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21.
Aleksandra Dubiella-Jackowska Żaneta Polkowska Lech Dariusz Piotr Pasławski Wojciech Staszek Jacek Namieśnik 《Central European Journal of Chemistry》2009,7(1):35-41
A solid phase extraction technique for the determination of platinum(IV) at trace levels by inductively coupled plasma mass
spectromA solid phase extraction technique for the determination of platinum(IV) at trace levels by inductively coupled plasma
mass spectrometry (ICP-MS) was developed. The method was based on retention of platinum in a sample on silica gel modified
with aminepropyl groups. The retention of platinum(IV) from the sample solution and the recovery of platinum with 1.0 mol
L−1 thiourea solution were quantitative. The relative standard deviation (RSD) was calculated as 5% (n = 7) at the 10 ng L−1 level. The enrichment factor was found to be (50-fold) for 250 mL of water sample. Under optimum conditions, the method detection
limit (MDL) was found to be 1 ng L−1 for platinum in water matrices. Recoveries of Pt from spike addition to atmospheric water samples were quantitative (80–95%).
The present method was used for the determination of platinum in precipitation, throughfall and runoff water samples.
相似文献
22.
Leszek Pazderski Tomasz Pawlak Jerzy Sitkowski Lech Kozerski Edward Szłyk 《Magnetic resonance in chemistry : MRC》2010,48(6):450-457
1H, 13C and 15N NMR studies of iron(II), ruthenium(II) and osmium(II) tris‐chelated cationic complexes with 2,2′‐bipyridine and 1,10‐phenanthroline of the general formula [M(LL)3]2+ (M = Fe, Ru, Os; LL = bpy, phen) were performed. Inconsistent literature 1H signal assignments were corrected. Significant shielding of nitrogen‐adjacent protons [H(6) in bpy, H(2) in phen] and metal‐bonded nitrogens was observed, being enhanced in the series Ru(II) → Os(II) → Fe(II) for 1H, Fe(II) → Ru(II) → Os(II) for 15N and bpy → phen for both nuclei. The carbons are deshielded, the effect increasing in the order Ru(II) → Os(II) → Fe(II). Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
23.
Karolina Hyz Robert Kawȩcki Elżbieta Bednarek Wojciech Bocian Jerzy Sitkowski Lech Kozerski 《Magnetic resonance in chemistry : MRC》2010,48(8):575-584
Topotecan (TPT) is in clinical use as an antitumor agent, hycamtin?. Because of this, it requires both biologically and chemically useful information to be available. TPT acts by binding to the covalent complex formed by nicked DNA and topoisomerase I. This has a poisonous effect since inserted into the single‐strand nick and TPT inhibits its religation. We used NMR to trace TPT dynamics, tautomerism and solvolysis products in various solvents and conditions. Chemical stability was assessed in methanol and DMSO as compared to water, and the regioselectivity of the N‐ and O‐methylation was studied using various alkylating agents. The reaction products of quaternization of the nitrogen atom and methylation of the oxygen atom were characterized by means of ESI MS, 1H/13C‐HMBC and ‐HSQCAD NMR. We have focused on the NMR characterization of TPT with an anticipation that its aggregation, tumbling properties and the intramolecular dipolar interactions will be a common feature for other compounds described in this article. These features can also be useful in tracing the interactions of this class of topoisomerase I (TopoI) poisons with DNA. Moreover, the results explained shed light on the recently disclosed problem of lack of stability of TPT in the heart tissue homogenate samples using the analytical assays developed for this class of compounds carried out in the presence of methanol. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
24.
Bocian W Kawecki R Bednarek E Sitkowski J Pietrzyk A Williamson MP Hansen PE Kozerski L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(22):5776-5787
The binding constants of camptothecin, topotecan and its lactone ring-opened carboxylate derivative to DNA octamers were measured by UV and NMR spectroscopy. The self-association of topotecan (TPT) was also measured. The carboxylate form of TPT binds in the same way as the lactone, but more weakly. Titration of TPT into d(GCGATCGC)2 shows a preferred location stacked onto the terminal G1 base. However, the intermolecular NOEs cannot be reconciled with a single conformation of the complex, and suggest a model of a limited number of conformations in fast exchange. MD calculations on four pairs of starting structures with TPT stacked onto the G1-C8 base pair in different orientations were therefore performed. The use of selected experimental "docking" restraints yielded ten MD trajectories covering a wide conformational space. From a combination of calculated free energies, NOEs and chemical shifts, some of the structures produced could be eliminated, and it is concluded that the data are consistent with two major families of conformations in fast exchange. One of these is the conformation found in a crystal of a TPT/DNA/topoisomerase I ternary complex [Proc. Natl. Acad. Sci. USA 2002, 99, 15 387-15 392]. 相似文献
25.
