18] Inclusions: Carboxysomes

Summary1. Polyhedral bodies are present in several groups of autotrophic bacteria that assimilate inorganic carbon via the Calvin cycle, including members of the colourless sulphur‐ oxidizing bacteria, ammonia‐ and nitrite‐oxidizing bacteria and all cyanobacteria (blue‐green algae) examined. Other groups of Calvin‐cycle bacteria lack the inclusions, which have not been found in the purple photosynthetic bacteria, or in the hydrogen bacteria, with one exception in each case. Polyhedral bodies also occur in the chlorophyll b‐containing photosynthetic symbiotic prokaryote, Prochloron, and in several cyanelles. The inclusion bodies have not been found in prokaryotes that cannot fix carbon dioxide via the Calvin cycle, or in eukaryotes.2. Polyhedral bodies have been isolated from a colourless sulphur bacterium (Thiobacillus neapolitanus), two nitrifying bacteria (Nitrobacter agilis and Nitrosomonas sp.) and two cyanobacteria (Anabaena cylindrica and Chlorogloeopsis fritschii). Ribulose 1,5‐bisphosphate carboxylase/oxygenase (RuBisCO), the carbon dioxide‐fixing enzyme of the Calvin cycle, has been found in the polyhedral bodies in each case, confirming that these inclusions in autotrophic bacteria be re‐termed carboxysomes.3. Knowledge of carboxysome composition has been constrained by difficulties in carboxysome isolation, although effective methods, including cell disruption in low‐ionic‐strength buffers followed by density‐gradient centrifugation through silicon polymers, or sucrose, followed be preparative agarose electrophoresis, are now available.4. Analysis of isolated T. neapolitanus, N. agilis and C. fritschii carboxysomes by dissociating sodium dodecyl sulphate‐polyacrylamide gel electrophoresis has revealed the presence of 7–15 polypeptides, the most abundant being the large and small subunits of RuBisCO. Two polypeptides of the T. neapolitanus carboxysomes have been ascribed to the carboxysome membrane (shell), although the identity of other polypeptides is unknown.5. DNA of unknown function has been reported in carboxysomes isolated from two Nitrobacter species and may be present in the organelles from T. neapolitanus.6. RuBisCO occurs in both the carboxysomes and in soluble form in the cytoplasm of carboxysome‐containing bacteria. Structural, kinetic, regulatory and immunological comparisons have demonstrated full or near identity between the cytoplasmic and carboxysomal forms of the enzyme. As with RuBisCO from chloroplasts and from almost all non‐carboxysome‐containing bacteria, the cytoplasmic and carboxysomal RuBisCOs each consist of eight large plus eight small subunits. All RuBisCOs are bifunctional enzymes, oxygen acting as a competitive inhibitor of carboxylation, and carbon dioxide acting competitively to inhibit the apparently wasteful oxygenase reaction. Carbon dioxide and oxygen fixation occur at the same site on the large subunit. Despite extensive study, the function of the small subunits is unknown. All RuBisCOs can exist in an inactive and active form, activation proceeding by an ordered reversible binding of carbon dioxide, followed by a divalent metal cation, to the large subunit, at sites distinct from the catalytic site. Identity of the activation and catalytic sites at lysine residues 201 and 175, respectively, on the RuBisCO large subunit in organisms as phylogenetically diverse as spinach and Rhodospirillum rubrum suggests a uniform mechanism of RuBisCO regulation throughout the Calvin cycle autotrophs.7. Carboxysome function is unknown, although several possibilities exist. A role for the organelles in autotrophy has been assumed and studies on carboxysome function have centred on relations between the organelles and RuBisCO. Carboxysomes may serve as active sites of carbon dioxide fixation, act as CO2‐concentrating compartments for RuBisCO, protect RuBisCO from adverse effects such as inhibition by oxygen and degradation by proteases, and/or act as general protein‐storage bodies. Evidence and argument for and against each of these possibilities is presented from whole‐cell and enzyme studies with sulphur bacteria and cyanobacteria, including specialist and nutritionally versatile strains.8. The need for further knowledge of carboxysome composition, particularly including the structure and properties of the protein shell, to permit further understanding of carboxysome function is emphasized.

