Browsing by Author "Zhang, Qingling"

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    Photofragmentation studies of semiconductor positive cluster ions
    (1989) Zhang, Qingling; Curl, Robert F., Jr.
    Laser photofragmentation of Si, Ge, and GaAs positive cluster ions prepared by laser vaporization and supersonic beam expansion has been investigated in a tandem time-of-flight mass spectrometer. Si$\sb{\rm n}\sp +$ up to size 80, Ge$\sb{\rm n}\sp +$ and Ga$\sb{\rm x}$As$\sb{\rm y}\sp +$ up to a total of 31 atoms have been studied. Ga$\sb{\rm x}$As$\sb{\rm y}\sp +$ fragment in a nearly uniform pattern probably via a step-loss of atoms pattern with odd fragments being more prominent than their even neighbors. Both Si$\sb{\rm n}\sp +$ and Ge$\sb{\rm n}\sp +$ of all sizes show as one fragmentation channel loss of one atom to produce Si$\sb{n-1}\sp +$ or Ge$\sb{n-1}\sp +$. In addition, Si$\sb{\rm n}\sp +$ and Ge$\sb{\rm n}\sp +$ in the size range n = 10-30 photofragment to produce positive ions of about one half the mass of the parent. For Ge$\sb{\rm n}\sp +$ as n becomes greater than 30, this fragmentation becomes a pattern in which positive ions containing 10 (or 7) fewer atoms are the principal products at low laser fluence. Increased fluence seems to fragment these daughters in the same way as they would behave as primary ions. The Si$\sb{\rm n}\sp +$ ions of greater than 30 atoms do not show this 10 or 7 atom neutral loss. Both Si$\sb{\rm n}\sp +$ and Ge$\sb{\rm n}\sp +$ for n $>$ 30 show an additional channel in which small positive ion fragments in the n = 6 to 11 size range are produced. This channel requires high fluence and is shown to involve at least two 6.4 eV (ArF) photons for Si$\sb{60}\sp +$. The absence of intermediate fragments in this channel suggests that these large cluster ions break down into several clusters because the positive charge would be expected to stay with the larger fragment in a fission into two clusters as the ionization potentials of the neutral clusters decrease with size. A reflectron tandem time-of-flight mass spectrometer has been designed and constructed. The resultant high resolution makes the apparatus a highly efficient instrument for fragmentation and spectroscopic studies.
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    Src Inhibition Blocks c-Myc Translation and Glucose Metabolism to Prevent the Development of Breast Cancer
    (AACR, 2015) Jain, Shalini; Wang, Xiao; Chang, Chia-Chi; Ibarra-Drendall, Catherine; Wang, Hai; Zhang, Qingling; Brady, Samuel W.; Li, Ping; Zhao, Hong; Dobbs, Jessica; Kyrish, Matt; Tkaczyk, Tomasz S.; Ambrose, Adrian; Sistrunk, Christopher; Arun, Banu K.; Richards-Kortum, Rebecca; Jia, Wei; Seewaldt, Victoria L.; Yu, Dihua
    Preventing breast cancer will require the development of targeted strategies that can effectively block disease progression. Tamoxifen and aromatase inhibitors are effective in addressing estrogen receptor–positive (ER+) breast cancer development, but estrogen receptor–negative (ER−) breast cancer remains an unmet challenge due to gaps in pathobiologic understanding. In this study, we used reverse-phase protein array to identify activation of Src kinase as an early signaling alteration in premalignant breast lesions of women who did not respond to tamoxifen, a widely used ER antagonist for hormonal therapy of breast cancer. Src kinase blockade with the small-molecule inhibitor saracatinib prevented the disorganized three-dimensional growth of ER− mammary epithelial cells in vitro and delayed the development of premalignant lesions and tumors in vivo in mouse models developing HER2+ and ER− mammary tumors, extending tumor-free and overall survival. Mechanistic investigations revealed that Src blockade reduced glucose metabolism as a result of an inhibition in ERK1/2–MNK1–eIF4E–mediated cap-dependent translation of c-Myc and transcription of the glucose transporter GLUT1, thereby limiting energy available for cell growth. Taken together, our results provide a sound rationale to target Src pathways in premalignant breast lesions to limit the development of breast cancers.