Theory of protein folding

Protein folding should be complex. Proteins organize themselves into specific three-dimensional structures, through a myriad of conformational changes. The classical view of protein folding describes this process as a nearly sequential series of discrete intermediates. In contrast, the energy landscape theory of folding considers folding as the progressive organization of an ensemble of partially folded structures through which the protein passes on its way to the natively folded structure. As a result of evolution, proteins have a rugged funnel-like landscape biased toward the native structure. Connecting theory and simulations of minimalist models with experiments has completely revolutionized our understanding of the underlying mechanisms that control protein folding.     

Stereoselective convergent synthesis of 24-substituted metabolites and analogues of vitamin D

The synthesis of vitamin D(3) active metabolites [24R,25-(OH)(2)-D(3), 24S,25-(OH)(2)-D(3) and 1alpha,24R,25-(OH)(3)-D(3)] and the first 24-aminovitamin D(3) derivatives [24S-benzoylamino-25-OH-D(3) and 24S-benzoylamino-1alpha,25-(OH)(2)-D(3)] are reported. The stereogenic center at C-24 was generated through ultrasonically induced aqueous conjugate addition of iodide 8 to dioxolanone 6 or oxazolidinone 7. The vitamin D triene system was constructed using the Lythgoe approach. The synthetic route, which is both short (6 or 7 steps from iodide 8) and efficient (32-45% overall yield), constitutes a practical method for the preparation of 24-functionalized metabolites and analogues of vitamin D(3). The ultrasonically induced conjugate addition in the key step provides a novel example of a highly stereoselective reaction promoted by the zinc-copper couple in aqueous media.     

Biogeographic patterns, β-diversity and dominance in the cerrado biome of Brazil

From a total woody flora of ca. 1000 species, a suite of 121 species forms an oligarchy dominating the cerrado biome. This mirrors patterns of dominance described in western Amazonian rain forests. Widespread sampling shows that across the biome this suite of species contributes on average 66% of the total species composition, and 75% of the total Importance Value Index in cerrado communities. An analysis of the floristic similarity between six cerrado phytogeographic provinces (southern, central and south-eastern, central-western, far-western, north-eastern, disjunct Amazonian) reveals great heterogeneity within the biome, principally of the less common species. Of the 951 species recorded from 375 floristic surveys across the biome, 494 species (more than half of the total) are found in only one of the provinces, with very few species (37, i.e., 3.9%) found in all six provinces. Each of the provinces contains a significant number of species which are apparently confined to it, ranging from 15 species (1.6% of the total woody cerrado flora) in the far-western province (primarily in the state of Rondônia) to 162 species (17%) in the central-western province. At the local level, floristic similarity can be very high. An analysis of the floristic composition of 13 sites within the Federal District shows a woody flora of 236 species, indicating that 25% of the total woody flora of the cerrado biome is represented in 0.3% of its area, illustrating the great conservation importance of this region. Floristic similarity between sites within the Federal District is high, although much of this similarity is accounted for by oligarch species which account for between 59 and 89% of total species recorded per site. Informed conservation judgements within the cerrado need to take account of regional floristic patterns to ensure maximum protection of biodiversity, as the majority of species are not geographically widespread within the biome.     

Arabidopsis ALF4 encodes a nuclear-localized protein required for lateral root formation

Lateral root formation, the primary way plants increase their root mass, displays developmental plasticity in response to environmental changes. The aberrant lateral root formation (alf)4-1 mutation blocks the initiation of lateral roots, thus greatly altering root system architecture. We have positionally cloned the ALF4 gene and have further characterized its phenotype. The encoded ALF4 protein is conserved among plants and has no similarities to proteins from other kingdoms. The gene is present in a single copy in Arabidopsis. Using translational reporters for ALF4 gene expression, we have determined that the ALF4 protein is nuclear localized and that the gene is expressed in most plant tissues; however, ALF4 expression and ALF4's subcellular location are not regulated by auxin. These findings taken together with further genetic and phenotypic characterization of the alf4-1 mutant suggest that ALF4 functions independent from auxin signaling and instead functions in maintaining the pericycle in the mitotically competent state needed for lateral root formation. Our results provide genetic evidence that the pericycle shares properties with meristems and that this tissue plays a central role in creating the developmental plasticity needed for root system development.     

