Monitoring photosynthesis in individual cells of Synechocystis sp. PCC 6803 on a picosecond timescale

Picosecond fluorescence kinetics of wild-type (WT) and mutant cells of Synechocystis sp. PCC 6803, were studied at the ensemble level with a streak-camera and at the cell level using fluorescence-lifetime-imaging microscopy (FLIM). The FLIM measurements are in good agreement with the ensemble measurements, but they (can) unveil variations between and within cells. The BE mutant cells, devoid of photosystem II (PSII) and of the light-harvesting phycobilisomes, allowed the study of photosystem I (PSI) in vivo for the first time, and the observed 6-ps equilibration process and 25-ps trapping process are the same as found previously for isolated PSI. No major differences are detected between different cells. The PAL mutant cells, devoid of phycobilisomes, show four lifetimes: ∼20 ps (PSI and PSII), ∼80 ps, ∼440 ps, and 2.8 ns (all due to PSII), but not all cells are identical and variations in the kinetics are traced back to differences in the PSI/PSII ratio. Finally, FLIM measurements on WT cells reveal that in some cells or parts of cells, phycobilisomes are disconnected from PSI/PSII. It is argued that the FLIM setup used can become instrumental in unraveling photosynthetic regulation mechanisms in the future.

Mn and Co toxicity in chlorophyll biosynthesis

The metal ion-induced inhibition of tetrapyrrole biosynthesis was studied in the cyanobacterium Anacystis nidulans. The accumulation of protoporphyrin and Mg protoporphyrin due to the effect of Co(2+) and Mn(2+) treatment, respectively, pointed to two different sites of inhibition.

A comparative study of EGFR mutation screening methods in non-small cell carcinoma of lung

Epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase of the ERBB2 family that has important roles in the proliferation and metastasis of tumor cells. It is frequently overexpressed in common solid tumors and has become a favored target for orally administered small-molecule tyrosine kinase inhibitors (TKI) and monoclonal antibody-based therapy. Gain-of-function somatic mutations of the EGFR tyrosine kinase domain have been associated with the response of some patients with non-small-cell lung carcinoma to TKIs. We evaluated three methods of EGFR mutation analysis to identify an optimal assay for clinical testing based on comparison of diagnostic sensitivity, technical difficulty, and cost (Tab. 1, Fig. 1, Ref. 12).

Analysis of extended human leukocyte antigen haplotype association with Addison's disease in three populations

OBJECTIVE

Addison's disease is an organ-specific autoimmune disorder with a polygenic background. The aim of the study was to identify non-class II human leukocyte antigen (HLA) susceptibility genes for Addison's disease.

DESIGN AND METHODS

Addison's disease patients from three European populations were analysed for selected HLA-DR-DQ alleles and for 11 microsatellite markers covering approximately 4 Mb over the HLA region. Subjects were 69 patients with Addison's disease from Estonia (24), Finland (14) and Russia (31). Consecutively recruited healthy newborns from the same geographical regions were used as controls (269 Estonian, 1000 Finnish and 413 Russian). Association measures for HLA-DRB1, DQB1, DQA1 and 11 microsatellites between D6S273 and D6S2223 were taken. A low-resolution full-house typing was used for HLA class II genes, while microsatellite markers were studied using fluorescence-based DNA fragment sizing technology.

RESULTS

We confirmed that the HLA-DR3-DQ2 and the DQB1*0302-DRB1*0404 haplotypes confer disease susceptibility. In Russian patients, we also found an increase of DRB1*0403 allele, combined with DQB1*0305 allele in three out of six cases (P<0.0001). Analysis of 11 microsatellite markers including STR MICA confirmed the strong linkage in DR3-DQ2 haplotypes but DRB1*0404-DQB1*0302 haplotypes were diverse. MICA5.1 allele was found in 22 out of 24 Estonian patients, but results from Finnish and Russian patients did not support its independent role in disease susceptibility.

CONCLUSION

HLA-DRB1*0403 was identified as a novel susceptibility allele for Addison's disease. Additionally, we found no evidence of a non-class II HLA disease susceptibility locus; however, the HLA-DR3-DQ2 haplotype appeared more conserved in patient groups with high DR-DQ2 frequencies.

Epidermal growth factor receptor (EGFR) mutations in breast and cervical cancer

20101

Background: EGFR is a tyrosine kinase receptor in the HER family which is widely expressed in a number of epithelial tumors and is believed to play a key role in cell proliferation. Molecular analysis of the EGFR gene in patients with non-small-cell lung cancer have identified a distinct subset of tumors that possess specific point mutations in the tyrosine kinase region of the EGFR gene, which correlate to response to tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib. Clinical trials involving TKIs are currently under way for patients with breast and cervical cancer. While responses thus far may have been modest it is unclear whether specific EGFR mutations are present in breast and cervical cancers which identify patients with improved prognosis and better response to therapy in these cancers. Using clinical samples with 5 years of follow-up clinical data, we have set out to determine whether EGFR mutations exist in breast and cervical cancers, and how these mutations, if any, correlate with the clinical data. Methods: We plan to perform sequence analysis of the tyrosine kinase domain of the EGFR gene (exons 18–24) in 50 archival breast and 44 cervical cancer specimens using PCR amplification and sequencing of genomic DNA. Clinical information has been extracted from patient charts on samples and will be correlated with the presence of any EGFR mutations identified. Results: To date we have collected 50 breast and 44 cervical tumor blocks and have isolated genomic DNA from the specimens. Sequencing for point mutations in exons 18–24 is underway. Clinical data on the cervical cancer specimens revealed a mean age at diagnosis of 48.2 years, tumor grades that were mostly intermediate (50%) and high (45%), and all FICO stages at diagnosis (43% stage I, 30% stage II, 5% stage III, 5% stage IV). In addition the rate of recurrence was 32%, and survival rate was 82% with an average time of follow-up for the set of 4.9 years. Conclusions: Our data will further elucidate the role of point mutations in EGFR gene in breast and cervical cancer prognosis and response to therapy, and will complement data currently being collected in clinical trials using TKIs.

No significant financial relationships to disclose.

