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University of Massachusetts Amherst

2021

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Articles 1 - 18 of 18

Full-Text Articles in Chemistry

Antibiotic Sensitivity Testing Of Foodborne Bacteria Using Surface-Enhanced Raman Spectroscopy, Joshua Gukowsky Oct 2021

Antibiotic Sensitivity Testing Of Foodborne Bacteria Using Surface-Enhanced Raman Spectroscopy, Joshua Gukowsky

Doctoral Dissertations

The spread of antibiotic resistant bacteria around the world has become a major public health issue, and it is essential that effective detection methods exist for identifying these organisms and preventing them from spreading throughout our food systems and into the environment. The goal of this research is to develop a novel analytical procedure that is capable of easily identifying antibiotic resistance in bacterial samples, and also provides more information about the biochemical characteristics of the bacteria and their responses to antibiotic exposure. Surface-enhanced Raman Spectroscopy (SERS), an analytical technique that uses light scattering to produce a spectrum based on …


Computational Approaches For The Multimodal Imaging Of Nanomaterials And Their Biochemical Effects, Laura J. Castellanos Oct 2021

Computational Approaches For The Multimodal Imaging Of Nanomaterials And Their Biochemical Effects, Laura J. Castellanos

Doctoral Dissertations

Nanomaterial delivery systems constitute a group of drug delivery vehicles that have been used extensively in biodelivery. The proper characterization of the therapeutic function of these nanomaterials requires analytical methods to track the presence of the cargo and its biochemical effects. In some cases, the detection of the cargo and biochemical changes are not attainable in the same experiment, and more than one technique might be needed for the proper analysis of the drug delivery system. In this case, separate analysis of adjacent tissue sections is performed by techniques that offer complementary information such as MALDI-MS and LA-ICP-MS. However, the …


Advanced Materials Design Using Application-Based Processing Techniques, Daniel S. Camarda Oct 2021

Advanced Materials Design Using Application-Based Processing Techniques, Daniel S. Camarda

Doctoral Dissertations

This dissertation pertains to generating advanced materials using application-based processing techniques. First, billets consisting of PTFE sintering powders are evaluated using Thermomechancal Analysis. It was found that both shape change and volume change are associated with enthalpic and entropic recoil, respectively. These phenomena, due to melting and stored energy during the powder compaction process, were found to be molecular weight dependent. Additionally, kinetics of the recovery and sintering process were found to be slower in blended specimens than pure samples. Next, the creation of graft copolymers by selectively grafting a second polymer to the amorphous fraction of a semi-crystalline polymer …


Amyloidogenesis Of Β-2-Microglobulin Studied By Mass Spectrometry And Covalent Labeling, Blaise G. Arden Oct 2021

Amyloidogenesis Of Β-2-Microglobulin Studied By Mass Spectrometry And Covalent Labeling, Blaise G. Arden

Doctoral Dissertations

Amyloid-forming proteins are implicated in a number of debilitating diseases. While many amyloid-forming proteins are well studied, the early stages of amyloidosis are still not well understood on a molecular level. Covalent labeling, combined with mass spectrometry (CL-MS), is uniquely well suited to provide molecular-level insight into the factors governing the early stages of amyloidosis. This dissertation leverages CL-MS techniques to examine the early stages of β-2-microglobulin (β2m) amyloidosis. β2m is the protein that forms amyloids in the condition known as dialysis-related amyloidosis. An automated CL-MS technique that uses dimethyl(2-hydroxy-5-nitrobenzyl) sulfonium bromide as a labeling reagent was developed and used …


Behavioral Modulation Of Supramolecular Assemblies Via Covalent And Non-Covalent Interfacial Transformations, Ann Fernandez Sep 2021

Behavioral Modulation Of Supramolecular Assemblies Via Covalent And Non-Covalent Interfacial Transformations, Ann Fernandez

Doctoral Dissertations

There are several molecular level mechanisms at the origin of biological functions that serve as inspiration for the development of the “next generation” of materials that display adaptive and interactive properties. However, it will take time for synthetic materials to approach the level of complexity, robustness, and adaptability of biological systems. Although there are switchable platforms that respond via sensitized molecular components, there are currently no examples of materials that truly possess the type of autonomous behavior seen in biological systems. Even though these concepts are common in living organisms, their translation into a synthetic platform remains challenging to this …


Manipulating The Aliovalent Magnetic Dopants In Ti(Iv)-Based Oxide Nanocrystals, Muhammad Abdullah Sep 2021

