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- 저자 : James Weber (검색결과 5 건)
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Factors Affecting the Production of Aromatic Immonium Ions in MALDI 157 nm Photodissociation Studies
DeGraan-Weber, Nick,Ashley, Daniel C.,Keijzer, Karlijn,Baik, Mu-Hyun,Reilly, James P. Springer New York LLC 2016 Journal of the American Society for Mass Spectrome Vol.27 No.5
<P>Immonium ions are commonly observed in the high energy fragmentation of peptide ions. In a MALDI-TOF/TOF mass spectrometer, singly charged peptides photofragmented with 157 nm VUV light yield a copious abundance of immonium ions, especially those from aromatic residues. However, their intensities may vary from one peptide to another. In this work, the effect of varying amino acid position, peptide length, and peptide composition on immonium ion yield is investigated. Internal immonium ions are found to have the strongest intensity, whereas immonium ions arising from C-terminal residues are the weakest. Peptide length and competition among residues also strongly influence the immonium ion production. Quantum calculations provide insights about immonium ion structures and the fragment ion conformations that promote or inhibit immonium ion formation.</P> [FIG OMISSION]</BR>
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Panagiotis Tsakiroglou,James Weber,Sharon Ashworth,Cristian Del Bo,Dorothy Klimis-Zacas 한국식품영양과학회 2021 Journal of medicinal food Vol.24 No.3
Wild blueberries rank very high in anthocyanins (ACNs) and phenolic acids (PA) among other berries. Previous work from our group has documented their beneficial effects. In this study, human umbilical vein endothelial cells were used, and ACNs, PAs, and their combination (ACNs:PAs) at concentrations of 0.002, 8, 15, 60, and 120 μg/mL were tested for endothelial tube formation. Treatment with ACNs decreased, while treatment with PAs and ACNs:PAs increased overall endothelial cell tube formation compared to control. Endothelial cells exposed to ACNs downregulated gene expression of AKT1 and endothelial nitric oxide synthase (eNOS), while PAs upregulated AKT1 and vascular endothelial growth factor (VEGF) gene expression. Combination of ACNs:PAs decreased gene expression of AKT1 and eNOS, while protein levels of AKT1 increased. In summary, based on the type of wild blueberry extract, angiogenesis is differentially modulated and is concentration dependent. Further experiments will delineate the mechanism(s) of the differential action of the aforementioned extracts on angiogenesis.
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Alexander E Weber,Ioanna K Bolia,Andrew Horn,Diego Villacis,Reza Omid,James E Tibone,Eric White,George F Hatch 대한정형외과학회 2021 Clinics in Orthopedic Surgery Vol.13 No.2
Background: Recent literature suggests that three-dimensional magnetic resonance imaging (3D MRI) can replace 3D computed tomography (3D CT) when evaluating glenoid bone loss in patients with shoulder instability. We aimed to examine if 2D MRI in conjunction with a validated predictive formula for assessment of glenoid height is equivalent to the gold standard 3D CT scans for patients with recurrent glenohumeral instability. Methods: Patients with recurrent shoulder instability and available imaging were retrospectively reviewed. Glenoid height on 3D CT and 2D MRI was measured by two blinded raters. Difference and equivalence testing were performed using a paired t -test and two one-sided tests, respectively. The interclass correlation coefficient (ICC) was used to test for interrater reliability, and percent agreement between the measurements of one reviewer was used to assess intrarater reliability. Results: Using an equivalence margin of 1 mm, 3D CT and 2D MRI were found to be different (p = 0.123). The mean glenoid height was significantly different when measured on 2D MRI (39.09 ± 2.93 mm) compared to 3D CT (38.71 ± 2.89 mm) (p = 0.032). The mean glenoid width was significantly different between 3D CT (30.13 ± 2.43 mm) and 2D MRI (27.45 ± 1.72 mm) (p < 0.001). The 3D CT measurements had better interrater agreement (ICC, 0.91) than 2D MRI measurements (ICC, 0.8). intrarater agreement was also higher on CT. Conclusions: Measurements of glenoid height using 3D CT and 2D MRI with subsequent calculation of the glenoid width using a validated methodology were not equivalent, and 3D CT was superior. Based on the validated methods for the measurement of glenoid bone loss on advanced imaging studies, 3D CT study must be preferred over 2D MRI in order to estimate the amount of glenoid bone loss in candidates for shoulder stabilization surgery and to assist in surgical decision-making.
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Enhancement of the Electron Spin Resonance of Single-Walled Carbon Nanotubes by Oxygen Removal
Rice, William D.,Weber, Ralph T.,Leonard, Ashley D.,Tour, James M.,Nikolaev, Pavel,Arepalli, Sivaram,Berka, Vladimir,Tsai, Ah-Lim,Kono, Junichiro American Chemical Society 2012 ACS NANO Vol.6 No.3
<P>We have observed a nearly 4-fold increase in the electron spin resonance (ESR) signal from an ensemble of single-walled carbon nanotubes (SWCNTs) due to oxygen desorption. By performing temperature-dependent ESR spectroscopy both before and after thermal annealing, we found that the ESR in SWCNTs can be reversibly altered <I>via</I> the molecular oxygen content in the samples. Independent of the presence of adsorbed oxygen, a Curie law (spin susceptibility ∝ 1/<I>T</I>) is seen from ∼4 to 300 K, indicating that the probed spins are finite-level species. For both the pre-annealed and post-annealed sample conditions, the ESR line width decreased as the temperature was increased, a phenomenon we identify as motional narrowing. From the temperature dependence of the line width, we extracted an estimate of the intertube hopping energy; for both sample conditions, we found this hopping energy to be ∼1.2 meV. Since the spin hopping energy changes only slightly when oxygen is desorbed, we conclude that only the spin susceptibility, not spin transport, is affected by the presence of physisorbed molecular oxygen in SWCNT ensembles. Surprisingly, no line width change is observed when the amount of oxygen in the SWCNT sample is altered, contrary to other carbonaceous systems and certain 1D conducting polymers. We hypothesize that physisorbed molecular oxygen acts as an acceptor (p-type), compensating the donor-like (n-type) defects that are responsible for the ESR signal in bulk SWCNTs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-3/nn204094s/production/images/medium/nn-2011-04094s_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn204094s'>ACS Electronic Supporting Info</A></P>
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