Effect of ion to ligand ratio on the aqueous to organic relative solubility of a lanthanide-ligand complex.

In the solvent extraction of rare earth elements, mechanistic aspects remain unclear regarding where and how extractant molecules coordinate metal ions and transport them from the aqueous phase into the organic phase. Molecular dynamics simulations were used to examine how unprotonated di(2-ethylhexyl)phosphoric acid (DEHP-) ligands that coordinate the Gd3+ ion can transfer the ion across the water-organic interface. Using the umbrella sampling technique, potential of mean force profiles were constructed to quantify the relative solubility of the Gd3+ ion coordinated to 0-3 DEHP- ligands in either water, 1-octanol, or hexane solvents and at the water-organic interfaces. The simulations show the Gd-DEHP- complexes, at varying Ln-ligand ratios, preferentially solvate on water-organic interfaces. While the Gd(DEHP-)3 complex will diffuse past the aqueous-organic interface into the octanol solvent, it is thermodynamically preferred for the Gd(DEHP-)3 complex to remain in the water-hexane interface when there is no amphiphilic layer of excess ligand.

Chelator-Assisted Precipitation-Based Separation of the Rare Earth Elements Neodymium and Dysprosium from Aqueous Solutions.

The rare earth elements (REEs) are critical resources for many clean energy technologies, but are difficult to obtain in their elementally pure forms because of their nearly identical chemical properties. Here, an analogue of macropa, G-macropa, was synthesized and employed for an aqueous precipitation-based separation of Nd3+ and Dy3+. G-macropa maintains the same thermodynamic preference for the large REEs as macropa, but shows smaller thermodynamic stability constants. Molecular dynamics studies demonstrate that the binding affinity differences of these chelators for Nd3+ and Dy3+ is a consequence of the presence or absence of an inner-sphere water molecule, which alters the donor strength of the macrocyclic ethers. Leveraging the small REE affinity of G-macropa, we demonstrate that within aqueous solutions of Nd3+, Dy3+, and G-macropa, the addition of HCO3- selectively precipitates Dy2(CO3)3, leaving the Nd3+-G-macropa complex in solution. With this method, remarkably high separation factors of 841 and 741 are achieved for 50:50 and 75:25 mixtures. Further studies involving Nd3+:Dy3+ ratios of 95:5 in authentic magnet waste also afford an efficient separation as well. Lastly, G-macropa is recovered via crystallization with HCl and used for subsequent extractions, demonstrating its good recyclability.

Molecular characterization of a rare case of high-grade B-cell lymphoma with MYC, BCL2, BCL6, and CCND1 rearrangements.

Quadruple-hit lymphomas are extremely rare non-Hodgkin lymphomas with a reported dismal prognosis in the few reported cases. A "quadruple hit" has been defined by the presence of concurrent MYC, BCL2, BCL6, and CCND1 chromosomal rearrangements. We report a new case of a quadruple hit lymphoma in a 73-year-old Hispanic man who presented with an enlarging left-sided neck mass. Computed tomography showed a 1.9-cm mass in left the tonsil with bulky cervical lymphadenopathy. The presence of all four chromosomal rearrangements can reportedly occur with disease progression in both diffuse large B-cell lymphomas and mantle cell lymphomas. Further characterization of the tumor by next-generation sequencing may be of benefit to delineate between these two possibilities. Immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and next-generation sequencing were used to confirm and classify the diagnosis. Histologic sections of the cervical lymph node demonstrated an atypical lymphoid infiltrate with large and pleomorphic cells, which were positive for CD20, CD10, BCL1 (Cyclin D1), BCL2, BCL6, and cMYC and negative for CD5 and SOX11 on immunohistochemistry with a Ki-67 proliferative index of 70%. FISH demonstrated MYC, BCL2, BCL6, and CCND1 rearrangements and the diagnosis of high-grade B-cell lymphoma with MYC, BCL2, BCL6, and CCND1 was rendered. Our patient was treated with dose adjusted etoposide, doxorubicin, cyclophosphamide, prednisone, and rituximab chemotherapy and has been in remission for 20 months.

