References of "Biochimica et biophysica acta"
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See detailEffects of surfactin on membrane models displaying lipid phase separation.
Deleu, Magali ULg; Lorent, Joseph; Lins, Laurence ULg et al

in Biochimica et Biophysica Acta (2013), 1828(2), 801-815

Surfactin, a bacterial amphiphilic lipopeptide is attracting more and more attention in view of its bioactive properties which are in relation with its ability to interact with lipids of biological ... [more ▼]

Surfactin, a bacterial amphiphilic lipopeptide is attracting more and more attention in view of its bioactive properties which are in relation with its ability to interact with lipids of biological membranes. In this work, we investigated the effect of surfactin on membrane structure using model of membranes, vesicles as well as supported bilayers, presenting coexistence of fluid-disordered (DOPC) and gel (DPPC) phases. A range of complementary methods was used including AFM, ellipsometry, dynamic light scattering, fluorescence measurements of Laurdan, DPH, calcein release, and octadecylrhodamine B dequenching. Our findings demonstrated that surfactin concentration is critical for its effect on the membrane. The results suggest that the presence of rigid domains can play an essential role in the first step of surfactin insertion and that surfactin interacts both with the membrane polar heads and the acyl chain region. A mechanism for the surfactin lipid membrane interaction, consisting of three sequential structural and morphological changes, is proposed. At concentrations below the CMC, surfactin inserted at the boundary between gel and fluid lipid domains, inhibited phase separation and stiffened the bilayer without global morphological change of liposomes. At concentrations close to CMC, surfactin solubilized the fluid phospholipid phase and increased order in the remainder of the lipid bilayer. At higher surfactin concentrations, both the fluid and the rigid bilayer structures were dissolved into mixed micelles and other structures presenting a wide size distribution. [less ▲]

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See detailModeling of non-covalent complexes of the cell-penetrating peptide CADY and its siRNA cargo.
Crowet, Jean-Marc ULg; Lins, Laurence ULg; Deshayes, Sebastien et al

in Biochimica et Biophysica Acta (2012)

CADY is a cell-penetrating peptide spontaneously making non-covalent complexes with siRNAs in water. Neither the structure of CADY nor that of the complexes is resolved. We have calculated and analyzed 3D ... [more ▼]

CADY is a cell-penetrating peptide spontaneously making non-covalent complexes with siRNAs in water. Neither the structure of CADY nor that of the complexes is resolved. We have calculated and analyzed 3D models of CADY and of the non-covalent CADY-siRNA complexes in order to understand their formation and stabilization. Data from the ab initio calculations and molecular dynamics support that, in agreement with the experimental data, CADY is a polymorphic peptide partly helical. Taking into consideration the polymorphism of CADY, we calculated and compared several complexes with peptide/siRNA ratios of up to 40. Four complexes were run by using molecular dynamics. The initial binding of CADYs is essentially due to the electrostatic interactions of the arginines with siRNA phosphates. Due to a repetitive arginine motif (XLWR(K)) in CADY and to the numerous phosphate moieties in the siRNA, CADYs can adopt multiple positions at the siRNA surface leading to numerous possibilities of complexes. Nevertheless, several complex properties are common: an average of 14+/-1 CADYs is required to saturate a siRNA as compared to the 12+/-2 CADYs experimentally described. The 40 CADYs/siRNA that is the optimal ratio for vector stability always corresponds to two layers of CADYs per siRNA. When siRNA is covered by the first layer of CADYs, the peptides still bind despite the electrostatic repulsion. The peptide cage is stabilized by hydrophobic CADY-CADY contacts thanks to CADY polymorphism. The analysis demonstrates that the hydrophobicity, the presence of several positive charges and the disorder of CADY are mandatory to make stable the CADY-siRNA complexes. [less ▲]

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See detailThe Pseudomonas aeruginosa membranes: A target for a new amphiphilic aminoglycoside derivative?
Ouberai, M.; El Garch, F.; Bussiere, A. et al

in Biochimica et biophysica acta (2011)

Aminoglycosides are among the most potent antimicrobials to eradicate Pseudomonas aeruginosa. However, the emergence of resistance has clearly led to a shortage of treatment options, especially for ... [more ▼]

