Computer Simulation on Kinetics of Primary Process in Photosynthesis (Ⅲ)——Energy Transfer in the Trimers and Hexamers of C-Phycocyanins

Based on the crystal structure data from X-ray analysis,the energy transfer processes inthe trimers and hexamers of C-phycocyanins(C-PC)have been simulated.The simulation results show(i)The excitation energy could transfer back and forth many times through a certain path before it was finallylost through fluorescence emission.(ii)The higher the aggregate,the less the transfer times.(iii)In atrimer,an m-(mediate)chromophore in a monomer and an f-(fluorescing)chromophore in another are inclosest proximity to each other and an appropriate orientation.These two chromophores form a fast transferpair with their energy transfer proceeding so fast that the time constant is less than 1 ps.There are 3 suchfast transfer pairs which are symmetrically equivalent in a trimer,while the paths of m■f and f■f betweenthe monomers are responsible for linking the fast transfer pairs.(iv)The excitation energy on an s-(sensi-tizing)chromophore is dominantly transferred to the f-chromophore in the same monomer.(v)In the hex-amer,there are 2 types of principal paths for linking the 2 trimers,which are m■m and s■s paths,whilethe excitation energy on the f-chromophores will be transferred into another trimer through the m-chro-mophore in the same fast transfer pair.The simulation shows that the hexamer possesses an optimal struc-ture for energy transfer.

Computer Simulation on Kinetics of Primary Process in Photosynthesis(Ⅱ)——Energy Transfer in the β Subunits and Monomers in C-Phycocyanins

Based on the crystal structure data of C-phycocyanins from Mastigocladus Laminosus andAgmenellum Quadruplicatum,the energy transfer processes in the βsubunits and the monomers are simulat-ed by the use of computer simulation technique.The simulation results show that excitation energy cantransfer in both directions between any pair of chromophores,and furthermore,the transfer can take place intwo opposite directions for many times between a pair of chromophores.There certainly exists energy trans-fer between the two subunits in a monomer.The dynamic nature of the energy transfer processes has beenshown.Besides,it is also indicated that a component obtained from mathematically fitting the experimentaldata cannot be equivalent to a physical process.

Isolation of Picocyanobacteria (Order Synechococcales) and Occurrence of the Cyanotoxin Anatoxin-A in a Shallow Mesotrophic Pond

We have verified the use of a serial filtration method to isolate picocyanobacteria for analysis. We used eDNA metabarcoding to confirm the picocyanobacteria as members of the Order Synechococcales, Genus Cyanobium, specifically Cyanobium 6307. Fluorometric analysis using accessory pigments phycocyanin and phycoerythrin described periods of excess biomass, where the net growth rate model confirmed these conditions. The total anatoxin-a concentrations in the picocyanobacterial sample ranged from 0.0074 - 6.41 μg·L-1 representing a 40-fold difference over the entire sampling season. Sampling frequency of every three days appeared to be an important factor in capturing these changes in anatoxin-a concentration. During a period of excess biomass, we were able to establish a linear correlation between cyanobacterial biomass and Anatoxin-a concentrations.

Isolation of Picocyanobacteria (Order Synechococcales) and Occurrence of Cyanotoxins (Anatoxin-a) in Saline Microhabitats at Martha’s Vineyard, MA

We have used serial filtration to isolate picocyanobacteria from brackish and marine microhabitats for analysis. We used 16s metabarcoding to confirm the picocyanobacteria as members of the Order Synechococcales, Genus Cyanobium 6307 (Upper Chilmark Pond) and differing abundances of Cyanobium 6307 and Synechococcus 9902 (Chilmark Pond, Edgartown Great Pond, Tisbury Great Pond and Tashmoo Pond). The proportion and composition of (pico)cyanobacteria in water samples were influenced by the salinity concentrations at various sites, as evidenced by fluorometry and 16s metabarcoding analysis. The cyanobacterial neurotoxin anatoxin-a was present in the picocyanobacterial samples from all studied sites. Additional analyses using fluorometry and 16s metabarcoding described members of the Order Nostocales, including a halotolerant population of Dolichospermum sp., Sphaerospermopsis spp. and Nodularia spp. in Upper Chilmark Pond. We were able to establish a positive linear correlation between cyanobacterial biomass (phycocyanin) and anatoxin-a concentrations using samples taken from Upper Chilmark Pond.

