@article{FuehrerSchlaad2014, author = {Fuehrer, Felix N. and Schlaad, Helmut}, title = {ADMET polymerization of amino-acid-based diene}, series = {Macromolecular chemistry and physics}, volume = {215}, journal = {Macromolecular chemistry and physics}, number = {22}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1352}, doi = {10.1002/macp.201400166}, pages = {2268 -- 2273}, year = {2014}, abstract = {1,4-Di(homo)allyl-2,5-diketopiperazines are synthesized and polymerized via ADMET using the Hoveyda-Grubbs 2nd generation catalyst. The but-3-enylated diketopiperazine can be converted into unsaturated tertiary polyamide with molar mass of <3000 g mol(-1), whereas the allylated diketopiperazine cannot. Double-bond isomerization occurs regardless of whether or not benzoquinone is present. A polyesteramide with a higher molar mass of ca. 4800 g mol(-1) is obtained by the alternating copolymerization (ALTMET) of 1,4-di(but-3-enyl)-2,5-di ketopiperazine and ethylene glycol diacrylate. A post-polymerization modification of the poly(ester)amides via radical thiol-ene chemistry, however, fails.}, language = {en} } @phdthesis{Fritz2006, author = {Fritz, Christina}, title = {Der Einfluß des prim{\"a}ren Stickstoffstoffwechsels auf den Aminos{\"a}ure- und Sekund{\"a}rstoffwechsel in Nicotiana tabacum L.}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13322}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {Es ist bekannt, dass {\"A}nderungen im Kohlenstoff- bzw. Stickstoffstaus der Pflanzen zu einer parallelen statt reziproken {\"A}nderung der kohlenstoff- und stickstoffhaltigen Prim{\"a}rmetabolite f{\"u}hren. Unter diesem Gesichtspunkt wurden in der vorliegenden Arbeit der Aminos{\"a}urestoffwechsel und der Sekund{\"a}rstoffwechsel unter reduzierten Stickstoffbedingungen untersucht. Zur Beeinflussung des Stickstoffstoffwechsels wurden nitratmangelern{\"a}hrte Tabakwildtyppflanzen und Genotypen mit unterschiedlich stark reduzierter Nitratreduktase-Aktivit{\"a}t verwendet. Dieses experimentelle System erlaubt zus{\"a}tzlich durch den Vergleich Nitrat defizienter Wildtyppflanzen mit Nitrat akkumulierenden NIA-Transformanten Prozesse zu identifizieren, die durch Nitrat gesteuert werden. Die Analysen der Prim{\"a}r- und Sekund{\"a}rmetabolite wurde in allen Genotypen diurnal durchgef{\"u}hrt, um auch tageszeitlich abh{\"a}ngige Prozesse zu identifizieren. Die Analyse der absoluten Gehalte aller individuellen Aminos{\"a}uren enth{\"u}llte bei den meisten erstaunlich stabile diurnale Muster mit einem Anstieg w{\"a}hrend des Tages und einem Abfall in der Nacht in Wildtyppflanzen gewachsen mit ausreichend Nitrat. Dieses Ergebnis legt die Schlussfolgerung nahe, dass die Biosynthese der Aminos{\"a}uren koordiniert abl{\"a}uft. In Pflanzen mit reduziertem Stickstoffstatus haben diese diurnalen Muster jedoch keinen Bestand. Die Kombination des erzeugten stickstoffbasierten Aminos{\"a}uredatensatz in Kombination mit einem bereits erzeugten Aminos{\"a}uredatensatz unter kohlenstofflimitierten Bedingungen von Matt et al. (2002) f{\"u}hrte durch Hauptkomponentenanalyse (PCA) und Korrelationsanalyse zu dem Ergebnis, dass die Hypothese nach einer koordinierten Aminos{\"a}urebiosynthese nicht allgemeine G{\"u}ltigkeit hat. Die PCA identifizierte Glutamin, Glutamat, Aspartat, Glycin, Pheny-lalanin und Threonin als Faktoren, die den Datens{\"a}tzen ihre charakteristische Eigenschaft und deren Varianz verleihen. Die Korrelationsanalyse zeigte, dass die sehr guten Korrelationen der individuellen Aminos{\"a}uren untereinander in reduzierten Stickstoff- und Kohlenstoffbedingungen sich verschlechtern. Das Verh{\"a}ltnis einer einzelnen Aminos{\"a}ure relativ zu den anderen f{\"u}hrte zur Identifizierung einiger Aminos{\"a}uren, die individuelle Antworten auf Stickstoff- und/oder Kohlenstoffstatus zeigen, und/oder speziell auf Nitrat, Licht und/oder den