Peridinin Chlorophyll Research Articles

A method of spectral subband decomposition by simultaneous fitting the initial spectrum and a set of its derivatives

An improved method for spectral subband decomposition based on simultaneous fitting of the initial spectrum and a set of its derivatives is introduced. Additionally, a procedure for finding an optimal smoothing filter to obtain undistorted derivatives is suggested. The proposed method is demonstrated with a model spectrum as well as with experimental absorption spectra of the photosynthetic antenna complexes, peridinin–chlorophyll a–protein (PCP) and the main light-harvesting complex of higher plants (LHC II).

Flow cytometric immunophenotyping including Bcl-2 detection on fine needle aspirates in the diagnosis of reactive lymphadenopathy and non-Hodgkin's lymphoma

Fine-needle aspiration (FNA) with immunophenotyping by immunocytochemistry (IC) on cytospins has recently received increased consideration in the diagnosis of lymphoma. The aim of our study was to establish the diagnostic value of a four-color flow cytometric (FCM) panel, including cytoplasmic Bcl-2, in cytologic diagnosis of malignant non-Hodgkin's lymphoma (NHL) and reactive lymphoid hyperplasia (RH). We investigated 424 FNAs from 396 patients. FCM panel included lambda/kappa/CD19/CD5, CD23/CD10/CD20/CD19, CD4/CD7/CD8/CD3 and Bcl-2/CD10/CD19/CD3 in fluorescein isothiocyanate, phycoerythrin, and peridinin chlorophyll protein or a tandem conjugate of R-phycoerythrin and indodicarbocyanine and allophycocyanin. Bcl-2 expression was evaluated separately for gated B and T cells. In 97% of 172 RH samples, FCM was concordant with the diagnosis. FCM gave correct immunologic diagnosis in 95% of low-grade B-cell NHLs, 78% of high-grade B-cell NHLs, and 53% of T-cell lymphomas. Malignant B cells had higher Bcl-2 expression than did reactive B and T cells. This helped to establish a correct diagnosis especially in cases where no clear-cut monoclonality could be shown by kappa/lambda staining or where there was no expression of surface light chain. The highest Bcl-2 expression was found in follicular lymphomas. Our FCM panel allowed precise classification of NHL in FNA material in 89.5% of all samples. Bcl-2 staining can be recommended for primary differentiation between reactive hyperplasia and NHL.

Cardiopulmonary bypass elicits a prominent innate immune response in children with congenital heart disease

Cardiopulmonary bypass elicits a prominent innate immune response in children with congenital heart disease

Usefulness of platelet reactivity before percutaneous coronary intervention in determining cardiac risk one year later