Disseminated Anaplastic Lymphoma Kinase (ALK)-Positive T-cell Lymphoma Involving the Uterus and Cervix: A Case Report.

Primary or secondary non-Hodgkin lymphomas (NHLs) involving the female gynecologic tract are rare. T-cell subtypes are further rare and portend a worse prognosis. We present a case of a 23-year-old female presenting with a cervical mass accompanied by constitutional symptoms and abnormal vaginal bleeding. Immunohistochemistry studies revealed the presence of disseminated T-cell non-Hodgkin lymphoma that was anaplastic lymphoma kinase (ALK)-positive. The patient demonstrated a complete response to systemic chemotherapy initially and again after the relapse of the disease one year after diagnosis. To our knowledge, this is the first case of an ALK-positive T-cell lymphoma with secondary involvement of the uterus and cervix; all previously published cases of this histologic subtype in the gynecologic tract describe primary disease of the vagina. This case emphasizes the importance of immunohistochemistry studies inclusive of T-cell and B-cell markers when evaluating biopsies from cervical tumors to render the appropriate diagnosis and guide systemic therapy.

Efficacy, safety, and tolerability of adjunctive eslicarbazepine acetate in patients with focal to bilateral tonic-clonic seizures.

OBJECTIVE: To report the efficacy, safety, and tolerability of adjunctive eslicarbazepine acetate (ESL) treatment in reducing focal to bilateral tonic-clonic seizures (FBTCS). METHODS: Data were pooled from 3 randomized clinical trials (RCTs) of adjunctive ESL in patients with focal seizures. Patients treated with 800 or 1200 mg/day ESL and who experienced ≥ 1 FBTCS during baseline were included. Efficacy was measured using FBTCS standardized seizure frequency (SSF), responder rates (≥50%, ≥75%, and 100%), and time to first FBTCS. Adverse events (AEs) were tabulated for each subgroup. RESULTS: Of the original 1447 patients, 438 patients in the safety population were included with ≥ 1 FBTCS at baseline (efficacy population, n = 429). Patients with ≥ 2 FBTCS (safety, n = 354; efficacy, n = 346) and ≥ 3 FBTCS (safety, n = 294; efficacy, n = 288) at baseline were also analyzed. The 1200 mg/day ESL group experienced lower least squares mean SSF vs placebo in patients with ≥ 1 baseline FBTCS (P = 0.0395) and ≥ 3 baseline FBTCS (P = 0.0091). The 50% responder rates improved for 1200 mg/day ESL vs placebo (≥1 FBTCS, P = 0.005; ≥2 FBTCS, P = 0.0063; ≥3 FBTCS, P = 0.0016). The 75% responder rates improved with 1200 mg/day ESL vs placebo (≥1 FBTCS, P = 0.0315; ≥2 FBTCS, P = 0.0215; ≥3 FBTCS, P = 0.0099), and with 800 mg/day ESL for ≥ 2 FBTCS at baseline (P = 0.0486). The 100% responder rate was higher in patients treated with 1200 mg/day ESL (not significant). Time to first FBTCS was longer with both 800 (P = 0.0008) and 1200 mg/day (P = 0.0020) ESL vs placebo for the ≥ 1 FBTCS subgroup, and with 1200 mg/day ESL for ≥ 2 FBTCS (P = 0.0060) and ≥ 3 FBTCS (P = 0.0152) subgroups. Overall, AEs occurred at similar rates across subgroups, and were lower than the original RCTs. CONCLUSION: Adjunctive ESL produced a robust response in patients with FBTCS, a seizure type associated with SUDEP and high injury rates. Adjunctive ESL was well tolerated in patients who experienced FBTCS.

Acyltransferase families that act on thioesters: Sequences, structures, and mechanisms.

