@article{1297, abstract = {In flies, the large tangential cells of the lobula plate represent an important processing center for visual navigation based on optic flow. Although the visual response properties of these cells have been well studied in blowflies, information on their synaptic organization is mostly lacking. Here we study the distribution of presynaptic release and postsynaptic inhibitory sites in the same set of cells in Drosophila melanogaster. By making use of transgenic tools and immunohistochemistry, our results suggest that HS and VS cells of Drosophila express γ-aminobutyric acid (GABA) receptors in their dendritic region within the lobula plate, thus being postsynaptic to inhibitory input there. At their axon terminals in the protocerebrum, both cell types express synaptobrevin, suggesting the presence of presynaptic specializations there. HS- and VS-cell terminals additionally show evidence for postsynaptic GABAergic input, superimposed on this synaptic polarity. Our findings are in line with the general circuit for visual motion detection and receptive field properties as postulated from electrophysiological and optical recordings in blowflies, suggesting a similar functional organization of lobula plate tangential cells in the two species.}, author = {Raghu, Shamprasad V and Maximilian Jösch and Borst, Alexander and Reiff, Dierk F}, journal = {Journal of Comparative Neurology}, number = {4}, pages = {598 -- 610}, publisher = {Wiley-Blackwell}, title = {{Synaptic organization of lobula plate tangential cells in Drosophila: γ-aminobutyric acid receptors and chemical release sites}}, doi = {10.1002/cne.21319}, volume = {502}, year = {2007}, } @article{8483, abstract = {Atom-resolved real-time studies of kinetic processes in proteins have been hampered in the past by the lack of experimental techniques that yield sufficient temporal and atomic resolution. Here we present band-selective optimized flip-angle short transient (SOFAST) real-time 2D NMR spectroscopy, a method that allows simultaneous observation of reaction kinetics for a large number of nuclear sites along the polypeptide chain of a protein with an unprecedented time resolution of a few seconds. SOFAST real-time 2D NMR spectroscopy combines fast NMR data acquisition techniques with rapid sample mixing inside the NMR magnet to initiate the kinetic event. We demonstrate the use of SOFAST real-time 2D NMR to monitor the conformational transition of α-lactalbumin from a molten globular to the native state for a large number of amide sites along the polypeptide chain. The kinetic behavior observed for the disappearance of the molten globule and the appearance of the native state is monoexponential and uniform along the polypeptide chain. This observation confirms previous findings that a single transition state ensemble controls folding of α-lactalbumin from the molten globule to the native state. In a second application, the spontaneous unfolding of native ubiquitin under nondenaturing conditions is characterized by amide hydrogen exchange rate constants measured at high pH by using SOFAST real-time 2D NMR. Our data reveal that ubiquitin unfolds in a gradual manner with distinct unfolding regimes.}, author = {Schanda, Paul and Forge, V. and Brutscher, B.}, issn = {1091-6490}, journal = {Proceedings of the National Academy of Sciences}, keywords = {Multidisciplinary}, number = {27}, pages = {11257--11262}, publisher = {National Academy of Sciences}, title = {{Protein folding and unfolding studied at atomic resolution by fast two-dimensional NMR spectroscopy}}, doi = {10.1073/pnas.0702069104}, volume = {104}, year = {2007}, } @article{8484, abstract = {A series of sequential, intra-residue, and bi-directional BEST H–N–CA, H–N–CO, and H–N–CB pulse sequences is presented that extends the BEST concept introduced recently for fast multidimensional protein NMR [Schanda et al., J. Am. Chem. Soc. 128 (2006) 9042] to the complete set of experiments required for sequential resonance assignment. We demonstrate for the protein ubiquitin that 3D BEST H–N–C correlation spectra can be recorded on a 600 MHz NMR spectrometer equipped with a cryogenic probe in only a few minutes of acquisition time with sufficient sensitivity to detect all expected cross peaks.