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101.
Katharina Root Yves Wittwer Konstantin Barylyuk Ulrike Anders Renato Zenobi 《Journal of the American Society for Mass Spectrometry》2017,28(9):1863-1875
Native ESI-MS is increasingly used for quantitative analysis of biomolecular interactions. In such analyses, peak intensity ratios measured in mass spectra are treated as abundance ratios of the respective molecules in solution. While signal intensities of similar-size analytes, such as a protein and its complex with a small molecule, can be directly compared, significant distortions of the peak ratio due to unequal signal response of analytes impede the application of this approach for large oligomeric biomolecular complexes. We use a model system based on concatenated maltose binding protein units (MBPn, n = 1, 2, 3) to systematically study the behavior of protein mixtures in ESI-MS. The MBP concatamers differ from each other only by their mass while the chemical composition and other properties remain identical. We used native ESI-MS to analyze model mixtures of MBP oligomers, including equimolar mixtures of two proteins, as well as binary mixtures containing different fractions of the individual components. Pronounced deviation from a linear dependence of the signal intensity with concentration was observed for all binary mixtures investigated. While equimolar mixtures showed linear signal dependence at low concentrations, distinct ion suppression was observed above 20 μM. We systematically studied factors that are most often used in the literature to explain the origin of suppression effects. Implications of this effect for quantifying protein–protein binding affinity by native ESI-MS are discussed in general and demonstrated for an example of an anti-MBP antibody with its ligand, MBP. 相似文献
102.
The flocculation between the rod-like biopolymer Schizophyllan and two types of colloidal particles (latex with diameter 40 nm and alumina with diameter 60 nm) has been investigated by means of fluorescence correlation spectroscopy (FCS). The concentration ratio of Schizophyllan/particle q was varied in the range 0.1 approximately 20. Under conditions of pH about 5.7, 1 mmol.L(-1) NaCl, and room temperature (22+/-0.5 degrees C), the particles are strongly charged (alumina particles positively charged, latex negatively), while Schizophyllan is neutral. We observed that Schizophyllan chains flocculate with both types of particles, which suggests that the charge neutralization does not play a decisive role in these interactions. The ratio of fluorescence intensity of one floc over that of one particle, Q(f)/Q(p), and the corresponding hydrodynamic radius (r(h)) of the flocs have been measured. For a Schizophyllan-latex system, Q(f)/Q(p) reached a maximum value of 5 for q=3 indicating that the flocs contained five particles on average. The corresponding value of r(h) was r(h)=455 nm. The flocculation kinetic of latex particles with Schizophyllan was too fast to be measurable by FCS. For the Schizophyllan-alumina system, Q(f)/Q(p) was stable at about 1 in the whole studied range of q but r(h) increased with q suggesting that many Schizophyllan chains are adsorbed on individual particles. The flocculation kinetic of this system was studied by FCS and the obtained results were compatible with those of photon correlation spectroscopy. 相似文献
103.
Konstantin Karaghiosoff Thomas M. Klaptke Alexej Michailovski Gerhard Holl 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(9):o580-o581
The title compound (systematic name: 4,10‐dinitro‐2,6,8,12‐tetraoxa‐4,10‐diazatetracyclo[5.5.0.03,11.05,9]dodecane), C6H6N4O8, exhibits the highest density among known N‐nitramines, due to its close‐packed crystal structure. It may be regarded as consisting of a distorted hexagonal close‐packed lattice formed by the isowurtzitane cages, with the nitro groups occupying the free space between the cages. 相似文献
104.
Marcos A. Kettner Prof. Dr. Konstantin Karaghiosoff Prof. Dr. Thomas M. Klapötke Dr. Muhamed Sućeska Swetlana Wunder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(25):7622-7631
Here we report on the preparation of two hydrogen atom free 3,3′‐bi(1,2,4‐oxadiazole) derivatives. 5,5′‐Bis(fluorodinitromethyl)‐3,3′‐bi(1,2,4‐oxadiazole) was synthesised by fluorination of diammonium 5,5′‐bis(dinitromethanide)‐3,3′‐bi(1,2,4‐oxadiazole). For our previously reported analogue 5,5′‐bis(trinitromethyl)‐3,3′‐bi(1,2,4‐oxadiazole), a new synthetic route starting from new 3,3′‐bi(1,2,4‐oxadiazolyl)‐5,5′‐diacetic acid was developed. In this course also hitherto unknown 5,5′‐dimethyl‐3,3′‐bi(1,2,4‐oxadiazole) was isolated. The compounds were characterised by multinuclear NMR spectroscopy, IR and Raman spectroscopy, elemental analysis as well as mass spectrometry. X‐ray diffraction studies were performed and the crystal structures for the 5,5'‐dimethyl and 5,5'‐(fluorodinitromethyl) derivatives are reported. The energetic 5,5'‐(fluorodinitromethyl) and 5,5'‐(trinitromethyl) compounds do not contain any hydrogen atoms and show remarkable high densities. Furthermore, the thermal stabilities and sensitivities were determined by differential scanning calorimetry (DSC) and standardised impact and friction tests. The heats of formation were calculated by the atomisation method based on CBS‐4M enthalpies. With these values and the room‐temperature X‐ray densities, several detonation and propulsion parameters, such as the detonation velocity and pressure as well as the specific impulse of mixtures with aluminium, were computed using the EXPLO5 code. 相似文献
105.