Aminoglycosides are among the most potent antimicrobials to eradicate Pseudomonas aeruginosa. However, the emergence of resistance has clearly led to a shortage of treatment options, especially for critically ill patients. In the search for new antibiotics, we have synthesized derivatives of the small aminoglycoside, neamine. The amphiphilic aminoglycoside 3',4',6-tri-2-naphtylmethylene neamine (3',4',6-tri-2NM neamine) has appeared to be active against sensitive and resistant P. aeruginosa strains as well as Staphylococcus aureus strains (Baussanne et al., 2010). To understand the molecular mechanism involved, we determined the ability of 3',4',6-tri-2NM neamine to alter the protein synthesis and to interact with the bacterial membranes of P. aeruginosa or models mimicking these membranes. Using atomic force microscopy, we observed a decrease of P. aeruginosa cell thickness. In models of bacterial lipid membranes, we showed a lipid membrane permeabilization in agreement with the deep insertion of 3',4',6-tri-2NM neamine within lipid bilayer as predicted by modeling. This new amphiphilic aminoglycoside bound to lipopolysaccharides and induced P. aeruginosa membrane depolarization. All these effects were compared to those obtained with neamine, the disubstituted neamine derivative (3',6-di-2NM neamine), conventional aminoglycosides (neomycin B and gentamicin) as well as to compounds acting on lipid bilayers like colistin and chlorhexidine. All together, the data showed that naphthylmethyl neamine derivatives target the membrane of P. aeruginosa. This should offer promising prospects in the search for new antibacterials against drug- or biocide-resistant strains. [less ▲]

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See detailEffects of monopropanediamino-beta-cyclodextrin on the denaturation process of the hybrid protein BlaPChBD.
Vandevenne, Marylène ULg; GASPARD, Genevieve ULg; Belgsir, E. M. et al

in Biochimica et biophysica acta (2011)

Irreversible accumulation of protein aggregates represents an important problem both in vivo and in vitro. The aggregation of proteins is of critical importance in a wide variety of biomedical situations ... [more ▼]

Irreversible accumulation of protein aggregates represents an important problem both in vivo and in vitro. The aggregation of proteins is of critical importance in a wide variety of biomedical situations, ranging from diseases (such as Alzheimer's and Parkinson's diseases) to the production (e.g. inclusion bodies), stability, storage and delivery of protein drugs. beta-Cyclodextrin (beta-CD) is a circular heptasaccharide characterized by a hydrophilic exterior and a hydrophobic interior ring structure. In this research, we studied the effects of a chemically modified beta-CD (BCD07056), on the aggregating and refolding properties of BlaPChBD, a hybrid protein obtained by inserting the chitin binding domain of the human macrophage chitotriosidase into the class A beta-lactamase BlaP from Bacillus licheniformis 749/I during its thermal denaturation. The results show that BCD07056 strongly increases the refolding yield of BlaPChBD after thermal denaturation and constitutes an excellent additive to stabilize the protein over time at room temperature. Our data suggest that BCD07056 acts early in the denaturation process by preventing the formation of an intermediate which leads to an aggregated state. Finally, the role of beta-CD derivatives on the stability of proteins is discussed. [less ▲]

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See detailComparative study of mature and zymogen mite cysteine protease stability and pH unfolding.
Chevigne, A.; Dumez, Marie-Eve ULg; Dumoulin, Mireille ULg et al

in Biochimica et Biophysica Acta (2010), 1800(9), 937-945

BACKGROUND: Papain-like proteases (CA1) are synthesized as inactive precursors carrying an N-terminal propeptide, which is further removed under acidic conditions to generate active enzymes. METHODS: To ... [more ▼]

BACKGROUND: Papain-like proteases (CA1) are synthesized as inactive precursors carrying an N-terminal propeptide, which is further removed under acidic conditions to generate active enzymes. METHODS: To have a better insight into the mechanism of activation of this protease family, we compared the pH unfolding of the zymogen and the mature form of the mite cysteine protease Der p 1. RESULTS: We showed that the presence of the propeptide does not significantly influence the pH-induced unfolding of the catalytic domain but does affect its fluorescence properties by modifying the exposure of the tryptophan 192 to the solvent. In addition, we demonstrated that the propeptide displays weaker pH stability than the protease domain confirming that the unfolding of the propeptide is the key event in the activation process of the zymogen. GENERAL SIGNIFICANCE: Finally, we show, using thermal denaturation and enzymatic activity measurements, that whatever the pH value, the propeptide does not stabilize the structure of the catalytic domain but very interestingly, prevents its autolysis. [less ▲]

