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Item Open Access Adsorption of heavy metals from low concentration solutions onto dried Chlamydomonas reinhardtii(2024) Genduso, Maria Giuseppina; Guagliano, Marianna; Finocchio, Elisabetta; Cristiani, Cinzia; Dotelli, Giovanni; Santomauro, GiuliaHeavy metals, such as Pb(II), Cr(III), and Cd(II), are frequently discharged into the environment, resulting in a threat for the health of living organisms. Microalgae represent an ecological method for the removal of these pollutants. The capture capability of active and dried Chlamydomonas reinhardtii towards both mono-ionic and multi-ionic solutions is evaluated to study the bioremediation in low-polluted wastewaters. Several characterization techniques have been performed to study morphology, composition, and the interaction between the metals and the microalgal functional groups of the wall. The effect of the operating conditions, such as contact time and pH, is assessed; an increased contact time of 4 days did not influence the adsorption yields of Pb and Cr, but it had a negative effect on Cd adsorption, while the impact of pH was mainly affecting the chemical speciation, rather than the adsorption capability. The microalga showed a larger affinity for Pb and Cd, respectively, 80 and 76% ( w / w ) of adsorption, while only the 65% ( w / w ) of the total Cr was adsorbed, suggesting a preferential biosorption.Item Open Access Polycondensation‐derived high‐molecular weight lignin as nonblended precursor for carbon fibers(2024) Clauss, Manuel M.; Frank, Erik; Bauch, Volker; Kuske, Lisa; Buchmeiser, Michael R.A new concept for the controlled chain‐extension of lignin has been developed. A mixture of trioxane as formaldehyde source, resorcinol as chain extender, and lignin allows to prepare high molecular weight precursor fibers by melt‐spinning, which can be spun on a semitechnical scale. Chain extension with resorcinol bridged by methylene groups is achieved during the stabilization process of the precursor fiber. After carbonization, carbon fibers (CFs) with an average diameter of 18 µm show an average tensile strength of 0.78 GPa and a Young's modulus of 106 GPa. A maximum tensile strength of 2.44 GPa and a Young's modulus of 294 GPa are reached with fibers 9.7 µm in diameter.Item Open Access Counterion effects on the mesomorphic and electrochemical properties of guanidinium salts(2024) Ebert, Max; Lange, Alyna; Müller, Michael; Wuckert, Eugen; Gießelmann, Frank; Klamroth, Tillmann; Zens, Anna; Taubert, Andreas; Laschat, SabineIonic liquid crystals (ILCs) combine the ion mobility of ionic liquids with the order and self-assembly of thermotropic mesophases. To understand the role of the anion in ILCs, wedge-shaped arylguanidinium salts with tetradecyloxy side chains were chosen as benchmark systems and their liquid crystalline self-assembly in the bulk phase as well as their electrochemical behavior in solution were studied depending on the anion. Differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (WAXS, SAXS) experiments revealed that for spherical anions, the phase width of the hexagonal columnar mesophase increased with the anion size, while for non-spherical anions, the trends were less clear cut. Depending on the anion, the ILCs showed different stability towards electrochemical oxidation and reduction with the most stable being the PF6 based compound. Cyclic voltammetry (CV) and density functional theory (DFT) calculations suggest a possible contribution of the guanidinium cation to the oxidation processes.Item Open Access Flux calculation for primary metabolism reveals changes in allocation of nitrogen to different amino acid families when photorespiratory activity changes(2024) Friedrichs, Nils; Shokouhi, Danial; Heyer, Arnd G.Photorespiration, caused by oxygenation of the enzyme Rubisco, is considered a wasteful process, because it reduces photosynthetic carbon gain, but it also supplies amino acids and is involved in amelioration of stress. Here, we show that a sudden increase in photorespiratory activity not only reduced carbon acquisition and production of sugars and starch, but also affected diurnal dynamics of amino acids not obviously involved in the process. Flux calculations based on diurnal metabolite profiles suggest that export of proline from leaves increases, while aspartate family members accumulate. An immense increase is observed for turnover in the cyclic reaction of glutamine synthetase/glutamine-oxoglutarate aminotransferase (GS/GOGAT), probably because of increased production of ammonium in photorespiration. The hpr1-1 mutant, defective in peroxisomal hydroxypyruvate reductase, shows substantial alterations in flux, leading to a shift from the oxoglutarate to the aspartate family of amino acids. This is coupled to a massive export of asparagine, which may serve in exchange for serine between shoot and root.Item Open Access Monazite beats zircon regarding dating of young metamorphic events : an example from polycyclic granitic gneiss of the Pohorje Mountains, Slovenia(2024) Li, Botao; Massonne, Hans‐Joachim; Zhang, Junfeng; Yuan, Xiaoping; Luo, TaoThe result of dating U-(Th)-Pb bearing minerals in metamorphic rocks frequently suffers from the interpretative relation of their growth to a specific metamorphic event. This problem occurs in the southern Pohorje Mountains. Therefore, granitic gneiss from this area was studied. Rims of