Characterization by electrospray ionization and tandem mass spectrometry of rhamnolipids produced by two Pseudomonas aeruginosa strains isolated from Brazilian crude oil.

In this work, biosurfactants produced by two Pseudomonas aeruginosa strains isolated from Brazilian crude oils were identified by proton nuclear magnetic resonance ((1)H NMR) and further characterized by mass spectrometry (MS) coupled with electrospray ionization (ESI) and tandem mass spectrometry (MS/MS) analysis in positive mode and their surface activities evaluated. Mono-rhamnolipids and di-rhamnolipids were identified for both isolates, but the most abundant were found to be mono-rhamnolipids. The similarity of rhamnolipids produced by the two strains was in good agreement with their surface activities. Both biosurfactants exhibited similar aqueous solution surface tensions, high emulsification indexes and critical micelle concentration values. The results obtained show that ESI-MS and MS/MS analysis alone provide a fast and highly specific characterization of biosurfactants produced by microbial strains.

Perception of tap water risks and quality: a structural equation model approach.

The present study aims to test a model of tap water risk and quality perception. A questionnaire was designed and applied to a convenience sample of 499 people in Portugal. The model includes aesthetic variables (colour, odour, and flavour), contextual indicators and risk perception. Other variables were also considered, including external information, trust in water companies, familiarity with tap water, and past water-related health problems. A behavioural outcome--drinking tap water--was also studied. Due to multivariate non-normality (Mardia's Coefficient (G2,P) = 460.3), the AGLS estimator was used for the structural equation model (SEM). A triangulation approach with multivariate regression analysis was used to explain the use of tap water to drink and to propose a more holistic model that could not be tested using SEM. Results show that perceived water quality is largely influenced by flavour. Other factors, such as perceived risk and contextual indicators, also have a role but their relevance is relatively weak. On the other hand, risk perception seems to be mainly a result of external information, past health problems, and water colour. Finally, the use of tap water to drink at home can be moderately explained and depends mostly on the ability to use alternatives (i.e. bottled water), tap water taste, and perceived risk.

Binding specificity and in vivo targets of the EH domain, a novel protein-protein interaction module.

EH is a recently identified protein-protein interaction domain found in the signal transducers Eps15 and Eps15R and several other proteins of yeast nematode. We show that EH domains from Eps15 and Eps15R bind in vitro to peptides containing an asparagine-proline-phenylalanine (NPF) motif. Direct screening of expression libraries with EH domains yielded a number of putative EH interactors, all of which possessed NPF motifs that were shown to be responsible for the interaction. Among these interactors were the human homolog of NUMB, a developmentally reguated gene of Drosophila, and RAB, the cellular cofactor of the HIV REV protein. We demonstrated coimmunoprecipitation of Eps15 with NUMB and RAB. Finally, in vitro binding of NPF-containing peptides to cellular proteins and EST database screening established the existence of a family of EH-containing proteins in mammals. Based on the characteristics of EH-containing and EH-binding proteins, we propose that EH domains are involved in processes connected with the transport and sorting of molecules within the cell.

Effect of beta-carotene supplementation on indices of colonic cell proliferation.

BACKGROUND: Epidemiologic studies have shown that consuming foods containing beta-carotene is associated with a decreased incidence of colon cancer. The validity of this association has recently been questioned. It is not known if the rate of colonic cell proliferation differs among individuals with or without a history of colonic polyps or cancer and if proliferation changes in response to beta-carotene. PURPOSE: This study was intended to (a) determine whether differences exist in colonic cell proliferation in individuals with and without prior colonic polyps or tumors, (b) demonstrate that beta-carotene accumulates in colonic mucosa following dietary supplementation, and (c) determine whether mucosal beta-carotene accumulation influences colonic cell proliferation. METHODS: Subjects were enrolled in the phase I study from June 1991 until February 1994. The participants included 20 individuals (11 males and nine females, aged 62.3 +/- 8.9 years [means +/- SD]) with normal colons (as judged by recent colonoscopy), 40 (24 males and 16 females, aged 59.6 +/- 10.1 years) with a history of colonic polyp(s), and 41 (30 males and 11 females, aged 67.2 +/- 9.7 years) with prior colon cancer. The subjects in the last two groups consumed either 30 mg of beta-carotene or placebo each morning for 3 months. This dose of beta-carotene has no known toxic effects, but it can increase the serum level by approximately 10-fold. beta-carotene concentration in serum and colonic tissue was quantitated by high-pressure liquid chromatography in samples collected before and after supplementation with beta-carotene or placebo. Cellular proliferation was assessed on the basis of tissue ornithine decarboxylase activity, urinary polyamine excretion, and proliferating cell nuclear antigen expression. The differences in colonic cell proliferation parameters due to beta-carotene supplementation, within and among different groups, were evaluated by the Wilcoxon matched-pairs signed ranked test and the Mann-Whitney test, respectively. All statistical tests were two-sided. RESULTS: Colonic cell proliferation did not differ in samples obtained from individuals with and without prior colonic polyp(s) or cancer. beta-carotene concentrations in serum and colonic tissue were significantly increased in groups receiving beta-carotene (P < .001). However, cell proliferation did not differ, as judged by any of the three measures, among samples from all experimental groups collected before and after supplementation with beta-carotene. CONCLUSIONS: Dietary supplementation with beta-carotene for a period of 3 months does not alter colonic cell proliferation in individuals with a history of colonic polyps or cancer. IMPLICATIONS: The mechanism by which beta-carotene might reduce colon cancer incidence does not appear to involve or result in a change in cell proliferation in the normal colonic mucosa as studied in individuals with a history of colonic polyps or cancer.