Isolation and identification of sialylcompounds from hemofiltrate

Summary Hemofiltrate of patients with end stage renal disease is a source of sialyl compounds of unusual composition which accumulate in uremia. The large volumes involved (20–30l), are concentrated and desalted by modified reverse osmosis using membranes with a nominal cut-off of 500 D. The transport of the individual solutes during this process is monitored by reversed-phase HPLC of the permeates and retentates, respectively. By a combination of size-exclusion and ion-exchange chromatography 11 sialyl compounds are isolated preparatively. All structures have been determined using one and two dimensional NMR spectroscopy, enzymatic degradation and FAB mass spectrometry.Supported by the Deutsche Forschungsgemeinschaft     

Algal biotechnology

The review gives a general outline of macro and microalgal biotechnology. The main methods by which algae are cultivated and harvested are described. The first section deals with the environmental factors affecting mass culture and the principles governing the design and operation of mass cultivation systems. The second section gives the main current and potential uses of algae: in wastewater treatment, a source of food and feed, an energy source, and in the production of common and fine chemicals, such as polysaccharides, lipids, glycerol, pigments, and enzymes. Pharmaceutical uses of algae are described, and their potential as a source of novel biologically-active compounds is discussed. Future developments and the great potential of algae are considered.     

The furan approach to oxacycles. Part 3: Stereoselective synthesis of 2,3-disubstituted tetrahydropyrans

Commercially available furan 1 was converted to 2,3-trans and 2,3-cis-disubstituted tetrahydropyrans 2 and 3 using a highly efficient route to oxacycles, based on the oxidation of the furan ring with singlet oxygen. Tetrahydropyrans 2 and 3 could be easily separated by column chromatography.     

Modeling equilibrium and kinetics of metal uptake by algal biomass in continuous stirred and packed bed adsorbers

Physical and chemical characterization of algae Gelidium particles shows a gel structure, with two major binding groups, carboxylic and hydroxyl groups, with an affinity constant distribution for protons, well described by a Quasi-Gaussian distribution suggested by Sips. A continuous model, considering a heterogeneous distribution of the carboxylic groups, determined by potentiometric titration experiments, was able to predict equilibrium data at different pH. The metal uptake capacity decreases with the solution pH, suggesting that competition exists between hydrogen ions, present in high concentrations for low pH values, and metal ions. For high ionic strengths, adsorption sites will be surrounded by counter ions and partially lose their charge, which weakens the contribution of the electrostatic binding and decreases the overall adsorption. A small influence of the temperature in the adsorption process was observed. Batch kinetic experiments were also performed, at different pH values, and results were well fitted by a mass transfer model, considering the intraparticle diffusion resistance given by the linear driving force model (LDF). Continuous stirred adsorber (CSTA) and packed bed column configurations were also tested for metal adsorption. The biosorbent regeneration was achieved by contacting it with strong acid (0.1 M HNO₃). A mass transfer model was applied with success to describe the biosorption/desorption process in CSTA and packed bed column, considering the equilibrium given by the Langmuir equation/mass action law and film and intraparticle diffusion resistances.     

Isolation and characterization of a photosystem I-associated antenna (LHC I) and a photosystem I—core complex from the chlorophyll c-containing alga Pleurochloris meiringensis (Xanthophyceae)

A photosystem (PS) I holocomplex was isolated from Pleurochloris meiringensis Vischer (Xanthophyceae) using sucrose density centrifugation. This complex exhibited a fluorescence emission maximum at 715 nm, which is in accordance with the long wavelength emission of whole cells. The complex was further dissociated into a core complex and a light-harvesting protein (LHC I). The core protein contains mainly Chl a and β-carotene, is 8.25 times enriched in P700 and has its main emission maximum at 715 nm. Therefore, the longest wavelength emission of P. meiringensis is due to the PS I core, which is in contrast to higher plants. The LHC I differs from LHC II with regard to its polypeptide pattern as well as its spectral properties. The arrangement of antennae is discussed in relation to the regulation of energy transfer between the photosystems.     

Biosensors to detect marine toxins: Assessing seafood safety

This article describes the different types of marine toxins and their toxic effects, and reviews the bio/analytical techniques for their detection, putting special emphasis to biosensors. Important health concerns have recently appeared around shellfish (diarrheic, paralytic, amnesic, neurologic and azaspiracid) and fish (ciguatera and puffer) poisonings produced by different types of phycotoxins, making evident the urgent necessity of counting on appropriate detection technologies. With this purpose, several analysis methods (bioassays, chromatographic techniques, immunoassays and enzyme inhibition-based assays) have been developed. However, easy-to-use, fast and low-cost devices, able to deal with complicated matrices, are still required. Biosensors offer themselves as promising biotools, alternative and/or complementary to conventional analysis techniques, for fast, simple, cheap and reliable toxicity screening. Nevertheless, despite the wide range of seafood toxins and the already rooted biosensing systems, the literature on biosensors for phycotoxins is scarce. This article discusses the existing biosensor-based strategies and their advantages and limitations. Finally, the article gives a general overlook about the regulation toxin levels and monitoring programmes currently established around the world concerning seafood safety.     

