| 1. |
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| 2. |
- Eriksson, Jonas, et al.
(författare)
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7-deaza-2 '-deoxyadenosine-5 '-triphosphate as an alternative nucleotide for the pyrosequencing technology
- 2004
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Ingår i: Nucleosides, Nucleotides & Nucleic Acids. - : Marcel Dekker. - 1525-7770 .- 1532-2335. ; 23:10, s. 1583-1594
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Tidskriftsartikel (refereegranskat)abstract
- A new adenosine nucleotide analog suitable for the Pyrosequencing method is presented. The new analog, 7-deaza-2'-deoxyadenosine-5'-triphosphate (c(7)dATP), has virtually the. same low substrate specificity for luciferase as the currently used analog, 2'-deoxyadenosine-5'-O-(1-thiotriphosphate) (dATPalphaS). The inhibitory effect dATPalphaS displays on the nucleotide degrading activity of apyrase was reduced significantly by substituting the c(7)dATP for the dATPalphaS. Both analogs show high stability after long time storage at +8degreesC. Furthermore, with the new nucleotide a read length of up to 100 bases was obtained for several templates from fungi, bacteria and viruses.
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| 3. |
- Friberg, Urban, et al.
(författare)
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Fitness effects of female mate choice : preferred males are detrimental for Drosophila melanogaster females
- 2003
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Ingår i: Journal of Evolutionary Biology. - : John Wiley & Sons. - 1010-061X .- 1420-9101. ; 16, s. 797-811
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of female mate choice, broadly defined to include any female behaviour or morphology which biases matings towards certain male phenotypes, is traditionally thought to result from direct or indirect benefits which females acquire when mating with preferred males. In contrast, new models have shown that female mate choice can be generated by sexual conflict, where preferred males may cause a fitness depression in females. Several studies have shown that female Drosophila melanogaster bias matings towards large males. Here, we use male size as a proxy for male attractiveness and test how female fitness is affected by reproducing with large or small males, under two different male densities. Females housed with large males had reduced lifespan and aged at an accelerated rate compared with females housed with small males, and increased male density depressed female fitness further. These fitness differences were due to effects on several different fitness components. Female fitness covaried negatively with male courtship rate, which suggests a cost of courtship. Mating rate increased with male size, whereas female fitness peaked at an intermediate mating rate. Our results suggest that female mate choice in D. melanogaster is, at least in part, a by-product of sexual conflict over the mating rate.
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| 4. |
- Gavrilets, Sergey, et al.
(författare)
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The evolution of female mate choice by sexual conflict
- 2001
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Ingår i: Proceedings of the Royal Society of London Series B. - London : The Roylal Society. - 0080-4649 .- 0962-8452 .- 1471-2954. ; 268:1466, s. 531-539
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Tidskriftsartikel (refereegranskat)abstract
- Although empirical evidence has shown that many male traits have evolved via sexual selection by female mate choice, our understanding of the adaptive value of female mating preferences is still very incomplete. It has recently been suggested that female mate choice may result from females evolving resistance rather than attraction to males, but this has been disputed. Here, we develop a quantitative genetic model showing that sexual conflict over mating indeed results in the joint evolution of costly female mate choice and exaggerated male traits under a wide range of circumstances. In contrast to traditional explanations of costly female mate choice, which rely on indirect genetic benefits, our model shows that mate choice can be generated as a side–effect of females evolving to reduce the direct costs of mating.
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| 5. |
- Persson, Gerd, et al.
(författare)
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Phase Behavior of 1-Alkylpyridinium Octane-1-sulfonates : Effect of the 1-Alkylpyridinium Counterion Size
- 2004
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:4, s. 1168-1179
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Tidskriftsartikel (refereegranskat)abstract
- The temperature-versus-composition phase diagrams of eight different 1-alkylpyridinium octane-1-sulfonates (APOSs) in water were studied by 1H NMR, 2H NMR, pulsed gradient spin−echo NMR, small-angle X-ray diffraction, differential scanning calorimetry, surface tension and conductivity measurements, and polarizing microscopy. The number of carbons (nc) in the hydrocarbon chain of the pyridinium counterions was varied from nc = 1 to nc = 8 to study how the phase behavior of the APOS/2H2O systems was affected by a change in the chain length of the counterion. The sodium octane-1-sulfonate (NaOS)/water system was used as a reference. This system formed an isotropic micellar solution (L1) phase and a normal hexagonal (HI) phase. All APOSs were readily soluble in water and formed L1 phases. The surface tension above the critical micelle concentration for nc between 1 and 3 was higher than that for NaOS, and it decreased steadily for the different APOSs with increasing chain length. The area per molecule at the air/solution interfaces was rather constant at 68 Å2 for nc between 1 and 7. For 1-octylpyridinium octane-1-sulfonate (OPOS), it was about 5 Å2 smaller, which was just outside the estimated error. However, the smallest area was obtained for NaOS. At higher surfactant concentrations, liquid crystalline phases formed. Both cubic and HI phases were found for nc = 1 and 2, while for nc between 3 and 5 only an HI phase was observed. HI and lamellar liquid crystalline (Lα) phases formed for nc = 6 and 7. The only liquid crystalline phase found in the OPOS system was a Lα phase. The NaOS HI phase was the only liquid crystalline phase that showed a linear relation between the 2H2O NMR quadrupolar splitting (ΔW) and Xsurf/XW, where Xsurf and XW are the mole fractions of surfactant and water. The OPOS lamellae were found to be much thinner than expected, indicating a defect lamellar structure. This was further supported by the behavior of the quadrupolar splitting of deuterated OPOS. The anomalous behaviors of the 2H2O NMR quadrupolar splitting observed in the Lα phases of 1-heptylpyridinium octane-1-sulfonate and OPOS were interpreted in terms of changes in the population of the water molecules residing in different sites combined with a continuous rearrangement of the lamellae surface with the possible development of holes. The appearances of the phase diagrams were discussed in terms of surfactant molecular geometry and the packing of the amphiphiles in the aggregates formed.
