Browsing by Author "Billiot, Eugene"
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Item Characterization of green surfactants with Dicarboxylate Polar Head(2023-08) Fritz, Shayden; Billiot, Fereshteh; Xu, Wei; Billiot, Eugene; Olson, MarkThere has been a growing emphasis on developing biodegradable and environmentally friendly surfactants. One such relatively new class of surfactants that fall into this category are amino acid-based surfactants. This research focused on studying the physical properties (critical micelle concentration [CMC] and hydrodynamic radius) of aspartic and glutamic amino acid-based surfactants with two different types of hydrophobic tails (saturated hydrophobic chain with 13 carbons and an unsaturated hydrophobic tail containing 11 carbons). In addition to the varying types of hydrophobic tails and polar headgroups, this study also examined what effect different types of diamine counterions had on the physical properties examined. It is interesting to note that the type of diamine counterion or the amino acid head group, for the most part, had little effect on the physical properties examined. The major factor affecting significant changes in the physical properties was the type of hydrophobic tail. The CMC value obtained for saturated 13 carbon surfactants was significantly lower compared to the surfactant with an unsaturated hydrophobic tail containing 11 carbon chains. The range for the CMC values of saturated 13 carbon surfactant was 6 to 12 mM, while the range of the CMC values of unsaturated 11 carbon surfactant was found to have a value of 33 to 52 mM. The surfactant with the unsaturated 11 carbon chain had a significantly smaller hydrodynamic radius in comparison to the saturated 13 carbon surfactant. The range of the hydrodynamic radius for the unsaturated 11 carbon surfactant had a hydrodynamic range from 1 to 5 nm and the saturated 13 carbon surfactant was between 5 to 8 nm. However, there was one exception to this trend and that was the saturated 13 carbon glutamic surfactant in the presence of 1,2 diaminoethane counterion. It had a significantly larger size than all other surfactants measured. The hydrodynamic radius that was measured from saturated 13 carbon surfactant in the presence of 1,2 diaminoethane had a value of 106.47 nmItem Characterization of single amino acid based surfactants undecanoic L-Isoleucine and undecanoic L-Norleucine in the presence of diamine counterions with varying chain lengths(2019-08) Maynard-Benson, Amber; Billiot, Eugene; Billiot, Fereshteh; Causgrove, TimothyTo understand chiral recognition and discrimination, single amino-acid-based surfactants undecanoic L-isoleucine and L-norleucine were synthesized and examined at various pHs with different counterions. Analysis was conducted utilizing different analytical instruments and techniques such as NMR and Capillary Electrophoresis (CE). Knowledge gained from this research will later be used to develop a database that will recognize behaviors of micelle systems and determine which parameters and materials will be most effective for enantiomeric separation.1 The focus of this particular study was to determine how varying the chain length of diamine counterions affects the properties of the surfactant. The following six counterions were investigated: 1,2-ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, and sodium. Sodium was employed as the standard counterion for comparison. Early work was performed using arginine and lysine as counterions before shifting focus to the diamines; this data is also included as supplemental information. Data from this project has shown that the Critical Micelle Concentration (CMC) of surfactants is dependent upon the chain length of the diamine counterions. As the counterion chain length was increased, the CMC decreased. At pH 9 the CMC decreased from 12.19 mM undecanoic L-isoleucine with 1,2 ethylenediamine to a CMC of 2.00 mM for undecanoic Lisoleucine with 1,6 diaminohexane as the counterion. CE data showed that as the chain length of the counterion was increased, the enantiomers were resolved at a lower surfactant-counterion concentration. There was also improved chiral selectivity of BNA enantiomers in the presence of diamine counterions compared to the standard sodium. Based on previous literature, the micellar size also increased with a decrease in CMC as expected. The average hydrodynamic radius of undecanoic L-norleucine with 1,2-ethylenediamine at pH 10 was 9.17 Å compared to 24.52 Å for L-norleucine with 1,6 diaminohexane at pH 10.Item Characterization of the dipeptide based micellar systems undecanoic alanine-alanine and undecanoic alanine-glycine(2018-12) Maldonado, Savanna; Billiot, Fereshteh; Billiot, Eugene; Abdulla, HussainSurfactant are surface-active-agents, meaning surfactants have the ability to lower surface tension. In this research, two dipeptide surfactants undecanoic alanine-alanine and undecanoic alanine-glycine were studied to better understand their micellar systems. Variations of pH, temperature, surfactant concentration, and counterion type were examined to determine what effect, if