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In the past two decades, mass loss from the Greenland ice sheet has accelerated, partly due to speedup of glaciers. However, uncertainty in speed derived from satellite products hampers detection of inland changes. In-situ measurements using stake surveys or GPS have lower uncertainties. To detect inland changes, we repeated in-situ measurements of ice-sheet surface velocities at historical locations first measured in 1959. Here, we show ice velocities have increased 5-15% across all deep inland sites. Several sites show a northward deflection of 3-4.5° in their flow azimuth. The recent appearance of a network of large transverse surface crevasses, bisecting historical overland traverse routes, may suggest a fundamental shift in local ice dynamics. We suggest that creep instability - a coincident warming and softening of near-bed ice layers - may explain recent acceleration and rotation, in the absence of a change in local driving stress. This mechanism, if included in simulations may improve projections of future ice loss.

Ten-year records of ice surface elevation changes derived from three GNSS stations placed on the interior of the Greenland ice sheet are used to assess the ability of CryoSat-2 radar altimetry to capture surface elevation changes during 2010-2021. We use GNSS interferometric reflectometry (GNSS-IR) to derive time series of continuous daily surface elevations. The footprint of GNSS-IR is about 1000 m2 and the accuracy is ±2cm, making it an excellent tool to validate ice surface height from satellite altimetry. We compare GNSS-IR derived ice surface elevations with CryoSat-2 derived surface elevations and find Cryosat-2 performs best at the GNSS site furthest north (GLS3) with a maximum difference of 12cm. The other GNSS sites have a higher residual range because of poorer data availability and local surface variations. The number of Cryosat-2 data points are roughly doubled from GLS1 and GLS2 to GLS3. GLS3 Is located in a very flat area of the ice sheet only moving 55m during 2011-2020. In contrast GLS1 moved 292m in the same period, clearly indicating a steeper slope to the ice sheet at this location, which we have difficulty correcting for because digital elevation models are associated with high uncertainty on the interior of the ice sheet. The strength of this assessment method lies in the continuous daily time series of surface elevation change derived from GNSS, as they clearly capture extreme short-term changes, which otherwise might have been perceived as errors in the radar altimetry measurements.

The Greenland Ice Sheet is the largest land ice contributor to sea level rise. This will continue in the future but at an uncertain rate and observational estimates are limited to the last few decades. Understanding the long-term glacier response to external forcing is key to improving projections. Here we use historical photographs to calculate ice loss from 1880–2012 for Jakobshavn, Helheim, and Kangerlussuaq glacier. We estimate ice loss corresponding to a sea level rise of 8.1 ± 1.1 millimetres from these three glaciers. Projections of mass loss for these glaciers, using the worst-case scenario, Representative Concentration Pathways 8.5, suggest a sea level contribution of 9.1–14.9 mm by 2100. RCP8.5 implies an additional global temperature increase of 3.7 °C by 2100, approximately four times larger than that which has taken place since 1880. We infer that projections forced by RCP8.5 underestimate glacier mass loss which could exceed this worst-case scenario., The Greenland Ice Sheet is the largest land ice contributor to sea level rise and understanding the long-term glacier response to external forcing is key to improved projections. Here the authors show Greenland’s three largest outlet glaciers will likely exceed current worst-case scenario

We use remotely sensed ice velocities in combination with observations of surface elevation and glacier area change to investigate the dynamics of Hagen Bræ, North Greenland in high detail over the last 35 years. From our data, we can establish for the first time that Hagen Bræ is a surge‐type glacier with characteristics of both Alaskan‐ and Svalbard‐type surging glaciers. We argue that the observed surge was preconditioned by the glacier geometry and triggered by englacially stored meltwater. At present, the glacier is in a transitional state between active and quiescence phases and is not building up to its pre‐surge geometry. We suggest that the glacier is adjusting to the loss of its floating section, general thinning, and changes in fjord conditions that occurred over the study period which are unrelated to the surge behavior. The high temporal resolution of the ice velocity data gives insight to the sub‐annual glacier flow., Key Points Thirty‐five years of remotely sensed data document the recent dynamics and surge cycle of Hagen Bræ in high detailWe argue that the surge was preconditioned by geometry but triggered by englacially stored meltwaterThe onset of the observed surge was abrupt while its termination was gradual