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See detailThe onset of NPQ and Deltamu(H)+ upon illumination of tobacco plants studied through the influence of mitochondrial electron transport.
Cardol, Pierre ULg; De Paepe, Rosine; Franck, Fabrice ULg et al

in Biochimica et Biophysica Acta (2010), 1797(2), 177-88

The relationship between the development of photoprotective mechanisms (non-photochemical quenching, NPQ), the generation of the electrochemical proton gradient in the chloroplast and the capacity to ... [more ▼]

The relationship between the development of photoprotective mechanisms (non-photochemical quenching, NPQ), the generation of the electrochemical proton gradient in the chloroplast and the capacity to assimilate CO(2) was studied in tobacco dark-adapted leaves at the onset of illumination with low light. These conditions induce the generation of a transient NPQ, which relaxes in the light in parallel with the activation of the Calvin cycle. Wild-type plants were compared with a CMSII mitochondrial mutant, which lacks the respiratory complex I and shows a delayed activation of photosynthesis. In the mutant, a slower onset of photosynthesis was mirrored by a decreased capacity to develop NPQ. This correlates with a reduced efficiency to reroute electrons at the PSI reducing side towards cyclic electron flow around PSI and/or other alternative acceptor pools, and with a smaller ability to generate a proton motive force in the light. Altogether, these data illustrate the tight relationship existing between the capacity to evacuate excess electrons accumulated in the intersystem carriers and the capacity to dissipate excess photons during a dark to light transition. These data also underline the essential role of respiration in modulating the photoprotective response in dark-adapted leaves, by poising the cellular redox state. [less ▲]

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See detailStandardized evaluation of protein stability.
Thomas, Annick ULg; Joris, Bernard ULg; Brasseur, Robert ULg

in Biochimica et Biophysica Acta (2010)

We compare Mean Force Potential values of a large series of PDB models of proteins and peptides and find that either as monomers or polymers, proteins longer than 200-250 residues have equivalent MFP ... [more ▼]

We compare Mean Force Potential values of a large series of PDB models of proteins and peptides and find that either as monomers or polymers, proteins longer than 200-250 residues have equivalent MFP values that are averaged to -65+/-3kcal/aa. This value is named the standard or stability value. The standard value is reached irrespective of sequences and 3D folds. Peptides are too short to follow the rule and frequently exist as populations of conformers; one exception are peptides in amyloid fibrils. Fibrils surpass the standard value in accordance with their uppermost stability. In parallel, we calculate median MFP values of amino acids in stably folded PDB models of proteins: median values vary from -25 for Gly to -115kcal/aa for Trp. These median values are used to score primary sequences of proteins: all sequences converge to a mean value of -63.5+/-2.5kcal/aa i.e. only 1.5kcal less than the folded model standard. Sequences from unfolded proteins have lower values. This supports the conclusion that sequences carry in an important message and more specifically that diversity of amino acids in sequences is mandatory for stability. We also use the median amino acid MFP to score residue stability in 3D folds. This demonstrates that 3D folds are compromises between fragments of high and fragments of low scores and that functional residues are often, but not always in the extreme score values. The approach opens to possibilities of evaluating any 3D model, of detecting functional residues and should help in conducting mutation assays. [less ▲]

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See detailRealistic modeling approaches of structure-function properties of CPPs in non-covalent complexes.
Thomas, Annick ULg; Lins, Laurence ULg; Divita, G. et al

in Biochimica et Biophysica Acta (2010)

Transfers of cargoes into cells by means of carrier peptides are multi-steps biological phenomenon the mechanisms of which are unclear. We here discuss bases of realistic in silico molecular modeling ... [more ▼]

Transfers of cargoes into cells by means of carrier peptides are multi-steps biological phenomenon the mechanisms of which are unclear. We here discuss bases of realistic in silico molecular modeling approaches of the formation of non-covalent complexes considering CPPs and cargo diversities. [less ▲]

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See detailAlternative photosynthetic electron flow to oxygen in marine Synechococcus.
Bailey, Shaun; Melis, Anastasios; Mackey, Katherine R M et al

in Biochimica et Biophysica Acta (2008), 1777(3), 269-76

Cyanobacteria dominate the world's oceans where iron is often barely detectable. One manifestation of low iron adaptation in the oligotrophic marine environment is a decrease in levels of iron-rich ... [more ▼]

