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1.
In this study, we use the measured extent of metal adsorption onto bacterial cells to constrain a linear free energy relationship that allows estimation of unknown stability constants for metal-bacterial surface complexes based on the value of corresponding aqueous metal-acetate stability constants. A previous study (Fein et al., 2001) used metal adsorption experiments to constrain a similar relationship, but the experiments were conducted using acid-washed bacteria, and subsequent evidence (Borrok et al., 2004a) shows that the acid-washing step affects the extent of adsorption of a number of metals onto bacterial surfaces. We measured the adsorption of Zn, Ni, Co, Sr, and Nd onto Bacillus subtilis in 0.1 M NaClO4 as a function of pH and metal:bacterial site ratio, using a non-electrostatic discrete four-site model of the bacterial protonation reactions as a basis for the metal adsorption modeling. The adsorption of the divalent cations (Zn, Ni, Co, and Sr) could best be modeled by considering adsorption reactions involving three sites on the bacterial surface; we used a one-site model to account for the Nd data that covered a more restricted pH range. The calculated stability constants for metal-Site 2 bacterial surface complexes are used to re-calibrate the linear free energy relationship previously defined by Fein et al. (2001). There is a significant difference between the original and the re-calibrated lines for weakly binding cations such as Sr2 +, but the difference becomes negligible for the stronger-binding cations. Because the linear free energy relationship defined in this study was calibrated from experiments that involved bacteria that were not exposed to acidic conditions, the estimated stability constant values that result from using this relationship are likely to reasonably reflect bacterial adsorption behaviors that occur in realistic geologic settings. 相似文献
2.
Zlatko Janeba Noha Maklad Morris J. Robins 《Nucleosides, nucleotides & nucleic acids》2013,32(10-12):1729-1743
Copper(I)-catalyzed 5-endo-dig cyclizations of 5-(alkyn-1-yl)uracil derivatives had given poor yields of substituted furo[2, 3]pyrimidin-2-ones unless the uracil ring was substituted at N1 with alkyl or glycosyl groups. This limited flexibility for the synthesis of analogues with varied substituents at N3 and/or C6 of the furo[2, 3]pyrimidin-2-one core has been overcome with 5-(3-hydroxyalkyn-1-yl)uracil compounds with no substituent at N1. Manipulation of the side-chain hydroxyl group gives access to additional furo[2,3-d]pyrimidin-2-one analogues. 相似文献
3.
An automated, iterative approach to finding the lowest energy, ionic diffusion paths through a periodic structure has been developed within our new code (written in FORTRAN 77 and named Bubble). The approach is quite general in that it can be applied to find, at a chosen temperature, the accessible (ergodic) regions of a hyper-surface, which is defined across a uniform grid [1]. We describe both our implementation within the Bubble code and its application to locating the approximate transition states for Mg interstitial diffusion in forsterite, which can then be refined using standard transition state searching [2]. 相似文献
4.
Public familiarity with basic scientific concepts and principles has been proposed as essential for effective democratic decision-making (Miller, 1998). Empirical research, however, finds that public ‘scientific literacy’ is generally low, falling well short of what normative criteria would consider ‘acceptable’. This has prompted calls to better engage, educate and inform the public on scientific matters, with the additional, usually implicit assumption that a knowledgeable citizenry should express more supportive and favourable attitudes toward science. Research investigating the notion that ‘to know science is to love it’ has provided only weak empirical support and has itself been criticised for representing science and technology as a unified and homogenous entity. In practice, it is argued, how knowledge impacts on the favourability of attitudes will depend on a multiplicity of factors, not least of which is the particular area of science in question and the technologies to which it gives rise (Evans & Durant, 1992). This article uses a new method for examining the knowledge-attitude nexus on a prominent area of 21st century science—biotechnology. The idea that greater scientific knowledge can engender change in the favourability of attitudes toward specific areas of science is investigated using data from the 2000 British Social Attitudes Survey and the 1999 Wellcome Consultative Panel on Gene Therapy. Together the surveys measure public opinion on particular applications of genetic technologies, including gene therapy and the use of genetic data, as well as more general attitudes towards genetic research. We focus our analysis on how two different measures of knowledge impact on these attitudes; one a general measure of scientific knowledge, the other relating specifically to knowledge of modern genetic science. We investigate what impact these knowledge domains have on attitudes towards biotechnology using a regression-based modelling technique (Bartels, 1996; Althaus, 1998; Sturgis, 2003). Controlling for a range of socio-demographic characteristics, we provide estimates of what collective and individual opinion would look like if everyone were as knowledgeable as the currently best-informed members of the general public on the knowledge domains in question. Our findings demonstrate that scientific knowledge does appear to have an important role in determining individual and group attitudes to genetic science. However, we find no support for a simple ‘deficit model’ of public understanding, as the nature of the relationship itself depends on the application of biotechnology in question and the social location of the individual. 相似文献
5.