The Greenland ice sheet has been losing mass in response to increased surface melting (Khan et al. 2015; van den Broeke et al. 2017) as well as discharge of ice from marine terminating outlet glaciers (van den Broeke et al. 2009; Box et al. 2018). Marine terminating outlet glaciers flow to the ocean where they lose mass by e.g. iceberg calving. Currently, the mass loss from the Greenland ice sheet is the largest Arctic contributor to global sea-level rise (van den Broeke et al. 2009, 2017; Box et al. 2018). Therefore, monitoring changes in the Greenland ice sheet is essential to provide policy makers with reliable data. There is a consensus that most marine terminating outlet glaciers have retreated in recent decades, and that the increased calving rates are a response to recent atmospheric and oceanic warming (e.g. Box et al. 2018; Moon et al. 2018). The rate of dynamic mass loss is determined by changes of the glacier calving front (i.e. its terminus) position, ice thickness and changes in ice flow. Ocean temperature and fjord circulation also influence the calving front stability by melting the glacier below the water line, thinning the ice that is in contact with water (Moon et al. 2014). Change in calving front position is therefore an important indicator for monitoring the dynamic behaviour of the upstream area of the ice sheet, which is further modulated by local topographic features and buttressing effects (Rignot & Kanagaratnam 2006; Nick et al. 2009). The Programme for Monitoring of the Greenland Ice Sheet (PROMICE) is dedicated to monitoring changes in the mass budget of the Greenland ice sheet, including monitoring of the calving front lines of marine terminating outlet glaciers. Here, we present an updated collection of annual measurements of end-of-melt-season calving front lines for 47 marine terminating outlet glaciers in Greenland between 1999 and 2018. We also present an example application of the data set, in which we estimate area changes for this group of glaciers since 1999. The Greenland calving front lines were measured from optical satellite imagery obtained from Landsat, Aster, and Sentinel-2 (Table 1). The PROMICE calving front product is freely available for download as ESRI shapefiles.

This report contains information on five selected locations that may be utilized for industrial collection of drinking water, and provides the technical background for the second licensing round of the Greenland Government in its Strategy for Export of Ice and Water. This report is not aimed at addressing any technical or engineering questions posed by the locations or water treatment, but only concerns the natural environment and the quality of the water as it was sampled. A prerequisite in the investigation has been that the water should be at least partly derived from meltwater originating either from the Greenland Ice Sheet or from local glaciers and ice caps. The identification and selection process for locations was de-scribed in detail in Ahlstrøm et al. (2018) and updated in Kjeldsen et al. (2019). Locations are defined as outlets of a significant meltwater river to accessible fjords in the southwestern part of Greenland, to minimize potential sea ice and iceberg interference. Catchments for each location or river outlet were derived employing advanced hydrological methods, using the most recent elevation models available.The five selected locations represent different catchment sizes with varying amounts of discharge, ranging from roughly 290,000 million litres per year, down to slightly over 10,000 million litres per year. The rivers at all locations are, on average, discharging water from May to November with the vast majority of water discharging in the period June-September. A comparison between modelled discharge for the catchments for the two periods 1980-1991 and 2006-2017, showed an increase in the discharge at all sites except one, which was stable. A similar method was also used to examine the change in discharge over the last few decades, showing a promising overall melt increase of more than 50 % for the region.The five selected locations were visited by boat to sample the water and collect additional data. The field visits were conducted in June and September in either 2018 or 2019, to capture the seasonal variability in the water quality. Two locations drain ice sheet catch-ments and three locations drain catchments with local mountain glaciers and ice caps.An extensive analysis of chemical, physical and microbiological parameters was performed on the water samples. Some types of analyses had to be performed on-site, some were performed at GEUS laboratories, and some at certified commercial laboratories.All of the locations provide large amounts of meltwater during the summer from June-September, with river outlets being relatively near deep fjord waters. The meltwater con-tains varying amounts of sediment derived from glacier erosion of the bedrock, requiring filtration of the meltwater before use. For all five locations, inorganic parameters are below drinking water requirements and guidelines in filtered water samples. Gentle UV-treatment of the water is recommended, as is commonly required for surface water, as microbiological parameters generally exceed the guideline limits at all locations.While the water quality can be expected to vary over the season, the results provide a strong indication of the potential for export of drinking water from meltwater rivers in Greenland.

