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Title: MECHANISTIC STUDIES OF THE PLP-DEPENDENT ENZYME, METHIONINE GAMMA-LYASE AND THE HEME-DEPENDENT ENZYME, INDOLEAMINE 2,3-DIOXYGENASE.
Creator: Foo, Timothy, Terentis, Andrew C., Florida Atlantic University, Department of Chemistry and Biochemistry, Charles E. Schmidt College of Science
Abstract/Description: Methionine-γ-lyase (MGL) is a pyridoxal-5′-phosphate (PLP) dependent enzyme found in bacteria and protozoa that catalyzes a variety of reactions, including the γ-elimination of L-methionine (L-Met). Besides its physiological roles in organisms, MGL is also a therapeutic target for pathogenic diseases and cancer. Since MGL’s catalytic mechanism remains uncertain, a new spectrophotometric assay was validated for measuring the kinetics of MGL catalyzed reactions. Kinetic data and density...
Show moreMethionine-γ-lyase (MGL) is a pyridoxal-5′-phosphate (PLP) dependent enzyme found in bacteria and protozoa that catalyzes a variety of reactions, including the γ-elimination of L-methionine (L-Met). Besides its physiological roles in organisms, MGL is also a therapeutic target for pathogenic diseases and cancer. Since MGL’s catalytic mechanism remains uncertain, a new spectrophotometric assay was validated for measuring the kinetics of MGL catalyzed reactions. Kinetic data and density functional theory (DFT) data for the γ-elimination reaction of L-Met and several other substrate analogues by MGL from P. gingivalis is reported. A direct correlation between experimental kcat values and DFT-calculated activation energies of the γ-cleavage reaction of the enamine intermediate was identified for various substrates. Considering these data, we propose a catalytic mechanism for MGL catalysis, whereby the γ-cleavage step is rate-limiting. This conclusion has direct implications for the rational design of substrates or inhibitors aimed at regulating MGL activity. PLP-dependent enzymes are present in all organisms and account for ~4% of all discovered enzyme activities. They all possess a common external aldimine and quinonoid intermediate at the start of their reaction pathway but likely diverge thereafter into different reaction pathways based on their substrate(s) and active site environment. To yield insight into the divergent reactivity of the quinonoid intermediate, DFT calculations of several PLP-dependent enzymes with unique reactivity revealed that the charge distribution is modulated on Cα and C4’, which allows for the regioselectivity of the quinonoid intermediate. The mammalian heme enzyme indoleamine 2,3-dioxygenase-1 (IDO1) catalyzes the first reaction of L-tryptophan (L-Trp) oxidation along the kynurenine pathway. IDO1 is a central immunoregulatory enzyme with important implications for inflammation, infectious disease, autoimmune disorders, and cancer. Since IDO1’s catalytic mechanism remains uncertain, kinetic data and DFT data for the dioxygenation reaction of L-Trp and several other substrate analogues by human IDO1 is reported. A direct correlation between experimental kcat values and DFT-calculated activation energies of the C2-O cleavage reaction of the L-Trp-epoxide intermediate was identified for various substrates. This conclusion has direct implications for the rational design of substrates or inhibitors aimed at regulating IDO1 activity and yields insight into heme-dependent dioxygenation chemistry.
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Date Issued: 2021
PURL: http://purl.flvc.org/fau/fd/FA00013870
Subject Headings: Lyases, Enzymes
Format: Document (PDF)

Title: Metalloprotease Profiling in Melanoma.
Creator: Giricz, Orsolya, Florida Atlantic University, Fields, Gregg B., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: The proteolytic activities of the ADAM (a disintegrin and metalloproteinase), ADAMTS (a disintegrin and metalloproteinases with thrombospondin motifs) and MMP (matrix metalloproteinase) protein families play important roles in normal and multiple pathological conditions. These metalloproteases have potential implications in the degradation of the extracellular matrix and in the processing of bioactive molecules. Under pathological conditions these proteases are involved in many diverse...
Show moreThe proteolytic activities of the ADAM (a disintegrin and metalloproteinase), ADAMTS (a disintegrin and metalloproteinases with thrombospondin motifs) and MMP (matrix metalloproteinase) protein families play important roles in normal and multiple pathological conditions. These metalloproteases have potential implications in the degradation of the extracellular matrix and in the processing of bioactive molecules. Under pathological conditions these proteases are involved in many diverse processes from tumor cell migration to cartilage destruction in rheumatoid arthritis. In the present study, the gene expression levels of six ADAMs, eight MMPs, and four ADAMTSs were analyzed by Real Time PCR. RNA was isolated from multiple normal fibroblast and metastatic melanoma cell lines, as well as the isogenic normal tissue and tumor samples. This method allowed for detected changes in mRNA expressiOn of the individual metalloproteainase genes to be compared between normal and metastatic states, and also between tissue and cultured cells. Substantial differences have been observed in the level of ADAM and MMP mRNA expression between tissue and cell lines. In general, the level of expression is several folds higher in cultured cells compared to the isogenic tissue they are derived from. Protein microarrays were utilized in order to evaluate the correlations between MMP and TIMP mRNA copy numbers and protein abundance in cell culture. In several cases, distinct differences were observed regarding the localization of the proteins examined. In order to determine if the metalloprotease genes that were elevated at the level of RNA expression produce functional proteins, the foundations of an in situ FRET assay have been established. This will greatly aid in a better understanding of the behavior of metallopeptidases in a cellular context.
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Date Issued: 2008
PURL: http://purl.flvc.org/fau/fd/FA00000859
Subject Headings: Tumor markers--Research, Metalloproteinases--Inhibitors, Melanoma--Research, Proteins--Synthesis, Genetic translation
Format: Document (PDF)

