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Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Thermodiffusion of aqueous salt solutions: Hofmeister Series and overlapping hydration shells
No full textMotivationOur study of ionic solutes is motivated by the most important practical application of thermodiffusion, where it is used to monitor protein-ligand reactions. Proteins are complex molecules that contain ionic as well as non-ionic groups. While non-ionic solutes in water have been extensively studied recently (Niether and Wiegand, 2019), ionic solutes' concentration and temperature dependence have not been investigated systematically. For non-ionic compounds, a strong correlation between thermodiffusion and hydration was found (Niether and Wiegand, 2019). Figure 1: Schematic comparison of the temperature dependence of ST for non-ionic and ionic solutes at different concentrations: low (dotted line), intermediate (dashed line), and high (solid line).Comparison of non-ionic and ionic solutesWe found one striking difference between non-ionic and ionic solutes looking at the effect of concentration on the temperature dependence of the Soret coefficient S_T, as illustrated in Fig. 1 (Mohanakumar et al. 2021). For a typical non-ionic solute in water, the behavior of ST changes from increasing with temperature to decreasing with temperature as the concentration increases. This is correlated with the hydration of the solutes which decreases as the concentration increases. Only very hydrophilic non-ionic solutes have ST values that increase with temperature for all concentrations. In contrast, the Soret coefficients of ionic solutes show the typical temperature dependence of very hydrophilic solutes over the entire concentration range. For salts with a high degree of dissociation we might have a tightly bound first hydration layer, which leads to a highly hydrophilic entity. For less dissociated salts it might be explained by cluster formation of the salts with increasing concentrations. Even at high salt concentrations the clusters as a whole are hydrated at their surfaces by water, but the total exposure to water is less as the surface decreases when more ions are part of larger clusters. Figure 2: (a) SiT values of all studied systems plotted as functionof log P. Note, that log P is the sum of an ionic and non-ionic contribution. First order polynomials of concentration and temperature have been used to fit the data using Eq.1. (b) Sequence of the anions based on SiT for the two investigated cations in comparison with the Hofmeister series.Anion and Cation influence on ST We investigated systematically the concentration and temperature dependence of the thermodiffusion of aqueous solutions of various potassium and sodium salts (Mohanakumar et al. 2021, Mohanakumar et al. 2022a). To describe the temperature and concentration dependence we used an empirical Ansatz suggested by Wittko and Köhler (Wittko and Köhler, 2007)S_T\left(m,T\right)=\alpha\left(m\right)\beta\left(T\right)+S_T^i (1)With polynomial serial expansions for \alpha\left(m\right) and \beta\left(T\right)\alpha\left(m\right)=\alpha_1m+\alpha_2m^2+\alpha_3m^3+\cdots\bigm\beta\left(m\right)=1+b_1\left(T-T_0\right)+b_2\left(T-T_0\right)^2+\cdots (2) m is the molality, T_0 is an arbitrary reference temperature, set to T_0=25°C and S_T^i is a temperature and concentration independent constant. Note, that we set a_0=0 as it is strongly coupled to S_T^i. We could describe the temperature and concentration dependence of S_T of various potassium and sodium salts in water using Eq.(1). In Figure 2(a) we display the adjustable parameter S_T^i as function of\ \log{P}, with P being the ratio of the equilibrium concentration of the solute (salt) in octanol and in water. So, a negative \log{P} signifies stronger hydrophilicity. We find for all investigated salts a linear correlation between S_T^i and\log{P}. This implies that also, for ionic solutes, hydrophilicity plays an important role. If we compare with the hydrophilicity scale of the Hofmeister series, we find a good agreement except for the thiocyanate anion, which should be, according to Hofmeister, the most hydrophobic anion. In brief, we can state that the hydration of the ions plays a significant role.Overlapping hydration shellsVarious salts in water exhibit non-monotonic variations of the Soret coefficient S_T with concentration, which