Vitamin B12 derivatives play several central roles in the metabolism of micro organisms (Friedrich 1988; Dolphin 1982; Golding and Rao 1987), which are also believed to possess the capacity unique in nature to build up the B,2 structure. Corrinoids related to vitamin B12 appear to have a particularly essential function in some methanogenic, acetogenic, sulphur- and sulphate-reducing bacteria, where they have been assigned a role in the fixation of carbon dioxide via the recently discovered acetyl coenzyme A pathway (Fuchs 1986; Wood et al.1986; Thauer 1988; Ragsdale et al. 1990).

Speciation, distribution and relationship of zinc and cadmium in summer coastal seawater of northern China

The bacterial symbionts of many marine invertebrates contain ribulose 1,5-bisphosphate (RuBP) carboxylase but apparently no carboxysomes, polyhedral bodies containing RuBP carboxylase. In the few cases where polyhedral bodies have been observed they have not been characterised enzymatically. Polyhedral bodies, 50–90 nm in diameter, were observed in thin cell sections of Thiobacillus thyasiris the putative symbiont of Thyasira flexuosa and RuBP carboxylase activity was detected in both soluble and particulate fractions after centrifugation of cell-free extracts. RuBP carboxylase purified 90-fold from the soluble fraction was of high molecular weight and consisted of large and small subunits, with molecular weights of 53,110 and 11,100 respectively. Particulate RuBP carboxylase activity was associated with polyhedral bodies 50–100 nm in diameter, as revealed by density gradient centrifugation and electron microscopy. Therefore, the polyhedral bodies were inferred to be carboxysomes. Native electrophoresis of isolated carboxysomes demonstrated a major band which comigrated with the purified RuBP carboxylase and three minor bands of lower molecular weight. Sodium dodecyl-sulphate (SDS) gel electrophoresis of SDS-dissociated carboxysomes demonstrated nine major polypeptides two of which were the large and small subunits of RuBP carboxylase. The RuBP carboxylase subunits represented 21% of the total carboxysomal protein. The most abundant polypeptide had a molecular weight of 40,500. Knowledge of carboxysome composition is necessary to provide an understanding of carboxysome function.

Polyhedral inclusion bodies were observed in cells of a Nitrosomonas species. They were present in growing cells as well as in resting cells. In thin sections their size was about 130 nm in growing cells and about 185 nm in diameter in resting cells. The bodies were commonly located in the nucleoplasm. They appeared to be bounded by a nonunit membrane and had a granular substructure. In thin sections about 70% of the exponentially grown cells and about 20% of the resting cells of the investigated strain showed 1-7 respectively 1-3 inclusion bodies.

