| 1. |
- Ahlford, Katrin, et al.
(författare)
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Rhodium-catalyzed asymmetric transfer hydrogenation of alkyl and aryl ketones in aqueous media
- 2008
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Ingår i: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 10:8, s. 832-835
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Tidskriftsartikel (refereegranskat)abstract
- A novel lipophilic rhodium catalyst was evaluated in the enantioselective transfer hydrogenation of ketones in water using sodium formate as the hydride donor, and in the presence of sodium docecylsulfonate. Alkyl alkyl ketones were reduced in good yields and in moderate to good enantioselectivities, and the reduction of aryl alkyl ketones proceeded with excellent enantioselectivity (up to 97% ee).
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| 2. |
- Ahlner, Alexandra, 1984-
(författare)
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Improved Methods for Characterization of Protein Dynamics by NMR spectroscopy and Studies of the EphB2 Kinase Domain
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Proteins are essential for all known forms of life and in many lethal diseases protein failure is the cause of the disease. To understand proteins and the processes they are involved in, it is valuable to know their structures as well as their dynamics and interactions. The structures may not be directly inspected because proteins are too small to be visible in a light microscope, which is why indirect methods such as nuclear magnetic resonance (NMR) spectroscopy have to be utilized. This method provides atomic information about the protein and, in contrast to other methods with similar resolution, the measurements are performed in solution resulting in more physiological conditions, enabling analysis of dynamics. Important dynamical processes are the ones on the millisecond timeframe, which may contribute to interactions of proteins and their catalysis of chemical reactions, both of significant value for the function of the proteins.To better understand proteins, not only do we need to study them, but also develop the methods we are using. This thesis presents four papers about improved NMR techniques as well as a fifth where the kinase domain of ephrinB receptor 2 (EphB2) has been studied regarding the importance of millisecond dynamics and interactions for the activation process. The first paper presents the software COMPASS, which combines statistics and the calculation power of a computer with the flexibility and experience of the user to facilitate and speed up the process of assigning NMR signals to the atoms in the protein. The computer program PINT has been developed for easier and faster evaluation of NMR experiments, such as those that evaluate protein dynamics. It is especially helpful for NMR signals that are difficult to distinguish, so called overlapped peaks, and the soft- ware also converts the detected signals to the indirectly measured physical quantities, such as relaxation rate constants, principal for dynamics. Next are two new versions of the Carr-Purcell-Maiboom-Gill (CPMG) dispersion pulse sequences, designed to measure millisecond dynamics in a way so that the signals are more separated than in standard experiments, to reduce problems with overlaps. To speed up the collection time of the data set, a subset is collected and the entire data set is then reconstructed, by multi-dimensional decomposition co-processing. Described in the thesis is also a way to produce suitably labeled proteins, to detect millisecond dynamics at Cα positions in proteins, using the CPMG dispersion relaxation experiment at lower protein concentrations. Lastly, the kinase domain of EphB2 is shown to be more dynamic on the millisecond time scale as well as more prone to interact with itself in the active form than in the inactive one. This is important for the receptor function of the protein, when and how it mediates signals.To conclude, this work has extended the possibilities to study protein dynamics by NMR spectroscopy and contributed to increased understanding of the activation process of EphB2 and its signaling mechanism.
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| 3. |
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| 4. |
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| 5. |
- Andersson, August, et al.
(författare)
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Magnetic resonance investigations of lipid motion in isotropic bicelles
- 2005
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 21:7, s. 7702-7709
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of DMPC in different isotropic bicelles have been investigated by NMR and EPR methods. The local dynamics were obtained by interpretation of 13C NMR relaxation measurements of DMPC in the bicelles, and these results were compared to EPR spectra of spin-labeled lipids. The overall size of the bicelles was investigated by PFG NMR translational diffusion measurements. The dynamics and relative sizes were compared among three different bicelles: [DMPC]/[DHPC] = 0.25, [DMPC]/[DHPC] = 0.5, and [DMPC]/[CHAPS] = 0.5. The local motion is found to depend much more strongly on the choice of the detergent, rather than the overall size of the bicelle. The results provide an explanation for differences in apparent dynamics for different peptides, which are bound to bicelles. This in turn determines under what conditions reasonable NMR spectra can be observed. A model is presented in which extensive local motion, in conjunction with the overall size, affects the spectral properties. An analytical expression for the size dependence of the bicelles, relating the radius of the bilayer region with physical properties of the detergent and the lipid, is also presented.
