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1.
Pigment constitution of a photochemically active chromoprotein(ACP) isolated from the blue-green alga Anabaena cylindrica,was immunologically studied. Results confirmed our previousview that ACP is a complex of c-phycocyanin and a pigment havingabsorption peaks at 480 and 695 nm. Antisera of both ACP andphycocyanin did not significantly affect the photochemical activityof ACP. (Received August 15, 1972; ) 相似文献
2.
In vivo fluorescence excitation and absorption spectra of marine phytoplankton: I. Taxonomic characteristics and responses to photoadaptation 总被引:2,自引:0,他引:2
SooHoo Janice Beeler; Kiefer Dale A.; Collins Donald J.; McDermid I. Stuart 《Journal of plankton research》1986,8(1):197-214
Absorption and fluorescence excitation spectra were measuredfor batch cultures of five species of marine phytoplankton grownunder high and low light. These spectra were examined for propertiescharacteristic of taxonomic position and of photoadaptive response.While regions of absorption and excitation of chlorophyll afluorescence diagnostic of pigment composition were identifiable,photoadaptive response had greater influence on spectral variability.Although reduced growth irradiance caused changes in both theabsorption and fluorescence excitation spectra, the fluorescenceexcitation spectrum appears to be more sensitive to alterationsin the ambient light field for growth than does the absorptionspectrum. For a single species. the fluorescence excitationspectrum for a sample grown at low irradiance showed greaterstructure than that for the sample grown at a high irradiance.Under low light conditions, the excitation of chlorophyll afluorescence by accessory pigments increased relative to theexcitation by chlorophyll a itself The highest fluorescenceyields occur in the blue-green region of the spectrum, correspondingto bands of peak absorption by the accessory pigments. Changesin absorption spectra are less marked, but two features recur.First. in the blue-green region of the spectrum from -500560nm. absorption is enhanced in the low-light cells relative tothat of the high-light cells. Second, the ratio of absorptionat 435 nm to that at 676 nm was greater for the high-light cells.Correlating changes in pigment concentrations were observed.The influence of photoadaptation on the properties of fluorescenceexcitation spectra is as great or greater than the influenceof pigment complements characteristic of specific algal taxa. 相似文献
3.
The relationship between a photochemically active chromoprotein(ACP) (cf. ref. 1) and photosystem II was investigated withmembrane fragments of Anabaena cylindrica, A. variabilis andP. boryaman. ACP was solubilized from membrane fragments of A. cylindricabut not from those of A. variabilis or P. boryanum, when themembrane fragments had been incubated in a dilute buffer andhad lost their Hill or photosystem II activity. In A. cylindrica,ACP-solubilization always occurred, independent of photosystemII inactivation, on incubation of the membrane fragments inmedia without PEG. However, the amount of ACP solubilizationaccompanying photosystem II inactivation was twice that withoutphotosystem II inactivation. The increase in ACP solubilizationaccompanying photosystem II inactivation. The kinetics resembledthose for the decrease in 695 nm fluorescence emitted by membranefragments at 196?C (cf. 2). The ACP solubilized independent of photosystem II inactivationwas assumed to have been released during disruption of intactcells in the preparation of membrane fragments. The slow ACPsolubilization upon the inactivation of photosystem II was attributedto the pigment being bound to membranes. We assume that thephoto-reactive component of ACP, P690 (cf. 3, 4), is releasedfrom the membranes during photosystem II inactivation, and thatP690 is a component of photosystem II which emits the 695 nmfluorescence at 196?C. (Received March 22, 1974; ) 相似文献
4.
Fluorescence spectra of the pigment system at 196°Cin membrane fragments of Anabaena variabilis and A. cylindricawere investigated. The fluorescence spectra of membrane fragments having four emissionbands at 645655, 685, 695 and 725 nm were basically similarto those reported for intact cells of blue-green algae, thoughthe emission from phycocyanin (645655 nm) was far strongerwith membrane fragments than with intact algal cells. Incubation of membrane fragments of A. variabilis in a dilutebuffer (102M, pH 7.5) caused an increase in the 645 nmfluorescence and slight decreases in the 685 and 695 nm fluorescences,but had no influence on the 725 nm fluorescence. The decreasein the 685 and 695 nm fluorescences of A. cylindrica was moremarked and had the same kinetics as the inactivation of photosystemII reaction measured by DPIP-photoreduction. When membrane fragments of A. cylindrica were incubated in thebuffer solution at room temperature or in the presence of MgCl2(103M) at 0°C; phycobilin aggregates, which emittedthe 655 and 685 nm fluorescence, were solubilized. This solubilizationwas not observed with membrane fragments of A. variabilis. (Received August 31, 1972; ) 相似文献
5.