Title: Methodologies Towards One Pot Synthesis of α-Arylated Amino Esters And Applications in Total Synthesis.
Creator: Samanta, Shyam S., Roche, Stephane P., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: In this dissertation, we discuss the development of a synthetic method to functionalize various α-haloglycine esters, as key precursors to a large variety of non-proteinogenic α-amino acids (Xaas). At first, we discovered a very practical and high yielding acetyl chloride-mediated cascade reaction to synthesize α-arylated amino esters in one-pot. In this multicomponent reaction (MCR), a primary carbamate was condensed with a glyoxylate, followed by an in situ halogenation which proved...
Show moreIn this dissertation, we discuss the development of a synthetic method to functionalize various α-haloglycine esters, as key precursors to a large variety of non-proteinogenic α-amino acids (Xaas). At first, we discovered a very practical and high yielding acetyl chloride-mediated cascade reaction to synthesize α-arylated amino esters in one-pot. In this multicomponent reaction (MCR), a primary carbamate was condensed with a glyoxylate, followed by an in situ halogenation which proved essential to trigger the final Friedel−Crafts functionalization. After careful reaction optimization, a plethora of arene nucleophiles were reacted with high regioselectively in CHCl3 at low temperatures (Method A) while less activated arenes reacted more cleanly in CH3CN and at higher temperatures (Method B). To broaden the scope of this reaction to acid sensitive nucleophiles, a one-pot reaction was designed via evaporation of all acid by-products at the α-haloglycine stage. The anion-binding Schreiner’s thiourea catalyst proved to be extremely efficient to promote this complementary approach (Method C) which relies on the chloride leaving group activation by the catalyst to assist the functionalization stage and deliver the α-amino ester product. In the second chapter, some highly practical and efficient preparations of α-haloglycine esters in one-pot have been developed to generate useful precursors of non-proteinogenic α-amino esters. Also, a mild and unique AcOH(cat.)/AcCl system was found to promote an autocatalytic-like condensation/deoxy halogenation and facilitate the multicomponent assembly of non-proteinogenic α-amino esters. Friedel–Crafts reaction between α-chloroglycine and N-methylindole have been studied in details to understand the mechanistic intricacy of this reaction. Our findings through the initial kinetic profiling support that the arylation likely proceeds via a SN1-like (or SN2C+) mechanism. In third chapter, we discuss the development of the most challenging α,α-disubstituted amino esters in a multicomponent fashion. Our results highlight that the MCR proceeds via the formation of an enamide intermediate, which is further tautomerized to corresponding iminium to produce the desired product. In collaboration with Eli Lilly at the Automated Synthesis Laboratory (ASL), we have developed silver (I) salts mediated Friedel–Crafts reaction for synthesis of α-trifluoromethylated α-amino esters on a fully automatized robot.
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Date Issued: 2018
PURL: http://purl.flvc.org/fau/fd/FA00013160
Subject Headings: Esters, Synthesis, Amino Acids
Format: Document (PDF)

Title: Molecular characterization of the injected venom of Conus ermineus.
Creator: Rivera-Ortiz, Jose A., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: Cone snails are predatory marine animals that rely on their venom components to immobilize and capture their prey. According to the type of prey preference, cone snails can be divided into three groups: vermivorous, molluscivorous and piscivorous. Conus ermineus had been identified as the only piscivorous snail of the Atlantic Ocean. Cone snail venom is a complex and rich sources of natural toxins. The majority of the components of the venom are peptidic in nature, and they act over different...
Show moreCone snails are predatory marine animals that rely on their venom components to immobilize and capture their prey. According to the type of prey preference, cone snails can be divided into three groups: vermivorous, molluscivorous and piscivorous. Conus ermineus had been identified as the only piscivorous snail of the Atlantic Ocean. Cone snail venom is a complex and rich sources of natural toxins. The majority of the components of the venom are peptidic in nature, and they act over different ionic channels and membrane receptors. Initial studies using mixture of venom collected from dissected venom ducts concluded that the venom from the same species do not exhibit unusual peptide polymorphism [Olivera, Hillyard, et al., 1995] and that the only major difference between individuals of the same species are different concentrations of the venom components [Vianna, et al., 2005]. For this study, peptides in the injected venom were collected from individual snails and characterized usin g analytical RP-HPLC for a maximum of three years. The different fractions collected were processed through capillary HPLC coupled with Q-TOF ESI-MS, and compared with analytical RP-HPLC fractions processed with MALDI-TOF MS. This study demonstrates that there is an animal-to-animal variation in the peptide components of the injected venom. The injected venom remains relatively constant over time for specific specimens in captivity. Finally, there are some peptides that had been found in all specimens both by MALDI-TOF MS and by ESI-MS. In this study, these peptides are called "molecular fingerprint" peptides. Based on matches of their derived masses to those predicted by published cDNA sequences, nine novel peptides were putatively identified. This study establishes that variations due to enzymatic posttranslational modification are omitted when we consider only information extrapolated from cDNA., The results of this study support the idea of the existence of a novel regulatory mechaism to expressed specific venom peptides for injection into the prey.
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Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3333310
Subject Headings: Gastropoda, Venom, Peptides, Structure, Coastal ecology
Format: Document (PDF)