any, changing these variables would have on micelle formation and chiral recognition. The counter ions examined in this study were di-amine alkanes with a different number of methyl groups separating the amines. These counter ions are pH dependent and preliminary results have shown that pH effects the interaction of these counter ions with the amino acid polar head, and in turn effects the physical properties of the surfactants and their micellar behavior. Some of the properties examined include: the critical micelle concentration, Krafft temperature, enantiomeric separation of chiral compounds, hydrodynamic radius of the micelles as well as fraction bound of the surfactant and counterions to the micelles. These systems were studied using proton Nuclear Magnetic Resonance (NMR), Diffusion Order Spectroscopy (DOSY), Capillary Electrophoresis (CE) and a LabQuest 2 with attached conductivity and temperature probes. The results here provide a better insight on the behavior of these dipeptide micellar systems which will aid in future research.Item Chiral recognition of binaphthyl derivatives with L-undecyl leucine surfactants in the presence of sodium and lysine counterions(Scientific Research Publishing, 2021-05-31) Billiot, Fereshteh; Garcia, Mauro; Risley, Amanda; Billiot, Eugene; Morris, KevinThis study investigates the effect of counterions on the chiral recognition of 1,1'-Binaphthyl-2,2'-diamine (BNA) and 1,1'-Binaphthyl-2,2'-diyl hydrogenphosphate (BNP) enantiomers when using an amino acid-based surfactant undecanoyl L-leucine (und-Leu) as the chiral pseudostationary phase in capillary electrophoresis. The effects of using two different counterions (sodium and lysine) on the chiral recognition of binaphthyl derivatives were compared at varying pH conditions. The enantiomeric separation of BNA and BNP enantiomers via capillary electrophoresis, using und-Leu as the chiral recognition medium, significantly improved the enantiomeric resolution in capillary electrophoresis at pH 7 when using Lysine counterions as compared to using sodium as the counterion. More specifically, at a surfactant concentration of 45 mM, at pH 7, a significant increase in chiral selectivity was observed when lysine was used as the counterion compared to sodium. The enantiomeric resolution of BNA and BNP increased by 6-fold and 1.1-fold, respectively, in capillary electrophoresis experiments when lysine was utilized as the counterion compared to using sodium. Furthermore, the retention factor of BNA and BNP enantiomers also increased approximately 3.5-fold and 4-fold, respectively, in the presence of lysine counterions as compared to using sodium counterions. When running buffer in capillary electrophoresis was increased to pH 11, the resolution and retention factors were nearly identical when comparing the effects of the sodium and lysine counterions. This signifies the important role of lysine’s positive net charge on chiral recognition. This study provides insight into the potential advantages of using cationic, pH-dependent counterions such as lysine to significantly improve the chiral recognition of binaphthyl derivatives when using chiral anionic surfactants as the pseudostationary phase in capillary electrophoresis.Item Chiral recognition of Dansyl Derivatives with an amino acid-based molecular micelle: A Molecular dynamics investigation(Scientific Research Publishing, 2021-05-26) Billiot, Fereshteh; Garcia, Mauro; Black, Nathan; Billiot, Eugene; Morris, Kevin F.; Fang, YayinIn this study, the chiral separation mechanisms of Dansyl amino acids, including Dansyl-Leucine (Dans-Leu), Dansyl-Norleucine (Dans-Nor), Dansyl-Tryptophan (Dans-Trp) and Dansyl-Phenylalanine (Dans-Phe) binding to poly-sodium N-undecanoyl-(L)-Leucylvalinate, poly (SULV), were investigated using molecular dynamics simulations. Micellar electrokinetic chromatography (MEKC) has previously shown that when separating the enantiomers of these aforementioned Dansyl amino acids, the L-enantiomers bind stronger to poly (SULV) than the D-enantiomers. This study aims to investigate the molecular interactions that govern chiral recognition in these systems using computational methods. This study reveals that the computationally- calculated binding free energy values for Dansyl enantiomers binding to poly (SULV) are in agreement with the enantiomeric order produced in experimental MEKC studies. The L-enantiomers of Dans-Leu, Dans-Nor, Dans-Trp, and Dans-Phe binding to their preferred binding pockets in poly (SULV) yielded binding free energy values of −21.8938, −22.1763, −21.3329 and −13.3349 kJ∙mol−1, respectively. The D-enantiomers of Dans-Leu, Dans-Nor, Dans-Trp, and Dans-Phe binding to their preferred binding pockets in poly (SULV) yielded binding free energy values of −14.5811, −15.9457, −13.6408, and −12.0959 kJ∙mol−1, respectively. Furthermore, hydrogen bonding analyses were used to investigate and elucidate the molecular interactions that govern chiral recognition in these molecular systems.Item A Comparison of first-year undergraduate and graduate international students' adjustment to college(2019-08) Oyeniyi, Odunola Funmilayo; Smith, Robert