Konishi Katsuko; Ogawa Teruo; Inoue Yorinao; Shibata Kazuo 《Plant & cell physiology》1973,14(2):227-236
Lamella preparations of spinach, Chlorella, Phaeodactylum, Anabatnaand Porphyra were treated with a hydrophobic reagent, lutein,and the absorption and fluorescence spectra in the red regionbefore and after treatment were compared for changes causedby the treatment. Absorption spectra of all these preparationsunderwent the same spectral change, transformation of a bandat 684 nm into a band at 666 nm. The longer the maximum wavelengthof the red peak, the greater was the fractional absorbance decreaseat 684 nm. The content of C684 (the chlorophyll form responsiblefor the 684 nm band) in the lamellae was estimated from thefractional decreases as being progressively higher in the orderof Phaeodactylum, Porphyra, Anabatna, Chlorella and spinach.The fluorescence spectra at liquid nitrogen temperature beforetreatment showed two bands. The longer wavelength band was transformedby the treatment into a shorter wavelength band(s), as describedbelow, according to the maximum wavelengths: spinach, F735F695(or F686); Chlorella, F715F700 (or F686); Phaeodactylum, anunidentified componentF690; Anabaena, F732F685 (or F695); Porphyra,F726F683. These chlorophyll forms with fluorescence maxima between715 and 735 nm were, therefore, designated C684 based on absorptionspectrophotometry, and are considered to play a role in photosystemII. (Received August 15, 1972; ) 相似文献
6.
The endophytic cyanobacterium, Anabaena azollae, isolated from laboratory cultures of Azolla caroliniana Willd., contains three spectroscopically distinct biliproteins. About 70% of the biliprotein is c-phycocyanin (max 610 nm) and 13% is allophycocyanin (max 647 nm, shoulder 620 nm). A third pigment corresponds to phycoerythrocyanin (max 570 nm, shoulder 590 nm). In very dilute solutions of allophycocyanin, at constant pH and buffer strength, the 647 nm maximum disappears and a single max occurs at 615–620 nm. The 647 nm absorption maximum reappears upon concentrating the dilute solution. Very dilute solutions of phycoerythrocyanin exhibit a broad peak between 570 and 590 nm. Absorption spectra of c-phycocyanin are not significantly altered upon dilution. Fluorescence emission maxima of phycoerythrocyanin, c-phycocyanin, and allophycocyanin occur at 630 nm, 643 nm and 660 nm respectively, using 540 nm excitation. Two subunits, of molecular weight 16,500 () and 20,600 (), are seen in c-phycocyanin upon dissociation with SDS. Dissociation of allophycocyanin and phycoerythrocyanin with SDS yields one sizeclass of subunits, with a molecular weight of about 17,500 for allophycocyanin and 18,000 for phycoerythrocyanin.Contribution No. 684
Offprint requests to: G. A. Peters 相似文献
7.
YU Fei TANG Chong-Qin XIN Yue-Yong PENG De-Chuan LI Liang-Bi KUANG Ting-Yun LI Ji-Yun LI Zhen-Sheng 《植物学报(英文版)》2001,43(7):686-692
Surfactants are widely used in the purification and research of structure and function of the protein complexes in photosynthetic membrane. To elucidate the mechanism of interaction between surfactants and photosystem Ⅰ (PSⅠ), effects of two typical surfactants, Triton X-100 and sodium dodecyl sulfate (SDS) on PSⅠ, were studied at different concentrations. The results were: SDS led to the reduction of apparent absorption intensity and blue shift of absorption peaks; while Triton X-100 led to the decrease of apparent absorption intensity in red region and blue shift of the peak, but to the increase of apparent absorption intensity in blue region. The fourth derivative spectra show that the longwavelength (669 nm and 683 nm) absorbing chlorophyll a was affected greatly and their relative changes of absorbance were axially symmetrical. The presence of surfactant could make the long wavelength fluorescence emission decrease greatly and a new fluorescence peak appeared around 680 nm, it was obvious that the surfactant interceded the transfer of excitation energy from antenna pigments to reaction center. The surfactants might affect the microenvironment of proteins, even the structure of PSⅠ protein subunits and hence changed the binding status of pigments with protein subunits, or the pigments might be released from the subunits. All of these might affect the absorption and the transfer of excitation energy. 相似文献
8.