Acyltransferases (AT) are enzymes that catalyze the transfer of acyl group to a receptor molecule. This review focuses on ATs that act on thioester-containing substrates. Although many ATs can recognize a wide variety of substrates, sequence similarity analysis allowed us to classify the ATs into fifteen distinct families. Each AT family is originated from enzymes experimentally characterized to have AT activity, classified according to sequence similarity, and confirmed with tertiary structure similarity for families that have crystallized structures available. All the sequences and structures of the AT families described here are present in the thioester-active enzyme (ThYme) database. The AT sequences and structures classified into families and available in the ThYme database could contribute to enlightening the understanding acyl transfer to thioester-containing substrates, most commonly coenzyme A, which occur in multiple metabolic pathways, mostly with fatty acids.

Face Mask and Tear Film Stability: A Pilot Study of the Objective Measurement of Tear Break-Up Time.

(1) Background: Mask-associated dry eye (MADE) has been associated with increased dry eye symptoms, apparently due to reduced tear break-up time (TBUT). This study aimed to determine the short-term impact of surgical face mask (FM) on tear film stability by measuring non-invasive tear break-up time (NIBUT). (2) Methods: Twenty-six healthy participants had NIBUT evaluated without FM, with surgical FM and with a surgical FM secured to the skin with adhesive tape (TFM). NIBUT-first was measured with Keratograph 5M (K5M, Oculus, Wetzlar, Germany). Each participant had NIBUT measured in four sessions on four consecutive days. Session 1: without FM vs. with FM. Session 2: with FM vs. without FM. Session 3: without FM vs. with TFM. Session 4: with TFM vs. without FM (3). The time between each measured setting was 2 min. Results: The mean ± SD NIBUT without FM was 8.9 ± 3.7, with FM 10.2 ± 4.1, and with TFM 8.4 ± 3.8 s. No significant differences were observed in NIBUT in any of the evaluated settings: without FM vs. with FM (p = 0.247), without FM vs. with TFM (p = 0.915), and with FM vs. with TFM (p = 0.11). (4) Conclusions: This study did not find a significant short-term effect of FM on NIBUT. Other variables or longer periods of exposure might trigger the symptoms and ocular surface alterations in MADE.

Correction: The solution structures and relative stability constants of lanthanide-EDTA complexes predicted from computation.

Correction for 'The solution structures and relative stability constants of lanthanide-EDTA complexes predicted from computation' by Ravi D. O'Brien et al., Phys. Chem. Chem. Phys., 2022, 24, 10263-10271, https://doi.org/10.1039/D2CP01081J.

Time to sustained responder status in patients with focal seizures treated with adjunctive eslicarbazepine acetate.

Rapid and sustained clinical responses are critical in improving long-term outcomes in epilepsy. While a 50 % reduction from baseline in standardized seizure frequency (SSF) is often cited as a measure of clinically meaningful efficacy, sustained response (SR) is an alternative method that allows the assessment of onset and durability of the response. Time to sustained response in SSF of ≥ 50 %, ≥ 75 %, ≥ 90 %, and 100 % was assessed for pooled data from 3 similar randomized clinical trials of adjunctive eslicarbazepine acetate (ESL). Patients with focal seizures on stable doses of 1-2 antiseizure medications were randomized to placebo, ESL 800 mg/day, or ESL 1200 mg/day. SR50, SR75, SR90, and SR100 were defined as a ≥ 50 %, ≥ 75 %, ≥ 90 %, and 100 % reduction, respectively, in SSF compared to baseline occurring anytime during the 12-week maintenance period, sustained through the end of the maintenance period. Safety signals were assessed for patients with SR50 onset within the first 2 weeks of the maintenance period (early responders) and any point following the first 2 weeks (later responders). A total of 1221 patients were included in this analysis. SR50 was achieved as early as Day 1 (placebo, 4.7 %; ESL 800 mg/day, 8.8 %; ESL 1200 mg/day, 10.4 %). After 84 days, SR50 was achieved by 32.1 % of the placebo group, 46.9 % of the ESL 800 mg/day group (p = 0.0002 vs placebo), and 53.7 % of the ESL 1200 mg/day group (p < 0.0001 vs placebo). Both ESL groups demonstrated earlier SR50 onset compared with placebo (p < 0.0001). Time to SR50 onset was not statistically different between the 800 and 1200 mg/day ESL dose groups. SR75 (p = 0.0001), SR90 (p = 0.0019), and SR100 (p = 0.0014) were achieved significantly earlier in the ESL 1200 mg/day groups vs placebo. SR75 was achieved significantly earlier in the ESL 800 mg/day group vs placebo (p = 0.0188), while achievements of SR90 (p = 0.0525) and SR100 (p = 0.0540) trended toward earlier occurrence. A greater proportion of patients in the ESL groups compared to the placebo group achieved an SR50 during the maintenance period, and those patients in the ESL groups also achieved SR50 and SR75 sooner than placebo treated patients. Additionally, patients treated with the higher ESL dose achieved SR90 and SR100 sooner than those treated with placebo.