E-nergiestatus der Thylakoidmembran. Glutamat beispielsweise verh{\"a}lt sich in den meisten Situationen stabil, Phenylalanin dagegen zeigt in jeder physiologischen Situation eine individuelle Antwort. Die Ergebnisse dieser Arbeit f{\"u}hren zu einer Erweiterung der Hypothese einer koordinierten Synthese der Aminos{\"a}uren dahingehend, dass diese nicht generell f{\"u}r alle Aminos{\"a}uren angenommen werden kann. Es gibt einige Aminos{\"a}uren deren, Anteile sich situationsbedingt anpassen. Die Reduktion des Stickstoffstatus in nitratmangelern{\"a}hrten Tabakwildtyppflanzen f{\"u}hrte zu der, nach der „Carbon-Nutrient-Balance" Hypothese erwarteten Verlagerung der kohlenstoffreichen Phenylpropanoide und des stickstoffreichen Nikotins. Die Erh{\"o}hung der Phenylpropanoidgehalte war nicht in der Nitrat akkumulierenden NIA-Transformante zu beobachten und somit konnte Nitrat als regulatorisches Element identifiziert werden. Ein Einfluss der Vorl{\"a}ufermetabolite konnte ausgeschlossen werden, da sowohl nitratmangelern{\"a}hrter Wildtyp als auch die Nitrat akkumulierende NIA-Transformante {\"a}hnliche Gehalte dieser aufwiesen. Genexpressionsanalysen {\"u}ber Mikroarray-Hybridisierung und quantitative RT-PCR zeigten, dass Nitrat durch noch nicht gekl{\"a}rte Mechanismen Einfluss auf die Expression einiger Gene nimmt, die dem Phenylpropanoidstoffwechsels zugeordnet sind. Aus der Arbeit hervorgegangene Ver{\"o}ffentlichungen: Christina Fritz, Natalia Palacios-Rojas, Regina Feil und Mark Stitt (2006) Regulation of Secondary Metabolism by the Carbon-Nitrogen Status in Tobacco: Nitrate Inhibits Large Sectors of Phenylpropanoid Metabolism. Plant Journal 46, 533 - 548 Christina Fritz, Petra Matt, Cathrin M{\"u}ller, Regina Feil und Mark Stitt (2006) Impact of the Carbon-Nitrogen Status on the Amino Acid Profile in Tobacco Source Leaves. Plant, Cell and Environment 29 (11), 2009 - 2111}, language = {de} } @article{ShiXieQietal.2019, author = {Shi, Jiang and Xie, Dongchao and Qi, Dandan and Peng, Qunhua and Chen, Zongmao and Schreiner, Monika and Lin, Zhi and Baldermann, Susanne}, title = {Methyl jasmonate-induced changes of flavor profiles during the processing of Green, Oolong, and Black Tea}, series = {Frontiers in plant science}, volume = {10}, journal = {Frontiers in plant science}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {1664-462X}, doi = {10.3389/fpls.2019.00781}, pages = {13}, year = {2019}, abstract = {Tea aroma is one of the most important factors affecting the character and quality of tea. Here we describe the practical application of methyl jasmonate (MeJA) to improve the aroma quality of teas. The changes of selected metabolites during crucial tea processing steps, namely, withering, fixing and rolling, and fermentation, were analyzed. MeJA treatment of tea leaves (12, 24, 48, and 168 h) greatly promotes the aroma quality of green, oolong, and black tea products when comparing with untreated ones (0 h) and as confirmed by sensory evaluation. MeJA modulates the aroma profiles before, during, and after processing. Benzyl alcohol, benzaldehyde, 2-phenylethyl alcohol, phenylacetaldehyde, and trans-2-hexenal increased 1.07- to 3-fold in MeJA-treated fresh leaves and the first two maintained at a higher level in black tea and the last two in green tea. This correlates with a decrease in aromatic amino acids by more than twofold indicating a direct relation to tryptophan- and phenylalanine-derived volatiles. MeJA-treated oolong tea was characterized by a more pleasant aroma. Especially the terpenoids linalool and oxides, geraniol, and carvenol increased by more than twofold.