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151.
Markus Nachbar Sami El Deeb Mona Mozafari Hassan A. Alhazmi Lutz Preu Sabine Redweik Wolf Dieter Lehmann Hermann Wätzig 《Electrophoresis》2016,37(5-6):744-751
Strong, sequence‐specific gas‐phase bindings between proline‐rich peptides and alkaline earth metal ions in nanoESI‐MS experiments were reported by Lehmann et al. (Rapid Commun. Mass Spectrom. 2006, 20, 2404–2410), however its relevance for physiological‐like aqueous phase is uncertain. Therefore, the complexes should also be studied in aqueous solution and the relevance of the MS method for binding studies be evaluated. A mobility shift ACE method was used for determining the binding between the small peptide GAPAGPLIVPY and various metal ions in aqueous solution. The findings were compared to the MS results and further explained using computational methods. While the MS data showed a strong alkaline earth ion binding, the ACE results showed nonsignificant binding. The proposed vacuum state complex also decomposed during a molecular dynamic simulation in aqueous solution. This study shows that the formed stable peptide–metal ion adducts in the gas phase by ESI‐MS does not imply the existence of analogous adducts in the aqueous phase. Comparing peptide–metal ion interaction under the gaseous MS and aqueous ACE conditions showed huge difference in binding behavior. 相似文献
152.
Sumper M Hett R Lehmann G Wenzl S 《Angewandte Chemie (International ed. in English)》2007,46(44):8405-8408
153.
Hayes PY Lambert LK Lehmann R Penman K Kitching W De Voss JJ 《Magnetic resonance in chemistry : MRC》2007,45(11):1001-1005
Complete (1)H and (13)C spectral assignments for the four major steroidal saponins isolated by methanolic extraction of the roots of Dioscorea villosa, collected in North Carolina, United States (in summer and autumn), are presented in this paper. The structures were determined by a combination of (1)H, (13)C and 2D NMR techniques and were found to be ((3beta,25R)-26-(beta-D-glucopyranosyloxy)-22-methoxyfurost-5-en-3-yl-O-beta-D-glucopyranosyl-(1 --> 3)-O-beta-D-glucopyranosyl-(1 --> 4)-O-[alpha-L-rhamnopyranosyl-(1 --> 2)]-beta-D-glucopyranoside (1) (or methyl parvifloside), ((3beta,25R)-26-(beta-D-glucopyranosyloxy)-22 methoxyfurost-5-en-3-yl-O-alpha-L-rhamnopyranosyl-(1 --> 2)-O-[beta-D-gluco- pyranosyl-(1 --> 4)]-beta-D-glucopyranoside (2) (or methyl protodeltonin), (3beta,25R)-spirost-5-en-3-yl-O-beta-D-glucopy ranosyl-(1 --> 3)-O-beta-D-glucopyranosyl-(1 --> 4)-O-[alpha-L-rhamnopyranosyl-(1 --> 2)]-beta-D-glucopyranoside (3) (or Zingiberensis saponin I) and (3beta,25R)-spirost-5-en-3-yl-O-alpha-L-rhamnopyranosyl-(1 --> 2)-O-[beta-Ds-glucopyranosyl -(1 --> 4)]-beta-D-glucopyranoside (4) (or deltonin). 相似文献
154.
Ancilotto F Pi M Mayol R Barranco M Lehmann KK 《The journal of physical chemistry. A》2007,111(49):12695-12701
We have investigated, by means of density functional theory, the structure of a "scolium", that is, an electron circulating around a positively charged 4He nanodroplet, temporarily prevented from neutralization by the helium-electron repulsion. The positive ion core resides in the center of the nanodroplet where, as a consequence of electrostriction, a strong increase in the helium density with respect to its bulk value occurs. The electron enveloping the 4He cluster exerts an additional electrostatic pressure which further increases the local 4He density around the ion core. We argue that under such pressure, sufficiently small 4He nanodroplets may turn solid. The stability of a scolium with respect to electron-ion recombination is investigated. 相似文献
155.
