5 results on '"Malin Wohlert"'
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2. Cellulose and the role of hydrogen bonds : not in charge of everything
- Author
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Tobias Benselfelt, Lars Wågberg, Jakob Wohlert, Malin Wohlert, István Furó, and Lars Berglund
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Hydrogen bonding ,Molecular interactions ,Materials science ,Polymers and Plastics ,Polymer science ,Hydrogen bond ,Computer modeling ,Pappers-, massa- och fiberteknik ,Molecular simulation ,Charge (physics) ,Paper, Pulp and Fiber Technology ,chemistry.chemical_compound ,chemistry ,Cellulose ,Nanomaterials - Abstract
In the cellulose scientific community, hydrogen bonding is often used as the explanation for a large variety of phenomena and properties related to cellulose and cellulose based materials. Yet, hydrogen bonding is just one of several molecular interactions and furthermore is both relatively weak and sensitive to the environment. In this review we present a comprehensive examination of the scientific literature in the area, with focus on theory and molecular simulation, and conclude that the relative importance of hydrogen bonding has been, and still is, frequently exaggerated.
- Published
- 2022
3. Propensity, free energy contributions and conformation of primary n -alcohols at a water surface
- Author
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Jochen S. Hub, Carl Caleman, Victor Ekholm, and Malin Wohlert
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Quantitative Biology::Biomolecules ,Chemistry ,Enthalpy ,Condensation ,Nucleation ,General Physics and Astronomy ,Small molecule ,Hydrophobic effect ,Molecular dynamics ,Adsorption ,Chemical physics ,ddc:540 ,Polar ,Physics::Chemical Physics ,Physical and Theoretical Chemistry - Abstract
Physical chemistry, chemical physics 23(34), 18823 - 18829 (2021). doi:10.1039/D1CP02818A, Atmospheric aerosols contain organic molecules that serve as cloud condensation nucleation sites and affect the climate. Several experimental and simulation studies have been dedicated to investigate their surface propensity, but the mechanisms that drive them to the water surface are still not fully understood. In this molecular dynamics (MD) simulation study, primary alcohols are considered as a model system representing polar organic molecules. We find that the surface affinity of n-alcohols increases linearly with the length of the hydrophobic tail. By decomposing the adsorption free energy into enthalpy and entropy contributions, we find that the transition from bulk to surface is entropically driven, compatible with the fact that the hydrophobic effect of small solutes is of entropic origin. The enthalpy of surface adsorption is nearly invariant among different n-alcohols because the loss of solvent���alcohol interactions is balanced by a gain in solvent���solvent interactions. Structural analysis shows that, at the surface, the linear alcohols prefer an orientation with the hydrophobic tail pointing out from the surface, whereas the hydroxyl group remains buried in the water. This general behaviour is likely transferable to other small molecules with similar structures but other functional groups that are present in the atmosphere. Therefore, the present study is a step forward toward a general description of organic molecules in aerosols., Published by RSC Publ., Cambridge
- Published
- 2021
- Full Text
- View/download PDF
4. Charge State Dependence of Amino Acid Propensity at Water Surface: Mechanisms Elucidated by Molecular Dynamics Simulations
- Author
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Carl Caleman, Malin Wohlert, Geethanjali Gopakumar, and Radost Herboth
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chemistry.chemical_classification ,Fysikalisk kemi ,010304 chemical physics ,Hydrogen bond ,Phenylalanine ,010402 general chemistry ,01 natural sciences ,Physical Chemistry ,Article ,0104 chemical sciences ,Amino acid ,Molecular dynamics ,chemistry ,Computational chemistry ,Valine ,0103 physical sciences ,Glycine ,Teoretisk kemi ,Side chain ,ddc:530 ,Physical and Theoretical Chemistry ,Umbrella sampling ,Theoretical Chemistry - Abstract
The journal of physical chemistry / A 125(22), 4705 - 4714 (2021). doi:10.1021/acs.jpca.0c10963, Atmospheric aerosols contain a variety of compounds, among them free amino acids and salt ions. The pH of the aerosol droplets depends on their origin and environment. Consequently, compounds like free amino acids found in the droplets will be at different charge states, since these states to a great extent depend on the surrounding pH condition. In droplets of marine origin, amino acids are believed to drive salt ions to the water surface and a pH-dependent amino acid surface propensity will, therefore, indirectly affect many processes in atmospheric chemistry and physics such as for instance cloud condensation. To understand the surface propensity of glycine, valine, and phenylalanine at acidic, neutral, and basic pH, we used molecular dynamics (MD) simulations to investigate them at three different charge states in water. Their respective surface propensities were obtained by the means of a potential of mean force (PMF) in an umbrella sampling approach. Glycine was found to have no preference for the surface, while both valine and phenylalanine showed high propensities. Among the charge states of the surface-enriched ones, the cation, representing the amino acids at low pH, was found to have the highest affinity. Free energy decomposition revealed that the driving forces depend strongly on the nature of the amino acid and its charge state. In phenylalanine, the main factor was found to be a substantial entropy gain, likely related to the side chain, whereas in valine, hydrogen bonding to the functional groups leads to favorable energies and, in turn, affects the surface propensity. A significant gain in water���water enthalpy was seen for both valine and phenylalanine., Published by Soc., Washington, DC
- Published
- 2021
- Full Text
- View/download PDF
5. Functionalization and patterning of nanocellulose films by surface-bound nanoparticles of hydrolyzable tannins and multivalent metal ions
- Author
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Malin Wohlert, Mama Pléa, Jakob Wohlert, Christina Schütz, Zoltán Bacsik, Wei Xia, Mukta V. Limaye, Konstantin Kriechbaum, Lennart Bergström, German Salazar-Alvarez, and Cheick Dembele
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Solid-state chemistry ,Metal ions in aqueous solution ,Hydrolyzable Tannin ,Nanoparticle ,Materialkemi ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Nanocellulose ,Metal ,Adsorption ,Chemical engineering ,visual_art ,visual_art.visual_art_medium ,Materials Chemistry ,Surface modification ,General Materials Science ,0210 nano-technology - Abstract
Inspired by the Bogolanfini dyeing technique, we report how flexible nanofibrillated cellulose (CNF) films can be functionalized and patterned by surface-bound nanoparticles of hydrolyzable tannins and multivalent metal ions with tunable colors. Molecular dynamics simulations show that gallic acid (GA) and ellagic acid (EA) rapidly adsorb and assemble on the CNF surface, and atomic force microscopy confirms that nanosized GA assemblies cover the surface of the CNF. CNF films were patterned with tannin-metal ion nanoparticles by an in-fibre reaction between the pre-impregnated tannin and the metal ions in the printing ink. Spectroscopic studies show that the Fe-III/II ions interact with GA and form surface-bound, stable GA-Fe-III/II nanoparticles. The functionalization and patterning of CNF films with metal ion-hydrolyzable tannin nanoparticles is a versatile route to functionalize films based on renewable materials and of interest for biomedical and environmental applications.
- Published
- 2019
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