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11.
12.
Munch HK Heide ST Christensen NJ Hoeg-Jensen T Thulstrup PW Jensen KJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(26):7198-7204
Self-assembly of proteins mediated by metal ions is crucial in biological systems and a better understanding and novel strategies for its control are important. An abiotic metal ion ligand in a protein offers the prospect of control of the oligomeric state, if a selectivity over binding to the native side chains can be achieved. Insulin binds Zn(II) to form a hexamer, which is important for its storage in vivo and in drug formulations. We have re-engineered an insulin variant to control its self-assembly by covalent attachment of 2,2'-bipyridine. The use of Fe(II) provided chemoselective binding over the native site, forming a homotrimer in a reversible manner, which was easily followed by the characteristic color of the Fe(II) complex. This provided the first well-defined insulin trimer and the first insulin variant for which self-assembly can be followed visually. 相似文献
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W. Meysahn F. Löwe G. A. Shook R. C. Emmons J. C. Munch H. G. Fisk J. E. Verschaffelt R. Crombez und G. Kortiim 《Fresenius' Journal of Analytical Chemistry》1931,85(1-3):64-67
Ohne Zusammenfassung 相似文献
15.
The aqueous solution chemistry of niobium is rather unexplored, and well characterized aqua complexes are scarce. In this work, a new niobium aqua ion is obtained upon treatment of Zn-reduced ethanolic solutions of NbCl5 with HCl in the presence of a sulfide source. The red aqua ion, obtained upon cation-exchange chromatography, forms readily the thiocyanate complex which has been crystallized as Cs(4.26)Na(1.74)[Nb4SO5(NCS)10] . 0.33H2O. X-ray crystallography revealed an unprecedented metal-metal bonded tetranuclear Nb4(mu4-S)(mu2-O)5(4+) core with a capping mu4-S ligand. 相似文献
16.
A direct injection, liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been developed for the analysis of the chloro-s-triazine herbicides and their degradates in finished drinking water. The target compounds in the method were selected based on their inclusion in a common mechanism group (CMG) because of their ability to induce a similar toxic effect through a common mechanism of toxicity. The target list includes the chloro-s-triazines (atrazine, simazine, cyanazine, and propazine) and their dealkylated degradates (desethylatrazine, desisopropylatrazine, and diaminochlorotriazine). Potential matrix effects are minimized by the use of individual isotopically enriched internal standards. Analyte stability in finished chlorinated drinking water samples is ensured through careful selection of proper dechlorinating and antimicrobial reagents and through buffering sample pH. In the absence of proper dechlorination, the target analytes were found to degrade over a short period of time, even under refrigerated storage conditions. The final method has adequate sensitivity to accurately detect all target analytes at or below 0.1 microg/L and displays sufficient precision and robustness to warrant publication as EPA Method 536. 相似文献
17.
M. Bellour A. Knaebel J.P. Munch S.J. Candau 《The European physical journal. E, Soft matter》2000,3(2):111-121
Static and dynamic light scattering and conductivity experiments were carried out on salt-free aqueous micellar solutions
of cetyltrimethylammonium n-hexane sulfonate (CTAC_6SO_3) and cetyltrimethylammonium n-heptane sulfonate (CTAC_7SO_3) as a function of surfactant concentration. This study confirms the analogy between the behavior
in the semi-dilute regime of elongated micellar systems and “classical” polyelectrolyte solutions. Time-resolved scattering
experiments performed after a variation of concentration from about twice the overlap volume fraction to less than half of it revealed the existence of a structural relaxation with a characteristic time of several hours.
Received 21 December 1999 相似文献
18.
DC Muddiman AP Null JC Hannis 《Rapid communications in mass spectrometry : RCM》1999,13(12):1201-1204
Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) has been used to determine the mass of a double-stranded 500 base-pair (bp) polymerase chain reaction (PCR) product with an average theoretical mass of the blunt-ended (i.e. unadenylated) species of 308 859.35 Da. The PCR product was generated from the linearized bacteriophage Lambda genome which is a double-stranded template. Utilization of ethanol precipitation in tandem with a rapid microdialysis step to purify and desalt the PCR product was crucial to obtain a precise mass measurement. The PCR product (0.8 pmol/μL) was electrosprayed from a solution containing 75% acetonitrile, 25 mM piperidine, and 25 mM imidazole and was infused at a rate of 200 nL/min. The average molecular mass and the corresponding precision were determined using the charge-states ranging from 172 to 235 net negative charges. The experimental mass and corresponding precision (reported as the 95% confidence interval of the mean) was 309 406 +/- 27 Da (87 ppm). The mass accuracy was compromised due to the fact that the PCR generates multiple products when using Taq polymerase due to the non-template directed 3'-adenylation. This results in a mixture of three PCR products with nearly identical mass (i.e. blunt-ended, mono-adenylated and di-adenylated) with unknown relative abundances that were not resolved in the spectrum. Thus, the experimental mass will be a weighted average of the three species which, under our experimental conditions, reflects a nearly equal concentration of the mono- and di-adenylated species. This report demonstrates that precise mass measurements of PCR products up to 309 kDa (500 bp) can be routinely obtained by ESI-FTICR requiring low femtomole amounts. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
19.
Tetsuharu Narita Alexandra Knaebel Jean-Pierre Munch Miklós Zrínyi Sauveur Jean Candau 《Macromolecular Symposia》2004,207(1):17-30
The Brownian motion of probe particles in aqueous solutions of poly(vinyl alcohol)(PVA) and in chemically crosslinked PVA gels has been studied by diffusing-wave spectroscopy (DWS). At long time scales the measurements allow us to determine the effect of the crosslinking ratio on the macroscopic viscosity of sols and the shear modulus of gels. The local shear modulus of gels as obtained from the characteristic length of the Brownian cage was found to agree with that measured by classical rheometry and dynamic light scattering (DLS). These microrheological techniques were applied to two polymer gel systems. Substrate induced gradient structure of hydrogels was studied from a microrheological point of view using DLS. It is clearly seen that hydrophobic substrate induces weakly crosslinked network formation at the interface region up to a few millimeters as expected from other experimental facts. Magnetic particle motion in gels under external magnetic field was investigated by DWS. The translational motion of the magnetic particles in gels due to the alternating magnetic force can be detected and found to be superimposed on the relaxation due to the thermal motion. 相似文献
20.
Sakari Leino Patrick JC May Paavo Alku Lassi A Liikkanen Hannu Tiitinen 《BMC neuroscience》2007,8(1):78