Telomere Protective Effects of a Cyanobacteria Phycocyanin against Blue Light and UV Irradiations: A Skin Anti-Aging and Photo-Protective Agent

Background: Cyanobacteria phycocyanins (Cps) have already shown powerful antioxidant properties. In human cells submitted to oxidative stress the telomeres length decrease, the expression of progerin and the activity of mTOR are increased. At our knowledge, there is no published data on Cps correlated with ultraviolet radiation (UV) and blue light effects in human cells regarding telomeres’ length, progerin expression or mTOR1 complex activity. Objectives: In this study, we sought to assess 1) telomeres’ length in newborn human fibroblasts exposed to UV and blue light;2) progerin production in mature human normal fibroblasts exposed to UV;3) mTOR1 activation in adult human normal keratinocytes exposed to UV, analyzing the activity of a Cyanobacteria phycocyanin (Cp) in these in vitro models. Materials and Methods: Human skin fibroblasts or human normal keratinocytes were cultured—in the absence or in the presence of Cp and submitted to UVB + UVA and blue light irradiations. Telomeres’ length, progerin expression and mTOR1 activity were then assessed by molecular biology and immuno-enzymatic methods. Results: In cultured fibroblasts exposed to irradiations and treated by Cp, telomeres’ shortage and progerin expression were lower compared to irradiated untreated cells. In cultured keratinocytes treated by Cp and exposed to irradiations, the mTOR activity was lower compared to irradiated untreated cells. Conclusions: In these in vitro studies on human skin fibroblasts and on normal human keratinocytes, the cyanobacteria phycocyanin (Cp) showed a decrease of damages induced by UV and blue light expressed by telomeres preservation and downregulation of progerin expression and of mTOR activity, thus showing skin anti-aging and photo-protective potential.

A novel phycocyanin-Chla/c_2-protein complex isolated from chloroplasts of Chroomonas placoidea

Nine pigment-protein complexes were separated and characterized from intact Chroomonasplacoidea chloroplasts by IEF. The bands Ⅰ-Ⅵ with their isoelectric points （pI） values from 4 to 6 were phycocyanin components; bands Ⅷ and Ⅸ （pI = 2.8-3.6） were chlorophyll-protein complexes. According to absorption and fluorescence spectra, band VII was designated as a novel phycocyanin-Chla/c2-protein complex （pI ≈ 3.4-3.7）. These results indicated that phycocyanin is structurally and functionally coupled with chlorophyll-protein complex in C. placoidea, and probably interacted with electrostatic force in combination.

Purification and Photodynamic Bioactivity of Phycoerythrin and Phycocyanin from Porphyra yezoensis Ueda

Phycoerythrin and phycocyanin were purified from Porphyra yezoensis Ueda with their bioactivity determined in this study. Continuous precipitation with ammonium sulfate at different concentrations(10%, 20%, 40% and 50%) increased the purity(A564:A280) of phycoerythrin to 1.49, 3.92 fold of the raw extract(0.38) and the purity(A615:A280) of phycocyanin to 0.70, 3.33 fold of the raw extract(0.21). Two more times of chromatography with hydroxylapatites finally made the purity of phycoerythrin and phycocyanin reach 5.50, 14.47 fold of the raw extract, and 5.10, 24.29 fold of the raw extract, respectviely. The yield of high purity phycoerythrin and phycocyanin were 0.21% and 0.09% of dried P. yezoensis blade, respectively. The photodynamic cytotoxic experiment showed that both phycoerythrin and phycocyanin inhibited the growth of liver tumor cells significantly. It was found that 250 mg L-1 purified phycoerythrin and phycocyanin inhibited the growth of hepatocellular carcinoma cells 24 h after laser-irradiation by 80% and 59%, respectively, and 100 mg L-1 purified phycoerythrin and phycocyanin induced the apoptosis of 31.54% and 32.54% of the cells, respectively, 8 h after photodynamic therapy. Oue findings demonstrated that P. yezoensis can serve as photosensitizer(phycoerythrin and phycocyanin) producer.