Characterization of the First VanB Vancomycin-Resistant <Emphasis Type="Italic">Enterococcus faecium</Emphasis> Isolated in a Spanish Hospital

We report the detection and characterization of the first vancomycin-resistant VanB-type Enterococcus faecium to be isolated in a Spanish hospital. Sequence analysis of the vanB gene showed that this isolate belonged to subtype vanB2. Moreover, PCR amplification analysis indicated that the vanB gene cluster was linked to a Tn5382-like transposon.     

Bone marrow stromal cells improve cardiac performance in healed infarcted rat hearts

Postinfarct congestive heart failure is one of the leading causes of morbidity and mortality in developed and developing countries. The main purpose of this study was to investigate whether transplantation of bone marrow stromal cells (BMSC) directly into the myocardium could improve the performance of healed infarcted rat hearts. Cell culture medium with or without BMSC was injected into borders of cardiac scar tissue 4 wk after experimental infarction. Cardiac performance was evaluated 2 wk after cellular (n = 10) or medium (n = 10) injection by electro- and echocardiography. Histological study was performed 3 wk after treatment. Electrocardiography of BMSC-treated infarcted rats showed electrical and mechanical parameters more similar to those in control than in medium-treated animals: a normal frontal QRS axis in 6 of 10 BMSC-treated and all control rats and a rightward deviation of the QRS axis in all 10 medium-treated animals. BMSC treatment, assessed by echocardiography, improved fractional shortening (39.00 +/- 4.03%) compared with medium-treated hearts (18.20 +/- 0.74%) and prevented additional changes in cardiac geometry. Immunofluorescence microscopy revealed colocalization of 4',6-diamidino-2-phenylindole-labeled nuclei of transplanted cells with cytoskeletal markers for cardiomyocytes and smooth muscle cells, indicating regeneration of damaged myocardium and angiogenesis. These data provide strong evidence that BMSC implantation can improve cardiac performance in healed infarctions and open new promising therapeutic opportunities for patients with postinfarction heart failure.     

Remodeling of resistance arteries in organoid culture is modulated by pressure and pressure pulsation and depends on vasomotion

The hypothesis was tested that pressure and pressure pulsation modulate vascular remodeling. Arterioles ( approximately 200 microm lumen diameter) were dissected from rat cremaster muscle and studied in organoid culture. In the first series, arterioles were kept at a stable pressure level of either 50 or 100 mmHg for 3 days. Both groups showed a progressive increase in myogenic tone during the experiment. Arterioles kept at 50 mmHg showed larger endothelium-dependent dilation, compared with vessels kept at 100 mmHg on day 3. Remodeling, as indicated by the reduction in maximally dilated diameter at 100 mmHg, was larger in arterioles kept at 50 mmHg compared with 100 mmHg: 34 +/- 4.5 versus 10 +/- 4.8 microm (P < 0.05). In the second series, arterioles were subjected to a stable pressure of 60 mmHg or oscillating pressure of 60 +/- 10 mmHg (1.5 Hz) for 4 days. Pressure pulsation induced partial dilation and was associated with less remodeling: 34 +/- 4.0 versus 19 +/- 4.5 microm (P < 0.01) for stable pressure versus oscillating pressure. Vasomotion was frequently observed in all groups, and inward remodeling was larger in vessels with vasomotion: 30 +/- 2.5 microm compared with vessels that did not exhibit vasomotion: 8.0 +/- 5.0 microm (P < 0.01). In conclusion, these results indicate that remodeling is not enhanced by high pressure. Pressure pulsation causes partial dilation and reduces inward remodeling. The appearance of vasomotion is associated with enhanced inward remodeling.     

The pathogen Mycobacterium marinum, a faster growing close relative of Mycobacterium tuberculosis, has a single rRNA operon per genome

Although Mycobacterium marinum and Mycobacterium tuberculosis are very closely related they differ significantly in their growth rates. The Type strain of M. marinum and one clinical isolate were investigated and, like M. tuberculosis, were found to have a single rRNA (rrn) operon per genome located downstream from murA gene and controlled by two promoters. No sequence differences were found that account for the difference in the growth rates of the two species. We infer that M. tuberculosis has the capacity to synthesize rRNA much faster than it actually does; and propose that the high number of insertion sequences in this species attenuate growth rate to lower values.