Anionic Amino Acids Research Articles

Efficient Cellulose Dissolution and Film Formation Enabled by Superbase Amino Acid Ionic Liquids.

Cellulose is a promising feedstock for the production of sustainable materials. To fully utilize its potential, exploring efficient cellulose solvents is a paramount prerequisite. In this study, ten superbase amino acid ionic liquids (SAAILs) are synthesized using 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) with different amino acid anions via a simple neutralization method. The properties of these SAAILs, such as viscosity and glass transition temperature, varied with their cation and anion structures. The ability of the SAAILs to dissolve cellulose is related to their Kamlet-Taft parameters, particularly hydrogen bond basicity (β). The main driving force for cellulose dissolution in SAAILs is thought to be hydrogen bonding interactions between SAAILs and cellulose hydroxyl groups. Four SAAILs composed of DBN or DBU cations and proline, or aspartic acid anions are identified as promising solvents for preparing regenerated cellulose films (RCFs). The RCF prepared from [DBN]Proline(Pro) showed a favorable combination of high tensile strength (76.9MPa), high Young's modulus (5201.2MPa), good transparency (≈70% at 550nm), and smooth surface morphology. These halogen- and metal-free SAAILs show the potential to provide a new avenue for cellulose processing.

Stability and rheological properties of foams co-stabilized by hydrophilic silica nanoparticles and amino acid/alkyl glycoside surfactants

Foams stabilized by nanoparticles (NPs) and surfactants have potential applications in the development of new environmentally friendly firefighting foams. In the present study, the mixed dispersions of anionic amino acid surfactant (SLG), nonionic alkyl glycoside surfactant (APG0810), and silica NPs were prepared. The influence of silica NPs on foamability, foam drainage, foam coarsening, and foam rheological properties of the mixture of SLG/APG0810 was systematically investigated. Results indicate that the presence of NPs results in decrease in conductivity and surface tension of the mixed dispersion. The viscosity of the mixed dispersions slightly decreases and then increases, while the foamability decreases following an increase with increasing NP concentration. The apparent viscosity of the mixed dispersions decreases over shear rate. The increase in NP concentration leads to rapid increase in viscoelastic modulus of the mixed dispersions and foams. The presence of NPs with concentration below 1 wt% results in acceleration of foam drainage and coarsening, while the presence of NPs with concentration above 1 wt% leads to deceleration of foam drainage and coarsening. This study offers theoretical support for the use of NPs in fluorine-free firefighting foams.

Microstructures of Choline Amino Acid based Biocompatible Ionic Liquids.

Bio-compatible ionic liquids (Bio-ILs) represent a class of solvents with peculiar properties and exhibit huge potential for their applications in different fields of chemistry. Ever since they were discovered, researchers have used bio-ILs in diverse fields such as biomass dissolution, CO2 sequestration, and biodegradation of pesticides. This review highlights the ongoing research studies focused on elucidating the microscopic structure of bio-ILs based on cholinium cation ([Ch]+ ) and amino acid ([AA]- ) anions using the state-of-the-art and classical molecular dynamics (MD) simulations. The microscopic structure associated with these green ILs guides their suitability for specific applications. ILs of this class differ in the side chain of the amino acid anions, and varying the side chain significantly affects the structure of these ILs and thus helps in tuning the efficiency of biomass dissolution. This review demonstrates the central role of the side chain on the morphology of choline amino acid ([Ch][AA]) bio-ILs. The seemingly matured field of bio-ILs and their employment in various applications still holds significant potential, and the insights on their microscopic structure would steer the field of target specific application of these green ILs.

Shield, Anchor, and Adhesive Roles of Methylene Blue in Tyrosinase Adsorbed on Carbon Felt for a Flow Injection Amperometric Enzyme Biosensor for Phenolic Substrates and Inhibitors.