F low cytometric analysis of platelets with the use of epitope-dependent monoclonal antibodies or fluorochrome-labeled ligands provides sensitive and specific assessment of platelet activation.1,2 Assessment of platelet function has not yet been implemented to direct antiplatelet therapy. In contrast, analogous methods are used extensively in the diagnosis and classification of malignancies, as well as to guide antineoplastic therapy.3–5 We have previously reported that flow cytometric analysis of platelet reactivity prospectively identifies those patients at high and low risk of cardiac events during the first 90 days after percutaneous coronary intervention (PCI).6 The aim of the present report was to determine whether this method provides an outcome measure at 6 months and 1 year of follow-up in patients who underwent PCI. • • • The institutional review board of the University of Vermont approved the protocol. All patients provided informed consent. Eligible nonconsecutive patients included those with symptomatic coronary artery disease, a normal creatine kinase and creatine kinase-MB at the time of the procedure, and no pretreatment with intravenous glycoprotein (GP) IIb/IIIa inhibitors. Blood was obtained shortly before PCI for assay of platelet reactivity by flow cytometry. Patients were classified into 1 of 2 groups, high reactivity and low reactivity based on the percentage of platelets capable of binding fibrinogen in response to adenosine diphosphate 0.2 M (activation of platelet GP IIb/IIIa). The median value for all patients was used to stratify the subjects. PCI was performed as clinically mandated. All patients were treated with aspirin 325 mg/daily in addition to clopidogrel 75 mg/daily for 4 weeks. The composite of myocardial infarction (MI), urgent revascularization, and repeat vascularization was assessed after 6 months and 1 year. Follow-up was obtained by telephone calls and chart review at 3, 6, and 12 months. Follow-up was completed in all but 3 of the 112 patients studied ([97.3%] 2 deaths, 1 lost to follow-up). Platelet reactivity was assessed as previously described.6 In brief, blood was anticoagulated with corn trypsin inhibitor. Platelet reactivity was determined with respect to the activation of GP IIb/IIIa. Blood in 5l aliquots was added to microcentrifuge tubes containing HEPES-Tyrodes buffer and fluorochrome-labeled ligands. Adenosine diphosphate (0.2 and 1 M) was used to activate platelets. A peridinin chlorophyll protein conjugated antibody to GP IIIa was used as an activation-independent marker of platelets. Fluorescein isothiocyanate conjugated fibrinogen was used to assess the activation of GP IIb/IIIa. The reaction mixture was incubated at room temperature for 15 minutes. Subsequently, platelets were fixed and red blood cells were lysed with Optilyse-C (Immunotech, Marseille, France). Association of ligands with platelets was determined with a fluorescence-activated cell sorter. Platelets were identified on the basis of particle size and on association with CD61 antibody. Descriptive statistics were implemented for all measures. Comparison of the cumulative incidence of events in high and low reactivity groups was conducted using 2 2 contingency table methods and Fisher’s exact test for dichotomous measures. Comparison of the incidence of clinical outcomes over time in the high and low reactivity groups were From the University of Vermont College of Medicine, Burlington, Vermont. Dr. Kabbani’s address is: 111 Colchester Avenue, Cardiology Unit—Fletcher Allen Health Care—McClure 1, Burlington, Vermont 05401. E-mail: Samer.Kabbani@vtmednet.org. Manuscript received September 13, 2002; revised manuscript received and accepted December 4, 2002. FIGURE 1. Kaplan-Meier curves of the probability of freedom from the composite end point at 1 year. Platelet reactivity was assessed by flow cytometric determination of the capacity of platelets to bind fibrinogen in response to adenosine diphosphate 0.2 M. The divergence of the curves during the initial 24 hours predominantly reflects a higher incidence of periprocedural MI in those with high platelet reactivity. The highest incidence of cardiac events occurred during the first 6 months after PCI.

Sex differences in in vitro pro-inflammatory cytokine production from peripheral blood of multiple sclerosis patients

We compared the patterns of the pro-inflammatory cytokines, interferon-γ (IFN-γ), interleukin-2 (IL-2) and tumor necrosis factor-α (TNF-α), and the anti-inflammatory cytokines, interleukin-10 (IL-10) and tumor growth factor-β (TGF-β) from peripheral blood of male and female patients with relapsing–remitting (RR) and secondary progressive (SP) forms of multiple sclerosis (MS). The relationships between pro-inflammatory cytokines and disability (expanded disability status scale, EDSS) were also examined. Peripheral blood anti-coagulated with heparin was obtained from 47 MS patients (30 women and 17 men) and activated with phorbol-12-myristate 13 acetate (PMA) and ionomycin in the presence of brefeldin A and stained for flow cytometry with fluorescently labeled antibodies against intracellular IFN-γ, TNF-α, IL-2, IL-4 and IL-10. The T cells were delineated with peridinin chlorophyll protein (Per-CP) labeled anti-CD3 antibody. The stained samples were analyzed on a flow cytometer to assess the intracellular pro-inflammatory cytokine patterns. The levels of interleukin-10 (IL-10) and tumor growth factor-β (TGF-β) were measured in plasma using enzyme-linked immunoassay. The percentage of TNF-α-producing CD3 positive cells was significantly higher ( P=0.045) in men (mean±S.D., 39±13%) than in women (mean±S.D., 29±13%) RR-MS patients. The percentage of CD3 positive cells producing IFN-γ was significantly correlated with EDSS in females but not in males (Spearman rank correlation r S=0.49, P=0.018). The secretion of the pro-inflammatory cytokines, IFN-γ and TNF-α, is influenced by gender in MS patients and may contribute to the sexual dimorphism of MS.

