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Myostatin is a negative regulator of muscle growth. When it is not present or non-functional double-muscling occurs, the primary characteristic of this phenotype being an increase in muscle mass. Another characteristic of double-muscling is an increased proportion of type IIB muscle fibres, which rely on glycolysis as their primary energy source, as opposed to type IIA and type I fibres which rely on oxidative phosphorylation. This switch in muscle metabolism directly impacts on the mitochondria, as mitochondria from glycolytic muscle fibres have been shown to have differences in metabolic activity. The increased proportion of glycolytic muscle fibres present in myostatin knockout animals provides a unique model to investigate alterations in muscle fibre type metabolism. The mouse model of myostatin knockout utilised during this stud...
Cyanobacteria (blue-green algae) are a group of ancient prokaryotic organisms which have become synonymous with water quality deterioration. An array of compounds is produced by aquatic cyanobacteria, the largest group being the oligopeptides. A major class of cyanobacterial oligopeptides are the microcystins; cyclic heptapeptides which contain the unique amino acid Adda (3 amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid). Due to their ability to inhibit protein phosphatases 1 and 2A and as they are concentrated in the liver, microcystins can be highly toxic to animals. Anabaenopeptins are cyclic hexapeptides which contain a carbonyl-linked sidechain amino acid and a ring which is cyclised through the sidechain amine of the position two D-lysine. Matrix-assisted laser desorption/ionisation-time of flight mass spectromet...
Introduction – The tolyporphins are metabolites isolated from the cyanobacterium Tolypothrix nodosa, comprising a porphyrin-like macrocycle with C-glycoside, hydroxide or acetate substituents. Previous studies of porphyrins by MALDI/LDI-TOF MS indicate that strong radical cations and anions are usually observed in the parent spectra with little fragmentation of the macrocycle. The spectra of the tolyporphins were obtained and trends in the series utilised to partially characterise two new analogues. Objective – To examine tolyporphins by LDI-TOF MS and utilise trends observed to partially characterise two new analogues. Methodology – The tolyporphins were analysed by LDI-TOF MS in positive and negative ion mode and by a post source decay method (LIFT) in positive ion mode. Tolyporphin A was also analysed by MALDI-TOF MS for comparison....
Cyanobacteria (blue-green algae) are a group of ancient prokaryotic organisms dating back between three and four billion years.¹ They have been attributed with oxygenating the earth’s atmosphere² but, since the anthropogenic euthrophication of lakes, ponds and oceans, they have become synonymous with water hygiene issues.³ This is due to the alteration of the nutrient composition of their habitat to one which is optimal for growth (or blooms). Cyanobacterial blooms may simply cause foul tastes and odours,⁴ but they can also lead to the production of toxic secondary metabolites poisonous to humans and animals upon ingestion.⁵ NZ has yet to suffer a human fatality, but the deaths of several dogs in Wellington was attributed to homoanatoxin-a 1 (Chart 1) from a Phormidium species.⁶
Myostatin is a secreted protein which is known to be a negative regulator of skeletal muscle growth. Numerous studies have demonstrated that down-regulating the expression of myostatin results in an increase in muscle mass. This increase in skeletal muscle is accompanied by a marked change in the muscle fibre composition from one reliant on mitochondrial oxidative metabolism to one more focused on glycolytic metabolism. A comparative proteomics study was undertaken to investigate the effect of this altered metabolism has on the mitochondria from the gastrocnemius muscle of myostatin null mice, compared with those from wild type mice. The majority of the proteins identified showed no significant modulation between the two phenotypes, but gives an interesting insight into observations made in previous studies. Several proteins were shown...
As the only known example of complete organ regeneration in mammals, deer antler in the growing or velvet phase is of major interest in developmental biology. This regeneration event initiates from self-renewing antler stem cells that exhibit pluripotency. At present, it remains unclear how the activation and quiescence of antler stem cells are regulated. Therefore, in the present study proteins that were differentially expressed between the antler stem cells and somatic cells (facial periosteum) were identified by a gel-based proteomic technique, and analysed using Ingenuity Pathway Analysis software. Several molecular pathways (PI3K/Akt, ERK/MAPK, p38 MAPK, etc.) were found to be activated during proliferation. Also expressed were the transcription factors POU5F1, SOX2, NANOG and MYC, which are key markers of embryonic stem cells. Ex...
Lagunamides A (1) and B (2) are new cyclic depsipeptides isolated from the marine cyanobacterium Lyngbya majuscula obtained from Pulau Hantu Besar, Singapore. The planar structural characterization of these molecules was achieved by extensive spectroscopic analysis, including 2D NMR experiments. In addition to Marfey’s method and 3JH−H coupling constant values, a modified method based on Mosher’s reagents and analysis using LC-MS was deployed for the determination of the absolute configuration. Lagunamides A and B displayed significant antimalarial properties, with IC₅₀ values of 0.19 and 0.91 μM, respectively, when tested against Plasmodium falciparum. Lagunamides A and B also possessed potent cytotoxic activity against P388 murine leukemia cell lines, with IC₅₀ values of 6.4 and 20.5 nM, respectively. Furthermore, these cyanobacteri...
Introduction: Microcystins (MCs) are a group of cyanotoxins which pose a serious health threat when present in aquatic systems. Quantitative analysis of MCs by matrix-assisted laser desorption/ionisation–time of flight (MALDI–TOF) mass spectrometry has potential for the processing of large numbers of samples quickly and economically. The existing method uses an expensive internal standard and protocols that are incompatible with automated sample preparation and data acquisition. Objective: To produce a MALDI–TOF sample preparation technique for the quantitation of MCs that not only maintains reproducibility and sensitivity, but is also compatible with an automated work-flow. Methodology: Seven different MALDI–TOF sample preparations were assessed for signal reproducibility (coefficient of variation) and sensitivity (method detection li...
Chemical investigation of the marine cyanobacterium Lyngbya majuscula from Pulau Hantu Besar, Singapore, has led to the isolation of a cyclodepsipeptide, hantupeptin A (1). The planar structure of 1 was assigned on the basis of extensive 1D and 2D NMR spectroscopic experiments. The absolute configuration of the amino and hydroxyl acid residues in the molecule was determined by application of the advanced Marfey method, chiral HPLC analysis, and Mosher’s method. Hantupeptin A showed cytotoxicity to MOLT-4 leukemia cells and MCF-7 breast cancer cells with IC50 values of 32 and 4.0 µM, respectively.
Hantupeptins B (2) and C (3) were isolated, along with the previously reported hantupeptin A (1), from the marine cyanobacterium, Lyngbya majuscula, collected from Pulau Hantu Besar, Singapore. Their structures were elucidated by interpretation of extensive 1D and 2D NMR spectroscopic data. Compounds 2 and 3 are cyclic depsipeptides consisting of five α-amino/hydroxy acid residues, including phenyllactic acid, proline, N-methyl-valine, valine, N-methyl-isoleucine, and a β-hydroxy acid unit with different degrees of unsaturation at the terminal end of each molecule. The absolute configurations of the common amino acids and phenyllactic acid were determined by the advanced Marfey’s and chiral HPLC analyses, respectively. The complete stereochemistry of 3-hydroxy-2-methyl-7-octynoic acid moiety in hantupeptin A was elucidated by a combina...
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