Search

The central implication of maximising behaviour amid competition is that rates of return tend toward equality. We test that implication in a market whose participants have the traits that behavioural economics suggests should make it hardest to find evidence of maximisation: the market for panhandling at Metrorail stations in Washington, District of Columbia. We find that stations with more panhandling opportunities attract more panhandlers and that cross-station differences in hourly panhandling receipts are statistically indistinguishable from zero. Panhandling rates of return thus tend toward equality. Extreme ‘behavioural’ traits do not prevent maximisation in this market.

Many techniques for engineering and interrogating three-dimensional (3-D) muscle bundles from animal- or patient-derived myoblasts have recently been developed to overcome the limitations of existing in vitro and in vivo model systems. However, many approaches for engineering 3-D muscle bundles rely on specialized and time-consuming techniques, such as photolithography for fabrication and cryosectioning for histology. Cryosectioning also limits visualization to a single plane instead of the entire 3-D structure. To address these challenges, we first implemented a consumer-grade 3-D-printer to rapidly prototype multiple templates for engineering muscle bundles. We then employed our templates to engineer 3D muscle bundles and identify template geometries that promoted bundle survival over three weeks. Subsequently, we implemented tissue clearing, immunostaining, and confocal imaging to acquire z-stacks of intact muscle bundles labelled for myogenic markers. With this approach, we could select the imaging plane on-demand and visualize the intact 3-D structure of bundles. However, tissue clearing did cause some tissue degradation that should be considered. Together, these advances in muscle tissue engineering and imaging will accelerate the use of these 3-D tissue platforms for disease modeling and therapeutic discovery.

Disruption in copper homeostasis causes a number of cognitive and motor deficits. Wilson's disease and Menkes disease are neurodevelopmental disorders resulting from mutations in the copper transporters ATP7A and ATP7B, with ATP7A mutations also causing occipital horn syndrome, and distal motor neuropathy. A 65 year old male presenting with brachial amyotrophic diplegia and diagnosed with amyotrophic lateral sclerosis (ALS) was found to harbor a p.Met1311Val (M1311V) substitution variant in ATP7A. ALS is a fatal neurodegenerative disease associated with progressive muscle weakness, synaptic deficits and degeneration of upper and lower motor neurons. To investigate the potential contribution of the ATP7AM1311V variant to neurodegeneration, we obtained and characterized both patient-derived fibroblasts and patient-derived induced pluripotent stem cells differentiated into motor neurons (iPSC-MNs), and compared them to control cell lines. We found reduced localization of ATP7AM1311V to the trans-Golgi network (TGN) at basal copper levels in patient-derived fibroblasts and iPSC-MNs. In addition, redistribution of ATP7AM1311V out of the TGN in response to increased extracellular copper was defective in patient fibroblasts. This manifested in enhanced intracellular copper accumulation and reduced survival of ATP7AM1311V fibroblasts. iPSC-MNs harboring the ATP7AM1311V variant showed decreased dendritic complexity, aberrant spontaneous firing, and decreased survival. Finally, expression of the ATP7AM1311V variant in Drosophila motor neurons resulted in motor deficits. Apilimod, a drug that targets vesicular transport and recently shown to enhance survival of C9orf72-ALS/FTD iPSC-MNs, also increased survival of ATP7AM1311V iPSC-MNs and reduced motor deficits in Drosophila expressing ATP7AM1311V. Taken together, these observations suggest that ATP7AM1311V negatively impacts its role as a copper transporter and impairs several aspects of motor neuron function and morphology.

Amyotrophic lateral sclerosis (ALS) is a fatal and progressive neurodegenerative disorder of undetermined etiology with no effective treatments. Motor weakness and bulbar dysfunction lead to premature death, usually resulting from respiratory failure. While much of the research has focused on the role of neuronal dysfunction in ALS etiology, evidence from human patients and animal models indicates that the neuromuscular junction (NMJ) shows significant functional and structural abnormalities prior to the onset of motor neuron degeneration and behavioral symptoms. The development of novel experimental approaches will allow the study and manipulation of human NMJs and significantly contribute to our understanding of ALS pathogenesis, leading to advances in pharmacological treatments for the disease. A novel approach that has been employed in recent years is the use of human induced pluripotent stem cells (iPSCs) to generate cell types contributing to synaptic connectivity at the NMJ. The generation and differentiation of cells derived from ALS patient iPSCs is a promising method for investigating disease mechanisms and drug screening at NMJs in vitro. In this review, we cover the theories underlying the mechanisms of ALS pathogenesis at the NMJ, an overview of the recent developments in the generation of functional human neuromuscular connectivity in vitro, and the advances in human iPSC programming and differentiation technology.