Phycocyanin attenuates X-ray-induced pulmonary inflammation via the TLR2-MyD88-NF-κB signaling pathway

Phycocyanin (PC), a natural algal protein, is reported for having anti-oxidant and antiinfl ammatory properties. We investigated its ability to attenuate lung infl ammation in mice subjected to X-ray radiation. Male C57BL/6 mice were assigned to the control, total body irradiation, PC pretreatment, and PC treatment groups. Mice in the PC pretreatment group were gavaged with 200 mg/kg PC for 7 consecutive days before irradiation, and those in the PC treatment group were gavaged with 200 mg/kg PC for 7 consecutive days after irradiation. Lungs were collected on Day 7 after irradiation exposure. Hematoxylin and eosin staining of mouse lung sections showed considerable infl ammation damage 7 days after irradiation compared with the control lung but a reduction in pathological injury in the PC treatment group. Pretreatment or treatment with PC signifi cantly decreased levels of interleukin-6 and tumor necrosis factor-α in the lung, and also increased the relative mRNA expression of superoxide dismutase and glutathione. In vivo, PC signifi cantly reduced the expression of Toll-like receptor TLR2, myeloid diff erentiation primary response Myd88, and nuclear factor NF-κB, at both the transcriptional and translation level. Taken together, these data indicated that PC attenuated lung infl ammatory damage induced by radiation by blocking the TLR2- MyD88-NF-κB signaling pathway. Therefore, PC could be a protective agent against radiation-induced infl ammatory damage in normal tissues.

Alternative Methods for Analysis of Cyanobacterial Populations in Drinking Water Supplies: Fluorometric and Toxicological Applications Using Phycocyanin

The management of cyanobacteria and potential exposure to associated biotoxins requires the allocation of scarce resources across a range of freshwater resources within various jurisdictions. Cost effective and reliable methods for sample processing and analysis form the foundation of the protocol yielding reliable data from which to derive important decisions. In this study the utilization of new methods to collect, process and analyze samples enhanced our ability to evaluate cyanobacterial populations. Extraction of phycocyanin using the single freeze thaw method provided more accurate and precise measurements (CV 4.7% and 6.4%), offering a simple and cost-effective means to overcome the influence of morphological variability. In-vacuo concentration of samples prior to ELISA analysis provided a detection limit of 0.001 μg·L?1 MC. Fractionation of samples (?1) = ?0.279 + (1.368 ? Log PC (μg·L?1) while in an Aphanizomemon spp. dominant system Log MC (ng·L?1) = 0.385 + (0.449 ? Log PC (μg·L?1). These methods and sampling protocol could be used in other aquatic systems across a broader regional landscape to estimate the levels of microcystins.

Temperature Influences on the Expression of GFP Promoted by the Upstream Sequence of cpcB from Arthrospira platensis

In order to investigate the regulation mechanism of the phycocyanin gene,a series of functional analyses of the upstream sequence of cpcB gene from Arthrospira platensis were conducted in E. coli with green fluorescent protein encoding gene(gfp) as the reporter. Results showed that the gfp gene could express at a high level under the promotion of the upstream sequence,suggesting the existence of some strong promoter elements in it. The expression of GFP was influenced by temperature. Higher temperature led to higher expression level. The bioinformatics analyses followed by mutation analyses on the secondary structure of translation ini-tiation region(TIR) revealed that RNA thermosensor might account for the temperature regulation.

Interventional effect of phycocyanin on mitochondrial membrane potential and activity of PC12 cells after hypoxia/reoxygenation

