of GL-irradiated DNA molecules spectral modifications that correlate with the UV spectroscopy results. The interaction between the chargeless photons and the field of water molecules from the cellular compartments is discussed in relation with the new field of macroscopic quantum coherence phenomena.

SUBMITTER: Comorosan S

PROVIDER: S-EPMC2710461 | biostudies-other | 2009 Aug

REPOSITORIES: biostudies-other

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Project description:Red and blue light are traditionally believed to have a higher quantum yield of CO2 assimilation (QY, moles of CO2 assimilated per mole of photons) than green light, because green light is absorbed less efficiently. However, because of its lower absorptance, green light can penetrate deeper and excite chlorophyll deeper in leaves. We hypothesized that, at high photosynthetic photon flux density (PPFD), green light may achieve higher QY and net CO2 assimilation rate (A n) than red or blue light, because of its more uniform absorption throughtout leaves. To test the interactive effects of PPFD and light spectrum on photosynthesis, we measured leaf A n of "Green Tower" lettuce (Lactuca sativa) under red, blue, and green light, and combinations of those at PPFDs from 30 to 1,300 μmol⋅m-2⋅s-1. The electron transport rates (J) and the maximum Rubisco carboxylation rate (V c,max) at low (200 μmol⋅m-2⋅s-1) and high PPFD (1,000 μmol⋅m-2⋅s-1) were estimated from photosynthetic CO2 response curves. Both QY m,inc (maximum QY on incident PPFD basis) and J at low PPFD were higher under red light than under blue and green light. Factoring in light absorption, QY m,abs (the maximum QY on absorbed PPFD basis) under green and red light were both higher than under blue light, indicating that the low QY m,inc under green light was due to lower absorptance, while absorbed blue photons were used inherently least efficiently. At high PPFD, the QY inc [gross CO2 assimilation (A g)/incident PPFD] and J under red and green light were similar, and higher than under blue light, confirming our hypothesis. V c,max may not limit photosynthesis at a PPFD of 200 μmol m-2 s-1 and was largely unaffected by light spectrum at 1,000 μmol⋅m-2⋅s-1. A g and J under different spectra were positively correlated, suggesting that the interactive effect between light spectrum and PPFD on photosynthesis was due to effects on J. No interaction between the three colors of light was detected. In summary, at low PPFD, green light had the lowest photosynthetic efficiency because of its low absorptance. Contrary, at high PPFD, QY inc under green light was among the highest, likely resulting from more uniform distribution of green light in leaves.

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Green light effects on biological systems: a new biophysical phenomenon.

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