Sodium dependency of the photosynthetic electron transport in the alkaliphilic cyanobacterium Arthrospira platensis

Arthrospira (Spirulina) platensis (A. platensis) is a model organism for investigation of adaptation of photosynthetic organisms to extreme environmental conditions: the cell functions in this cyanobacterium are optimized to high pH and high concentration (150-250 mM) of Na+. However, the mechanism of the possible fine-tuning of the photosynthetic functions to these extreme conditions and/or the regulation of the cellular environment to optimize the photosynthetic functions is poorly understood. In this work we investigated the effect of Na-ions on different photosynthetic activities: linear electron transport reactions (measured by means of polarography and spectrophotometry), the activity of photosystem II (PS II) (thermoluminescence and chlorophyll a fluorescence induction), and redox turnover of the cytochrome b6f complex (flash photolysis); and measured the changes of the intracellular pH (9-aminoacridine fluorescence). It was found that sodium deprivation of cells in the dark at pH 10 inhibited, within 40 min, all measured photosynthetic reactions, and led to an alkalinization of the intracellular pH, which rose from the physiological value of about 8.3-9.6. These were partially and totally restored by readdition of Na-ions at 2.5-25 mM and about 200 mM, respectively. The intracellular pH and the photosynthetic functions were also sensitive to monensin, an exogenous Na+/H+ exchanger, which collapses both proton and sodium gradients across the cytoplasmic membrane. These observations explain the strict Na+-dependency of the photosynthetic electron transport at high extracellular pH, provide experimental evidence on the alkalization of the intracellular environment, and support the hypothesized role of an Na+/H+ antiport through the plasma membrane in pH homeostasis (Schlesinger et al. (1996). J. Phycol. 32, 608-613). Further, we show that (i) the specific site of inactivation of the photosynthetic electron transport at alkaline pH is to be found at the water splitting enzyme; (ii) in contrast to earlier reports, the inactivation occurs in the dark and, for short periods, without detectable damage in the photosynthetic apparatus; and (iii) in contrast to high pH, Na+ dependency in the neutral pH range is shown not to originate from PSII, but from the acceptor side of PSI. These data permit us to conclude that the intracellular environment rather than the machinery of the photosynthetic electron transport is adjusted to the extreme conditions of high pH and high Na+ concentration.

Alternate routes to conformational specificity in a Greek key beta barrel protein

The N-terminal domain of protein S, a Greek key calcium-binding protein from Myxococcus xanthus, forms an atypical molten globule in the calcium-free state. The structure of this state is characterized by significant conformational fluctuations, which are localized to a subdomain that is not contiguous along the polypeptide chain. The conformational instability of this subdomain appears to arise from repulsive electrostatic interactions of four acidic side chains that are clustered together but are removed from the calcium-binding sites. This domain can be induced to form a native-like state through two different routes, calcium binding or reduction of pH. Acid-induced folding stabilizes the locally unfolded subdomain by selectively removing repulsive interactions without significantly affecting global stability. In contrast, calcium binding appears to increase local stability indirectly by causing global stabilization.

Calexcitin B is a new member of the sarcoplasmic calcium-binding protein family

Calexcitin (CE) is a calcium sensor protein that has been implicated in associative learning. The CE gene was previously cloned from the long-finned squid, Loligo pealei, and the gene product was shown to bind GTP and modulate K(+) channels and ryanodine receptors in a Ca(2+)-dependent manner. We cloned a new gene from L. pealei, which encodes a CE-like protein, here named calexcitin B (CE(B)). CE(B) has 95% amino acid identity to the original form. Our sequence analyses indicate that CEs are homologous to the sarcoplasmic calcium-binding protein subfamily of the EF-hand superfamily. Far and near UV circular dichroism and nuclear magnetic resonance studies demonstrate that CE(B) binds Ca(2+) and undergoes a conformational change. CE(B) is phosphorylated by protein kinase C, but not by casein kinase II. CE(B) does not bind GTP. Western blot experiments using polyclonal antibodies generated against CE(B) showed that CE(B) is expressed in the L. pealei optic lobe. Taken together, the neuronal protein CE represents the first example of a Ca(2+) sensor in the sarcoplasmic calcium-binding protein family.

Bioenergetic responses of Synechocystis 6803 fatty acid desaturase mutants at low temperatures

Fatty acid composition of the membrane lipids in the mesophilic cyanobacterium Synechocystis sp. PCC 6803 was altered in earlier work by targeted mutagenesis of genes for fatty acid desaturases. In this work, cells of several mutant strains, depleted in the unsaturated fatty acids in membrane lipids, were grown at 34 degrees C. Spheroplasts (permeabilized cells) were prepared by lysozyme digestion of the cell wall followed by gentle osmotic shock. The bioenergetic parameters ATP formation, electron transport, and H+ uptake were measured at various temperatures. All three bioenergetic parameters for spheroplasts from wild-type cells (which had abundant polyunsaturated fatty acids) were active down to the lowest temperatures used (1 degrees - 2 degrees C). In two strains, which lacked the capacity to desaturate fatty acids at the A 12 position and at the A 12 and A6 positions (designated as desA- and desA-/desD-, respectively), the spheroplasts lost the capacity to form ATP (measured as phenazine methosulfate cyclic phosphorylation) at about 5 degrees C but retained electron transport (water oxidation-dependent ferricyanide reduction) and H+ uptake linked to phenazine methosulfate cyclic electron transport. It appears that the absence of the unsaturation of fatty acids in the A 12 and A6 positions blocks the ability of the photosynthetic membranes to couple a bioenergetically competent proton-motive force to the ATP formation mechanism at temperatures below 5 degrees C. It remains to be determined whether the loss of ATP formation in the mutant strains is the failure of available protons to properly flow into the CF0CF1-ATP synthase or a failure in the CF1 part of the complex in coupling the dissipative H+ flow to the enzyme mechanism of the synthase.