Carotenoid to chlorophyll energy transfer in the peridinin-chlorophyll-a-protein complex involves an intramolecular charge transfer state.

Carotenoids are, along with chlorophylls, crucial pigments involved in light-harvesting processes in photosynthetic organisms. Details of carotenoid to chlorophyll energy transfer mechanisms and their dependence on structural variability of carotenoids are as yet poorly understood. Here, we employ femtosecond transient absorption spectroscopy to reveal energy transfer pathways in the peridinin-chlorophyll-a-protein (PCP) complex containing the highly substituted carotenoid peridinin, which includes an intramolecular charge transfer (ICT) state in its excited state manifold. Extending the transient absorption spectra toward near-infrared region (600-1800 nm) allowed us to separate contributions from different low-lying excited states of peridinin. The results demonstrate a special light-harvesting strategy in the PCP complex that uses the ICT state of peridinin to enhance energy transfer efficiency.

Removal of T and B lymphocytes by in-line filtration: evaluation of the efficiency of a polyester filter type (Pall WBF-2) by flow cytometric counting.

The aim of this study was to investigate whether in-line filtration, using a polyester filter for the preparation of red cell concentrates (RCC) and plasma (PL), leads to an altered proportion of T and B lymphocytes in the fraction of residual white blood cells (WBC). The capacity of Pall WBF-2 in-line filters to reduce the numbers of T and B lymphocytes from red blood cell concentrates (RCC) and plasma (PL) of 22 donations was investigated by three-colour flow cytometry (FC) using the Tritest-Trucount kit. T and B lymphocytes were identified using monoclonal antibodies (mAbs) against CD3, CD19 and CD45, conjugated with fluorescein isothiocyanate, phycoerythrin or peridinin chlorophyll protein-A, respectively. As the number of B cells was below the detection limit of the FC method, WBC of the respective blood components of healthy donors were concentrated 25-fold by Percoll density-gradient centrifugation. In this fraction the absolute numbers of T and B cells, as well as their ratio, were determined using the Attractor software, which provides a discrimination of rare cell counts from FC in relation to debris. The mean numbers, as well as minima and maxima of T and B lymphocytes per unit, were as follows. T cells in RCC: 4.51 x 10(3) (1.68 x 10(2)-4.09 x 10(4)) and in PL: 1.35 x 10(3) (2.21-1.78 x 10(4)); B cells in RCC: 2.33 x 10(3) (7.10 x 10(1)-9.15 x 10(3)) and in PL: 2.33 x 102 (7.5 x 10(2)-2.8 x 10(3)). T cells were retained, on average, at a higher level than B cells: 3.01 times higher in RCC and 1.01 times higher in PL. After filtration, the ratio of T and B lymphocytes changed in RCC (1.95 : 1) compared with unfiltered blood, where it was 5.83 : 1. In PL the ratio did not change notably compared to unfiltered blood. The results of this research show that cell concentration (using gradient centrifugation) in combination with an appropriate FC acquisition and analysis procedure, allows both residual T and B lymphocytes (being under the detection limit without cell concentration) to be determined.

Two-Photon Excitation Study of Peridinin in Benzene and in the Peridinin Chlorophyll a-Protein (PCP)

Peridinin chlorophyll a-protein (PCP) is a unique light harvesting protein found in dinoflagellates, that contains a large amount of the carotenoid peridinin. Carotenoids have unusual spectroscopic properties due to theirapproximate C 2 h symmetry, which makes transitions from their ground states to their S 1 (S 2 ) states one-photon forbidden (allowed). To gain information about one-photon forbidden electronic states in peridinin, fluorescence excitation spectra were measured after two-photon excitation for peridinin in benzene and in the PCP. The samples were excited using 920-1320 nm light. Fluorescence of the isolated peridinin S, state was then measured at 750 nm. In PCP, the excited peridinin transfers energy to chlorophyll whose fluorescence was monitored at 670 nm. Surprisingly, two-photon absorption was observed in both the peridinin S 1 and S 2 regions, with the spectrum slightly red-shifted in the protein sample. The peridinin S, energy was found to be higher than that of typical light harvesting carotenoids, making its S 1 state very close in energy to its S 2 state. We suggest that peridinin's polar groups, symmetry breaking, and possible mixing of electronic states lead to two-photon character of the normally one-photon allowed S 0 -S 2 transition.