L.; Watson, Joshua C.; Nelson, Kristina; Billiot, EugeneInternational students constitute a growing student population in many colleges and universities in the United States. Adjusting to a new culture requires a new set of cultural patterns and behaviors that can be uncomfortable and sometimes stressful. Having a better understanding of how international students adjust to college in terms of resilience, relational skills, and acculturative stress, is important to university staff and the students alike, as it is the first step in improving the rate at which these students adjust to their new campus lives abroad. The purpose of this study was to investigate how resilience, relational skills, and acculturative stress, predict college adjustment of first-year undergraduate and graduate international students in the U.S. between August 2018 and May 2019. A combination of ninety-five undergraduate (n=40) and graduate (n=55) first-year international students participated in this study. The data was collected during the spring semester of 2019 from two universities in South Texas utilizing the Brief Resilience Scale (Smith et al., 2008), the Relational Skills Inventory (Smith, 2019), the Acculturative Stress Scale for International Students (Sandhu & Asrabadi, 1994, 1998), and the Inventory of New College Student Adjustment (Watson & Lenz, 2018). Descriptive statistics and MANOVA were used to analyze the variables in this study and a standard multiple regression was employed to determine the unique contributions of resilience, relational skills, and acculturative stress on college adjustment. Additionally, Fisher’s z transformation was used to evaluate whether two regression models were significantly different. The results indicated a statistically significant difference between first-year undergraduate and graduate international students as related to college adjustment. Further analysis discovered significant relationships among predictor and criterion variables. Resilience, relational skills, and acculturative stress significantly explained 55% of the variance in the adjustment of these international students. The comparison of these 3 factors to each other revealed no statistically significant differences, which indicates there are no distinctions in model fit between undergraduate and graduate students. The results of this study have practical implications for college educators, counselors, and administrators which may help universities meet the needs of first-year international students.Item Development and verification of a computational model for the prediction of critical micelle concentrations (CMCs) for monoanionic amino acid-based surfactants(2023-08) Black, Nathan D.; Billiot, Eugene; Billiot, Fereshteh; Olson, MarkIn this research, the critical micelle concentrations (CMCs) of nine novel monoanionic amino acid-based surfactants (AABSs) were experimentally determined and used to validate a CMC prediction model based upon molecular dynamics (MD) simulations. The AABSs were synthesized, purified, and had their CMCs determined via the electrical conductivity method. After parametrizing the AABSs with a hybrid gaff2/ff14SB force field, MD simulations were performed in which they were solvated with various explicit and implicit solvents at concentrations ranging from 0.1 – 100 mM. This produced several parameters which are believed to be representative of the thermodynamics of AABS solutions. A battery of polynomial regression and statistical uncertainty analyses were performed on the concentration-dependent values of each parameter for the AABSs. It was found that using the implicit solvent model IGB8 results in distinct measurement uncertainties before and after specific concentrations that strongly agreed with the experimental CMCs. Utilizing an algorithm based upon the t-test in which these values were identified, the total potential and van der Waal energies were found to be the best predictors of AABS CMCs. This was supplemented by a quantitative structure-property relationship (QSPR) study in which ionization potentials and van der Waal energies were identified as strong predictors for experimental CMCs. It was jointly concluded from the results of MD simulation analysis and QSPR regressions that electrostatic energies restrict the CMCs of this family of AABSs to a particular order of magnitude, while the van der Waal energies distinguish each AABs from one another. This research represents the first documented (and successful) attempt to theoretically predict CMCs for AABSs, as well as a pioneering unification between MD simulation- and QSPR-based theoretical studies.Item Development of bis-bipyridinium and anthracene carboxyimide-based stimuli-responsive soft matter(2023-08) Jakharia, Vandan Paresh; Olson, Mark; Billiot, Fereshteh; Billiot, EugeneThis thesis focuses on the design and synthesis of an array of novel amphiphilic and polymeric molecules as precursors for developing dynamic stimuli-responsive supramolecular materials by harnessing the competency of non-covalent interactions. Over the past decades, bipyridinium-based derivatives have gained tremendous attention due to their applicability as functional units in tunable supramolecular complexes. The innate propensity of functionalized bipyridinium salts to serve as a ?