170 research outputs found
Teste de Morisky-Green e Brief Medication Questionnaire para avaliar adesão a medicamentos
Shear bond strength and debonding characteristics of a new premixed self-etching with a reference total-etch adhesive
Mutant generation by allelic exchange and genome resequencing of the biobutanol organism Clostridium acetobutylicum ATCC 824
Quantitative proteomic analysis of the influence of lignin on biofuel production by Clostridium acetobutylicum ATCC 824
Background: Clostridium acetobutylicum has been a focus of research because of its ability to produce high-value
compounds that can be used as biofuels. Lignocellulose is a promising feedstock, but the lignin–cellulose–hemicellulose
biomass complex requires chemical pre-treatment to yield fermentable saccharides, including cellulose-derived
cellobiose, prior to bioproduction of acetone–butanol–ethanol (ABE) and hydrogen. Fermentation capability is
limited by lignin and thus process optimization requires knowledge of lignin inhibition. The effects of lignin on cellular
metabolism were evaluated for C. acetobutylicum grown on medium containing either cellobiose only or cellobiose
plus lignin. Microscopy, gas chromatography and 8-plex iTRAQ-based quantitative proteomic technologies were
applied to interrogate the effect of lignin on cellular morphology, fermentation and the proteome.
Results: Our results demonstrate that C. acetobutylicum has reduced performance for solvent production when
lignin is present in the medium. Medium supplemented with 1 g L−1
of lignin led to delay and decreased solvents
production (ethanol; 0.47 g L−1
for cellobiose and 0.27 g L−1
for cellobiose plus lignin and butanol; 0.13 g L−1
for cellobiose
and 0.04 g L−1
for cellobiose plus lignin) at 20 and 48 h, respectively, resulting in the accumulation of acetic
acid and butyric acid. Of 583 identified proteins (FDR < 1 %), 328 proteins were quantified with at least two unique
peptides. Up- or down-regulation of protein expression was determined by comparison of exponential and stationary
phases of cellobiose in the presence and absence of lignin. Of relevance, glycolysis and fermentative pathways were
mostly down-regulated, during exponential and stationary growth phases in presence of lignin. Moreover, proteins
involved in DNA repair, transcription/translation and GTP/ATP-dependent activities were also significantly affected
and these changes were associated with altered cell morphology.
Conclusions: This is the first comprehensive analysis of the cellular responses of C. acetobutylicum to lignin at metabolic
and physiological levels. These data will enable targeted metabolic engineering strategies to optimize biofuel
production from biomass by overcoming limitations imposed by the presence of lignin
Epigenetic regulation of centromeric chromatin: old dogs, new tricks?
The assembly of just a single kinetochore at the centromere of each sister chromatid is essential for accurate chromosome segregation during cell division. Surprisingly, despite their vital function, centromeres show considerable plasticity with respect to their chromosomal locations and activity. The establishment and maintenance of centromeric chromatin, and therefore the location of kinetochores, is epigenetically regulated. The histone H3 variant CENP-A is the key determinant of centromere identity and kinetochore assembly. Recent studies have identified many factors that affect CENP-A localization, but their precise roles in this process are unknown. We build on these advances and on new information about the timing of CENP-A assembly during the cell cycle to propose new models for how centromeric chromatin is established and propagated
Biogenesis and functions of bacterial S-layers.
The outer surface of many archaea and bacteria is coated with a proteinaceous surface layer (known as an S-layer), which is formed by the self-assembly of monomeric proteins into a regularly spaced, two-dimensional array. Bacteria possess dedicated pathways for the secretion and anchoring of the S-layer to the cell wall, and some Gram-positive species have large S-layer-associated gene families. S-layers have important roles in growth and survival, and their many functions include the maintenance of cell integrity, enzyme display and, in pathogens and commensals, interaction with the host and its immune system. In this Review, we discuss our current knowledge of S-layer and related proteins, including their structures, mechanisms of secretion and anchoring and their diverse functions
Measurement of electron antineutrino oscillation based on 1230Â days of operation of the Daya Bay experiment
published_or_final_versio
Improved Search for a Light Sterile Neutrino with the Full Configuration of the Daya Bay Experiment
published_or_final_versio
Improved measurement of the reactor antineutrino flux and spectrum at Daya Bay
published_or_final_versio
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