Selective antibacterial activity of the cationic peptide PaDBS1R6 against Gram-negative bacteria

Infections caused by Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa foremost among them, constitute a major worldwide health problem. Bioinformatics methodologies are being used to rationally design new antimicrobial peptides, a potential alternative for treating these infections. One of the algorithms used to develop antimicrobial peptides is the Joker, which was used to design the peptide PaDBS1R6. This study evaluates the antibacterial activities of PaDBS1R6 in vitro and in vivo, characterizes the peptide interaction to target membranes, and investigates the PaDBS1R6 structure in contact with mimetic vesicles. Moreover, we demonstrate that PaDBS1R6 exhibits selective antimicrobial activity against Gram-negative bacteria. In the presence of negatively charged and zwitterionic lipids the structural arrangement of PaDBS1R6 transits from random coil to α-helix, as characterized by circular dichroism. The tertiary structure of PaDBS1R6 was determined by NMR in zwitterionic dodecylphosphocholine (DPC) micelles. In conclusion, PaDBS1R6 is a candidate for the treatment of nosocomial infections caused by Gram-negative bacteria, as template for producing other antimicrobial agents.     

Deep Crustal Communities of the Juan de Fuca Ridge Are Governed by Mineralogy

Volcanic ocean crust contains a global chemosynthetic microbial ecosystem that impacts ocean productivity, seawater chemistry and geochemical cycling. We examined the mineralogical effect on community structure in the aquifer ecosystem by using a four-year in situ colonization experiment with igneous minerals and glasses in Integrated Ocean Drilling Program Hole 1301A on the Juan de Fuca Ridge. Microbial community analysis and scanning electron microscopy revealed that olivine phases and iron-bearing minerals bore communities that were distinct from iron-poor phases. Communities were dominated by Archaeoglobaceae, Clostridia, Thermosipho, Desulforudis and OP1 lineages. Our results suggest that mineralogy determines microbial composition in the subseafloor aquifer ecosystem.     

Selection and structural analysis of de novo proteins from an α3β3 genetic library

The construction of novel functional proteins has been a key area of protein engineering. However, there are few reports of functional proteins constructed from artificial scaffolds. Here, we have constructed a genetic library encoding α3β3 de novo proteins to generate novel scaffolds in smaller size using a binary combination of simplified hydrophobic and hydrophilic amino acid sets. To screen for folded de novo proteins, we used a GFP‐based screening system and successfully obtained the proteins from the colonies emitting the very bright fluorescence as a similar intensity of GFP. Proteins isolated from the very bright colonies (vTAJ) and bright colonies (wTAJ) were analyzed by circular dichroism (CD), 8‐anilino‐1‐naphthalenesulfonate (ANS) binding assay, and analytical size‐exclusion chromatography (SEC). CD studies revealed that vTAJ and wTAJ proteins had both α‐helix and β‐sheet structures with thermal stabilities. Moreover, the selected proteins demonstrated a variety of association states existing as monomer, dimer, and oligomer formation. The SEC and ANS binding assays revealed that vTAJ proteins tend to be a characteristic of the folded protein, but not in a molten‐globule state. A vTAJ protein, vTAJ13, which has a packed globular structure and exists as a monomer, was further analyzed by nuclear magnetic resonance. NOE connectivities between backbone signals of vTAJ13 suggested that the protein contains three α‐helices and three β‐strands as intended by its design. Thus, it would appear that artificially generated α3β3 de novo proteins isolated from very bright colonies using the GFP fusion system exhibit excellent properties similar to folded proteins and would be available as artificial scaffolds to generate functional proteins with catalytic and ligand binding properties.     

RNA翻译的复杂性：不翻译、部分翻译、从头翻译及过度翻译

经典分子生物学的中心法则描述了遗传信息的传递方向.中心法则认为RNA只有通过翻译产生蛋白质才在生命活动中发挥功能.但是随着分子生物学的发展,很多RNA其本身就可以承担生命学功能.而且RNA的形式也不仅仅只有线性这一种.本文总结了RNA转录后命运的4种形式:不翻译、部分翻译、从头翻译和过度翻译.RNA命运的多样性使得对于翻译的理解比经典的中心法则规定的内容将更加丰富、复杂.充分了解RNA转录后的命运,对以后研究RNA的功能提出了更高的要求,也为我们真正而全面地了解RNA的功能提供了可能.     