Energy Transfer in the Peridinin Chlorophyll- a Protein of Amphidinium carterae Studied by Polarized Transient Absorption and Target Analysis

The peridinin chlorophyll- a protein (PCP) of dinoflagellates differs from the well-studied light-harvesting complexes of purple bacteria and green plants in its large (4:1) carotenoid to chlorophyll ratio and the unusual properties of its primary pigment, the carotenoid peridinin. We utilized ultrafast polarized transient absorption spectroscopy to examine the flow of energy in PCP after initial excitation into the strongly allowed peridinin S 2 state. Global and target analysis of the isotropic and anisotropic decays reveals that significant excitation (25–50%) is transferred to chlorophyll- a directly from the peridinin S 2 state. Because of overlapping positive and negative features, this pathway was unseen in earlier single-wavelength experiments. In addition, the anisotropy remains constant and high in the peridinin population, indicating that energy transfer from peridinin to peridinin represents a minor or negligible pathway. The carotenoids are also coupled directly to chlorophyll- a via a low-lying singlet state S 1 or the recently identified S CT. We model this energy transfer time scale as 2.3 ± 0.2 ps, driven by a coupling of ∼47 cm −1. This coupling strength allows us to estimate that the peridinin S 1/S CT donor state transition moment is ∼3 D.

Förster Excitation Energy Transfer in Peridinin-Chlorophyll- a-Protein

Time-resolved fluorescence anisotropy spectroscopy has been used to study the chlorophyll a (Chl a) to Chl a excitation energy transfer in the water-soluble peridinin–chlorophyll a–protein (PCP) of the dinoflagellate Amphidinium carterae. Monomeric PCP binds eight peridinins and two Chl a. The trimeric structure of PCP, resolved at 2 Å (Hofmann et al., 1996, Science. 272:1788–1791), allows accurate calculations of energy transfer times by use of the Förster equation. The anisotropy decay time constants of 6.8 ± 0.8 ps ( τ 1) and 350 ± 15 ps ( τ 2) are respectively assigned to intra- and intermonomeric excitation equilibration times. Using the ratio τ 1/ τ 2 and the amplitude of the anisotropy, the best fit of the experimental data is achieved when the Q y transition dipole moment is rotated by 2–7° with respect to the y axis in the plane of the Chl a molecule. In contrast to the conclusion of Moog et al. (1984, Biochemistry. 23:1564–1571) that the refractive index ( n) in the Förster equation should be equal to that of the solvent, n can be estimated to be 1.6 ± 0.1, which is larger than that of the solvent (water). Based on our observations we predict that the relatively slow intermonomeric energy transfer in vivo is overruled by faster energy transfer from a PCP monomer to, e.g., the light-harvesting a/c complex.

Measurement of absolute concentration and viability of CD34+ cells in cord blood and cord blood products using fluorescent beads and cyanine nucleic acid dyes

Conventional flow cytometric methods for CD34+ cell counting may be affected by the high number of nucleated red blood cells or nonviable cells in cord blood and its products. We developed a simple flow cytometric no-wash procedure that avoids these shortcomings because it provides absolute CD34+ cell counts and assesses cell viability. Samples were incubated with phycoerythrin (PE)-labeled anti-CD34 (Becton Dickinson Immunocytometry Systems [BD], San Jose, CA) and peridinin chlorophyll protein (PerCP)-labeled anti-CD45 (BD) in bead-containing TRUCOUNT tubes (BD). After red cell lysis with a fixative-free reagent, the impermeant nucleic acid dye YO-PRO-1 (Molecular Probes, Eugene, OR) was added and samples were analyzed on a single-laser FACSCalibur (BD). A comparison with the ProCOUNT progenitor cell assay (BD) in 57 samples revealed excellent correlation of results (r = 0.98, intercept -0.2 cells/microl, slope 1.01). Precision studies conveyed coefficients of variation of 6.4 and 8.9% at concentrations of 35 and 16 CD34+ cells/microl, respectively. In untreated and leukocyte-enriched cord blood 4.5+/-3.8% of CD34+ cells were stained by YO-PRO-1, representing apoptotic or necrotic cells. In post-thawing cryopreserved samples this number increased to 10.4+/-5.5%. Isotype controls showed very low blank values of viable cells (0.1+/-0.4 cells/microl, maximum 2.4) and seemed unnecessary. We found no washing-related alteration of results in 35 samples, indicating that the method may also be performed with cell washing. Replacing YO-PRO-1 with TO-PRO-3 facilitated four-color analysis of subpopulations of viable CD34+ cells on a FACSCalibur equipped with a second (diode) laser. We found the proposed method to be a rapid, efficient, and flexible procedure that improved validity of CD34+ cell counts.

