196,908 research outputs found
Gel characteristics-waterbinding properties of blood plasma gels and methodological aspects on the waterbinding of gel systems
No full textDFT-based multi-scale modelling of materials and nanoparticles
No full textRedox-active metal oxide surfaces and interfaces ‒ such as electrodes, catalysts, and sensors ‒ play crucial roles in our society and in the development of new materials and greener technologies. In the scientific literature, a full arsenal of experimental methods are being used to help to characterize such materials interfaces. Simultaneously, the (ever-increasing) theoretical materials studies in the literature provide structural and mechanistic information at a detail that is difficult to beat by experiments – but are the models accurate enough? There are at least two major challenges in materials modelling: (i) how to build structural models that capture the complexity and imperfections of the real systems, and (ii) how to find good enough interaction models (say a DFT functional [1] or a force-field). Here mimicking the interactions and chemical properties of materials without explicit electrons present is a formidable task, especially when the transfer of electrons is closely coupled to the material's functionality, as is the case for redox-active metal oxides.I will discuss some of our efforts in the development of a multiscale modelling approach for surfaces and interfaces of metal oxides (e.g. CeO2, ZnO, MgO) – with and without interacting molecules (e.g. O2 and water).In summary, we combine a range of theoretical methods including DFT [2], tight-binding-DFT [3], and reactive force-field simulations [4] in a consistent multi-scale approach to examine the properties of oxide nanosystems. We generate images and spectra to make direct comparisons with the experimental counterparts (e.g. IRRAS spectra [5]), but we also generate properties that cannot be measured by experiments such as the water dipole moment enhancement on a surface (often much larger [1] than in liquid water!). I will also inform about the European Materials Modelling Council (https://emmc.info/), and our efforts to promote the use and quality of materials modelling in industry; the EMMC is open to everyone interested. References[1] G. G. Kebede, D. Spångberg, P. D. Mitev, P. Broqvist, K. Hermansson, "Comparing van der Waals DFT methods for water on NaCl(001) and MgO(001), The Journal of Chemical Physics 146, 064703 (2017). [2] M. Hellström, D. Spångberg, K. Hermansson, "Treatment of Delocalized Electron Transfer in Periodic and Embedded Cluster DFT Calculations: The Case of Cu on ZnO (10-10)", Journal of Computational Chemistry 36, 2394 (2015). [3] J. Kullgren, M. J. Wolf, K. Hermansson, Ch. Köhler, B. Aradi,Th. Frauenheim, and P. Broqvist, "Self-Consistent-Charge Density-Functional Tight-Binding (SCC-DFTB) Parameters for Ceria in 0D to 3D". J. Phys. Chem. C 121, 4593−4607 (2017). [4] P. Broqvist, J. Kullgren, M. J. Wolf, A. C. T. van Duin, K. Hermansson, "A ReaxFF force-field for ceria bulk, surfaces and nanoparticles", J. Phys. Chem. C 119, 13598 (2015). [5] S. Hu, Z. Wang, A. Mattsson, L. Österlund, K. Hermansson, "Simulation of IRRAS Spectra for Molecules on Oxide Surfaces: CO on TiO2(110)", J. Phys. Chem. C 119, 5403 (2015).</p
Multiscale modelling of metal oxide interfaces and nanoparticles
No full textRedox-active metal oxide surfaces and interfaces ‒ such as electrodes, catalysts, and sensors ‒ play crucial roles in our society and in the development of new materials and greener technologies. In the scientific literature, a full arsenal of experimental methods are being used to help characterize such interfaces. At the same time, the number of theoretical studies in the literature steadily increases, providing mechanistic information at a detail that is hard to beat by experiment. Are such theoretical results accurate enough? Here the major challenges are (i) how to build a structural model that captures the complexity and imperfections of the real system at hand, and (ii) how to find an interaction model/a materials relation (say a DFT functional [1] or a force-field) that is good enough.A 5 nm metal oxide nanoparticle may be very small to an experimentalist, but it contains many thousand atoms, making standard quantum-mechanical (e.g. regular DFT) methods totally unfeasible. Can force-field