This paper analyzes the determinants of network structure, as measured by hierarchy and monopolization, by examining various black market networks. We examine structures of networks on the Internet Dark Net (Virtual) and compare it to network structures of traditional black markets (Ground), using agent-based modeling. The purpose of modeling these two different types of illicit markets is to understand the network structure that emerges from the interactions of the agents in each environment. Traditional black markets are relatively hierarchical, with high degree and high betweenness. We compare the density and average length of the shortest path of the simulated Ground black market networks with our simulated Virtual network. We find that hierarchy and monopolization tendencies in networks are products of different transaction costs and information asymmetries. The Internet is an effective way to lower multiple aspects of network structure. We observe that the network structure surrounding the interactions in the Virtual black market is less hierarchical and slightly more monopolistic than the network structure of the Ground market.

An intronic GGGGCC repeat expansion in C9ORF72 is the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), but the pathogenic mechanism of this repeat remains unclear. Using human induced motor neurons (iMNs), we found that repeat-expanded C9ORF72 was haploinsufficient in ALS. We found that C9ORF72 interacted with endosomes and was required for normal vesicle trafficking and lysosomal biogenesis in motor neurons. Repeat expansion reduced C9ORF72 expression, triggering neurodegeneration through two mechanisms: accumulation of glutamate receptors, leading to excitotoxicity, and impaired clearance of neurotoxic dipeptide repeat proteins derived from the repeat expansion. Thus, cooperativity between gain- and loss-of-function mechanisms led to neurodegeneration. Restoring C9ORF72 levels or augmenting its function with constitutively active RAB5 or chemical modulators of RAB5 effectors rescued patient neuron survival and ameliorated neurodegenerative processes in both gain- and loss-of-function C9ORF72 mouse models. Thus, modulating vesicle trafficking was able to rescue neurodegeneration caused by the C9ORF72 repeat expansion. Coupled with rare mutations in ALS2, FIG4, CHMP2B, OPTN and SQSTM1, our results reveal mechanistic convergence on vesicle trafficking in ALS and FTD.

Multiple Sclerosis is a demyelinating disease of the CNS and the primary cause of neurological disability in young adults. Loss of myelinating oligodendrocytes leads to neuronal dysfunction and death and is an important contributing factor to this disease. Endogenous oligodendrocyte precursor cells (OPCs), which on differentiation are responsible for replacing myelin, are present in the adult CNS. As such, therapeutic agents that can stimulate OPCs to differentiate and remyelinate demyelinated axons under pathologic conditions may improve neuronal function and clinical outcome. We describe the details of an automated, cell-based, morphometric-based, high-content screen that is used to identify small molecules eliciting the differentiation of OPCs after 3 days. Primary screening was performed using rat CG-4 cells maintained in culture conditions that normally support a progenitor cell-like state. From a library of 73,000 diverse small molecules within the Sanofi collection, 342 compounds were identified that increased OPC morphological complexity as an indicator of oligodendrocyte maturation. Subsequent to the primary high-content screen, a suite of cellular assays was established that identified 22 nontoxic compounds that selectively stimulated primary rat OPCs but not C2C12 muscle cell differentiation. This rigorous triaging yielded several chemical series for further expansion and bio- or cheminformatics studies, and their compelling biological activity merits further investigation.