Title: MONITORING COLLAGENOLYSIS UTILIZING TRIPLE HELICAL PEPTIDE PROBES.
Creator: Tokmina-Roszyk, Michal, Fields, Gregg B., Florida Atlantic University, Department of Chemistry and Biochemistry, Charles E. Schmidt College of Science
Abstract/Description: Collagen is the major structural scaffold in the body and serves as barrier between tissues, and thus its turnover is tightly regulated. Collagen triple-helical structure renders it resistant to general proteolysis. Several proteases are capable of cleaving the triplehelical regions of collagen, including several mammalian matrix metalloproteinases (MMPs) and bacterial collagenases. MMP-mediated collagenolysis is associated with numerous diseases and some bacterial collagenases have found...
Show moreCollagen is the major structural scaffold in the body and serves as barrier between tissues, and thus its turnover is tightly regulated. Collagen triple-helical structure renders it resistant to general proteolysis. Several proteases are capable of cleaving the triplehelical regions of collagen, including several mammalian matrix metalloproteinases (MMPs) and bacterial collagenases. MMP-mediated collagenolysis is associated with numerous diseases and some bacterial collagenases have found clinical application use due to their efficiency in the hydrolysis of the collagen triple-helix. A selective Förster resonance energy transfer triple-helical peptide (fTHP) probe for monitoring the activity of Clostridial collagenase has been developed. The fTHP [sequence: Gly-mep-Flp-(Glyvi Pro-Hyp)4-Gly-Lys(Mca)-Thr-Gly-Pro-Leu-Gly-Pro-Pro-Gly-Lys(Dnp)-Ser-(Gly-Pro-Hyp)4-NH2] was stable at 37 °C and was efficiently hydrolyzed by bacterial collagenase (kcat/KM = 25,000 s -1 M-1) but not by clostripain, trypsin, neutral protease, thermolysin, or elastase. The bacterial collagenase fTHP assay can be utilized in applications where specific activity towards triple-helical collagen needs to be evaluated, such as isolation of cells from various tissues. An fTHP scaffold was also utilized to evaluate the sequence preferences of eight MMPs. Residues spanning from P3 to P11 investigated using a positional scanning synthetic combinatorial library. Deconvolution of the library data revealed distinct motifs for several MMPs and discrimination among closely related MMPs. The results of this study show that the P10 11 substrate play an important role in the collagenase-substrate interactions and that modifying these residues can drastically affect the affinity of MMPs towards THP substrates. The identified sequence preferences of MMPs will enable the design of selective triple-helical MMP probes that could be used for monitoring in vivo enzyme activity and enzyme-facilitated drug delivery.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013422
Subject Headings: Collagen, Peptides, Matrix Metalloproteinases, Microbial Collagenase, Molecular Probes
Format: Document (PDF)

Title: MULTIVALENT PROTEIN GLYCOSYLATION: A DRIVING FORCE OF CANCER PROGRESSION AND ALZHEIMER’S DISEASE PATHOGENESIS.
Creator: Singh, YashoNandini, Cudic, Maré, Florida Atlantic University, Department of Chemistry and Biochemistry, Charles E. Schmidt College of Science
Abstract/Description: Glycosylation is a frequent and heterogeneous post-translational protein modification occurring in all domains of life. Aberrant cell-surface glycosylation is shown to mediate several processes involved in tumor cell proliferation, adhesion, and metastasis. Recent findings linked altered protein glycosylation to Alzheimer’s disease (AD) pathogenesis. One key obstacle in studying functional consequences of glycosylation has been the lack of structurally defined glycopeptide or protein model...
Show moreGlycosylation is a frequent and heterogeneous post-translational protein modification occurring in all domains of life. Aberrant cell-surface glycosylation is shown to mediate several processes involved in tumor cell proliferation, adhesion, and metastasis. Recent findings linked altered protein glycosylation to Alzheimer’s disease (AD) pathogenesis. One key obstacle in studying functional consequences of glycosylation has been the lack of structurally defined glycopeptide or protein model compounds for biochemical studies at the molecular level. For tumor progression, studies are crucial towards understanding the glycan-lectin recognition process tied to deciphering the information contained in glycan structures and for AD, foundational studies are necessary for understanding the role of O-glycosylation in protein processing and its fate toward the amyloid pathway. In chapter 1, a highly O-glycosylated transmembrane and cancer-associated mucin protein, MUC1, is used as a model for designing synthetic tools for exploring its role in metastasis via association with lectins and specificity of anti-MUC1 antibodies. This dissertation for the first time presents a MUC1-based positional scanning synthetic glycopeptide combinatorial library that varies in the number and location of tumor-associated Tn antigen. The importance of defined structural complexity for evaluating glycan density and glycosylation patterns for binding to Tn-specific plant lectins and anti-MUC1 (mouse) monoclonal antibodies was revealed using an enzyme-linked lectin assay (ELLA). Chapter 2 addressed the growing significance of peptide lectinomimics for recognizing tumor-specific glycans. Fluorescently labelled alanine scan analogues of odorranalectin (OL), a cyclic peptide that exhibits lectin like properties, were screened for binding BSA-conjugated monosaccharides using ELLA. Results revealed that Lys5, Phe7, Tyr9, Gly12, Leu14, and Thr17 were crucial for binding BSA-L-fucose, BSA-Dgalactose and BSA-N-acetyl-D-galactosamine. The thermodynamics of binding of the selected alanine analogues was evaluated by isothermal titration calorimetry. The thermodynamic profile of interactions with asialofetuin exhibits shift to an entropy-driven mechanism compared to fucoidan, which displayed an enthalpy-entropy compensation, typically associated with the carbohydrate-lectin recognition process. Chapter 3 focused on amyloid-precursor protein (APP) O-glycosylation and its role in AD pathogenesis. We synthesized native and Swedish-mutated (glyco)peptides with O-GalNAc moiety on Thr663 and/or Ser667 or Tyr681 to explore the role of glycosylation on conformation, secretase activity, and aggregation kinetics of Aβ40. Our results show that conformation is strongly dependent on external conditions such as buffer ions and solvent polarity as well as internal modifications of (glyco)peptides such as length, O-glycosylation, and Swedish mutation (Lys670Asn/Met671Leu). Furthermore, the level of β-secretase activity significantly increased for the glycopeptides containing the Swedish mutation compared to their nonglycosylated and native counterparts. Lastly, glycopeptides impacted the kinetics of Aβ40 aggregation by significantly increasing the lag phase and delaying aggregation onset, however, this effect was less pronounced for its Swedish-mutated counterparts.
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Date Issued: 2022
PURL: http://purl.flvc.org/fau/fd/FA00013949
Subject Headings: Glycosylation, Alzheimer Disease, Lectins
Format: Document (PDF)