Sequestration of aggregates into specialized deposition sites occurs in many species across all kingdoms of life ranging from bacteria to mammals and is commonly believed to have a cytoprotective function. Yeast cells possess at least 3 different spatially separated deposition sites, one of which is termed “Insoluble Protein Deposit (IPOD)” and harbors amyloid aggregates. We have recently discovered that recruitment of amyloid aggregates to the IPOD uses an actin cable based recruitment machinery that also involves vesicular transport.1 Here we discuss how different proteins known to be involved in vesicular transport processes to the vacuole might act to guide amyloid aggregates to the IPOD. These factors include the Myosin V motor protein Myo2 involved in transporting vacuolar vesicles along actin cables, the transmembrane protein Atg9 involved in the recruitment of large precursor hydrolase complexes to the vacuole, the phosphatidylinositol/ phosphatidylcholine (PI/PC) transfer protein Sec 14 and the SNARE chaperone Sec 18. Furthermore, we present new data suggesting that the yeast dynamin homolog Vps1 is also crucial for faithful delivery of the amyloid model protein PrD-GFP to the IPOD. This is in agreement with a previously identified role for Vps1 in recruitment of heat-denatured aggregates to a perivacuolar deposition site.2 相似文献
6.
Sabine Elowe 《Cell cycle (Georgetown, Tex.)》2017,16(8):746-748
Tyrosine phosphorylation is rare, representing only about 0.5% of phosphorylations in the cell under basal conditions. While mitogenic tyrosine kinase signaling has been extensively explored, the role of phosphotyrosine signaling across the cell cycle and in particular during mitosis is poorly understood.
Two recent, independent studies tackled this question from different angles to reveal exciting new insights into the role of this modification during cell division. Caron et al.1 exploited mitotic phosphoproteomics data sets to determine the extent of mitotic tyrosine phosphorylation, and St-Denis et al.2 identified protein tyrosine phosphatases from all subfamilies as regulators of mitotic progression or spindle formation. These studied collectively revealed that tyrosine phosphorylation may play a more prominent and active role in mitotic progression than previously appreciated. 相似文献
7.
《Journal of biological dynamics》2013,7(2):117-130
We address several conjectures raised in Cantrell et al. [Evolution of dispersal and ideal free distribution, Math. Biosci. Eng. 7 (2010), pp. 17–36 [9]] concerning the dynamics of a diffusion–advection–competition model for two competing species. A conditional dispersal strategy, which results in the ideal free distribution of a single population at equilibrium, was found in Cantrell et al. [9]. It was shown in [9] that this special dispersal strategy is a local evolutionarily stable strategy (ESS) when the random diffusion rates of the two species are equal, and here we show that it is a global ESS for arbitrary random diffusion rates. The conditions in [9] for the coexistence of two species are substantially improved. Finally, we show that this special dispersal strategy is not globally convergent stable for certain resource functions, in contrast with the result from [9], which roughly says that this dispersal strategy is globally convergent stable for any monotone resource function. 相似文献
8.
In Disney/Pixar's phenomenally popular animated film Finding Nemo (Stanton, 2003), one of the central themes of fish welfare was highlighted when the moorish idol, Gill, commented, “Fish aren't meant to be kept in a box, kid. It does things to you.” The notion that fish might have the capacity to suffer in captivity (Chandroo, Duncan, & Moccia, 2004a, 2004b) links to the larger question of sentiency, which remains a fundamental tenet when justifying concerns for nonhuman animal welfare (Dawkins, 2006; Huntingford et al., 2006). Although terrestrial nonhuman-animal welfare has been discussed and explored for many years, the development of aquatic animal welfare concepts and approaches remains relatively new and beyond public awareness (Braastad, Damsgård, & Juell, 2006; Broom, 2007; Farmed Animal Welfare Council, 1996; Fisheries Society of the British Isles, 2002; Håstein, Scarfe, & Lund, 2005; Iwama, 2007; Schreck, 1981). 相似文献
9.
