Quantitative analysis of extracted phycobilin pigments in cyanobacteria-an assessment of spectrophotometric and spectrofluorometric methods.

Monika Sobiechowska-Sasim,Alicja Kosakowska,Joanna Stoń-Egiert

doi:10.1007/s10811-014-0244-3

Monika Sobiechowska-Sasim, Alicja Kosakowska + Show 1 more

Open Access

https://doi.org/10.1007/s10811-014-0244-3

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Abstract

Phycobilins are an important group of pigments that through complementary chromatic adaptation optimize the light-harvesting process in phytoplankton cells, exhibiting great potential as cyanobacteria species biomarkers. In their extracted form, concentrations of these water-soluble molecules are not easily determined using the chromatographic methods well suited to solvent-soluble pigments. Insights regarding the quantitative spectroscopic analysis of extracted phycobilins also remain limited. Here, we present an in-depth study of two methods that utilize the spectral properties of phycobilins in aqueous extracts. The technical work was carried out using high-purity standards of phycocyanin, phycoerythrin, and allophycocyanin. Calibration parameters for the spectrofluorometer and spectrophotometer were established. This analysis indicated the possibility of detecting pigments in concentrations ranging from 0.001 to 10 μg cm−3. Fluorescence data revealed a reproducibility of 95 %. The differences in detection limits between the two methods enable the presence of phycobilins to be investigated and their amounts to be monitored from oligotrophic to eutrophic aquatic environments.

Highlights

Adequate information on phytoplankton community structure and functional diversity is essential to protect vulnerableM
The spectrophotometric and spectrofluorometric signatures of single phycobilin pigments differ in their shape, λmax number, and position
PC was investigated by exciting the molecule at 590 nm, APC emission spectra were obtained from excitation wavelengths set at 600 nm, and PE emission spectra at 576 nm were obtained from excitation at 530 nm

Summary

Introduction

Adequate information on phytoplankton community structure and functional diversity is essential to protect vulnerableM. Adequate information on phytoplankton community structure and functional diversity is essential to protect vulnerable. These water-soluble protein complexes—open-chain tetrapyrroles—are the major players in light harvesting in cyanobacteria, but they are found in red algae, cryptomonads, prochlorophytes, and glaucocytophytes (Larkum 2003). The pigment system of cyanobacteria produces only a weak chlorophyll a fluorescence signal. Fluorescence spectra arise mainly from photosystem II, so the fluorescence yield of phycobilins is very high, carrying a significant amount of spectral information that can be used to assess the abundance of cyanobacteria (Yentsch and Yentsch 1979). The availability of accurate concentrations for phycobilin pigments is essential for correlating reflectance with field population density; this is especially important in remote sensing. The color sensors currently employed for the satellite imagery used to monitor large areas and to detect algal blooms are insufficiently sensitive to detect specific phycobilins (Woźniak et al 2011)

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