Gene expression and gene therapy in experimental duodenal ulceration

Gastroduodenal ulceration is still poorly understood and changes in gene expression may provide new mechanistic insights. Previously, we demonstrated that angiogenic growth factors are potent ulcer healing agents, and the synthesis of bFGF, PDGF and VEGF is enhanced early in duodenal ulcer healing. The initial molecular event in duodenal ulceration seems to be the organ-specific early release of ET-1 in the pre-ulcerogenic stages after the administration of duodenal ulcerogen cysteamine in rats. We also briefly review here data from literature indicating a central role of ET-1 in gastroduodenal ulceration. After studying the involvement of immediate early genes (e.g. egr-1, Sp1) in ulcer development, we now investigated expression of other genes in the duodenal mucosa in the early stages of chemically induced duodenal ulceration in rats. Following a brief review of principles of gene expression and gene therapy, we review our preliminary gene expression studies, involving monitoring about 1200 genes which revealed about 160 signals and prominent changes in about 30 genes in the early stages of experimental duodenal ulceration. Cysteamine enhanced ET-B receptor gene expression in 30 min, while transcription factors (MAX, STAT 3) showed increased expression in 12 h. We recently also initiated gene therapy studies to enhance the local synthesis of PDGF and VEGF to accelerate duodenal ulcer healing, using a single dose of naked DNA (ND) or adenoviral (AV) vectors of VEGF and PDGF in rats with cysteamine-induced duodenal ulcers. Gene therapy with ND or AV of VEGF or PDGF significantly accelerated chronic duodenal ulcer healing, and increased levels of VEGF and PDGF were detected by Western blotting and ELISA in duodenal mucosa after both VEGF and PDGF gene therapy. Thus, gene expression studies provide new insights into the molecular mechanisms of duodenal ulceration and VEGF or PDGF gene therapy seems to be a new option to achieve a rapid ulcer healing.

Membrane dynamics as seen by fourier transform infrared spectroscopy in a cyanobacterium, Synechocystis PCC 6803. The effects of lipid unsaturation and the protein-to-lipid ratio

The roles of lipid unsaturation and lipid-protein interactions in maintaining the physiologically required membrane dynamics were investigated in a cyanobacterium strain, Synechocystis PCC 6803. The specific effects of lipid unsaturation on the membrane structure were addressed by the use of desaturase-deficient (desA(-)/desD(-)) mutant cells (which contain only oleic acid as unsaturated fatty acid species) of Synechocystis PCC 6803. The dynamic properties of the membranes were determined from the temperature dependence of the symmetric CH(2) stretching vibration frequency, which is indicative of the lipid fatty acyl chain disorder. It was found that a similar membrane dynamics is maintained at any growth temperature, in both the wild-type and the mutant cell membranes, with the exception of mutant cells grown at the lower physiological temperature limit. It seems that in the physiological temperature range the desaturase system of the cells can modulate the level of lipid desaturation sufficiently to maintain similar membrane dynamics. Below the range of normal growth temperatures, however, the extent of lipid disorder was always higher in the thylakoid than in the cytoplasmic membranes prepared from the same cells. This difference was attributed to the considerable difference in protein-to-lipid ratio in the two kinds of membranes, as determined from the ratio of the intensities of the protein amide I band and the lipid ester C&z.dbnd6;O vibration. The contributions to the membrane dynamics of an ab ovo present 'structural' lipid disorder due to the protein-lipid interactions and of a thermally induced 'dynamic' lipid disorder could be distinguished.

The tolerance of cyanobacterium Cylindrospermopsis raciborskii to low-temperature photo-inhibition affected by the induction of polyunsaturated fatty acid synthesis

Acyl-lipid desaturation introduces double bonds (unsaturated bonds) at specifically defined positions of fatty acids that are esterified to the glycerol backbone of membrane glycerolipids. Desaturation patterns of the glycerolipids of Cylindrospermopsis raciborskii, a filamentous cyanobacterium, were determined in cells grown at 35 degrees C and 25 degrees C. The lowering of the growth temperature from 35 degrees C to 25 degrees C resulted in a considerable accumulation of polyunsaturated octadecanoic fatty acids in all lipid classes. The tolerance to low-temperature photo-inhibition of the C. raciborskii cells grown at 25 degrees C and 35 degrees C was also compared. The lower growth temperature increased the tolerance of C. raciborskii cells. These results strengthen the importance of polyunsaturated glycerolipids in the tolerance to environmental stresses and may give a physiological explanation for the determinative role of C. raciborskii in algal blooming in Lake Balaton (Hungary).

Induction of polyunsaturated fatty-acid synthesis enhances tolerance of a cyanobacterium, Cylindrospermopsis raciborskii, to low-temperature photoinhibition

Acyl-lipid desaturation introduces double bonds (unsaturated bonds) at specifically defined positions of fatty acids that are esterified to the glycerol backbone of membrane glycerolipids. Desaturation pattern of the glycerolipids of Cylindrospermopsis raciborskii (C. raciborskii), a filamentous cyanobacterial strain, was determined in cells grown at 35 degrees C and 25 degrees C. The lowering of the growth temperature from 35 degrees C to 25 degrees C resulted in a considerable accumulation of polyunsaturated octadecanoic fatty acids in all lipid classes. Lipid unsaturation of C. raciborskii was also compared to Synechocystis PCC6803. In C. raciborskii cells, a shift in growth temperature induced a much more pronounced alteration in the desaturation pattern of all lipid classes than in Synechocystis PCC6803. The tolerance to low-temperature photoinhibition of the C. raciborskii cells grown at 25 degrees C and 35 degrees C was also compared to the tolerance of Synechocystis cells grown at the same temperatures. Lower growth temperature increased the tolerance of C. raciborskii cells but not that of Synechocystis cells. These results strengthen the importance of polyunsaturated glycerolipids in the tolerance to environmental stresses and may give a physiological explanation for the determinative role of C. raciborskii strain in algal blooming in the Lake Balaton (Hungary).

Non-class II HLA gene associated with type 1 diabetes maps to the 240-kb region near HLA-B

Several studies provide evidence that in addition to the DQ-DR genes, HLA contains another uncharacterized gene or genes associated with type 1 diabetes. Our aim was to investigate the effect of this gene independently of the DQ-DR genes and to localize it with a matched case-control study. More than 1,400 patients and 30,000 control individuals from Finland were studied. They were first genotyped for the selected alleles of the HLA-DQB1, -DQA1, and -DRB1 genes. For the DR3/4(0404) genotype, 75 patients and 181 control subjects were stratified, and 241 patients and 354 controls were stratified for the DR3/4(0401) genotype. Ten microsatellite markers in the HLA class III and I regions (D6S273, TNFa, C12A, STR MICA, MIB, C125, C143, C245, C3211, and MOGc) and selected alleles of the HLA-A and HLA-B genes were studied. In the DR3/4(0404)-stratified group, we found that markers located between C12A and C143 near the HLA-B gene confer a strong additional diabetes association. This was confirmed by the population differentiation test in both DR3/4(0404)- and DR3/4(0401)-stratified groups. Our data indicate that an additional gene associated with type 1 diabetes is located in the 240-kb region near HLA-B. We excluded STR MICA polymorphism as a mutation responsible for diabetes association.