The Expression of Connexins and SOX2 Reflects the Plasticity of Glioma Stem-Like Cells

Glioblastoma (GBM) is the most malignant primary brain tumor, with an average survival rate of 15 months. GBM is highly refractory to therapy, and such unresponsiveness is due, primarily, but not exclusively, to the glioma stem-like cells (GSCs). This subpopulation express stem-like cell markers and is responsible for the heterogeneity of GBM, generating multiple differentiated cell phenotypes. However, how GBMs maintain the balance between stem and non-stem populations is still poorly understood. We investigated the GBM ability to interconvert between stem and non-stem states through the evaluation of the expression of specific stem cell markers as well as cell communication proteins. We evaluated the molecular and phenotypic characteristics of GSCs derived from differentiated GBM cell lines by comparing their stem-like cell properties and expression of connexins. We showed that non-GSCs as well as GSCs can undergo successive cycles of gain and loss of stem properties, demonstrating a bidirectional cellular plasticity model that is accompanied by changes on connexins expression. Our findings indicate that the interconversion between non-GSCs and GSCs can be modulated by extracellular factors culminating on differential expression of stem-like cell markers and cell-cell communication proteins. Ultimately, we observed that stem markers are mostly expressed on GBMs rather than on low-grade astrocytomas, suggesting that the presence of GSCs is a feature of high-grade gliomas. Together, our data demonstrate the utmost importance of the understanding of stem cell plasticity properties in a way to a step closer to new strategic approaches to potentially eliminate GSCs and, hopefully, prevent tumor recurrence.     

基于质谱的BLAST方法在金鱼胚胎蛋白质鉴定中的应用

未知基因组及蛋白质序列数据库有限的物种的蛋白质组学分析是当前一些非模式生物物种蛋白质组学研究领域的瓶颈之一.基于同源性搜索的BLAST方法（MS BLAST）,是近年新发展起来的一种用于未知基因组的蛋白质鉴定的搜索工具,已成功应用于许多未知基因组物种的蛋白质鉴定.SPITC化学辅助方法是本实验室建立的一种改进的de novo质谱测序方法.采用MS BLAST方法对经Mascot软件数据库搜索未能鉴定到的19个金鱼胚胎蛋白质进行鉴定,其中12个蛋白质是直接测序后进行MS BLAST搜索得到的结果,另外7个蛋白质是联合MS BLAST和SPITC衍生方法得到的鉴定结果.实验结果证明,采用MS BLAST方法进行蛋白质的跨物种鉴定具有可行性和可靠性,给蛋白质的跨物种鉴定提供了一条新的途径.     

Theoretical basis for the interpretation of surface permeability data by a transient method

Surface permeability data are frequently required when the system under study consists of a multiple zone membrane. Rotunno et al. (1970) developed a transient method to determine surface permeabilities in which the solute from one compartment is fully absorbed by the membrane without being transferred to the other. The theoretical analysis of the various possible situations is presented here to show that: (1) a linear plot of uptake vs. contact time can be expected for the most simple case (quasi-steady state in the external zone) even in the presence of considerable boundary layer resistance, and (2) a linear display of experimental data is not exclusive for that case, but it can also occur in the more complex situation of a composite resistance of a semi-infinite medium plus boundary layer. On this basis, different alternatives to interpret the data are suggested, according to the physical situation and the equations developed for each case.     

La evaluación de la calidad de vida en personas con demencia

Quality of life (QoL) is one of the most important outcome variables in the study of the efficacy of interventions with people with dementia. However, its assessment is difficult 1) because it is a complex construct for which there is no unified theoretical or conceptual approach, and 2) because of the inherent difficulties in the cognitive impairments of the people under study. In this work different methods and instruments to this end are reviewed, and related findings are discussed. It is important to take into account the subjective view of the assessed person, as assessments done by proxies tend to underestimate QoL. In spite of the need for further development in this field, it is concluded that the instrument of choice is the QOL-AD, as it is change-sensitive, it correlates with health measurements, it is translated into several languages and it can be administered to people with low MMSE scores.