Solvent-free chlorophyll spectrometry in unicellular algal research
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PHYCOLOGICAL METHODS
Solvent-free chlorophyll spectrometry in unicellular algal research Raymond J. Ritchie 1 & Suhailar Sma-Air 1 Received: 13 July 2020 / Revised and accepted: 13 August 2020 # Springer Nature B.V. 2020
Abstract Scanning spectrophotometers equipped with integrating spheres are now readily available commercially. This study explores the possibility of largely escaping from solvent-based determinations of chlorophylls and bacteriochlorophylls using the in vivo absorption spectra to deduce the chlorophyll/bacteriochlorophyll (Chl/BChl) contents of unicellular photosynthetic organisms. Furthermore, we show that scans from ordinary dual beam spectrometers can also be used to estimate the Chl/BChls of unicells in vivo despite light scattering. Spectra of unicellular algae using integrating sphere spectroscopy can measure the absorbance (A) of turbid cell suspensions and hence the in vivo pigment absorption properties of photosynthetic organisms. These results were compared with those obtained using conventional dual beam spectrophotometry scans on turbid cell suspensions and the in solvent spectra of the photosynthetic pigments. The common unicellular green alga, Chlorella sp., is used as an example of an oxygenic photo-organism with Chl a + b, and comparisons were made to other unicellular algae: a cyanobacterium (Synechococcus), a diatom (Chaetoceros) and Acaryochloris. The anoxygenic photosynthetic bacterium Rhodopseudomonas palustris (BChl a) was included in the study. Empirical algorithms are presented for the solvent-free estimation of Chls a, a + b, a + c1c2, d + a and BChl a for the organisms in the study. Keywords Integrating sphere spectroscopy . Absorbance (A) . Transmission (%T) . Oxygenic photo-organisms . Anoxygenic photo-organisms . In vivo and in solvent determinations of chlorophylls
Introduction Integrating sphere scanning spectrophotometers are now readily available commercially. They are particularly useful for objectively assessing the spectral absorption and reflectance of algal cell suspensions and so provide a measurement of what light photosynthetic organisms are actually absorbing in vivo (Scheer 1991, Scheer 2006). Ordinary dual beam spectrometers generally do not give valid quantitative measurements of the spectral properties of living cells due to background light scattering. Spectra of unicellular oxygenic algae and photosynthetic bacteria using integrating sphere spectroscopy can measure the absorbance (A) of turbid cell suspensions and hence the in vivo pigment absorption properties of photosynthetic organisms.
* Raymond J. Ritchie [email protected]; [email protected] 1
ANED (Andaman Environment and Natural Disaster Research Centre), Technology and Environment, Prince of Songkla University-Phuket, Phuket 83120, Thailand
In this study, the quantitative spectral properties of some representative oxygenic and an anoxygenic photosynthetic organisms are compared with those obtained using an integrating sphere spectrophotometer, conventional dual beam
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