Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 6 de 6
Filter
Add more filters










Database
Language
Publication year range
1.
Food Chem ; 135(4): 2575-83, 2012 Dec 15.
Article in English | MEDLINE | ID: mdl-22980845

ABSTRACT

Coffee grown at high elevations fetches a better price than that grown in lowland regions. This study was aimed at determining whether climatic conditions during bean development affected sensory perception of the coffee beverage and combinations of volatile compounds in green coffee. Green coffee samples from 16 plots representative of the broad range of climatic variations in Réunion Island were compared by sensory analysis. Volatiles were extracted by solid phase micro-extraction and the volatile compounds were analysed by GC-MS. The results revealed that, among the climatic factors, the mean air temperature during seed development greatly influenced the sensory profile. Positive quality attributes such as acidity, fruity character and flavour quality were correlated and typical of coffees produced at cool climates. Two volatile compounds (ethanal and acetone) were identified as indicators of these cool temperatures. Among detected volatiles, most of the alcohols, aldehydes, hydrocarbons and ketones appeared to be positively linked to elevated temperatures and high solar radiation, while the sensory profiles displayed major defects (i.e. green, earthy flavour). Two alcohols (butan-1,3-diol and butan-2,3-diol) were closely correlated with a reduction in aromatic quality, acidity and an increase in earthy and green flavours. We assumed that high temperatures induce accumulation of these compounds in green coffee, and would be detected as off-flavours, even after roasting. Climate change, which generally involves a substantial increase in average temperatures in mountainous tropical regions, could be expected to have a negative impact on coffee quality.


Subject(s)
Coffea/chemistry , Coffee/chemistry , Odorants/analysis , Volatile Organic Compounds/analysis , Climate , Coffea/growth & development , Coffea/metabolism , Coffee/standards , Ecosystem , Humans , Quality Control , Taste , Volatile Organic Compounds/metabolism
2.
Expert Opin Ther Targets ; 7(5): 593-602, 2003 Oct.
Article in English | MEDLINE | ID: mdl-14498822

ABSTRACT

Chemotherapy of malaria parasites is limited by established drug resistance and lack of novel treatment options. Intraerythrocytic stages of Plasmodium falciparum, the causative agent of severe malaria, are wholly dependent upon host glucose for energy. A facilitative hexose transporter (PfHT), encoded by a single-copy gene, mediates glucose uptake and is therefore an attractive potential target. The authors first established heterologous expression in Xenopus laevis to allow functional characterisation of PfHT. They then used this expression system to compare the interaction of substrates with PfHT and mammalian Gluts (hexose transporters) and identified important differences between host and parasite transporters. Certain Omethyl derivatives of glucose proved to be particularly useful discriminators between mammalian transporters and PfHT. The authors exploited this selectivity and synthesised an O-3 hexose derivative that potently inhibits PfHT expressed in oocytes. This O-3 derivative (compound 3361) also kills cultured P. falciparum with comparable potency. Compound 3361 acts with reasonable specificity against PfHT orthologues encoded by other parasites such as Plasmodium vivax, Plasmodium yoelii and Plasmodium knowlesi. Multiplication of Plasmodium berghei in a mouse model is also significantly impeded by this compound. These findings validate PfHT as a novel target.


Subject(s)
Antimalarials/pharmacology , Drug Design , Glucose/analogs & derivatives , Malaria, Falciparum/drug therapy , Monosaccharide Transport Proteins/antagonists & inhibitors , Plasmodium falciparum/drug effects , Protozoan Proteins/antagonists & inhibitors , Amino Acid Sequence , Animals , Antimalarials/therapeutic use , Drug Evaluation, Preclinical , Energy Metabolism/drug effects , Fermentation , Fructose/metabolism , Gene Expression Regulation , Glucose/chemistry , Glucose/metabolism , Glycolysis/drug effects , Humans , Malaria, Falciparum/parasitology , Mammals/metabolism , Mice , Molecular Sequence Data , Monosaccharide Transport Proteins/genetics , Monosaccharide Transport Proteins/physiology , Mutagenesis, Site-Directed , Plasmodium/drug effects , Plasmodium/enzymology , Plasmodium falciparum/enzymology , Plasmodium falciparum/genetics , Plasmodium falciparum/growth & development , Protozoan Proteins/genetics , Protozoan Proteins/physiology , Recombinant Fusion Proteins/antagonists & inhibitors , Sequence Alignment , Sequence Homology, Amino Acid , Species Specificity , Structure-Activity Relationship , Substrate Specificity , Xenopus laevis
3.
Appl Microbiol Biotechnol ; 60(1-2): 114-9, 2002 Oct.
Article in English | MEDLINE | ID: mdl-12382051

