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It is generally agreed that the hepatotoxic microcystins (MCs) are the most abundant toxins produced by cyanobacteria in freshwater. In various freshwater lakes in East Africa MC-producing Microcystis has been reported to dominate the phytoplankton, however the regulation of MC production is poorly understood. From May 2007 to April 2008 the Microcystis(More)
[structure: see text] Nostocarboline and seven derivatives were prepared and displayed minimal inhibitory concentration (MIC) values >or=100 nM against the growth of Microcystis aeruginosa PCC 7806, Synechococcus PCC 6911, and Kirchneriella contorta SAG 11.81, probably via the inhibition of photosynthesis. The natural product hybrid(More)
As NAD(+) is a rate-limiting cosubstrate for the sirtuin enzymes, its modulation is emerging as a valuable tool to regulate sirtuin function and, consequently, oxidative metabolism. In line with this premise, decreased activity of PARP-1 or CD38-both NAD(+) consumers-increases NAD(+) bioavailability, resulting in SIRT1 activation and protection against(More)
Aerucyclamides C and D were isolated from the cyanobacterium Microcystis aeruginosa PCC 7806, and their structures established by NMR spectroscopy and chemical transformation and degradation. Acidic hydrolysis of aerucyclamide C (CF(3)CO(2)H, H(2)O) resulted in microcyclamide 7806A. This chemical evidence combined with spectroscopic and physical data(More)
Two new modified hexacyclopeptides, aerucyclamides A and B, were isolated from the toxic freshwater cyanobacterium Microcystis aeruginosa PCC 7806. The constitution was assigned by spectroscopic methods, and the configuration determined by chemical degradation and analysis by Marfey's method combined with chemical synthesis. Synthetic aerucyclamide B was(More)
The structural and thermodynamic properties of a 6-residue beta-peptide that was designed to form a hairpin conformation have been studied by NMR spectroscopy and MD simulation in methanol solution. The predicted hairpin would be characterized by a 10-membered hydrogen-bonded turn involving residues 3 and 4, and two extended antiparallel strands. The(More)
Oligomers of beta-amino acids (beta-peptides), which are readily available by standard meth ods either in solution or on solid support, adopt a large variety of different secondary structures in solution and in the solid state. beta-Peptides 4, 5 and 10 fold into a helix with 3 residues per turn and 14-membered H-bonded rings (314 helix) that is left-handed(More)
A new quaternary beta-carboline alkaloid, nostocarboline, was isolated from the freshwater cyanobacterium Nostoc 78-12A, and its constitution was assigned by 2D-NMR methods. The structure was proven by its total synthesis starting from norharmane via chlorination at C-6 and methylation at N-2. Nostocarboline was found to be a potent butyrylcholinesterase(More)
The isolation and structure of cyanopeptolin 1020 (hexanoic acid-Glu-N[-O-Thr-Arg-Ahp-Phe-N-Me-Tyr-Val-]) from a Microcystis strain is reported. Very potent picomolar trypsin inhibition (IC(50) = 670 pM) and low nanomolar values against human kallikrein (4.5 nM) and factor XIa (3.9 nM) have been determined for cyanopeptolin 1020. For plasmin and(More)
Microcystins (MCs) are cyclic heptapeptides, which are the most abundant toxins produced by cyanobacteria in freshwater. The phytoplankton of many freshwater lakes in Eastern Africa is dominated by cyanobacteria. Less is known, however, on the occurrence of MC producers and the production of MCs. Twelve Ugandan freshwater habitats ranging from mesotrophic(More)