calculations be used instead? Well, mimicking the interactions and chemical properties without explicit electrons present is a formidable task, especially when the transfer of electrons is closely coupled to the material's functionality, as is the case for redox-active metal oxides. I will discuss some of our efforts in the development of a multiscale modelling approach for surfaces and interfaces of metal oxides (e.g. CeO2, ZnO, MgO) – with and without interacting molecules (e.g. O2 and water).In summary, we combine a range of theoretical methods including DFT [2], tight-binding-DFT [3], and reactive force-field simulations [4] in a consistent multi-scale approach to examine the properties of oxide nanosystems. We generate images and spectra to make direct comparisons with the experimental couterparts (e.g. IRRAS spectra [5] and a new unpublished approach to predict vibrational spectra for OH-covered metal oxides), but we also generate properties that cannot be measured by experiments such as the water dipole moment enhancement on a surface (oftem much larger than in liquid water!). I will also inform about the European Materials Modelling Council (https://emmc.info/), and our efforts to promote the use of materials modelling in industry and the quality of the modelling results; the EMMC is open to everyone interested.References:[1] G. G. Kebede, D. Spångberg, P. D. Mitev, P. Broqvist, K. Hermansson, "Comparing van der Waals DFT methods for water on NaCl(001) and MgO(001), The Journal of Chemical Physics 146, 064703 (2017). [2] M. Hellström, D. Spångberg, K. Hermansson, "Treatment of Delocalized Electron Transfer in Periodic and Embedded Cluster DFT Calculations: The Case of Cu on ZnO (10-10)", Journal of Computational Chemistry 36, 2394 (2015). [3] J. Kullgren, M. J. Wolf, K. Hermansson, Ch. Köhler, B. Aradi,Th. Frauenheim, and P. Broqvist, "Self-Consistent-Charge Density-Functional Tight-Binding (SCC-DFTB) Parameters for Ceria in 0D to 3D". J. Phys. Chem. C 121, 4593−4607 (2017). [4] P. Broqvist, J. Kullgren, M. J. Wolf, A. C. T. van Duin, K. Hermansson, "A ReaxFF force-field for ceria bulk, surfaces and nanoparticles", J. Phys. Chem. C 119, 13598 (2015). [5] S. Hu, Z. Wang, A. Mattsson, L. Österlund, K. Hermansson, "Simulation of IRRAS Spectra for Molecules on Oxide Surfaces: CO on TiO2(110)", J. Phys. Chem. C 119, 5403 (2015).</p
Impact of Users’ Attitudes Toward Anonymous Internet Interventions for Cannabis vs. Alcohol use: A Secondary Analysis of Data From Two Clinical Trials
No full textRomero D, Johansson M,
Hermansson U and Lindner P (2021)
Impact of Users’ Attitudes Toward
Anonymous Internet Interventions for
Cannabis vs. Alcohol Use: A
Secondary Analysis of Data From Two
Clinical Trials.
Front. Psychiatry 12:730153.
doi: 10.3389/fpsyt.2021.73015
Formation of "helical hairpins" during membrane protein integration into the ER membrane: role of the N- and C-terminal flanking regions
No full textThe helical hairpin, two closely spaced transmembrane helices separated by a short turn, is a common structural element in integral membrane proteins. Previous studies on the sequence determinants of helical hairpin formation have focussed on the role of polar and charged residues placed centrally in a long stretch of hydrophobic residues, and have yielded a "propensity scale" for the relative efficiency with which different residues promote the formation of helical hairpins. In this study, we shift our attention to the role of charged residues flanking the hydrophobic stretch. Clusters of charged residues are known to hinder membrane translocation, and thus flanking charged residues may conceivably force a long hydrophobic segment to form a helical hairpin even if there are no or only weakly turn-promoting residues in the hydrophobic stretch. We indeed find that Lys and, more surprisingly, Asp residues strongly affect helical hairpin formation when placed next to a poly-Leu-based transmembrane segment. We also find that a cluster of four consecutive Lys residues can affect the efficiency of helical hairpin formation even when placed approximately 30 residues downstream of the hydrophobic stretch. These observations have interesting implications for the way we picture membrane protein topogenesis within the context of the endoplasmic reticulum (ER) translocon
A turn propensity scale for transmembrane helices.