Andre Schmandke Alice C Mosberger Antonio Schmandke Zeliha Celen Martin E Schwab 《Cell Adhesion & Migration》2013,7(6):451-453
After central nervous system (CNS) insults, such as spinal cord injury or traumatic brain injury, neurons encounter a complex microenvironment where mechanisms that promote regeneration compete with inhibitory processes. Sprouting and axonal re-growth are key components of functional recovery, but are often counteracted by inhibitory molecules. Several strategies are being pursued whereby these inhibitory molecules are either being neutralized with blocking antibodies, with enzymatic degradation or downstream signaling events are being interfered with. Two recent studies1,2 show that activating integrin signaling in dorsal root ganglion (DRG) neurons renders them able to overcome inhibitory signals, and could possibly lead to new strategies to improve neuronal regeneration. 相似文献
10.
The natural remobilization of an initially static mixed dense non-aqueous phase liquid (DNAPL) pool due to dissolution was demonstrated by (Roy et al. 2002, 2004) using a compositional mathematical model and laboratory experiments with open pools over a porous medium. The purposes of this study were to: a) demonstrate natural remobilization for a pool within porous media (as opposed to an open pool); and b) analyze the capillary effects associated with residual formation, a changing saturation profile, hysteresis, and aging, as these processes may reduce the potential for natural remobilization of pools in porous media. DNAPL pools comprised of tetrachloroethene and benzene were created within a zone of larger glass beads overlying smaller glass beads, in a water-saturated 2-D flow cell. In one case, remobilization occurred in the form of a DNAPL finger, after 56 days of flushing. In another case, no remobilization had occurred after 64 days of flushing, though the density increased by 430 kg m ?3 and remobilization was predicted by the compositional model. Comparison of observations with model predictions suggest that contact angle hysteresis, related to an observed change in wettability, was the most significant contributing factor causing overprediction of the potential for natural remobilization. 相似文献
11.
Tad W. Patzek 《植物科学评论》2008,27(4):272-293
This paper considers the local, field-scale sustainability of a productive industrial maize agrosystem that has replaced a fertile grassland ecosystem.
Using the revised thermodynamic approach of Svirezhev (1998, 2000) and Steinborn and Svirezhev (2000), it is shown that currently this agrosystem is unsustainable in the U.S., with or without tilling the soil. The calculated average erosion rates of soil necessary to dissipate the entropy produced by U.S. maize agriculture, 23–45 t ha?1 yr?1, are bounded from above by an experimental estimate of mean soil erosion by conventional agriculture worldwide, 47 t ha?1 yr?1, (Montgomery, 2007). Between 1982 and 1997, US agriculture caused an estimated 7–23 t ha?1 yr?1 of average erosion with the mean of 15 t ha?1 yr?1 (USDA-NRCS Database). The lower mean erosion rate of no till agriculture, 1.5 t ha?1 yr?1 (Montgomery, 2007), necessitates the elimination of weeds and pests with field chemicals—with the ensuing chemical and biological soil degradation, and chemical runoff—to dissipate the produced entropy. The increased use of field chemicals that replace tillers is equivalent to the killing or injuring of up to 300 kg ha?1 yr?1 of soil flora and fauna. Additional soil degradation, not calculated here, occurs by acidification, buildup of insoluble metal compounds, and buildup of toxic residues from field chemicals. The degree of unsustainability of an average U.S. maize field is high, requiring 6–13 times more energy to reverse soil erosion and degradation, etc., than the direct energy inputs to maize agriculture. This additional energy, if spent, would not increase maize yields. The calculated “critical yield” of “organic” maize agriculture that does not use field chemicals and fossil fuels is only 30 percent lower than the average maize yield of 8.7 tons per hectare (～140 bu/acre) assumed here. This critical yield would not likely be achieved and sustained by large monocultures, but might be achieved by more balanced organic polycultures (Baum et al., 2008). 相似文献
12.
Ilya V. Buynevich 《Ichnos》2013,20(4):189-191
Recognition and sampling of traces in unconsolidated sands present a major challenge for ichnologists. This can be partially remedied through the application of high-resolution geophysical techniques, such as ground-penetrating radar (GPR or georadar), which uses electromagnetic impulse for continuous imaging of shallow subsurface. It addition to geological applications, GPR imaging has been used in several studies focused on animal traces as related to conservation of endangered fossorial species (Kinlaw et al., 2007; Martin et al., 2011), slope and levee stability (Nichol et al., 2003; Di Prinzio et al., 2010), and mapping of fossil tracks (Matthews et al., 2006; Aucoin and Hasbargen, 2010) and tracking surfaces (Webb, 2007). Few efforts have been dedicated specifically to characterizing burrow and track characteristics (Stott, 1996; Sensors & Software Inc., 2010 [compilation on geophysical projects related to animal burrows]; Buynevich and Hasiotis, 2011; Buynevich et al., 2011; Martin et al., 2011) and most of the above studies are published in journals not routinely accessed by ichnologists. 相似文献
13.
