Formulação de um biofilme para controlo da listéria em queijos

Dissertação de Mestrado, Tecnologia e Segurança Alimentar, 12 Fevereiro de 2016, Universidade dos Açores.

Biosynthesis and mode of action of ribosomally synthesized and post-translationally modified antimicrobial peptides

One of the greatest sources of biologically active compounds is natural products. Often these compounds serve as platforms for the design and development of novel drugs and therapeutics. The overwhelming amount of genomic information acquired in recent years has revealed that ribosomally synthesized and post-translationally modified natural products are much more widespread than originally anticipated. Identified in nearly all forms of life, these natural products display incredible structural diversity and possess a wide range of biological functions that include antimicrobial, antiviral, anti-inflammatory, antitumor, and antiallodynic activities. The unique pathways taken to biosynthesize these compounds offer exciting opportunities for the bioengineering of these complex molecules. The studies described herein focus on both the mode of action and biosynthesis of antimicrobial peptides. In Chapter 2, it is demonstrated that haloduracin, a recently discovered two-peptide lantibiotic, possesses nanomolar antimicrobial activity against a panel of bacteria strains. The potency of haloduracin rivals that of nisin, an economically and therapeutically relevant lantibiotic, which can be attributed to a similar dual mode of action. Moreover, it was demonstrated that this lantibiotic of alkaliphile origin has better stability at physiological pH than nisin. The molecular target of haloduracin was identified as the cell wall peptidoglycan precursor lipid II. Through the in vitro biosynthesis of haloduracin, several analogues of Halα were prepared and evaluated for their ability to inhibit peptidoglycan biosynthesis as well as bacterial cell growth. In an effort to overcome the limitations of in vitro biosynthesis strategies, a novel strategy was developed resulting in a constitutively active lantibiotic synthetase enzyme. This methodology, described in Chapter 3, enabled the production of fully-modified lacticin 481 products with proteinogenic and non-proteinogenic amino acid substitutions. A number of lacticin 481 analogues were prepared and their antimicrobial activity and ability to bind lipid II was assessed. Moreover, site-directed mutagenesis of the constitutively active synthetase resulted in a kinase-like enzyme with the ability to phosphorylate a number of peptide substrates. The hunt for a lantibiotic synthetase enzyme responsible for installing the presumed dehydro amino acids and a thioether ring in the natural product sublancin, led to the identification and characterization of a unique post-translational modification. The studies described in Chapter 4, demonstrate that sublancin is not a lantibiotic, but rather an unusual S-linked glycopeptide. Its structure was revised based on extensive chemical, biochemical, and spectroscopic characterization. In addition to structural investigation, bioinformatic analysis of the sublancin gene cluster led to the identification of an S-glycosyltransferase predicted to be responsible for the post-translational modification of the sublancin precursor peptide. The unprecedented glycosyltransferase was reconstituted in vitro and demonstrated remarkable substrate promiscuity for both the NDP-sugar co-substrate as well as the precursor peptide itself. An in vitro method was developed for the production of sublancin and analogues which were subsequently evaluated in bioactivity assays. Finally, a number of putative biosynthetic gene clusters were identified that appear to harbor the necessary genes for production of an S-glycopeptide. An additional S-glycosyltransferase with more favorable intrinsic properties including better expression, stability, and solubility was reconstituted in vitro and demonstrated robust catalytic abilities.

Sonata in E-flat Major for Violin and Piano, K.481

Soitinnus: Viulu, piano.

Patroas e meninas; afilhadas e madrinhas: gênero e raça como conteúdos de análise sobre a efetividade social do Decreto-Lei n.º 6.481, de 12 de junho de 2008, nas relações de trabalhoinfantil doméstico

Para dar voz e rosto aos sujeitos, considerando-os protagonistas de suas histórias, é preciso ouvi-los em escuta ativa: dialogar com suas histórias de vida. As falas coletados na pesquisa empírica oportunizaram a construção da categoria heurística como filhas, da qual abstraio, ao longo deste estudo, algumas possibilidades hermenêuticas. Os instrumentais interpretativos acolhidos neste trabalho sinalizam para algumas possibilidades de compreensão acerca da prática de exploração de meninas nos serviços domésticos. Esta prática, hoje ilegal no Brasil – podendo importar em crime contra a organização do trabalho, pela vigência do Decreto-Lei n.º 6.481, de 12 de junho de 2008, que regulamenta os arts. 3.º, alínea d, e 4.º da Convenção n.º 182 da OIT –, é proibida para menores de 18 anos. Contudo, as normativas legais e as políticas institucionais de enfrentamento não são óbices à formulação de novos discursos para velhas sociabilidades excludentes e estigmatizantes da mulher negra, principal mão-de-obra explorada nos serviços domésticos. Rediscutindo categorias, problematizando nomenclaturas e articulando a interlocução entre os atores envolvidos nesta prática, empreendo a tarefa de dar-lhes visibilidade social.

Na 50 Nachlass Arthur Schopenhauer - 'Schopenhauer-Archiv', 481 - Aufstellung der Leipziger Stadtobligationen

1 Blatt

Ms.Ff.F.Stoltze 3. 481 - Brief von Friedrich Stoltze an Lyda Stoltze

Frankfurter Latern: Produktion