Direct evidence for requirement of phosphatidylglycerol in photosystem II of photosynthesis

Phosphatidylglycerol (PG) is considered to play an important role in the ordered assembly and structural maintenance of the photosynthetic apparatus in thylakoid membranes. However, its function in photosynthesis remains poorly understood. In this study we have identified a pgsA gene of Synechocystis sp. PCC6803 that encodes a PG phosphate synthase involved in the biosynthesis of PG. A disruption of the pgsA gene allowed us to manipulate the content of PG in thylakoid membranes and to investigate the function of PG in photosynthesis. The obtained pgsA mutant could grow only in the medium containing PG, and the photosynthetic activity of the pgsA mutant dramatically decreased with a concomitant decrease of PG content in thylakoid membranes when the cells grown in the presence of PG were transferred to the medium without PG. This decrease of photosynthetic activity was attributed to the decrease of photosystem (PS)II activity, but not to the decrease in PSI activity. These findings demonstrate that PG is essential for growth of Synechocystis sp. PCC6803 and provide the first direct evidence that PG plays an important role in PSII.

Review article: transcription factors and growth factors in ulcer healing

This review is focused on recent investigations demonstrating a pharmacological and pathophysiologic role in gastroduodenal ulceration for growth factors such as basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF), as well as for transcription factors. Our experiments revealed accelerated healing, without decreased gastric acid secretion, of chronic cysteamine-induced duodenal ulcers in rats treated daily for 3 weeks with intragastric administration of bFGF, PDGF or VEGF. Our recent studies also indicate a pathophysiological role of endogenous growth factors in the natural history of experimental duodenal ulcer development and healing. More recently, we investigated the genetic regulation of these growth factors in experimental duodenal ulceration. Since gene expression is most effectively controlled by transcription factors, proteins that bind to cis-acting elements of DNA and guide the binding of polymerase II to start the transcription of specific mRNA, we tested the hypothesis that the expression of IEGs and their transcription factor products, such as Egr-1 and Sp1, might precede the increased synthesis of bFGF, PDGF and VEGF in duodenal ulcer healing. Indeed, the duodenal ulcerogen cysteamine, but not its nonulcerogen and toxic analogue ethanolamine, rapidly increased duodenal (but not gastric) mucosal levels of ET-1, which was followed by enhanced expression of Egr-1 and a decrease in Sp1 in the preulcerogenic stage of duodenal ulceration. These changes in levels of ET-1 and expression of transcription factors were also accompanied by increased expression of the CDK inhibitor p21. Thus, not only growth factors such as bFGF, PDGF and VEGF, but also transcription factors such as Egr-1 and Sp1 and the cell cycle regulator p21, may play a role in the natural history of experimental duodenal ulceration.

Ketamine and phenobarbital do not reduce the evoked-potential enhancement induced by electroconvulsive shock seizures in the rat

Electroconvulsive shock (ECS) seizures provide an animal analog of electroconvulsive therapy (ECT). Repeated ECS seizures cause a long-lasting, and perhaps permanent, enhancement of entorhinal-dentate evoked potentials (EPs) in the rat. Recently it has been reported that ketamine protects against ECS-induced EP enhancement. The present study was designed to replicate these findings and to extend them by incorporating a phenobarbital group (to control for ketamine's partial diminution of seizures) and an animal test of antidepressant activity (the Porsolt test). Unexpectedly, we found that neither ketamine nor phenobarbital protected against ECS-induced enhancement of EPs. Both, however, diminished the 'therapeutic' effects of ECS, as modeled by the Porsolt test. These data suggest that the use of ketamine would not eliminate the unwanted effects of ECT and that it might diminish ECT's therapeutic benefits.

Mossy fiber sprouting induced by repeated electroconvulsive shock seizures

The elicitation of repeated focal seizures (kindling) induces mossy fiber sprouting in the hippocampus of the rat. The present study investigated whether repeated generalized seizures also induce mossy fiber sprouting. Human psychiatric patients receive repeated generalized seizures during electroconvulsive therapy (ECT). Male Long-Evans rats received a course of eight electroconvulsive shock (ECS) seizures administered on a 48-h schedule over a course of 2 1/2 weeks. Control subjects received matched handling, but no stimulation. Fourteen days after the last ECS trial, all subjects were sacrificed and their brains subjected to Timm staining. Cell counts and area measures were also taken in the hilus. Significant sprouting, but not significant cell loss, was seen in the fascia dentata of the subjects that had received ECS.

Radiation-induced enterocolitis: basic and applied science

We adapted and introduced in our laboratory a simplified animal model of radiation-induced enterocolitis. After a shielding of the parenchymatous organs, our dose-response studies revealed that 20 Gy x-ray radiation resulted in about 20% mortality and reproducible lesions in the terminal ileum and proximal colon. These changes are optimal for pharmacologic studies since they may be decreased or aggravated by drugs. Sucralfate dose-dependently decreased the clinical signs of enterocolitis (e.g., lethargy, diarrhea) as well as the number and area of ileal and colonic erosions and ulcers. The wet weight of the ileum and colon were also decreased by sucralfate. bFGF at the small doses used exerted a beneficial effect only on a few of the parameters of enterocolitis. Thus sucralfate, and maybe bFGF, might decrease the severity and accelerate the healing of radiation-induced enterocolitis.

Amygdala-kindled and electroconvulsive seizures alter hippocampal expression of the m1 and m3 muscarinic cholinergic receptor genes

Expression of m1 and m3 muscarinic cholinergic receptors mRNAs was examined in rat hippocampus following either: (1) kindling to five Stage 5 amygdala-kindled seizures; or (2) eight electroconvulsive shock (ECS) seizures. Twenty-four hours after the last seizure of either type, there was a significant decrease in both m1 and m3 mRNAs in CA1, CA3 and the dentate gyrus subfields of the hippocampus. Twenty-eight days after the last seizure of either type, there was a significant increase in m1 mRNAs in CA1, CA3, and the dentate gyrus; for m3 mRNAs, there was a significant increase in CA3 28 days after the last ECS seizure, and in CA1 and CA3 28 days after the last kindled seizure. These results suggest that seizures alter the cholinergic system in the hippocampus, and that some of the alterations are very long-lasting.