Meltwater from Greenland is an increasingly attractive resource of pure freshwater. To at-tract investments from the industry, an extensive effort has been launched to map possible extraction locations, determine the quality of the meltwater, and review the existing ice and water export legislation. This report presents results from mapping- and water quality anal-ysis of five selected locations, visited by boat in June 2017. Two locations drain ice sheet catchments and three locations drain catchments with local mountain glaciers.The mapping includes catchment delineation, ice- and land runoff modelling, ice-dynamic modelling of the age of the melting ice, collection of fjord depth data and an assessment of the risk from glacial lake outburst floods. An extensive analysis of chemical, physical and microbiological parameters were performed on the water samples collected during field-work. Some types of analysis had to be performed on-site, some were performed at GEUS laboratories, and some at certified commercial laboratories.Greenland has a diverse geology including areas with potential for mining of metals and radioactive isotopes. The existence of such areas could influence the water quality in melt-water rivers. The 2017 survey, however, showed excellent water quality at all locations with regards to inorganics like metal ions and radioisotopes. Toxic metals like arsenic, cadmium and nickel were well below the lowest criterion at all locations and so was fluoride, which may be an indicator for a number of toxic metals in Southern Greenland. Radioactivity was below the detection limit of the commercial laboratory at all locations. The seasonal varia-tion of metals and radioisotopes is not yet known, but so far the locations look promising with regards to these quality parameters.Biology is another factor that may influence water quality of meltwater rivers. Of most con-cern are cyanobacteria in lakes and rivers and bacteria from the gut of animals. Cyanobac-teria produce toxins like microcystins and Anatoxin-A. These compounds were not detected at any of the locations. Coliforms and enterococci were chosen as indicator bacteria. Coli-forms were not found at any location. Enterococcaceae were detected only at one location (2 per 5 mL). Total colony forming units (CFU) at 22 and 36°C were also analysed. While some CFU were found at 22°C (7-115 per mL) almost none were found at 36°C (0-2 per mL), which is a good safety indication. The bacterial parameters generally indicated good water quality, but some sort of simple disinfection should be considered, as is the case for all surface water for human consumption.In summary, the results indicate an excellent water quality at all five locations, with all pa-rameter values below the required drinking water standards for the European Union, the United States and The International Council of Bottled Water Associations (ICBWA) .

The warming climate is changing the surface dynamics of the Greenland Ice Sheet, including the balance between snowfall and melt. Increasing surface melt impacts the structure of the relatively porous near-surface layer known as firn. Camp Century, a base abandoned in 1967, now comprises a subsurface debris field within the firn in Northwest Greenland. We collected 80 km of 100 or 250 MHz radar data in nested grids over this subsurface debris field. Here, we present a comprehensive analysis and interpretation of this ice-penetrating radar survey. The vast majority (95%) of subsurface reflectors are located at depths of greater than 32 m. The tunnel network, as well as an overlying layer associated with historical surface activities, is readily visible in the radar data. This subsurface debris field is approximately circular with a radius of less than 1 km. Local downwarping of clear internal layers – likely annual accumulation layers - identifies now-collapsed liquid sumps. Analysis of radar signal polarity suggests that liquid hydrocarbons are likely present in one of these sumps. The radar data and a geo-referenced site map of Camp Century are freely accessible at www.campcenturyclimate.dk .

