The Determining Factors of the Self-Assembly of Collagen Mimetic Peptide

We recently reported that a designed triple helix Col108 self-associates to form collagen-like mini-fibrils having a d-periodicity of 35 nm. Recombinant protein Col108 consists of 378-residue triple helix domain organized into three repeating sequence units, and a C-terminal foldon domain. The 35 nm d-period of Col108 mini-fibrils is consistent with the one unit staggered arrangement of the associating helices. To further investigate if the sequence periodicity is crucial for collagen mimetic peptide fibril formation, we studied the self-assembly of four other designed triple helical peptides. Peptide 2U108 has two repeating sequence units; peptide Col877 consists of three repeating units but the amino acid sequence of each unit is very different from that of Col108; peptide 1U108 has only one sequence unit and peptide. Col108r has the same amino acid composition of that of Col108 but lacks the sequence periodicity. Both 2U108 and Col877 formed mini-fibrils having the same periodicity of 35 nm as that observed in Col108 under electron microscopy, but no fibril-like assemblies were observed for either 1U108 or Col108r. Since both 2U108 and Col877 have tandem repeats of sequence units while 1U108 and Col108r do not, these findings support the essential roles of the long-range repeating sequence units on the self-assembly of collagen-like, staggered fibrils and suggest a design-rule for the self-assembly of triple helices into collagen-like mini-fibrils

The expression of Sirtuin1 and its role in ovarian cancer

SIRT1 has been a popular subject in the scientific research field since its detection in 1990. The function of this protein varies greatly depending on the tissue. Recent studies focused on SIRT1, especially in tumors. SIRT1 has been revealed to modulate cancer cell growth, metastasis, and invasion in numerous tumors. However, SIRT1 has been barely studied in gynecological tumors. The purpose of our study was to evaluate the effect of SIRT1 on ovarian cancer. First, we analyzed the relationship between the intensity of SIRT1 and RXR-alpha staining and clinical prognosis in ovarian cancer by immunohistochemistry. To further study the therapeutic effects of SIRT1 activator Resveratrol, we used MTT, M30, BrdU, and other methods to test the function of resveratrol on ovarian cancer cell lines A2780, UWB1, 289, and A2780cis, including proliferation and apoptosis. Finally, the relationship between RXR-alpha and SIRT1 proteins in ovarian cancer treated with Resveratrol was studied by western blot. Studies have shown that nuclear RXR-alpha and SIRT1-expression are significantly connected with a better outcome and overall survival rates in advanced ovarian cancer. Resveratrol had a direct effect on ovarian cancer: it suppressed the growth and proliferation of ovarian cancer cells and even increased their apoptosis. At the protein level, resveratrol (100 μM, 24h) up-regulated the expression of RXR-alpha in the anti-carboplatin cell line A2780cis and down-regulated the expression of SIRT1 in A2780. In conclusion, SIRT1 may have a suppressive role in ovarian cancer, especially in advanced ovarian cancer

Enhanced bias stress stability of a-InGaZnO thin film transistors by inserting an ultra-thin interfacial InGaZnO:N layer

Amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) having an ultra-thin nitrogenated a-IGZO (a-IGZO:N) layer sandwiched at the channel/gate dielectric interface are fabricated. It is found that the device shows enhanced bias stress stability with significantly reduced threshold voltage drift under positive gate bias stress. Based on x-ray photoelectron spectroscopy measurement, the concentration of oxygen vacancies within the a-IGZO:N layer is suppressed due to the formation of N-Ga bonds. Meanwhile, low frequency noise analysis indicates that the average trap density near the channel/dielectric interface continuously drops as the nitrogen content within the a-IGZO:N layer increases. The improved interface quality upon nitrogen doping agrees with the enhanced bias stress stability of the a-IGZO TFTs.This work was supported in part by the State Key Program for Basic Research of China under Grant Nos. 2010CB327504, 2011CB922100, and 2011CB301900; in part by the National Natural Science Foundation of China under Grant Nos. 60936004 and 11104130; in part by the Natural Science Foundation of Jiangsu Province under Grant Nos. BK2011556 and BK2011050; and in part by the Priority Academic Program Development of Jiangsu Higher Education Institutions