Light-Regulated Transcription of Genes Encoding Peridinin Chlorophyll a Proteins and the Major Intrinsic Light-Harvesting Complex Proteins in the DinoflagellateAmphidinium carterae Hulburt (Dinophycae)1

In the dinoflagellate Amphidinium carterae, photoadaptation involves changes in the transcription of genes encoding both of the major classes of light-harvesting proteins, the peridinin chlorophyll a proteins (PCPs) and the major a/c-containing intrinsic light-harvesting proteins (LHCs). PCP and LHC transcript levels were increased up to 86- and 6-fold higher, respectively, under low-light conditions relative to cells grown at high illumination. These increases in transcript abundance were accompanied by decreases in the extent of methylation of CpG and CpNpG motifs within or near PCP- and LHC-coding regions. Cytosine methylation levels in A. carterae are therefore nonstatic and may vary with environmental conditions in a manner suggestive of involvement in the regulation of gene expression. However, chemically induced undermethylation was insufficient in activating transcription, because treatment with two methylation inhibitors had no effect on PCP mRNA or protein levels. Regulation of gene activity through changes in DNA methylation has traditionally been assumed to be restricted to higher eukaryotes (deuterostomes and green plants); however, the atypically large genomes of dinoflagellates may have generated the requirement for systems of this type in a relatively "primitive" organism. Dinoflagellates may therefore provide a unique perspective on the evolution of eukaryotic DNA-methylation systems.

Circular dichroism (CD) study of peridinin[ndash ]chlorophyll a protein (PCP) complexes from marine dinoflagellate algae The tetramer approach

The absorption and circular dichroism spectra of PCP (peridinin–chlorophyll a protein) light-harvesting complexes from Glenodiniumsp. and Gonyaulaxpolyedra are studied in terms of vibronic coupling theory. Analysis based on a tetramer model allows the determination of the relative positions of peridinin molecules in the PCP complexes studied. The tetrameric arrangementof four peridinins around the chlorophyll a is suggested to favour the efficient transfer of energy from the peridinin to thechlorophyll. The simple arguments presented suggest that the energy transfer from peridin to chlorophyll might occur from theΨ1± states of the peridinin tetramer to the Bx, and By states of the chlorophyll a.

The structure and organization of the luciferase gene in the photosynthetic dinoflagellate Gonyaulax polyedra.

The structural features of dinoflagellate nuclei are distinct from those of other eukaryotes in several respects, and the mechanisms of DNA replication and transcription are almost completely unknown. In this study we investigated the structure and organization of the gene coding for luciferase (LCF), the enzyme catalyzing the bioluminescent reaction in the dinoflagellate Gonyaulax polyedra. The genomic lcf sequence, including its flanking regions, were completely determined. The transcription initiation site was identified using primer extension and RNase protection assays. Sequence analysis shows that, like the luciferin-binding protein gene (lbp) from G. polyedra, lcf does not contain introns. Analysis of results from genomic Southern blots, inverse PCR, and sequencing revealed that the lcf gene is organized as tandem repeats in the genome. The spacer region between the lcf genes, which very likely contains the promoter elements necessary for transcription initiation, has no TATA box or other known promoter elements or consensus sequences. However, a conserved sequence motif was identified by comparing the two intergene spacer regions of lcf and the peridinin chlorophyll protein gene, pcp; a novel 13 nt sequence, CGTGAACGCAGTG, which might be a dinoflagellate promoter, was found to be present in both.