No full textUsing a model protein with a 40 residue hydrophobic transmembrane segment, we have measured the ability of all the 20 naturally occurring amino acids to form a tight turn when placed in the middle of the hydrophobic segment. Turn propensities in a transmembrane helix are found to be markedly different from those of globular proteins, and in most cases correlate closely with the hydrophobicity of the residue. The turn propensity scale may be used to improve current methods for membrane protein topology prediction
Multiscale modelling of reactive metal oxide interfaces
No full textChemically active metal oxide surfaces and interfaces ‒catalysts, sensors, electrodes‒ play crucial roles in our society and in the development of new technologies. Modelling such complex systems is by no means easy, and the computational scientist needs to make shrewd decisions about both the choice of structural model for the interface and the choice of total-energy method. This presentation concerns static and dynamic condensed-matter chemistry modelling of metal oxide surfaces, interfaces, nanoparticles. I will discuss some of our efforts to develop multiscale modelling protocols for metal oxide surfaces, nanoparticles and interfaces (e.g. CeO2 and ZnO) – with and without interacting molecules. We combine a range of theoretical methods including DFT, tight-binding-DFT, and reactive force-field models. A key question here is whether it is really possible to model redox-active metal oxides without including the electrons? Adequate models for post-processing of simulation data is as important as the data generation itself, since the post-processing links directly to experimental methods for e.g. surface characterization, such as spectra and images. I will also discuss some of our efforts in this field. Chemically active metal oxide surfaces and interfaces ‒catalysts, sensors, electrodes‒ play crucial roles in our society and in the development of new technologies. Modelling such complex systems is by no means easy, and the computational scientist needs to make shrewd decisions about both the choice of structural model for the interface and the choice of total-energy method. . I will discuss some of our efforts to develop multiscale modelling protocols for metal oxide surfaces, nanoparticles and interfaces (e.g. Ceria and ZnO) – with and without interacting molecules. We combine a range of theoretical methods including DFT, tight-binding-DFT, and reactive force-field models. A key question here is: Is it possible to model redox-active metal oxides without including the electrons? Adequate models for post-processing of simulation data is as important as the data generation itself, since the post-processing links directly to experimental methods for, e.g., surface characterization, such as spectra and images. I will also discuss some of our efforts in this field.References: [1] M. Hellström, K. Jorner, M. Bryngelsson, S.E. Huber, J. Kullgren, Th. Frauenheim, P. Broqvist, "An SCC-DFTB Repulsive Potential for Various ZnO Polymorphs and the ZnO-Water System", J. Phys. Chem. C, 2013, 117, 17004.[2] P. Broqvist, J. Kullgren, M. J. Wolf, A. C. T. van Duin, K. Hermansson, "A ReaxFF force-field for ceria bulk, surfaces and nanoparticles", J. Phys. Chem. C, 2015, 119, 13598.[3] M. Hellström, D. Spångberg, K. Hermansson, "Treatment of Delocalized Electron Transfer in Periodic and Embedded Cluster DFT Calculations: The Case of Cu on ZnO (10-10)", Journal of Computational Chemistry, 2015, 36, 2394.[4] S. Hu, Z. Wang, A. Mattsson, L. Österlund, K. Hermansson, "Simulation of IRRAS Spectra for Molecules on Oxide Surfaces: CO on TiO2(110)", J. Phys. Chem. C, 2015, 119, 5403.</p
Cellular immune responses to low density lipoprotein in atherosclerosis
