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S Claveau

Publications and source records attributed to S Claveau.

7 recordsLinked to original sources
PubMed2005

AZT binding to Na,K-ATPase.

3'-azido-3'-deoxythymidine (AZT) is the first effective drug used clinically for the treatment of human immunodeficiency virus (HIV) infection. The drug interactions with DNA and protein are associated with its mechanism of action in vivo. This study was designed to examine the interaction of AZT with the Na,K-dependent adenosine triphosphatase (Na,K-ATPase) in H2O and D2O solutions at physiological pH using drug concentration of 0.1 microM to 1 mM and final protein concentration of 0.5 to 1 mg/mL. Ultraviolet absorption and Fourier transform infrared difference spectroscopy with its self-deconvolution, second-derivative resolution enhancement, and curve-fitting procedures were used to characterize the drug-binding mode, the drug-binding constant, and the effects of drug interaction on the protein secondary structure. Spectroscopic evidence showed that at low drug concentration (0.1 microM), AZT binds (H-bonding) mainly to the polypeptide C=O and C-N groups with two binding constants of K1 = 5.3 x 10(5) M(-1) and K2 = 9.8 x 10(3) M(-1). As drug content increased, AZT-lipid complex prevailed. At a high drug concentration (1 mM), drug binding resulted in minor protein secondary structural changes from that of the alpha-helix 19.8%; beta-pleated 25.6%; turn 9.1%; beta-antiparallel 7.5% and random 38%, in the free Na,K-ATPase to that of the alpha-helix 19%; beta-pleated 21.1%; turn 10.1%; beta-antiparallel 8.8% and random 41%, in the AZT-ATPase complexes.

Antiviral Agents↗
PubMed2004

Alcohol-mediated error-prone PCR.

The effect of urea, isopropanol, propan-1-ol, and butan-1-ol on PCR using three different DNA polymerases was investigated. In the presence of these agents, polymerases were active as expected up to a critical concentration where they became progressively inhibited. Critical concentrations of alcohols generally increased with thermoresistance of the polymerases and decreased with the hydrophobicity of the alcohols. These results indicate that an important aspect of the inhibition involved conformational loosening due to a decrease in the hydrophobic effect. A mutagenic effect occurred with Vent(r) (exo-) DNA polymerase in the presence of 7.0 to 8.0% v/v propan-1-ol, affording mutation frequencies of up to 9.8 x 10(-3) mutation/bp/PCR. Under these conditions the preferential replacement of Gs and Cs was observed, in opposition to standard error-prone PCR that favors replacement of As and Ts. Comparison of various PCR conditions indicates that propanol and MnCl2 have different modes of action, and that the decrease in fidelity promoted by propanol is due to a finely tuned partial destabilization of the polymerase. The PCR conditions developed in this study provide a useful alternative for targeting different sequence space for directed evolution experiments.

1-Propanol↗
PubMed2004

Single-point mutations at the surface of MB-1Trp lead to important changes in its conformational properties.

Protein design is currently used for the creation of new proteins with desirable traits. In our lab we focus on the synthesis of proteins with high essential amino acid content having potential applications in animal nutrition. One of the limitations we face in this endeavour is achieving stable proteins despite a highly biased amino acid content. We report here the synthesis and the characterization of three variants of MB-1Trp in which two solvent-exposed Leu have been replaced by Glu allowing for the formation of new salt bridges at the surface of the protein. Although both mutations were expected to be similar (i.e. same mutation in a comparable local environment), they appear to have different effects on MB-1Trp as shown by far-UV circular dichroism, thermal denaturation, fluorescence and proteolytic resistance measurements. For the mutation Leu68Glu, an increase in the protein melting temperature of 6 degrees C was observed. Surprisingly, the mutation in position Leu19Glu led to a decrease in melting temperature and a modification of tertiary structure.

Amino Acid Substitution↗
PubMed1993

Infection due to Rhizomucor pusillus: report of four cases in patients with leukemia and review.

Rhizomucor pusillus, a thermophilic fungus of the order Mucorales, is a rare cause of human infection. A search of the literature has produced only seven reports describing nine cases of infection caused by this organism. Recently, over a period of 17 months, four cases of R. pusillus infection in patients with leukemia were diagnosed: a cluster of three cases in a Montreal hospital and one isolated case from Quebec City. All four cases were proven both by histopathologic examination and by culture of tissues. In three cases, pulmonary involvement was confirmed following lung surgery, and in one case, disseminated infection was observed at autopsy. All patients received amphotericin B, and two underwent surgical debridement; however, none of the patients survived.

Adolescent↗
PubMed1981

Limited in vitro activity of cefamandole against 100 beta-lactamase- and non-beta-lactamase-producing Haemophilus influenzae strains: comparison of moxalactam, chloramphenicol, and ampicillin.

In the present study, the minimal inhibitory concentrations and minimal bactericidal concentrations of moxalactam, cefamandole lithium, ampicillin, and chloramphenicol were determined, both in broth and on solid medium, against 75 non-beta-lactamase-producing and 25 beta-lactamase-producing strains of Haemophilus influenzae. Most of the 75 strains were inhibited or killed by 2 microgram or less of ampicillin, chloramphenicol, or moxalactam per ml, but cefamandole exhibited poor bactericidal activity against 11 non-beta-lactamase-producing strains, of which 9 were non-type B H. influenzae. Most of the 25 beta-lactamase-producing H. influenzae were resistant to 128 microgram of ampicillin per ml. Both moxalactam and chloramphenicol, which had minimal inhibitory concentrations of less than 0.25 and 2 microgram/ml, respectively, were more active than cefamandole, which had a minimal inhibitory concentration ranging from 2 to greater than or equal to 128 microgram/ml.

Ampicillin↗