Methylene blue (MB) acted as a stabilizer for preventing surface-induced denaturation of tyrosinase (TYR) adsorbed on a carbon felt (CF) surface, which is based on shield and anchor roles preventing the unfavorable conformational change of TYR on the hydrophobic CF surface. Furthermore, MB acted as an effective adhesive for TYR immobilization on CF. The resulting TYR and MB coadsorbed CF (TYR/MB-CF) worked as an excellent working electrode unit in an electrochemical detector in a flow injection amperometric biosensor, which allowed highly sensitive consecutive determination of not only TYR substrates but also competitive inhibitors. Simultaneous adsorption of TYR and MB from their mixed solution was much useful as compared with step-wise separated adsorption of TYR on the MB-adsorbed CF, which suggests that the binding interaction of MB with TYR in the solution phase is important for this phenomenon. Fluorescence and UV-vis spectroscopy revealed that not only electrostatic forces between the cationic MB and anionic amino acid residues of TYR but also hydrophobic interactions via the phenothiazine ring of MB play a principal binding driving force of MB with TYR at the surface of the TYR molecules. Synchronous fluorescence, three-dimensional fluorescence, and circular dichroism (CD) spectroscopy clarified that the conformation and the secondary structure of TYR slightly changed upon the MB binding, implying that MB binding leads to the modification of the original intramolecular bonding in part.

Mitochondrial ATP Synthase and Mild Uncoupling by Butyl Ester of Rhodamine 19, C4R1.

The homeostasis of the transmembrane potential of hydrogen ions in mitochondria is a prerequisite for the normal mitochondrial functioning. However, in different pathological conditions it is advisable to slightly reduce the membrane potential, while maintaining it at levels sufficient to produce ATP that will ensure the normal functioning of the cell. A number of chemical agents have been found to provide mild uncoupling; however, natural proteins residing in mitochondrial membrane can carry this mission, such as proteins from the UCP family, an adenine nucleotide translocator and a dicarboxylate carrier. In this study, we demonstrated that the butyl ester of rhodamine 19, C4R1, binds to the components of the mitochondrial ATP synthase complex due to electrostatic interaction and has a good uncoupling effect. The more hydrophobic derivative C12R1 binds poorly to mitochondria with less uncoupling activity. Mass spectrometry confirmed that C4R1 binds to the β-subunit of mitochondrial ATP synthase and based on molecular docking, a C4R1 binding model was constructed suggesting the binding site on the interface between the α- and β-subunits, close to the anionic amino acid residues of the β-subunit. The association of the uncoupling effect with binding suggests that the ATP synthase complex can provide induced uncoupling.

Does side chain group of anion affect absorption of SO2 in amino acid ionic liquid?

1-propyl-3-methylimidazolium cation with glycinate, alaninate, valinate, leucinate, cysteinate, and serinate as amino acid anions were selected as the counter ions to study the effect of the side chain group of anions on the absorption of SO2. One can see that the enlargement of the alkyl group from glycinate to leucinate leads to a slight decrease in gas absorption interaction energy; changing the side chain group to the methyl thiol (cysteinate) and methyl alcohol (serinate), drastically changes gas nteraction energy with the same trend in absorption Gibbs energy. In addition, the charge transfer between the imidazolium-based amino acid ionic liquid and captured gas as well as the distance between anion and the absorbed SO2 gas in glycinate is the lowest which can be the main reason for being the most favorable absorbent in the present study. A deep insight into the nature of interactions sheds light on the difference in the distribution of van der Waals (vdW) interaction that plays the essential role in the SO2 capturing; in other words, vdW distribution in the glycinate system is concentrated and clear while in the other systems, this distribution is observed in a scattered manner.

Tracing the Effect of Replacing [Gly]- with [Ala]- and Hydroxylation of [emim]+ on the Fine-Tuning of the Transport Properties of the Corresponding Amino Acid-Based Ionic Liquids Using MD Simulation.

