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Brody, Seymour Steven

doi:10.1023/a:1020405921105

Cited by 51 publications

(24 citation statements)

References 13 publications

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“…where τ is the measured lifetime and τ 0 is the natural lifetime of Chl a (Brody and Rabinowitch 1957;Brody 2002). The natural lifetime is the time that would be required for a molecule to return to the ground state from an excited state if fluorescence were the sole dissipation pathway.…”

Section: Photophysiologymentioning

confidence: 99%

“…The natural lifetime is the time that would be required for a molecule to return to the ground state from an excited state if fluorescence were the sole dissipation pathway. For Chl a, τ 0 is 15 ns and is constant, independent of solvent, organism or environmental condition (Brody and Rabinowitch 1957;Brody 2002;Lakowicz 2006). We then calculated the quantum yield for thermal dissipation (Φ T ) as…”

Section: Photophysiologymentioning

confidence: 99%

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Photosynthetic energy conversion efficiency in the West Antarctic Peninsula

Sherman

Gorbunov

Schofield

et al. 2020

Limnology & Oceanography

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The West Antarctic Peninsula (WAP) is a highly productive polar ecosystem where phytoplankton dynamics are regulated by intense bottom-up control from light and iron availability. Rapid climate change along the WAP is driving shifts in the mixed layer depth and iron availability. Elucidating the relative role of each of these controls and their interactions is crucial for understanding of how primary productivity will change in coming decades. Using a combination of ultra-high-resolution variable chlorophyll fluorescence together with fluorescence lifetime analyses on the 2017 Palmer Long Term Ecological Research cruise, we mapped the temporal and spatial variability in phytoplankton photophysiology across the WAP. Highest photosynthetic energy conversion efficiencies and lowest fluorescence quantum yields were observed in iron replete coastal regions. Photosynthetic energy conversion efficiencies decreased by~60% with a proportional increase in quantum yields of thermal dissipation and fluorescence on the outer continental shelf and slope. The combined analysis of variable fluorescence and lifetimes revealed that, in addition to the decrease in the fraction of inactive reaction centers, up to 20% of light harvesting chlorophyll-protein antenna complexes were energetically uncoupled from photosystem II reaction centers in iron-limited phytoplankton. These biophysical signatures strongly suggest severe iron limitation of photosynthesis in the surface waters along the continental slope of the WAP.

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Section: Photophysiologymentioning

confidence: 99%

Section: Photophysiologymentioning

confidence: 99%

Photosynthetic energy conversion efficiency in the West Antarctic Peninsula

Sherman

Gorbunov

Schofield

et al. 2020

Limnology & Oceanography

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“…It was demonstrated that the presence of re-emission slows down fluorescence kinetics (Mammel et al 1992; Connolly et al 1982; Lakowicz 1994). The impact of re-emission on measured fluorescence lifetimes can be quite substantial in a solution of highly concentrated Chls (Connolly et al 1982), which was reported to have fluorescence yield of around 0.33 (Brody 2002). However this effect can be avoided or minimised if very thin layers of photosynthetic tissue are used (Lakowicz 1994) or if the measurements are performed in front-face detection (Connolly et al 1982).…”

Section: How To Achieve Well-defined Photosynthetic States?mentioning

confidence: 99%

Time-resolved fluorescence measurements on leaves: principles and recent developments

2018

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Photosynthesis starts when a pigment in the photosynthetic antennae absorbs a photon. The electronic excitation energy is then transferred through the network of light-harvesting pigments to special chlorophyll (Chl) molecules in the reaction centres, where electron transfer is initiated. Energy transfer and primary electron transfer processes take place on timescales ranging from femtoseconds to nanoseconds, and can be monitored in real time via time-resolved fluorescence spectroscopy. This method is widely used for measurements on unicellular photosynthetic organisms, isolated photosynthetic membranes, and individual complexes. Measurements on intact leaves remain a challenge due to their high structural heterogeneity, high scattering, and high optical density, which can lead to optical artefacts. However, detailed information on the dynamics of these early steps, and the underlying structure–function relationships, is highly informative and urgently required in order to get deeper insights into the physiological regulation mechanisms of primary photosynthesis. Here, we describe a current methodology of time-resolved fluorescence measurements on intact leaves in the picosecond to nanosecond time range. Principles of fluorescence measurements on intact leaves, possible sources of alterations of fluorescence kinetics and the ways to overcome them are addressed. We also describe how our understanding of the organisation and function of photosynthetic proteins and energy flow dynamics in intact leaves can be enriched through the application of time-resolved fluorescence spectroscopy on leaves. For that, an example of a measurement on Zea mays leaves is presented. Electronic supplementary material The online version of this article (10.1007/s11120-018-0607-8) contains supplementary material, which is available to authorized users.

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“…In the particular case of Chl a (see i, ii, above), it has strong absorption both in the blue and in the red, plus several weaker absorption bands in-between ( Fig. 1); (iii) the natural singlet excitation lifetime of Chl a, that is calculated from its absorption spectrum, is approximately 15 ns, but its mean measured excitation lifetime in vivo ranges between 0.3 and 0.4 ns (Brody and (2006); (ii) Bazzaz (1981); (iii) Shedbalkar and Rebeiz (1992); (iv) Govindjee and Satoh (1983); (v) Zapata et al (2003); (vi) Kobayashi et al (2007) Photosynth Res (2009) 99:85-98 89 Rabinowitch 1957; Schmuck and Moya 1994;Schilstra et al 1999;Morales et al 2001;Brody 2002). We also note that this excitation lifetime exceeds, by one order of magnitude, the time required for charge separation in the PS II-RC (5-7 ps; Greenfield et al 1997;Miloslavina et al 2006;Broess et al 2008) and in PS I-RC (1-2 ps; Savikhin et al 2001;Holzwarth et al 2005); and (iv) its lowest excited singlet state (cf.…”

Section: Chlorophylls In Solutionmentioning

confidence: 99%

A viewpoint: Why chlorophyll a?

et al. 2009

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Chlorophyll a (Chl a) serves a dual role in oxygenic photosynthesis: in light harvesting as well as in converting energy of absorbed photons to chemical energy. No other Chl is as omnipresent in oxygenic photosynthesis as is Chl a, and this is particularly true if we include Chl a(2), (=[8-vinyl]-Chl a), which occurs in Prochlorococcus, as a type of Chl a. One exception to this near universal pattern is Chl d, which is found in some cyanobacteria that live in filtered light that is enriched in wavelengths >700 nm. They trap the long wavelength electronic excitation, and convert it into chemical energy. In this Viewpoint, we have traced the possible reasons for the near ubiquity of Chl a for its use in the primary photochemistry of Photosystem II (PS II) that leads to water oxidation and of Photosystem I (PS I) that leads to ferredoxin reduction. Chl a appears to be unique and irreplaceable, particularly if global scale oxygenic photosynthesis is considered. Its uniqueness is determined by its physicochemical properties, but there is more. Other contributing factors include specially tailored protein environments, and functional compatibility with neighboring electron transporting cofactors. Thus, the same molecule, Chl a in vivo, is capable of generating a radical cation at +1 V or higher (in PS II), a radical anion at -1 V or lower (in PS I), or of being completely redox silent (in antenna holochromes).

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Untitled

Cited by 51 publications

References 13 publications

Photosynthetic energy conversion efficiency in the West Antarctic Peninsula

Photosynthetic energy conversion efficiency in the West Antarctic Peninsula

Time-resolved fluorescence measurements on leaves: principles and recent developments

A viewpoint: Why chlorophyll a?

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