}, author = {Lescop, Ewen and Schanda, Paul and Brutscher, Bernhard}, issn = {1090-7807}, journal = {Journal of Magnetic Resonance}, number = {1}, pages = {163--169}, publisher = {Elsevier}, title = {{A set of BEST triple-resonance experiments for time-optimized protein resonance assignment}}, doi = {10.1016/j.jmr.2007.04.002}, volume = {187}, year = {2007}, } @article{8485, abstract = {High signal to noise is a necessity for the quantification of NMR spectral parameters to be translated into accurate and precise restraints on protein structure and dynamics. An important source of long-range structural information is obtained from 1H–1H residual dipolar couplings (RDCs) measured for weakly aligned molecules. For sensitivity reasons, such measurements are generally performed on highly deuterated protein samples. Here we show that high sensitivity is also obtained for protonated protein samples if the pulse schemes are optimized in terms of longitudinal relaxation efficiency and J-mismatch compensated coherence transfer. The new sensitivity-optimized quantitative J-correlation experiment yields important signal gains reaching factors of 1.5 to 8 for individual correlation peaks when compared to previously proposed pulse schemes.}, author = {Schanda, Paul and Lescop, Ewen and Falge, Mirjam and Sounier, Rémy and Boisbouvier, Jérôme and Brutscher, Bernhard}, issn = {0925-2738}, journal = {Journal of Biomolecular NMR}, keywords = {Spectroscopy, Biochemistry}, pages = {47--55}, publisher = {Springer Nature}, title = {{Sensitivity-optimized experiment for the measurement of residual dipolar couplings between amide protons}}, doi = {10.1007/s10858-006-9138-2}, volume = {38}, year = {2007}, } @article{8486, abstract = {A technique is described that allows reducing acquisition times of multidimensional NMR experiments by extensive spectral folding. The method is simple and has many interesting applications for NMR studies of molecular structure, dynamics, and kinetics.}, author = {Lescop, Ewen and Schanda, Paul and Rasia, Rodolfo and Brutscher, Bernhard}, issn = {0002-7863}, journal = {Journal of the American Chemical Society}, keywords = {Colloid and Surface Chemistry, Biochemistry, General Chemistry, Catalysis}, number = {10}, pages = {2756--2757}, publisher = {American Chemical Society}, title = {{Automated spectral compression for fast multidimensional NMR and increased time resolution in real-time NMR spectroscopy}}, doi = {10.1021/ja068949u}, volume = {129}, year = {2007}, } @article{8487, abstract = {Following unidirectional biophysical events such as the folding of proteins or the equilibration of binding interactions, requires experimental methods that yield information at both atomic-level resolution and at high repetition rates. Toward this end a number of different approaches enabling the rapid acquisition of 2D NMR spectra have been recently introduced, including spatially encoded “ultrafast” 2D NMR spectroscopy and SOFAST HMQC NMR. Whereas the former accelerates acquisitions by reducing the number of scans that are necessary for completing arbitrary 2D NMR experiments, the latter operates by reducing the delay between consecutive scans while preserving sensitivity. Given the complementarities between these two approaches it seems natural to combine them into a single tool, enabling the acquisition of full 2D protein NMR spectra at high repetition rates. We demonstrate here this capability with the introduction of “ultraSOFAST” HMQC NMR, a spatially encoded and relaxation-optimized approach that can provide 2D protein correlation spectra at ∼1 s repetition rates for samples in the ∼2 mM concentration range. The principles, relative advantages, and current limitations of this new approach are discussed, and its application is exemplified with a study of the fast hydrogen−deuterium exchange characterizing amide sites in Ubiquitin.}, author = {Gal, Maayan and Schanda, Paul and Brutscher, Bernhard and Frydman, Lucio}, issn = {0002-7863}, journal = {Journal of the American Chemical Society}, keywords = {Colloid and Surface Chemistry, Biochemistry, General Chemistry, Catalysis}, number = {5}, pages = {1372--1377}, publisher = {American Chemical Society}, title = {{UltraSOFAST HMQC NMR and the repetitive acquisition of 2D protein spectra at Hz rates}}, doi = {10.1021/ja066915g}, volume = {129}, year = {2007}, } @article{8511, abstract = {Here we study an amazing phenomenon discovered by Newhouse [S. Newhouse, Non-density of Axiom A(a) on S2, in: Proc. Sympos. Pure Math., vol. 14, Amer. Math. Soc., 1970, pp. 191–202; S. Newhouse, Diffeomorphisms with infinitely many sinks, Topology 13 (1974) 9–18; S. Newhouse, The abundance of wild hyperbolic sets and nonsmooth stable sets of