Natural amino acid-based ionic liquids (AAILs) composed of deprotonated amino acids, [AA]-, as anions and hydroxylated imidazolium cations provide an eco-friendly nontoxic IL family with the growing number of chemical and biochemical revolutionary applications. In this paper, the transport properties of four AAILs composed of 1-(2-hydroxyethyl)-3-methylimidazolium ([HOemim]+) and 1-ethyl-3-methylimidazolium ([emim]+) cations with alaninate and glycinate anions were studied by molecular dynamics (MD) simulations. A nonpolarizable all-atom force field with the scaled charge (±0.8e) on each of the ions was applied and compared with the unit charge model in some cases. The tunable effects of the presence of the hydroxyl group in the side chain of the imidazolium cation, the type of amino acid anion, and the varied temperature on the dynamical behavior of AAILs were investigated in detail. The experimentally compatible trends of the simulated ionic self-diffusion coefficients, ionic conductivity, and ionicity were found to be inverse to the viscosity and ionic association of these ILs as [emim][Gly] > [emim][Ala] > [HOemim][Gly] > [HOemim][Ala]. The main reason behind these trends is the higher ability of the hydroxylated cation for the hydrogen-bond formation with [AA]-. The mean square displacement (MSD), self-diffusion, and transference number of imidazolium cations are larger than those of [AA]- anions, except in the case of [HOemim][Gly]. It was found that the activation energy for diffusion of [AA]- is lower than that of [HOemim]+ but higher than that of [emim]+ in [HOemim][AA] and [emim][AA] ILs, respectively. The computed velocity autocorrelation function (VACF) showed that [Gly]-, as the lightest ion, has the shortest mean collision time and velocity randomization time among the ions, especially in the [HOemim][Gly] IL. Replacing [emim]+ with [HOemim]+, similar to the effect of decreasing temperature, causes significant decreasing of the ionic self-diffusion and increasing of the well depth of the first minimum of the ionic VACFs. Current findings show that introducing suitable functional groups in the side chain of imidazolium cations can be a viable approach for efficient engineering design and fine-tuning of the transport properties of these AAILs.

Greener approach for the separation of naphthenic acid from model oil using Pyrrolidinium-based amino acid ionic liquids

Four novel pyrrolidinium-based amino acid ionic liquids were synthesized and characterized. The physicochemical properties of these amino acid ionic liquids (AAILs), such as viscosity, density, thermal stability, and surface tension were investigated. These ionic liquids (ILs) were used as a green chemistry approach for the extraction of naphthenic acid from the model oil. The influence of amino acid anions on the de-acidification process was assessed by attaching prolinate, glycinate, alaninate and serinate. Extraction results show that very small amounts of ILs are sufficient to extract naphthenic acid from a model oil configuration with a high total acid number. The regeneration and reusability of the synthesized ILs have also been analysed in this work. Moreover, the antimicrobial activity assay was performed to ascertain the potential toxicological effect of the synthesized set on the aquatic system.

Reaction Mechanism of CO2 with Choline-Amino Acid Ionic Liquids: A Computational Study.

Carbon capture and sequestration are the major applied techniques for mitigating CO2 emission. The marked affinity of carbon dioxide to react with amino groups is well known, and the amine scrubbing process is the most widespread technology. Among various compounds and solutions containing amine groups, in biodegradability and biocompatibility perspectives, amino acid ionic liquids (AAILs) are a very promising class of materials having good CO2 absorption capacity. The reaction of amines with CO2 follows a multi-step mechanism where the initial pathway is the formation of the C-N bond between the NH2 group and CO2. The added product has a zwitterionic character and can rearrange to give a carbamic derivative. These steps of the mechanism have been investigated in the present study by quantum mechanical methods by considering three ILs where amino acid anions are coupled with choline cations. Glycinate, L-phenylalanilate and L-prolinate anions have been compared with the aim of examining if different local structural properties of the amine group can affect some fundamental steps of the CO2 absorption mechanism. All reaction pathways have been studied by DFT methods considering, first, isolated anions in a vacuum as well as in a liquid continuum environment. Subsequently, the role of specific interactions of the anion with a choline cation has been investigated, analyzing the mechanism of the amine-CO2 reaction, including different coupling anion-cation structures. The overall reaction is exothermic for the three anions in all models adopted; however, the presence of the solvent, described by a continuum medium as well as by models, including specific cation- -anion interactions, modifies the values of the reaction energies of each step. In particular, both reaction steps, the addition of CO2 to form the zwitterionic complex and its subsequent rearrangement, are affected by the presence of the solvent. The reaction enthalpies for the three systems are indeed found comparable in the models, including solvent effects.