Long-term quality of life in patients with focal seizures treated with adjunctive eslicarbazepine acetate.

By controlling seizures, anti-seizure medications can improve health-related quality of life (HRQOL). Data from a post-hoc pooled analysis of adjunctive eslicarbazepine acetate (ESL) was used to describe HRQOL measures, including overall quality of life, seizure worry, emotional well-being, energy/fatigue, cognitive functioning, medication effects, social function, and overall score over a period of up to one year. Patients who completed a double-blind treatment phase (Part 1) of these trials were eligible to enter the open label extension (OLE; Part 2). Patients who continued into the OLE initiated adjunctive ESL at 800 mg/day for 1 month before investigators could titrate dosages based on efficacy and tolerability. HRQOL was measured at baseline and at the last assessment using the Quality of Life in Epilepsy Inventory (QOLIE-31) in all patients who entered the 1-year OLE and in patients who completed the 1-year OLE. The mean QOLIE-31 scores and mean change in scores were analyzed using paired t-tests. The percentage of patients with improvements in QOLIE-31 scores beyond the minimally important change (MIC) threshold from baseline to end of 1-year OLE is described. Of 1410 patients in the intent-to-treat population, 1120 patients continued to part 2, and 795 patients completed the OLE. In patients who entered the OLE, mean improvements in scores for seizure worry, overall quality of life, emotional well-being, medication side effects, social functioning, and total score were statistically significant. In patients who completed the OLE, the mean change to final assessment was statistically significantly improved for all QOLIE categories. In patients who entered the OLE with a final assessment, the percentage of patients meeting the MIC for social functioning was the highest (46.9%), followed by medication effects (44.9%), and seizure worry (42.9%). Patients who completed the OLE with a final assessment found a similar rank ordering in QOLIE scale improvements compared with those who entered the OLE with a final assessment. For both sets of patient groups, the least number of subjects met MIC criteria for the energy/fatigue QOLIE category. Treatment with therapeutic doses of adjunctive ESL in patients with focal seizures was associated with improvements in HRQOL for a period of up to one year.

Mutation Space of Spatially Conserved Amino Acid Sites in Proteins.

The mutation space of spatially conserved (MSSC) amino acid residues is a protein structural quantity developed and described in this work. The MSSC quantifies how many mutations and which different mutations, i.e., the mutation space, occur in each amino acid site in a protein. The MSSC calculates the mutation space of amino acids in a target protein from the spatially conserved residues in a group of multiple protein structures. Spatially conserved amino acid residues are identified based on their relative positions in the protein structure. The MSSC examines each residue in a target protein, compares it to the residues present in the same relative position in other protein structures, and uses physicochemical criteria of mutations found in each conserved spatial site to quantify the mutation space of each amino acid in the target protein. The MSSC is analogous to scoring each site in a multiple sequence alignment but in three-dimensional space considering the spatial location of residues instead of solely the order in which they appear in a protein sequence. MSSC analysis was performed on example cases, and it reproduces the well-known observation that, regardless of secondary structure, solvent-exposed residues are more likely to be mutated than internal ones. The MSSC code is available on GitHub: "https://github.com/Cantu-Research-Group/Mutation_Space".

Analysis of the First Ion Coordination Sphere: A Toolkit to Analyze the Coordination Sphere of Ions.