Using a tongue-inspired in vitro platform, Nesmith et al. demonstrate that DMD myoblasts fail to align and polarize with respect to extracellular matrix cues in the same manner as healthy myoblasts, resulting in diminished myotube formation and weaker contractile strength., Tongue weakness, like all weakness in Duchenne muscular dystrophy (DMD), occurs as a result of contraction-induced muscle damage and deficient muscular repair. Although membrane fragility is known to potentiate injury in DMD, whether muscle stem cells are implicated in deficient muscular repair remains unclear. We hypothesized that DMD myoblasts are less sensitive to cues in the extracellular matrix designed to potentiate structure–function relationships of healthy muscle. To test this hypothesis, we drew inspiration from the tongue and engineered contractile human muscle tissues on thin films. On this platform, DMD myoblasts formed fewer and smaller myotubes and exhibited impaired polarization of the cell nucleus and contractile cytoskeleton when compared with healthy cells. These structural aberrations were reflected in their functional behavior, as engineered tongues from DMD myoblasts failed to achieve the same contractile strength as healthy tongue structures. These data suggest that dystrophic muscle may fail to organize with respect to extracellular cues necessary to potentiate adaptive growth and remodeling.

Over the past few decades, a variety of different reagents for stem cell maintenance and differentiation have been commercialized. These reagents share a common goal in facilitating the manufacture of products suitable for cell therapy while reducing the amount of non-defined components. Lessons from developmental biology have identified signalling molecules that can guide the differentiation processin vitro, but less attention has been paid to the extracellular matrix used. With the introduction of more biologically relevant and defined matrices, that better mimic specific cell niches, researchers now have powerful resources to fine-tune theirin vitrodifferentiation systems, which may allow the manufacture of therapeutically relevant cell types. In this review article, we revisit the basics of the extracellular matrix, and explore the important role of the cell–matrix interaction. We focus on laminin proteins because they help to maintain pluripotency and drive cell fate specification.This article is part of the theme issue ‘Designer human tissue: coming to a lab near you’.

Enzymes that modify DNA are faced with significant challenges in specificity for both substrate binding and catalysis. We describe how single hydrogen bonds between M.HhaI, a DNA cytosine methyltransferase, and its DNA substrate regulate the positioning of a peptide loop which is approximately 28 A away. Stopped-flow fluorescence measurements of a tryptophan inserted into the loop provide real-time observations of conformational rearrangements. These long-range interactions that correlate with substrate binding and critically, enzyme turnover, will have broad application to enzyme specificity and drug design for this medically relevant class of enzymes.

Biomolecular self-assembly provides a basis for the bottom-up construction of useful and diverse nanoscale architectures. DNA is commonly used to create these assemblies and is often exploited as a lattice or an array. Although geometrically rigid and highly predictable, these sheets of repetitive constructs often lack the ability to be enzymatically manipulated or elongated by standard biochemical techniques. Here, we describe two approaches for the construction of position-controlled, molecular-scale, discrete, three- and four-way DNA junctions. The first approach for constructing these junctions relies on the use of nonmigrating cruciforms generated from synthetic oligonucleotides to which large, biologically generated, double-stranded DNA segments are enzymatically ligated. The second approach utilitizes the DNA methyltransferase-based SMILing (sequence-specific methyltransferase-induced labeling of DNA) method to site-specifically incorporate a biotin within biologically derived DNA. Streptavidin is then used to form junctions between unique DNA strands. The resultant assemblies have precise and predetermined connections with lengths that can be varied by enzymatic or hybridization techniques, or geometrically controlled with standard DNA functionalization methods. These junctions are positioned with single nucleotide resolution on large, micrometer-length templates. Both approaches generate DNA assemblies which are fully compatible with standard recombinant methods and thus provide a novel basis for nanoengineering applications.