diffeomorphisms, Publ. Math. Inst. Hautes Études Sci. 50 (1979) 101–151]. It turns out that in the space of Cr smooth diffeomorphisms Diffr(M) of a compact surface M there is an open set U such that a Baire generic diffeomorphism f ∈ U has infinitely many coexisting sinks. In this paper we make a step towards understanding “how often does a surface diffeomorphism have infinitely many sinks.” Our main result roughly says that with probability one for any positive D a surface diffeomorphism has only finitely many localized sinks either of cyclicity bounded by D or those whose period is relatively large compared to its cyclicity. It verifies a particular case of Palis’ Conjecture saying that even though diffeomorphisms with infinitely many coexisting sinks are Baire generic, they have probability zero. One of the key points of the proof is an application of Newton Interpolation Polynomials to study the dynamics initiated in [V. Kaloshin, B. Hunt, A stretched exponential bound on the rate of growth of the number of periodic points for prevalent diffeomorphisms I, Ann. of Math., in press, 92 pp.; V. Kaloshin, A stretched exponential bound on the rate of growth of the number of periodic points for prevalent diffeomorphisms II, preprint, 85 pp.].}, author = {Gorodetski, A. and Kaloshin, Vadim}, issn = {0001-8708}, journal = {Advances in Mathematics}, keywords = {General Mathematics}, number = {2}, pages = {710--797}, publisher = {Elsevier}, title = {{How often surface diffeomorphisms have infinitely many sinks and hyperbolicity of periodic points near a homoclinic tangency}}, doi = {10.1016/j.aim.2006.03.012}, volume = {208}, year = {2007}, } @article{8512, abstract = {For diffeomorphisms of smooth compact finite-dimensional manifolds, we consider the problem of how fast the number of periodic points with period n grows as a function of n. In many familiar cases (e.g., Anosov systems) the growth is exponential, but arbitrarily fast growth is possible; in fact, the first author has shown that arbitrarily fast growth is topologically (Baire) generic for C2 or smoother diffeomorphisms. In the present work we show that, by contrast, for a measure-theoretic notion of genericity we call “prevalence”, the growth is not much faster than exponential. Specifically, we show that for each ρ,δ>0, there is a prevalent set of C1+ρ (or smoother) diffeomorphisms for which the number of periodic n points is bounded above by exp(Cn1+δ) for some C independent of n. We also obtain a related bound on the decay of hyperbolicity of the periodic points as a function of n, and obtain the same results for 1-dimensional endomorphisms. The contrast between topologically generic and measure-theoretically generic behavior for the growth of the number of periodic points and the decay of their hyperbolicity show this to be a subtle and complex phenomenon, reminiscent of KAM theory. Here in Part I we state our results and describe the methods we use. We complete most of the proof in the 1-dimensional C2-smooth case and outline the remaining steps, deferred to Part II, that are needed to establish the general case. The novel feature of the approach we develop in this paper is the introduction of Newton Interpolation Polynomials as a tool for perturbing trajectories of iterated maps.}, author = {Kaloshin, Vadim and Hunt, Brian}, issn = {0003-486X}, journal = {Annals of Mathematics}, number = {1}, pages = {89--170}, publisher = {Princeton University Press}, title = {{Stretched exponential estimates on growth of the number of periodic points for prevalent diffeomorphisms I}}, doi = {10.4007/annals.2007.165.89}, volume = {165}, year = {2007}, } @article{860, abstract = {We identified a mutation in the CRYGD gene (P23S) of the γ-crystallin gene cluster that is associated with a polymorphic congenital cataract that occurs with frequency of ∼0.3% in a human population. To gain insight into the molecular mechanism of the pathogenesis of γ-crystallin isoforms, we undertook an evolutionary analysis of the available mammalian and newly obtained primate sequences of the γ-crystallin genes. The cataract-associated serine at site 23 corresponds to the ancestral state, since it was found in CRYGD of a lower primate and all the surveyed nonprimate mammals. Crystallin proteins include two structurally similar domains, and substitutions in mammalian CRYGD protein at site 23 of the first domain were always associated with substitutions in the structurally reciprocal sites 109 and 136 of the second domain. These data suggest that the cataractogenic effect of serine at site 23 in the N-terminal domain of CRYGD may be compensated indirectly by amino acid changes in a distal domain. We also found that gene conversion was a factor in the evolution of the γ-crystallin gene cluster throughout different mammalian clades. The high rate of gene conversion observed between the functional CRYGD gene and two primate γ-crystallin pseudogenes (CRYGEP1 and CRYGFP1) coupled with a surprising finding of apparent negative selection in primate pseudogenes suggest a deleterious impact of recently derived pseudogenes involved in gene conversion in the γ-crystallin gene cluster.