Rapid and accurate approaches to characterizing the coordination structure of an ion are important for designing ligands and quantifying structure-property trends. Here, we introduce AFICS (Analysis of the First Ion Coordination Sphere), a tool written in Python 3 for analyzing the structural and geometric features of the first coordination sphere of an ion over the course of molecular dynamics simulations. The principal feature of AFICS is its ability to quantify the distortion a coordination geometry undergoes compared to uniform polyhedra. This work applies the toolkit to analyze molecular dynamics simulations of the well-defined coordination structure of aqueous Cr3+ along with the more ambiguous structure of aqueous Eu3+ chelated to ethylenediaminetetraacetic acid. The tool is targeted for analyzing ions with fluxional or irregular coordination structures (e.g., solution structures of f-block elements) but is generalized such that it may be applied to other systems.

Solution Structures of Europium Terpyridyl Complexes with Nitrate and Triflate Counterions in Acetonitrile.

Lanthanide-ligand complexes are key components of technological applications, and their properties depend on their structures in the solution phase, which are challenging to resolve experimentally or computationally. The coordination structure of the Eu3+ ion in different coordination environments in acetonitrile is examined using ab initio molecular dynamics (AIMD) simulations and extended X-ray absorption fine structure (EXAFS) spectroscopy. AIMD simulations are conducted for the solvated Eu3+ ion in acetonitrile, both with or without a terpyridyl ligand, and in the presence of either triflate or nitrate counterions. EXAFS spectra are calculated directly from AIMD simulations and then compared to experimentally measured EXAFS spectra. In acetonitrile solution, both nitrate and triflate anions are shown to coordinate directly to the Eu3+ ion forming either ten- or eight-coordinate solvent complexes where the counterions are binding as bidentate or monodentate structures, respectively. Coordination of a terpyridyl ligand to the Eu3+ ion limits the available binding sites for the solvent and anions. In certain cases, the terpyridyl ligand excludes any solvent binding and limits the number of coordinated anions. The solution structure of the Eu-terpyridyl complex with nitrate counterions is shown to have a similar arrangement of Eu3+ coordinating molecules as the crystal structure. This study illustrates how a combination of AIMD and EXAFS can be used to determine how ligands, solvent, and counterions coordinate with the lanthanide ions in solution.

Time to baseline seizure count in patients with focal seizures receiving adjunctive eslicarbazepine acetate in a phase IV clinical trial.

BACKGROUND: The efficacy and tolerability of eslicarbazepine acetate (ESL), a once-daily, orally-administered, anti-seizure medication (ASM), have primarily been established in treatment-resistant epilepsy patients, the population most often enrolled in clinical trials of anti-seizure medications. More recently, ESL was also shown to be effective and well-tolerated as first adjunctive therapy in non-treatment-resistant patients in an open-label, non-randomized, Phase IV, 24-week study of ESL using standard efficacy parameters in adults with focal seizures. OBJECTIVE: To determine the time required to reach baseline seizure count, as an alternative method of assessing the efficacy of adjunctive ESL in patients with relatively low baseline monthly seizure frequencies. This additional analysis was undertaken, as subtle changes and improvements are difficult to analyze using standard efficacy parameters, such as standardized seizure frequency reduction when the baseline frequency of seizures is particularly low. METHODS: This was a post-hoc analysis of the Phase IV study data, which investigated time to baseline seizure count in patients aged ≥ 18 years with focal seizures as an alternative measure of anti-seizure efficacy. In the Phase IV trial, patients had been enrolled into 2 groups: Arm 1: ESL as first adjunctive therapy to levetiracetam (LEV) or lamotrigine (LTG), the two most commonly-prescribed ASMs, in patients with inadequate response to treatment; Arm 2: ESL as a later adjunctive therapy, following prior use of 1-2 ASMs in patients who required an additional therapeutic option. RESULTS: The time to reach individual baseline seizure count was longer in patients with focal seizures receiving ESL as a first (Arm 1) versus later (Arm 2) adjunctive therapy (p = 0.005). Patients who received ESL as a first adjunctive therapy had a longer time to ESL discontinuation than patients who received ESL as a later adjunctive therapy (p = 0.04). In Arm 1, patients receiving concomitant LTG reported treatment-emergent adverse events (TEAEs) significantly earlier than those receiving LEV (p = 0.02). Compared to patients receiving concomitant LTG, a greater number of patients in Arm 1 who were taking concomitant LEV had a modal ESL dose > 1200 mg and completed the full maintenance period. A greater number of patients in Arm 1 who were receiving concomitant LEV and completed the 24-week maintenance period reached a maximum ESL dose of 1600 mg, compared to those taking LTG, who reached a maximum ESL dose of 1200 mg. CONCLUSIONS: This analysis of the Phase IV clinical trial data provides an alternative way of assessing efficacy beyond standardized seizure frequency reduction, in the context of relatively low monthly median seizure frequencies at baseline (SSF 2.0-2.4). These results provide further support for the use of ESL as an earlier or later adjunctive therapy to LEV or LTG.