Vascular approach to gastroduodenal ulceration: new studies with endothelins and VEGF

Endothelins (ET) and VEGF/VPF (vascular endothelial growth factor/vascular permeability factor) are products mainly of endothelial cells, which are also regulated via autocrine and paracrine pathways by these peptides. As a follow-up to our focus on vascular factors in ulcer pathogenesis and healing, we review here our recent studies with ET-1 and VEGF/VPF in animal models and human subjects. Our new results demonstrated a rapid and time-dependent release of ET-1 into the systemic circulation after intragastric administration of ethanol or HCI in rats, and ethanol in humans. The ET-1 release preceded the development of hemorrhagic erosions in both species and might be used as a diagnostic tool to noninvasively quantify acute gastric mucosal lesions. The development of solitary duodenal ulcers in the rat was preceded only by an organ- (involving only the duodenum and not the stomach) and molecule-specific (induced only by cysteamine and not by the nonulcerogenic analog ethanolamine) rapid local release of ET-1. The severity of cysteamine-induced duodenal ulcers was dose-dependently decreased by pretreatment with ET-1 antibodies or antagonist bosentan. A single intragastric dose of VEGF/VPF resulted in gastroprotection against ethanol, while daily intragastric treatment with the peptide for three weeks stimulated angiogenesis in the base of cysteamine-induced duodenal ulcers and accelerated ulcer healing. Thus, modulation of vascular factors seems to be sufficient for both acute gastroprotection and chronic duodenal ulcer healing.

Light-induced expression of fatty acid desaturase genes

In cyanobacterial cells, fatty acid desaturation is one of the crucial steps in the acclimation processes to low-temperature conditions. The expression of all the four acyl lipid desaturase genes of Synechocystis PCC 6803 was studied as a function of temperature and separately as a function of light. We used cells grown at 25 degreesC in light-activated heterotrophic growth conditions. In these cells, the production of alpha-linolenic acid and 18:4 fatty acids was negligible and the synthesis of gamma-linolenic acid was remarkably suppressed compared with those of the cells grown photoautotrophically. The cells grown in the light in the presence of glucose showed no difference in fatty acid composition compared with cells grown photoautotrophically. The level of desC mRNA for delta9 desaturase was not affected by either the temperature or the light. It was constitutively expressed at 25 degreesC with and without illumination. The level of desB transcripts was negligible in the dark-grown cells and was enhanced about 10-fold by exposure of the cells to light. The maximum level of expression occurred within 15 min. The level of desA and desD mRNAs was higher in dark-grown cells than that of desB mRNA for omega3 desaturase. However, the induction of both desA and desD mRNAs for delta12 and delta6 desaturases, respectively, was enhanced by light about 10-fold. Rifampicin, chloramphenicol, and 3-(3, 4-dichlorophenyl)-1,1-dimethylurea completely blocked the induction of the expression of desA, desB, and desD. Consequently, we suggest the regulatory role of light via photosynthetic processes in the induction of the expression of acyl lipid desaturases.

Genetic Enhancement of the Ability to Tolerate Photoinhibition by Introduction of Unsaturated Bonds into Membrane Glycerolipids

Strong light leads to damage to photosynthetic machinery, particularly at low temperatures, and the main site of the damage is the D1 protein of the photosystem II (PSII) complex. Here we describe that transformation of Synechococcus sp. PCC 7942 with the desA gene for a [delta]12 desaturase increased unsaturation of membrane lipids and enhanced tolerance to strong light. To our knowledge, this is the first report of the successful genetic enhancement of tolerance to strong light. Analysis of the light-induced inactivation and of the subsequent recovery of the activity of the PSII complex revealed that the recovery process was markedly accelerated by the genetic transformation. Labeling experiments with [35S]L-methionine also revealed that the synthesis of the D1 protein de novo at low temperature, which was a prerequisite for the restoration of the PSII complex, was much faster in the transformed cells than in the wild-type cells. These findings demonstrate that the ability of membrane lipids to desaturate fatty acids is important for the photosynthetic organisms to tolerate strong light, by accelerating the synthesis of the D1 protein de novo.

Long-term enhancement of entorhinal-dentate evoked potentials following 'modified' ECS in the rat

Electroconvulsive therapy (ECT) is widely used as a treatment for drug-resistant depression. The animal analogue of ECT is electroconvulsive shock (ECS) seizures. We have recently shown that repeated ECS seizures cause a long-lasting, perhaps permanent, enhancement in entorhinal-dentate evoked potentials in the rat. Our study, however, involved 'unmodified' ECS, whereas in clinical practice ECT is now usually given in its 'modified' form (with near-threshold currents, a short-acting barbiturate, muscle relaxant and oxygen). We have therefore repeated our experiments using modified ECS. Entorhinal-dentate evoked potentials were measured in Long-Evans rats before and after: (1) eight modified ECS seizures; or (2) eight sham modified ECS trials. Despite the use of the modified procedure, a significant and long-lasting enhancement in population spike amplitude was seen in the ECS group. We conclude that the modified procedure does not protect rats against the long-lasting enhancement of evoked potentials. Similar changes may be occurring in the brains of patients subjected to modified ECT.

The action in vivo of glycine betaine in enhancement of tolerance of Synechococcus sp. strain PCC 7942 to low temperature

The cyanobacterium Synechococcus sp. strain PCC 7942 was transformed with the codA gene for choline oxidase from Arthrobacter globiformis under the control of a constitutive promoter. This transformation allowed the cyanobacterial cells to accumulate glycine betaine at 60 to 80 mM in the cytoplasm. The transformed cells could grow at 20 degrees C, the temperature at which the growth of control cells was markedly suppressed. Photosynthesis of the transformed cells at 20 degrees C was more tolerant to light than that of the control cells. This was caused by the enhanced ability of the photosynthetic machinery in the transformed cells to recover from low-temperature photoinhibition. In darkness, photosynthesis of the transformed cells was more tolerant to low temperature such as 0 to 10 degrees C than that of the control cells. In parallel with the improvement in the ability of the transformed cells to tolerate low temperature, the lipid phase transition of plasma membranes from the liquid-crystalline state to the gel state shifted toward lower temperatures, although the level of unsaturation of the membrane lipids was unaffected by the transformation. These findings suggest that glycine betaine enhances the tolerance of photosynthesis to low temperature.