}, author = {Plotnikova, Olga V and Fyodor Kondrashov and Vlasov, Peter K and Grigorenko, Anastasia P and Ginter, Evgeny K and Rogaev, Evgeny I}, journal = {American Journal of Human Genetics}, number = {1}, pages = {32 -- 43}, publisher = {Cell Press}, title = {{Conversion and compensatory evolution of the γ-crystallin genes and identification of a cataractogenic mutation that reverses the sequence of the human CRYGD gene to an ancestral state}}, doi = {10.1086/518616}, volume = {81}, year = {2007}, } @article{861, abstract = {Background: Mitochondrial tRNAs have been the subject of study for structural biologists interested in their secondary structure characteristics, evolutionary biologists have researched patterns of compensatory and structural evolution and medical studies have been directed towards understanding the basis of human disease. However, an up to date, manually curated database of mitochondrially encoded tRNAs from higher animals is currently not available. Description: We obtained the complete mitochondrial sequence for 277 tetrapod species from GenBank and re-annotated all of the tRNAs based on a multiple alignment of each tRNA gene and secondary structure prediction made independently for each tRNA. The mitochondrial (mt) tRNA sequences and the secondary structure based multiple alignments are freely available as Supplemental Information online. Conclusion: We compiled a manually curated database of mitochondrially encoded tRNAs from tetrapods with completely sequenced genomes. In the course of our work, we reannotated more than 10% of all tetrapod mt-tRNAs and subsequently predicted the secondary structures of 6060 mitochondrial tRNAs. This carefully constructed database can be utilized to enhance our knowledge in several different fields including the evolution of mt-tRNA secondary structure and prediction of pathogenic mt-tRNA mutations. In addition, researchers reporting novel mitochondrial genome sequences should check their tRNA gene annotations against our database to ensure a higher level of fidelity of their annotation.}, author = {Popadin, Konstantin Yu and Mamirova, Leila A and Fyodor Kondrashov}, journal = {BMC Bioinformatics}, publisher = {BioMed Central}, title = {{A manually curated database of tetrapod mitochondrially encoded tRNA sequences and secondary structures}}, doi = {10.1186/1471-2105-8-441}, volume = {8}, year = {2007}, } @article{879, abstract = {Having an extra copy of a gene is thought to provide some functional redundancy, which results in a higher rate of evolution in duplicated genes. In this article, we estimate the impact of gene duplication on the selection of tuf paralogs, and we find that in the absence of gene conversion, tuf paralogs have evolved significantly slower than when gene conversion has been a factor in their evolution. Thus, tuf gene copies evolve under a selective pressure that ensures their functional uniformity, and gene conversion reduces selection against amino acid substitutions that affect the function of the encoded protein, EF-Tu.}, author = {Fyodor Kondrashov and Gurbich, Tatiana A and Vlasov, Peter K}, journal = {Trends in Genetics}, number = {5}, pages = {215 -- 218}, publisher = {Elsevier}, title = {{Selection for functional uniformity of tuf duplicates in γ-proteobacteria}}, doi = {10.1016/j.tig.2007.03.002}, volume = {23}, year = {2007}, } @article{904, abstract = {Background: Independently evolving lineages mostly accumulate different changes, which leads to their gradual divergence. However, parallel accumulation of identical changes is also common, especially in traits with only a small number of possible states. Results: We characterize parallelism in evolution of coding sequences in three four-species sets of genomes of mammals, Drosophila, and yeasts. Each such set contains two independent evolutionary