Tailoring the self-assembly of lipid-based lyotropic liquid crystalline mesophases with biocompatible ionic liquid aqueous solutions

Interest in lipid-based lyotropic liquid crystalline nanoparticles (LCNPs) as drug delivery vehicles continues to grow, owing to their unique structural features. The structure of these particles can be controlled to suit specific applications, through tailoring the lipid composition and solvent conditions. Ionic liquids (ILs) are liquid salts comprising tailorable cations and anions, of which some are known to support the self-assembly of amphiphiles, and hence can be used as designer solvents for LCNPs. We employed dynamic light scattering, small angle X-ray scattering, and cryogenic transmission electron microscopy to examine the particle size and lyotropic liquid crystalline mesophase behavior of monoolein (MO)-based LCNPs in aqueous solutions containing 13 choline ILs with a selection of amino acid and carboxylate anions at 6 concentrations 20, 10, 5, 1, 0.33, and 0.16 wt%. Our results show the formation of LCNPs with various liquid crystalline nanostructures, including the inverse bicontinuous primitive cubic (Q2) phase with the Im3m crystallographic space group, the inverse hexagonal (H2), and the inverse discontinuous micellar cubic (I2) phases. The internal nanostructures of the MO nanoparticles depended on three main factors, the anion of the ILs, the IL concentration, and the pH of the solution. This study elucidates the potential application of IL solvents as a powerful tool to tailor the internal nanostructure of MO-based LCNPs, and advances the exploration of IL-enabled responsive LCNPs systems as prospective nanocarriers.

Amino acid ionic liquids as components of aqueous biphasic systems for L-tryptophan extraction: Experiment and thermodynamic modeling with ePC-SAFT equation of state

Aqueous biphasic systems (ABSs) based on ionic liquids (ILs) have been considered as promising for the extraction, purification and separation of a wide range of substances, including biomolecules. Among the structurally modified ILs, amino acid ILs (AAILs) attract special attention.In this work we obtain systematic experimental data on the partitioning of L-tryptophan in the aqueous mixtures of 1-alkyl-3-methylimidazolium AAILs, [Cnmim]X, with different hydrocarbon chain length (n = 4, 8) and amino acid anions: X = [Leu] (L-Leucinate), [Val] (L-Valinate), [Lys] (L-Lysinate), and inorganic salt (K3PO4). Our results show that the partition coefficients are higher in the ABSs with AAILs than with halide ILs. AAIL with [C8mim]+ cation demonstrate a noticeable specificity of lysinate anions. The obtained new data are discussed in terms of AAIL’s structure. We conclude that hydrogen bonding is likely to play the major role in partitioning of the solute. Taking into account the low toxicity of AAILs, these ABSs have a high potential for the extraction of small biomolecules.Moreover, we found that in the studied ABSs based on chiral AAILs, partitioning of D-tryptophan is equal to that for L-tryptophan.ePC-SAFT is applied for the first time to model liquid-liquid equlibrium in ternary ABSs containing AAILs and partitioning of L-tryptophan. We obtain satisfactory results and conclude that ePC-SAFT is a promising tool for modeling ABSs that contain AAIL and inorganic salt.

Generalized Approach towards Secretion-Based Protein Production via Neutralization of Secretion-Preventing Cationic Substrate Residues.

Many heterologous proteins can be secreted by bacterial ATP-binding cassette (ABC) transporters, provided that they are fused with the C-terminal signal sequence, but some proteins are not secretable even though they carry the right signal sequence. The invention of a method to secrete these non-secretable proteins would be valuable both for understanding the secretory physiology of ABC transporters and for industrial applications. Herein, we postulate that cationic “supercharged” regions within the target substrate protein block the secretion by ABC transporters. We also suggest that the secretion of such substrate proteins can be rescued by neutralizing those cationic supercharged regions via structure-preserving point mutageneses. Surface-protruding, non-structural cationic amino acids within the cationic supercharged regions were replaced by anionic or neutral hydrophilic amino acids, reducing the cationic charge density. The examples of rescued secretions we provide include the spike protein of SARS-CoV-2, glutathione-S-transferase, streptavidin, lipase, tyrosinase, cutinase, growth factors, etc. In summary, our study provides a method to predict the secretability and a tool to rescue the secretion by correcting the secretion-blocking regions, making a significant step in understanding the physiological properties of ABC transporter-dependent protein secretion and laying the foundation for the development of a secretion-based protein-producing platform.

