http://hdl.handle.net/10033/6819 AG Chemische Mikrobiologie (CMIK) Sat, 25 May 2013 16:25:10 GMT 2013-05-25T16:25:10Z http://hdl.handle.net/10033/243651 Title: Antimicrobial and biofilm inhibiting diketopiperazines. Authors: de Carvalho, M P; Abraham, W-R Abstract: Diketopiperazines are the smallest cyclic peptides known. 90% of Gram-negative bacteria produce diketopiperazines and they have also been isolated from Gram-positive bacteria, fungi and higher organisms. Biosynthesis of cyclodipeptides can be achieved by dedicated nonribosomal peptide synthetases or by a novel type of synthetases named cyclopeptide synthases. Since the first report in 1924 a large number of bioactive diketopiperazines was discovered spanning activities as antitumor, antiviral, antifungal, antibacterial, antiprion, antihyperglycemic or glycosidase inhibitor agents. As infections are of increasing concern for human health and resistances against existing antibiotics are growing this review focuses on the antimicrobial activities of diketopiperazines. The antibiotic bicyclomycin is a diketopiperazine and structure activity studies revealed the unique nature of this compound which was finally developed for clinical applications. The antimicrobial activities of a number of other diketopiperazines along with structure activity relationships are discussed. Here a special focus is on the activity-toxicity problem of many compounds setting tight limitations to their application as drugs. Not only these classical antimicrobial activities but also proposed action in modulating bacterial communication as a new target to control biofilms will be evaluated. Pathogens organized in biofilms are difficult to eradicate because of the increase of their tolerance for antibiotics for several orders. Diketopiperazines were reported to modulate LuxR-mediated quorum-sensing systems of bacteria, and they are considered to influence cell-cell signaling offering alternative ways of biofilm control by interfering with microbial communication. Concluding the review we will finally discuss the potential of diketopiperazines in the clinic to erase biofilm infections. Sun, 01 Jul 2012 00:00:00 GMT http://hdl.handle.net/10033/243651 2012-07-01T00:00:00Z http://hdl.handle.net/10033/232314 Title: Chemische Funktionalisierung und Materialoptimierung dentaler Implantat-Abutments zur Reduktion der oralen Biofilmbildung Authors: Stiesch, Meike; Menzel, Henning; Abraham, Wolf-Rainer; Müller, Peter Paul; Dempwolf, Wiebke; Pfaffenroth, Cornelia; Kohorst, Phillip; Winkel, Andreas Fri, 06 Jul 2012 00:00:00 GMT http://hdl.handle.net/10033/232314 2012-07-06T00:00:00Z http://hdl.handle.net/10033/214221 Title: Volatile sesquiterpenes from fungi: what are they good for? Authors: Kramer, Rolf; Abraham, Wolf-Rainer Mon, 05 Mar 2012 15:25:32 GMT http://hdl.handle.net/10033/214221 2012-03-05T15:25:32Z http://hdl.handle.net/10033/203609 Title: Adenosine in the inflamed gut: a Janus faced compound. Authors: Estrela, A B; Abraham, W-R Abstract: The purine ribonucleoside adenosine (Ado) has been recognized for its regulatory functions in situations of cellular stress like ischemia, hypoxia and inflammation. The importance of extracellular Ado as a modulator in the immune system is a theme of great appreciation and the focus of recent increasing interest in the field of gastrointestinal inflammation. In this review, the different aspects of Ado signaling during inflammatory responses in the gut are discussed, considering the contribution of the four known Ado receptors (ARs; A(1), A(2A), A(2B), and A(3)), their mechanisms and expression patterns. Activation of these receptors in epithelial cells as well as in immune cells recruited to the inflamed intestinal mucosa determines the overall effect, ranging from a protective, anti-inflammatory modulation to a strong pro-inflammatory induction. Here we present the current advances in agonists and antagonists development and their potential therapeutic application studied in animal models of intestinal inflammation. In addition, alternative complementary approaches to manipulate such a complex signaling system are discussed, for example, the use of AR allosteric modulators or interference with Ado metabolism. Special features of the gut environment are taken into account: the contribution of diet components; the involvement of Ado in intestinal infections; the interactions with the gut microbiome, particularly, the recent exciting finding that an intestinal bacterium can directly produce extracellular Ado in response to host defense mechanisms in an inflammation scenario. Understanding each component of this dynamic system will broaden the possibilities for applying Ado signaling as a therapeutic target in gut inflammation. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/10033/203609 2011-01-01T00:00:00Z