Objectives The aim of the study was to evaluate ultrasonographic changes in the small intestine of cats with clinical signs of gastrointestinal disease and low or low–normal serum cobalamin concentrations. Methods Records for client-owned cats presenting to the small animal hospital with signs of gastrointestinal disease and in which serum cobalamin concentrations were measured from 2000–2013 were reviewed. Inclusion criteria were cobalamin concentrations Results Of 751 serum cobalamin measurements, hypocobalaminemia or low–normal cobalamin was identified in 270 cats, abdominal ultrasound was performed in 207 of those cats and a diagnosis was available for 75 of them. Small intestinal ultrasound changes were detected in 49/75 (65%) cats. Abnormalities included thickening, loss of wall layer definition, echogenicity alterations and discrete masses. Serum cobalamin concentrations Conclusions and relevance One-third of symptomatic cats with hypocobalaminemia or low–normal cobalamin concentrations may have an ultrasonographically normal small intestine. For the majority of cats in this study, histopathologic abnormalities were observed in the small intestine, regardless of ultrasound changes. These findings suggest gastrointestinal disease should not be excluded based on low–normal cobalamin concentrations, even with a concurrent normal ultrasound examination. Additional studies are needed in cats with low–normal serum cobalamin concentrations, as a definitive diagnosis was not pursued consistently in those cats. However, data from this study suggest that careful monitoring, histopathologic evaluation and future cobalamin supplementation may be warranted.

Currently, one of the main issues to improve the image quality of Magnetic Particle Imaging (MPI), besides the development of applicable MPI scanner systems and reconstruction methods, is the improvement of magnetic properties of magnetic nanoparticles (MNP), the so-called MPI tracer. Optimized tracers potentially enhance mass sensitivity and spatial resolution of MPI and may be the key for successful clinical MPI [1].

We provide an extensive analysis of the Deep Web, using data from the Silk Road which is an encrypted online marketplace that employs crypto currency and functions over the Tor network. Utilizing a modeling technique that is suggested by trade auction theory where parties, buyers and sellers have transparent reputations. We investigate how this model functions if only one party has an observable reputation and how the seller’s reputation plays into prices of goods and services. Our data set is parsed from the Silk Road website over a 9 month time period. We demonstrate that the online marketplace has been operating without governmental taxation or regulation and is functioning steadily. We discuss the robustness of spontaneous order with respect to the Deep Web as an emergent marketplace.

The characterization of conformational changes that drive induced-fit mechanisms and their quantitative importance to enzyme specificity are essential for a full understanding of enzyme function. Here, we report on M.HhaI, a sequence-specific DNA cytosine C(5) methyltransferase that reorganizes a flexible loop (residues 80-100) upon binding cognate DNA as part of an induced-fit mechanism. To directly observe this approximately 26A conformational rearrangement and provide a basis for understanding its importance to specificity, we replaced loop residues Lys-91 and Glu-94 with tryptophans. The double mutants W41F/K91W and W41F/E94W are relatively unperturbed in kinetic and thermodynamic properties. W41F/E94W shows DNA sequence-dependent changes in fluorescence: significant changes in equilibrium and transient state fluorescence that occur when the enzyme binds cognate DNA are absent with nonspecific DNA. These real-time, solution-based results provide direct evidence that binding to cognate DNA induces loop reorganization into the closed conformer, resulting in the correct assembly of the active site. We propose that M.HhaI scans nonspecific DNA in the loop-open conformer and rearranges to the closed form once the cognate site is recognized. The fluorescence data exclude mechanisms in which loop motion precedes base flipping, and we show loop rearrangements are directly coupled to base flipping, because the sequential removal of single hydrogen bonds within the target guanosine:cytosine base pair results in corresponding changes in loop motion.

Val121 is positioned immediately above the extrahelical cytosine in HhaI DNA C5-cytosine methyltransferase, and replacement with alanine dramatically interferes with base flipping and catalysis. DNA binding and kcat are decreased 105-fold for the Val121 → Ala mutant that has a normal circular dichroism spectrum and AdoMet affinity. The magnitude of this loss of function is comparable with removal of the essential catalytic Cys81. Surprisingly, DNA binding is completely recovered (increase of 105-fold) with a DNA substrate lacking the target cytosine base (abasic). Thus, interfering with the base flipping transition results in a dramatic loss of binding energy. Our data support an induced fit mechanism in which tight DNA binding is coupled to both base flipping and protein loop rearrangement. The importance of the proximal protein segment (His127–Thr132) in maintaining this critical interaction between Val121 and the flipped cytosine was probed with single site alanine substitutions. None of these mutants are significantly altered in secondary structure, AdoMet or DNA affinity, kmethylation, kinactivation, or kcat. Although Val121 plays a critical role in both extrahelical base stabilization and catalysis, its position and mobility are not influenced by individual residues in the adjacent peptide region. Structural comparisons with other DNA methyltransferases and DNA repair enzymes that stabilize extrahelical nucleotides reveal a motif that includes a positively charged or polar side chain and a hydrophobic residue positioned adjacent to the target DNA base and either the 5′- or 3′-phosphate.