Okada Mitsumasa; Ohtomi Michiko; Nakayama Katsumi; Sakamoto Yohko; Satoh Hiroyuki; Konagaya Masako; Yoshizaki Makoto 《Plant & cell physiology》1987,28(8):1435-1441
Several, new, water-soluble pigments have been detected in thematured thalli of the green alga, Bryopsis maxima. Among thepigments, a major red one has been purified and characterized.The red pigment has absorption maxima at 237, 268, 331, 450,485 and 520 nm and a shoulder at 570 nm. Its fluorescence emissionspectrum has maxima at 659 and 730 nm. The pigment has minuscharge at the pH above 3.0 and is soluble in water and polarorganic solvents but not in nonpolar solvents. Its molecularweight was estimated to be 1,490. The infrared, N.m.r. and massspectra suggest that the pigment has an open tetra pyrrole structure.
5Present address: Department of Biochemistry, Nippon MedicalSchool, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113, Japan. (Received July 2, 1987; Accepted August 26, 1987) 相似文献
9.
Detection of chlorophyllide in chlorophyll-free plasma membrane preparations from Anacystis nidulans 总被引:1,自引:0,他引:1
B Hinterstoisser A Missbichler B Pineau G A Peschek 《Biochemical and biophysical research communications》1988,154(3):839-846
Plasma and thylakoid membranes were isolated and purified from the cyanobacterium Anacystis nidulans. Spectrophotometric examination of acetone extracts gave major absorption bands resulting from carotenoids and chlorophyll a in plasma and thylakoid membranes, respectively. Only a very small absorption peak at 663 nm was detected in acetone extracts of plasma membranes which, in contrast to the corresponding peak from thylakoid membranes, could not be extracted into n-hexane; methanol, on the other hand, was effective with both plasma and thylakoid membranes. Aqueous membrane suspensions excited at 435 nm gave strong fluorescence emission at 662 nm for plasma membranes, but only a very small one for thylakoid membranes which had been adjusted to equal absorbance at 678 nm. Excitation spectra of the 668 nm fluorescence emission peak in acetone extracts of plasma and thylakoid membranes were strikingly different from each other. Finally, high performance liquid chromatography afforded clear-cut preparative separation of the two "chlorophyll-like" pigments in plasma and thylakoid membranes, respectively, and identification by comparison with retention characteristics known from the literature, together with a pure chlorophyll a standard. Our results indicate that the highly fluorescent and polar "chlorophyll-like" pigment in plasma membranes of Anacystis is a chlorophyll precursor, viz. chlorophyllide a. 相似文献
10.
Mohanty P.; Braun Barbara Zilinskas; Govindjee ; Thornber J. P. 《Plant & cell physiology》1972,13(1):81-91
Emission spectra of a system I chlorophyll (Chl) -protein complex(SI Chl-P)3 and system II particles, prepared by the methodof Dietrich and Thornber (25), and by the method of Huzisigeet al. (24), respectively, were measured at room and liquidnitrogen temperatures to characterize the emission bands originatingfrom system I and system II. Room temperature and 77°K spectra clearly show that theF695 (690697 nm) fluorescence band originates from bothphotosystems. In SI Chl-P the F695 band was observed both atroom and at liquid nitrogen temperatures. At 77°K, the Chl fluorescence at 685 nm is nearly as intenseas that at 720 nm (long-wavelength band) in dilute samples ofSI Chl-P. Reabsorption of 685 nm fluorescence has distortedconsiderably the shape of emission spectra of system I publishedthus far. In dilute samples of system II, the F695 is as (ormore) intense as F685, and the F735 is drastically decreased. Additionally, it is reported here that in Cyanidium caldarium,studied to compare the in vivo system with isolated SI Chl-Pand system II preparations, the 695 nm band is present uponexcitation in both system I and system II; the ratio of thelong-wave length fluorescence (F735) to the short-wavelengthfluorescence (F685) is much higher than those in the purifiedpreparations. Conceivably, the high values, obtained in thedilute samples of algae, are due to the reabsorption of thefluorescence from the short-wavelength form of Chl in the chloroplastin vivo. Furthermore, in this alga the phycocyanin fluorescenceband is split with maxima at 655 (phycocyanin) and 665 nm (allophycocyanin)at 77°K. At room temperature, however, the allophycocyaninfluorescence predominates having a peak at about 670 nm. Therelative increase in phycocyanin fluorescence at 77°K maybe due to a decrease in the energy transfer from it to allophycocyaninin agreement with slow Förster type transfer.
