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231.
Beyeh NK Weimann DP Kaufmann L Schalley CA Rissanen K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(18):5552-5557
The non-covalent interactions of different upper-rim-substituted C(2)-resorcinarenes with tetramethylammonium salts were analyzed in the gas phase in an Electrospray Ionization Fourier-transform ion-cyclotron-resonance (ESI-FTICR) mass spectrometer and by (1)H NMR titrations. The order of binding strengths of the hosts towards the tetramethylammonium cation in the gas phase reflects the electronic nature of the substituents on the upper rim of the resorcinarene. In solution, however, a different trend with particularly high binding constants for halogenated resorcinarenes has been observed. This trend can be explained by a synergetic effect originating from the interaction of the halogenated resorcinarenes with the counter anions through hydrogen bonding. This study highlights the importance of weak interactions in recognition processes and points out the benefits of comparing the gas-phase data with results obtained from solution experiments. 相似文献
232.
Behan RK Hoffart LM Stone KL Krebs C Green MT 《Journal of the American Chemical Society》2006,128(35):11471-11474
Using a combination of M?ssbauer spectroscopy and density functional calculations, we have determined that the ferryl forms of P450(BM3) and P450cam are protonated at physiological pH. Density functional calculations were performed on large active-site models of these enzymes to determine the theoretical M?ssbauer parameters for the ferryl and protonated ferryl (Fe(IV)OH) species. These calculations revealed a significant enlargement of the quadrupole splitting parameter upon protonation of the ferryl unit. The calculated quadrupole splittings for the protonated and unprotonated ferryl forms of P450(BM3) are DeltaE(Q) = 2.17 mm/s and DeltaE(Q) = 1.05 mm/s, respectively. For P450cam, they are DeltaE(Q) = 1.84 mm/s and DeltaE(Q) = 0.66 mm/s, respectively. The experimentally determined quadrupole splittings (P450(BM3), DeltaE(Q) = 2.16 mm/s; P450cam, DeltaE(Q) = 2.06 mm/s) are in good agreement with the values calculated for the protonated forms of the enzymes. Our results suggest that basic ferryls are a natural consequence of thiolate-ligated hemes. 相似文献
233.
Repo S Paldanius TA Hytönen VP Nyholm TK Halling KK Huuskonen J Pentikäinen OT Rissanen K Slotte JP Airenne TT Salminen TA Kulomaa MS Johnson MS 《Chemistry & biology》2006,13(10):1029-1039
The chicken genome encodes several biotin-binding proteins, including avidin and avidin-related protein 4 (AVR4). In addition to D-biotin, avidin binds an azo dye compound, 4-hydroxyazobenzene-2-carboxylic acid (HABA), but the HABA-binding properties of AVR4 are not yet known. Differential scanning calorimetry, UV/visible spectroscopy, and molecular modeling were used to analyze the binding of 15 azo molecules to avidin and AVR4. Significant differences are seen in azo compound preferences for the two proteins, emphasizing the importance of the loop between strands beta3 and beta4 for azo ligand recognition; information on these loops is provided by the high-resolution (1.5 A) X-ray structure for avidin reported here. These results may be valuable in designing improved tools for avidin-based life science and nanobiotechnology applications. 相似文献
234.
Zhiyan Song Kari J. Parker Idorenyin Enoh Hua Zhao Olarongbe Olubajo 《Magnetic resonance in chemistry : MRC》2010,48(2):123-128
Interaction of polyamines with nucleotides plays a key role in many biological processes. Here we use multiple NMR techniques to characterize interaction of spermidine with adenosine 5′‐triphosphate (ATP). Two‐dimensional 1H‐15N spectra obtained from gs‐HMBC experiments at varied pH show significant shift of N‐1 peak around pH 2.0–7.0 range, suggesting that spermidine binds to N‐1 site of ATP base. The binding facilitates N‐1 deprotonation, shifting its pKa from 4.3 to 3.4. By correlating 15N and 31P chemical shift data, it is clear that spermidine is capable of concurrently binding to ATP base and phosphate sites around pH 4.0–7.0. The self‐diffusion constants derived from 1H PFG‐diffusion measurements provide evidence that binding of spermidine to ATP is in 1:1 ratio, and pH variations do not induce significant nucleotide self‐association in our samples. 31P spectral analysis suggests that at neutral pH, Mg2+ ion competes with spermidine and shows stronger binding to ATP phosphates. From 31P kinetic measurements of myosin‐catalyzed ATP hydrolysis, it is found that binding of spermidine affects the stability and reactivity of ATP. These NMR results are important for advancing the studies on nucleotide–polyamine interaction and its impact on nucleotide structures and activities under varied conditions. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
235.