Abstract SY31-04: Uncovering targetable dependencies of latent brain metastatic cells

Abstract Uncovering Targetable Dependencies of Latent Brain Metastatic Cells Srinivas Malladi, Department of Pathology, Harold C. Simmons Comprehensive Cancer Center, UT Southwestern Medical Center, Dallas, TX, 75390, USA ABSTRACT HER2+ breast cancer patients presenting with brain metastases have poor survival outcomes. Metachronous brain metastases or relapse are observed in approximately fifty percent of HER2+ breast cancer patients considered disease free after a variable length of time post primary diagnosis and treatment. Disseminated latent residual cells that survive current therapies are responsible for these relapses or metachronous metastasis. How disseminated tumor cells survive as latent/dormant entities for extended period before initiating metachronous metastasis is poorly understood. Moreover, the basis for disparate metastatic fitness among disseminated tumor cells of similar oncotype within a distal organ is unknown and vital for better clinical management. Through a phenotypic screen in mice, we have isolated HER2+ latent (Lat) and brain metastatic (BM) cells.Transcriptomic and metabolic profiles of these brain-tropic breast cancer cells identified actionable dependencies and unique therapeutic opportunities. Brain-tropic Lat and metastatic cells have distinct metabolic profiles that determine their metastatic fitness. Both latent and metastatic cells survive in equilibrium with innate immune surveillance, oxidize glutamine and maintain cellular redox homeostasis through the anionic amino acid transporter xCT. Likewise, xCT expression was significantly higher in matched metachronous brain metastatic samples compared to primary tumors from HER2+ breast cancer patients. Genetic or pharmacological blockade of xCT eradicates residual disease and brain metastatic relapse in these preclinical models. Lactate secreted by aggressive metastatic cells limits innate immune surveillance and triggers overt metastasis. Furthermore, transcriptomic analysis identified augmented AXL expression. Depleting or inhibiting AXL in these HER2 targeted therapy resistant brain-tropic cells attenuates metastatic incidence. In sum, by investigating phenotypically distinct brain-tropic latent and metastatic cells, we uncovered the impact of metabolic diversity and adaptations on metastatic fitness and identified targetable vulnerabilities. Citation Format: Srinivas Malladi. Uncovering targetable dependencies of latent brain metastatic cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr SY31-04.

Phosphorylated Serine-Modified Polyamidoamine Dendrimer as an Osteoid Surface-Targeting Drug Carrier.

The aim of this study was to develop a polyethylene glycol (PEG)-conjugated third-generation polyamidoamine dendrimer (PAMAM) with phosphorylated serine as an osteoid surface-targeting drug carrier for the treatment of bone diseases. We conjugated PAMAM backbones to l-serine and obtained Ser-PAMAM. Then, phosphoric acid and PEG were covalently bound to the Ser-PAMAM to generate PEGylated phosphorylated Ser-PAMAM (PEG-phosSer-PAMAM). Using osteoblast-like cells (MC3T3-E1 cells) cultured in 3D collagen gels, we showed that phosSer-PAMAM adsorbed both the hydroxyapatite and type I collagen components of the bone matrix. Fourier transform infrared spectroscopy analysis indicated that the phosphoryl side chains of phosSer-PAMAM formed electrostatic interactions and hydrogen bonds with the anionic amino acid residues of type I collagen. Mice were intravenously injected with the foregoing molecules, and a tissue distribution study disclosed that the lower limb bone took up about twice as much 111In-labeled PEG-phosSer-PAMAM as 111In-labeled nonphosphorylated PEG-Ser-PAMAM or unmodified PAMAM. An intrabone distribution experiment showed that fluorescein isothiocyanate (FITC)-labeled PEG-phosSer-PAMAM accumulated on the osteoid surfaces, which is associated with bone pathogenesis such as skeletal dysplasias and osteoporosis to a far greater extent than nonphosphorylated PEG-Ser-PAMAM. Our findings indicated that PEG-phosSer-PAMAM is a promising carrier for efficient drug targeting to osteoid surfaces.

