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Data: Towards understanding specific ion effects in aqueous media using thermodiffusion
No full text<p>Data, which are presented in the following publication: Mohanakumar, Shilpa; Wiegand, Simone (2022): Towards understanding specific ion effects in aqueous media using thermodiffusion. In: The Eur. Phys. J. E 45 (2), S. 10. DOI: 10.1140/epje/s10189-022-00164-8.</p>
Data: Thermodiffusion of aqueous solutions of various potassium salts
No full text<p>Data, which are presented in the following publication: Mohanakumar, Shilpa; Luettmer-Strathmann, Jutta; Wiegand, Simone (2021): Thermodiffusion of aqueous solutions of various potassium salts. In: J Chem Phys 154 (8), S. 84506. DOI: 10.1063/5.0038039.</p>
Thermophoresis of electrolyte solutions and protein-ligand systems
Get PDFThermophoresis or thermodiffusion is the mass transport driven by a temperature gradient.
This thesis focuses on the thermophoretic motion of ionic compounds in a biological context
and is motivated by a practical application, in which thermodiffusion is used to monitor
protein-ligand reactions. Proteins are complex molecules containing non-ionic and ionic
groups. While recent studies of non-ionic compounds found a strong correlation between
thermodiffusion and hydration, it is unclear how this correlation changes when molecules
are charged. To separate ionic from non-ionic contributions, it is reasonable to look first
into the thermophoretic motion of simple salts without large organic side groups and to
study in the next step complex protein-ligand systems, which typically contain hydrophobic
and hydrophilic groups. The systematic studies of aqueous solutions of simple salts should
reveal differences between ionic and non-ionic systems and should give further information
about ion and ion specific effects. Due to the high complexity of protein-ligand systems,
complementary methods should be used to gain a better understanding of the interactions
between different components that are present in the system. This will help to understand
how the thermophoretic behavior of the free protein differs from that of the protein-ligand
complex formed.
Study of the thermophoretic behavior of ionic systems indicates that several correlations,
which were found for aqueous solutions of non-ionic solutes are no longer valid for ionic
solutes. For non-ionic solutes hydrogen bonds primarily influence the thermophoretic behavior.
In case of ionic solutes, although both electrostatic interactions and hydrogen bonds
are present, it is found that thermophoretic behavior is influenced by electrostatic interactions.
Focusing on the specific ion effects for ionic systems in the context of the Hofmeister
series, a change of the anion is found to influence the thermophoretic behavior more than
a change of the cation. Further, a correlation between thermophoretic behavior and hydrophilicity
of the ionic solutes is found, which underlines the sensitivity of thermodiffusion
to changes in hydration. Based on this sensitivity, a preliminary model is developed for describing
the non-monotonous variation of Soret coefficient ST with concentration for aqueous
solutions of alkali iodide salts. To study the thermodiffusion of binding reactions, we also
use complementary methods such as Isothermal Titration Calorimetry (ITC) and a thermophoretic
microfluidic cell. As systems, we have chosen EDTA-CaCl2 and protein-ligand
systems (binding of Bovine Carbonic Anhydrase I (BCA I) with two aryl sulfonamide ligands). To gain deeper insight into the complex formation reactions thermophoretic data
(non-equilibrium process) are compared with thermodynamic data (equilibrium process) to
establish a mathematical relation between ST and Gibb’s free energy ΔG. For EDTA-CaCl2
and protein-ligand systems, the derived relation holds valid, which enables calculation of ΔG
at a particular temperature from ST
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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