The syntheses of s-triazolo[3,4-a]phthalazines (15, 3-R-TAP) by reaction of hydralazine (12, 1-hydrazinophthalazine) with N-protected amino acids and dipeptides under homogeneous (solution) and heterogeneous ("solid-phase") conditions are reported. Transition metal complexes containing the TAP ligand were prepared and their spectral properties investigated. The use of metal-ions and a cation-exchange resin (H+ form) were considered for the mild hydrolysis of side-chain amide bonds in TAP derivatives. The objective of these studies was to determine the feasibility of reacting the carboxyl groups in amino acids with hydralazine to afford the TAP derivatives as a method for peptide sequencing from the C-terminal residue. Hydralazine reacts with carboxylic acids to form an amide intermediate which undergoes ring closure with elimination of water to form the s-triazolo[3,4-a]phthalazine derivative. To promote the initial binding of hydralazine to the acid, coupling reagents were used to activate the carboxylate group towards nucleophilic attack. N-Ethyl-5-phenylisoxazolium-3'-sulfonate (17, NEPIS), 1-ethoxy -carbonyl-2-ethoxy-l,2-dihydroquinoline (27, EEDQ), various phosphorus compounds, carbodiimides, and chloroformates were carboxyl activating agents used to synthesize TAP derivatives. In solution studies, the carbodiimides (EDC, 16 and DCC, Si), NEPIS (17), and a combination of triphenylphosphite with imidazole are the most successful procedures for TAP synthesis In solid-phase studies, the best procedures for activating immobilized amino acids, are with isobuty'l chloroformate, NEPIS (l?), and DCC (51). Transition metal complexes were synthesized with the general formula: [M(3-H-TAP) (H20)6_n](C104)m (n = 4, m = 2, M = Co, Ni, Cu; n = 2, m = 2, M = Ni; n = 6, m = 3, M = Co). The infrared and visible spectra of these complexes are reported. [Co(.trien)C3-(N-Ac-gly)-TAP)J(C104)2 was also prepared and under acidic conditions, no hydrolysis of the side-chain amide bond was observed. There was also no significant hydrolysis of the side-chain with free ?+ 2+ 3-(N-Ac-gly)-TAP in the presence of Co and Cu under acidic conditions, or when it was eluted through a cation-exchange (H+ form) column. The decomposition of hydralazine in non-aqueous media was investigated and a major product of the decomposition was identified as diphthalazinylhydrazine {82). The implication of our studies is that the modification of amino acids with hydralazine is not yet a viable method for C-terminal peptide sequencing. Improvements are required for improving the yields of the coupled product, and the lack of a mild and selective method for hydrolyzing the C-terminal peptide bond limits the method at present to determination of the C-terminal residue only. / Science, Faculty of / Chemistry, Department of / Graduate

Present throughout all classes of life, antimicrobial peptides (AMPs) confer defense against bacteria, viruses, fungi, and insects. Identifying maize AMPs would provide breeders with a new defense resource. Here, the investigation of maize AMPs is reported. The distribution of AMPs within a panel of ten Mississippi maize inbred lines with varying resistance to Lepidoptera larvae feeding and Aspergillus infection is explored to characterize their observed resistances. Homology data-mining with two comprehensive AMP databases revealed 88 unique maize AMP protein sequences across 81 genes in the MaizeGDB B73 genome assembly. AMP-related polymorphic sites were identified using genomic primers. Analyses with qRT-PCR revealed 8 differentially expressed maize AMP genes. Computational 3D models of AMPs are limited, and models of these eight maize AMP genes were predicted. Two-dimensional electrophoresis gels were used to contrast protein profiles of inbreds with varying resistance to identify regions related to AMPs and other defense-related protein.

Abstract not available

Reproduction de : Thèse d'exercice : Médecine : Nancy 1 : 2006. / Titre provenant de l'écran-titre.

Thesis (Ph.D.)--University of Adelaide, School of Chemistry and Physics, Discipline of Chemistry, 2006. / Includes author's previously published papers. "July 2006" Bibliography: leaves 159-182. Also available in print form.