BACKGROUND： Phycocyanin can relieve decrease of mitochondrial membrane potential through reducing production of active oxygen so as to protect neurons after hypoxia/reoxygenation. OBJECTIVE： To observe the effect of phycocyanin on activity of PC12 cells and mitochondrial membrane potential after hypoxia/reoxygenation. DESIGN： Randomized controlled study SETTING ： Cerebrovascular Disease Institute of Affiliated Hospital, Medical College of Qingdao University MATERIALS： The experiment was carried out at the Key Laboratory of Prevention and Cure for cerebropathia in Shandong Province from October to December 2005. PC12 cells, rat chromaffin tumor cells, were provided by Storage Center of Wuhan University; phycocyanin was provided by Ocean Institute of Academia Sinica; Thiazoyl blue tetrazolium bromide （MTT） and rhodamine 123 were purchased from Sigma Company, USA; RPMI-1640 medium, fetal bovine serum and equine serum were purchased from Gibco Company, USA. METHODS： ① Culture of PC12 cells： PC12 cells were put into RPMI-1640 medium which contained 100 g/L heat inactivation equine serum and 0.05 volume fraction of fetal bovine serum and incubated in CO2 incubator at 37℃. Number of cells was regulated to 4 × 10^5 L 1, and cells were inoculated at 96-well culture plate. The final volume was 100μL. ② Model establishing and grouping： Cultured PC12 cells were randomly divided into three groups： phycocyanin group, model control group and non-hypoxia group. At 24 hours before hypoxia, culture solution in phycocyanin group was added with phycocyanin so as to make sure the final concentration of 3 g/L , but cells in model control group did not add with phycocyanin. Cells in non-hypoxia group were also randomly divided into adding phycocyanin group （the final concentration of 3 g/L） and non-adding phycocyanin group. Cells in model control group and phycocyanin group were cultured with hypoxia for 1 hour and reoxygenation for 1, 2 and 3 hours; meanwhile, cells in non-hypoxia group were cultured with oxygen and were measured at 1 hour after hypoxia/reoxygenation. ③ Detecting items： At 1, 2 and 3 hours after reoxygenation, absorbance （A value） of PC12 cells was measured with MTT technique so as to observe activity and quantity of cells. Fluorescence intensity of PC12 cells marked by rhodamine 123 was measured with confocal microscope in order to observe changes of mitochondrial membrane potential. MAEN OUTCOME MEASURES： Comparisons between quantity and activity of PC12 cells and mitochondria membrane potential at 1, 2 and 3 hours after reoxygenation. RESULTS： ① Effect of phycocyanin on quantity and activity of PC12 cells： A value was 0.924±0.027 in adding phycocyanin group and 0.924±0.033 in non-adding phycocyanin group. A value was lower in model control group and phycocyanin group than that in non-hypoxia group at 1, 2 and 3 hours after reoxygenation （0.817±0.053, 0.838±0.037, 0.875±0.029; 0.842±0.029, 0.872±0.025, 0.906±0.023, P 〈 0.05）. A value was higher in phycocyanin group than that in model control group at 1, 2 and 3 after culture （P 〈 0.05）. With culture time being longer, A value was increased gradually in phycocyanin group and model control group after reoxygenation （P 〈 0.05）. ~ Effect of phycocyanin on mitochondrial membrane potential of PC12 cells： Fluorescence intensity was 2.967±0.253 in adding phycocyanin group and 2.962±0.294 in non-adding phycocyanin group. Fluorescence intensity was lower in model control group and phycocyanin group than that in non-hypoxia group at 1, 2 and 3 hours after hypoxia/reoxygenation （1.899±0.397, 2.119±0.414, 2.287±0.402; 2.191±0.377, 2.264±0.359, 2.436±0.471, P 〈 0.05）; but it was higher in phycocyanin group than that in model control group at 1, 2 and 3 after reoxygenation （P 〈 0.05）. With culture time being longer, fluorescence intensity was increased gradually in phycocyanin group and model control group after reoxygenation （P 〈 0.05）. CONCLUSION： Phycocyanin and reoxygenation can protect PC12 cells after hypoxia injury through increasing mitochondrial membrane potential and cellular activity, and the effect is improved gradually with prolonging time of reoxygenation.

The effects of electrochemical oxidation on in-vivo fluorescence and toxin content in Microcystis aeruginosa culture

The increasing occurrence of cyanobacterial blooms in water bodies is a serious threat to the environment. Efficient in-lake treatment methods for the control of cyanobacteria proliferation are needed, their in-vivo detection to obtain a real-time response to their presence, as well as the information about their physiological state after the applied treatment. In-vivo fluorescence measurements of photosynthetic pigments have proved to be effective for quantitative and qualitative detection of phytoplankton in a water environment. In the experiment, chlorophyll and phycocyanin fluorescence sensors were used concurrently to detect stress caused by electrochemical oxidation applying an electrolytic cell equipped with borondoped diamond electrodes on a laboratory culture of cyanobacteria Microcystis aeruginosa PCC 7806. The inflicted injuries were reflected in a clear transient increase in the phycocyanin fluorescence signal(for 104 %? 43%) 24 h after the treatment, which was not the case for the chlorophyll fluorescence signal. In the next 72 h of observation, the fluorescence signals decreased(on 40% of the starting signal) indicating a reduction of cell number, which was confirmed by cell count(24% reduction of the starting concentration) and analysis of extracted chlorophyll and phycocyanin pigment. These results demonstrate the viability of the combined application of two sensors as a useful tool for in-vivo detection of induced stress, providing real-time information needed for the evaluation of the efficiency of the in-lake treatment and decision upon the necessity of its repetition. The electrochemical treatment also resulted in a lower free microcystins concentration compared to control.