}, language = {en} } @phdthesis{Behrendt2018, author = {Behrendt, Felix Nicolas}, title = {New bio-based polymers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-418316}, school = {Universit{\"a}t Potsdam}, pages = {vii, 153}, year = {2018}, abstract = {Redox-responsive polymers, such as poly(disulfide)s, are a versatile class of polymers with potential applications including gene- and drug-carrier systems. Their degradability under reductive conditions allows for a controlled response to the different redox states that are present throughout the body. Poly(disulfide)s are typically synthesized by step growth polymerizations. Step growth polymerizations, however, may suffer from low conversions and therefore low molar masses, limiting potential applications. The purpose of this thesis was therefore to find and investigate new synthetic routes towards the synthesis of amino acid-based poly(disulfide)s. The different routes in this thesis include entropy-driven ring opening polymerizations of novel macrocyclic monomers, derived from cystine derivatives. These monomers were obtained with overall yields of up to 77\% and were analyzed by mass spectrometry as well as by 1D and 2D NMR spectroscopy. The kinetics of the entropy-driven ring-opening metathesis polymerization (ED-ROMP) were thoroughly investigated in dependence of temperature, monomer concentration, and catalyst concentration. The polymerization was optimized to yield poly(disulfide)s with weight average molar masses of up to 80 kDa and conversions of ~80\%, at the thermodynamic equilibrium. Additionally, an alternative metal free polymerization, namely the entropy-driven ring-opening disulfide metathesis polymerization (ED-RODiMP) was established for the polymerization of the macrocyclic monomers. The effect of different solvents, concentrations and catalyst loadings on the polymerization process and its kinetics were studied. Polymers with very high weight average molar masses of up to 177 kDa were obtained. Moreover, various post-polymerization reactions were successfully performed. This work provides the first example of the homopolymerization of endo-cyclic disulfides by ED-ROMP and the first substantial study into the kinetics of the ED-RODiMP process.}, language = {en} } @article{LachmannMettlerAltmannWackeretal.2019, author = {Lachmann, Sabrina C. and Mettler-Altmann, Tabea and Wacker, Alexander and Spijkerman, Elly}, title = {Nitrate or ammonium}, series = {Ecology and evolution}, volume = {9}, journal = {Ecology and evolution}, number = {3}, publisher = {Wiley}, address = {Hoboken}, issn = {2045-7758}, doi = {10.1002/ece3.4790}, pages = {13}, year = {2019}, abstract = {In freshwaters, algal species are exposed to different inorganic nitrogen (Ni) sources whose incorporation varies in biochemical energy demand. We hypothesized that due to the lesser energy requirement of ammonium (NH4+)-use, in contrast to nitrate (NO3-)-use, more energy remains for other metabolic processes, especially under CO2-and phosphorus (Pi) limiting conditions. Therefore, we tested differences in cell characteristics of the green alga Chlamydomonas acidophila grown on NH4+ or NO3- under covariation of CO2 and Pi-supply in order to determine limitations, in a full-factorial design. As expected, results revealed higher carbon fixation rates for NH4+ grown cells compared to growth with NO3- under low CO2 conditions. NO3- -grown cells accumulated more of the nine analyzed amino acids, especially under Pi-limited conditions, compared to cells provided with NH4+. This is probably due to a slower protein synthesis in cells provided with NO3-. In contrast to our expectations, compared to NH4+ -grown cells NO3- -grown cells had higher photosynthetic efficiency under Pi-limitation. In conclusion, growth on the Ni-source NH4+ did not result in a clearly enhanced Ci-assimilation, as it was highly dependent on Pi and CO2 conditions (replete or limited). Results are potentially connected to the fact that C. acidophila is able to use only CO2 as its inorganic carbon (Ci) source.