Reversibility of the Phosphoroclastic Split of Pyruvate (Utter, M. F., Lipmann, F., and Werkman, C. H. (1945) J. Biol. Chem. 158, 521–531) Chester Hamlin Werkman (1893–1962) was born in Fort Wayne, Indiana. His career in science began at Iowa State University in 1920 when he became a graduate student under Robert E. Buchanan, an internationally recognized microbiologist. Werkman's interest in bacteria stemmed from the fact that he thought of them as simple models for studying the basic chemical transformations involved in living processes. He completed his dissertation in 1923 and remained with Buchanan until he was offered a faculty position at the University of Massachusetts in 1924. However, he returned to the Department of Bacteriology at Iowa State a year later and remained there as a faculty member for the rest of his life. Upon returning to Iowa State, Werkman's research interests underwent a slow evolution. Initially he continued to publish papers related to his thesis work on immunology and vitamins, but soon he developed an interest in food microbiology and the role of vitamins as growth factors for bacteria. During the early 1930s, the Iowa State agricultural experimental station started investigating the use of bacterial fermentation to dispose of farm waste, and Werkman became involved in this effort. This resulted in his publication of a series of papers describing organic techniques to isolate and quantify the products of various fermentation processes. Soon Werkman became interested in investigating the intermediate mechanisms of these fermentations and embarked on what would become a lifelong study of reaction intermediates in bacteria. One of Werkman's most important contributions to physiological microbiology was done with his graduate student, Harland G. Wood. Werkman and Wood established the existence of heterotrophic carbon dioxide fixation (the concept that all organisms, not just plants or specialized bacteria, can utilize CO2), which could be summarized by the “Wood Werkman reaction.” CO2+CH3COCOOH⇌COOHCH2COCOOH Werkman and Wood used 13C-labeled compounds to confirm heterotrophic carbon dioxide fixation and also to study the utilization of carbon in metabolism. To do this, they built a mass spectrometer and a 72-foot thermal diffusion column (to produce concentrated 13C) in the elevator shaft of the science building. They published their first detailed papers on the use of 13C-labeled compounds in the Journal of Biological Chemistry (JBC) (1Wood H.G. Werkman C.H. Hemingway A. Nier A.O. Heavy carbon as a tracer in heterotrophic carbon dioxide assimilation..J. Biol. Chem. 1941; 139: 365-376Abstract Full Text PDF Google Scholar, 2Wood H.G. Werkman C.H. Hemingway A. Nier A.O. The position of carbon dioxide carbon in succinic acid synthesized by heterotrophic bacteria..J. Biol. Chem. 1941; 139: 377-381Abstract Full Text PDF Google Scholar). These and other papers by Wood will be the subject of a future JBC Classic. In 1938, Merton Franklin Utter (1917–1980) joined Werkman's laboratory as a graduate student. Utter, who was born in Westboro, Missouri, had just graduated from Simpson College in Indianola, Iowa. The first paper he published with Werkman was entitled “The Preparation of an Active Juice from Bacteria” (3Wiggert W.P. Silverman M. Utter M.F. Werkman C.H. Preparation of an active juice from bacteria..Iowa State Coll. J. Sci. 1940; 14: 179-186Google Scholar). This was a very modest title considering that active enzyme systems had not yet been isolated from bacteria. Werkman and Utter used these bacterial extracts and 13C-labeled compounds to further investigate carbon dioxide fixation, which is the subject of the JBC Classic reprinted here. The Wood Werkman reaction had already established that carbon dioxide could be combined with aC3 compound, but the existence of a C1 + C2 reaction had not been demonstrated. Werkman and Utter knew that the phosphoroclastic split, in which pyruvic acid is split to make acetyl phosphate and formic acid, was common in Escherichia coli. CH3COCOOHPyruvic acid+H3PO4⇌CH3COOPO3H2acetyl phosphate+HCOOHformic acid If they could prove that this reaction was reversible, it would be an example of a C1 + C2 addition. Although the C1 compound in the reaction is formic acid rather than carbon dioxide, formic acid is in equilibrium with carbon dioxide and hydrogen in E. coli, so carbon dioxide fixation is ultimately involved in the reaction. Werkman and Utter teamed up with Fritz Lipmann (the author of a future JBC Classic), who had just discovered the role of acetyl phosphate in metabolism. To prove the reversibility of the reaction, they added 13C-labeled formic acid to E. coli extracts and tested for 13C in the resulting pyruvic acid. In separate experiments they added CH 133COOH and adenyl pyrophosphate (which would react to form labeled acetyl phosphate) to the extracts. In both cases the pyruvic acid formed contained 13C, demonstrating the reversibility of the phosphoroclastic split and the occurrence of C1 + C2 carbon dioxide fixation. As a final test they added 13CO2 to whole cell suspensions of E. coli and showed that the bacteria produced 13C-labeled pyruvic acid. After earning his Ph.D. with Werkman in 1942, Utter was appointed instructor in bacteriology at Ohio State. In 1944 he was offered an assistant professorship at the University of Minnesota and moved to Minneapolis. He moved again in 1946, this time to Cleveland, Ohio, to become an associate professor of biochemistry at Western Reserve University School of Medicine. Utter was promoted to professor in 1956 and became chairman of the biochemistry department in 1965. He remained as chairman until 1976 and then devoted all of his time to research and teaching in the Department of Biochemistry. Utter was also an associate editor for the JBC and helped to guide the journal's editorial policies during its rapid expansion. Utter continued to study metabolism and soon became interested in gluconeogenesis, which is where he made his most significant contribution to biochemistry. For many years it was believed that the synthesis of glucose (gluconeogenesis) occurred by the reversal of the Embden-Meyerhof pathway in glycolysis. Utter demonstrated that this was incorrect by discovering phosphoenolpyruvate carboxykinase and pyruvate carboxylase, two enzymes that are involved in the conversion of pyruvate to phosphoenolpyruvate in a sequence of reactions that differ from those in glycolysis. Utter, along with Bruce Keech, also provided one of the first examples of allosteric control of an enzyme when he demonstrated that acetyl-CoA regulates pyruvate carboxylase activity. 1All biographical information on Chester Hamlin Werkman was taken from Refs. 4Brown R.W. Biographical Memoir of Chester Hamlin Werkman. 44. National Academy of Sciences, Washington, D. C.1974: 328-358Google Scholar and 5Singleton R. From bacteriology to biochemistry: Albert Jan Kluyver and Chester Werkman at Iowa State..J. Hist. Biol. 2000; 33: 141-180Crossref PubMed Scopus (10) Google Scholar. 1All biographical information on Chester Hamlin Werkman was taken from Refs. 4Brown R.W. Biographical Memoir of Chester Hamlin Werkman. 44. National Academy of Sciences, Washington, D. C.1974: 328-358Google Scholar and 5Singleton R. From bacteriology to biochemistry: Albert Jan Kluyver and Chester Werkman at Iowa State..J. Hist. Biol. 2000; 33: 141-180Crossref PubMed Scopus (10) Google Scholar., 2All biographical information on Merton Franklin Utter was taken from Ref. 6Wood H.G. Hanson R.W. Biographical Memoir of Merton Franklin Utter. 56. National Academy of Sciences, Washington, D. C.1987: 474-499Google Scholar. 2All biographical information on Merton Franklin Utter was taken from Ref. 6Wood H.G. Hanson R.W. Biographical Memoir of Merton Franklin Utter. 56. National Academy of Sciences, Washington, D. C.1987: 474-499Google Scholar.