2 Department of Botanical Sciences, University of California,Los Angeles, California 90024, U. S. A. (Received September 7, 1971; ) 相似文献
11.
Scanning electron microscopy and microspectrophotometry of the photoreceptors of ictalurid catfishes
A. J. Sillman S. J. Ronan E. R. Loew 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1993,173(6):801-807
The retinal photoreceptors from larval channel catfish (Ictalurus punctatus) were studied using single cell, in situ microspectrophotometry. Rods appear at 5 days after hatch; cones are present from
day one. The rods contain a visual pigment which absorbs light maximally at 540 nm. The cones contain either a green sensitive
visual pigment with peak absorbance at 535 nm or a red sensitive visual pigment with peak absorbance at 608 nm. All pigments
are based on vitamin A2. Visual pigment complement does not change with age, as photoreceptors from adultI. punctatus, I. catus andI. melas contain visual pigments virtually identical to those of the larvalI. punctatus. Regardless of age, no visual pigment with peak absorbance in the short wavelength region of the spectrum was ever observed.
Scanning electron microscopy of adultI. punctatus retinas showed large rods with long, cylindrical outer segments and smaller cones with short, tapered outer segments. The
myoids of both rods and cones are extensable. The rods, embedded in a granular tapetal material, comprise from 50 to 60% of
the photoreceptors. Only single cones are present. The data are consistent with the idea that the ictalurid catfishes spend
their entire lives in an environment deficient in blue light. 相似文献
12.
The visual pigments in the compound eye of the comma butterfly, Polygonia c-album, were investigated in a specially designed epi-illumination microspectrophotometer. Absorption changes due to photochemical conversions of the visual pigments, or due to light-independent visual pigment decay and regeneration, were studied by measuring the eye shine, i.e., the light reflected from the tapetum located in each ommatidium proximal to the visual pigment-bearing rhabdom. The obtained absorbance difference spectra demonstrated the dominant presence of a green visual pigment. The rhodopsin and its metarhodopsin have absorption peak wavelengths at 532 nm and 492 nm, respectively. The metarhodopsin is removed from the rhabdom with a time constant of 15 min and the rhodopsin is regenerated with a time constant of 59 min (room temperature). A UV rhodopsin with metarhodopsin absorbing maximally at 467 nm was revealed, and evidence for a blue rhodopsin was obtained indirectly. 相似文献
13.
The spectral properties and the ability of etyolated leaves pigments treated with organic solvent vapours (OS) for phototransformations were studied by measuring low temperature fluorescence spectra (-196 degrees C). Under the effects of OS the fluorescence at 655 nm was gradually decreased and that at 630--640 nm was increased. The effects of OS depended on the partial pressure of OS. The ability of the pigments for phototransformations was decreased with an increase in fluorescence at 630 nm. The emission maximum of fluorescence of the pigment formed in the light was shifted by 10--18 nm towards the shortwave region. Partial reversibility of the destroying effects of diethyl ester was found. A removal of the ester vapours resulted in a relative increase of fluorescence in the etyolated leaves at 640--645 nm and a decrease of the amount of "photo-inactive" pigment. The maximum of fluorescence of the pigment formed in the light was shifted towards the long-wave region (approximately 5 nm) as compared to the leaves irradiated in the presence of the ester. Partial functional reconstitution indicates that at least part of the pigment molecules are able to form a protochlorophyllide (protochlorophyll) -- protein complex, similar to the native one. 相似文献
14.
