Preprocess dependence of optical properties of ensembles and single siphonaxanthin-containing major antenna from the marine green alga Codium fragile

Abstract

The siphonaxanthin-siphonein-Chl-a/b-protein (SCP) is the light-harvesting complex of the marine alga Codium fragile. Its structure resembles that of the major light-harvesting complexes of higher plants, LHC II, yet it features a reversed Chl a:Chl b ratio and it accommodates other variants of carotenoids. We have recorded the fluorescence emission spectra and fluorescence lifetimes from ensembles and single SCP complexes for three different scenarios of handling the samples. While the data obtained from ensembles of SCP complexes yield equivalent results, those obtained from single SCP complexes featured significant differences as a function of the sample history. We ascribe this discrepancy to the different excitation intensities that have been used for ensemble and single complex spectroscopy, and conclude that the SCP complexes undergo an aging process during storage. This process is manifested as a lowering of energetic barriers within the protein, enabling thermal activation of conformational changes at room temperature. This in turn leads to the preferential population of a red-shifted state that features a significant decrease of the fluorescence lifetime.

Wavelength-Dependent Optical Response of Single Photosynthetic Antenna Complexes from Siphonous Green Alga Codium fragile

“…The corresponding fluorescence transient was determined only for the immobilized sample and was compatible with a biexponential decay with lifetime components (amplitudes) of 4.0 ns (85%) and 1.2 ns (15%), which is in line with the distribution found for the single complexes. These results are documented in ref . Given that an intensity of 525 W/cm 2 at 561 nm produces about the same number of excited states per unit time as an intensity of 270 W/cm 2 at 639 nm and the agreement between the ensemble spectra taken at high-light and low-light illumination conditions, as well as the lack of any spectral features that are related to free chlorophyll molecules, namely, emission around 675 nm, and a fluorescence lifetime component of about 5–8 ns, − we exclude the possibility that the emission from the red-shifted quenched state stems from photodamaged complexes.…”

“…Protein Preparation. Codium fragile (KU-065, KU-MACC, Kobe, Japan) was cultivated in floating form as described in refs and . Additionally, SCP was purified from lyophilized algae according to refs and .…”

“…Codium fragile (KU-065, KU-MACC, Kobe, Japan) was cultivated in floating form as described in refs and . Additionally, SCP was purified from lyophilized algae according to refs and . Briefly, thylakoid proteins solubilized with n -dodecyl-β- d -maltoside (β-DDM) were separated by sucrose density gradient; the collected crude SCP band was purified twice by anion exchange column chromatography, purified again by sucrose density gradient, and finally gel filtered.…”

“…In a recent publication, we addressed a possible dependence of the emission spectrum on both the excitation intensity and the sample preparation conditions . Due to signal-to-noise restrictions, this could be investigated only for bulk samples.…”

Biopigments (Phycoerythrin, Fucoxanthin and Siphonaxanthin) from Seaweeds and Their Potential Applications as Ingredients in Cosmeceutical Industries: A Review

“…[32,33], Sargassum angustifolium [34], Turbinaria turbinata [35], etc. Additionally, siphonaxanthin, a particular keto-carotenoid, is accumulated in certain green seaweed [36,37], such as Codium cylindricum [38,39], Codium fragile [36,37,40,41], Halimeda sp., [42], etc. The sources of three biopigments from various types of seaweed are presented in Table 1.…”