Gastrointestinal manifestations, risk factors, and management in patients with post-transplant lymphoproliferative disorder: A systematic review.

BACKGROUND: Patients with a history of solid organ transplantation (SOT) or hematopoietic stem cell transplantation (HSCT) are at an increased risk of developing post-transplant lymphoproliferative disorder (PTLD). The gastrointestinal (GI) tract is commonly affected as it has an abundance of B and T cells. AIM: To determine typical GI-manifestations, risk factors for developing PTLD, and management. METHODS: Major databases were searched until November 2021. RESULTS: Non-case report studies that described GI manifestations of PTLD, risk factors for developing PTLD, and management of PTLD were included. Nine articles written within the last 20 years were included in the review. All articles found that patients with a history of SOT, regardless of transplanted organ, have a propensity to develop GI-PTLD. CONCLUSION: GI tract manifestations may be nonspecific; therefore, consideration of risk factors is crucial for identifying GI-PTLD. Like other lymphoma variants, PTLD is very aggressive making early diagnosis key to prognosis. Initial treatment is reduction of immunosuppression which is effective in more than 50% of cases; however, additional therapy including rituximab, chemotherapy, and surgery may also be required.

Water Defect Stabilizes the Bi3+ Lone-Pair Electronic State Leading to an Unusual Aqueous Hydration Structure.

The aqueous hydration structure of the Bi3+ ion is probed using a combination of extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT) simulations of ion-water clusters and condensed-phase solutions. Anomalous features in the EXAFS spectra are found to be associated with a highly asymmetric first-solvent water shell. The aqueous chemistry and structure of the Bi3+ ion are dramatically controlled by the water stabilization of a lone-pair electronic state involving the mixed 6s and 6p orbitals. This leads to a distinct multimodal distribution of water molecules in the first shell that are separated by about 0.2 Å. The lone-pair structure is stabilized by a collective response of multiple waters that are localized near the lone-pair anti-bonding site. The findings indicate that the lone-pair stereochemistry of aqueous Bi3+ ions plays a major role in the binding of water and ligands in aqueous solutions.

Psychiatric adverse events in three phase III trials of eslicarbazepine acetate for focal seizures.