}, language = {en} } @article{HenningKochlikKuschetal.2022, author = {Henning, Thorsten and Kochlik, Bastian Max and Kusch, Paula and Strauss, Matthias and Juric, Viktorija and Pignitter, Marc and Marusch, Frank and Grune, Tilman and Weber, Daniela}, title = {Pre-Operative assessment of micronutrients, amino acids, phospholipids and oxidative stress in bariatric surgery candidates}, series = {Antioxidants : open access journal}, volume = {11}, journal = {Antioxidants : open access journal}, number = {4}, publisher = {MDPI}, address = {Basel}, issn = {2076-3921}, doi = {10.3390/antiox11040774}, pages = {13}, year = {2022}, abstract = {Obesity has been linked to lower concentrations of fat-soluble micronutrients and higher concentrations of oxidative stress markers as well as an altered metabolism of branched chain amino acids and phospholipids. In the context of morbid obesity, the aim of this study was to investigate whether and to which extent plasma status of micronutrients, amino acids, phospholipids and oxidative stress differs between morbidly obese (n = 23) and non-obese patients (n = 13). In addition to plasma, malondialdehyde, retinol, cholesterol and triglycerides were assessed in visceral and subcutaneous adipose tissue in both groups. Plasma gamma-tocopherol was significantly lower (p < 0.011) in the obese group while other fat-soluble micronutrients showed no statistically significant differences between both groups. Branched-chain amino acids (all p < 0.008) and lysine (p < 0.006) were significantly higher in morbidly obese patients compared to the control group. Malondialdehyde concentrations in both visceral (p < 0.016) and subcutaneous (p < 0.002) adipose tissue were significantly higher in the morbidly obese group while plasma markers of oxidative stress showed no significant differences between both groups. Significantly lower plasma concentrations of phosphatidylcholine, phosphatidylethanolamine, lyso-phosphatidylethanolamine (all p < 0.05) and their corresponding ether-linked analogs were observed, which were all reduced in obese participants compared to the control group. Pre-operative assessment of micronutrients in patients undergoing bariatric surgery is recommended for early identification of patients who might be at higher risk to develop a severe micronutrient deficiency post-surgery. Assessment of plasma BCAAs and phospholipids in obese patients might help to differentiate between metabolic healthy patients and those with metabolic disorders.}, language = {en} } @article{MeyerMainzKehretal.2017, author = {Meyer, Sabine and Mainz, Andi and Kehr, Jan-Christoph and Suessmuth, Roderich and Dittmann, Elke}, title = {Prerequisites of Isopeptide Bond Formation in Microcystin Biosynthesis}, series = {ChemBioChem : a European journal of chemical biology}, volume = {18}, journal = {ChemBioChem : a European journal of chemical biology}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4227}, doi = {10.1002/cbic.201700389}, pages = {2376 -- 2379}, year = {2017}, abstract = {The biosynthesis of the potent cyanobacterial hepatotoxin microcystin involves isopeptide bond formation through the carboxylic acid side chains of d-glutamate and -methyl d-aspartate. Analysis of the in vitro activation profiles of the two corresponding adenylation domains, McyE-A and McyB-A(2), either in a didomain or a tridomain context with the cognate thiolation domain and the upstream condensation domain revealed that substrate activation of both domains strictly depended on the presence of the condensation domains. We further identified two key amino acids in the binding pockets of both adenylation domains that could serve as a bioinformatic signature of isopeptide bond-forming modules incorporating d-glutamate or d-aspartate. Our findings further contribute to the understanding of the multifaceted role of condensation domains in nonribosomal peptide synthetase assembly lines.}, language = {en} }