Targeted mutagenesis of acyl-lipid desaturases in Synechocystis: evidence for the important roles of polyunsaturated membrane lipids in growth, respiration and photosynthesis

Acyl-lipid desaturases introduce double bonds (unsaturated bonds) at specifically defined positions in fatty acids that are esterified to the glycerol backbone of membrane glycerolipids. The desA, desB and desD genes of Synechocystis sp. PCC 6803 encode acyl-lipid desaturases that introduce double bonds at the delta12, omega3 and delta6 positions of C18 fatty acids respectively. The mutation of each of these genes by insertion of an antibiotic resistance gene cartridge completely eliminated the corresponding desaturation reaction. This system allowed us to manipulate the number of unsaturated bonds in membrane glycerolipids in this organism in a step-wise manner. Comparisons of the variously mutated cells revealed that the replacement of all polyunsaturated fatty acids by a monounsaturated fatty acid suppressed growth of the cells at low temperature and, moreover, it decreased the tolerance of the cells to photoinhibition of photosynthesis at low temperature by suppressing recovery of the photosystem II protein complex from photoinhibitory damage. However, the replacement of tri- and tetraunsaturated fatty acids by a diunsaturated fatty acid did not have such effects. These findings indicate that polyunsaturated fatty acids are important in protecting the photosynthetic machinery from photoinhibition at low temperatures.

Immunocytochemical localization of acyl-lipid desaturases in cyanobacterial cells: evidence that both thylakoid membranes and cytoplasmic membranes are sites of lipid desaturation

There are four acyl-lipid desaturases in the cyanobacterium Synechocystis sp. PCC 6803. Each of these desaturases introduces a double bond at a specific position, such as the Delta6, Delta9, Delta12, or omicron3 position, in C18 fatty acids. The localization of the desaturases in cyanobacterial cells was examined immunocytochemically with antibodies raised against synthetic oligopeptides that corresponded to the carboxyl-terminal regions of the desaturases. All four desaturases appeared to be located in the regions of both the cytoplasmic and the thylakoid membranes. These findings suggest that fatty acid desaturation of membrane lipids takes place in the thylakoid membranes as well as in the cytoplasmic membranes.

Antisense RNA inhibition of the putative vacuolar H(+)-ATPase proteolipid of Dictyostelium reduces intracellular Ca2+ transport and cell viability

Transport of Ca2+ via a P-type pump into the contractile vacuole of Dictyostelium discoideum appears to be facilitated by vacuolar proton (V-H+) ATPase activity. To investigate the involvement of the V-H(+)-ATPase in this process using molecular techniques, we cloned a cDNA (vatP) encoding the putative proteolipid subunit of this enzyme. The deduced protein product of this cDNA is composed of 196 amino acids with a calculated M(r) of 20,148 and the primary structure exhibits high amino acid sequence identity with V-H(+)-ATPase proteolipids from other organisms. vatP is a single-copy gene and it produces one approximately 900 nt transcript at relatively constant levels during growth and development. Attempts to disrupt the endogenous gene using vatP cDNA were unsuccessful. But, expression of vatP antisense RNA reduced the levels of vatP message and V-H(+)-ATPase activity by 50% or more. These antisense strains grew and developed slowly, especially under acidic conditions, and the cells seemed to have difficulty forming acidic vesicles. During prolonged cultivation, all of the antisense strains either reverted to a wild-type phenotype or died. Thus in Dictyostelium, unlike yeast, the V-H(+)-ATPase seems to be indispensable for cell viability. When different antisense strains were analyzed for Ca2+ uptake by the contractile vacuole, they all accumulated less Ca2+ than control transformants. These results are consistent with earlier pharmacological studies which suggested that the V-H(+)-ATPase functions in intracellular Ca2+ transport in this organism.

Characterization of the Fad12 mutant of Synechocystis that is defective in delta 12 acyl-lipid desaturase activity

The Fad12 mutant of Synechocystis sp. PCC 6803 has a defect in the desA gene for delta 12 acyl-lipid desaturase. We identified a change in the nucleotide sequence of the structural gene for the desaturase, in which a leucine codon has been converted to a stop codon. Western blot analysis revealed that the delta 12 acyl-lipid desaturase was localized in both plasma membranes and thylakoid membranes of wild-type cells but was absent from both types of membrane in Fad12 cells. These findings suggest that the desaturation of fatty acids takes place in both types of membrane in Synechocystis sp. PCC 6803. The mutation in the delta 12 desaturase did not affect the lipid composition of thylakoid and plasma membranes, but it changed the fatty acid composition of lipids in similar ways in both types of membrane.

Unsaturation of the membrane lipids of chloroplasts stabilizes the photosynthetic machinery against low-temperature photoinhibition in transgenic tobacco plants

Using tobacco plants that had been transformed with the cDNA for glycerol-3-phosphate acyltransferase, we have demonstrated that chilling tolerance is affected by the levels of unsaturated membrane lipids. In the present study, we examined the effects of the transformation of tobacco plants with cDNA for glycerol-3-phosphate acyltransferase from squash on the unsaturation of fatty acids in thylakoid membrane lipids and the response of photosynthesis to various temperatures. Of the four major lipid classes isolated from the thylakoid membranes, phosphatidylglycerol showed the most conspicuous decrease in the level of unsaturation in the transformed plants. The isolated thylakoid membranes from wild-type and transgenic plants did not significantly differ from each other in terms of the sensitivity of photosystem II to high and low temperatures and also to photoinhibition. However, leaves of the transformed plants were more sensitive to photoinhibition than those of wild-type plants. Moreover, the recovery of photosynthesis from photoinhibition in leaves of wild-type plants was faster than that in leaves of the transgenic tobacco plants. These results suggest that unsaturation of fatty acids of phosphatidylglycerol in thylakoid membranes stabilizes the photosynthetic machinery against low-temperature photoinhibition by accelerating the recovery of the photosystem II protein complex.

Unsaturation of the membrane lipids of chloroplasts stabilizes the photosynthetic machinery against low-temperature photoinhibition in transgenic tobacco plants

Using tobacco plants that had been transformed with the cDNA for glycerol-3-phosphate acyltransferase, we have demonstrated that chilling tolerance is affected by the levels of unsaturated membrane lipids. In the present study, we examined the effects of the transformation of tobacco plants with cDNA for glycerol-3-phosphate acyltransferase from squash on the unsaturation of fatty acids in thylakoid membrane lipids and the response of photosynthesis to various temperatures. Of the four major lipid classes isolated from the thylakoid membranes, phosphatidylglycerol showed the most conspicuous decrease in the level of unsaturation in the transformed plants. The isolated thylakoid membranes from wild-type and transgenic plants did not significantly differ from each other in terms of the sensitivity of photosystem II to high and low temperatures and also to photoinhibition. However, leaves of the transformed plants were more sensitive to photoinhibition than those of wild-type plants. Moreover, the recovery of photosynthesis from photoinhibition in leaves of wild-type plants was faster than that in leaves of the transgenic tobacco plants. These results suggest that unsaturation of fatty acids of phosphatidylglycerol in thylakoid membranes stabilizes the photosynthetic machinery against low-temperature photoinhibition by accelerating the recovery of the photosystem II protein complex.