Effect of CeCl_3 on the Photosynthetic Characteristics of Spirulina Platensis

In this paper we report that CeCl3 could accelerate the synthesis of chlorophyll a and protein in spirulina platensis. and enhance the activity of oxygen evolution. We also found that the accelerations of CeCl3 in spirulina platensis culture solution of low NaHCO3 were more than in culture solution of high NaHCO3, therefore it was related to the concentration of NaHCO3 The absorption spectrum and low temperature (77 K) fluorescence emission spectrum of spirulina platensis with CeCl3 treated were significantly different from their controls,i.e.its absorption peak of phycocyanin at 620 nm was higher than that of the control.its absorption peak at the long wave region migrated from 676 to 680 nm, and its fluorecence emission ratios (730 nm/685～695 nm) of photosystem I(PSI) to photosystem Ⅱ(PS Ⅱ) were also higher than those of the control; the pitch of the spiral algal body became shorter, and induced structural changes too.

Evaluation of Size Structure in Freshwater Cyanobacterial Populations: Methods to Quantify Risk Associated with Changes in Biomass and Microcystin Concentrations

Cyanobacterial populations in surface waters, including drinking water supplies and recreational waters, represent an ever present challenge for resource managers. As communities continuously respond to external and internal processes, dynamic profiles of composition, dominance, growth and toxigenicity emerge. In this study measures of size structure and biomass, quantified using light microscopy and fluorometry, were used to estimate microcystin concentrations through linear regression analysis. Toxigenic profiles using cyanobacterial biomass were developed for lakes dominated by Microcystis spp. and Dolichospermum spp., influenced by both genus-specific pigment concentrations as well as microcystin concentrations. Community composition (Log %MIC) and biomass were used to describe microcystin concentrations in mixed assemblages, where composition was the first input variable. The accessory photopigment phycocyanin was used to describe the linear relationship between the daily growth and net microcystin production rates in the bloom-forming Microcystis spp. samples, suggesting that this size-fractionated sample may provide indications of potential toxigenicity in the whole lake water sample. Future investigations using fluorometric evaluation of cyanobacterial populations could provide additional applications and metrics for use by resource managers to quantify risk association with elevated cyanotoxin concentrations.

EFFECTS OF PHYCOCYANIN ON EXPRESSION OF CytC mRNA AND CASPASE-3 mRNA AFTER FOCAL CEREBRAL ISCHEMIA/REPERFUSION IN RATS

Objective To study the effects of phycocyanin on the expression of Cytochrome C (CytC)genes and Caspase-3 genes after focal cerebral ischemia/reperfusion in rats. Methods A rat middle cerebral ar-tery occlusion (MCAO)/reperfusion model was produced using the intraluminal filament method. The rats were di-vided into three groups: sham operation group, model control group and phycocyanin group. After MCAO, the neu-robehavioral testing of all rats was made. The infarction area was evaluated with the method of 2,3,7-triphenyltet-razolium chloride (TTC) staining. The expression of CytC mRNA and Caspase-3 mRNA were determined by in situhybridization. Results In the sham operation group and the model control group, there was only a few CytC-positive cells were seen in the normal cerebral tissue. In the model control group, the upregulation of CytC mRNAbegan 6h after ischemia, reached a maximum at 12h (cortex) -24h (striatum) , then subsided gradually, but stillin high level. In the phycocyanin group, CytC-positive cells were also mainly in cortex and striatum, but the numberof the cells was significantly lower than the number of the model control group. The time-phase pattern of CytCmRNA in the phycocyanin group was similar to the pattern of the model control group. In the sham operation groupand the model control group, there was only a few Caspase-3-positive cells were seen in the normal cerebral tissue.In the model control group, the upregulation of Caspase-3 mRNA began 6h after ischemia, reached a maximum at24h and subsided at 48h, but still in high level. In the phycocyanin group, Caspase-3-positive cells were also mainlyin the penumbral area, but the number of the cells were significantly lower than the number of the model controlgroup. The time-phase pattern of Caspase-3 mRNA in the phycocyanin group was similar to the pattern of the modelcontrol group. Conclusion The over-expression of CytC mRNA and Caspase-3 mRNA might play a key role inischemic cerebral injury after MCAO. Phycocyanin could inhibit the over-expression of CytC mRNA and Caspase-3mRNA in the cerebral cortex, and might play an important role in the protection of ischemic neurons.

