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21.
B. K. Wagner P. E. Garrett Minfang Yeh S. W. Yates 《Journal of Radioanalytical and Nuclear Chemistry》1997,219(2):217-220
The first excited state of137Ba has been excited by the inelastic scattering of accelerator-produced neutrons. The energy of this state at 283.5 keV is not in agreement with the generally accepted value of 279.2 keV, but is in accord with other recent measurements. No evidence for a doublet of states near this energy is found. 相似文献
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Pierre Thureau Simone Sturniolo Miri Zilka Fabio Ziarelli Stéphane Viel Jonathan R. Yates Giulia Mollica 《Magnetic resonance in chemistry : MRC》2019,57(5):256-264
Structure determination of functional organic compounds remains a formidable challenge when the sample exists as a powder. Nuclear magnetic resonance crystallography approaches based on the comparison of experimental and Density Functional Theory (DFT)-computed 1H chemical shifts have already demonstrated great potential for structure determination of organic powders, but limitations still persist. In this study, we discuss the possibility of using 13C-13C dipolar couplings quantified on powdered theophylline at natural isotopic abundance with the help of dynamic nuclear polarization, to realize a DFT-free, rapid screening of a pool of structures predicted by ab initio random structure search. We show that although 13C-13C dipolar couplings can identify structures possessing long range structural motifs and unit cell parameters close to those of the true structure, it must be complemented with other data to recover information about the presence and the chemical nature of the supramolecular interactions. 相似文献
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Weixun Wang Bernard K. Choi Wenyu Li Zhege Lao Anita Y. H. Lee Sandra C. Souza Nathan A. Yates Timothy Kowalski Alessandro Pocai Lucinda H. Cohen 《Journal of the American Society for Mass Spectrometry》2014,25(4):614-625
Stromal cell-derived factor 1α (SDF-1α) or CXCL12 is a small pro-inflammatory chemoattractant cytokine and a substrate of dipeptidyl peptidase IV (DPP-IV). Proteolytic cleavage by DPP-IV inactivates SDF-1α and attenuates its interaction with CXCR4, its cell surface receptor. To enable investigation of suppression of such inactivation with pharmacologic inhibition of DPP-IV, we developed quantitative mass spectrometric methods that differentiate intact SDF-1α from its inactive form. Using top-down strategy in quantification, we demonstrated the unique advantage of keeping SDF-1α’s two disulfide bridges intact in the analysis. To achieve the optimal sensitivity required for quantification of intact and truncated SDF-1α at endogenous levels in blood, we coupled nano-flow tandem mass spectrometry with antibody-based affinity enrichment. The assay has a quantitative range of 20 pmol/L to 20 nmol/L in human plasma as well as in rhesus monkey plasma. With only slight modification, the same assay can be used to quantify SDF-1α in mice. Using two in vivo animal studies as examples, we demonstrated that it was critical to differentiate intact SDF-1α from its truncated form in the analysis of biomarkers for pharmacologic inhibition of DPP-IV activity. These novel methods enable translational research on suppression of SDF-1 inactivation with DPP-IV inhibition and can be applied to relevant clinical samples in the future to yield new insights on change of SDF-1α levels in disease settings and in response to therapeutic interventions. Figure
? 相似文献
27.
John R. Yates Jimmy K. Eng Karl R. Clauser Alma L. Burlingame 《Journal of the American Society for Mass Spectrometry》1996,7(11):1089-1098
We have broadened the utility of the SEQUEST computer algorithms to permit correlation of uninterpreted high-energy collision-induced dissociation spectra of peptides with all sequences in a database. SEQUEST now allows for the additional fragment ion types observed under high-energy conditions. We analyzed spectra from peptides isolated following trypsin digestion of 13 proteins. SEQUEST ranked the correct sequence first for 90% (18/20) of the spectra in searches of the OWL database, without constraint by enzyme cleavage specificity or species of origin. All false-positives were flagged by the scoring system. SEQUEST searches databases for sequences that correspond to the precursor ion mass ±0.5 u. Preliminary ranking of the top 500 candidates is done by calculation of fragment ion masses for each sequence, and comparison to the measured ion masses on the basis of ion series continuity, summed ion intensity, and immonium ion presence. Final ranking is done by construction of model spectra for the 500 candidates and constructing/performing of a cross-correlation analysis with the actual spectrum. Given the need to relate mounting genome sequence information with corresponding suites of proteins that comprise the cellular molecular machinery, tandem mass spectrometry appears destined to play the leading role in accelerating protein identification on the large scale required. 相似文献
28.
J. L. Pore D. S. Cross C. Andreoiu R. Ashley G. C. Ball P. C. Bender A. S. Chester A. Diaz Varela G. A. Demand R. Dunlop A. B. Garnsworthy P. E. Garrett G. Hackman B. Hadinia B. Jigmeddorj A. T. Laffoley A. Liblong R. Kanungo B. Noakes C. M. Petrache M. M. Rajabali K. Starosta C. E. Svensson P. J. Voss Z. M. Wang J. L. Wood S. W. Yates 《The European Physical Journal A - Hadrons and Nuclei》2017,53(2):27
29.
An ion-molecule reaction has been studied by measuring the momentum of both the reactant and the product ions. This is carried out in an ordered molecular film of CD3I where electron stimulated desorption causes the reaction CD+3+ CD3I--> C2D+5+DI. The close similarity of the normal momentum of CD+3 and C2D+5 indicates that a sticky collision occurs in which, to within 10%, the momentum of the reactant ion is transferred to the momentum of the product ion. The measurement represents the first use of molecularly aligned species to study momentum effects in an ion-molecule reaction. 相似文献
30.
C. Harwood G. H. Wostenholm B. Yates D. V. Badami 《Journal of Polymer Science.Polymer Physics》1978,16(5):759-766
Characterization measurements of a commercial phenol-formaldehyde resin prepared from constituents including phenol and formaldehyde in the molar ratio 1:1.33 are reported. The measurements consist of (1) the linear thermal expansion coefficient between approximately 85 and 270°K; (2) the specific heat capacity between approximately 6 and 100°K; (3) the Young's modulus at room temperature. A critical examination of the data reveals that: (1) the vibrational behavior is predominantly that of a three-dimensional assembly; (2) as far as data available from other sources permit an assessment to be made, the principle of additivity appears to be applicable to the specific heat capacity between approximately 50 and 100°K; and (3) the data lie near the limit of an empirical relationship observed between the Young's modulus and linear thermal expansion coefficient of other polymers. 相似文献