排序方式: 共有88条查询结果,搜索用时 390 毫秒
61.
Dr. Matthew R. Aronoff Dr. Jasmine Egli Adeline Schmitt Prof. Helma Wennemers 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(22):5070-5074
Cγ-substituted proline derivatives are valuable tools for developing functionalized collagen peptides for biological and materials investigations, yet the stereochemistry at Cγ can produce undesired steric or stereoelectronic constraints. Alkylated γ-azaproline (γ-azPro) derivatives are proline mimetics that lack a stereogenic center at the γ-position of the ring and can thus utilize the invertibility of nitrogen to adapt their conformation. NMR spectroscopic analyses and DFT calculations highlighted how alkylated γ-azPro derivatives are conformationally dynamic and adopt conformational preferences through ring pucker flip along with nitrogen inversion. Lastly, incorporation of alkylated γ-azPro into collagen peptides produced functionalized pH-responsive triple helices with similar thermal stabilities, regardless of their placement in the Xaa or Yaa position within the characteristic Xaa-Yaa-Gly repeating unit of collagen peptides. 相似文献
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Mao Li Robert Puschmann Andreas Herdlitschka Dorothea Fiedler Helma Wennemers 《Angewandte Chemie (International ed. in English)》2020,59(36):15586-15589
Inositol hexakisphosphate (InsP6) is a central member of the inositol phosphate messengers in eukaryotic cells. Tools to manipulate the level of InsP6, particularly with compartment selectivity, are needed to enable functional cellular studies. We present cationic octa‐(4S)guanidiniumproline ( Z8 ) for the delivery of InsP6 into the cell nucleus. CD spectroscopy, binding affinity, dynamic light scattering, and computational studies revealed that Z8 binds tightly to InsP6 and upon binding undergoes a conformational change from a PPII‐helical structure to a structure that forms aggregates. The unique conformational features of the cationic oligoproline enable complex formation and cellular delivery of InsP6 with considerably greater efficacy than the flexible counterpart octaarginine. 相似文献
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Helma GladdinesMarcel van de Vel 《Topology and its Applications》2011,158(3):424-431
The disconnection number d(X) is the least number of points in a connected topological graph X such that removal of d(X) points will disconnect X (Nadler, 1993 [6]). Let Dn denote the set of all homeomorphism classes of topological graphs with disconnection number n. The main result characterizes the members of Dn+1 in terms of four possible operations on members of Dn. In addition, if X and Y are topological graphs and X is a subspace of Y with no endpoints, then d(X)?d(Y) and Y obtains from X with exactly d(Y)−d(X) operations. Some upper and lower bounds on the size of Dn are discussed.The algorithm of the main result has been implemented to construct the classes Dn for n?8, to estimate the size of D9, and to obtain information on certain subclasses such as non-planar graphs (n?9) and regular graphs (n?10). 相似文献
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Antimicrobial Poly(2‐methyloxazoline)s with Bioswitchable Activity through Satellite Group Modification 下载免费PDF全文
Dipl.‐Ing. Christian Krumm Dipl.‐Chem. Simon Harmuth Montasser Hijazi Britta Neugebauer Anne‐Larissa Kampmann Helma Geltenpoth Prof. Dr. Albert Sickmann Prof. Dr. Joerg C. Tiller 《Angewandte Chemie (International ed. in English)》2014,53(15):3830-3834
Biocides are widely used for preventing the spread of microbial infections and fouling of materials. Since their use can build up microbial resistance and cause unpredictable long‐term environmental problems, new biocidal agents are required. In this study, we demonstrate a concept in which an antimicrobial polymer is deactivated by the cleavage of a single group. Following the satellite group approach, a biocidal quaternary ammonium group was linked through a poly(2‐methyloxazoline) to an ester satellite group. The polymer with an octyl‐3‐propionoate satellite group shows very good antimicrobial activity against Gram‐positive bacterial strains. The biocidal polymer was also found to have low hemotoxicity, resulting in a high HC50/MIC value of 120 for S. aureus. Cleaving the ester satellite group resulted in a 30‐fold decrease in antimicrobial activity, proving the concept valid. The satellite group could also be cleaved by lipase showing that the antimicrobial activity of the new biocidal polymers is indeed bioswitchable. 相似文献