The crystal structure of the low-temperature form of anhydrous caffeine has been determined by using X-ray powder-diffraction data with a combined simulated-annealing/Rietveld method. Anhydrous caffeine crystallizes with five crystallographically independent molecules in a monoclinic C-centred unit cell with dimensions of a=43.0390(17), b=15.0676(6) and c=6.95314(14) A and a beta angle of 99.027(2) degrees. 相似文献
156.
157.
Wolf D. Lehmann 《Journal of the American Society for Mass Spectrometry》1998,9(6):606-611
By using nanoelectrospray ionization and a triple quadrupole analyzer, simplified fragment ion spectra of peptides have been recorded by combining skimmer collision-induced dissociation with precursor ion scanning or neutral loss scanning. These pseudo-MS3 scan modes are characterized by two-stage collision-induced dissociation and have been termed sCID/precursor and sCID/neutral loss scan, respectively. By these scan modes, peptide fragment ion spectra can be generated that predominantly show signals of a single fragment ion series, such as the B or Y″ series. Skimmer collision-induced dissociation combined with scanning for neutral loss of 28 generates spectra showing B ions, whereas combination with precursor ion scanning for the Y″1 ion results in spectra showing Y″ ions for tryptic peptides (Y″1=m/z 147 for C-terminal lysine, Y″1=m/z 175 for C-terminal arginine). Sequence information including the direction of the sequence is easily extracted from the simplified fragment ion spectra generated by two-stage collision-induced dissociation, because the scan mode defines the type of fragments observed. The analytical results reported are similar to those that have been achieved in MS3 experiments using a hybrid BEQQ or a pentaquadrupole mass spectrometer (Schey, K. L.; Schwartz, J. C.; Cooks, R. G. Rapid Commun. Mass Spectrom. 1989, 3, 305–309). The pseudo-MS3 technique used in this study has some limitations with respect to sample purity, because there is no step of mass selection before the first stage of collisional activation; however, it has the advantage that a standard triple quadrupole instrumentation can be used. 相似文献
158.
159.
Gerhart Braunegg Anna de Raadt Sabine Feichtenhofer Herfried Griengl Irene Kopper Antje Lehmann Hans-Jorg Weber 《Angewandte Chemie (International ed. in English)》1999,38(18):2763-2766
A general principle for biohydroxylation , in which time-consuming screening and enrichment techniques are avoided, is demonstrated by the introduction of a docking/protecting group into the substrate. This facilitates acceptance by the microorganism and allows the use of a narrow range of microorganisms, for example Beauveria bassiana ATTC 7159 (B. b.), for the hydroxylation of compounds with diverse structures. After the biohydroxylation, the docking/protecting group is removed (see scheme). 相似文献
160.
Nicola Knetzger Viktoria Bachtin Susanne Lehmann Andreas Hensel Eva Liebau Fabian Herrmann 《Molecules (Basel, Switzerland)》2021,26(23)
In continuation of the search for new anthelmintic natural products, the study at hand investigated the nematicidal effects of the two naturally occurring quassinoids ailanthone and bruceine A against the reproductive system of the model nematode Caenorhabditis elegans to pinpoint their anthelmintic mode of action by the application of various microscopic techniques. Differential Interference Contrast (DIC) and the epifluorescence microscopy experiments used in the presented study indicated the genotoxic effects of the tested quassinoids (c ailanthone = 50 µM, c bruceine A = 100 µM) against the nuclei of the investigated gonadal and spermathecal tissues, leaving other morphological key features such as enterocytes or body wall muscle cells unimpaired. In order to gain nanoscopic insight into the morphology of the gonads as well as the considerably smaller spermathecae of C. elegans, an innovative protocol of polyethylene glycol embedding, ultra-sectioning, acridine orange staining, tissue identification by epifluorescence, and subsequent AFM-based ultrastructural data acquisition was applied. This sequence allowed the facile and fast assessment of the impact of quassinoid treatment not only on the gonadal but also on the considerably smaller spermathecal tissues of C. elegans. These first-time ultrastructural investigations on C. elegans gonads and spermathecae by AFM led to the identification of specific quassinoid-induced alterations to the nuclei of the reproductive tissues (e.g., highly condensed chromatin, impaired nuclear membrane morphology, as well as altered nucleolus morphology), altogether implying an apoptosis-like effect of ailanthone and bruceine A on the reproductive tissues of C. elegans. 相似文献