To further explore possible avenues for accessing microbial biodiversity for drug discovery from natural products, we constructed and screened a 5,000-clone “shotgun” environmental DNA library by using an Escherichia coli-Streptomyces lividans shuttle cosmid vector and DNA inserts from microbes derived directly (without cultivation) from soil. The library was analyzed by several means to assess diversity, genetic content, and expression of heterologous genes in both expression hosts. We found that the phylogenetic content of the DNA library was extremely diverse, representing mostly microorganisms that have not been described previously. The library was screened by PCR for sequences similar to parts of type I polyketide synthase genes and tested for the expression of new molecules by screening of live colonies and cell extracts. The results revealed new polyketide synthase genes in at least eight clones. In addition, at least five additional clones were confirmed by high-pressure liquid chromatography analysis and/or biological activity to produce heterologous molecules. These data reinforce the idea that exploiting previously unknown or uncultivated microorganisms for the discovery of novel natural products has potential value and, most importantly, suggest a strategy for developing this technology into a realistic and effective drug discovery tool.

Glioblastoma multiform (GBM) remains clinical indication with significant "unmet medical need". Innovative new therapy to eliminate residual tumor cells and prevent tumor recurrences is critically needed for this deadly disease. A major challenge of GBM research has been the identification of novel molecular therapeutic targets and accurate diagnostic/prognostic biomarkers. Many of the current clinical therapeutic targets of immunotoxins and ligand-directed toxins for high-grade glioma (HGG) cells are surface sialylated glycoproteins. Therefore, methods that systematically and quantitatively analyze cell surface sialoglycoproteins in human clinical tumor samples would be useful for the identification of potential diagnostic markers and therapeutic targets for malignant gliomas. In this study, we used the bioorthogonal chemical reporter strategy (BOCR) in combination with label-free quantitative mass spectrometry (LFQ-MS) to characterize and accurately quantify the individual cell surface sialoproteome in human GBM tissues, in fetal, adult human astrocytes, and in human neural progenitor cells (NPCs). We identified and quantified a total of 843 proteins, including 801 glycoproteins. Among the 843 proteins, 606 (72%) are known cell surface or secreted glycoproteins, including 156 CD-antigens, all major classes of cell surface receptor proteins, transporters, and adhesion proteins. Our findings identified several known as well as new cell surface antigens whose expression is predominantly restricted to human GBM tumors as confirmed by microarray transcription profiling, quantitative RT-PCR and immunohistochemical staining. This report presents the comprehensive identification of new biomarkers and therapeutic targets for the treatment of malignant gliomas using quantitative sialoglycoproteomics with clinically relevant, patient derived primary glioma cells.

In an effort to characterize the diversity of mechanisms involved in cellular self-protection against the antitumor antibiotic mitomycin C (MC), DNA fragments from the producing organism (Streptomyces lavendulae) were introduced into Streptomyces lividans and transformants were selected for resistance to the drug. Subcloning of a 4.0-kb BclI fragment revealed the presence of an MC resistance determinant, mrd. Nucleotide sequence analysis identified an open reading frame consisting of 130 amino acids with a predicted molecular weight of 14,364. Transcriptional analysis revealed that mrd is expressed constitutively, with increased transcription in the presence of MC. Expression of mrd in Escherichia coli resulted in the synthesis of a soluble protein with an Mr of 14,400 that conferred high-level cellular resistance to MC and a series of structurally related natural products. Purified MRD was shown to function as a drug-binding protein that provides protection against cross-linking of DNA by preventing reductive activation of MC.