Cyanobacteria dominate the world's oceans where iron is often barely detectable. One manifestation of low iron adaptation in the oligotrophic marine environment is a decrease in levels of iron-rich photosynthetic components, including the reaction center of photosystem I and the cytochrome b6f complex [R.F. Strzepek and P.J. Harrison, Photosynthetic architecture differs in coastal and oceanic diatoms, Nature 431 (2004) 689-692.]. These thylakoid membrane components have well characterised roles in linear and cyclic photosynthetic electron transport and their low abundance creates potential impediments to photosynthetic function. Here we show that the marine cyanobacterium Synechococcus WH8102 exhibits significant alternative electron flow to O2, a potential adaptation to the low iron environment in oligotrophic oceans. This alternative electron flow appears to extract electrons from the intersystem electron transport chain, prior to photosystem I. Inhibitor studies demonstrate that a propyl gallate-sensitive oxidase mediates this flow of electrons to oxygen, which in turn alleviates excessive photosystem II excitation pressure that can often occur even at relatively low irradiance. These findings are also discussed in the context of satisfying the energetic requirements of the cell when photosystem I abundance is low. [less ▲]

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See detailRelationships between the orientation and the structural properties of peptides and their membrane interactions.
Lins, Laurence ULg; Decaffmeyer, Marc ULg; Thomas, Annick ULg et al

in Biochimica et biophysica acta (2008), 1778(7-8), 1537-44

Physical properties of membranes, such as fluidity, charge or curvature influence their function. Proteins and peptides can modulate those properties and conversely, the lipids can affect the activity and ... [more ▼]

Physical properties of membranes, such as fluidity, charge or curvature influence their function. Proteins and peptides can modulate those properties and conversely, the lipids can affect the activity and/or the structure of the former. Tilted peptides are short hydrophobic protein fragments characterized by an asymmetric distribution of their hydrophobic residues when helical. They were detected in viral fusion proteins and in proteins involved in different biological processes that need membrane destabilization. Those peptides and non lamellar lipids such as PE or PA appear to cooperate in the lipid destabilization process by enhancing the formation of negatively-curved domains. Such highly bent lipidic structures could favour the formation of the viral fusion pore intermediates or that of toroidal pores. Structural flexibility appears as another crucial property for the interaction of peptides with membranes. Computational analysis on another kind of lipid-interacting peptides, i.e. cell penetrating peptides (CPP) suggests that peptides being conformationally polymorphic should be more prone to traverse the bilayer. Future investigations on the structural intrinsic properties of tilted peptides and the influence of CPP on the bilayer organization using the techniques described in this chapter should help to further understand the molecular determinants of the peptide/lipid inter-relationships. [less ▲]

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See detailCold adaptation of enzymes: structural, kinetic and microcalorimetric characterizations of an aminopeptidase from the Arctic psychrophile Colwellia psychrerythraea and of human leukotriene A(4) hydrolase
Huston, A. L.; Haeggstrom, J. Z.; Feller, Georges ULg

in Biochimica et Biophysica Acta (2008), 1784(11), 1865-72

The relationships between structure, activity, stability and flexibility of a cold-adapted aminopeptidase produced by a psychrophilic marine bacterium have been investigated in comparison with a ... [more ▼]

The relationships between structure, activity, stability and flexibility of a cold-adapted aminopeptidase produced by a psychrophilic marine bacterium have been investigated in comparison with a mesophilic structural and functional human homolog. Differential scanning calorimetry, fluorescence monitoring of thermal- and guanidine hydrochloride-induced unfolding and fluorescence quenching were used to show that the cold-adapted enzyme is characterized by a high activity at low temperatures, a low structural stability versus thermal and chemical denaturants and a greater structural permeability to a quenching agent relative to the mesophilic homolog. These findings support the hypothesis that cold-adapted enzymes maintain their activity at low temperatures as a result of increased global or local structural flexibility, which results in low stability. Analysis of the thermodynamic parameters of irreversible thermal unfolding suggests that entropy-driven factors are responsible for the fast unfolding rate of the cold-adapted aminopeptidase. A reduced number of proline residues, a lower degree of hydrophobic residue burial and a decreased surface accessibility of charged residues may be responsible for this effect. On the other hand, the reduction in enthalpy-driven interactions is the primary determinant of the weak conformational stability. [less ▲]