Stimulation of the non-specific defence enhances the disease resistance and growth, and has good potentials as a measure for increased microbial control in juvenile production of marine fish and shellfish. So far, the most commonly used immunostimulants are β-(1 → 3, 1 → 6)-glucans, and in this study the stimulatory potential of a β-(1 → 3, 1 → 6)-glucan of marine origin, the storage polysaccharide from the marine diatom Chaetoceros mülleri, was examined. The glucan (chrysolaminaran) was extracted from cultures of C. mülleri, and used as a dietary supplement in two first feeding experiments with larvae of Atlantic cod Gadus morhua L. In one experiment the microalgal glucan was compared to the commercial yeast-glucan product MacroGard®, and in the other to an alginate with a high content of mannuronic acid (High-M alginate) isolated from Durvillaea antarctica. The stimulants were given via rotifers, and weaning to formulated feed was initiated at day 17 or 18 after hatching. The survival ± SEM at day 27 after hatching was 24.5 ± 2.0%, 14.8 ± 4.5% and 13.1 ± 1.4% for the groups fed C. mülleri-glucan, yeast glucan and for the control, respectively, in the first experiment. The group fed C. mülleri-glucan group had higher survival compared to the control (P < 0.05) group, whereas the yeast glucan had no positive effect on the survival (p > 0.05). The dry weights of the groups at day 27 were low, with 203.2 ± 52.2, 165.2 ± 43.4 and 198.5 ± 58.1 μg per larva for the C. mülleri-glucan, yeast glucan and control groups, respectively. In the second experiment the survival in the period of feeding formulated feed (days 18-30) were 44.6 ± 4.3%, 44.7 ± 1.3%, and 33.8 ± 4.1% survival for the C. mülleri-glucan, High-M alginate and control group, respectively. The cod larvae fed C. mülleri-glucan reached an average weight of 531.6 ± 17.2 μg at day 30, which was significantly higher (p < 0.05) than the control group that had an average of 473.6 ± 3.5 μg. The larvae fed High-M alginate had an average weight of 470.3 ± 31.6 μg per larva at day 30, and not significantly different from the control (p > 0.05). The early weaning to formulated diet had detrimental effect on the growth of the larvae. In both experiments the C. mülleri-glucan group was the only group showing a positive growth rate in the period of weaning to dry feed. The microbial conditions in larval gut and water were monitored with respect to total colony forming units on Marine agar, and Vibrio- and Pseudomonas-like species on selective agars (TCBS and marine Pseudomonas Agar with CFC-supplement). The larvae were rapidly colonised after hatching, but no or weak effects of the stimulants were observed on the colonisation rates or the composition. The total CFU varied from 10 1 to 10 2 CFU per μg larva after initiation of the first feeding. The percentages of Pseudomonas-like bacteria increased throughout the period, whereas the levels of Vibrio-like bacteria were low and stable. The chrysolaminaran from the diatom C. mülleri was shown to be a promising candidate for use as an immunostimulatory feed additive, and which should be further explored. © 2006 Elsevier B.V. All rights reserved.

The vertebrate 2-5A system is part of the innate immune response and central to cellular antiviral activities. Upon activation by viral double-stranded RNA, 5′-triphosphorylated, 2′-5′-linked oligoadenylate polyribonucleotides (2-5As) are synthesized by one of several 2′-5′ oligoadenylate synthetases. The 2-5As bind and activate RNase L, an unspecific endoribonuclease, resulting in viral and cellular RNA decay. Given that most endogenous RNAs are degraded by RNase L, continued enzyme activity will eventually lead to cell growth arrest and cell death. This is averted, when 2-5As and their 5′-dephosphorylated forms, the so-called 2-5A core molecules, are cleaved and thus inactivated by 2′-5′-specific nuclease(s), e.g. phosphodiesterase 12, thereby turning RNase L into its latent form. In this study, we have characterized the human phosphodiesterase 12 in vitro focusing on its ability to degrade 2-5As and 2-5A core molecules. We have found that the enzyme activity is distributive and is influenced by temperature, pH and divalent cations. This allowed us to determine Vmax and Km kinetic parameters for the enzyme. We have also identified a novel 2′-5′-oligoadenylate nuclease; the human plasma membrane-bound ectonucleotide pyrophosphatase/phosphodiesterase 1, suggesting that 2-5A catabolism may be a multienzyme-regulated process.