BIOREACTOR TECHNOLOGY FOR PRODUCTION OF VALUABLE ALGAL PRODUCTS

Bioreactor technology has long been employed for the production of various (mosilycheap) food and pharmaceutical products. More recently, research has been mainly focused on the devel-opment of novel bioreactor technology for the production of high - value products. This paper reports theemployment of novel bioreactor technology for the production of high-value biomass and metabolites by mi-croalgae. These high-value products include microalgal biomass as health foods, pigments including phy-cocyanin and carotenoids, and polyunsaturated fatty acids such as eicosapentaenoic acid and docsahex-aenoic acid. The processes involved include heterotrphic and mixotrophic cultures using organic sub-strates as the carbon source. We have demonstrated that these bioreactor cultivation systems are particu-larly suitable for the production of high-value products from various microalgae. These cultivation systemscan be further modified to improve cell densities and productivities by using high cell density techniquessuch as fed-batch and membrane cell recycle systems. For most of the microalgae investigated, the maxi-mum cell concentrations obtained using these bioreactor systems in our laboratories are much higher thanany so far reported in the literature.

IRON IONS INCREASE THE THERMOSTABILITY OF PHYCOCYANIN OF SPIRULINA MAXIMA

A spectral method to investigate the effect of Fe3+, Fe2+ on the thermostability ofphycocyanin (PC) of Spirulina maxima showed that iron ions prevent decrease of visible light absorbanceand fluorescence intensity of PC. Increase in denaturation temperature caused by Fe3+ was observed bythe micro - differential scanning calorimetric method. All results showed iron ions maintain the aggrega-tion stability of the PC. The absorption spectrum of phycocyanobilin (PCB, a prosthetic group of PC) withFe3+ in chloroform was quite different from that of free PCB.

Physicochemical degradation of phycocyanin and means to improve its stability:A short review

The cyanobacterium Arthrospira platensis,spirulina,is a source of pigments such as phycobiliprotein and phycocyanin.Phycocyanin is used in the food,cosmetics,and pharmaceutical industries because of its antioxidant,anti-inflammatory,and anticancer properties.The different steps involved in extraction and purification of this protein can alter the final properties.In this review,the stability of phycocyanin(pH,temperature,and light)is discussed,considering the physicochemical parameters of kinetic modeling.The optimal working pH range for phycocyanin is between 5.5 and 6.0 and it remains stable up to 45℃;however,exposure to relatively high temperatures or acidic pH decreases its half-life and increases the degradation kinetic constant.Phycobiliproteins are sensitive to light;preservatives such as mono-and disaccharides,citric acid,or sodium chloride appear to be effective stabilizing agents.Encapsulation within nano-or micro-structured materials such as nanofibers,microparticles,or nanoparticles,can also preserve or enhance its stability.

Isolation and Characterization of C-phycocyanin from Spirulina Platensis

The isolation of biliproteins from the Spirulina platensis cultured in southern China was accomplished with gel filtration on Sephacryl S 200 and chromatography on hydroxylapatite. The spectrophotometry, isoelectric point, and amino acid composition of C phycocyanin were determined, respectively.

The phycocyanin-chlorophyll-protein complexes isolated from Chroomonas placoidea

An active photosystem(PS)Ⅱparticle and two light-harvesting complexes,as well as their subcomplexes that have not been reported previously,were isolated from a cryptophyte Chroomonas placoidea by Triton X-100 sucrose density gradient centrifugation.The fluorescence spectra revealed that there were efficient energy couplings between phycocyanin(PC645)and chlorophyll(Chl)within both zonesⅢandⅣof the gradient,which were designated respectively as light-harvesting complex and PSⅡparticles whose size was 15-20 nm according to negative staining in electron microscopy.When the two complexes were further resolved into sub-complexes,the energy coupling was retained in the core PSⅡcomplex(named as zoneⅣ-2 of the sucrose gradient),which contained almost no outer antenna pigment Chl c.Sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE)showed that the PC645 components appeared in Chl-containing protein complexes were mainly the β subunit with molecular weight of 20 kDa.These results demonstrate that PC645 in this cryptophyte was structurally but preferentially combined with the light-harvesting complex and PSⅡcore.The excitation energy absorbed by PC645 could be directly transferred to Chl a(especially the long wavelength of Chl a)in the PSⅡreaction center or via the Chl a/c-protein complex.The β subunit corresponded to the terminal fl uorescence emission and might play an important role in transmitting energy from PC645 to the Chl-protein complex.The results will help in elucidating the architecture and function of the energy transfer system comprising phycobiliproteins and Chl-protein complexes in cryptophytes.