The mcr locus from Streptomyces lavendulae confers high level resistance (> 100 μg/ml) to mitomycin C (MC) and related mitomycins when cloned into Streptomyces lividans . Production of the mcrA gene product (MCRA) was shown to be MC-inducible by identification of MCRA ( M r of 54 kDa) using Western blot analysis and enzyme linked immunosorbent assay (ELISA). The magnitude of MCRA production was dependent on MC concentration, with primary induction starting at 0.1 lμg/ml and maximum induction at 10 μg/ml of the drug. Different levels of MCRA production were observed when other mitomycin metabolites were used as inducers, and the level of induction related directly to aziridine ring substitution on the individual molecules. Moreover, inducible synthesis of the mcrA gene product was unique to this structural class since production of MCRA did not occur as a general response to DNA damaging agents. The time profile of intracellular MCRA synthesis correlated with MC production in S. lavendulae , suggesting coordinated regulation of MC resistance and biosynthetic genes.

Articular cartilage, which is mainly composed of collagen II, enables smooth skeletal movement. Degeneration of collagen II can be caused by various events, such as injury, but degeneration especially increases over the course of normal aging. Unfortunately, the body does not fully repair itself from this type of degeneration, resulting in impaired movement. Microfracture, an articular cartilage repair surgical technique, has been commonly used in the clinic to induce the repair of tissue at damage sites. Mesenchymal stem cells (MSC) have also been used as cell therapy to repair degenerated cartilage. However, the therapeutic outcomes of all these techniques vary in different patients depending on their age, health, lesion size and the extent of damage to the cartilage. The repairing tissues either form fibrocartilage or go into a hypertrophic stage, both of which do not reproduce the equivalent functionality of endogenous hyaline cartilage. One of the reasons for this is inefficient chondrogenesis by endogenous and exogenous MSC. Drugs that promote chondrogenesis could be used to induce self-repair of damaged cartilage as a non-invasive approach alone, or combined with other techniques to greatly assist the therapeutic outcomes. The recent development of human induced pluripotent stem cell (iPSCs), which are able to self-renew and differentiate into multiple cell types, provides a potentially valuable cell resource for drug screening in a “more relevant” cell type. Here we report a screening platform using human iPSCs in a multi-well plate format to identify compounds that could promote chondrogenesis.

Two genes (mcrA and mcrB) from Streptomyces lavendulae that together confer resistance to mitomycin C were identified. This DNA appears to comprise a polycistronic operon with a drug-inducible leaderless mRNA. The deduced amino acid sequence of mcrA shows similarity to sequences of a special class of bacterial, plant, and animal oxygen oxidoreductases.

The idea of linking the liberal arts and professional education is not new. References to its importance are prominent in the reform literature of the past several decades and the reform agendas of the 1990s (Willis 1962; Schwebel, 1985). Much of the reform discussion has examined how general education can be enhanced and professional education (especially teacher education) limited. Indeed, there are some who proffer the idea that "limited" teacher education is best defined as "no" teacher educa

Although men's studies is no longer a novelty on college campuses, it can still raise some bewildered eyebrows and prompt a few explosive reactions. Recently, on a national computer bulletin board used by reference librarians, a request for journals, articles, and books “that analyze drama from a male/masculine perspective” touched off considerable crossfire among respondents. Beneath the hostilities, however, were serious questions and understandable confusions about the topic of men's studies. These concerns suggest that some clarifications concerning the new men's studies might be useful.

Nonlinear finite-element structural analyses were performed on the first stage high-pressure fuel turbopump blade of the Space Shuttle Main Engine. The analyses examined the structural response and the dynamic characteristics at typical operating conditions. Single crystal material PWA-1480 was considered for the analyses. Structural response and the blade natural frequencies with respect to the crystal orientation were investigated. The analyses were conducted based on typical test stand engine cycle. Influence of combined thermal, aerodynamic, and centrifugal loadings was considered. Results obtained showed that the single crystal secondary orientation effects on the maximum principal stresses are not highly significant.

A finite element structure code and a finite difference Euler solver are combined to provide a more accurate analysis of a large-scale propfan. The NASTRAN finite element code is used to compute the blade deflection due to centrifugal and aerodynamic loads, and the NASPROP finite difference 3-D Euler code is employed to compute the steady-state aerodynamic load of the deflected blade. The effects of deflection on the aerodynamic and propeller performance characteristics are discussed. The local pressure profiles of deflected and undeflected blade models are compared with test data. The results show that improvements can be made by including proper blade deflection in the numerical model.