An axial, dynamic stiffness model of an arbitrary wide and long rubber bush mounting is developed within the audible-frequency range, where influences of audible frequencies, material properties, bush mounting length and radius, are investigated. The problems of simultaneously satisfying the locally non-mixed boundary conditions at the radial and end surfaces are solved by adopting a waveguide approach, using the dispersion relation for axially symmetric waves in thick-walled infinite plates, while satisfying the radial boundary conditions by mode matching. The rubber is assumed nearly incompressible, displaying dilatation elasticity and deviatoric viscoelasticity based on a fractional derivative, standard linear solid embodying a Mittag–Leffler relaxation kernel, the main advantage being the minimum parameter number required to successfully model wide-frequency band material properties. The stiffness is found to depend strongly on frequency, displaying acoustical resonance phenomena; such as stiffness peaks and troughs. The presented model agrees fully with a simplified, long-bush model while diverging from it for increased diameter-to-length ratios. To a great extent, the increased influences of higher order modes and dispersion explain the discrepancies reported for the approximate approach. 相似文献
236.
CoCl2 has been used as a mild and effective catalyst for regioselective ring opening of oxiranes with anilines to synthesize β-amino alcohols in good yields. 相似文献
237.
Antonio M. Peralta Ignacio Villanueva J.D. Maitland Wright Kari Ylinen 《Journal of Mathematical Analysis and Applications》2007,325(2):968-974
Let X be a Banach space. Then there is a locally convex topology for X, the “Right topology,” such that a linear map T, from X into a Banach space Y, is weakly compact, precisely when T is a continuous map from X, equipped with the “Right” topology, into Y equipped with the norm topology. When T is only sequentially continuous with respect to the Right topology, it is said to be pseudo weakly compact. This notion is related to Pelczynski's Property (V). 相似文献
238.
Jarmo Ropponen Tero Tuuttila Manu Lahtinen Sami Nummelin Kari Rissanen 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5574-5586
The syntheses and thermal and X‐ray powder diffraction analyses of three sets of aliphatic polyester dendrimers based on 2,2‐bis(hydroxymethyl)propionic acid as a repeating unit and 2,2‐dimethyl‐1,3‐propanediol, 1,5‐pentanediol, and 1,1,1‐tris(hydroxymethyl)ethane as core molecules are reported. These dendritic polyesters were prepared in high yields with the divergent method. The thermal properties of these biodendrimers were evaluated with thermogravimetric analysis and differential scanning calorimetry. The thermal decomposition of the compounds occurred around 250 °C for the hydroxyl‐ended dendrimers and around 150 °C for the acetonide‐protected dendrimers. In addition, the crystallinity of the lower generation dendrimers was evaluated with X‐ray powder diffraction. The highest crystallinity and the highest melting points were observed for the first‐generation dendritic compounds. The higher generation dendrimers showed weaker melting transitions during the first heating scan. Only the glass‐transition temperatures were observed in subsequent heating scans. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5574–5586, 2004 相似文献
239.
240.
Sannapaneni Janardan Pothini Suman G. Swapna A. Amrita R. Priya Ramamoorthy Siva Kari Vijayakrishna Akella Sivaramakrishna 《Applied biochemistry and biotechnology》2014,173(2):596-608
A group of hydrazide and semicarbazide derivatives containing isopropylidene, benzylidene, cyclohexylidene, and phospholidene groups was synthesized and characterized by spectroscopic techniques. These compounds were tested for DNA interaction studies monitored by UV-Vis and IR data as well as molecular docking. Investigations on interactions of these compounds with DNA revealed an intercalative mode of binding between them. It is interesting to note that semicarbazide derivatives with aliphatic substituents showed better DNA binding than the aromatic substituents. 相似文献