Since akinete germination is triggered by light and the action spectrum for this process has features in common with the spectra of the two photochromic pigments, phycochromes b and d, a search was made for the presence of these phycochromes in akinetes of the blue-green alga. Anabaena variabilis Kützing. Allophycocyanin-B was also looked for, since the action spectrum for akinete germination points to a possible participation of this pigment too. Isoelectric focusing was used for purification of the pigments. The different fractions were investigated for phycochromes b and d by measuring the absorbance difference spectra: for phycochrome b. 500 nm irradiated minus 570 nm irradiated, and for phycochrome d, 650 nm irradiated minus 610 nm irradiated. For determination of allophycocyanin-B. fourth derivative analysis of absorption spectra was made for some of the fractions from the isoelectric focusing column. Phycochrome b was also assayed for by measuring in vivo absorption difference spectra. The assays were positive for all three pigments. The complete photosynthetic pigment systems were also studied by in vivo fluorescence measurements on both akinetes and vegetative cells of Anabaena variabilis. Fluorescence emission and excitation spectra at selected emission wavelengths were measured at room temperature and liquid nitrogen temperature. The energy transfer from phycoerythrocyanin to phycocyanin is very efficient under all conditions, as is the energy transfer from phycocyanin to allophycocyanin at room temperature. At low temperature, however, phycocyanin is partly decoupled from allophycocyanin, particularly in the akinetes; the energy transfer from allophycocyanin to chlorophyll a is less efficient at low temperature in both types of cells, but especially in akinetes. Delayed light emission was measured for both types of cells and found to be very weak in akinetes compared to vegetative cells. From this study it would seem that akinetes lack an active photosystem II, although the 691 nm peak in the 570 nm excited low temperature fluorescence emission spectrum proves the presence of photosystem II chlorophyll, and also its energetic connection to the phycobilisomes. 相似文献
15.
A photoreactive component, P690, was isolated from ACP by successivetreatments with SDS and Triton X 100. The isolated P690 is a chromoprotein with a molecular weightof 50,000 daltons and an isoelectric point at pH 9.1. Its spectrumhas absorption maxima at 275, 450, 475, 630 and 690 nm and itemits, at 196?C, a fluorescence at 695 nm. The photochemicaloxidation-reduction reaction activity is fully retained in theP690. The isolated P690 forms a complex with phycocyanin in vitro.This complex was identical with the original ACP in all characteristicsexamined. The complex formation of P690 is specific to phycocyanin.A possible mechanism for ACP formation is discussed. (Received March 22, 1974; ) 相似文献
16.
Pigments and a UV-absorbing substance in corals and a blue-green alga living in the Great Barrier Reef 总被引:4,自引:0,他引:4
Pigments and UV-absorbing substances in several species of coralsand a blue-green alga harvested in the environs of the GreatBarrier Reef were studied by measuring the in vivo reflectionspectra of intact samples and absorption spectra of their waterextracts with a recording spectrophotometer set on a biologicalresearch vessel. Red, pink, mauve and violet colors of fourspecies of Acropora were thus found to be due to differencesin the relative content of two pigments designated as P(pigment)-560and P-590, according to the maximum wavelength in mµ oftheir major absorption peaks. A yellow species of Acropora anda red species of Pocillopora contained different pigments, P-500and P-480, respectively. All these five species of corals contained,in addition to the above pigments, a UV-absorbing substancehaving an absorption peak near 320 mµ. The contents ofthis substance in the organisms seemed to be very high as judgedfrom its band height relative to band heights of the visiblepigment bands. Blue-green algal cells harvested near the sameenvirons contained a similar UV-absorbing substance in additionto phycobilin pigments. The spectral characteristics of thepigments and the UV-absorbing substance found in the coralsand alga are presented in this paper.
1The present study was carried out in cooperation with Drs.F. T. HAXO, P. HALLDAL and S. W. JEFFREY on the research vessel,R. V. "Alpha Helix", of University of California during the1966 expedition to the Great Barrier Reef, North Queensland,Australia, and was supported by the National Science Foundationof the U. S. A. (Received December 3, 1968; ) 相似文献
17.
Zebrafish and goldfish are both diurnal freshwater fish species belonging to the same family, Cyprinidae, but their visual ecological surroundings considerably differ. Zebrafish are surface swimmers in conditions of broad and shortwave-dominated background spectra and goldfish are generalized swimmers whose light environment extends to a depth of elevated short wavelength absorbance with turbidity. The peak absorption spectrum (lambdamax) of the zebrafish blue (SWS2) visual pigment is consistently shifted to short wavelength (416 nm) compared with that of the goldfish SWS2 (443 nm). Among the amino acid differences between the two pigments, only one (alanine in zebrafish and serine in goldfish at residue 94) was previously known to cause a difference in absorption spectrum (14-nm lambdamax shift in newt SWS2). In this study, we reconstructed the ancestral SWS2 pigment of the two species by applying likelihood-based Bayesian statistics and performing site-directed mutagenesis. The reconstituted ancestral photopigment had a lambdamax of 430 nm, indicating that zebrafish and goldfish achieved short wavelength (-14 nm) and long wavelength (+13 nm) spectral shifts, respectively, from the ancestor. Unexpectedly, the S94A mutation resulted in only a -3-nm spectral shift when introduced into the goldfish SWS2 pigment. Nearly half of the long wavelength shift toward the goldfish pigment was achieved instead by T116L (6 nm). The S295C mutation toward zebrafish SWS2 contributed to creating a ridge of absorbance around 400 nm and broadening its spectral sensitivity in the short wavelength direction. These results indicate that the evolutionary engineering approach is very effective in deciphering the process of functional divergence of visual pigments. 相似文献
18.