Christopher J. Derrick 《Cell cycle (Georgetown, Tex.)》2017,16(1):23-32
Localized mRNA translation is a widespread mechanism for targeting protein synthesis, important for cell fate, motility and pathogenesis. In Drosophila, the spatiotemporal control of gurken/TGF-α mRNA translation is required for establishing the embryonic body axes. A number of recent studies have highlighted key aspects of the mechanism of gurken mRNA translational control at the dorsoanterior corner of the mid-stage oocyte. Orb/CPEB and Wispy/GLD-2 are required for polyadenylation of gurken mRNA, but unlocalized gurken mRNA in the oocyte is not fully polyadenylated.1 At the dorsoanterior corner, Orb and gurken mRNA have been shown to be enriched at the edge of Processing bodies, where translation occurs.2 Over-expression of Orb in the adjacent nurse cells, where gurken mRNA is transcribed, is sufficient to cause mis-expression of Gurken protein.3 In orb mutant egg chambers, reducing the activity of CK2, a Serine/Threonine protein kinase, enhances the ventralized phenotype, consistent with perturbation of gurken translation.4 Here we show that sites phosphorylated by CK2 overlap with active Orb and with Gurken protein expression. Together with our new findings we consolidate the literature into a working model for gurken mRNA translational control and review the role of kinases, cell cycle factors and polyadenylation machinery highlighting a multitude of conserved factors and mechanisms in the Drosophila egg chamber. 相似文献
14.
《Autophagy》2013,9(8):801-802
Considerable attention has been paid to the topic of autophagy induction. In part, this is because of the potential for modulating this process for therapeutic purposes. Of course we know that induced autophagy can also be problematic—for example, when trying to eliminate an established tumor that might be relying on autophagy for its own cytoprotective uses. Accordingly, inhibitory mechanisms have been considered; however, the corresponding studies have tended to focus on the pathways that block autophagy under noninducing conditions, such as when nutrients are available. In contrast, relatively little is known about the mechanisms for inhibiting autophagy under inducing conditions. Yet, this type of regulation must be occurring on a routine basis. We know that dysregulation of autophagy, e.g., due to improper activation of Beclin 1 leading to excessive autophagy activity, can cause cell death.1 Accordingly, we assume that during starvation or other inducing conditions there must be a mechanism to modulate autophagy. That is, once you turn it on, you do not want to let it continue unchecked. But how is autophagy downregulated when the inducing conditions still exist? 相似文献
15.
《Biodemography and social biology》2013,59(1):42-66
Recent adaptationist accounts of human mental and physical health have reinvigorated the debate over the evolution of human intelligence. In the tradition of strong inference the current study was developed to determine whether either Miller's (1998, 2000a) Fitness Indicator Theory or Rushton's (1985, 2000) Differential-K Theory better accounts for general intelligence (“g”) in an undergraduate university population (N = 192). Owing to the lengthy administration time of the test materials, a newly developed 18-item short form of the Ravens Advanced Progressive Matrices (APM-18; Sefcek, Miller, and Figueredo 2007) was used. A significant, positive relationship between K and F (r = .31, p < .001) emerged. Contrary to predictions, no significant relationships were found between “g” and either K or F (r = –.09, p ≥ .05 and r = .11, p ≥ .05, respectively). Though generally contrary to both hypotheses, these results may be explained in relation to antagonistic pleiotropy and a potential failure to derive correct predictions for within-species comparisons directly from the results of between-species comparisons. 相似文献
16.
17.