Coexpression of CD69 and HLADR activation markers on synovial fluid T lymphocytes of patients affected by rheumatoid arthritis: a three-colour cytometric analysis.

The aim of the present study was to evaluate the coexpression of very early (CD69), early (CD25) and late (HLADR) antigens and to analyse the mean fluorescence intensity (MFI) of such activation markers on synovial fluid (SF) and peripheral blood (PB) lymphocytes of patients affected by rheumatoid arthritis (RA) and other types of chronic synovitis (OCS). A three colour cytometric analysis was performed using a peridinin chlorophyll protein conjugated anti-CD3 antibody in combination with fluorescein isothiocyanate or phycoerythrin labelled anti-CD69, anti-HLADR, anti-CD25 monoclonal antibodies (mAbs). A T cell gating method was utilized, so that three sets of bivariant dot plot quadrant displays were obtained (CD69/HLADR, CD69/CD25, CD25/HLADR). A large percentage of SF T lymphocytes in RA showed the coexpression of very early and late activation antigens (CD3 + CD69 + HLADR +), whereas CD3 + CD69 + CD25 + bearing cells and CD3 + CD25 + HLADR + lymphocytes were only a small percentage. Similar results were obtained in patients with OCS, although to a lesser extent. No statistically significant differences in MFI of CD69 and HLADR positive SF T cells between RA and OCS were observed. The CD69 + CD25-HLADR + T cell subset is the most commonly represented in the synovial environment, among those we have evaluated; this phenotype may be characteristic of chronic inflammatory arthritis.

Carotenoid interactions in peridinin chlorophyll a proteins from dinoflagellates. Evidence for optical excitions and triplet migration

Optical and magnetic resonance spectroscopy has been used to investigate two peridinin–chlorophyll a–protein (PCP) complexes constituting the peripheral antenna of the photosystem of two dinoflagellate species. One protein contains a cluster of four peridinins and one chlorophyll molecule, the other contains two such clusters in a ‘quasi’ dimer of the former. Evidence of intra-cluster excitonic interactions between peridinins is provided by low-temperature absorption and circular dichroism spectra. Peridinin triplets are detected in zero-field magnetic resonance spectroscopy by both optical emission and absorption. Interaction among peridinin molecules causes a fast intra-cluster and a slow inter-cluster triplet migration. The origin of the interactions is discussed by correlating optical and magnetic spectroscopic data.

Measurements of In Vivo Megakaryocytopoiesis: Studies in Nonhuman Primates and Patients

In vivo megakaryocytopoiesis was directly analyzed for megakaryocyte (MK) number and mass, expression of lineage-specific and myeloid differentiation markers, and cell maturation as determined by size, granularity and ploidy. Using a rapid method for multiparameter correlative analysis with three-color flow cytometry (FCM) and a single-argon-ion-laser analyzer, cell DNA in aspirated marrow was stained with 7-amino-actinomycin D, and surface membrane receptors were analyzed with antibodies and cytokines labeled with fluorescein, phycoerythrin and peridinin chlorophyll protein. MKs expressing glycoprotein (GP) IIb/IIIa were enumerated in relation to the nucleated erythroid precursors expressing glycophorin A, and MK diameters were measured by time-of-flight technique. In human marrow (n = 10) the average MK diameter is 37 microm (range: 21 microm for 2N to 56 microm for 64N cells), volume is 26 x 10(3) fL, and MK number is 10 x 10(6)/kg, giving a total MK mass of 26 x 10(10) fL/kg. The modal ploidy is 16N. In essential thrombocythemia patients (n = 10) with a mean platelet count of 907 +/- 23 x 10(6)/L, MK number and volume increased twofold with modal ploidy of 32N, and MK mass fourfold the normal value. After reducing the platelet count to 353 +/- 42 x 10(6)/L with anagrelide therapy, MK number and volume decreased with modal ploidy of 16N, resulting in reduced MK mass by 50%. By contrast, patients with chronic myelogenous leukemia (n = 3) showed an increase in small MKs with a modal ploidy of 8N. In non-human primates, treatment with interleukin 6 or GM-CSF increased MK volume and ploidy with a variable increase in cell number and platelet counts. Treatment with recombinant human MK growth and development factor (n = 6, 5 microg/kg for 28 days) increased platelet count fivefold, MK number fourfold, MK volume twofold and total mass sevenfold. Using three-color FCM, marrow MKs labeled for GPIIb/IIIa and stained for DNA expressed high levels of von Willebrand factor with a high resolution of 2N/4N MKs from the total marrow cells. The expression of myeloid markers including CD36, CD45 and IgG-Fc gammaRII CDw32 correlated directly with increasing cell maturation, concordant with the expression of GPIIb/IIIa and GPIb. Conversely, the expression of HLA-DR declined with maturation. We conclude that pathophysiologic and therapeutic changes in megakaryocytopoiesis in vivo are readily quantified using FCM measurements.