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| 6. |
- Andersson, August, 1974-
(författare)
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The Application of isotropic bicelles as model membranes
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Isotropic bicelles are disc-shaped aggregates of lipids and detergents, and are suitable model systems for high-resolution NMR studies of membrane-interacting peptides. In this thesis the structures for the two peptides motilin and transportan were determined by homonuclear 1H methods in the presence of bicelles, and the structure of the bovine prion protein peptide (bPrPp) was solved in the presence of DHPC micelles. All of these peptides were found to be largely a-helical when bound to the model membranes. In subsequent experiments both motilin and transportan were shown to reside on the surface of the bicelles, whereas bPrPp is more likely to have a transmembrane configuration. NMR translational diffusion experiments revealed that the isotropic bicelles studied here are very large objects compared to what is regularly indicated by high-resolution NMR spectroscopy. Furthermore, these studies showed that all three peptides examined interact strongly with bicelles. Investigation of the NMR-relaxation of labeled sites in the peptides motilin and penetratin demonstrated that the overall rotational correlation times for these peptides do not reflect the bicellar size. Such decoupling of NMR relaxation from the dependence of overall size is also seen for the dynamics of the lipid molecules in the bicelles. It is therefore concluded that the overall size is not the sole determinant of the linewidths in NMR spectra, but that extensive motions within the bicelles also exert significant effects. Another interesting observation is that the membrane-bound structures of the peptides motilin, transportan, penetratin and bPrPp are very similar, even though these peptides have very different biological functions. In contrast, considerably more variation is observed in the membrane-positioning and molecular dynamics of these peptides. Since the bicelles have been found to induce differences in membrane positioning and molecular dynamics compared to micelles, these model membranes are likely to be important in order to enhance our understanding of the biological function of membrane interacting peptides.
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| 7. |
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| 8. |
- Andrésen, Cecilia
(författare)
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Protein Structure and Interaction in Health and Disease
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on protein structure, dynamics and interaction and their relation to human disease. In particular, the biophysical and structural properties of both well-ordered and partially disordered proteins are studied using a range of biophysical techniques such as circular dichroism spectroscopy, fluorescence spectroscopy, mass spectrometry and nuclear magnetic resonance spectroscopy. Pseudomonas aeruginosa is a human pathogen due to its multidrug resistance (MDR) caused by overexpression of efflux pump systems. This thesis describes how MDR mutations within the MexR repressor of the MexAB-OprM system reduce the DNA affinity by altering its stability with maintained structure. The oncogenic protein c-Myc is involved in many essential biological functions such as cell proliferation, differentiation and apoptosis and is also highly associated with several forms of human cancers, and where the N-terminal domain is regulated by a plethora of protein interactions. In this thesis the intrinsically disordered N-terminal part of c-Myc and its interactions with the proteins Bin1 and TBP are described. Myc binds Bin1 with maintained disorder in a multivalent manner, which may explain why the onco-protein can interact with such a wide range of binding partners. A similarly dynamic interaction is observed for Myc with the TATA-binding protein (TBP). The essential human multidomain glutaredoxin Grx3 is associated with several biological functions such as redox signaling, proliferation and signal transduction. We have solved the structure and analyzed the dynamic properties in the ps-ns and ms time scale for the two N-terminal domains, providing a platform for further analysis of the Grx3 protein and its interactions. Taken together, this thesis emphasizes the importance of joint structural, biophysical and dynamic studies to better understand protein function in health and disease.
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| 9. |
- Ariöz, Candan, 1983-, et al.
(författare)
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Anionic Lipid Binding to the Foreign Protein MGS Provides a Tight Coupling between Phospholipid Synthesis and Protein Overexpression in Escherichia coli
- 2013
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 52:33, s. 5533-5544
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Tidskriftsartikel (refereegranskat)abstract
- Certain membrane proteins involved in lipid synthesis can induce formation of new intracellular membranes in Escherichia coli, i.e., intracellular vesicles. Among those, the foreign monotopic glycosyltransferase MGS from Acholeplasma laidlawii triggers such massive lipid synthesis when overexpressed. To examine the mechanism behind the increased lipid synthesis, we investigated the lipid binding properties of MGS in vivo together with the correlation between lipid synthesis and MGS overexpression levels. A good correlation between produced lipid quantities and overexpressed MGS protein was observed when standard LB medium was supplemented with four different lipid precursors that have significant roles in the lipid biosynthesis pathway. Interestingly, this correlation was highest concerning anionic lipid production and at the same time dependent on the selective binding of anionic lipid molecules by MGS. A selective interaction with anionic lipids was also observed in vitro by P-31 NMR binding studies using bicelles prepared with E. coli lipids. The results clearly demonstrate that the discriminative withdrawal of anionic lipids, especially phosphatidylglycerol, from the membrane through MGS binding triggers an in vivo signal for cells to create a feed-forward stimulation of lipid synthesis in E. coil. By this mechanism, cells can produce more membrane surface in order to accommodate excessively produced MGS molecules, which results in an interdependent cycle of lipid and MGS protein synthesis.
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| 10. |
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