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21.
Graesser DT Wylie BJ Nieuwkoop AJ Franks WT Rienstra CM 《Magnetic resonance in chemistry : MRC》2007,45(Z1):S129-S134
We present a novel rotational-echo double resonance (REDOR) method for detection of multiple (19)F-(15)N distances in solid proteins. The method is applicable to protein samples containing a single (19)F label, in addition to high levels of (13)C and (15)N enrichment. REDOR dephasing pulses are applied on the (19)F channel during an indirect constant time chemical shift evolution period on (15)N, and polarization is then transferred to (13)C for detection, with high-power (1)H decoupling throughout the sequence. This four-channel experiment reports site-specifically on (19)F-(15)N distances, with highly accurate determinations of approximately 5 A distances and detection of correlations arising from internuclear distances of at least 8 A. We demonstrate the method on the well-characterized 56-residue model protein GB1, where the sole tryptophan residue (Trp-43) has been labeled with 5-(19)F-Trp, in a bacterial growth medium also including (13)C-glucose and (15)N ammonium chloride. In GB1, 11 distances are determined, all agreeing within 20% of the X-ray structure distances. We envision the experiment will be utilized to measure quantitative long-range distances for protein structure determination. 相似文献
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Thode AM Kim KH Blackwell SB Greene CR Nations CS McDonald TL Macrander AM 《The Journal of the Acoustical Society of America》2012,131(5):3726-3747
An automated procedure has been developed for detecting and localizing frequency-modulated bowhead whale sounds in the presence of seismic airgun surveys. The procedure was applied to four years of data, collected from over 30 directional autonomous recording packages deployed over a 280 km span of continental shelf in the Alaskan Beaufort Sea. The procedure has six sequential stages that begin by extracting 25-element feature vectors from spectrograms of potential call candidates. Two cascaded neural networks then classify some feature vectors as bowhead calls, and the procedure then matches calls between recorders to triangulate locations. To train the networks, manual analysts flagged 219 471 bowhead call examples from 2008 and 2009. Manual analyses were also used to identify 1.17 million transient signals that were not whale calls. The network output thresholds were adjusted to reject 20% of whale calls in the training data. Validation runs using 2007 and 2010 data found that the procedure missed 30%-40% of manually detected calls. Furthermore, 20%-40% of the sounds flagged as calls are not present in the manual analyses; however, these extra detections incorporate legitimate whale calls overlooked by human analysts. Both manual and automated methods produce similar spatial and temporal call distributions. 相似文献
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Tavan T Trent 《Journal of Functional Analysis》1985,64(2):163-177
It is shown that P2(μ) ≠ L2(μ) if and only if there exists a probability measure ν with ν ⊥ μ and 6pz.dfnc;1,ν ? Cz.dfnc;pz.dfnc;2,μ for all polynomials p and a fixed constant C < ∞. The relationship between this method and theorems of Berger and of Carey and Pincus concerning rationally cyclic vectors for powers of nonnormal subnormal Operators is examined. 相似文献
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J. William Helton Orlando Merino Trent E. Walker 《Integral Equations and Operator Theory》1995,22(4):420-439
This article gives necessary and sufficient conditions for local solutions to several very general constrained optimization problems over spaces of analytic functions.The results presented here have many applications, a particular instance of which is the sup-norm approximation of functions continuous on the unit circle in the complex plane by functions continuous on the circle and analytic on the open disk and whose Fourier coefficients satisfy prescribed linear relations.Also, the results in this article generalize Nevanlinna-Pick and Caratheodory-Fejer Interpolation results to allow values of arbitrary derivatives of functions to be assigned or merely bounded. Classically, NP and CF solve only problems with consecutive derivatives specified.In engineering, constraints on the Fourier coefficients of a frequency response function correspond to constraints on its time domain behavior. Indeed the central problems of control theory involve both time and frequency domain constraints. That is precisely what the results in this paper handle.Supported in part by the AFOSR and the NSF 相似文献
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Hin‐Koon Woo Eden P. Go Linh Hoang Sunia A. Trauger Benjamin Bowen Gary Siuzdak Trent R. Northen 《Rapid communications in mass spectrometry : RCM》2009,23(12):1849-1855
Mass spectrometry has become an indispensable tool for the global study of metabolites (metabolomics), primarily using electrospray ionization mass spectrometry (ESI‐MS). However, many important classes of molecules such as neutral lipids do not ionize well by ESI and go undetected. Chemical derivatization of metabolites can enhance ionization for increased sensitivity and metabolomic coverage. Here we describe the use of tris(2,4,6,‐trimethoxyphenyl)phosphonium acetic acid (TMPP‐AA) to improve liquid chromatography (LC)/ESI‐MS detection of hydroxylated metabolites (i.e. lipids) from serum extracts. Cholesterol which is not normally detected from serum using ESI is observed with attomole sensitivity. This approach was applied to identify four endogenous lipids (hexadecanoyl‐sn‐glycerol, dihydrotachysterol, octadecanol, and alpha‐tocopherol) from human serum. Overall, this approach extends the types of metabolites which can be detected using standard ESI‐MS instrumentation and demonstrates the potential for targeted metabolomics analysis. Published in 2009 by John Wiley & Sons, Ltd. 相似文献
28.
Piyush Deokar Dominik Leitz Trent H. Stein Monica Vasiliu Prof. Dr. David A. Dixon Prof. Dr. Karl O. Christe Prof. Dr. Ralf Haiges 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(37):13251-13257
The arsenic(III) and antimony(III) cyanides M(CN)3 (M=As, Sb) have been prepared in quantitative yields from the corresponding trifluorides through fluoride–cyanide exchange with Me3SiCN in acetonitrile. When the reaction was carried out in the presence of one equivalent of 2,2′‐bipyridine, the adducts [M(CN)3 ? (2,2′‐bipy)] were obtained. The crystal structures of As(CN)3, [As(CN)3 ? (2,2′‐bipy)] and [Sb(CN)3 ? (2,2′‐bipy)] were determined and are surprisingly different. As(CN)3 possesses a polymeric three‐dimensional structure, [As(CN)3 ? (2,2′‐bipy)] exhibits a two‐dimensional sheet structure, and [Sb(CN)3 ? (2,2′‐bipy)] has a chain structure, and none of the structures resembles those found for the corresponding arsenic and antimony triazides. 相似文献
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