Title: Natural Product Studies of Marine Organisms from the Western Atlantic.
Creator: Hall, Andrew, West, Lyndon, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: The projects described in this dissertation are focused on compounds derived from marine organisms collected from the western Atlantic marine environment. Chapter 1 provides an introduction to the study of natural products chemistry, marine natural products, and overview of the research undertaken from natural product chemists. Chapter 2 describes the isolation and structure elucidation of a series of rare diterpenoids from the gorgonian Briareum asbestinum, together with their conformational...
Show moreThe projects described in this dissertation are focused on compounds derived from marine organisms collected from the western Atlantic marine environment. Chapter 1 provides an introduction to the study of natural products chemistry, marine natural products, and overview of the research undertaken from natural product chemists. Chapter 2 describes the isolation and structure elucidation of a series of rare diterpenoids from the gorgonian Briareum asbestinum, together with their conformational analysis and biosynthetic interconversions. These rare diterpenes from Briareum asbestinum are linked by an unusual transannular oxa-6π electrocyclization which is described in detail and this work demonstates the biomimetic hemisynthesis of briareolate esters L (19) to B (22) achieved via an intermediary, briareolate ester G (2), through a controlled set of photoinduced isomerizations and a unique photochromic transannular oxa-6π electrocyclization. This work focuses largely on the mechanistic understanding of the photochemical production of these briarane diterpenoids and illustrates a unique UVA/UVC, photochromic switch which induces a transannular oxa- 6π electrocyclization. Chapter 3 describes the assay-guided isolation of marine antioxidants. This chapter focuses on the screening of marine organism extracts using the Ferric Reducing Antioxidant Power (FRAP) assay for antioxidant activity guided isolation of marine natural products. The chapter concludes with the activity guided isolation and structural elucidation of 1-O-palmitoyl-2-O-myristoyl-3-O-(6-sulfo-α-D-quinovopyranosyl)- glycerol (40) to show direct antioxidant potential through FRAP analysis. Chapter 4 describes the isolation, structural elucidation and pharmacological evaluation of the novel secondary metabolites iso-PsA(45), Iso-PsC (46), iso-PsD (47) as well as known Pseudopterosins A(41), B(42), C(43), D(44), K(48), K2’OAc(49), K2’OAc(50). These secondary metabolites were evaluated for both cytotoxicity. The chapter concludes with the screening of these compounds as αβ-amyloid fibril modulators utilizing atomic force microcopy (AFM).
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004666
Subject Headings: Marine natural products., Diterpenes., Marine metabolites
Format: Document (PDF)

Title: Natural products biosynthesis in the gorgonian Eunicea fusca and other marine invertebrates.
Creator: Saleh, Maysoon Baker, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: Marine organisms represent a rich source of bioactive secondary metabolites. These bioactive compounds are often present in trace quantities in the organism and their clinical development has been hampered by lack of an available supply. The supply problem can be addressed by a chemical synthesis or through biological methods such as aquaculture, cell culture or enzymatic means. The overall goal of this research was to conduct biosynthetic studies of the marine alkaloids ET 743 and stevensine...
Show moreMarine organisms represent a rich source of bioactive secondary metabolites. These bioactive compounds are often present in trace quantities in the organism and their clinical development has been hampered by lack of an available supply. The supply problem can be addressed by a chemical synthesis or through biological methods such as aquaculture, cell culture or enzymatic means. The overall goal of this research was to conduct biosynthetic studies of the marine alkaloids ET 743 and stevensine, and the diterpenes fuscol and fuscoside A-D. The motivation for this is that biosynthetic data could be used to develop a biotechnological production method. ET 743, an anti-cancer agent, is the main alkaloid produced by Ecteinascidia turbinata. Since DKP of DOPA is a key intermediate in ET 743 biosynthesis and since the chemical synthesis of DOPA derivatives is problematic, we developed an enzymatic production method using tyrosine hydroxylase as a tool to oxidize DKP of tyrosine to DKP of DOPA. Stevensine and oroidin are bromopyrrole alkaloids isolated from the marine sponge Axinella corrugate. Stevensine exhibits antimicrobial activity as well as cytotoxicity in vitro against murine leukemia cells. We were able to develop an enzyme based method to identify the amino acids precursors for Stevensine and oroidin using a cell-free extract of the sponge. Fuscosides are diterpene arabinose glycosides isolated from the Caribbean soft coral Eunicea fusca. They and the aglycone fuscol are potent anti-inflammatory compounds with long-lasting effect and have a selective inhibitory action against leukotriene production in murine models of inflammation. We identified and confirmed the intermediary of the diterpenes cyclase product using radioactivity-guided isolation. Furthermore, we completed the elucidation of fuscol biosynthetic pathway. We provided evidence for the use of these diterpenes as oxygen scavengers in the organism. In addition, we investigated the biosynthetic source of the diterpenes in E. fusca and we provided direct evidence for their production by the microbes (bacteria or fungi) present in the organism.
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Date Issued: 2005
PURL: http://purl.flvc.org/fcla/dt/12147
Subject Headings: Chemistry, Biochemistry
Format: Document (PDF)

