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About this book

Martin Stein's thesis describes a novel methodology for natural product discovery. Due to its high degree of reproducibility, robustness and sensitivity, the technique can be utilized to detect even trace amounts of bioactive substances in heterogeneous matrices such as fermentation broths or crude organic extracts. This research is thus relevant for a large number of researchers working in natural product discovery. Applications of this novel NMR-based approach include suitable environmental triggers for the induction of biosynthetic machineries. The author demonstrates the extraordinary value of this approach by the successful isolation of two potent inhibitors of the pharmaceutically relevant proteasome core particle from the insect pathogen photorhabdus luminescens. This thesis has led to a number of publications in high-impact journals.

Table of Contents

Frontmatter

Chapter 1. Introduction

Abstract
The ubiquitin-proteasome system (UPS) is responsible for the directed disposal of unfolded, misfolded and short-lived proteins in eukaryotic cells and is therefore a key player in protein homeostasis. Moreover, it participates in crucial biological pathways by the degradation of signaling factors such as cyclins or the tumor suppressor p53.
Martin Lorenz Stein

Chapter 2. Objective

Abstract
Due to the silencing of many natural toxins under common growth conditions, a robust and unambiguous technique is required to screen different fermentation approaches and identify the defined molecular trigger for the secretion of metabolites that affect biological maintenance.
Martin Lorenz Stein

Chapter 3. Materials and Methods

Abstract
All applied compounds were acquired from the following companies: Bachem (Bubendorf, SWI), Enzo Life Sciences (Lörrach, GER), Fluka (Neu-Ulm, GER), Merck (Darmstadt, GER), Santa Cruz (Heidelberg, GER), Sigma-Aldrich (Steinheim, GER), Roth (Karlsruhe, GER) and VWR (Darmstadt, GER).
Martin Lorenz Stein

Chapter 4. Results

Abstract
Initially, a suitable subunit-selective peptide sequence had to be established, which then served as a scaffold for the NMR-active substrate.
Martin Lorenz Stein

Chapter 5. Discussion

Abstract
The present thesis has led to the establishment of a new tool for the detection of proteasome inhibitors in highly heterogeneous matrices. Due to the NMR-based nature of the assay, it is not prone to common artefacts caused by quenching or autofluorescence that are responsible for the plenitude of false positive and equally negative results in high-throughput screenings conducted with UV-VIS assays.
Martin Lorenz Stein
Additional information