Extinction coefficient for red-shifted chlorophylls: Chlorophyll d and chlorophyll f

Both chlorophyll f and chlorophyll d are red-shifted chlorophylls in oxygenic photosynthetic organisms, which extend photon absorbance into the near infrared region. This expands the range of light that can be used to drive photosynthesis. Quantitative determination of chlorophylls is a crucial step in the investigation of chlorophyll-photosynthetic reactions in the field of photobiology and photochemistry. No methods have yet been worked out for the quantitative determination of chlorophyll f. There is also no method available for the precise quantitative determination of chlorophyll d although it was discovered in 1943. In order to obtain the extinction coefficients (ε) of chlorophyll f and chlorophyll d, the concentrations of chlorophylls were determined by Inductive Coupled Plasma Mass Spectrometry according to the fact that each chlorophyll molecule contains one magnesium (Mg) atom. Molar extinction coefficient εchl f is 71.11 × 103 L mol− 1 A707 nm cm− 1 and εchl d is 63.68 × 103 L mol− 1 A697 nm cm− 1 in 100% methanol. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.

► There is a real need for accurate extinction coefficients for Chl d and Chl f. ► ICP‐MS was used to determine the molar concentrations of Mg extracted from purified chlorophylls. ► The extinction coefficients at different wavelengths in various solvents were calculated. ► The spectral properties of red‐shifted chlorophylls were reported.