Title: Neuroprotection from induced glutamate excitotoxicity by Conus brunneus conopeptides in a stroke-related model.
Creator: Crouch, Rebecca A., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: Cone snails are carnivorous marine mollusks, utilizing their neuropeptide-rich venom for prey capture. The venom of Conus brunneus, a wide-spread Eastern Pacific vermivore, has not been extensively studied. In the current work, peptides from the dissected venom were characterized and tested using preliminary bioassays. Six peptides (A-F) were isolated and tested. Three peptide identities were determined by comparison with previously reported data: bru9a (A), bru3a (F), and an a-conotoxin (E)....
Show moreCone snails are carnivorous marine mollusks, utilizing their neuropeptide-rich venom for prey capture. The venom of Conus brunneus, a wide-spread Eastern Pacific vermivore, has not been extensively studied. In the current work, peptides from the dissected venom were characterized and tested using preliminary bioassays. Six peptides (A-F) were isolated and tested. Three peptide identities were determined by comparison with previously reported data: bru9a (A), bru3a (F), and an a-conotoxin (E). Preliminary screening in a stroke-related model of induced glutamate excitotoxicity in primary neuronal cells and PC12 cell cultures indicated potential neuroprotective activity of peptide fractions A, D, and F. Further testing is necessary to determine and verify structure, activity, target, and mechanism of action of the promising peptides from C. brunneus, which may prove effective neuropharmacological agents to treat stroke.
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Date Issued: 2013
PURL: http://purl.flvc.org/fcla/dt/3362331
Subject Headings: Gastropoda, Venom, Therapeutic use, Peptides, Structure, Neuroprotective agents, Central nervous system, Diseases, Treatment
Format: Document (PDF)

Title: New stereoselective reactions to form amido alkyl c-n and vinyl triflate c-o bonds via carbocation intermediates & ultrafast silicon fluorination methodologies for applications in pet imaging.
Creator: Alhuniti, Mohammed, Lepore, Salvatore D., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: We report here the development of a Lewis acid catalyzed method for the dehydrative coupling of cyclic alcohols and nitriles to form amides with retention of configuration. By contrast, the formation of amides by nitrile trapping of carbocations (Ritter reaction) usually affords racemic product. The present reaction was accomplished by first converting alcohol starting materials to their corresponding chlorosulfites in situ. Even after an extensive search, only copper (II) salts were able to...
Show moreWe report here the development of a Lewis acid catalyzed method for the dehydrative coupling of cyclic alcohols and nitriles to form amides with retention of configuration. By contrast, the formation of amides by nitrile trapping of carbocations (Ritter reaction) usually affords racemic product. The present reaction was accomplished by first converting alcohol starting materials to their corresponding chlorosulfites in situ. Even after an extensive search, only copper (II) salts were able to produce the desired conversion of these chlorosulfites to amides though with low catalytic turnover. Improving the turnover without deteriorating the stereochemical outcome was eventually accomplished by a careful selection of the reagent addition sequence and through the removal of gaseous byproducts. This Ritter-like coupling reaction proceeds in good yields with secondary cyclic alcohols under mild conditions. The stereochemical outcome likely due to fast nucleophilic capture of a non-planar carbocations (hyperconjomers) stabilized by ring hyperconjugation.
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Date Issued: 2014
PURL: http://purl.flvc.org/fau/fd/FA00004262
Subject Headings: Intermediates (Chemistry), Nuclear medicine, Organometallic chemistry, Physical organic chemistry, Reaction mechanisms (Chemistry), Tomography, Emission
Format: Document (PDF)

Title: Nuclear magnetic resonance spectroscopic studies of metallocene (IVB) squarate polymers and other metallocene (IVB)-containing polymers.
Creator: Li, Alicia Qing, Florida Atlantic University, Carraher, Charles E., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: Group IVB metallocene polymers and oligomers undergo a pi-sigma rearrangement of the cyclopentadienyl moieties in DMSO based on NMR data. The sigma-Cp rings are stereochemically rigid at room temperature.
Date Issued: 1991
PURL: http://purl.flvc.org/fcla/dt/14681
Subject Headings: Organometallic polymers, Metallocenes, Nuclear magnetic resonance
Format: Document (PDF)

Title: Peptidomic analysis and characterization of the venom from Conus purpurascens.
Creator: Rodriguez, Alena, Mari, Frank, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: The venom of cone snails is a potent cocktail of peptides, proteins, and other small molecules. Several of the peptides (conopeptides and conotoxins) target ion channels and receptors and have proven useful as biochemical probes or pharmaceutical leads. In this study, the venom of a fish-hunting cone snail, Conus purpurascens was analyzed for intraspecific variability; α-conotoxins from the venom were isolated by high performance liquid chromatography, identified by mass spectrometry and...
Show moreThe venom of cone snails is a potent cocktail of peptides, proteins, and other small molecules. Several of the peptides (conopeptides and conotoxins) target ion channels and receptors and have proven useful as biochemical probes or pharmaceutical leads. In this study, the venom of a fish-hunting cone snail, Conus purpurascens was analyzed for intraspecific variability; α-conotoxins from the venom were isolated by high performance liquid chromatography, identified by mass spectrometry and nuclear magnetic resonance, and tested in a electrophysiological assay in Drosophila melanogaster; the effects of diet change on venom composition was investigated. It has been determined that each specimen of C. purpurascens expresses a distinct venom, resulting in the expression of more than 5,000 unique conopeptides across the species. α- conotoxin PIA was shown to inhibit the Dα7 nicotinic acetylcholine receptor.
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Date Issued: 2015
PURL: http://purl.flvc.org/fau/fd/FA00004403, http://purl.flvc.org/fau/fd/FA00004403
Subject Headings: Conidae -- Environmental aspects, Drosophila melanogaster, Gastropoda -- Venom, Peptides -- Structure, Venom
Format: Document (PDF)

