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Luke L. M. Heaton Eduardo López Philip K. Maini Mark D. Fricker Nick S. Jones 《Proceedings. Biological sciences / The Royal Society》2010,277(1698):3265-3274
Cord-forming fungi form extensive networks that continuously adapt to maintain an efficient transport system. As osmotically driven water uptake is often distal from the tips, and aqueous fluids are incompressible, we propose that growth induces mass flows across the mycelium, whether or not there are intrahyphal concentration gradients. We imaged the temporal evolution of networks formed by Phanerochaete velutina, and at each stage calculated the unique set of currents that account for the observed changes in cord volume, while minimizing the work required to overcome viscous drag. Predicted speeds were in reasonable agreement with experimental data, and the pressure gradients needed to produce these flows are small. Furthermore, cords that were predicted to carry fast-moving or large currents were significantly more likely to increase in size than cords with slow-moving or small currents. The incompressibility of the fluids within fungi means there is a rapid global response to local fluid movements. Hence velocity of fluid flow is a local signal that conveys quasi-global information about the role of a cord within the mycelium. We suggest that fluid incompressibility and the coupling of growth and mass flow are critical physical features that enable the development of efficient, adaptive biological transport networks. 相似文献
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How often will elections end in landslides? What is the probability for a head-to-head race? Analyzing ballot results from several large countries rather anomalous and yet unexplained distributions have been observed. We identify tactical voting as the driving ingredient for the anomalies and introduce a model to study its effect on plurality elections, characterized by the relative strength of the feedback from polls and the pairwise interaction between individuals in the society. With this model it becomes possible to explain the polarization of votes between two candidates, understand the small margin of victories frequently observed for different elections, and analyze the polls'' impact in American, Canadian, and Brazilian ballots. Moreover, the model reproduces, quantitatively, the distribution of votes obtained in the Brazilian mayor elections with two, three, and four candidates. 相似文献
5.
Eduardo J. Delgado 《Journal of molecular modeling》2010,16(8):1421-1425
Despite their importance as herbicides, dimethoxypyrimidinylsalicylic acids has been poorly characterized from a physical-chemical
point of view. This lack of information has prevented the assessment of their impact in the environment once they are released.
In this study, environmentally important properties (free energy of solvation, Henry’s law constant, octanol/air, and octanol/water
partition coefficients) of 39 dimethoxypyrimidinylsalicylic derived compounds are calculated by density functional theory
(DFT) methods at B3LYP/6-31G(d,p) level of theory using the Poisson-Boltzmann solvation model. These properties have not been
reported previously for this family of compounds, neither experimentally or theoretically. 相似文献
6.
M K Ram L J Andrade T B Phillips M R van Schravendijk 《Protein expression and purification》1999,17(2):305-311
The A(280)/A(260) ratio of a purified protein is frequently used as an indication of the purity of the preparation with respect to nucleic acids. We show here that for low-molecular-weight recombinant proteins purified from Escherichia coli, a low A(280)/A(260) ratio can also result from contamination with UDP-linked murein precursors derived from bacterial cell wall metabolism. Although these precursors are small molecules of molecular weight 1000-1200, they comigrate in gel filtration with recombinant human FKBP (MW 11,820). This gel filtration behavior, which is distinct from that of unmodified mononucleotides, does not reflect binding interactions with FKBP, but is an intrinsic property of these precursors. Therefore, these molecules would be expected to copurify with other low-molecular-weight proteins, especially in the abbreviated purification protocols made possible by freeze-thaw release of recombinant proteins from E. coli (Johnson, B. H., and Hecht, M. H. (1994) BioTechnology 12, 1357-1360). Several alternative strategies are discussed for integrating these findings into the design of improved purification procedures for low-molecular-weight recombinant proteins. 相似文献
7.
Capuchin monkeys (Sapajus spp.) in captive settings frequently manipulate and throw objects. In the wild, they may push or drop stones and sticks toward targets during inter- or intraspecific threat displays. In addition, female capuchin monkeys exhibit a broad repertoire of behaviors during their proceptive period, including facial expressions, vocalizations, stereotyped body postures, and touch-and-run behavior. This study reports stone throwing as a newly-described communicative behavior during the proceptive display of females in a group of bearded capuchin monkeys (S. libidinosus) in Serra da Capivara National Park, Brazil. During a two-year study, three females from one group were seen throwing stones at males during their proceptive phase. After this period, three other females in the same group exhibited the same behavior. Although it may be possible that this pattern is the result of several independent innovations by each female, the apparent absence of this behavior in other groups leads us to suggest that we have documented the diffusion of a new behavioral trait or tradition within this capuchin social group. 相似文献
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P Bonaldo V Russo F Bucciotti G M Bressan A Colombatti 《The Journal of biological chemistry》1989,264(10):5575-5580
A cDNA library constructed from chick aorta poly(A+) RNA in the expression vector pEX1 was screened with rabbit polyclonal antisera. Additional clones were obtained by DNA-DNA hybridization with subclones from the most 5'- and 3'-ends. The overlapping clones span 4.6 kilobases and code for the entire alpha 1 (VI) chain. The nucleotide sequence reveals a 3057-base pair open reading frame that codes for 1019 amino acids. Analysis of the deduced amino acid sequence predicts that alpha 1 (VI) has one collagenous domain (COL) of 336 residues flanked by three repeated domains of about 200 residues each, one at the amino (A'3) and two at the carboxyl ends (A'2 and A'1), respectively, that are similar to the type A repeats of von Willebrand Factor. The COL domain presents two short interruptions near the carboxyl end of the triple helix and three of the six potential N-asparaginyl-linked carbohydrate attachment sites (Asn-Xaa-Ser/Thr). Furthermore, it contains 1 cysteine at position 89 that could participate in the formation of dimers and 3 Arg-Gly-Asp sequences that might be potential sites for cell adhesion. The COL domain shows an extended region, starting from position 40, within the triple helix, made of 14 Gly-Xaa-Yaa triplets that lack proline in the Y position, suggesting that it might be more flexible than the rest of the domain. At the junction of the COL with the N- and C-terminal domains, there are several cysteines that could confer the well known resistance of type VI collagen to pepsin and collagenase digestion under nonreducing conditions. The present sequence data allow a structural model for type VI collagen assembly to be proposed that is consistent with the structure implied from previous electron microscopic observation by Furthmayr et al. (Furthmayr, H., Wiedemann, H., Timpl, R., Odermatt, R., and Engel, J. (1983) Biochem. J. 221, 303-311). 相似文献
10.
Eduardo León-Ruiz Purificación Alcázar Eugenio Domínguez-Vilches Carmen Galán 《Aerobiologia》2011,27(1):37-50
The present study sought to determine which of the common Poaceae species in the study area contribute most to the Poaceae
pollen season curve, and to determine the phenological behaviour of the species studied. The different floral phenophases
in thirty-three Poaceae species common in and around the city of Córdoba (SW Iberian Peninsula) were checked periodically
over the period 2004–2006. Results showed that longer phenological ranges were recorded in the coolest and wettest year, and
shorter ranges in the warmest and driest year. Moreover, ranges varied as a function of altitude: populations in lower-lying
areas flowered earlier than those at higher altitudes. The results, taken in conjunction with the findings of preliminary
research into potential pollen production, showed that probably only four of the Poaceae species studied—Dactylis glomerata, Lolium rigidum, Trisetaria panicea and Vulpia geniculata—were major contributors to the Poaceae airborne pollen curve. 相似文献