Background The 5′-triphosphorylated, 2′-5′-linked oligoadenylate polyribonucleotides (2-5As) are central to the interferon-induced antiviral 2-5A system. The 2-5As bind and activate the RNase L, an endoRNase degrading viral and cellular RNA leading to inhibition of viral replication. The 2-5A system is tightly controlled by synthesis and degradation of 2-5As. Whereas synthesis is mediated by the 2′-5′ oligoadenylate synthetase family of enzymes, degradation seems to be orchestrated by multiple enzyme nucleases including phosphodiesterase 12, the ectonucleotide pyrophosphatase/phosphodiesterase 1 and the A-kinase anchoring protein 7. Results Here we present assay tools for identification and characterization of the enzymes regulating cellular 2-5A levels. A procedure is described for the production of 2′-5′ oligoadenylates, which are then used as substrates for development and demonstration of enzyme assays measuring synthetase and nuclease activities, respectively. The synthetase assays produce only a single reaction product allowing for very precise kinetic assessment of the enzymes. We present an assay using dATP and the A(pA)3 tetramer core as substrates, which requires prior isolation of A(pA)3. A synthetase assay using either of the dNTPs individually together with NAD+ as substrates is also presented. The nuclease reactions make use of the isolated 2′-5′ oligoadenylates in producing a mixture of shorter reaction products, which are resolved by ion-exchange chromatography to determine the enzyme activities. A purified human 2′-5′ oligoadenylate synthetase and a purified human phosphodiesterase 12 along with crude extracts expressing those proteins, are used to demonstrate the assays. Conclusions This paper comprises an assay toolbox for identification and characterization of the synthetases and nucleases regulating cellular 2-5A levels. Assays are presented for both enzyme families. The assays can also be used to address a broader cellular role of the OAS enzymes, based on the multiple substrate specificity intrinsic to these proteins. Electronic supplementary material The online version of this article (doi:10.1186/s12858-015-0043-8) contains supplementary material, which is available to authorized users.

The signal transducer and activator of transcription 3 (STAT3) is a well-described pro-oncogene found constitutively activated in several cancer types. Folates are B vitamins that, when taken up by cells through the Reduced Folate Carrier (RFC), are essential for normal cell growth and replication. Many cancer cells overexpress a glycophosphatidylinositol (GPI)-anchored Folate Receptor α (FRα). The function of FRα in cancer cells is still poorly described, and it has been suggested that transport of folate is not its primary function in these cells. We show here that folic acid and folinic acid can activate STAT3 through FRα in a Janus Kinase (JAK)-dependent manner, and we demonstrate that gp130 functions as a transducing receptor for this signalling. Moreover, folic acid can promote dose dependent cell proliferation in FRα-positive HeLa cells, but not in FRα-negative HEK293 cells. After folic acid treatment of HeLa cells, up-regulation of the STAT3 responsive genes Cyclin A2 and Vascular Endothelial Growth Factor (VEGF) were verified by qRT-PCR. The identification of this FRα-STAT3 signal transduction pathway activated by folic and folinic acid contributes to the understanding of the involvement of folic acid in preventing neural tube defects as well as in tumour growth. Previously, the role of folates in these diseases has been attributed to their roles as one-carbon unit donors following endocytosis into the cell. Our finding that folic acid can activate STAT3 via FRα adds complexity to the established roles of B9 vitamins in cancer and neural tube defects.