paths, which we call paths I and II. An amino acid replacement which occurred along path I also occurs along path II with the probability 50-8211;80% of that expected under selective neutrality. Thus, the per site rate of parallel evolution of proteins is several times higher than their average rate of evolution, but still lower than the rate of evolution of neutral sequences. This deficit may be caused by changes in the fitness landscape, leading to a replacement being possible along path I but not along path II. However, constant, weak selection assumed by the nearly neutral model of evolution appears to be a more likely explanation. Then, the average coefficient of selection associated with an amino acid replacement, in the units of the effective population size, must exceed ∼0.4, and the fraction of effectively neutral replacements must be below ∼30%. At a majority of evolvable amino acid sites, only a relatively small number of different amino acids is permitted. Conclusion: High, but below-neutral, rates of parallel amino acid replacements suggest that a majority of amino acid replacements that occur in evolution are subject to weak, but non-trivial, selection, as predicted by Ohta's nearly-neutral theory.}, author = {Bazykin, Georgii A and Fyodor Kondrashov and Brudno, Michael and Poliakov, Alexander V and Dubchak, Inna L and Kondrashov, Alexey S}, journal = {Biology Direct}, publisher = {BioMed Central}, title = {{Extensive parallelism in protein evolution}}, doi = {10.1186/1745-6150-2-20}, volume = {2}, year = {2007}, } @article{9149, abstract = {The interaction of tidal currents with sea-floor topography results in the radiation of internal gravity waves into the ocean interior. These waves are called internal tides and their dissipation due to nonlinear wave breaking and concomitant three-dimensional turbulence could play an important role in the mixing of the abyssal ocean, and hence in controlling the large-scale ocean circulation. As part of on-going work aimed at providing a theory for the vertical distribution of wave breaking over sea-floor topography, in this paper we investigate the instability of internal tides in a very simple linear model that helps us to relate the formation of unstable regions to simple features in the sea-floor topography. For two-dimensional tides over one-dimensional topography we find that the formation of overturning instabilities is closely linked to the singularities in the topography shape and that it is possible to have stable waves at the sea floor and unstable waves in the ocean interior above. For three-dimensional tides over two-dimensional topography there is in addition an effect of geometric focusing of wave energy into localized regions of high wave amplitude, and we investigate this focusing effect in simple examples. Overall, we find that the distribution of unstable wave breaking regions can be highly non-uniform even for very simple idealized topography shapes.}, author = {Bühler, Oliver and Muller, Caroline J}, issn = {0022-1120}, journal = {Journal of Fluid Mechanics}, keywords = {mechanical engineering, mechanics of materials, condensed matter physics}, pages = {1--28}, publisher = {Cambridge University Press}, title = {{Instability and focusing of internal tides in the deep ocean}}, doi = {10.1017/s0022112007007410}, volume = {588}, year = {2007}, } @article{7323, abstract = {The main factors for reducing the consumption of a vehicle are reduction of curb weight, air drag and increase in the drivetrain efficiency. Highly efficient drivetrains can be developed based on PEFC technology and curb weight may be limited by an innovative vehicle construction. In this paper, data on consumption and efficiency of a four‐place passenger vehicle with a curb weight of 850 kg and an H2/O2 fed PEFC/Supercap hybrid electric powertrain are presented. Hydrogen consumption in the New European Driving Cycle is 0.67 kg H2/100 km, which corresponds to a gasoline equivalent consumption of 2.5 l/100 km. When including the energy needed to supply pure oxygen, the calculated consumption increases from 0.67 to 0.69–0.79 kg H2/100 km, depending on the method of oxygen production.}, author = {Büchi, F. N. and Paganelli, G. and Dietrich, P. and Laurent, D. and Tsukada, A. and Varenne, P. and Delfino, A. and Kötz, R. and Freunberger, Stefan Alexander and Magne, P.-A. and Walser, D. and Olsommer, D.