No full textAtherosclerosis is an inflammatory disease of the medium and large sized arterial vessels. Low density lipoprotein (LDL) particles carrying cholesterol are trapped within the arterial intima and elicit both innate as well as adaptive immune responses. T cells are present in the atherosclerotic plaque and cellular immunity plays an important role in lesion development. Mouse models of atherosclerosis are efficient means of unraveling the inflammatory process in the intima. The studies in this thesis have used some of these models to investigate the impact of the adaptive immunity on atherosclerosis and how antigen specific immunity can be explored to create new therapeutic opportunities.Dendritic cells (DC) are potent inducers of T cells. To explore the effect of DC on atherosclerosis, in the context of an atherosclerosis-related antigen, we injected hypercholesterolemic Apoe-/- mice with malondialdehyde (MDA)-LDL pulsed DC. This cell transfer increased local inflammation in the vessel wall and accelerated plaque development. Importantly, the treatment also generated adaptive immune responses specific for components of LDL. This study suggests that DC can be used to influence atherogenic immunity.The use of the hypercholesterolemic huB100tg x Ldlr-/- mouse model permitted us to study human LDL-derived epitopes to dissect the cellular autoimmune response in atherosclerosis. We demonstrated that CD4+ T cells, expressing T cell receptors (TCRs) with the variable beta domain TRBV31, recognize apolipoprotein B100 (ApoB100) of LDL and are needed for the development of advanced atherosclerosis. This illustrates the importance of ApoB100-specific T cell immunity in the atherogenic process.Furthermore, we employed a strategy for immunoprotection of atherosclerosis by nasally administrating an ApoB100-derived peptide fused to the B-subunit of cholera toxin. This treatment targeted the mucosal immunity which led to an induction of antigen-specific regulatory T cells and significantly reduced atherosclerosis in Apoe-/- mice.Finally, to make use of DC as a treatment modality for atherosclerotic disease, we injected huB100tg x Ldlr-/- mice with DC that had been made tolerogenic by treatment with IL-10 and ApoB100. This led to a very significant reduction of atherosclerotic lesions in the aorta with decreased CD4+ T cell infiltrates and dampened systemic inflammation. The tolerogenic DC therapy diminished the autoreactive T cell response to ApoB100, showing the relevance of antigen-specific immunity in atherosclerosis and treatments thereof. In conclusion, we have studied the adaptive immunity to ApoB100 of LDL in mouse models. This has led to the identification of novel therapeutic targets for cardiovascular disease. We found that pro-atherosclerotic T cells can recognize ApoB100 and that DC can present epitopes of LDL and activate pro-inflammatory T cells. When manipulating DC to induce T cell tolerance to ApoB100, immunoprotection is established with reduced atherosclerosis as a consequence. Finally, by using derivatives of ApoB100 for mucosal vaccination we could also target atherosclerosis development.List of scientific papersI. Hjerpe C, Johansson D, Hermansson A, Hansson GK, Zhou X (2010). "Dendritic cells pulsed with malondialdehyde modified low density lipoprotein aggravate atherosclerosis in Apoe(-/-) mice." Atherosclerosis 209(2): 436-41. Epub 2009 Nov 7 https://pubmed.ncbi.nlm.nih.gov/19897195II. Hermansson A, Ketelhuth DF, Strodthoff D, Wurm M, Hansson EM, Nicoletti A, Paulsson-Berne G, Hansson GK (2010). "Inhibition of T cell response to native low-density lipoprotein reduces atherosclerosis." J Exp Med 207(5): 1081-93. Epub 2010 May 3 https://pubmed.ncbi.nlm.nih.gov/20439543III. Klingenberg R, Lebens M, Hermansson A, Fredrikson GN, Strodthoff D, Rudling M, Ketelhuth DF, Gerdes N, Holmgren J, Nilsson J, Hansson GK (2010). "Intranasal immunization with an apolipoprotein B-100 fusion protein induces antigen-specific regulatory T cells and reduces atherosclerosis." Arterioscler Thromb Vasc Biol 30(5): 946-52. Epub 2010 Feb 18 https://pubmed.ncbi.nlm.nih.gov/20167655IV. Hermansson A, Johansson D, Ketelhuth DFJ, Andersson J, Zhou X, Hansson GK (2010). "Immunotherapy with tolerogenic apolipoprotein B-100 loaded dendritic cells attenuates atherosclerosis in hypercholesterolemic mice." (Submitted)</p
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
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