1H-NMR metabolite profiles of different strains of Plasmodium falciparum

Although efforts to understand the basis for inter-strain phenotypic variation in the most virulent malaria species, Plasmodium falciparum, have benefited from advances in genomic technologies, there have to date been few metabolomic studies of this parasite. Using 1H-NMR spectroscopy, we have compared the metabolite profiles of red blood cells infected with different P. falciparum strains. These included both chloroquine-sensitive and chloroquine-resistant strains, as well as transfectant lines engineered to express different isoforms of the chloroquine-resistance-conferring pfcrt (P. falciparum chloroquine resistance transporter). Our analyses revealed strain-specific differences in a range of metabolites. There was marked variation in the levels of the membrane precursors choline and phosphocholine, with some strains having >30-fold higher choline levels and >5-fold higher phosphocholine levels than others. Chloroquineresistant strains showed elevated levels of a number of amino acids relative to chloroquine-sensitive strains, including an approximately 2-fold increase in aspartate levels. The elevation in amino acid levels was attributable to mutations in pfcrt. Pfcrt-linked differences in amino acid abundance were confirmed using alternate extraction and detection (HPLC) methods. Mutations acquired to withstand chloroquine exposure therefore give rise to significant biochemical alterations in the parasite

The glucans extracted with warm water from diatoms are mainly derived from intracellular chysolaminaran and not extracellular polysaccharides

Several recent studies have employed warm-water treatment of diatom cells to extract nominally bound extracellular polymeric substances. Where examined, the dominant neutral sugar in these extracts was glucose. In the present study, we sought to characterize the structure of the glucose-rich polymers in the water extracts of diatoms and to determine the origin of these polymers. The marine diatoms surveyed were Phaeodactylum tricornutum, Cylindrotheca fusiformis, Craspedostauros australis and Thalassiosira pseudonana. A freshwater species, Pinnularia viridis, was also investigated for the dye labelling experiments. Freshly harvested marine diatoms were extracted with water at 308C for 1 h. Constituent monosaccharide analyses showed that glucose was the dominant neutral sugar (80 - 95 mol% of the total) in the extracts from three marine species, whereas the P. tricornutum extract contained predominantly ribose, galactose and glucose, and was inferred to be enriched in low-molecular-weight components. Linkage analysis of the constituent monosaccharides and proton nuclear magnetic resonance spectroscopy showed that the glucose in these extracts was derived primarily from 1,3-b-D-glucan. Immunocytochemistry with a monoclonal anti-1,3-b-D-glucan antibody confirmed that the glucan was localized in the vacuoles of diatom cells preserved by freeze-substitution. Nearly all diatom cells incubated with a fluorescent dye, DiBAC4(3), during warm water treatment at 308C or 608C incorporated the dye, demonstrating that the membrane integrity of the diatoms was compromised and supporting the contention that intracellular glucan was released during the treatment. In light of these data, the extracellular glucans of diatoms reported in some previous studies are re-interpreted as intracellular chrysolaminaran

Metabolite profiling of the intraerythrocytic malaria parasite Plasmodium falciparum by (1)H NMR spectroscopy

NMR spectroscopy was used to identify and quantify compounds in extracts prepared from mature trophozoite-stage Plasmodium falciparum parasites isolated by saponin-permeabilisation of the host erythrocyte. One-dimensional 1H NMR spectroscopy and four two-dimensional NMR techniques were used to identify more than 50 metabolites. The intracellular concentrations of over 40 metabolites were estimated from the 1H NMR spectra of extracts prepared by four extraction methods: perchloric acid, methanol/water, methanol/chloroform/water, and methanol alone. The metabolites quantified included: the majority of the biological α-amino acids; 4-aminobutyric acid; mono-, di- and tri-carboxylic acids; nucleotides; polyamines; myo-inositol; and phosphocholine and phosphoethanolamine. The parasites also contained a significant concentration (up to 12 mM) of the exogenous buffering agent, HEPES. Although the metabolite profiles obtained with each extraction method were broadly similar, perchloric acid was found to have significant advantages over the other extraction media

Feedback Inhibition of Pantothenate Kinase Regulates Pantothenol Uptake by the Malaria Parasite

To survive, the human malaria parasite Plasmodium falciparum must acquire pantothenate (vitamin B5) from the external medium. Pantothenol (provitamin B5) inhibits parasite growth by competing with pantothenate for pantothenate kinase, the first enzyme i

Fabrication of 1.55μm Si-Based Resonant Cavity Enhanced Photodetectors

A novel bonding method using silicate gel as bonding medium is developed.High reflective SiO2/Si mirrors deposited on silicon substrates by e-beam deposition are bonded to the active layers at a low temperature of 350℃ without any special treatment on bonding surfaces.The reflectivities of the mirrors can be as high as 99.9%.A Si-based narrow band response InGaAs photodetector is successfully fabricated,with a quantum efficiency of 22.6% at the peak wavelength of 1.54μm,and a full width at half maximum of about 27nm.This method has a great potential for industry processes