Manipulating The Aliovalent Magnetic Dopants In Ti(Iv)-Based Oxide Nanocrystals, Muhammad Abdullah

Doctoral Dissertations

The intentional incorporation of impurities or dopants in semiconductors is fundamental to manipulate the properties that render them useful for spintronics, photocatalysis, and optoelectronics. One long-standing challenge in integrating the doped semiconductors in various applications is the design of materials with controlled individual dopant properties such as dopants speciation, valence state, and spin dynamics. Despite several elegant studies to circumvent these material challenges, the quest for new materials with tunable dopant properties to address the theoretical and experimental understanding continues. In this work, we combine synthetic chemistry and various spectroscopies to study a class of materials possessing both substitutional magnetic …


Design Of Resposive Oligomeric And Polymeric Interfaces For Sensing And Controlled Release Applications, . Manisha Sep 2021

Design Of Resposive Oligomeric And Polymeric Interfaces For Sensing And Controlled Release Applications, . Manisha

Doctoral Dissertations

Nature has designed magnificent responsive systems by constructing several interacting molecular level networks for the recognition and propagation of chemical and biochemical information. One of the eminent characteristics of these systems is their capability to quickly transduce molecular scale recognition events into macroscopic or visually observable responses. Inspired by these systems present in nature, we became interested in developing artificial responsive systems with similar capabilities. This dissertation will feature four such systems that employ amphiphilic oligomers and polymers which were chosen as the scaffolds because of their high thermodynamic stability, low critical aggregation concentrations, convenient handles to incorporate functional group …


Designing Stimuli-Responsive Nanocomposites To Investigate Interface Dynamics, Huyen Vu Jul 2021

Designing Stimuli-Responsive Nanocomposites To Investigate Interface Dynamics, Huyen Vu

Doctoral Dissertations

Inspired by nature, this research focuses on designing multifunctional renewable nanocomposites with high toughness and stimuli-responsiveness. In recent years, cellulose nanocrystals (CNCs) have been explored due to their abundance, renewable resource, and unique mechanical strength and structural coloration. CNCs naturally self-assemble into the helicoidal (Bouligand) structure that effectively endure high impacts but is brittle without an attendant soft phase. A thermoresponsive polymer, poly(diethylene glycol methyl ether methacrylate) (PMEO2MA), was incorporated into CNCs via evaporation-induced self-assembly to improve toughness of the resulting nanocomposites and to study responses in polymer dynamics under varying temperature and humidity conditions. To study microscopic …


Thermoelectric Transport In Disordered Organic And Inorganic Semiconductors, Meenakshi Upadhyaya Jul 2021

Thermoelectric Transport In Disordered Organic And Inorganic Semiconductors, Meenakshi Upadhyaya

Doctoral Dissertations

The need for alternative energy sources has led to extensive research on optimizing the conversion efficiency of thermoelectric (TE) materials. TE efficiency is governed by figure-of-merit (ZT) and it has been an enormously challenging task to increase ZT > 1 despite decades of research due to the interdependence of material properties. Most doped inorganic semiconductors have a high electrical conductivity and moderate Seebeck coefficient, but ZT is still limited by their high lattice thermal conductivity. One approach to address this problem is to decrease thermal conductivity by means of alloying and nanostructuring, another is to consider materials with an inherently low …


Enhancing The Intracellular Availability Of Protein Cargoes In Polymer-Mediated Delivery, Christopher R. Hango Jun 2021

Enhancing The Intracellular Availability Of Protein Cargoes In Polymer-Mediated Delivery, Christopher R. Hango

Doctoral Dissertations

Protein drugs, including antibodies, are rapidly emerging as the top-selling pharmaceuticals worldwide owing to their unparalleled specificity and biocompatibility. However, none of the currently-approved protein therapeutics act intracellularly, despite the vast majority of potential drug targets residing within the cell. This is due mainly to the paramount challenge of transporting hydrophilic macromolecular cargoes across the plasma membrane. As such, effective protein carriers are essential for the advancement of modern medicine. Despite significant advances, many challenges still plague protein delivery. Following membrane transduction, delivery vectors must preserve the structure and activity of their cargoes while transporting them to the correct subcellular …


Investigative Mechanisms To Exploit Caspase-Induced Apoptosis Using Polymeric Nanogels, Francesca Edith Anson May 2021

Investigative Mechanisms To Exploit Caspase-Induced Apoptosis Using Polymeric Nanogels, Francesca Edith Anson

