| 1. |
- Noresson, A. L., et al.
(författare)
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Designing interactions by control of protein-ligand complex conformation : Tuning arginine-arene interaction geometry for enhanced electrostatic protein-ligand interactions
- 2018
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Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 9:4, s. 1014-1021
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Tidskriftsartikel (refereegranskat)abstract
- We investigated galectin-3 binding to 3-benzamido-2-O-sulfo-galactoside and -thiodigalactoside ligands using a combination of site-specific mutagenesis, X-ray crystallography, computational approaches, and binding thermodynamics measurements. The results reveal a conformational variability in a surface-exposed arginine (R144) side chain in response to different aromatic C3-substituents of bound galactoside-based ligands. Fluorinated C3-benzamido substituents induced a shift in the side-chain conformation of R144 to allow for an entropically favored electrostatic interaction between its guanidine group and the 2-O-sulfate of the ligand. By contrast, binding of ligands with non-fluorinated substituents did not trigger a conformational change of R144. Hence, a sulfate-arginine electrostatic interaction can be tuned by the choice of ligand C3-benzamido structures to favor specific interaction modes and geometries. These results have important general implications for ligand design, as the proper choice of arginine-aromatic interacting partners opens up for ligand-controlled protein conformation that in turn may be systematically exploited in ligand design.
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| 2. |
- Bässler, M., et al.
(författare)
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Beam line I411 at MAX II - Performance and first results
- 2001
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0168-9002. ; 469:3, s. 382-393
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Tidskriftsartikel (refereegranskat)abstract
- We report on the characteristics and first results from the soft X-ray beam line I411, based on an undulator at the third generation synchrotron facility MAX II, Sweden. The beam line is designed for high-resolution, angle-resolved electron spectroscopy on gases, liquids and solids. Main components are the modified SX700 monochromator and the end station, both of which were previously used at beam line 51 at MAX I. The end station is equipped with a rotatable SES-200 hemispherical electron-analyser. Before the end station, a one-metre section is reserved for exchangeable experimental set-ups. The usable photon energy range is 50-1500 eV and the photon flux is two orders of magnitudes higher compared to beam line 51. At 400 eV a resolving power of about 5700 in the first order of the monochromator grating could be obtained. In gas phase, a total electron energy resolution of 16 meV has been achieved. Detailed results on the undulator performance, flux, photon and electron energy resolution as well as some technical details are presented here. As an example of the capabilities of the beam line I411, we present the fully vibrationally resolved Auger resonant Raman electron spectrum of gas-phase N 2.
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| 3. |
- Stenslokken, K. O., et al.
(författare)
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Adenosinergic and cholinergic control mechanisms during hypoxia in the epaulette shark (Hemiscyllium ocellatum), with emphasis on branchial circulation
- 2004
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 207:25, s. 4451-4461
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Tidskriftsartikel (refereegranskat)abstract
- Coral reef platforms may become hypoxic at night during low tide. One animal in that habitat, the epaulette shark (Hemiscyllium ocellatum), survives hours of severe hypoxia and at least one hour of anoxia. Here, we examine the branchial effects of severe hypoxia (<0.3 mg oxygen 1(-1) for 20 min in anaesthetized epaulette shark), by measuring ventral and dorsal aortic blood pressure (P-VA and P-DA), heart rate (fH), and observing gill microcirculation using epi-illumination microscopy. Hypoxia induced a flow of blood in two parallel blood vessels, termed longitudinal vessels, in the outer borders of the free tip of the gill filament. Hypoxia also induced significant falls in fH, P-VA and P-DA, and a biphasic change in ventilation frequency (increase followed by decrease). Adenosine injection (1 mumol kg(-1)) also initiated blood flow in the longitudinal vessels, in addition to significant drops in P-VA, P-DA and fH, and a biphasic response in ventilation frequency (decrease followed by increase) indicating that adenosine influences ventilation. Aminophylline (10 mg kg(-1)), an A(1) and A(2) adenosine receptor antagonist, blocked the effects of adenosine injection, and also significantly reduced blood flow in the longitudinal vessels during hypoxia. In the second part of the study, we examined the cholinergic influence on the cardiovascular circulation during severe hypoxia (<0.3 mg 1(-1)) using antagonists against muscarinic (atropine 2 mg kg(-1)) and nicotinic (tubocurarine 5 mg kg(-1)) receptors. Injection of acetylcholine (ACh; 1 mumol kg(-1)) into the ventral aorta caused a marked fall in fH, a large increase in P-VA, but small changes in P-DA (suggesting increased R-gill. Atropine was able to inhibit the branchial vascular responses to ACh but not the hypoxic bradycardia, suggesting the presence of muscarinic receptors on the heart and gill vasculature, and that the hypoxia induced bradyeardia is of non-cholinergic origin. The results suggest that adenosine mediates increases in the arterio-venous circulation in the gill during hypoxia. This may serve to increase blood supply to heart and gill tissue.