}, issn = {1615-6846}, journal = {Fuel Cells}, number = {4}, pages = {329--335}, publisher = {Wiley}, title = {{Consumption and efficiency of a passenger car with a Hydrogen/Oxygen PEFC based hybrid electric drivetrain}}, doi = {10.1002/fuce.200600050}, volume = {7}, year = {2007}, } @article{7324, abstract = {Efficiency is the key parameter for the application of fuel cells in automotive applications. The efficiency of a hydrogen/oxygen polymer electrolyte fuel cell system is analyzed and compared to hydrogen/air systems. The analysis is performed for the tank to electric power chain. Furthermore, the additional energy required for using pure oxygen as a second fuel is analyzed and included in the calculation. The results show that if hydrogen is produced from primary fossil energy carriers, such as natural gas and pure oxygen needs to be obtained by a conventional process; the fuel to electric current efficiency is comparable for hydrogen/oxygen and hydrogen/air systems. However, if hydrogen and oxygen are produced by the splitting of water, i.e., by electrolysis or by a thermochemical process, the fuel to electric current efficiency for the hydrogen/oxygen system is clearly superior.}, author = {Büchi, F. N. and Freunberger, Stefan Alexander and Reum, M. and Paganelli, G. and Tsukada, A. and Dietrich, P. and Delfino, A.}, issn = {1615-6846}, journal = {Fuel Cells}, number = {2}, pages = {159--164}, publisher = {Wiley}, title = {{On the efficiency of an advanced automotive fuel cell system}}, doi = {10.1002/fuce.200500257}, volume = {7}, year = {2007}, } @article{7325, abstract = {Our experimental results shown here disprove that finite diffusion can generally be assumed in ac impedance models for H2/air-polymer electrolyte fuel cells (PEFCs) to account for the diffusive transport of oxygen through the gas diffusion layer (GDL) toward the air electrode. It is shown that the amplitude of the oxygen concentration oscillation created as a consequence of superimposed ac current at the air electrode is not zero at the channel/GDL interface but extends into the gas channels, at least below modulation frequencies of fmod=10 Hz . By this, sinusoidal oxygen-concentration oscillations within the cathode gas channels are excited locally along the flow field. Due to the forced air convection in the cathode flow-field channels, a coupling via the gas phase occurs downstream of the flow field. The coupling strongly affects the local and by this the overall impedance response of the cell and evokes the formation of a low-frequency arc in H2/air-PEFC impedance spectra. Based on the experimental results, a qualitative model is presented explaining the local impedance response of a segmented 200cm2H2/air PEFC.}, author = {Schneider, I. A. and Freunberger, Stefan Alexander and Kramer, D. and Wokaun, A. and Scherer, G. G.}, issn = {0013-4651}, journal = {Journal of The Electrochemical Society}, number = {4}, publisher = {The Electrochemical Society}, title = {{Oscillations in gas channels: Part I. The forgotten player in impedance spectroscopy in PEFCs}}, doi = {10.1149/1.2435706}, volume = {154}, year = {2007}, } @article{7704, abstract = {Gradients of axon guidance molecules instruct the formation of continuous neural maps, such as the retinotopic map in the vertebrate visual system. Here we show that molecular gradients can also instruct the formation of a discrete neural map. In the fly olfactory system, axons of 50 classes of olfactory receptor neurons (ORNs) and dendrites of 50 classes of projection neurons (PNs) form one-to-one connections at discrete units called glomeruli. We provide expression, loss- and gain-of-function data to demonstrate that the levels of transmembrane Semaphorin-1a (Sema-1a), acting cell-autonomously as a receptor or part of a receptor complex, direct the dendritic targeting of PNs along the dorsolateral to ventromedial axis of the antennal lobe. Sema-1a also regulates PN axon targeting in higher olfactory centers. Thus, graded expression of Sema-1a contributes to connection specificity from ORNs to PNs and then to higher brain centers, ensuring proper representation of olfactory information in the brain.