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| 6. |
- Häggkvist, Roland, 1950-, et al.
(författare)
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A Monte Carlo sampling scheme for the Ising model
- 2004
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Ingår i: Journal of statistical physics. - : Springer. - 0022-4715 .- 1572-9613. ; 114:02-jan, s. 455-480
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we describe a Monte Carlo sampling scheme for the Ising model and similar discrete-state models. The scheme does not involve any particular method of state generation but rather focuses on a new way of measuring and using the Monte Carlo data. We show how to reconstruct the entropy S of the model, from which, e.g., the free energy can be obtained. Furthermore we discuss how this scheme allows us to more or less completely remove the effects of critical fluctuations near the critical temperature and likewise how it reduces critical slowing down. This makes it possible to use simple state generation methods like the Metropolis algorithm also for large lattices.
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| 7. |
- Häggkvist, Roland, 1950-, et al.
(författare)
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Computation of the Ising partition function for two-dimensional square grids
- 2004
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - New York : American Physical Society through the American Institute of Physics. - 1063-651X .- 1095-3787. ; 69:4
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Tidskriftsartikel (refereegranskat)abstract
- An improved method for obtaining the Ising partition function of nxn square grids with periodic boundary is presented. Our method applies results from Galois theory in order to split the computation into smaller parts and at the same time avoid the use of numerics. Using this method we have computed the exact partition function for the (320x320) grid, the (256x256) grid, and the (160x160) grid, as well as for a number of smaller grids. We obtain scaling parameters and compare with what theory prescribes.
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| 8. |
- Thidholm, Ellinor, et al.
(författare)
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Novel approach reveals localisation and assembly pathway of the PsbS and PsbW proteins into the photosystem II dimer
- 2002
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Ingår i: FEBS LETTERS. - 0014-5793 .- 1873-3468. ; 513:2-3, s. 217-22
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Tidskriftsartikel (refereegranskat)abstract
- A blue-native gel electrophoresis system was combined with an in organello import assay to specifically analyse the location and assembly of two nuclear-encoded photosystem 11 (PSII) subunits. With this method we were able to show that initially the low molecular mass PsbW protein is not associated with the monomeric form of PSII. Instead a proportion of newly imported PsbW is directly assembled in dimeric PSH super-complexes with very fast kinetics; its negatively charged N-terminal domain is essential for this process. The chlorophyll-binding PsbS protein, which is involved in energy dissipation, is first detected in the monomeric PSII subcomplexes, and only at later time points in the dimeric form of PSII. It seems to be bound tighter to the PSII core complex than to light harvesting complex II. These data point to radically different assembly pathways for different PSII subunits. (C) 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.
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| 9. |
- Engström, Christian, et al.
(författare)
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Numerical methods for homogenization of Maxwell's equations
- 2004
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Ingår i: URSI 2004 International Symposium on Electromagnetic Theory. - : Pisa University Press. - 8884922526 - 9788884922526 ; , s. 987-989
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Konferensbidrag (refereegranskat)abstract
- When the wavelength is much larger than the typical scale of the microstructure in a material, it is possible to define effective or homogenized material coefficients. Two numerical methods for the determination of the homogenized coefficients are compared. Numerical examples, where extreme properties of the effective material are achieved in the two dimensional case, are presented.
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| 10. |
- Jass, Jana, et al.
(författare)
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Physical properties of Escherichia coli P pili measured by optical tweezers
- 2004
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Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 87:6, s. 4271-4283
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical behavior of individual P pili of uropathogenic Escherichia coli has been investigated using optical tweezers. P pili, whose main part constitutes the PapA rod, composed of approximately 10(3) PapA subunits in a helical arrangement, are distributed over the bacterial surface and mediate adhesion to host cells. They are particularly important in the pathogenesis of E. coli colonizing the upper urinary tract and kidneys. A biological model system has been established for in situ measurements of the forces that occur during mechanical stretching of pili. A mathematical model of the force-versus-elongation behavior of an individual pilus has been developed. Three elongation regions of pili were identified. In region I, P pili stretch elastically, up to a relative elongation of 16 +/- 3%. The product of elasticity modulus and area of a P pilus, EA, was assessed to 154 +/- 20 pN (n=6). In region II, the quaternary structure of the PapA rod unfolds under a constant force of 27 +/- 2 pN (n approximately 100) by a sequential breaking of the interactions between adjacent layers of PapA subunits. This unfolding can elongate the pilus up to 7 +/- 2 times. In region III, pili elongate in a nonlinear manner as a result of stretching until the bond ruptures.
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