BACKGROUND: The expression of 2'-5'-Oligoadenylate synthetases (OASs) is induced by type 1 Interferons (IFNs) in response to viral infection. The OAS proteins have a unique ability to produce 2'-5' Oligoadenylates, which bind and activate the ribonuclease RNase L. The RNase L degrades cellular RNAs which in turn inhibits protein translation and induces apoptosis. Several single nucleotide polymorphisms (SNPs) in the OAS1 gene have been associated with disease. We have investigated the functional effect of two common SNPs in the OAS1 gene. The SNP rs10774671 affects splicing to one of the exons in the OAS1 gene giving rise to differential expression of the OAS1 isoforms, and the SNP rs1131454 (former rs3741981) resides in exon 3 giving rise to OAS1 isoforms with either a Glycine or a Serine at position 162 in the core OAS unit.RESULTS: We have used three human cell lines with different genotypes in the OAS1 SNP rs10774671, HeLa cells with the AA genotype, HT1080 cells with AG, and Daudi cells with GG. The main OAS1 isoform expressed in Daudi and HT1080 cells was p46, and the main OAS1 isoform expressed in HeLa cells was p42. In addition, low levels of the OAS1 p52 mRNA was detected in HeLa cells and p48 mRNA in Daudi cells, and trace amounts of p44a mRNA were detected in the three cell lines treated with type 1 interferon. We show that the OAS1 p46 isoform was localized in the mitochondria in Daudi cells, whereas the OAS1 isoforms in HeLa cells were primarily localized in cytoplasmic vacuoles/lysosomes. By using recombinantly expressed OAS1 mutant proteins, we found that the OAS1 SNP rs1131454 (former rs3741981) did not affect the enzymatic OAS1 activity.CONCLUSIONS: The SNP rs10774671 determines differential expression of the OAS1 isoforms. In Daudi and HT1080 cells the p46 isoform is the most abundantly expressed isoform associated with the G allele, whereas in HeLa cells the most abundantly expressed isoform is p42 associated with the A allele. The SNP rs1131454 (former rs3741981) does not interfere with OAS1 enzyme activity. The OAS1 p46 isoform localizes to the mitochondria, therefore a full 2-5A system can now be found in the mitochondria.

The vertebrate 2-5A system is part of the innate immune system and central to cellular antiviral defense. Upon activation by viral double-stranded RNA, 5′-triphosphorylated, 2′–5′-linked oligoadenylate polyribonucleotides (2-5As) are synthesized by one of several 2′–5′-oligoadenylate synthetases. These unusual oligonucleotides activate RNase L, an unspecific endoribonuclease that mediates viral and cellular RNA breakdown. Subsequently, the 2-5As are removed by a 2′-phosphodiesterase (2′-PDE), an enzyme that apart from breaking 2′–5′ bonds also degrades regular, 3′–5′-linked oligoadenylates. Interestingly, 2′-PDE shares both functionally and structurally characteristics with the CCR4-type exonuclease–endonuclease–phosphatase family of deadenylases. Here we show that 2′-PDE locates to the mitochondrial matrix of human cells, and comprise an active 3′–5′ exoribonuclease exhibiting a preference for oligo-adenosine RNA like canonical cytoplasmic deadenylases. Furthermore, we document a marked negative association between 2′-PDE and mitochondrial mRNA levels following siRNA-directed knockdown and plasmid-mediated overexpression, respectively. The results indicate that 2′-PDE, apart from playing a role in the cellular immune system, may also function in mitochondrial RNA turnover. The vertebrate 2-5A system is part of the innate immune system and central to cellular antiviral defense. Upon activation by viral double-stranded RNA, 5′-triphosphorylated, 2′–5′-linked oligoadenylate polyribonucleotides (2-5As) are synthesized by one of several 2′–5′-oligoadenylate synthetases. These unusual oligonucleotides activate RNase L, an unspecific endoribonuclease that mediates viral and cellular RNA breakdown. Subsequently, the 2-5As are removed by a 2′-phosphodiesterase (2′-PDE), an enzyme that apart from breaking 2′–5′ bonds also degrades regular, 3′–5′-linked oligoadenylates. Interestingly, 2′-PDE shares both functionally and structurally characteristics with the CCR4-type exonuclease–endonuclease–phosphatase family of deadenylases. Here we show that 2′-PDE locates to the mitochondrial matrix of human cells, and comprise an active 3′–5′ exoribonuclease exhibiting a preference for oligo-adenosine RNA like canonical cytoplasmic deadenylases. Furthermore, we document a marked negative association between 2′-PDE and mitochondrial mRNA levels following siRNA-directed knockdown and plasmid-mediated overexpression, respectively. The results indicate that 2′-PDE, apart from playing a role in the cellular immune system, may also function in mitochondrial RNA turnover.