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| 4. |
- Stensløkken, K.-O., et al.
(författare)
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Endothelin receptors in teleost fishes: cardiovascular effects and branchial distribution
- 2006
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Ingår i: Am J Physiol. - : American Physiological Society. ; 290:3
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Tidskriftsartikel (refereegranskat)abstract
- By observing gill blood flow using epi-illuminating microscopy, in parallel with cardiovascular recordings and immunohistochemistry, we have tried to identify the receptor mediating endothelin (ET) type 1 (ET1)-induced pillar cell contraction in the lamellae of the Atlantic cod (Gadus morhua). Intra-arterial injection of the specific ETB receptor agonist BQ-3020 induced dose-dependent increases in ventral aortic blood pressure, gill vascular resistance, and pillar cell area (indicating contraction). The specific ETA receptor antagonist BQ-610 did not prevent either pillar cell contraction or increased gill vascular resistance induced by ET-1 injection. The cardiovascular responses were corroborated by the detection of ETB receptor-like immunoreactivity (IR) associated with pillar cells in the lamellar region and in neuroendocrine cells. ETB receptor-like IR was also found lining the muscle layer of lamellar arterioles and filament arteries. In contrast, strong ETA receptor-like IR was found on branchial nerves throughout the filaments. In addition, ET-like IR was concentrated in neuroendocrine cells in the filament and lamellae. We also present data suggesting that ET-mediated pillar cell contraction is widespread among teleost fish, including Atlantic cod, rainbow trout (Oncorhynchus mykiss), sculpin (Myoxocephalus scorpius), and mackerel (Scomber scombrus). Taken together, our results suggest that an ETB-like receptor mediates pillar cell contraction in fishes, whereas ETA-like receptors may serve another function in the gill, inasmuch as ETA receptor-like IR is found on branchial nerves
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| 5. |
- Roth, O., et al.
(författare)
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Male mate choice relies on major histocompatibility complex class I in a sex-role-reversed pipefish
- 2014
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 27:5, s. 929-938
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Tidskriftsartikel (refereegranskat)abstract
- Mate choice for compatible genes is often based on genes of the major histocompatibility complex (MHC). Although MHC-based mate choice is commonly observed in female choice, male mate choice remains elusive. In particular, if males have intense paternal care and are thus the choosing sex, male choice for females with dissimilar MHC can be expected. Here, we investigated whether male mate choice relies on MHC class I genes in the sex-role reversed pipefish Syngnathus typhle. In a mate choice experiment, we determined the relative importance of visual and olfactory cues by manipulating visibility and olfaction. We found that pipefish males chose females that maximize sequence-based amino acid distance between MHC class I genotypes in the offspring when olfactory cues were present. Under visual cues, large females were chosen, but in the absence of visual cues, the choice pattern was reversed. The use of sex-role reversed species thus revealed that sexual selection can lead to the evolution of male mate choice for MHC class I genes.
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| 6. |
- Sorensen, S. L., et al.
(författare)
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Femtosecond pump-probe photoelectron spectroscopy of predissociative Rydberg states in acetylene
- 2000
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 112:18, s. 8038-8042
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Tidskriftsartikel (refereegranskat)abstract
- We employ a pump-probe approach to molecular photoionization to study fast dissociation of Rydberg states in acetylene. By using time-resolved photoelectron spectroscopy to study the electronic state of the resulting ions we are able to monitor the system continuously during dissociation or rearrangement. We find that the predissociative lifetime for the 3R‴ (v′2 = 1) Rydberg state is about 150 fs. We demonstrate a powerful new technique using time-correlated femtosecond harmonic generation and laser light pulses to study the time evolution of ultrafast dynamic processes in molecules.
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