is not understood on a microscopic level. We investigated the thermodiffusive properties of aqueous solutions of sodium iodide, potassium iodide and lithium iodide, using thermal diffusion forced Rayleigh scattering in a concentration range of 0.5 – 4 mole per kg of solvent and a temperature range of 15 to 45°C (Mohanakumar et al. 2022b). In all three cases S_T has a minimum at m_{min}=1 mole per kg of solvent. We develop an intuitive picture in which the relevant objects are the fully hydrated salt molecules (FHP), including all water molecules that behave differently from bulk water. Our hypothesis is that these FHPs form a random close packing at m_{min}, which implies that the outer hydration shell start to touch as indicated in Figure 3. Preliminary, somewhat sketchy calculations indicate that indeed Soret coefficients begin to rise beyond m_{min}. Indications are given as to why the model will fail at large concentrations. Figure 3: Hydrated salt molecules overlapping with increasing concentration. The green–red sphere represents the bare salt molecule, after adding the blue shell of strongly attached water molecules we get the salt particle (HSP), while after adding next the outer light blue shell of perturbed water we arrive at the hydrated salt molecule, called FHP. At concentrations above mmin the outer shells overlap as shown on the right side.ConclusionsWe have studied the thermophoretic properties of various salts in water over a range of temperatures and concentrations. Although the temperature dependence of the Soret coefficient of the ionic compounds does not change in the same pronounced way as function of their hydrophilicity observed for non-ionic solutes, we find a linear correlation between S_T^i and \log{P}. Most likely, the hydration shell of ionic solutes is more tightly bound to the ions than in the case of non-ionic solutes, so we find a similar temperature dependence of the Soret coefficient for all concentrations. Additionally, overlapping of the hydration shells might also be responsible for the occurrence of a minimum of S_T with concentration. However, this hypothesis needs to be quantified by computer simulations. AcknowledgementsWe thank Fernando Bresme, Jan Dhont and Jutta Luettmer-Strathmann for fruitful and helpful discussions. ReferencesD. Niether, S. Wiegand, Thermophoresis of biological and biocompatible compounds in aqueous solution, J. Phys. Condens. Matter, 31, 503003 (2019).S. Mohanakumar, J. Luettmer-Strathmann, S. Wiegand, Thermodiffusion of aqueous solutions of various potassium salts, J. Chem. Phys., 154, 84506 (2021).S. Mohanakumar, S. Wiegand: Towards understanding specific ion effects in aqueous media using thermodiffusion The Eur. Phys. J. E 45(2), 10 (2022a).G. Wittko, W. Köhler, On the temperature dependence of thermal diffusion of liquid mixtures, Europhys. Lett. 78, 46007 (2007).S. Mohanakumar, H. Kriegs, W. J. Briels, S. Wiegand, Overlapping hydration shells in salt solutions causing non-monotonic Soret coefficients with varying concentration PCCP 24, 27380 (2022b)
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
Get PDFIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
Cutting Edge: Pseudomonas aeruginosa Abolishes Established Lung Transplant Tolerance by Stimulating B7 Expression on Neutrophils
No full textThe mechanisms that link bacterial infection to solid organ rejection remain unclear. In this study, we show that following the establishment of lung allograft acceptance in mice, Pseudomonas aeruginosa airway infection induces a G-CSF-dependent neutrophilia that stimulates acute rejection. Graft-infiltrating neutrophils sharply upregulate the B7 molecules CD80 and CD86, but they do not express CD40 or MHC class II in response to P. aeruginosa infection. Neutrophil B7 promotes naive CD4(+) T cell activation and intragraft IL-2(+), IFN-gamma(+), and IL-17(+) T lymphocyte accumulation. Intravital two-photon microscopy reveals direct interactions between neutrophils and CD4(+) T cells within pulmonary allografts. Importantly, lung rejection in P. aeruginosa-infected recipients is triggered by CD80/86 on neutrophils and can be prevented by B7 blockade without affecting clearance of this pathogen. These data show that neutrophils enhance T cell activation through B7 trans-costimulation and suggest that inhibiting neutrophil-mediated alloimmunity can be accomplished without compromising bacterial immune surveillance. The Journal of Immunology, 2012, 189: 4221-4225