To examine the associations of job acquisition and loss in a representative, prospective community sample of people with schizophrenia living in the UK, France and Germany.A representative sample of twelve hundred and eight people with schizophrenia were recruited from selected secondary mental health services in the U.K, France and Germany and followed up for 2 years. Information on demographic details, psychotic symptoms and work status was collected.The odds of getting jobs were increased by being resident in Marseille, Leipzig, Hemer and Heilbronn and by a higher regional general population employment rate. The odds were reduced by living in Lyon, a later illness onset, a longer length of illness, a continuous illness course and more severe negative psychotic symptoms. Previous vocational training reduced the odds of losing employment, whilst living in Lyon or Leipzig, harmful use of alcohol and more positive psychotic symptoms at baseline all increased the odds.In addition to illness related factors, area of residence and local labour market conditions appear to be important in explaining employment status change in people with schizophrenia.

13 páginas, 5 figuras, 3 tablas., The 2 0 -5 0 -oligoadenylate synthetase (OAS) belongs to a nucleotidyl transferase family that includes poly(A) polymerases and CCA-adding enzymes. In mammals and birds, the OAS functions in the interferon system but it is also present in an active form in sponges, which are devoid of the interferon system. In view of these observations, we have pursued the idea that OAS genes could be present in other metazoans and in unicellular organisms as well. We have identified a number of OAS1 genes in annelids, mollusks, a cnidarian, chordates, and unicellular eukaryotes and also found a family of proteins in bacteria that contains the five OAS-specific motifs. This indicates a specific relationship to OAS. The wide distribution of the OAS genes has made it possible to suggest how the OAS1 gene could have evolved from a common ancestor to choanoflagellates and metazoans. Furthermore, we suggest that the OASL may have evolved from an ancestor of cartilaginous fishes, and that the OAS2 and the OAS3 genes evolved from a mammalian ancestor. OAS proteins function in the interferon system in mammals. This system is only found in jawed vertebrates. We therefore suggest that the original function of OAS may differ from its function in the interferon system, and that this original function of OAS is preserved even in OAS genes that code for proteins, which do not have 2 0 -5 0 -oligoadenylate synthetase activity., The work was initially supported by a grant from the Danish Natural Science Council and the Carlsberg Foundation. The work was supported by the Estonian Science Foundation (Grant no. 7421).

We have investigated the content and structure of the chrysolaminarans isolated from the two marine diatoms Chaetoceros mulleri and Thalassiosira weissflogii. Samples were taken from different phases of growth, and the structure of the chrysolaminaran was seen in relation to the specific growth rate of the diatoms. The structure determined for the glucan from C. mulleri was found not to vary with different specific growth rates. T. weissflogii showed some variance in the structure, both throughout the different stages of growth and between samples taken from the stationary phase. C. mulleri was found to have a chrysolaminaran with a degree of polymerization (DP) of 22-24 and a degree of beta-(1-->6) branching of 0.006-0.009. These results corresponded well with previous results obtained in our laboratories. The chrysolaminaran isolated from T. weissflogii was found to have a DP of 5-13 and no beta-(1-->6) branching. This is to our knowledge the first characterization of the chrysolaminaran from T. weissflogii.

High-resolution magic-angle spinning (hr-MAS) NMR spectroscopy was used to record NMR spectra of a cell paste from the marine diatom Chaetoceros mulleri. This gave information on a cellular storage polysaccharide identified as a beta-D-(1-->3)-linked glucan, using hr-MAS one-dimensional 1H and 13C, two-dimensional 1H,1H-COSY and 13C,1H-correlation spectroscopy. The same structural information was deduced from the liquid state NMR data on the glucan extracted from C. mulleri. The extracted glucan proved to be a beta-D-(1-->3)-linked glucan with a degree of polymerization of 19 and a degree of beta-D-(1-->6) branching of 0.005. The hr-MAS spectrum of the diatom showed several nonglucan resonances in the carbohydrate region of the NMR spectrum (60-103 ppm) that were shown to be noncarbohydrate resonances by means of two-dimensional 13C,1H- and 1H,1H-correlated NMR data.