This book contains the proceedings of the 1991 Nobel Symposium devoted to the study of carbon dioxide (CO2) fixation and reduction in biological and model systems. With chapters authored by leading experts from around the world, the book covers subjects as diverse as photosynthetic carbon dioxide fixation and electrochemical reduction of CO2. Others topics include the organometallic chemistry of CO2 pertinent to catalysis, how enzymes deal with carbon dioxide and bicarbonate, photochemical electron transfer applied to the reduction of CO2, and the molecular biology and biochemistry of CO2, among many others. Students and researchers in biochemistry and the chemistry of CO2 fixation will welcome this timely survey of the field.

Single cell protein production of Euglena gracilis and carbon dioxide fixation in an innovative photo-bioreactor

Carbon dioxide fixation is the biological process through which carbon dioxide is converted to organic compounds. Organisms that fix carbon dioxide provide the organic carbon necessary to support the existence of all heterotrophic life on our planet. This article provides an introduction to the various mechanisms of carbon dioxide fixation utilised by microorganisms. The Calvin–Benson–Bassham cycle is shared among plants, algae and many photo‐ and chemoautotrophic bacteria, and is probably the most well known carbon dioxide‐fixation pathway. However, a number of other pathways exist that are unique to the microbial world and the diverse chemistry and strategies they utilise are fascinating. Among the six carbon‐fixing pathways known at present, three pathways harbouring novel enzymes have just been established in the past few years. With the number and diversity of microorganisms still expanding, the possibilities are high that further novel pathways will be identified in the near future.Key Concepts:Carbon dioxide fixation is the biological process through which carbon dioxide is converted to organic compounds.Organisms that fix carbon dioxide provide the organic carbon necessary to support the existence of all heterotrophic life on our planet.In addition to the Calvin–Benson–Bassham cycle, which is also found in plants and microorganisms harbour a number of unique carbon dioxide‐fixing pathways.

BackgroundNannochloropsis oceanica belongs to a large group of photoautotrophic eukaryotic organisms that play important roles in fixation and cycling of atmospheric CO2. Its capability of storing solar energy and carbon dioxide in the form of triacylglycerol (TAG) of up to 60% of total weight under nitrogen deprivation stress sparked interest in its use for biofuel production. Phenotypes varying in lipid accumulation among an N. oceanica population can be disclosed by single-cell analysis/sorting using fluorescence-activated cell sorting (FACS); yet the phenomenon of single cell heterogeneity in an algae population remains to be fully understood at the molecular level. In this study, combination of FACS and proteomics was used for identification, quantification and differentiation of these heterogeneities on the molecular level.ResultsFor N. oceanica cultivated under nitrogen deplete (−N) and replete (+N) conditions, two groups differing in lipid content were distinguished. These differentiations could be recognized on the population as well as the single-cell levels; proteomics uncovered alterations in carbon fixation and flux, photosynthetic machinery, lipid storage and turnover in the populations. Although heterogeneity patterns have been affected by nitrogen supply and cultivation conditions of the N. oceanica populations, differentiation itself seems to be very robust against these factors: cultivation under +N, −N, in shaker bottles, and in a photo-bioreactor all split into two subpopulations. Intriguingly, population heterogeneity resumed after subpopulations were separately recultivated for a second round, refuting the possible development of genetic heterogeneity in the course of sorting and cultivation.ConclusionsThis work illustrates for the first time the feasibility of combining FACS and (prote)-omics for mechanistic understanding of phenotypic heterogeneity in lipid-producing microalgae. Such combinatorial method can facilitate molecular breeding and design of bioprocesses.