Capillary extrudate analysis was performed on two aqueous alumina pastes having average particle sizes of I and 5 μm, respectively. The batches were composed of hydroxypropyl methylcellulose binder and a stearate lubricant. Extrusion as a function of solids loading, batch mixedness, and extrusion velocity was measured. Results show that the initial particle size and solids loading influenced the uniformity and appearance of the cylindrical extrudates. Further variation of particle size distribution showed a strong pressure versus length/diameter relationship.

Gold nanoparticles were modified with RNA and utilized to detect specific DNA sequences and various RNA nucleases.

Optimizing production in mature fields depends greatly on proper reservoir characterization. After a certain period of production, a reservoir may exhibit changes in its properties because of changes in formation water salinity arising from water injection, left-behind residual oil in the rock, and changes in pressure regime. These factors, combined with complexities in the original reservoirs properties, such as rapid variations in permeability and oil viscosity, strongly affect the degree of uncertainty in evaluating and predicting productive zones when using only conventional logging methods. These variations affect the responses of most conventional logs. Consequently, traditional log analysis models may fail to provide realistic evaluation results and may not achieve appropriate production forecasts. Common examples of such failures have been recognized when producing high water content from a zone believed to be hydrocarbon or when perforating an interval that does not produce. New logging technologies, such as magnetic resonance imaging (MRI), demonstrate promising formation evaluation results in mature fields. The MRI technology helps to properly distinguish candidate production zones and provide key in-situ reservoir properties, including hydrocarbon type, reservoir quality in terms of permeability and porosity, and barrier zones. The ability of MRI to determine oil viscosity influences the selection and elimination of zones to be produced based on its fluids mobilities. Thus, MRI serves well in the selection of hydrocarbon producing intervals. This paper discusses the effectiveness of applying the MRI technology in characterizing the reservoir fluid properties in the El Furrial field, East Venezuela. It also highlights the value of this technology in minimizing the cost of mis-identified zones for production or testing by identifying best candidate intervals. Verification of the MRI results with actual production testing and/or formation pressure measurements will be demonstrated in the article.

Electrostatic assembly of cationic nanoparticles onto the negatively charged backbone of double-stranded DNA has been shown to produce one-dimensional chains with potential use as nanoelectronic components. In this paper, micron long DNA templates stretched on aminosilane- and hexamethyldisilazane-modified silicon surfaces are used to assemble 3.5 nm gold nanoparticles passivated with cationic thiocholine. Atomic force microscopy is used to analyze the density and defects along the approximately 5 nm high structures, with comparison between positively charged and neutral surfaces. Low background adsorption of nanoparticles is facilitated by both these surface chemistries, while the neutral surface yields a more densely packed assembly.

Molecular dynamics (MD) simulations of HhaI DNA methyltransferase and statistical coupling analysis (SCA) data on the DNA cytosine methyltransferase family were combined to identify residues that are coupled by coevolution and motion. The highest ranking correlated pairs from the data matrix product (SCA·MD) are colocalized and form stabilizing interactions; the anticorrelated pairs are separated on average by 30 Å and form a clear focal point centered near the active site. We suggest that these distal anti-correlated pairs are involved in mediating active-site compressions that may be important for catalysis. Mutants that disrupt the implicated interactions support the validity of our combined SCA·MD approach.

We have characterized Escherichia coli DNA adenine methyltransferase, a critical regulator of bacterial virulence. Steady-state kinetics, product inhibition, and isotope exchange studies are consistent with a kinetic mechanism in which the cofactor S-adenosylmethionine binds first, followed by sequence-specific DNA binding and catalysis. The enzyme has a fast methyl transfer step followed by slower product release steps, and we directly demonstrate the competence of the enzyme cofactor complex. Methylation of adjacent GATC sites is distributive with DNA derived from a genetic element that controls the transcription of the adjacent genes. This indicates that the first methylation event is followed by enzyme release. The affinity of the enzyme for both DNA and S-adenosylmethionine was determined. Our studies provide a basis for further structural and functional analysis of this important enzyme and for the identification of inhibitors for potential therapeutic applications.