Browsing by Author "RODRIGUEZ, M"

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    CLINICAL ISOLATE OF A PORINLESS SALMONELLA-TYPHI RESISTANT TO HIGH-LEVELS OF CHLORAMPHENICOL
    (1990) TORO, CS; LOBOS, SR; CALDERON, I; RODRIGUEZ, M; MORA, GC
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    LIPOPOLYSACCHARIDES OF THIOBACILLUS SPECIES CONTAINING LIPID-A WITH 2,3-DIAMINO-2,3-DIDEOXYGLUCOSE
    (1987) YOKOTA, A; RODRIGUEZ, M; YAMADA, Y; IMAI, K; BOROWIAK, D; MAYER, H
    Lipopolysaccharides were isolated from two strains of Thinobacillus ferrooxidans and one strain each of Thiobacillus thiooxidans, Thiobacillus novellus and Thiobacillus sp. IFO 14570. Neutral sugars, 2-keto-3-deoxyoctonate, fatty acids and the rare 2,3-diamino-2,3-dideoxyglucose were detected in all lipopolysaccharides. Lipopolysaccharides of both T. ferrooxidans strains contained L-glycero-D-manno-heptose, whereas that of T. thiooxidans contained both L-glycero-D-manno-heptose and D-glycero-D-manno-heptose. On the other hand, heptoses were absent in lipopolysaccharides of T. novellus and Thiobacillus sp. IFO 14570. Lipid A of T. ferrooxidans and T. thiooxidans contained both glucosamine and 2,3-diamino-2,3-dideoxyglucose, in contrast, lipid A of T. novellus and the Thiobacillus sp. IFO 14570 most likely contain only 2,3-diamino-2,3-dideoxyglucose as backbone sugar. Deoxycholate polyacrylamide gel electrophoresis revealed S-type character for all lipopolysaccharides studied. The significance of the lipopolysccharide composition for taxonomic and phylogenetic questions with regard to thiobacilli is discussed.
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    THE MAJOR THIOBACILLUS-FERROOXIDANS OUTER-MEMBRANE PROTEIN FORMS LOW CONDUCTANCE ION CHANNELS IN PLANAR LIPID BILAYERS
    (1992) SILVA, M; FERREIRA, A; RODRIGUEZ, M; WOLFF, D
    A protein isolated and purified from the outer membrane of the acidophilic, chemolithotrophic bacterium, Thiobacillus ferrooxidans with an oligomeric molecular weight of 90 000 Da (p90) was incorporated into phosphatidylethanolamine planar lipid bilayers. The protein formed slightly anionic channels in KCl solutions, with a conductance of 25 pS in 100 mM KCl. The current-voltage relationship was linear between +/-60 mV, and the conductance was a saturating function of the salt concentration. These channels fluctuated from a single open to closed state at low potentials, but present flickering activity at higher potentials.
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    THERMAL STUDIES OF METAL POLY(STYRENE-CO-ACRYLONITRILE) .14.
    (TAYLOR & FRANCIS AS, 1994) CARDENAS, G; ACUNA, J; CARBACHO, H; RODRIGUEZ, M; TAGLE, LH
    The thermal stabilities of metal poly(styrene-co-acrylonitrile) has been studied by thermogravimetry (TG) between 278 K and 823 K under nitrogen flow. The kinetic data thus obtained indicate that the thermostabilities decrease in the order: Sn-STAN > Ga-STAN > Ag-STAN > Sb-STAN > Cu-STAN > Pd-STAN > Fe-STAN > Au-STAN > Bi-STAN for high Molecular Weight (HMW) and Ag-STAN > Pd-STAN > Fe-STAN > Ga-STAN > Cu-STAN > Sb-STAN > Sn-STAN > Bi-STAN > Au-STAN for low Molecular Weight (LMW) copolymers. The thermal stability seems to be dependable on the nature of the bond established between the copolymer and the metal. Cu-copolymer exhibits the lowest Ea most probably due to their oxidation potential. On the other hand, Ag-copolymer has the highest Ea and similar to the copolymer (fraction 1). The thermal decomposition temperatures were obtained from the DTG curves. The reaction order for the thermal decomposition of these copolymers is zero. In other words, we are dealing with a single step decomposition mechanism. The pre-exponential factor, the reaction order, the decomposition temperature and the activation energy of the decomposition for metal poly(styrene-co-acrylonitrile) have been determined.