Since carbon dioxide (CO2) is an abundant, economical, nontoxic and environmentally benign C1 chemical reagent, fixation of carbon dioxide in organic molecules has recently become an attractive project in organic synthesis. An electrochemical method has contributed greatly to this area because it enables an efficient fixation of carbon dioxide in organic molecules even under atmospheric pressure of carbon dioxide when a reactive metal, such as magnesium or aluminum metal, is used as a sacrificial anode. There have been a number of reports on electrochemical fixation of carbon dioxide, and we have also reported synthesis of useful carboxylic acids by electrochemical carboxylation of various organic compounds. On the other hands, it is well known that fluorine-containing organic compounds have unique chemical and physical properties. The introduction of fluorine atoms into biologically-active compounds is also known to cause remarkable modification of their original activities. Therefore, considerable attention has been paid to efficient and selective preparation methods of organofluorine compounds. However, little attention has been paid to electrochemical carboxylation to afford fluorinated carboxylic acids.1-4 During the course of our continuous studies on the synthesis of useful carboxylic acids by electrochemical fixation of carbon dioxide,5 we recently found that electrochemical reduction of polyfluoroarenes in the presence of carbon dioxide resulted in a regioselective cleavage of a C-F bond of the phenyl ring followed by reaction with carbon dioxide to give the corresponding mono-carboxylated products, polyfluorobenzoic acids, in moderate to good yields.6 We report herein the results for synthesis of polyfluorobenzoic acids by regioselective electrochemical carboxylation of polyfluoroarenes.First, we screened reaction conditions for electrochemical carboxylation of hexafluorobenzene (1a) as a substrate. When constant current electrolysis of 1a was carried out in DMF using a one-compartment cell equipped with a Pt cathode and an Mg anode with 3 F/mol of electricity in the presence of carbon dioxide, reductive cleavage of a C-F bond on the phenyl ring followed by reaction with carbon dioxide took place to give pentafluorobenzoic acid (2a). After reaction conditions screening, 2a could be obtained in 73% 19F NMR yield by electrolysis of 1a at –40°C with 5 mA/cm2 of current density. After recrystallization with hexane and acetone, pentafluorobenzoic acid (2a) was obtained in 65% isolated yield as a pure product.We next investigated similar electrochemical carboxylations of several polyfluoroarenes, and the results are shown in Scheme. When pentafluorobenzene (1b) was subjected to the present electrochemical carboxylation under the same conditions for the reaction of 1a, C-F bond cleavage followed by carboxylation also took place efficiently to give 2,3,5,6-tetrafluorobenzoic acid (2b) in 78% 19F NMR yield and 66% isolated yield after recrystallization. It is noteworthy that C-F bond cleavage followed by carboxylation of 1b occurred at the C3 position of 1b predominantly to give 2b as a major product. Similar regioselective electrochemical carboxylation was also achieved when pentafluoroarenes 1c-f were used as substrates. Under the same conditions except for 1d, electrochemical carboxylation of 1c-f gave 4-substituted-2,3,5,6-tetrafluorobenzoic acids 2c-f in 61-84% 19F NMR yields and 49-76% isolated yields after recrystallization. It is also to note that C-F bond cleavage occurred at the para position of the substituents of Me-, AcO-, Me(RO)2C-, and MeS- in pentafluoroethylarenes 1c-f predominantly in all cases to give 4-substituted-2,3,5,6-tetrafluorobenzoic acids 2c-f as major products.<Scheme>Other results of electrochemical carboxylation of polyfluoroarenes and proposed reaction mechanism including regioselectivity of the carboxylation will be presented.