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See detailThermostability and in vitro digestibility of a purified major allergen 2S albumin (Ses i 1) from white sesame seeds (Sesamum indicum)
Moreno, F. J.; Maldonado-Larrosa, Barbara Maria ULg; Wellner, N. et al

in Biochimica et Biophysica Acta (2005), 1752(2), 142-153

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See detailRGDS and DGEA-induced [Ca2+]i signalling in human dermal fibroblasts.
Mineur, Pierre ULg; Guignandon, A.; Lambert, Charles ULg et al

in Biochimica et Biophysica Acta (2005), 1746(1), 28-37

A pulse of short peptides, RGDS and DGEA in the millimolar range, immediately elicits in normal human fibroblasts a transient increase of intracellular Ca2+ ([Ca2+]i). In the present study, we show that ... [more ▼]

A pulse of short peptides, RGDS and DGEA in the millimolar range, immediately elicits in normal human fibroblasts a transient increase of intracellular Ca2+ ([Ca2+]i). In the present study, we show that this [Ca2+]i occurs in an increasing number of cells as a function of peptides concentration. It is specific of each peptide and inhibited at saturating concentration of the peptide in the culture medium. The [Ca2+]i transient depends on signalling pathways slightly different for DGEA and RGDS involving tyrosine kinase(s) and phosphatase(s), phospholipase C, production of inositol-trisphosphate and release of Ca2+ from the cellular stores. GFOGER, the classical collagen binding peptide of alpha1- alpha2- and alpha11-beta1 integrins, in triple helical or denatured form, does not produce any Ca2+ signal. The [Ca2+]i signalling induced by RGDS and DGEA is inhibited by antibodies against beta1 integrin subunit while that mediated by RGDS is also inhibited by antibodies against the alpha3 integrin. Delay in the acquisition of responsiveness is observed during cell adhesion and spreading on a coat of fibronectin for RGDS or collagen for DGEA or on a coat of the specific integrin-inhibiting antibodies but not by seeding cells on GFOGER or laminin-5. This delay is suppressed specifically by collagenase acting on the collagen coat or trypsin on the fibronectin coat. Our results suggest that free integrins and associated focal complexes generate a Ca2+ signal upon recognition of DGEA and RGDS by different cellular pathways. [less ▲]

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See detailSite-directed mutagenesis studies of the hypoxia-inducible factor-1alpha DNA-binding domain.
Michel, Gaetan; Minet, Emmanuel; Mottet, Denis ULg et al

in Biochimica et Biophysica Acta (2002), 1578(1-3), 73-83

Hypoxia-inducible factor-1 (HIF-1), a heterodimeric transcription factor, is activated when cells are exposed to hypoxia. It is composed of two subunits, HIF-1alpha and ARNT. When activated, it binds to ... [more ▼]

Hypoxia-inducible factor-1 (HIF-1), a heterodimeric transcription factor, is activated when cells are exposed to hypoxia. It is composed of two subunits, HIF-1alpha and ARNT. When activated, it binds to the hypoxia-responsive element (HRE) and up-regulates the expression of several genes (vascular endothelial growth factor (VEGF), erythropoietin (EPO), enolase, em leader ). By molecular modeling, a 3-D model for the complex between the DNA-binding domain of HIF-1 (bHLH domain) and its consensus DNA sequence has been developed. Specific interactions between three amino acids (Ser22, Ala25, Arg30) of the HIF-1alpha subunit and DNA bases were identified. In order to further investigate the role of these amino acids, we generated four mutants of the HIF-1alpha subunit using site-directed mutagenesis. The activity of each mutant was tested using a reporter gene containing either 6 HRE sequences or the authentic human VEGF promoter. The results show that three mutants, Ala25Ser, Ala26Glu and Arg30Ala, were no longer active in the reporter gene assay. On the other hand, the Ser22Ala mutant increased the reporter gene expression, in normoxia as well as in hypoxia. These results correlate with the ones obtained when the DNA-binding capability of the mutants was assayed by electrophoretic mobility shift assays (EMSA): Arg30Ala and Ala26Glu mutants bind very weakly to HRE while the Ser22Ala mutant has the same binding capacity as the wild-type HIF-1alpha. These results bring new insights on the specificity of the protein/DNA interactions for HIF-1 towards HRE. [less ▲]