Electron spin echo envelope modulations of SeO3− radicals in (NH4)3H(SeO4)2 crystals

Experimental and theoretical studies indicate that water molecules between redox partners can significantly affect their electron-transfer and possibly also the triplet–triplet energy transfer (TTET) properties when in the vicinity of chromophores. In the present work, the interaction of an intervening water molecule with the peridinin triplet state in the peridinin–chlorophyll a–protein (PCP) from Amphidinium carterae is studied by using orientation selective 2H electron spin echo envelope modulation (ESEEM) spectroscopy, in conjunction with quantum mechanical calculations. This water molecule is located at the interface between the chlorophyll and peridinin pigments involved in the photoprotection mechanism (Chl601(602)–Per614(624), for nomenclature see reference [1]), based on TTET. The characteristic deuterium modulation pattern is observed in the electron spin-echo envelopes for the PCP complex exchanged against 2H2O. Simulations of the time- and frequency-domain two-pulse and three-pulse ESEEM require two types of coupled 2H. The more strongly coupled 2H has an isotropic coupling constant (aiso) of − 0.4 MHz. This Fermi contact contribution for one of the two water protons and the precise geometry of the water molecule at the interface between the chlorophyll and peridinin pigments, resulting from the analysis, provide experimental evidence for direct involvement of this structured water molecule in the mechanism of TTET. The PCP antenna, characterised by a unity efficiency of the process, represents a model for future investigations on protein- and solvent-mediated TTET in the field of natural/artificial photosynthesis.

Nucleotide sequence of two cDNAs encoding fucoxanthin chlorophyll a/c proteins in the diatom Odontella sinensis

Two cDNA clones encoding fucoxanthin chlorophyll a/c-binding proteins (FCP) in the diatom Odontella sinensis have been cloned and sequenced. The derived amino acid sequences of both clones are identical, comparison of the corresponding nucleic acids reveals differences only in the third codon position, suggesting a recent gene duplication. The derived proteins are similar to the chlorophyll a/b-binding proteins of higher plants. The presequences for plastid import resemble signal sequences for cotranslational import rather than transit peptides of higher plants. They are very similar to the presequences of FCP proteins in the diatom Phaeodactylum, but different from the presequences of the gamma-subunit of CF0CF1 of Odontella and the peridinin chlorophyll a binding proteins (PCP) of the dinoflagellate Symbiodinium.

A novel peridinin—chlorophyll a protein (PCP) from the marine dinoflagellate Alexandrium cohorticula: A high pigment content and plural spectral forms of peridinin and chlorophyll a

A new type of peridinin—chlorophyll a protein (PCP) was isolated from the marine dinoflagellate Alexandrium cohorticula. Unlike previous studies, PCP was obtained as a single component in the presence of a protease inhibitor. The monomer had a molecular mass of 37 kDa with 12 peridinin molecules associated with 2 chl a molecules. This pigment content was much higher than that reported previously. We observed a partial amino acid sequence of the N-terminus that is novel among photosynthetic pigment—protein complexes. Magnetic circular dichroism clearly indicated that chl a in PCP had monomeric features. Multiple spectral components were suggested for both chl a and peridinin. Based on the high pigment content, the optical properties were compared with those for a reported PCP containing 4 chl a and 1 peridinin.