Ribulose 1,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) activity was approximately equally distributed between supernatant and pellet fractions produced by differential centrifugation of disrupted cells of Chlorogloeopsis fritschii. Low ionic strength buffer favoured the recovery of particulate RuBP carboxylase. Density gradient centrifugation of resuspended cell-free particulate material produced a single band of RuBP carboxylase activity, which was associated with the polyhedral body fraction, rather than with the thylakoids or other observable particles. Isolated polyhedral body stability was improved by density gradient centrifugation through gradients of Percoll plus sucrose in buffer, which yielded apparently intact polyhedral bodies. These were 100 to 150 nm in diameter and contained ring-shaped, 12 nm diameter particles. It is inferred that the C. fritschii polyhedral bodies are carboxysomes. Sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis of SDS-dissociated polyhedral bodies revealed 8 major polypeptides. The most abundant, with molecular weights of 52,000 and 13,000, correspond with the large and small subunits, respectively, of RuBP carboxylase.

Mutant strains of the unicellular green alga Chlamydomonas reinhardi which -have impaired photosynthesis are characterized by their inability to fix carbon dioxide in the light at the wild-type rate.l The incapacity of these mutant strains to fix carbon dioxide by photosynthesis can be attributed to one of three possibilities: (1) the loss of a step in the photosynthetic electron transport chain; (2) the loss of the capacity to carry out photosynthetic phosphorylation; or (3) the loss of one of the steps in photosynthetic carbon dioxide fixation associated with the reductive pentose phosphate cycle. The mutant strains of C. reinhardi described to date2-4 fall into the first category mentioned above. In this paper we shall describe ac-20, a mutant strain which lacks the capacity for photosynthetic carbon dioxide fixation as a consequence of the loss of RuDP carboxylase activity. Organisms and the Methods.-The organisms used in the experiments described below were the wild-type strain of C. reinhardi, 137c, and the mutant strain ac-20, derived from wild type by ultraviolet irradiation followed by a screening test'; for carbon dioxide fixation. Cells, in the logarithmic phase of growth, were harvested from shake cultures grown at 25?C in high salt minimal medium' supplemented with 0.2% sodium acetate. Light (2500 lux) was provided by daylight fluorescent lamps. Carbon dioxide fixation by whole cells was measured as previously described.7 The light intensity was 60,000 lux. The water-soluble products of carbon dioxide fixation by whole cells in the light were also examined. A cell suspension in minimal medium (30 ml, 10 mg/ml wet weight) was placed in a lollipop and illuminated with 20,000 lux. Temperature was maintained at 25?C. The suspension was aerated, and after 10 min C14-labeled sodium bicarbonate (8 ,moles, 50 /c/imole) was introduced into the lollipop. Sixty sec later the reaction was terminated by emptying the contents of the lollipop into a hot methanol-chloroform mixture (12:5 v/v). The water-soluble products were then extracted according to the method of Bieleski and Young.' The products were separated on a Dowex-l chloride column (1 X 90 cm) using two stages of linear HC1 gradient elution. The gradient was as follows: tubes 1-35, water; tubes 36-155, a linear gradient from 0.028 N to 0.041 N HC1; tubes 156-265, a linear gradient from 0.070 N to 0.130 N HC1. Aliquots of 100 lambda from each tube were plated on planchets and counted. Twelve peaks were observed. Chloroplast fragments were prepared according to the method of Levine and Volkmann.K Crude extracts for enzyme assays were obtained from cells which had been washed once in 0.02 M Tris buffer, pH 7.5, and then resuspended in 5 ml of the same buffer. The cells were disrupted by sonic oscillation at 0?C for 21/2 min using a Mullard 20-kc ultrasonic disintegrator. The disrupted cell preparations were then centrifuged at 20,000 X g for 20 minl at 0?C. The green supernatant was used as the crude extract. The activity of the photosynthetic electron transport chain was measured by assaying the rate of TPN photoreduction by chloroplast fragments using the method described by Levine and Smillie.2

The radical polymerization of glycidyl methacrylate (GMA) was conducted under a carbon dioxide atmosphere (1 atm) in the presence of catalysts for the reaction of carbon dioxide and the oxirane group to afford the five‐membered cyclic carbonate group. The degrees of the carbon dioxide fixation depended on catalysts, concentration, and solvents. In solution reaction, the slower polymerizations resulted in faster carbon dioxide fixation, due to the faster carbon dioxide fixation to GMA than to oxirane moieties in polymers. When the polymerization was conducted in 1,4‐dioxane, which is a good solvent for polyGMA but a poor solvent for the analogous polymer bearing cyclic carbonate moieties, the resulting polymers were precipitated out as the progress of the polymerization and the carbon dioxide fixation. As a result, polymers could be isolated by simple filtration and rinsing with methanol. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3170–3176, 2009

The fine structure of striated microtubules and sleeve bodies in several species of Anabaena