}, author = {Komiyama, Takaki and Sweeney, Lora Beatrice Jaeger and Schuldiner, Oren and Garcia, K. Christopher and Luo, Liqun}, issn = {0092-8674}, journal = {Cell}, number = {2}, pages = {399--410}, publisher = {Elsevier}, title = {{Graded expression of semaphorin-1a cell-autonomously directs dendritic targeting of olfactory projection neurons}}, doi = {10.1016/j.cell.2006.12.028}, volume = {128}, year = {2007}, } @article{7705, abstract = {Axon-axon interactions have been implicated in neural circuit assembly, but the underlying mechanisms are poorly understood. Here, we show that in the Drosophila antennal lobe, early-arriving axons of olfactory receptor neurons (ORNs) from the antenna are required for the proper targeting of late-arriving ORN axons from the maxillary palp (MP). Semaphorin-1a is required for targeting of all MP but only half of the antennal ORN classes examined. Sema-1a acts nonautonomously to control ORN axon-axon interactions, in contrast to its cell-autonomous function in olfactory projection neurons. Phenotypic and genetic interaction analyses implicate PlexinA as the Sema-1a receptor in ORN targeting. Sema-1a on antennal ORN axons is required for correct targeting of MP axons within the antennal lobe, while interactions amongst MP axons facilitate their entry into the antennal lobe. We propose that Sema-1a/PlexinA-mediated repulsion provides a mechanism by which early-arriving ORN axons constrain the target choices of late-arriving axons.}, author = {Sweeney, Lora Beatrice Jaeger and Couto, Africa and Chou, Ya-Hui and Berdnik, Daniela and Dickson, Barry J. and Luo, Liqun and Komiyama, Takaki}, issn = {0896-6273}, journal = {Neuron}, number = {2}, pages = {185--200}, publisher = {Elsevier}, title = {{Temporal target restriction of olfactory receptor neurons by semaphorin-1a/plexinA-mediated axon-axon interactions}}, doi = {10.1016/j.neuron.2006.12.022}, volume = {53}, year = {2007}, } @article{7753, abstract = {In many species, females show reduced expression of a trait that is under sexual selection in males, and this expression is thought to be maintained through genetic associations with the male phenotype. However, there is also the potential for the female trait to convey an advantage in intrasexual conflicts over resources. We tested this hypothesis in a feral population of Soay sheep, in which males and females have a polymorphism for horn development, producing either full (normal horned), reduced (scurred) or no (polled, females only) horns. During the lambing period, females who possessed horns were more likely to initiate and win aggressive interactions, independent of age, weight and birthing status. The occurrence of aggression was also context dependent, decreasing over the lambing period and associated with local density. Our results demonstrate that a trait that confers benefits to males during intrasexual competition for mates may also be used by females in intrasexual competition over resources: males use weaponry to gain mates, whereas females use weaponry to gain food.}, author = {Robinson, Matthew Richard and Kruuk, Loeske E.B}, issn = {1744-9561}, journal = {Biology Letters}, number = {6}, pages = {651--654}, publisher = {The Royal Society}, title = {{Function of weaponry in females: The use of horns in intrasexual competition for resources in female Soay sheep}}, doi = {10.1098/rsbl.2007.0278}, volume = {3}, year = {2007}, } @article{7780, abstract = {We used single-channel electrical recordings and Langevin molecular dynamics simulations to explore the electrophoretic translocation of various β-hairpin peptides across the staphylococcal α-hemolysin (αHL) protein pore at single-molecule resolution. The β-hairpin peptides, which varied in their folding properties, corresponded to the C terminal residues of the B1 domain of protein G. The translocation time was strongly dependent on the electric force and was correlated with the folding features of the β-hairpin peptides. Highly unfolded peptides entered the pore in an extended conformation, resulting in fast single-file translocation events. In contrast, the translocation of the folded β-hairpin peptides occurred more slowly. In this case, the β-hairpin peptides traversed the αHL pore in a misfolded or fully folded conformation. This study demonstrates that the interaction between a polypeptide and a β-barrel protein pore is dependent on the folding features of the polypeptide. }, author = {Goodrich, Carl Peter and Kirmizialtin, Serdal and Huyghues-Despointes, Beatrice M. and Zhu, Aiping and Scholtz, J. Martin and Makarov, Dmitrii E. and Movileanu, Liviu}, issn = {1520-6106}, journal = {The Journal of Physical Chemistry B}, number = {13}, pages = {3332--3335}, publisher = {American Chemical Society}, title = {{Single-molecule electrophoresis of β-hairpin peptides by electrical recordings and Langevin dynamics simulations}}, doi = {10.1021/jp071364h}, volume = {111}, year = {2007}, }