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See detailEnzyme Activity Determination on Macromolecular Substrates by Isothermal Titration Calorimetry: Application to Mesophilic and Psychrophilic Chitinases
Lonhienne, T.; Baise, Etienne ULg; Feller, Georges ULg et al

in Biochimica et Biophysica Acta (2001), 1545(1-2), 349-56

Isothermal titration calorimetry has been applied to the determination of the kinetic parameters of chitinases (EC 3.2.1.14) by monitoring the heat released during the hydrolysis of chitin glycosidic ... [more ▼]

Isothermal titration calorimetry has been applied to the determination of the kinetic parameters of chitinases (EC 3.2.1.14) by monitoring the heat released during the hydrolysis of chitin glycosidic bonds. Experiments were carried out using two different macromolecular substrates: a soluble polymer of N-acetylglucosamine and the insoluble chitin from crab shells. Different experimental temperatures were used in order to compare the thermodependence of the activity of two chitinases from the psychrophile Arthrobacter sp. TAD20 and of chitinase A from the mesophile Serratia marcescens. The method allowed to determine unequivocally the catalytic rate constant k(cat), the activation energy (E(a)) and the thermodynamic activation parameters (DeltaG(#), DeltaH(#), DeltaS(#)) of the chitinolytic reaction on the soluble substrate. The catalytic activity has also been determined on insoluble chitin, which displays an effect of substrate saturation by chitinases. On both substrates, the thermodependence of the activity of the psychrophilic chitinases was lower than that observed with the mesophilic counterpart. [less ▲]

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See detailGene structure and promoter function of a teleost ribosomal protein: a tilapia (Oreochromis mossambicus) L18 gene
Molina, Alfredo; Iyengar, Arati; Marins, Luis F. et al

in Biochimica et Biophysica Acta (2001), 1520(3), 195-202

We have cloned and characterized a tilapia (Oreochromis mossambicus) L18 ribosomal protein gene, including the complete transcribed region and 488 bp of upstream regulatory sequences. We have also ... [more ▼]

We have cloned and characterized a tilapia (Oreochromis mossambicus) L18 ribosomal protein gene, including the complete transcribed region and 488 bp of upstream regulatory sequences. We have also isolated two L18 cDNAs from another tilapia (Oreochromis niloticus) with a few conservative nucleotide differences. Our results suggest the presence of two genes in both species. Reporter constructs were tested for transient expression in CV1 cells and in microinjected zebrafish and tilapia embryos. The tilapia L18 promoter was able to drive expression of the reporter gene in all three experiments, with no apparent preference for a particular tissue. The tilapia L18 promoter is therefore likely to be a powerful tool to drive tissue-independent gene expression in fish. [less ▲]

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See detailPsychrophilic Enzymes: Revisiting the Thermodynamic Parameters of Activation May Explain Local Flexibility
Lonhienne, T.; Gerday, Charles ULg; Feller, Georges ULg

in Biochimica et Biophysica Acta (2000), 1543(1), 1-10

Basic theoretical and practical aspects of activation parameters are briefly reviewed in the context of cold-adaptation. In order to reduce the error impact inherent to the transition state theory on the ... [more ▼]

Basic theoretical and practical aspects of activation parameters are briefly reviewed in the context of cold-adaptation. In order to reduce the error impact inherent to the transition state theory on the absolute values of the free energy (DeltaG(#)), enthalpy (DeltaH(#)) and entropy (DeltaS(#)) of activation, it is proposed to compare the variation of these parameters between psychrophilic and mesophilic enzymes, namely Delta(DeltaG(#))(p-m), Delta(DeltaH(#))(p-m) and Delta(DeltaS(#))(p-m). Calculation of these parameters from the available literature shows that the main adaptation of psychrophilic enzymes lies in a significant decrease of DeltaH(#), therefore leading to a higher k(cat), especially at low temperatures. Moreover, in all cases including cold-blooded animals, DeltaS(#) exerts an opposite and negative effect on the gain in k(cat). It is argued that the magnitude of this counter-effect of DeltaS(#) can be reduced by keeping some stable domains, while increasing the flexibility of the structures required to improve catalysis at low temperature, as demonstrated in several cold-active enzymes. This enthalpic-entropic balance provides a new approach explaining the two types of conformational stability detected by recent microcalorimetric experiments on psychrophilic enzymes. [less ▲]