Identification of dimethylarsinoyl-riboside derivatives in seaweed by pneumatically assisted electrospray tandem mass spectrometry

Pneumatically-assisted electrospray tandem mass spectrometry (ES MS/MS) was proposed as a technique for the identification of dimethylarsinoyl-riboside derivatives (arsenosugars) in seaweed (Laminaria). Conditions for the acquisition of MS and MS/MS spectra were optimized. A size-exclusion HPLC (SE HPLC) step was developed for the purification of algal extracts prior to ES MS. The arsenosugar fraction was found to elute prior to the majority of other arsenic compounds. The identity of the compounds expected to be arsenosugar compounds was confirmed by the collision induced dissociation (CID) of the relevant protonated molecule ions. An independent confirmation of the identity of analytes was obtained by two-dimensional (size-exclusion–anion exchange) HPLC–ICP MS with signal identification by spiking with the appropriate arsenosugar standards.     

The effects of organolead compounds on a freshwater and a marine alga

There are conflicting reports concerning the toxicity of tetraalkyllead (TAL) compounds to algae. A number of groups have found the TAL's to be comparable in toxicity with the trialkyllead compounds (R₃Pb⁺), whereas in a recent report it is suggested that the TAL's themselves are completely non-toxic and any apparent toxicity is due to R₃Pb⁺ breakdown products. With the object of identifying the toxic agent, the effect of Et₄Pb (TEL) on two algal species was re-examined. Analyses were carried out during the course of the incubations to establish the nature and concentrations of organoleads present in both media and algae, and hence evaluate their relative contributions to total toxicity. Algae were also cultured in the presence of Me₄Pb (TML), Me₃PbCl, Et₃PbCl, Bu₃PbCl and Et₂PbCl₂ to assess relationships between alkyl chain length and degree of substitution around the lead on algal activity. Additions of selenide and sulphide were made to the Et₃Pb⁺ and Et₂Pb²⁺ systems to see if these environmentally abundant species reduced or enhanced organolead toxicity. Problems were encountered in the analysis of the heterogeneous TEL containing media. Regardless of the analytical problems, the results confirm the previous findings that TAL's are non-toxic to algae and it is the R₃Pb⁺ breakdown products which are responsible for the apparent toxicity of the TAL's. The trialkylleads were the most toxic of the several alkyllead species studied, and within the trialkyl series toxicity increased with alkyl chain length. Neither selenide or sulphide had any significant ameliorative effect on alkyllead toxicity. It was found that the ionic organoleads were complexed on the TAL's and this complexing led to a number of unexpected results.     

Growth of the green algae Chlamydomonas reinhardtii under red and blue lasers

Red and blue lasers, holding promise as an electric light source for photosynthetic systems on account of being true monochromatic, high-power, and having high electrical-conversion efficiency, were employed in growing a green alga, Chlamydomonas reinhardtii. The laser treatments tested included: 655-nm Red; 680-nm Red; 655-nm Red+474-nm Blue and 680-nm Red+474-nm Blue. A white cold cathode lamp with spectral output similar to that of white fluorescent lamp served as control. C. reinhardtii successfully grew and divided under the 655 and 680-nm red lasers as well as under the white-light control. Supplementing either red with blue laser, however, resulted in increased algae cell count that significantly exceeded those under both red lasers and the white-light control on average by 241%.     

Absorption and Fluorescence Properties of Chromophoric Dissolved Organic Matter Produced by AlgaeSCIEI北大核心CSCD

Four kinds of diatom (Chaetoceros curvisetus, Phaeodactylumtricornutum, Nitzschia closterium f. minutissima and Navicula halophile) and two kinds of dinoflagellates (Prorocentrum donghaiense and Gymnodinium) were cultured under laboratory conditions. Variations of optical properties of chromophoric dissolved organic matter (CDOM) were studied with absorption and fluorescence excitation-emission matrix spectroscopy(EEM) during growth of marine microalgae in incubation experiment. Absorption spectrum revealed absorption coefficient a(355) (CDOM absorption coefficients at 355 nm) of 6 kinds of marine microalgae above increased by 64.8%, 242.3%, 535.1%, 903.2%, 836% and 196.4%, respectively. Simultaneously, the absorption spectral slope(Sg), determined between 270 and 350 rim, representing the size of molecular weight of CDOM and humic-like composition, decreased by 8.7%, 34.6%, 39.4%, 53.1%, 46.7%, and 35.7%, respectively. Applying parallel factor analysis (PARAFAC) together with EEM got four components of CDOM: C1(Ex/Em=350(260) nm/450 nm), C2 (Ex/Em=260 (430) nm/525 nm) 03 (Ex/Em=325 nm/400 nm) and C4(Ex/Em=275 nm/325 nm), which.were relative to three humic-like and one protein-like fluorescent components of Nitzschia closterium f. minutissima and Navicula halophile. In incubation experiment, fluorescence intensity of these four components during growth of Nitzschia closterium f. minutissima increased by, respectively, 8.68, 24.9, 7.19 and 39.8 times, and those of Navicula halophile increased by 2.64, 0.07, 4.39 and 12.4 times, respectively. Significant relationships were found between the fluorescence intensity of four components of CDOM, a(355) and Sg. All results demonstrated that both content and molecular weight of CDOM produced by diatom and dinoflagellate studied in incubation experiment increased, but these two parameters changed more obviously of the diatom than those of dinoflagellate; the proportion of humic-like components in the composition of CDOM also increased clearly with the growth of marine microalgae, but protein-like fluorescent component had only a slow growth. Furthermore, the absorption spectrum of CDOM produced by different species of algae changed obviously and the relative composition fluorescence intensity of CDOM produced by different microalgae were found to vary among different composition from EEM, which suggested CDOM produced by different microalgae make quite different contributions to CDOM in natural seawater.