OBJECTIVE: Eslicarbazepine acetate (ESL) is a once-daily (QD), oral anti-seizure medication for the treatment of focal (partial-onset) seizures. Here, we evaluate risk factors for the development of psychiatric treatment-emergent adverse events (TEAEs) in clinical trials of adjunctive ESL in adults with focal seizures. METHODS: This post-hoc analysis evaluated data pooled from three Phase III, randomized, double-blind, placebo-controlled trials (BIA-2093-301, -302, -304). After an 8-week baseline period, patients were randomized equally to receive placebo, ESL 400 mg (not reported here), 800 mg, or 1200 mg QD (up to 2-week titration; 12-week maintenance; optional open-label extension [OLE]). Incidences of psychiatric TEAEs were evaluated according to three separate criteria: medical history of psychiatric disorders (yes/no); baseline use of psychotropic drugs (yes/no); Montgomery-Åsberg Depression Rating Scale (MADRS) score at baseline (0-6: normal; 7-19: mild depression; 20-34: moderate depression). RESULTS: The analysis populations comprised 1251 patients for the controlled study period and 1137 patients for the 1-year OLE. Psychiatric TEAE incidence was similar between patients taking ESL and placebo in the controlled and OLE study periods and was not related to ESL dose. Psychiatric TEAEs generally occurred more frequently in patients with a medical history of psychiatric disorders, using psychotropic drugs, or with depressive symptoms than in those without a history, not using psychotropic drugs, or with no depressive symptoms. Depression and anxiety were the most frequently reported psychiatric TEAEs. SIGNIFICANCE: Overall, in clinical trials of ESL in adults with focal seizures, incidences of psychiatric events were not statistically different between patients taking ESL and placebo, were not related to ESL dose, and generally occurred more frequently in patients with baseline psychiatric symptoms or a history of psychiatric disorders. Long-term exposure to ESL was not associated with a marked increase in the incidence of psychiatric TEAEs.

The solution structures and relative stability constants of lanthanide-EDTA complexes predicted from computation.

Ligand selectivity to specific lanthanide (Ln) ions is key to the separation of rare earth elements from each other. Ligand selectivity can be quantified with relative stability constants (measured experimentally) or relative binding energies (calculated computationally). The relative stability constants of EDTA (ethylenediaminetetraacetic acid) with La3+, Eu3+, Gd3+, and Lu3+ were predicted from relative binding energies, which were quantified using electronic structure calculations with relativistic effects and based on the molecular structures of Ln-EDTA complexes in solution from density functional theory molecular dynamics simulations. The protonation state of an EDTA amine group was varied to study pH ∼7 and ∼11 conditions. Further, simulations at 25 °C and 90 °C were performed to elucidate how structures of Ln-EDTA complexes varying with temperature are related to complex stabilities at different pH conditions. Relative stability trends are predicted from computation for varying Ln3+ ions (La, Eu, Gd, Lu) with a single ligand (EDTA at pH ∼11), as well as for a single Ln3+ ion (La) with varying ligands (EDTA at pH ∼7 and ∼11). Changing the protonation state of an EDTA amine site significantly changes the solution structure of the Ln-EDTA complex resulting in a reduction of the complex stability. Increased Ln-ligand complex stability is correlated to reduced structural variations in solution upon an increase in temperature.

Advanced Theory and Simulation to Guide the Development of CO2 Capture Solvents.

Increasing atmospheric concentrations of greenhouse gases due to industrial activity have led to concerning levels of global warming. Reducing carbon dioxide (CO2) emissions, one of the main contributors to the greenhouse effect, is key to mitigating further warming and its negative effects on the planet. CO2 capture solvent systems are currently the only available technology deployable at scales commensurate with industrial processes. Nonetheless, designing these solvents for a given application is a daunting task requiring the optimization of both thermodynamic and transport properties. Here, we discuss the use of atomic scale modeling for computing reaction energetics and transport properties of these chemically complex solvents. Theoretical studies have shown that in many cases, one is dealing with a rich ensemble of chemical species in a coupled equilibrium that is often difficult to characterize and quantify by experiment alone. As a result, solvent design is a balancing act between multiple parameters which have optimal zones of effectiveness depending on the operating conditions of the application. Simulation of reaction mechanisms has shown that CO2 binding and proton transfer reactions create chemical equilibrium between multiple species and that the agglomeration of resulting ions and zwitterions can have profound effects on bulk solvent properties such as viscosity. This is balanced against the solvent systems needing to perform different functions (e.g., CO2 uptake and release) depending on the thermodynamic conditions (e.g., temperature and pressure swings). The latter constraint imposes a "Goldilocks" range of effective parameters, such as binding enthalpy and pK a, which need to be tuned at the molecular level. The resulting picture is that solvent development requires an integrated approach where theory and simulation can provide the necessary ingredients to balance competing factors.