Doctoral Dissertations

Cysteine aspartate proteases (caspases) act as the molecular scissors of cell death, disintegrating diverse cellular components necessary for survival and growth via proteolysis. Caspases are tightly regulated through a myriad of mechanisms including proteolytic processing, structural changes, post-translational modifications and metal binding. Correspondingly, cancers have evolved numerous resistance and desensitization mechanisms upstream or within the caspase pathway to avoid death signals. These mechanisms are extremely diverse and are not fully understood however, the field overwhelming suggests caspase activity and caspase inhibition antagonism to be critical for efficacious cancer therapies. Accordingly, exploiting the role of caspases in apoptosis has become an …


Electrospinning Fibers Via Complex Coacervation, Xiangxi Meng Apr 2021

Electrospinning Fibers Via Complex Coacervation, Xiangxi Meng

Doctoral Dissertations

Electrospun fibers are high-surface-area materials widely used in applications ranging from batteries to wound dressings. Typically, an electrospinning precursor solution is prepared by dissolving a high-molecular-weight polymer in an organic solvent to form a sufficiently entangled solution. Our approach bypasses the requirement for entanglements and completely avoids toxic chemicals by focusing on using an aqueous complex coacervates solution. Coacervates are a dense, polymer-rich liquid phase resulting from the associative electrostatic complexation of oppositely charged macroions. We were the first to demonstrate that liquid complex coacervates could be successfully electrospun into polyelectrolyte complex (PEC) fibers. A canonical coacervate system was formed …


Evidence For The Role Of Cyp51a And Xenobiotic Detoxification In Differential Sensitivity To Azole Fungicides In Boxwood Blight Pathogens, Stefanos Stravoravdis, Robert E. Marra, Nicholas R. Leblanc, Joanne Crouch, Jonathan P. Hulvey Jan 2021

Evidence For The Role Of Cyp51a And Xenobiotic Detoxification In Differential Sensitivity To Azole Fungicides In Boxwood Blight Pathogens, Stefanos Stravoravdis, Robert E. Marra, Nicholas R. Leblanc, Joanne Crouch, Jonathan P. Hulvey

Microbiology Department Faculty Publication Series

Boxwood blight, a fungal disease of ornamental plants (Buxus spp.), is caused by two sister species, Calonectria pseudonaviculata (Cps) and C. henricotiae (Che). Compared to Cps, Che is documented to display reduced sensitivity to fungicides, including the azole class of antifungals, which block synthesis of a key fungal membrane component, ergosterol. A previous study reported an ergosterol biosynthesis gene in Cps, CYP51A, to be a pseudogene, and RNA-Seq data confirm that a functional CYP51A is expressed only in Che. The lack of additional ergosterol biosynthesis genes showing significant differential expression suggests that the functional CYP51A in Che could contribute to …


Raising Dielectric Permittivity Mitigates Dopant-Induced Disorder In Conjugated Polymers, Meenakshi Upadhyaya, Michael Lu-Díaz, Subhayan Samanta, Muhammad Abdullah, Keith Dusoe, Kevin R. Kittilstved, Dhandapani Venkataraman, Zlatan Akšamija Jan 2021

Raising Dielectric Permittivity Mitigates Dopant-Induced Disorder In Conjugated Polymers, Meenakshi Upadhyaya, Michael Lu-Díaz, Subhayan Samanta, Muhammad Abdullah, Keith Dusoe, Kevin R. Kittilstved, Dhandapani Venkataraman, Zlatan Akšamija

Electrical and Computer Engineering Faculty Publication Series

Conjugated polymers need to be doped to increase charge carrier density and reach the electrical conductivity necessary for electronic and energy applications. While doping increases carrier density, Coulomb interactions between the dopant molecules and the localized carriers are poorly screened, causing broadening and a heavy tail in the electronic density-of-states (DOS). The authors examine the effects of dopant-induced disorder on two complimentary charge transport properties of semiconducting polymers, the Seebeck coefficient and electrical conductivity, and demonstrate a way to mitigate them. Their simulations, based on a modified Gaussian disorder model with Miller-Abrahams hopping rates, show that dopant-induced broadening of the …


Effective And Selective Dna Modification On Bacterial Membranes, Qian Tian, Yousef Bagheri, Puspam Keshri, Rigumula Wu, Kewei Ren, Qikun Yu, Mingxu You Jan 2021

Effective And Selective Dna Modification On Bacterial Membranes, Qian Tian, Yousef Bagheri, Puspam Keshri, Rigumula Wu, Kewei Ren, Qikun Yu, Mingxu You