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Luca Garbuio Dr. Bartosz Lewandowski Patrick Wilhelm Ludmila Ziegler Dr. Maxim Yulikov Prof. Dr. Helma Wennemers Prof. Dr. Gunnar Jeschke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10747-10753
Oligoprolines are commonly used as molecular scaffolds. Past studies on the persistence length of their secondary structure, the polyproline II (PPII) helix, and on the fraction of backbone cis amide bonds have provided conflicting results. We resolved this debate by studying a series of spin‐labeled proline octadecamers with EPR spectroscopy. Distance distributions between an N‐terminal GdIII‐DOTA (DOTA=1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid) label and a nitroxide label at one of five evenly spaced backbone sites allowed us to discriminate between the flexibility of the PPII helix and the cis amide contributions. An upper limit of 2 % cis amide bonds per residue was found in a 7:3 (v/v) water/glycerol mixture, whereas cis amides were not observed in trifluoroethanol. Extrapolation of Monte Carlo models from the glass transition to ambient temperature predicts a persistence length of ≈3–3.5 nm in both solvents. The method is generally applicable to any type of oligomer for which the persistence length is of interest. 相似文献
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Dr. Carlotta Foletti Dr. Rolf A. Kramer Dr. Harald Mauser Prof. Dr. Urs Jenal Dr. Konrad H. Bleicher Prof. Dr. Helma Wennemers 《Angewandte Chemie (International ed. in English)》2018,57(26):7729-7733
c‐di‐GMP is an attractive target in the fight against bacterial infections since it is a near ubiquitous second messenger that regulates important cellular processes of pathogens, including biofilm formation and virulence. Screening of a combinatorial peptide library enabled the identification of the proline‐rich tetrapeptide Gup‐Gup‐Nap‐Arg, which binds c‐di‐GMP selectively over other nucleotides in water. Computational and CD spectroscopic studies provided a possible binding mode of the complex and enabled the design of a pentapeptide with even higher binding strength towards c‐di‐GMP. Biological studies showed that the tetrapeptide inhibits biofilm growth by the opportunistic pathogen P. aeruginosa. 相似文献
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Claudio E. Grünenfelder Dr. Jessica K. Kisunzu Prof. Dr. Helma Wennemers 《Angewandte Chemie (International ed. in English)》2016,55(30):8571-8574
The tripeptide H‐d Pro‐Pro‐Asn‐NH2 is presented as a catalyst for asymmetric conjugate addition reactions of aldehydes to maleimide. The peptidic catalyst promotes the reaction between various aldehydes and unprotected maleimide with high stereoselectivities and yields. The obtained products were readily derivatized to the corresponding pyrrolidines, lactams, lactones, and peptide‐like compounds. 1H NMR spectroscopic, crystallographic, and computational investigations provided insight into the conformational properties of H‐d Pro‐Pro‐Asn‐NH2 and revealed the importance of hydrogen bonding between the peptide and maleimide for catalyzing the stereoselective C?C bond formation. 相似文献
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Gong XY Dobrunz D Kümin M Wiesner M Revell JD Wennemers H Hauser PC 《Journal of separation science》2008,31(3):565-573
The separation and detection of small oligopeptides in CE with contactless conductivity detection were demonstrated. A strongly acidic separation buffer (0.5 M acetic acid) was employed in order to render the species cationic. Separation of the stereoisomers was achieved in typically 10-15 min by using either dimethyl-beta-CD (DM-beta-CD), (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18C(6)H(4)), a combination of the two substances, or of histidine, as buffer additives. Calibration curves were determined for isomers of Gly-Asp and H-Pro-Asp-NH(2), in the range of 0.05-0.5 mM and 0.1-1 mM, respectively, and were found to be linear. LODs were determined to be in the order of 1.0 microM. The determination of isomeric impurities down to about 1% was found possible. Species showing good separation could also be successfully determined on an electrophoretic lab-on-chip device, with analysis times of a few minutes. 相似文献