-electron deficient acceptor allows them to undergo ?-? stacking donor-acceptor CT interactions in the presence of ?-electron rich organic molecules. This characteristic feature was employed to develop novel bipyridinium-functionalized amphiphiles and bio-polymeric materials that are capable of engaging in molecular recognition with and facilitating the extraction of melatonin, a neurotransmitter from water. The first project reports the design and development of heptyl and glycol-bridged bis-bipyridinium-based gemini amphiphiles that can undergo template-directed self-assembly. Previous studies indicated that the electrophilic aromatic nature of tetra-cationic bis-bipyridinium gemini amphiphiles can be exploited to form ?-? stacking charge-transfer interactions with ?-electron rich molecules. Thus, in an effort to establish structure-property relationships and understand the effect of the bridging unit, varied bridged bis-bipyridinium gemini amphiphiles were synthesized. They were investigated for their use of melatonin as a template for directed self-assembly processes. The charge-transfer interactions between the units lead to absorption band formation in the visible region of the electromagnetic radiation that can be exploited for various material applications. Upon comparing, the two derivatives in detail, their micellization behavior, surface properties, thermodynamic parameters, UV-Vis absorption, and micellar size exhibited similar characteristics. However, the heptyl-bridged gemini amphiphile responded to templation much more strongly, while the glycol-bridged gemini amphiphile exhibited higher solubility, they both portrayed excellent amphiphile and surface-active characteristics. The second part of this work focuses on employing ?-electron deficient bipyridinium units to design and process functional lipoic ester-based polymeric materials for the indole-base molecular targets from water. A series of lipoic-ester based-bipyridinium functionalized polymers with varying alkyl tail lengths were developed and studied to determine structure-property correlations and analyze their material characteristics. Out of the eight-novel functionalized polymeric materials, bipyridinium-bridged lipoic ester polymer (BLEP) formed polymeric sheets while nonyl-bipyridinium-functionalized lipoic ester polymer (9C-BFLEP) formed coacervates in water. Both materials showed comparable and acceptable efficiency in adsorbing melatonin out of solution by harnessing ?-? stacking charge-transfer interactions in conjugation with the hydrophobic effect. This approach provided a quick and promising method for the remediation of indole-cored molecules from water. Lastly, an anthracene carboxyimide derivative was synthesized with the ability to undergo a photo-induced [4+4] cycloaddition dimerization process. The dimerization can easily be reversed upon heating. The compound was found to be able to have a special feature that allows them to undergo single crystal-to-single crystal photo-dimerization upon exposure to UV light. This controlled switchable characteristic property of anthracene carboxyimide are unique and can be utilized for developing tunable molecular switches with applications where stimuli-responsive materials are required.Item Experimental-computational investigation of chiral separations with amino acid-based surfactants(2021-05) Garcia, Mauro; Billiot, Eugene; Billiot, Fereshteh; Causgrove, TimothyThis thesis research investigates the use of amino acid-based micelles to separate enantiomeric compounds. These are investigated using both, experimental and computational methods. The experimental portion of my thesis research investigates the effect of counterions on the chiral recognition of 1,1′-Binaphthyl-2,2′-diamine (BNA) and 1,1′-Binaphthyl-2,2′-diyl hydrogen phosphate (BNP) enantiomers when using an amino acid-based surfactant as the chiral pseudo stationary phase in capillary electrophoresis. The effects of sodium counterions on the chiral recognition of binaphthyl derivatives were compared to that of using pH-dependent Lysine counterions at varying pH conditions. The enantiomeric separation of BNP and BNA enantiomers via capillary electrophoresis, using L-Undecyl-Leucine (und-Leu) as the chiral recognition medium, significantly improved the enantiomeric resolution in capillary electrophoresis at pH 7 when using Lysine counterions as compared to using sodium counterions. Therefore, this experimental project provides insight into the advantages of using cationic, pH-dependent counterions such as Lysine to significantly improve the chiral recognition of binaphthyl derivatives in capillary electrophoresis studies. The computational portion of my thesis research focused on developing computational methodology to study the binding interactions between amino acid-based molecular micelles and chiral enantiomers. The computational method development plays a crucial role in helping the research advance towards the