Kuberan B Beeler DL Lawrence R Lech M Rosenberg RD 《Journal of the American Chemical Society》2003,125(41):12424-12425
We have engineered a two-step enzymatic synthesis of Mitrin which is a more potent and homogeneous anticoagulant than the current animal-derived heparin. This engineered heparin may have advantages of being free from animal-derived pathogens and may also have reduced side effects such as heparin induced thrombocytopenia. This approach can also be extended to tailor heparin-based drugs with improved therapeutic characteristics to treat other disorders or infections in which heparin-like molecules play a major role. 相似文献
26.
Marcel Scheepstra Dr. Lidia Nieto Dr. Anna K. H. Hirsch Dr. Sascha Fuchs Dr. Seppe Leysen Chan Vinh Lam Leslie in het Panhuis Prof. Dr. Constant A. A. van Boeckel Dr. Hans Wienk Prof. Dr. Rolf Boelens Dr. Christian Ottmann Dr. Lech‐Gustav Milroy Prof. Dr. Luc Brunsveld 《Angewandte Chemie (International ed. in English)》2014,53(25):6443-6448
27.
Xianwen Lou Bas F. M. de Waal Lech‐Gustav Milroy Joost L. J. van Dongen 《Journal of mass spectrometry : JMS》2015,50(5):766-770
In matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI TOF MS), analyte signals can be substantially suppressed by other compounds in the sample. In this technical note, we describe a modified thin‐layer sample preparation method that significantly reduces the analyte suppression effect (ASE). In our method, analytes are deposited on top of the surface of matrix preloaded on the MALDI plate. To prevent embedding of analyte into the matrix crystals, the sample solution were prepared without matrix and efforts were taken not to re‐dissolve the preloaded matrix. The results with model mixtures of peptides, synthetic polymers and lipids show that detection of analyte ions, which were completely suppressed using the conventional dried‐droplet method, could be effectively recovered by using our method. Our findings suggest that the incorporation of analytes in the matrix crystals has an important contributory effect on ASE. By reducing ASE, our method should be useful for the direct MALDI MS analysis of multicomponent mixtures. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
28.
Dr. Lech‐Gustav Milroy Dr. Maria Bartel Dr. Morkos A. Henen Dr. Seppe Leysen Joris M. C. Adriaans Prof. Dr. Luc Brunsveld Dr. Isabelle Landrieu Dr. Christian Ottmann 《Angewandte Chemie (International ed. in English)》2015,54(52):15720-15724
The discovery of novel protein–protein interaction (PPI) modulators represents one of the great molecular challenges of the modern era. PPIs can be modulated by either inhibitor or stabilizer compounds, which target different though proximal regions of the protein interface. In principle, protein–stabilizer complexes can guide the design of PPI inhibitors (and vice versa). In the present work, we combine X‐ray crystallographic data from both stabilizer and inhibitor co‐crystal complexes of the adapter protein 14‐3‐3 to characterize, down to the atomic scale, inhibitors of the 14‐3‐3/Tau PPI, a potential drug target to treat Alzheimer’s disease. The most potent compound notably inhibited the binding of phosphorylated full‐length Tau to 14‐3‐3 according to NMR spectroscopy studies. Our work sets a precedent for the rational design of PPI inhibitors guided by PPI stabilizer–protein complexes while potentially enabling access to new synthetically tractable stabilizers of 14‐3‐3 and other PPIs. 相似文献
29.
30.
A series of tetrachloride platinum(IV) compounds of the general formulae PtCl4L2, where L = 1,2,4-triazolo[1,5-a]pyrimidine (tp) (1), 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp) (2), 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) (3) and 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) (4) have been prepared and characterized by thermal analysis, 1H, 13C, 15N, 195Pt NMR and IR spectroscopy. Spectral data suggest that the triazolopyrimidines act as a monodentate ligand via the nitrogen atom N(3). The preliminary assessments of antitumor properties of the four complexes were evaluated as in vitro antiproliferative activity against three cell lines: HL-60 human acute promyelocytic leukemia, SW707 rectal adenocarcinoma and HCV29T bladder cancer. PtCl4(dbtp)2 exhibits high cytotoxic activity against all human cell lines, whereas the other complexes are only moderately active. 相似文献