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- Graneli, Annette, 1973, et al.
(författare)
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Long-distance lateral diffusion of human Rad51 on double-stranded DNA
- 2006
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Ingår i: Proc Natl Acad Sci U S A. ; 103:5, s. 1221-6
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Tidskriftsartikel (refereegranskat)abstract
- Rad51 is the primary eukaryotic recombinase responsible for initiating DNA strand exchange during homologous recombination. Although the subject of intense study for over a decade, many molecular details of the reactions promoted by Rad51 and related recombinases remain unknown. Using total internal reflection fluorescence microscopy, we directly visualized the behavior of individual Rad51 complexes on double-stranded DNA (dsDNA) molecules suspended in an extended configuration above a lipid bilayer. Here we show that complexes of Rad51 can bind to and slide freely along the helical axis of dsDNA. Sliding is bidirectional, does not require ATP hydrolysis, and displays properties consistent with a 1D random walk driven solely by thermal diffusion. The proteins move freely on the DNA for long periods of time; however, sliding terminates and the proteins become immobile upon encountering the free end of a linear dsDNA molecule. This study provides previously uncharacterized insights into the behaviors of human Rad51, which may apply to other members of the RecA-like family of recombinases.
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| 4. |
- Graneli, Annette, 1973, et al.
(författare)
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Organized arrays of individual DNA molecules tethered to supported lipid bilayers
- 2006
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Ingår i: Langmuir. ; 22:1, s. 292-9
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Tidskriftsartikel (refereegranskat)abstract
- An unappreciated aspect of many single-molecule techniques is the need for an inert surface to which individual molecules can be anchored without compromising their biological integrity. Here, we present new methods for tethering large DNA molecules to the surface of a microfluidic sample chamber that has been rendered inert by the deposition of a supported lipid bilayer. These methods take advantage of the "bio-friendly" environment provided by zwitterionic lipids, but still allow the DNA molecules to be anchored at fixed positions on the surface. We also demonstrate a new method for constructing parallel arrays of individual DNA molecules assembled at defined positions on a bilayer-coated, fused silica surface. By using total internal reflection fluorescence microscopy to visualize the arrays, it is possible to simultaneously monitor hundreds of aligned DNA molecules within a single field-of-view. These molecular arrays will significantly increase the throughput capacity of single-molecule, fluorescence-based detection methods by allowing parallel processing of multiple individual reaction trajectories.
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- Abreu, PC, et al.
(författare)
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Eutrophication processes and trophic interactions in a shallow estuary: Preliminary results based on stable isotope analysis (delta C-13 and delta N-15)
- 2006
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Ingår i: Estuaries and Coasts. - 1559-2731. ; 29:2, s. 277-285
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Tidskriftsartikel (refereegranskat)abstract
- Stable isotopes ratios (delta C-13 and delta N-15) were measured in primary producers and consumers of two bays with contrasting eutrophic conditions in the pains Lagoon estuary, southern Brazil: the Justino bay, a more pristine ecosystem, and the Mangueira bay, a heavily polluted region that receives the Rio Grande city sewage and effluents of several industries. delta C-13 values of organisms collected in both subsystems were not different, but delta N-15 values had significant statistical differences, ca. 3.5 parts per thousand higher in the Mangueira bay. It is likely that primary producers and consumers in this subsystem are greatly influenced by higher nitrogen input due to domestic and industrial sewages. The stable isotope analysis also corroborated several trophic interactions previously established by gut content analysis, and due to its higher sensitivity, it was possible to better determine the contributions of different primary producers and detrital fractions to the consumers' diets. It was confirmed that plant detritus represents the main food source for most organisms. The stable isotope analysis also demonstrated that detritivorous benthic organisms in the same habitat have distinct diet compositions, with differential consumption of C3 and C4 plants. This technique showed that some consumers that eat detritus do not have in their stable isotopic signature any relationship with that of plants. It is likely that these consumers assimilate their carbon and nitrogen from other sources like microalgae or microorganisms that colonize decaying plants.
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- Abreu, Paulo Cesar, et al.
(författare)
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Importance of biofilm as food source for shrimps (Farafantepenaeus paulensis) evaluated by stable isotopes (∂13C and ∂15N)
- 2007
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 347:1-2, s. 88-96
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Tidskriftsartikel (refereegranskat)abstract
- Abstract The contribution of biofilm and artificial feeds for the growth of the pink shrimp Farfantepenaeus paulensis reared in tanks and net cages were evaluated by using stable isotope (δ13C and δ15N) analysis. In the net cage experiment, mass balance and mixing equations showed that the biofilm contribution to shrimp growth was over 49% of carbon and 70% of nitrogen. These data suggest that the artificial feed offered in this experiment, although ingested, was not properly incorporated in the shrimp tissue. In contrast, biofilm growing in tanks contributed little to the nitrogen incorporated by the shrimp (maximum of 29%). In this experiment, shrimp presented an unusually large isotope fractionation. These results imply that the shrimp are selectively ingesting some items from the biofilm, or differentially assimilate specific items of the artificial feed, due to differential digestibility. The hypothesis of selective feeding of biofilm microorganisms was corroborated in the experiment with net cages, where shrimp preferentially consumed centric diatoms. This study also demonstrated that shrimp biofilm consumption and the presence of artificial feed largely influenced biofilm formation. The consumption of centric diatoms by shrimp seem to stimulate biofilm chlorophyll-a, while biofilm δ15N values measured in tanks indicate that microorganisms present in the biofilm absorbs nitrogen released by artificial feed after its decomposition.
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- Anesio, Alexandre M, et al.
(författare)
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Decreased bacterial growth on vascular plant detritus due to photochemical modification
- 1999
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Ingår i: AQUATIC MICROBIAL ECOLOGY. - 0948-3055. ; 17:2, s. 159-165
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the effects of UV radiation on abiotic decomposition and dissolution of leaf Litter from the aquatic macrophyte Phragmites australis. Dead leaves were autoclaved and incubated in quartz tubes with autoclaved Milli-Q water, in darkness, und
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- Anesio, Alexandre Magno, et al.
(författare)
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Influence of humic substances on bacterial and viral dynamics in freshwaters
- 2004
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Ingår i: Applied and Environmental Microbiology. - 0099-2240. ; 70:8, s. 4848-4854
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial and viral abundances were measured in 24 lakes with dissolved organic carbon (DOC) concentrations ranging from 3 to 19 mg of C liter(-1). In addition, a laboratory experiment was performed to test the effects of different sources of carbon (i.e., glucose and fulvic acids) and nutrients on the dynamics of viruses and bacteria. In the lake survey, no correlation was found between virus abundance and DOC concentration, yet there was a significant positive correlation between bacterial abundance and DOC concentration. A negative correlation was found between the virus-to-bacteria ratio and DOC level. These results are in agreement with our findings in the laboratory, where virus counts were significantly lower in treatments with fulvic acid additions than in a control (mean, 67.4% +/- 6.5% of the control). Virus counts did not differ significantly among the control and treatments with glucose, indicating that it was the type of organic carbon and not quantity which had an impact on viruses. Results from this study suggest that the way viruses control bacterial assemblages in humic lakes is different from the mechanism in clear water systems.
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