Tamás Horváth

This study investigates how phospholipid headgroups influence passive membrane penetration and structural impact of four nitrogen-, sulfur-, and oxygen-containing heterocycles (NSO-HETs)—N-methyl-2-pyrrolidone (PIR), 1,4-dioxane (DIOX), oxane (OXA), and phenol (PHE). Using all-atom molecular dynamics simulations combined with Accelerated Weight Histogram free energy calculations, the passive transport of NSO-HETs across DPPC, DPPE, DPPA, and DPPG bilayers was characterized. DPPG showed the highest membrane affinity, increasing permeability (logP_memb/bulk) by 27–64% compared to DPPE, associated with the lowest permeability and tightest lipid packing. Free energy barriers are also decreased in DPPG relative to DPPE; PIR’s central barrier dropped from 19.2 kJ/mol (DPPE) to 16.6 kJ/mol (DPPG), while DIOX’s barrier decreased from 7.2 to 5.2 kJ/mol. OXA exhibited the lowest central barriers (1.2–2.2 kJ/mol) and uniquely accumulated at higher concentrations in the bilayer center than in bulk water, with free energy ranging from −3.4 to −5.9 kJ/mol. PHE and OXA caused significant bilayer thinning (up to 11%) and reduced lipid tail order, especially in DPPE and DPPA. Concentration effects were most pronounced in DPPE, where high solute loading disrupted lipid order and altered free energy profiles. These results highlight the crucial role of headgroup identity in modulating NSO-HET membrane permeability and structural changes.

Nuclear incidents release hazardous ⁹⁰Sr, posing risks to health. Seeking chelating agents capable of removing ⁹⁰Sr is critical for nuclear safety and development. In our work, the main goal was to develop a substantial yet straightforward method to support the design of viable, in vivo stable chelating agents for radiostrontium. To investigate, we implemented the highly accurate density functional theory (DFT)-based r²SCAN-3c composite method and isothermal titration calorimetry (ITC). Our methods were validated through the characterization of calcium (Ca²⁺) and strontium (Sr²⁺) chelation by ethylenediaminetetraacetic acid (EDTA). The chosen DFT model was able to approximate the literature value (ΔΔG _DFT of 15.4 kJ/mol for the ion exchange reaction from Ca-EDTA to Sr-EDTA, compared to the literature value of 11.0 kJ/mol), while the thermodynamic parameters obtained from the ITC study of calcium EDTA chelation were almost identical to those found in the literature. With the validated methods, strontium chelation by (7,16-bis-malonate)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-bis-malonic acid (Decorporol) was first synthesized and then examined. Our DFT calculations revealed that the exchange reaction from Ca²⁺ to Sr²⁺ with Decorporol has an exergonic (-14.1 kJ/mol) Gibbs free energy profile, which is also approved by the experimental Gibbs free energy change of -34.5 ± 1.1 kJ/mol obtained from the ITC measurements. Measurements at elevated temperatures and physiological conditions did not impact chelation significantly; therefore, in vivo application of the chelating agent is feasible.

A sudden increase in polyurethane (PU) production necessitates viable recycling methods for the waste generated. PU is one of the most important plastic materials with a wide range of applications; however, the stability of the urethane linkage is a major issue in chemical recycling. In this work, termination reactions of a model urethane molecule, namely methyl N-phenyl carbamate (MPCate), are investigated using G3MP2B3 composite quantum chemical method. Our main goal was to gain insights into the energetic profile of urethane bond termination and find an applicable chemical recycling method. Hydrogenation, hydrolysis, methanolysis, peroxidation, glycolysis, ammonolysis, reduction with methylamine and termination by dimethyl phosphite were explored in both gas and condensed phases. Out of these chemicals, degradation by H₂, H₂O₂ and CH₃NH₂ revealed promising results with lower activation barriers and exergonic pathways, especially in water solvation. Implementing these effective PU recycling methods can also have significant economic benefits since the obtained products from the reactions are industrially relevant substances. For example, aniline and dimethyl carbonate could be reusable in polymer technologies serving as potential methods for circular economy. As further potential transformations, several ionizations of MPCate were also examined including electron capture and detachment, protonation/deprotonation and reaction with OH⁻. Alkaline digestion against the model urethane MPCate was found to be promising due to the relatively low activation energy. In an ideal case, the transformation of the urethane bond could be an enzymatic process; therefore, potential enzymes, such as lipoxygenase, were also considered for the catalysis of peroxidation, and lipases for methanolysis.

Industrially relevant phosgenation mechanisms of 2,4-toluenediamine (2,4-TDA) were investigated using G3MP2B3 model chemistry. Six reaction pathways had been explored, which resulted in the formation of toluene diisocyanate (2,4-TDI) including different scenarios of the ‘phosgenations first’ and ‘consecutive phosgenations’ mechanisms in both gas and condensed phases. Two possible ‘phosgenations first’ mechanisms show superior to the others in terms of energy, regardless of which phases are considered. Due to the o-dichlorobenzene (ODCB) solvation, the reaction barriers are dramatically reduced compared to the gas-phase reaction mechanism and the solvent effect can be described by linear relationship. Standard enthalpy of formation value was also recommended for 2,4-TDA (59.3 kJ/mol) and 2,4-TDI (−94.1 kJ/mol), as well as for the gas-phase intermediates (IM).