Title: PHOSPHORUS SEQUESTRATION AND BIOREMEDIATION: PHOSPHORUS-31 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY.
Creator: Duersch, Bobby G., Louda, J. William, Florida Atlantic University, Department of Chemistry and Biochemistry, Charles E. Schmidt College of Science
Abstract/Description: Eutrophication is an increase in primary plant nutrients (Nitrogen [N] and Phosphorus [P]) in oceans, estuaries and lakes. The consequences of eutrophication are harmful algal blooms (HABs), resulting in algal toxin production and the depletion of oxygen as the extensive biomass decays. P is often the limiting nutrient and is viewed as a significant environmental problem. Most of the excess P that enters aquatic ecosystems originates from anthropogenic sources such as fertilizers, sewage,...
Show moreEutrophication is an increase in primary plant nutrients (Nitrogen [N] and Phosphorus [P]) in oceans, estuaries and lakes. The consequences of eutrophication are harmful algal blooms (HABs), resulting in algal toxin production and the depletion of oxygen as the extensive biomass decays. P is often the limiting nutrient and is viewed as a significant environmental problem. Most of the excess P that enters aquatic ecosystems originates from anthropogenic sources such as fertilizers, sewage, animal wastes, compost, crop residues, and wastewater. Over time, one of the main reservoirs of P becomes organic P (Po). We investigated the chemical nature and dynamics of P in cyanobacteria, horse manure, stormwater treatment areas, and rice fields. To better understand the chemical nature of P, the identification of specific P compounds was required, which was achieved through 31P nuclear magnetic resonance (NMR) spectroscopy. We investigated how paramagnetic metals and quadrupolar nuclei cause severe line broadening, peak shifts, and decreased the signal to noise ratio. Results revealed that certain Po forms are readily bioavailable to Microcystis aeruginosa. Additionally, the potential heterotrophic use of the organic portion (e.g., glucose, glycerol) of these P compounds are indicated for the growth and persistence of Microcystis aeruginosa. We showed that the cultivation of rice (Oryza sativa L.) had been found to effectively reduce P from agrarian soil and water through plant uptake and, therefore, minimizing downstream eutrophication. Soil, water, sugarcane, and rice plants at two different stages were analyzed for twelve different elements. Finally, we examined how a “relic” agrarian ditch in Stormwater Treatment Area 1 East (STA-1E) can be used for the retention and sequestration of P and other nutrients. The STAs were established to capture P from agricultural and other sources before reaching the Everglades. Retained P is primarily stored in the wetland soils and sediments, generated through a collection of interrelated physical, chemical, and biological processes.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013594
Subject Headings: Nuclear magnetic resonance spectroscopy, Eutrophication, Phosphorus--Environmental aspects, Bioremediation
Format: Document (PDF)

Title: Photodegradation of 2-mercaptobenzothiazole disulfide and related benzothiazoles.
Creator: Zajickova, Zuzana, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: Benzothiazoles are heterocyclic compounds used predominantly as rubber vulcanization accelerators. The overall goal of our research was to investigate the photodegradation behavior of 2-mercaptobenzothiazole disulfide, its degradation product 2-mercaptobenzothiazole, and further degradation product benzothiazole. Modern analytical techniques were utilized to follow photodegradation process at arbitrary intervals. A chromatographic method using reverse phase liquid chromatography was developed...
Show moreBenzothiazoles are heterocyclic compounds used predominantly as rubber vulcanization accelerators. The overall goal of our research was to investigate the photodegradation behavior of 2-mercaptobenzothiazole disulfide, its degradation product 2-mercaptobenzothiazole, and further degradation product benzothiazole. Modern analytical techniques were utilized to follow photodegradation process at arbitrary intervals. A chromatographic method using reverse phase liquid chromatography was developed for the separation of benzothiazoles in the irradiated mixture. Direct photolysis of benzothiazole and 2-mercaptobenzothiazole in methanol at 253.7 and 313 nm in the presence or absence of oxygen was investigated at first. Benzothiazole was found to undergo photodimerization into 2,2'-bibenzothiazole, and in the presence of oxygen to give two additional photoproducts - 2-hydroxybenzothiazole and 2-methylbenzothiazole. The major degradation products of 2-mercaptobenzothiazole are benzothiazole and 2-benzothiazolesulfonic acid, with 2,2'-thiobisbenzothiazole, 2,x'-thiobisbenzothiazole (x = 4, 5, 6, 7), and 2-mercaptobenzothiazole disulfide as the minor degradation products. Direct photolysis of 2-mercaptobenzothiazole disulfide was investigated in four different solvents, at two different wavelengths (253.7 and 313 nm) and concentrations in the presence or absence of oxygen. In all cases 2-mercaptobenzothiazole and 2,x'-thiobisbenzothiazole were detected as the degradation products and in acetonitrile 2-thiocyanatobenzothiazole was also detected. A mechanism is proposed to rationalize the formation of photodegradation products. The effects of solvent, irradiation wavelength, and duration of irradiation time, concentration of the starting material and presence or absence of oxygen are summarized as well. It was observed that photodecomposition at 253.7 nm occurred at a much faster rate than at 313 nm and that less concentrated solutions decomposed faster. At higher concentration of 2-mercaptobenzothiazole its disulfide was detected as one of the degradation products. Methylated products were detected in methanol and acetonitrile and photoreaction took longer in polar protic solvents. Oxygenated products were formed in presence of oxygen and the photoreaction was slower as well in comparison to degassed solutions.
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Date Issued: 2006
PURL: http://purl.flvc.org/fcla/dt/12219
Subject Headings: Chemistry, Analytical, Chemistry, Physical
Format: Document (PDF)

