Substrate specificity of lipase B from Candida antarctica in the synthesis of arylaliphatic glycolipids

Arylaliphatic glycolipids are known for their pharmaceutical and medicinal properties. We found that a great variety of arylaliphatic esters can be synthesized from non-activated substrates like glucose or the natural occurring drug salicin using lipase B from Candida antarctica (CAL-B). However, esters based on aromatic carboxylic acids or unsaturated arylaliphatic acids, like cinnamic acid and its derivatives, which are known to display anticancer activity, could not be obtained. In this work, we performed computer-aided molecular modeling based on data of our work published recently and syntheses of new glycolipids to understand why some substances are accepted by CAL-B while some are not. For this purpose, we investigated the accessibility of the lipase binding site for the arylaliphatic acyl donors as well as the steric interactions between the aglycons of glucosides and the residues of the alcohol binding pocket in order to elucidate potentials and limitations of CAL-B for the synthesis of aromatic glycolipids.     

Estimations of Bacterial Growth Rates in Natural Waters

Specific growth rates as low as 0.005 hr⁻¹ (generation times of 20 to 200 hr) of aquatic bacteria in natural waters have been calculated from significant differences between dilution rates and washout rates in a chemostat. The measured growth rates were affected by the treatment of the water samples (type of sterilization) and by competition with the natural microflora for the unknown growth-limiting substrate.     

Liver Necrosis and Lethal Systemic Inflammation in a Murine Model of Rickettsia typhi Infection: Role of Neutrophils,Macrophages and NK Cells

Rickettsia (R.) typhi is the causative agent of endemic typhus, an emerging febrile disease that is associated with complications such as pneumonia, encephalitis and liver dysfunction. To elucidate how innate immune mechanisms contribute to defense and pathology we here analyzed R. typhi infection of CB17 SCID mice that are congenic to BALB/c mice but lack adaptive immunity. CB17 SCID mice succumbed to R. typhi infection within 21 days and showed high bacterial load in spleen, brain, lung, and liver. Most evident pathological changes in R. typhi-infected CB17 SCID mice were massive liver necrosis and splenomegaly due to the disproportionate accumulation of neutrophils and macrophages (MΦ). Both neutrophils and MΦ infiltrated the liver and harbored R. typhi. Both cell populations expressed iNOS and produced reactive oxygen species (ROS) and, thus, exhibited an inflammatory and bactericidal phenotype. Surprisingly, depletion of neutrophils completely prevented liver necrosis but neither altered bacterial load nor protected CB17 SCID mice from death. Furthermore, the absence of neutrophils had no impact on the overwhelming systemic inflammatory response in these mice. This response was predominantly driven by activated MΦ and NK cells both of which expressed IFNγ and is considered as the reason of death. Finally, we observed that iNOS expression by MΦ and neutrophils did not correlate with R. typhi uptake in vivo. Moreover, we demonstrate that MΦ hardly respond to R. typhi in vitro. These findings indicate that R. typhi enters MΦ and also neutrophils unrecognized and that activation of these cells is mediated by other mechanisms in the context of tissue damage in vivo.     

Accumulation of Hydroxycoumarins During Post-harvest Deterioration of Tuberous Roots of Cassava (Manihot esculenta Crantz)

The use of the root crop Cassava (Manihot esculenta Crantz)is constrained by its rapid deterioration after harvest. Chemicaland spectroscopic examination revealed the accumulation of fourhydroxycoumarins (esculin, esculetin, scopolin and scopoletin),compounds derived from the phenylpropanoid pathway, during thetime course of post-harvest deterioration. Fluorescence-microscopyrevealed their localization in the apoplast of the parenchyma.Scopoletin and scopolin showed the most dramatic increases inconcentration, peaking by day 2 after harvesting. A smallersecondary peak of scopoletin tended to be more pronounced incultivars showing lower susceptibility to deterioration. Evidencefor the metabolism of scopoletin to an insoluble coloured productby means of a peroxidase is presented. This product may be thecause of the discolouration of the vascular tissue during storage.Copyright 2000 Annals of Botany Company Cassava, hydroxycoumarins, Manihot esculenta, peroxidases, post-harvest physiological deterioration, wound response     

Immunological evidence for a ribulose bisphosphate carboxylase-like protein in the symbiotic dinoflagellate Symbiodinium sp.

Whereas previously there has been no convincing evidence for ribulose bisphosphate carboxylase in dinoflagellates, a strong and highly specific reaction was observed when antibodies to the denatured large subunit of the (silver beet) protein were used to probe Western blots of whole soluble fractions of various Symbiodinium isolates. No reaction was observed using extracts from Symbiodinium isolated from a host which had been maintained under low light intensity. The results imply extensive sequence homology between the large subunit of ribulose bisphosphate carboxylase and a dinoflagellate protein of M , approximately 35 000.