A Computational Analysis of the Reaction of SO2 with Amino Acid Anions: Implications for Its Chemisorption in Biobased Ionic Liquids

We report a series of calculations to elucidate one possible mechanism of SO2 chemisorption in amino acid-based ionic liquids. Such systems have been successfully exploited as CO2 absorbents and, since SO2 is also a by-product of fossil fuels’ combustion, their ability in capturing SO2 has been assessed by recent experiments. This work is exclusively focused on evaluating the efficiency of the chemical trapping of SO2 by analyzing its reaction with the amino group of the amino acid. We have found that, overall, SO2 is less reactive than CO2, and that the specific amino acid side chain (either acid or basic) does not play a relevant role. We noticed that bimolecular absorption processes are quite unlikely to take place, a notable difference with CO2. The barriers along the reaction paths are found to be non-negligible, around 7–11 kcal/mol, and the thermodynamic of the reaction appears, from our models, unfavorable.

Analyzing how ions tend to form in the aqueous phase of the slurry and how they affect the bacterial oxidation of sulphide minerals

This paper describes the results of a study that relied on chemical and physico-chemical analysis techniques to examine the qualitative and quantitative composition of anions during bacterial oxidation of flotation concentrate. It was found that bacterial oxidation of flotation concentrate results in the production of anions of sulphate, thiosulphate, arsenate, selenate, nitrate, chloride and amino acids (cysteine, threonine and arginine). Anions of amino acids, as well as thiosulphate and selenate anions form chelates with precious metals, which get carried away with the biocake wash to the neutralization stage. The findings helped determine how the concentration of gold ions changes at different process stages. This research aims to analyze the behavior of anions during bacterial oxidation of sulphide minerals. The research material included samples of processed sulphide ores taken from active bacterial oxidation reactors at 12 different points (classifier overflow, flotation concentrate from the thickener, exit from reactors 1, 2, 3, 4, 5, 6; solids of counterflow wash-1 and wash-3, top of the sorption cyanidation tank, cyanidation tailings). The concentrations of amino acids were determined during sample analysis. Three amino acids were mainly detected in the solution: cysteine, threonine and arginine. These amino acids are capable of binding with gold ions and forming chelates. Under the effect of cyanides, cysteine and arginine were found to decompose while threonine remained intact.

Effects of Dicationic Imidazolium-Based Ionic Liquid Coatings on Oral Osseointegration of Titanium Implants: A Biocompatibility Study in Multiple Rat Demographics.

Dicationic imidazolium-based ionic liquids with amino acid anions, such as IonL-phenylalanine (IonL-Phe), have been proposed as a multifunctional coating for titanium (Ti) dental implants. However, there has been no evaluation of the biocompatibility of these Ti coatings in the oral environment. This study aims to evaluate the effects of IonL-Phe on early healing and osseointegration of Ti in multiple rat demographics. IonL-Phe-coated and uncoated Ti screws were implanted into four demographic groups of rats to represent biological variations that could affect healing: young males (YMs) and females (YFs), ovariectomized (OVXFs) females, and old males (OMs). Samples underwent histopathological and histomorphometric analysis to evaluate healing at 7 and 30 days around IonL-coated and uncoated Ti. The real-time quantitative polymerase chain reaction was also conducted at the 2- and 7-day YM groups to evaluate molecular dynamics of healing while the IonL-Phe was present on the surface. IonL-coated and uncoated implants demonstrated similar histological signs of healing, while coated samples’ differential gene expression of immunological and bone markers was compared with uncoated implants at 2 and 7 days in YMs. While YMs presented suitable osseointegration for both uncoated and IonL-Phe-coated groups, decreased success rate in other demographics resulted from lack of supporting bone in YFs and poor bone quality in OVXFs and OMs. Overall, it was found that IonL-coated samples had increased bone-to-implant contact across all demographic groups. IonL-Phe coating led to successful osseointegration across all animal demographics and presented the potential to prevent failures in scenarios known to be challenged by bacteria.

A Review of CO2 Capture by Poly(Ionic liquid)s

Abstract: Over the last two decades, poly(ionic liquid)s (PILs) have undergone extensive research and development. PILs have opened a whole new passage to versatile ionic polymers. It has compelled the chemical industry to rethink its modern ways of carbon capture. PILs have demonstrated excellent CO2 sorption capacities in comparison to their corresponding ionic liquids (ILs). The effects of the chemical structures of PILs on CO2 sorption, including the types of anion, cation, and backbone, have been discussed. This review aims to cover details of a large range of PILs along with their physical and structural properties, synthesis procedures, and the absorption power towards CO2. Imidazolium-based PILs are some of the strongest absorbents of CO2. On the other hand, PILs with amino acid (AA) anion seem to have a much-improved sorption capacity when compared PILs with the non-AA anionic part. PILs with hexafluorophosphate ion (PF6-) relatively absorb more CO2 compared to tetra-fluoroborate (BF4-) based PILs. The solubility of CO¬2 was increased with increasing pressure and decreased as temperature increased. The inclusion of hydroxyl groups in the polycation increased the interaction with CO2 molecules.¬ The COSMO-RS model was used to understand the molecular-level behavior of PILs in terms of their activity coefficients.