ABSTRACT

Seeds of the tropical tree Moringa oleifera contain small storage proteins able to flocculate particles in suspension in water. The cDNA encoding one of these flocculent proteins, MO(2.1), was cloned and the recombinant protein was expressed in Escherichia coli. The flocculent activity of the purified recombinant MO(2.1)was assayed on clays and bacteria using light and confocal microscopy and GFP-overexpressing bacteria. We show that MO(2.1)is able to aggregate montmorillonite clay particles as well as gram-positive and gram-negative bacteria. We discuss the use of recombinant proteins to study flocculating properties and improve water purification processes.


Subject(s)
Gram-Negative Bacteria/drug effects , Gram-Positive Bacteria/drug effects , Moringa oleifera/chemistry , Plant Proteins/chemistry , Plant Proteins/pharmacology , Seeds/chemistry , Amino Acid Sequence , Base Sequence , Cloning, Molecular , Escherichia coli , Flocculation , Gram-Negative Bacteria/ultrastructure , Gram-Positive Bacteria/ultrastructure , Microscopy, Confocal , Molecular Sequence Data , Plant Proteins/genetics , Plant Proteins/isolation & purification , Recombinant Proteins/chemistry , Sequence Analysis
4.
Plant Physiol ; 125(4): 1919-29, 2001 Apr.
Article in English | MEDLINE | ID: mdl-11299371

ABSTRACT

Tobacco (Nicotiana tabacum var Petit Havana) ndhB-inactivated mutants (ndhB-) obtained by plastid transformation (E.M. Horvath, S.O. Peter, T. Joët, D. Rumeau, L. Cournac, G.V. Horvath, T.A. Kavanagh, C. Schäfer, G. Peltier, P. MedgyesyHorvath [2000] Plant Physiol 123: 1337-1350) were used to study the role of the NADH-dehydrogenase complex (NDH) during photosynthesis and particularly the involvement of this complex in cyclic electron flow around photosystem I (PSI). Photosynthetic activity was determined on leaf discs by measuring CO2 exchange and chlorophyll fluorescence quenchings during a dark-to-light transition. In the absence of treatment, both non-photochemical and photochemical fluorescence quenchings were similar in ndhB- and wild type (WT). When leaf discs were treated with 5 microM antimycin A, an inhibitor of cyclic electron flow around PSI, both quenchings were strongly affected. At steady state, maximum photosynthetic electron transport activity was inhibited by 20% in WT and by 50% in ndhB-. Under non-photorespiratory conditions (2% O2, 2,500 microL x L(-1) CO2), antimycin A had no effect on photosynthetic activity of WT, whereas a 30% inhibition was observed both on quantum yield of photosynthesis assayed by chlorophyll fluorescence and on CO2 assimilation in ndhB-. The effect of antimycin A on ndhB- could not be mimicked by myxothiazol, an inhibitor of the mitochondrial cytochrome bc1 complex, therefore showing that it is not related to an inhibition of the mitochondrial electron transport chain but rather to an inhibition of cyclic electron flow around PSI. We conclude to the existence of two different pathways of cyclic electron flow operating around PSI in higher plant chloroplasts. One of these pathways, sensitive to antimycin A, probably involves ferredoxin plastoquinone reductase, whereas the other involves the NDH complex. The absence of visible phenotype in ndhB- plants under normal conditions is explained by the complement of these two pathways in the supply of extra-ATP for photosynthesis.