Title: Photodegradation of bromacil and terbacil by ultraviolet radiation.
Creator: Johnson, Hannah Kalyani, Florida Atlantic University, Parkanyi, Cyril, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: The photodegradation of bromacil (5-bromo-3-sec-butyl-6-methyluracil) and terbacil (5-chloro-3-tert-butyl-6-methyluracil) by ultraviolet radiation has been investigated. Irradiation of aerated aqueous solutions of the title compounds (25 ppm), led to fast degradation of both. The reactions were found to follow first order kinetics with rate constants 5.77x10^-1 hr^-1 in the case of bromacil and 8.45x10^-2 hr^-1 in the case of terbacil. Degradation in ethanol and cyclohexane was also studied,...
Show moreThe photodegradation of bromacil (5-bromo-3-sec-butyl-6-methyluracil) and terbacil (5-chloro-3-tert-butyl-6-methyluracil) by ultraviolet radiation has been investigated. Irradiation of aerated aqueous solutions of the title compounds (25 ppm), led to fast degradation of both. The reactions were found to follow first order kinetics with rate constants 5.77x10^-1 hr^-1 in the case of bromacil and 8.45x10^-2 hr^-1 in the case of terbacil. Degradation in ethanol and cyclohexane was also studied, but the solutions were not analyzed for photoproducts. The photoreaction mixture of both the herbicides in water showed four peaks on GC, indicating four photoproducts. Loss of halogens from the heterocyclic ring has been observed as shown by the presence of Br- in the case of bromacil and Cl- in the case of terbacil in the photoreaction solution. 6-Methyluracil which was isolated from the aqueous fraction of the photoreaction mixture was the common photoproduct from both bromacil and terbacil. From the organic fractions 3-sec-butyl-5-acetyl-5-hydroxyhydantoin was identified in the case of bromacil and 3-tert-butyl-5-acetyl-5-hydroxyhydantoin in the case of terbacil. The other two photoproducts were left unidentified.
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Date Issued: 1993
PURL: http://purl.flvc.org/fcla/dt/14929
Subject Headings: Ultraviolet radiation, Photochemistry--Deterioration, Herbicides, Uracil
Format: Document (PDF)

Title: Physiological and non-physiological regulation of indoleamine-2,3-dioxygenase.
Creator: Sempertegui Plaza, Tito S., Terentis, Andrew C., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry, Florida Atlantic University
Abstract/Description: The heme enzyme indoleamine 2,3-dioxygenase (IDO) catalyses L-tryptophan (LTrp) oxidation along the kynurenine pathway and is a key regulator of the mammalian immune system. It’s unknown if the enzyme is under redox control and the use of new potent inhibitors of IDO represents a novel therapeutic approach.
Date Issued: 2013
PURL: http://purl.flvc.org/fau/fd/FA00004256
Format: Document (PDF)

Title: POLARIZED CRYSTAL SPECTRA OF QUADRATE CHROMIUM(III) COMPLEXES.
Creator: KLEIN, ROBERT LEWIS, JR., Florida Atlantic University, Perumareddi, Jayarama R., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: The polarized crystal spectra of a series of tetragonal trans- diacidobis (ethylenediamine) chromium (III) complexes, trans-[Cr(en)2XY], where X= Y = Br-, H2O, F-, Cl- and X= H2O, Y = OH-, F-, have been measured at liquid nitrogen temperature, achieving better resolution of the split components of the cubic spin-allowed bands, and also definite energy level assignments. The observed band positions have been fitted with the predicted transition energies by the use of the appropriate energy...
Show moreThe polarized crystal spectra of a series of tetragonal trans- diacidobis (ethylenediamine) chromium (III) complexes, trans-[Cr(en)2XY], where X= Y = Br-, H2O, F-, Cl- and X= H2O, Y = OH-, F-, have been measured at liquid nitrogen temperature, achieving better resolution of the split components of the cubic spin-allowed bands, and also definite energy level assignments. The observed band positions have been fitted with the predicted transition energies by the use of the appropriate energy equations for d^3 configuration immersed in tetragonal fields with full configuration interaction. The ligand field parameters, which include the cubic and axial, and the electron correlation parameter B have been evaluated by such a fitting. The derived parameters have been analyzed and their significance discussed. Using thick crystals, we have uncovered a rich doublet structure in some of the complexes and tentative values of the electron correlation parameter C have been obtained for all the complexes.
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Date Issued: 1971
PURL: http://purl.flvc.org/fcla/dt/13454
Subject Headings: Chromium
Format: Document (PDF)