development of a predictive database. After developing a set of protocols for the computational research, the methods were then used to study the chiral separation mechanisms of Dansyl amino acids, including Dansyl-Leucine, Dansyl-Norleucine, Dansyl- Tryptophan and Dansyl-Phenylalanine binding to poly-sodium N-undecanoyl-(L)-Leucylvalinate, poly(SULV). This study reveals that the computationally-calculated binding free energy values for Dansyl enantiomers binding to poly(SULV) are in agreement with the enantiomeric order produced in experimental MEKC studies. Furthermore, hydrogen bonding analyses was used to investigate and elucidate the molecular interactions that govern chiral recognition in these molecular systems.Item The influence of diamine counterion use and surfactant counterion ratio on chiral selectivity of amino acid-based surfactants(2022-04) Montoya, Sara; Black, Nathan; Billiot, Eugene; Billiot, Fereshteh; Morris, KevinIn this study, the effects of counterion type and surfactant-to-counterion ratio on the chiral selectivity of several binaphthyl derivatives with L,L- undecanoyl leucine-valinate was examined by use of Micellar Electrokinetic Chromatography (MEKC). The chiral separations of 1, 1−𝑏𝑖−2−𝑛𝑎𝑝ℎ𝑡ℎ𝑦𝑙−2, 2−𝑑𝑖𝑦𝑙ℎ𝑦𝑑𝑟𝑜𝑔𝑒𝑛(𝐵𝑁 𝑃 )1, 1′−𝑏𝑖−2−𝑛𝑎𝑝ℎ𝑡ℎ𝑦𝑙−2, 2′−𝑑𝑖𝑎𝑚𝑖𝑛𝑒(𝐵𝑁𝐴)𝑎𝑛𝑑1, 1′−𝑏𝑖−2−𝑛𝑎𝑝ℎ𝑡ℎ𝑜𝑙(𝐵𝑂𝐻 by the dipeptide surfactant varied widely in the presence of three counterions, 1,2 diaminoethyl, 1,2 diamino- propyl, and 1,3 diaminopropyl and with surfactant-to-counterion ratios of 1-to-1 and 1-to-0.5. The results of this study have shown that the selection of 1,2 diaminoethyl in a 1-to-1 surfactant-counterion-ratio provides enhanced baseline separation for enantiomers of BOH in comparison to its 1-to-0.5 counterpart, though no significant difference in separation can be observed for enantiomers of BNP under the same conditions. Despite the observation that every one of the three included counterions engendered some degree of separation for each analyte, enantiomers of BNP exhibited heightened separation in the presence of 1,2 diaminoethyl and 1,2 diaminopropyl at a pH level of 8. Conversely, the comparative Na counterion separates enantiomers of BOH and BNA significantly better than the counterions examined.Item Navigating becoming: Latina leaders speak out(2023-5) Esparza, Cristina Lorena; Maxwell, Gerri; Elliff, D. Scott; Cervantes, Bernadine; Billiot, EugeneThe purpose of this qualitative, narrative study is to give voice to Latinas in leadership. In the last few decades, there have been more women making their entrance into the educational administrative field, but minority females continue to evidence smaller amounts of participation. Although a few studies have reported the number of Latinas in administrative positions, the study of their administrative experiences is limited. Given an ever-emerging diverse student population, developing Latina leaders is urgent. Research advocates that Latinas offer opportunities to best serve minority students due to their personal and professional characteristics, culture, and experiences. Although the Latino(a) population continues to grow in the United States, Latino(a) leaders are underrepresented, and so are their recruitment, development, and retention needs in the literature. Thus, this topic is vital for education research, education policy, and educational leadership practice. The five primary themes resulting from the testimonios of these leaders included their perspectives on how their identities shaped them as leaders as well as how the various barriers they encountered not only challenged them but made them stronger leaders. Additionally, these participants shared how their cultural expectations informed them as leaders. When opportunities presented themselves, these Latinas stepped up to those challenges seeing them as opportunities. Finally, the participants shared how their resiliency was a culmination of their life and leadership experiences, both being noteworthy to the impact they shared as leaders. The study concludes with recommendations for aspiring Latina leaders.Item Synthesis of aspartic acid-based bifurcated tripeptide surfactants(2023-08-29) Swonke, Roslyn; Garcia, Angelina; Billiot, Eugene; Billiot, Fereshteh; Olson, Mark; Azad, ChandraAmino acid-based surfactants (AABS) are amphipathic molecules composed of an amino acid-based polar headgroup and nonpolar hydrocarbon chain. Surfactants, the truncated name for surface-active agents, are molecules that decrease surface tension. It is this property, along with their amphipathic structure, that imbues surfactants with useful properties, such as encapsulating other compounds and emulsifying insoluble phases. AABS are of particular interest, as they incorporate amino acids, which are the building blocks of life. The incorporation of amino acids as the polar headgroup thus improves bioavailability and biodegradability, thereby increasing the applications of this subset of surfactants. The objective of this study is to synthesize and characterize a group of novel tripeptide bifurcated AABS with aspartic acid as the central amino acid at the polar headgroup.