zircon in these rocks gave U-Pb ages around 90 Ma interpreted as an indicator of Late Cretaceous metamorphism. However, in situ dating of monazite with LA-ICP-MS yielded Early Miocene U-Th-Pb ages consistent with contact metamorphism by magmas forming the Pohorje pluton. This is supported by geothermobarometry using compositions of garnet and muscovite in granitic gneiss. This method led to pressure–temperature conditions of 6.5 kbar and 625°C, in line with intrusion depths estimated for the southeastern part of the Pohorje pluton. Consequently, zircon was not suitable for dating the latest metamorphic event but monazite was. Furthermore, monazite dating suggests two main intrusion pulses of magmas differing by 2-3 Ma.Item Open Access Computational investigation of catalytic reaction mechanisms(2024) Heitkämper, Juliane; Kästner, Johannes (Prof. Dr.)Item Open Access Prolinyl phosphoramidates of nucleotides with increased reactivity(2024) Humboldt, Adrian; Rami, Fabian; Topp, Franka M.; Arnold, Dejana; Göhringer, Daniela; Pallan, Pradeep S.; Egli, Martin; Richert, ClemensNucleoside monophosphates (NMPs) are the subunits of RNA. They are incorporated into growing complementary strands when sequences are copied in enzyme‐free reactions using organic leaving groups at the phosphates. Amino acids are rarely considered as leaving groups, but proline can act as a leaving group when N‐linked to NMPs, so that prolinyl NMPs hydrolyze in aqueous buffer at 37 °C, with half‐life times as short as 2.4 h, and they act as monomers in enzyme‐free primer extension. Still, their level of reactivity is insufficient for practical purposes, requiring months for some extensions. Herein we report the synthesis of eight substituted prolinyl AMPs together with seven related compounds and the results of a study of their reactivity. A δ‐carboxy prolinyl NMP was found to be converted with a half‐life time of just 11 min in magnesium‐free buffer, and a δ‐isopropyl prolinyl NMP was shown to react sevenfold faster than its prolinyl counterpart in enzyme‐free genetic copying of RNA. Our results indicate that both anchimeric and steric effects can be employed to increase the reactivity of aminoacidyl nucleotides, i.e. compounds that combine two fundamental classes of biomolecules in one functional entity.Item Open Access Influence of the counterion on the structure and stability of the smectic C phase in ionic liquid crystals(2024) Kapernaum, Nadia; Opri, Klaudia; Wuckert, Eugen; Marino, Sebastian; Scheuring, Nikolai; Laschat, Sabine; Gießelmann, FrankItem Open Access Total synthesis of tosyl‐samroiyotmycin A and its biological profiling(2024) Kolb, Benedikt; Schmid, Fabian; Weng, Jessica; Altevogt, Luca; Pereira Rebelo, Ruben; Wank, Bianca; Baro, Angelika; Zens, Anna; Shekhar, Aditya; Bilitewski, Ursula; Sax, Sibylle; Wittlin, Sergio; Taylor, Dale; Müller, Rudolf; Laschat, SabineAbstractA total synthesis of the enantiopure syn,syn‐tosyl‐samroiyotmycin A, a C2‐symmetric 20‐membered antimalarial macrodiolide with syn,syn‐configuration of the 8,24‐dihydroxy‐9,25‐dimethyl units and it's enantiopure anti,anti‐derivative is described. The synthesis was accomplished utilizing a linear approach in 7 steps and 3 % overall yield via a sequence of diastereoselective methylation of SuperQuat oxazolidinone auxiliary, cross metathesis and Yamaguchi macrolactonization of fully functionalized seco‐acids. By a similar approach we gained access to several samroiyotmycin analogues and precursors. Antimalarial activity was tested on multi‐resistant (K1) and sensitive (Nf54) P. falciparum strains providing insight into structure activity relationships. Both tosyl‐oxazol unit as well as the syn‐configuration of the two contiguous stereogenic centers turned out to be beneficial for antiplasmodial activity. For instance, syn,syn‐tosyl‐samroiyotmycin A showed 3.4 times higher activities than the “tosyl‐free” natural product.Item Open Access Revealing the antipolar order in the antiferroelectric SmZA phase by means of circular alignment(2024) Nacke, Pierre; Tuffin, Rachel; Klasen-Memmer, Melanie; Rudquist, Per; Giesselmann, FrankMany ferroelectric nematic liquid crystals, like one of the archetype materials, DIO, do not have a direct paraelectric N to ferroelectric NF phase transition, but exhibit yet another phase between N and NF. This phase has recently been proposed to be antiferroelectric, with a layered structure of alternating polarization normal to the average director and is sometimes referred to as Smectic ZA (SmZA). We have examined the SmZA phase in circularly rubbed (CR) cells, known to discriminate between the polar NF and the non-polar N phase from the configuration of disclination lines formed. We find that the ground state of SmZA has the same disclination configuration as the non-polar N phase, demonstrating that the SmZA phase is also non-polar, i.e., it has no net ferroelectric polarization. At the same time, the SmZA texture generally has a grainy appearance, which we suggest is partly a result of the frustration related to layered order combined with the imposed twist in CR cells. We discuss possible orientations of the smectic layers, depending on the alignment conditions. While a horizontal SmZA layer structure is always compatible with surface-induced twist, a vertical layer structure would tend to break up in a twisted bookshelf structure to match non-parallel alignment directions at the two surfaces.