Title: PRION FRAGMENT 106-128: AN INVESTIGATION OF AMYLOID FORMATION AND INHIBITION.
Creator: Regmi, Deepika, Du, Deguo, Florida Atlantic University, Department of Chemistry and Biochemistry, Charles E. Schmidt College of Science
Abstract/Description: Misfolding and aggregation of Cellular Prion Protein (PrPc) is a major molecular process involved in the pathogenesis of Prion diseases. An N-terminal portion of the Prion protein, PrP106-128, is a 23-residue peptide fragment characterized by an amphipathic structure with two domains: a hydrophilic N-terminal domain and a hydrophobic C-terminal domain. Here, we studied the aggregation properties of the prion fragment peptide PrP106-128. The results show that the peptide aggregates in a...
Show moreMisfolding and aggregation of Cellular Prion Protein (PrPc) is a major molecular process involved in the pathogenesis of Prion diseases. An N-terminal portion of the Prion protein, PrP106-128, is a 23-residue peptide fragment characterized by an amphipathic structure with two domains: a hydrophilic N-terminal domain and a hydrophobic C-terminal domain. Here, we studied the aggregation properties of the prion fragment peptide PrP106-128. The results show that the peptide aggregates in a concentration-dependent manner in an aqueous solution and that the aggregation is sensitive to pH and the preformed amyloid seeds.Furthermore, we show that the zwitterionic POPC liposomes moderately inhibit the aggregation of PrP(106–128), whereas POPC/cholesterol (8:2) vesicles facilitate peptide aggregation likely due to the increase of the lipid packing order and membrane rigidity in the presence of cholesterol. In addition, anionic lipid vesicles of POPG and POPG/cholesterol above a certain concentration accelerate the aggregation of the peptide remarkably. The strong electrostatic interactions between the N-terminal region of the peptide and POPG may constrain the conformational plasticity of the peptide, preventing insertion of the peptide into the inner side of the membrane and thus promoting fibrillation on the membrane surface. The results suggest that the charge properties of the membrane, the composition of the liposomes, and the rigidity of lipid packing are critical in determining peptide adsorption on the membrane surface and the efficiency of the membrane in catalyzing peptide oligomeric nucleation and amyloid formation.
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Date Issued: 2023
PURL: http://purl.flvc.org/fau/fd/FA00014356
Subject Headings: Prion Proteins, Prion diseases, Epigallocatechin gallate, Amyloid
Format: Document (PDF)

Title: Purification and characterization of two members of the protein tyrosine phosphatase family: dual specificity phosphatase PVP and low molecular weight phosphatase WZB.
Creator: Livingston, Paula A., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: Two protein tyrosine phosphatases, dual specificity phosphatase PVP and low molecular weight phosphatase WZB were purified and characterized. PVP was expressed as inclusion bodies and a suitable purification and refolding method was devised. Enzyme kinetics revealed that p-nitrophenylphosphate and (Sb(B-naphthyl phosphate were substrates with KM of 4.0mM and 8.1mM respectively. PVP showed no reactivity towards phosphoserine. Kinetic characterization of WZB showed that only...
Show moreTwo protein tyrosine phosphatases, dual specificity phosphatase PVP and low molecular weight phosphatase WZB were purified and characterized. PVP was expressed as inclusion bodies and a suitable purification and refolding method was devised. Enzyme kinetics revealed that p-nitrophenylphosphate and (Sb(B-naphthyl phosphate were substrates with KM of 4.0mM and 8.1mM respectively. PVP showed no reactivity towards phosphoserine. Kinetic characterization of WZB showed that only pnitrophenylphosphate was a substrate with no affinity for Ç-naphthyl phosphate and phosphoserine. Optimal conditions for activity with PNPP were found at a pH of 5 with a KM of 1.1mM, kcat of 35.4s-1 and kcat/KM of 32.2s-1mM-1. Inhibition studies showed that phosphate, fluoride, and molybdate were competitive inhibitors with Ki of 3.2mM, 71.7mM, and 50.4(So(BM respectively and hydrogen peroxide abolished activity. Active site mutants of WZB Cys9Ser and Asp115Asn showed no activity.
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Date Issued: 2009
PURL: http://purl.flvc.org/FAU/332911
Subject Headings: Protein-tyrosine phosphatase, Cellular signal transduction, Cell cycle, Regulation, Membrane proteins, Structure-activity relationships, Protein kinases
Format: Document (PDF)

Title: Raman and surface-enhanced raman spectroscopy of G-quadruplexes.
Creator: Friedman, Samantha, Terentis, Andrew C., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: G-quadruplexes (G4s) are nucleic acid structures formed from π-stacked planar sets of four Hoogsteen hydrogen bonded guanine bases. G4s emerged as potential therapeutic targets based on their ability to modulate gene expression and inhibit the ability of telomerase to elongate chromosomal telomeres. Raman spectroscopy, polarized Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS), and other optical spectroscopic techniques were used to characterize the G4s formed by four different...
Show moreG-quadruplexes (G4s) are nucleic acid structures formed from π-stacked planar sets of four Hoogsteen hydrogen bonded guanine bases. G4s emerged as potential therapeutic targets based on their ability to modulate gene expression and inhibit the ability of telomerase to elongate chromosomal telomeres. Raman spectroscopy, polarized Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS), and other optical spectroscopic techniques were used to characterize the G4s formed by four different DNA sequences: human telomeric (HT), thrombin-binding aptamer (TBA), nuclease hypersensitive element III1 region of the c- Myc gene promoter (Myc), and a single loop-isomer of Myc (MycL1).
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Date Issued: 2015
PURL: http://purl.flvc.org/fau/fd/FA00004370, http://purl.flvc.org/fau/fd/FA00004370
Subject Headings: Nucleic acids, Binding sites (Biochemistry), Biochemical genetics, Raman spectroscopy, Raman effect, Surface enhanced, Spectroscopic imaging, Spectrum analysis
Format: Document (PDF)

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