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Pelevin’s Trinity in the novel “t”: author – protagonist – reader
No full textThe article attempts to interpret Pelevin's artistic strategy in the novel "T" by exploring its subject organization and addressing the key problems of the author, the protagonist, and the reader as they are seen by the researcher. The article analyzes the peculiarities of constructing the narrative reality in the novel "T", and goes on to discuss Pelevin's philosophic models of the development of the humankind, and the emergence of his new anthropology
Measuring industry-science links through inventor-author relations: A profiling method
Get PDFIn this pilot study we examine the performance of text-based profiling in recovering a set of validated inventor-author links. In a first step we match patents and publications solely based on their similarity in content. Next, we compare inventor and author names on the highest ranked matches for the occurrence of name matches. Finally, we compare these candidate matches with the names listed in a validated set of inventor-author names. Our text-based profile methodology performs significantly better than a random matching of patents and publications, suggesting that text-based profiling is a valuable complementary tool to the name searches used in previous studies.innovation; industry-science links; text-based profiling;
Wave turbulence of a rotating array of quantized vortices in the T → 0 temperature limit
No full textThe dynamics of quantized vortices in the zero temperature limit is currently of great interest, particularly in the case of the Fermi superfluid He-B. Here we study wave turbulence, generated by the librating motion of a rotating cylindrical container filled with He-B, in the limit of vanishing viscous forces at temperatures . The polarization of the quantized vortices with respect to the axis of rotation is measured using non-invasive NMR techniques. We observe a decrease of the polarization when the librating motion is started, and a two-stage relaxation process when the modulation of the rotation velocity is stopped. The first relaxation process is associated with the dissipation of large-scale flow stored in inertial waves and the solid body rotation of the vortex array. From the decay of these energy reservoirs we determine the rate of energy dissipation of large-scale flow. The later second process is related to the relaxation of Kelvin waves on individual vortices. This process is monitored by the recovery of the polarization. The existence of a Kelvin wave cascade at the lowest temperatures is currently a central open question. We supply some evidence for the cascade
DNA fusion gene vaccination mobilizes effective anti-leukemic cytotoxic T lymphocytes from a tolerized repertoire
No full textThe majority of known human tumor-associated antigens derive from non-mutated self proteins. T cell tolerance, essential to prevent autoimmunity, must therefore be cautiously circumvented to generate cytotoxic T cell responses against these targets. Our strategy uses DNA fusion vaccines to activate high levels of peptide-specific CTL. Key foreign sequences from tetanus toxin activate tolerance-breaking CD4+ T cell help. Candidate MHC class Ibinding tumor peptide sequences are fused to the C terminus for optimal processing and presentation. To model performance against a leukemia-associated antigen in a tolerized setting, we constructed a fusion vaccine encoding an immunodominant CTL epitopederived from Friend murine leukemia virus gag protein (FMuLVgag) and vaccinated tolerant FMuLVgag-transgenic (gag-Tg) mice. Vaccination with the construct induced epitopespecificIFN-c-producing CD8+ T cells in normal and gag-Tg mice. The frequency and avidity of activated cells were reduced in gag-Tg mice, and no autoimmune injury resulted. However, these CD8+ T cells did exhibit gag-specific cytotoxicity in vitro and in vivo. Also, epitope-specific CTL killed FBL-3 leukemia cells expressing endogenous FMuLVgag antigen and protected against leukemia challenge in vivo. These results demonstrate a simple strategy to engage anti-microbial T cell help to activate epitope-specific polyclonal CD8+ T cell responses from a residual tolerized repertoire
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