Construction and regulation of thermo-responsive vesicular solution in catanionic surfactant systems

<p indent="0mm">The aggregation behaviors in the binary systems of cationic Gemini surfactants with amide groups in hydrophobic chains (C₁₂A-C₂-AC₁₂) or spacer group (C₁₂-AC₂A-C₁₂) and anionic amino acid surfactant <italic>N</italic>-dodecanoylglutamic acid (C₁₂Glu) have been studied at two different pH values by adjusting the mixing ratio and temperature. The catanionic surfactant<bold> </bold>systems at pH 5.0 and 10.0 formed spherical micelles and vesicles at <sc>25 ℃</sc> by varying the mixing ratio, respectively. Upon increasing the temperature, the different temperature responsivenesses were realized in four vesicular solutions of catanionic surfactant systems. At pH 5.0 and 10.0, the vesicles formed in C₁₂A-C₂-AC₁₂&amp;C₁₂Glu system were stable and maintained a bluish hue, while the vesicles in C₁₂-AC₂A-C₁₂&amp;C₁₂Glu system tended to form the larger aggregates, accompanied by the change in solution from bluish to milky, or even precipitation with increasing temperature. Besides, the intermolecular hydrogen bonding of C₁₂Glu containing two carboxyl groups played an important role in vesicle formation and thermal stability. For C₁₂A-C₂-AC₁₂&amp;C₁₂Glu and C₁₂-AC₂A-C₁₂&amp;C₁₂Glu systems at pH 5.0, the hydrogen bonding of carboxyl groups in C₁₂Glu promoted the vesicle formation and thermal stability. In contrast, at pH 10.0, the carboxyl groups did not form hydrogen bonds and the vesicular solutions of C₁₂A-C₂-AC₁₂&amp;C₁₂Glu and C₁₂-AC₂A-C₁₂&amp;C₁₂Glu systems underwent dark blue or the transition from bluish to milky to precipitation, respectively. Moreover, these transition processes were thermally reversible. These thermo-responsive vesicular solutions can be elucidated on the basis of the temperature-induced variations in the strength of hydrogen bonds of the headgroups. The results suggested that the location of amide groups and hydrogen bonding between carboxyl groups could affect the formation and thermal stability of vesicular solutions.

Abstract P1-06-08: Metabolic diversity determines metastatic fitness of breast cancer brain-tropic cells

Abstract HER2+ breast cancer patients presenting with either synchronous (S-BM), latent residual (Lat) or metachronous (M-BM) brain metastases have poor survival outcomes. However, the basis for disparate metastatic fitness among disseminated tumor cells of similar oncotype within a distal organ remains unknown. Employing isogenic HER2+ breast cancer brain metastasis models, we show metabolic diversity and plasticity within brain-tropic cells determines metastatic fitness. Lactate secreted by aggressive metastatic cells (S-BM and M-BM) or lactate supplementation to mice bearing latent residual disease limits innate immune surveillance and triggers overt metastasis. Attenuating lactate metabolism in S-BM impedes metastasis, while M-BM adapt and survive as latent residual disease. In contrast to S-BM, Lat and M-BM survive in equilibrium with innate immune surveillance, oxidize glutamine and maintain cellular redox homeostasis through the anionic amino acid transporter xCT. Moreover, xCT expression is significantly higher in matched metachronous brain metastatic samples compared to primary tumors from HER2+ breast cancer patients. Genetic or pharmacological blockade of xCT eradicates residual disease and brain metastatic relapse in these preclinical models. Citation Format: Srinivas Malladi. Metabolic diversity determines metastatic fitness of breast cancer brain-tropic cells [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-06-08.