Chemistry Department Faculty Publication Series

With highly precise self-assembly and programmability, DNA has been widely used as a versatile material in nanotechnology and synthetic biology. Recently, DNA-based nanostructures and devices have been engineered onto eukaryotic cell membranes for various exciting applications in the detection and regulation of cell functions. While in contrast, the potential of applying DNA nanotechnology for bacterial membrane studies is still largely underexplored, which is mainly due to the lack of tools to modify DNA on bacterial membranes. Herein, using lipid-DNA conjugates, we have developed a simple, fast, and highly efficient system to engineer bacterial membranes with designer DNA molecules. We have …


Polymeric Nanoparticles Active Against Dual-Species Bacterial Biofilms, Jessa Marie V. Makabenta, Jungmi Park, Cheng-Hsuan Li, Aritra Nath Chattopadhyay, Ahmed Nabawy, Ryan F. Landis, Akash Gupta, Suzannah Schmidt-Malan, Robin Patel, Vincent M. Rotello Jan 2021

Polymeric Nanoparticles Active Against Dual-Species Bacterial Biofilms, Jessa Marie V. Makabenta, Jungmi Park, Cheng-Hsuan Li, Aritra Nath Chattopadhyay, Ahmed Nabawy, Ryan F. Landis, Akash Gupta, Suzannah Schmidt-Malan, Robin Patel, Vincent M. Rotello

Chemistry Department Faculty Publication Series

Biofilm infections are a global public health threat, necessitating new treatment strategies. Biofilm formation also contributes to the development and spread of multidrug-resistant (MDR) bacterial strains. Biofilm-associated chronic infections typically involve colonization by more than one bacterial species. The co-existence of multiple species of bacteria in biofilms exacerbates therapeutic challenges and can render traditional antibiotics ineffective. Polymeric nanoparticles offer alternative antimicrobial approaches to antibiotics, owing to their tunable physico-chemical properties. Here, we report the efficacy of poly(oxanorborneneimide) (PONI)-based antimicrobial polymeric nanoparticles (PNPs) against multi-species bacterial biofilms. PNPs showed good dual-species biofilm penetration profiles as confirmed by confocal laser scanning microscopy. …


Exogenous Introduction Of Initiator And Executioner Caspases Results In Different Apoptotic Outcomes, Francesca Anson, S Thayumanavan, Jeanne A. Hardy Jan 2021

Exogenous Introduction Of Initiator And Executioner Caspases Results In Different Apoptotic Outcomes, Francesca Anson, S Thayumanavan, Jeanne A. Hardy

Chemistry Department Faculty Publication Series

The balance of pro-apoptotic and pro-survival proteins defines a cell's fate. These processes are controlled through an interdependent and finely tuned protein network that enables survival or leads to apoptotic cell death. The caspase family of proteases is central to this apoptotic network, with initiator and executioner caspases, and their interaction partners, regulating and executing apoptosis. In this work, we interrogate and modulate this network by exogenously introducing specific initiator or executioner caspase proteins. Each caspase is exogenously introduced using redox-responsive polymeric nanogels. Although caspase-3 might be expected to be the most effective due to the centrality of its role …


A Synergistic Anti-Diabetic Effect By Ginsenosides Rb1 And Rg3 Through Adipogenic And Insulin Signaling Pathways In 3t3-L1 Cells, Hee-Do Hong, Sun-Il Choi, Ok-Hwan Lee, Young-Cheul Kim Jan 2021

A Synergistic Anti-Diabetic Effect By Ginsenosides Rb1 And Rg3 Through Adipogenic And Insulin Signaling Pathways In 3t3-L1 Cells, Hee-Do Hong, Sun-Il Choi, Ok-Hwan Lee, Young-Cheul Kim

Nutrition Department Faculty Publication Series

Although ginsenosides Rb1 and Rg3 have been identified as the significant ginsenosides found in red ginseng that confer anti-diabetic actions, it is unclear whether insulin-sensitizing effects are mediated by the individual compounds or by their combination. To determine the effect of ginsenosides Rb1 and Rg3 on adipocyte differentiation, 3T3-L1 preadipocytes were induced to differentiate the standard hormonal inducers in the absence or presence of ginsenosides Rb1 or Rg3. Additionally, we determined the effects of Rb1, Rg3, or their combination on the expression of genes related to adipocyte differentiation, adipogenic transcription factors, and the insulin signaling pathway in 3T3-L1 cells using …