title: Applying and comparing two chemometric methods in absorption spectral analysis of photopigments from Arctic microalgae.
abstract: Pigment absorption property of two arctic microalgae species (Skeletonema marinoi and Chlorella sp.) cultured at three temperatures (0, 4 and 8°C) was analyzed. Carotenoids and chlorophyll (Chl) c were positive factors to the high cell activities and primary productivities of S. marinoi at 4°C and 0°C, respectively; whereas Chl a had a positive effect on Chlorella sp. at all three temperatures, and carotenoids had a relatively high effect at 0°C. The absorption locations of photopigments were analyzed in detail using both fourth derivative and Symlet-6 wavelet analysis. Both methods precisely detected pigments with a relative large content; the fourth derivative analysis specifically detected the existence of a Chl a peak at about 410 nm and showed better differentiation of diatoxanthin, whereas the wavelet analysis distinctively indicated the existence of chlorophyllide a, β-carotene, and Chl c. The separation limit to pigment peaks of the fourth derivative spectra (4 nm) was 1 nm higher than that of the wavelet high-frequency spectra (3 nm). The wavelet high-frequency spectra were more stable in detecting pigment locations and were more effective in discriminating microalgae. Small algebraic difference of 10(-16) between the reconstructed absorption spectra obtained by the inverse wavelet transform and their corresponding original spectra also showed the validity of Symlet-6 wavelet in the detection of pigments. Another specific discovery of this research is the existence of a Chl a allomer in Chlorella sp., which was detected by both methods.
authors.affiliation: SOA Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai 200136, PR China.
authors.forename: Fang
authors.initials: F
authors.lastname: Zhang
authors.forename: Jianfeng
authors.initials: J
authors.lastname: He
authors.forename: Lihua
authors.initials: L
authors.lastname: Xia
authors.forename: Minghong
authors.initials: M
authors.lastname: Cai
authors.forename: Ling
authors.initials: L
authors.lastname: Lin
authors.forename: Yingzhi
authors.initials: Y
authors.lastname: Guang
mesh_terms: D001110:Arctic Regions; D002338:Carotenoids / Q000032:analysis* / Q000145:classification; D002708:Chlorella / Q000737:chemistry* / Q000254:growth & development / Q000302:isolation & purification; D002734:Chlorophyll / Q000032:analysis* / Q000145:classification; D017377:Diatoms / Q000737:chemistry* / Q000254:growth & development / Q000302:isolation & purification; D013057:Spectrum Analysis / Q000379:methods*; D013696:Temperature
chemical_list: D002734:Chlorophyll; D002338:Carotenoids