Schubert Hendrik; Schiewer Ulrich; Tschirner Erhard 《Journal of plankton research》1989,11(2):353-359
The fluorescence characteristics of the cyanobacteria Synechocystisaquatilis Sauv., Microcystis firma (Breb. et Lenorm.) Schmidleand Synechococcus leopoliensis (Racib.) Kom. and the green algaScenedesmus quadricauda (Turp.) Breb. were examined. In thethree cyanobacteria, phycocyanin is the main accessory pigment.Phycoerythrin is not present in our investigated strains ofcyanobacteria. The highest excitation of the chlorophyll a (Chla) fluorescence of cyanobacteria resulted from light with wavelengthsof 620630 nm. A definite Kautsky effectis also evident at this wavelength. However, excitation withblue light (420520 nm) produced only very slight fluorescence.The Kautsky effect is not evident at these wavelengths, evenat high photon flux densities. For Scenedesmus, fluorescencecharacteristics typical of green algae were found. The fluorescenceexcitation of cyanobacteria at 620 nm corresponds to a photosynthesispeak in the action spectrum measured in terms of O2 production.The results underline the necessity of fluorescence measurementsat several wavelengths whenever mixed populations are involved.Such measurements also present possibilities for more accurateestimation of biomass and potential photosynthetic productionin mixed populations. 相似文献
19.
M. Cummings J. Partridge 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2001,187(11):875-889
We studied the optical microhabitat use and visual pigment variation among a group of closely related teleosts (surfperch: Embiotocidae) living along the nearshore central California coast. We employed a diver-operated spectroradiometer to record the optical microhabitat use of eight surfperch species in Monterey Bay. and microspectrophotometry to measure visual pigment absorbance for nine surfperch species. Species were dichromatic with mixtures of A1- and A2-based visual pigments exhibiting extensive maximum absorbance (lambda(max)) variation across species: 455-482 nm for SWS cones and 527-546 nm for LWS cones. Interspecific variation in sidewelling irradiance measurements (mean lambdaFmaxs) significantly accounted for 63% of the variation in surfperch LWS visual pigments and 83% of the interspecific variation in SWS visual pigments using a phylogenetically-corrected regression technique. Optimality models for maximizing relative photon capture of background radiance demonstrate that the LWS cone lambda(max) values are tuned for maximizing photon capture of the species-specific horizontal visual field, while the SWS cone lambda(max), are well offset from the dominant background radiance. This study is one of the first to demonstrate species-specific differences in habitat usage at microhabitat scales accounting for differences in photoreceptor peak absorbance among closely related, sympatric species. 相似文献
20.
Mercury, at a low concentration (3 µM) caused an enhancementin the intensity of room temperature fluorescence emitted byphycocyanin and induced a blue shift in the emission peak ofSpirulina cells indicating the alterations in the energy transferwithin the phycobilisomes. In vitro the isolated intact Spirulinaphycobilisomes from control cells exhibited only a reductionin fluorescence yield with low concentration of HgCl2 withoutbeing accompanied by changes in the emission features, whereasthe isolated phycobilisomes from mercury treated cells exhibitedthe alterations in the spectral characteristics at the levelof phycocyanin. When isolated phycocyanin and allophycocyaninwere exposed to very low concentrations of Hg2* ions, C-phycocyaninexhibited a large decrease in the absorbance in the longer wavelength(615620 nm) region, but not allophycocyanin. In addition,mercury also caused a monotonous decrease in the C-phycocyaninemission intensity at 646 nm accompanied by a blue shift to642 nm. These results on isolated C-phycocyanin suggest thatselective bleaching of beta-84 chromophore of phycocyanin isinduced by mercury. The differential effect of mercury towardsC-phycocyanin and allophycocyanin could possibly be due to thedifference in the protein conformation of phycocyanin and allophycocyanin. (Received July 11, 1990; Accepted December 17, 1990) 相似文献