Bis[N,N′‐diisopropylbenzamidinato(−)]silicon(II): Lewis Acid/Base Reactions with Triorganylboranes 下载免费PDF全文
Konstantin Junold Johannes A. Baus Dr. Christian Burschka Dr. Célia Fonseca Guerra Prof. Dr. F. Matthias Bickelhaupt Prof. Dr. Reinhold Tacke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12411-12415
Reaction of the donor‐stabilized silylene 1 (which is three‐coordinate in the solid state and four‐coordinate in solution) with BEt3 and BPh3 leads to the formation of the Lewis acid/base complexes 2 and 3 , respectively, which are the first five‐coordinate silicon compounds with an Si?B bond. These compounds were structurally characterized by crystal structure analyses and by multinuclear NMR spectroscopic studies in the solid state and in solution. Additionally, the bonding situation in 2 and 3 was analyzed by quantum chemical studies. 相似文献
106.
The fundamental aspects of charging in electrospray ionization (ESI) are hotly debated. In the present study, ESI charging of DNA oligonucleotides was explored in both positive (ESI+) and negative (ESI?) polarity using mass spectrometry detection. Single‐stranded 12‐mer CCCCAATTCCCC in buffer solution (aqueous NH4Ac, 100 mM) produced similar charge state distribution (CSD) in either ESI+ or ESI?. Similarity of CSD in ESI+ and ESI? was also observed for the double‐stranded 12‐mer CGCGAATTCGCG. By adding typical low‐vapor reagents (e.g. m‐nitro benzyl alcohol, m‐NBA; sulfolane) into the same buffer solution (<0.5% w/v), both CCCCAATTCCCC and CGCGAATTCGCG revealed strong supercharging (SC) effect in ESI?, while very little or no SC effect was observed in ESI+. With either sulfolane or m‐NBA, the CGCGAATTCGCG duplex dissociated into single strands in ESI?. No SC was observed in both ESI+ and ESI? for thermally denatured CGCGAATTCGCG duplex in NH4Ac buffer without the reagents. These findings are difficult to reconcile with the earlier model, which attributes SC in aqueous buffer solution to the conformational changes of analytes. Our observations suggest that the ionic strength of ESI droplets strongly affects the CSD of biopolymers such as DNA oligonucleotides and that SC effect is related to the depletion of ionic strength during the ESI process. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
107.
Stefanie Schönberger Christoph Jagdhuber Laura Ascherl Camilla Evangelisti Thomas M. Klapötke Konstantin Karaghiosoff 《无机化学与普通化学杂志》2014,640(1):68-75
A great number of binary neutral phosphorus sulfides was discovered and investigated. However all stable representatives of this family of compounds adopt a polycyclic structure in contrast to their lighter homologues, the nitrogen oxides. Acyclic representatives can be stabilized by adduct formation with a nitrogen base. The bis(pyridine) adduct py2P2S5 of the unstable acyclic phosphorus sulfide P2S5 is readily obtained stirring P4S10 in pyridine at ambient temperature. X‐ray diffraction studies on single crystals of py2P2S5 · 0.5 py ( 1b ) show a N2O5 like structure for the P2S5 framework. The long P–N distances of 1.86 Å indicate only weak coordination of the pyridine molecules to phosphorus. Single crystal X‐ray diffraction studies on py2P2S4.34O0.66 ( 2 ) reveal the presence of py2P2S4O ( 3 ) together with py2P2S5 in the crystal. Compound 3 contains the mixed phosphorus oxide sulfide molecule P2S4O stabilized as bis(pyridine) adduct. It is readily obtained from pyP2S5 by oxidation with KMnO4 in pyridine. The oxygen atom occupies the bridging position between the two phosphorus atoms. Quantum chemical calculations at the MPW1PW91 level of theory as well as DTA/TG thermal analyses confirm the weak coordination of the pyridine molecules in py2P2S5, py2P2S4O, and py2P2S7 to phosphorus. 相似文献
108.
The 1:1 and 2:1 complexes between water and trans- and cis-isomers of nitrous acid have been isolated in argon matrices and studied using FTIR spectroscopy and DFT(B3LYP) calculations with a 6-311++G(2d,2p) basis set. The analysis of the experimental spectra indicate that 1:1 complexes trapped in solid argon involve very strong hydrogen bond in which acid acts as the proton donor and water as the proton acceptor. The perturbed OH stretches are −248, −228 cm−1 red shifted from their free-molecules values in complexes formed by trans- and cis-HONO isomers, respectively. The calculated spectral parameters for the two complexes are in good agreement with experimental data. The calculations also predict stability of two more 1:1 weakly bound complexes formed by each isomer. In these the water acts as the proton donor and one of the two oxygen atoms of the acid as the acceptor. The experimental spectra demonstrate also formation of 2:1 complex between water and trans-HONO isomer in an argon matrix. The performed calculations indicate that the complex involves a seven-membered ring in which OH group of HONO forms very strong hydrogen bond with the oxygen atom of one water molecule and nitrogen atom acts as a weak proton acceptor for the hydrogen atom of the second water molecule of the water dimer. The observed perturbations of the OH stretch of trans-HONO (750 cm−1 red shift) is much larger than that predicted by calculations (556 cm−1 red shift); this difference is attributed to strong solvation effect of argon matrix on very strong hydrogen bond. 相似文献
109.
110.
Konstantin Iakoubovskii 《Central European Journal of Physics》2009,7(4):645-653
This paper reviews major techniques of aligning carbon nanotubes, either during the growth or by the post-growth processing.
A number of post-processing alignment techniques are discussed, which employ mechanical stretching, fracture, compression,
friction, filtration, fiber drawing, gas flow, liquid crystals, Langmuir-Blodgett technique, acoustic, magnetic and electric
fields. The suitability of those techniques to industrial applications is analyzed.
相似文献