《Cell Adhesion & Migration》2013,7(4):378-383
Cell migration is a highly integrated, multistep process that plays an important role in physiological and pathological processes. The migrating cell is highly polarized, with complex regulatory pathways that integrate its component processes spatially and temporally.1 The Drosophila tumor suppressor, Lethal (2) giant larvae (Lgl), regulates apical-basal polarity in epithelia and asymmetric cell division.2 But little is known about the role of Lgl in establishing cell polarity in migrating cells. Recently, we showed that the mammalian Lgl1 interacts directly with non-muscle myosin IIA (NMIIA), inhibiting its ability to assemble into filaments in vitro.3 Lgl1 also regulates the cellular localization of NMIIA, the maturation of focal adhesions, and cell migration.3 We further showed that phosphorylation of Lgl1 by aPKCζ prevents its interaction with NMIIA and is important for Lgl1 and acto-NMII cytoskeleton cellular organization.4 Lgl is a critical downstream target of the Par6-aPKC cell polarity complex; we showed that Lgl1 forms two distinct complexes in vivo, Lgl1-NMIIA and Lgl1-Par6-aPKCζ in different cellular compartments.4 We further showed that aPKCζ and NMIIA compete to bind directly to Lgl1 through the same domain. These data provide new insights into the role of Lgl1, NMIIA, and Par6-aPKCζ in establishing front-rear polarity in migrating cells. In this commentary, I discuss the role of Lgl1 in the regulation of the acto-NMII cytoskeleton and its regulation by the Par6-aPKCζ polarity complex, and how Lgl1 activity may contribute to the establishment of front-rear polarity in migrating cells. 相似文献
18.
《Cell cycle (Georgetown, Tex.)》2013,12(19):3555-3558
CEP192 is a centrosome protein that plays a critical role in centrosome biogenesis and function in mammals, Drosophila and C. elegans.1-6 Moreover, CEP192-depleted cells arrest in mitosis with disorganized microtubules, suggesting that CEP192’s function in spindle assembly goes beyond its role in centrosome activity and pointing to a potentially more direct role in the regulation of the mitotic microtubule landscape.7 To better understand CEP192 function in mitosis, we used mass spectrometry to identify CEP192-interacting proteins. We previously reported that CEP192 interacts with NEDD1, a protein that associates with the γ-tubulin ring complex (γ-TuRC) and regulates its phosphorylation status during mitosis.8 Additionally, within the array of proteins that interact with CEP192, we identified the microtubule binding K63-deubiquitinase CYLD. Further analyses show that co-depletion of CYLD alleviates the bipolar spindle assembly defects observed in CEP192-depleted cells. This functional relationship exposes an intriguing role for CYLD in spindle formation and raises the tantalizing possibility that CEP192 promotes robust mitotic spindle assembly by regulating K63-polyubiquitin-mediated signaling through CYLD. 相似文献
19.
Theory, research, and application in developmental science share the conceptual and methodological challenges of integrating the study of the course of a person's intra-individual changes and the formulation of subgroup (differential) or nomothetic generalizations. One approach to these challenges has involved building tailored construct representations that filter out irrelevant idiosyncratic information hampering the articulation of nomothetic relations by means of individual level factor analysis (P–technique). Exploring this approach has provided initially promising results (Nesselroade, Gerstorf, Hardy, & Ram, 2007). We present a specification of an alternative to traditional factor invariance (higher-order invariance) that further formalizes these ideas and examine the results of some simulation experiments designed to evaluate the appropriateness of the implementation. The results also have implications for use in basic and applied work across the life span of between-persons variation and subgroup comparisons to establish relations among variables. 相似文献
20.
《朊病毒》2013,7(6):405-411
ABSTRACTWithin the mammalian prion field, the existence of recombinant prion protein (PrP) conformers with self-replicating (ie. autocatalytic) activity in vitro but little to no infectious activity in vivo challenges a key prediction of the protein-only hypothesis of prion replication – that autocatalytic PrP conformers should be infectious. To understand this dissociation of autocatalysis from infectivity, we recently performed a structural and functional comparison between a highly infectious and non-infectious pair of autocatalytic recombinant PrP conformers derived from the same initial prion strain.1 We identified restricted, C-terminal structural differences between these 2 conformers and provided evidence that these relatively subtle differences prevent the non-infectious conformer from templating the conversion of native PrPC substrates containing a glycosylphosphatidylinositol (GPI) anchor.1 In this article we discuss a model, consistent with these findings, in which recombinant PrP, lacking post-translational modifications and associated folding constraints, is capable of adopting a wide variety of autocatalytic conformations. Only a subset of these recombinant conformers can be adopted by post-translationally modified native PrPC, and this subset represents the recombinant conformers with high specific infectivity. We examine this model's implications for the generation of highly infectious recombinant prions and the protein-only hypothesis of prion replication. 相似文献