Structure and interactions of phycocyanobilin chromophores in phycocyanin and allophycocyanin from an analysis of their resonance raman spectra

Raman spectra of phycocyanobilin, phycocyanin, and allophycocyanin were obtained at resonance with their visible and near-UV transitions. These spectra were empirically assigned with the help of 14N- and 15N-isotopic substitutions and comparisons with resonance Raman spectra of phycoerythrin. These results confirm the previously suggested assignment of a conformation-sensitive band around 1239-1246 cm-1 to a mode involving nu CmH and nu CN coordinates. Computer-assisted decomposition of the complex, conformation-sensitive 1580-1670-cm-1 region yielded five components that we labeled I-V. The previously described spectral changes observed upon monomerization and denaturation in resonance Raman spectra of phycocyanin and allophycocyanin essentially arise from changes in the relative intensities of these components. Component I (around 1649-1651 cm-1) and component III (1621-1624 cm-1) originate predominantly from nu C=C at C15 of the chromophore. Their relative intensity ratio reflects the relative amounts of C15-Z-anti and C15-Z-syn methine bridge conformations, respectively. Component II (1633-1638 cm-1) is ascribed to a nu C=C mode of pyrrole rings; it is not sensitive to the chromophore conformation. Component IV is also conformation-insensitive and originates from nu C=N and nu C=C coordinates, most likely from ring C. Component V (1591-1594 cm-1) involves a nu C=N coordinate in ring D, coupled to a nu C=C coordinate of the C15 methine bridge. The implications of the present assignments on those of resonance Raman active modes of phytochrome are discussed. A consistent set of correlations between chromophore conformations and resonance Raman data is obtained for both phycobiliproteins and phytochrome.

The recovery of photosynthesis from low-temperature photoinhibition is accelerated by the unsaturation of membrane lipids: a mechanism of chilling tolerance

In a previous study of mutants in fatty-acid desaturation of Synechocystis PCC6803, it was demonstrated that the photoinhibition of photosynthesis at low temperature in vivo is tolerated by cells as a result of the unsaturation of glycerolipids of thylakoid membranes. Since the extent of photoinhibition of photosynthesis in vivo depends on a balance between the photoinduced inactivation and the recovery from the photoinhibited state, an examination was made of the effects of the unsaturation of membrane lipids on these processes. It appears that the unsaturation of the membrane lipids does not affect the inactivation process but accelerates the recovery process and, moreover, that the apparent increase in the photoinhibition in vivo of photosynthesis at low temperature is caused by a depressed rate of recovery at low temperature.

Contribution of membrane lipids to the ability of the photosynthetic machinery to tolerate temperature stress

The contribution of the unsaturation of membrane lipids to the ability of the photosynthetic machinery to tolerate temperature stress was studied in a transgenic cyanobacterium. Anacystis nidulans R2-SPc was transformed with the desA gene, which encodes the Delta12-desaturase that desaturates the fatty acids of membrane lipids in Synechocystis PCC6803. The transformant acquired the ability to introduce a second double bond into palmitoleic and oleic acids. The transformation enhanced the tolerance of the photosynthetic machinery to chilling stress but it had no detectable effect on the ability to tolerate heat stress. The transformation itself did not have any effect on photosynthetic activity. These results imply that an increase in the unsaturation of membrane lipids enhances the tolerance of the photosynthetic machinery toward chilling stress but not toward heat stress and that such an increase does not affect photosynthesis within the range of physiological temperatures.

The Unsaturation of Membrane Lipids Stabilizes Photosynthesis against Heat Stress

The effect of the unsaturation of glycerolipids of thylakoid membranes on the heat tolerance of the photosynthetic evolution of oxygen was studied in vivo by mutation and transformation of fatty-acid desaturases in the cyanobacterium Synechocystis PCC6803. The experimental results indicate that elimination of dienoic lipid molecules decreases, to a small but distinct extent, the heat tolerance of photosynthetic oxygen evolution, but that elimination of trienoic lipid molecules has no effect on the heat tolerance. This conclusion contrasts with the previous hypothesis that the heat tolerance of photosynthesis is enhanced upon an increase in the level of saturation of membrane lipids. It is also shown that light does not affect the nature of the effect of lipid unsaturation on the heat tolerance of photosynthesis.

Unsaturation of fatty acids in membrane lipids enhances tolerance of the cyanobacterium Synechocystis PCC6803 to low-temperature photoinhibition

Effect of the unsaturation of fatty acids in the glycerolipids of thylakoid membranes on low-temperature photoinhibition of photosynthesis was studied by mutation and transformation of the cyanobacterium Synechocystis PCC6803. When grown at 34 degrees C, the wild type contained mono-, di-, and triunsaturated lipids; a mutant, designated Fad6, contained mono- and diunsaturated lipids; and a transformant of Fad6, with a disrupted gene for desaturation and designated Fad6/desA::Kmr, contained only monounsaturated lipids. Fad6/desA::Kmr was the most susceptible among these strains to low-temperature photoinhibition of photosynthesis, whereas Fad6 and the wild type were apparently indistinguishable in terms of sensitivity to photoinhibition. This result suggests that the presence of diunsaturated fatty acids is important in protecting against low-temperature photoinhibition. The photoinhibition at room temperature, although much less significant than that at low temperature, was also affected by the unsaturation of fatty acids. By contrast, the photosynthetic transport of electrons, measured at various temperatures, was not affected by changes in extent of fatty acid unsaturation.

Enhancement of chilling tolerance of a cyanobacterium by genetic manipulation of fatty acid desaturation

The sensitivity (or tolerance) of plants to chilling determines their choice of natural habitat and also limits the worldwide production of crops. Although the molecular mechanism for chilling sensitivity has long been debated, no definitive conclusion has so far been reached about its nature. A probable hypothesis, however, is that chilling injury is initiated by phase transition of lipids of cellular membranes, as demonstrated for cyanobacteria, which serve as a model system for the plant cells. Because the phase transition temperature depends on the degree of unsaturation of fatty acids of the membrane lipids, it is predicted that the chilling tolerance of plants can be altered by genetically manipulating fatty-acid desaturation by introducing double bonds into fatty acids of membrane lipids. Here we report the cloning of a gene for the plant-type desaturation (termed desA). The introduction of this gene from a chilling-resistant cyanobacterium, Synechocystis PCC6803, into a chilling-sensitive cyanobacterium, Anacystis nidulans, increases the tolerance of the recipient to low temperature.