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See detailResistance of Isolated Pulmonary Mitochondria During in Vitro Anoxia/Reoxygenation
Willet, K.; Detry, Olivier ULg; Sluse, Francis ULg

in Biochimica et Biophysica Acta (2000), 1460(2-3), 346-52

The aim of the study was to investigate the effect of in vitro anoxia/reoxygenation on the oxidative phosphorylation of isolated lung mitochondria. Mitochondria were isolated after harvesting from fresh ... [more ▼]

The aim of the study was to investigate the effect of in vitro anoxia/reoxygenation on the oxidative phosphorylation of isolated lung mitochondria. Mitochondria were isolated after harvesting from fresh pig lungs flushed with Euro-Collins solution. Mitochondrial respiratory parameters were determined in isolated mitochondria before anoxia (control), after 5-45 min anoxia followed by 5 min reoxygenation, and after 25 or 40 min of in vitro incubation in order to follow the in vitro aging of mitochondria during respiratory assays. Respiratory parameters measured after anoxia/reoxygenation did not show any oxidative phosphorylation dysfunction, indicating a high resistance of pulmonary mitochondria to in vitro anoxia/reoxygenation (up to 45 min anoxia). These results indicate that mitochondria are not directly responsible of their oxidative phosphorylation damage observed after in vivo ischemia (K. Willet et al., Transplantation 69 (2000) 582) but are a target of others cellular injuries leading to mitochondrial dysfunction in vivo. [less ▲]

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See detailFluorescence, Absorption and Electron Spin Resonance Study of Bacteriochlorin a Incorporation into Membrane Models
Hoebeke, Maryse ULg; Damoiseau, X.; Schuitmaker, H. J. et al

in Biochimica et Biophysica Acta (1999), 1420(1-2), 73-85

Analysis of the bacteriochlorin a absorption spectra suggests the existence of a monomer-dimer equilibrium, particularly intense in phosphate buffer and favored by a decrease of the pH. The dye in ... [more ▼]

Analysis of the bacteriochlorin a absorption spectra suggests the existence of a monomer-dimer equilibrium, particularly intense in phosphate buffer and favored by a decrease of the pH. The dye in methanolic solution is predominantly in monomeric form. Fluorescence and electron spin resonance nitroxide spin labeling measurements indicate that incorporation into the lipid phase of dimyristoyl-L-alpha-phosphatidylcholine liposomes induces dye monomerization. Moreover, the molecules are bound in the external surface of the vesicles and a complete incorporation is ensured by a lipid-to-dye ratio greater than 125. [less ▲]

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See detailCloning of the Rat Brain Cdna Encoding for the Slc-1 G Protein-Coupled Receptor Reveals the Presence of an Intron in the Gene
Lakaye, Bernard ULg; Minet, Arlette ULg; Zorzi, Willy ULg et al

in Biochimica et Biophysica Acta (1998), 1401(2), 216-20

In order to isolate new G protein-coupled receptors expressed in the cerebral cortex, a set of degenerate oligonucleotides corresponding to the third and seventh transmembrane segment were synthetized ... [more ▼]

In order to isolate new G protein-coupled receptors expressed in the cerebral cortex, a set of degenerate oligonucleotides corresponding to the third and seventh transmembrane segment were synthetized. Their use in PCR on rat brain cortex mRNA amplified several cDNA fragments. One of them, a 526 bp sequence, encoded for what was at that time an unknown G protein-coupled receptor. An oligonucleotide derived from the sequence was then used as a probe to isolate the receptor cDNA from a rat brain cDNA library. It encodes for a 353aa protein with seven transmembrane segments, three consensus N-glycosylation sites at the amino terminus and several potential phosphorylation sites in the intracellular loops. This protein shares 91% overall identity with a recently cloned human somatostatin-like receptor of 402aa named SLC-1. This suggests that we have cloned the rat orthologue of the human SLC-1. However, the extracellular N-terminus of the human receptor is 49 amino acids longer and shows 50% identity with the rat one. Because the human sequence was deduced from genomic DNA, we suspected the presence of an intron in the gene. This was confirmed by PCR using primers spanning the intron. On the basis of the sequence of a 128 kb fragment of chromosome 22 encompassing the SLC-1 gene, we were able to deduce a corrected amino acids sequence for the human receptor. So both rat and human SLC-1 receptors are 353aa long, with three consensus N-glycosylation sites. They share 96% identity at the amino acid level and are encoded by a gene containing one intron in the coding sequence. [less ▲]

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