The active conformation of allophycocyanin from Spirulina platensis studied with spectroscopic analysis.
Allophycocyanin (APC) was purified from Spirulina platensis using hydroxylapatite chromatography and ion-exchange chromatography. Effects of solution pH on spectra of APC were studied. APC has an absorption maximum at 650 nm, and a shoulder at 620 nm. The fluorescence emission peak is at 660 nm. The efficiency of energy absorbing and transfer in APC could be reflected by the absorption spectra and fluorescence spectra, respectively. Structural variations of APC could be monitored by means of circular dichroism spectra. APC showed good absorbance and fluorescence stability at varying pH with only minor changes between pH 4-10. The trimeric structure of APC was maintained while local variations of protein peptides were allowed in response to the environmental disturbance. Beyond this pH range, secondary structure as well as overall conformation of APC dramatically changed, and the energy absorption and transfer ability were also disrupted.
Shao
Si-Mi
SM
State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Ji'nan 250100, China. shaosimi@mail.sdu.edu.cn
Su
Hai-Nan
HN
Zhang
Xi-Ying
XY
Peng
Guo-Hong
GH
Zhou
Bai-Cheng
BC
Zhang
Yu-Zhong
YZ