Undergraduate honors paper--Mount Holyoke College, 2008. Dept of Chemistry. / Includes bibliographical references (leaves 77-78).

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (p. [117]-123).

Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

Thesis advisor: Marc Snapper / Thesis advisor: Steven Bruner / Peptide natural products have diverse, elaborate scaffolds and are important leads in the development of new drugs. A complete understanding of the natural biosynthetic pathways of these compounds can improve chemical syntheses and boost bioengineering efforts. There are two classes of peptide natural products: ribosomal and nonribosomal peptides. Ribosomally produced and posttranslationally modified peptides (RiPPs) are produced by the ribosome using the 20 canonical amino acids and undergo extensive tailoring to yield the active natural products. Nonribosomal peptides (NRPs) are assembled through an enzyme dependent system and can incorporate over 500 different amino and acyl building blocks to impart complexity. These peptides can also undergo additional tailoring to further modify the core peptide. The microviridins are a class of RiPPs that are modified by two ATP dependent ligases to create a total of three macrocyclic bonds. We have solved the three dimensional protein structures of each of these ligases to establish the mechanism of substrate recognition and cyclization. Vancomycin is a NRP that contains five nonproteinogenic aromatic amino acids that are necessary for biological activity. One of these amino acids is derived from a polyketide pathway and undergoes a four-electron oxidation by a cofactor independent dioxygenase, DpgC. We have solved the structure of this enzyme and have established a radical mechanism. We have investigated this mechanism using synthetic probes and mutagenesis. We have examined O₂ binding using molecular dynamics and mutagenesis. NRPs are synthesized by the multidomain, modular nonribosomal peptide synthetases (NRPSs) in an enzyme templated, ATP-dependent manner. We have synthesized domain specific probes to study the structures and mechanisms of these pathways. Our continued work will provide the insight necessary to manipulate these pathways to provide biologically active compounds. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

<p>Several lines of cellular and physiological evidence have suggested the presence of a novel class of systemically mobile plant molecules that are recognized by antibodies generated against vertebrate atrial natriuretic peptides (ANPs). Functional characterization of these immunoanalogues, referred to as immunoreactive plant natriuretic peptides (irPNPs) or plant natriuretic peptides (PNPs), has shown that they play important roles in a number of cellular processes crucial for plant growth and maintenance of cellular homeostasis. Although the various biological roles of PNPs in plants are known, their exact mode of action remains elusive. To elucidate the mechanisms of action for these immunoanalogues, we have prepared a biologically active recombinant PNP from Arabidopsis thaliana (AtPNP-A) and the biological activity was demonstrated by showing its ability to induce water uptake into Arabidopsis thaliana protoplasts. In addition, the molecule was shown to downregulate photosynthesis while at the same time up-regulating respiration, transpiration as well as net water uptake and retention capacities in the sage Plectranthus ecklonii. Further analysis of the recombinant AtPNP-A indicated that the peptide can induce systemic response signalling though the phloem. A recombinant Arabidopsis wall associated kinase-like protein (AtWAKL10) that has a domain organization resembling that of vertebrate natriuretic peptide (NP) receptors was also partially characterized as a possible receptor for the recombinant AtPNP-A. Vertebrate NP receptors contain an extracellular ligand-binding domain and an intracellular guanylate cyclase (GC)/kinase domain and signal through the activity of their GC domain that is capable of generating intracellular cGMP from GTP. The structural resemblance of AtWAKL10 to vertebrate NP receptors could suggest a functional homology with receptor molecules and it is conceivable that such a receptor may recognize PNPs as ligands. The characterization of the recombinant AtWAKL10 showed that the molecule functions as both a GC and a kinase in vitro. This strengthened the suggestion that AtWAKL10 could be a possible AtPNP-A receptor especially considering the fact that AtPNP-A applications to plant cells also<br /> trigger cGMP transients. Furthermore, a bioinformatic analysis of the functions of AtPNP-A and AtWAKL10 has inferred both molecules in plant pathogen responses and defense mechanisms, thus indirectly functionally linking the two proteins.</p>