Subject(s)
Antimycin A/pharmacology , NADH Dehydrogenase/metabolism , Nicotiana/physiology , Photosynthesis/physiology , Photosynthetic Reaction Center Complex Proteins/metabolism , Plant Proteins/genetics , Plants, Toxic , Carbon Dioxide/metabolism , Chlorophyll/metabolism , Electron Transport , Kinetics , Light , Light-Harvesting Protein Complexes , Methacrylates , Photosynthesis/drug effects , Photosystem I Protein Complex , Plastids/genetics , Thiazoles/pharmacology , Nicotiana/drug effects , Nicotiana/genetics
5.
Philos Trans R Soc Lond B Biol Sci ; 355(1402): 1447-54, 2000 Oct 29.
Article in English | MEDLINE | ID: mdl-11127998

ABSTRACT

Besides electron transfer reactions involved in the 'Z' scheme of photosynthesis, alternative electron transfer pathways have been characterized in chloroplasts. These include cyclic electron flow around photosystem I (PS I) or a respiratory chain called chlororespiration. Recent work has supplied new information concerning the molecular nature of the electron carriers involved in the non-photochemical reduction of the plastoquinone (PQ) pool. However, until now little is known concerning the nature of the electron carriers involved in PQ oxidation. By using mass spectrometric measurement of oxygen exchange performed in the presence of 18O-enriched O2 and Chlamydomonas mutants deficient in PS I, we show that electrons can be directed to a quinol oxidase sensitive to propyl gallate but insensitive to salicyl hydroxamic acid. This oxidase has immunological and pharmacological similarities with a plastid protein involved in carotenoid biosynthesis.


Subject(s)
Chloroplasts/enzymology , Light-Harvesting Protein Complexes , Oxidoreductases/metabolism , Photosynthesis/physiology , Photosynthetic Reaction Center Complex Proteins/metabolism , Photosystem I Protein Complex , Thylakoids/metabolism , Animals , Cell Respiration , Chlamydomonas reinhardtii/metabolism , Chloroplasts/metabolism , Cytochrome b Group/metabolism , Cytochrome b6f Complex , Electron Transport , Membrane Proteins/genetics , Membrane Proteins/physiology , Oxygen/metabolism , Photosynthetic Reaction Center Complex Proteins/genetics , Plant Proteins/genetics , Plant Proteins/physiology
6.
Plant Physiol ; 123(4): 1337-50, 2000 Aug.
Article in English | MEDLINE | ID: mdl-10938352

ABSTRACT

The ndh genes encoding for the subunits of NAD(P)H dehydrogenase complex represent the largest family of plastid genes without a clearly defined function. Tobacco (Nicotiana tabacum) plastid transformants were produced in which the ndhB gene was inactivated by replacing it with a mutant version possessing translational stops in the coding region. Western-blot analysis indicated that no functional NAD(P)H dehydrogenase complex can be assembled in the plastid transformants. Chlorophyll fluorescence measurements showed that dark reduction of the plastoquinone pool by stromal reductants was impaired in ndhB-inactivated plants. Both the phenotype and photosynthetic performance of the plastid transformants was completely normal under favorable conditions. However, an enhanced growth retardation of ndhB-inactivated plants was revealed under humidity stress conditions causing a moderate decline in photosynthesis via stomatal closure. This distinctive phenotype was mimicked under normal humidity by spraying plants with abscisic acid. Measurements of CO(2) fixation demonstrated an enhanced decline in photosynthesis in the mutant plants under humidity stress, which could be restored to wild-type levels by elevating the external CO(2) concentration. These results suggest that the plastid NAD(P)H:plastoquinone oxidoreductase in tobacco performs a significant physiological role by facilitating photosynthesis at moderate CO(2) limitation.


Subject(s)
Gene Silencing , NADPH Dehydrogenase/metabolism , Nicotiana/metabolism , Photosynthesis , Plant Proteins/metabolism , Plants, Toxic , Plastids/metabolism , Abscisic Acid/metabolism , Abscisic Acid/pharmacology , Base Sequence , Blotting, Western , Carbon Dioxide/metabolism , Humidity , Molecular Sequence Data , NADPH Dehydrogenase/genetics , Oxygen/metabolism , Phenotype , Plant Leaves/genetics , Plant Leaves/metabolism , Plant Proteins/genetics , Plastids/genetics , Nicotiana/genetics , Nicotiana/growth & development
SELECTION OF CITATIONS
SEARCH DETAIL
...