Evidence for Chloroplastic Succinate Dehydrogenase Participating in the Chloroplastic Respiratory and Photosynthetic Electron Transport Chains of Chlamydomonas reinhardtii

A method for isolating intact chloroplasts from Chlamydomonas reinhardtii F-60 was developed from the Klein, Chen, Gibbs, Platt-Aloia procedure ([1983] Plant Physiol 72: 481-487). Protoplasts, generated by treatment with autolysine, were lysed with a solution of digitonin and fractionated on Percoll step gradients. The chloroplasts were assessed to be 90% intact (ferricyanide assay) and free from cytoplasmic contamination (NADP isocitrate dehydrogenase activity) and to range from 2 to 5% in mitochondrial contamination (cytochrome c oxidase activity). About 25% of the cellular succinate dehydrogenase activity (21.6 micromoles per milligram chlorophyll per hour, as determined enzymically) was placed within the chloroplast. Chloroplastic succinate dehydrogenase had a K(m) for succinate of 0.55 millimolar and was associated with the thylakoidal material derived from the intact chloroplasts. This same thylakoidal material, with an enzymic assay of 21.6 micromoles per milligram chlorophyll per hour was able to initiate a light-dependent uptake of oxygen at a rate of 16.4 micromoles per milligram chlorophyll per hour when supplied with succinate and methyl viologen. Malonate was an apparent competitive inhibitor of this reaction. The succinate dehydrogenase activity present in the chloroplast was sufficient to account for the photoanaerobic rate of acetate dissimilation in H(2) adapted Chlamydomonas (M Gibbs, RP Gfeller, C Chen [1986] Plant Physiol 82: 160-166).

Chromophore conformational analysis in phycocyanin and in related chromopeptides by surface enhanced Raman spectroscopy

Chromopeptides got from phycocyanin by proteolytic digestion do not preserve the extended chromophore conformations characteristic to the native protein. Chromophore conformations in the chromopeptides showed heterogenity varying between completely folded and semi-extended states. Indications were found that the silver sol-phycocyanin interaction involves the UV electronic transition of the biliprotein which may explain why the visible excited surface enhanced Raman spectra were similar not to the visible excited but to the UV-excited resonance Raman spectrum of phycocyanin.

Lipid Saturation Induced Microviscosity Increase Has No Effect on the Reducibility of Flash-Oxidized Cytochrome f in Pea Thylakoids

Homogeneous catalytic hydrogenation was used to modify the level of fatty acid unsaturation of thylakoid membranes in the pea chloroplast. Fluidity alteration has been monitored simultaneously using the spin-label probe, 16-doxyl stearate. Even in the case of 30% hydrogenation, no change in the reduction rate of flash-oxidized cytochrome f was observed, in contrast to the fact that the same decrease in the double-bond content of the thylakoid membrane resulted in a pronounced inhibition in the full-chain electron transport. We conclude that the rate of lateral diffusion of reduced plastoquinone is unaffected by the lowering of the fluidity of the thylakoid lipid matrix.

Nitrate starvation induces homeoviscous regulation of lipids in the cell envelope of the blue-green alga, Anacystis nidulans

Replacement of the normal culture liquid to a nitrate-free medium resulted in an immediate drop in the ratio of protein to lipid in isolated cell envelopes of Anacystis nidulans cells. The relative fluidity of the envelope membranes or liposomes, made from the extracted lipids of the envelope, was estimated by measuring the steady-state fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. A thermotrophic phase transition of lipids within the cytoplasmic membrane of intact cells was also revealed by detecting the temperature-dependent absorption changes in the proportion of zeaxanthin at 390 nm. It became evident that a decrease in the proportion of protein to lipid within the cell envelope was accompanied neither by changes in the microviscosity level, nor by shifting of characteristic temperatures of the liquid-crystalline-to-gel transition of lipids. In parallel with nitrate starvation, however, the proportion of saturated fatty acids of the envelope lipids increased markedly. Accumulation of saturated, longer-chain (C18) fatty acids at the cost of C16 counterparts upon nitrate deprivation occurred in all of the complex lipids. In accordance with these findings, a pronounced decrease in the fluidity was demonstrated for the liposomes prepared from the envelope polar lipids of nitrate-starved cells compared with the corresponding control, throughout the temperature range (45-5 degrees C) studied. We propose that the fluidizing effect due to a fall in the ratio of protein to lipid was compensated by a rapidly triggering regulatory process which enables the preservation of the fluidity characteristics at an optimal level within the cell envelope of A. nidulans.

Primary Role of the Cytoplasmic Membrane in Thermal Acclimation Evidenced in Nitrate-Starved Cells of the Blue-Green Alga, Anacystis nidulans

The lipid phase transition of the cytoplasmic membrane and the chilling susceptibility were studied in nitrate-starved Anacystis nidulans cells. Nitrate starvation resulted in the disappearance of the thylakoid membrane system, without any effect on chilling susceptibility. The chilling susceptibility of the algal cells depended on the growth temperature. Temperatures of lipid phase transitions of the cytoplasmic membranes were detected by chilling-induced spectral changes in the carotenoid region, in vivo. These values were identical to those of cultures containing intact thylakoid systems. Our results suggest that cytoplasmic membrane plays a determinative role in the thermal acclimation of the alga cells.

Resonance Raman spectra of phycocyanin, allophycocyanin and phycobilisomes from blue-green alga Anacystis nidulans

Resonance Raman spectra of native C-phycocyanin, allophycocyanin and whole, intact phycobilisomes from the blue-green alga Anacystis nidulans (Synechococcus 6301) are reported. A tentative assignment for the more prominent resonance Raman bands is suggested. The possibly sensitive regions for inter-chromophore interactions in the case of phycobilisomes are also discussed.

Two simple procedures for isolation of allophycocyanin II from Anacystis nidulans

Allophycocyanin II purification using initial extraction of phycobiliproteins by acetone treatment is introduced. An additional fast method using Al2O3 is described. Both extraction procedures are followed up by conventional hydroxylapatite chromatography.