Tautomeric Effect of Histidine on the Monomeric Structure of Amyloid β-Peptide(1–40)

Shi, Hu,Kang, Baotao,Lee, Jin Yong American Chemical Society 2016 The Journal of physical chemistry B Vol.120 No.44

<P>Histidine state (deprotonated, neutral, and protonated) is considered an important factor influencing the structural properties and aggregation mechanisms in amyloid beta-peptides (A beta), which are associated with the pathogenesis of Alzheimer's disease. Understanding the structural properties and aggregation mechanisms is a great challenge because two forms (the N-epsilon-H or N-delta-H tautomer) can exist in the free neutral state of histidine. Here, replica exchange molecular dynamics simulation was performed to elucidate the changes in structure and the mechanism of aggregation influenced by tautomeric behaviors of histidine in A beta(1-40). Our results show that sheet-dominating conformations can be found in the His6(delta)-His13(delta)-His14(delta) (delta delta delta) isomer with significant antiparallel sheet structures between R5-D7 and L34-G38, as well as between L17-F20 and L34-G38, implying that a new aggregation mechanism may exist to promote the generation of oligomers and/or aggregates. This work fundamental tautomeric behaviors of neutral histidine in the process of aggregation. is helpful in understanding the fundamental tautomeric behaviors of neutral histidine in the process of aggregation.</P>

Zn²⁺ Effect on Structure and Residual Hydrophobicity of Amyloid β-Peptide Monomers

Shi, Hu,Kang, Baotao,Lee, Jin Yong American Chemical Society 2014 The Journal of physical chemistry B Vol.118 No.35

<P>The aggregation of amyloid β-peptide (Aβ peptide) has been associated with the pathogenesis of Alzheimer’s disease (AD). In the present study, we aimed to disclose how Zn<SUP>2+</SUP> affects the Aβ aggregation in detail. Thus, molecular dynamics simulation was implemented to elucidate the changes of structure and residual hydrophobicity upon Zn<SUP>2+</SUP> coordination. Our results show that Zn<SUP>2+</SUP> can strongly influence the structural properties of Aβ40 and Aβ42 by reducing helical formation and increasing turn formation to expose the hydrophobic regions. Furthermore, hydrophobicity of Zn<SUP>2+</SUP>-Aβ40 and Zn<SUP>2+</SUP>-Aβ42 was much higher than that of each monomer, since Zn<SUP>2+</SUP> binding can significantly influence the hydrophilic domains of Aβ. The further analyses indicate that not only four residues (H6, E11, H13, and H14) but also R5, D7, K16, K28, and terminal residues influence hydrophobicity upon Zn<SUP>2+</SUP> coordination. Importantly, R5, K16, and K28 play a crucial role to regulate solvation-free energies. This work is helpful to understand the fundamental role of Zn<SUP>2+</SUP> in aggregation, which could be useful for further development of new drugs to inhibit Zn<SUP>2+</SUP>-Aβ aggregation.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcbfk/2014/jpcbfk.2014.118.issue-35/jp504779m/production/images/medium/jp-2014-04779m_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp504779m'>ACS Electronic Supporting Info</A></P>

Energy Absorption Characteristics of PVC Coarse Aggregate Concrete under Impact Load

Shi Hu,Huaming Tang,Shenyao Han 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.4

In this paper, polyvinyl chloride (PVC) coarse aggregate with different mixing contents is used to solve the problems of plastic pollution, low energy absorption capacity and poor damage integrity, which provides an important reference for PVC plastic concrete used in the initial support structures of highway tunnels and coal mine roadway. At the same time, the energy absorption characteristics and their relationship under different impact loads are studied, which provides an important reference for predicting the energy absorption characteristics of concrete under other PVC aggregate content or higher impact speed. This study replaced natural coarse aggregate in concrete with different contents and equal volume of well-graded flaky PVC particles obtained by crushing PVC soft board. Also, slump, compression, and splitting strength tests, a free falling low-speed impact test of steel balls and a high-speed impact compression test of split Hopkinson pressure bar (SHPB) were carried out. Results demonstrate that the static and dynamic compressive strength decreases substantially, and the elastic modulus and slump decrease slowly with the increase of the mixing amount of PVC aggregate (0–30%). However, the energy absorption rate under low-speed impact and the specific energy absorption per MPa under high-speed impact increase obviously, indicating that the energy absorption capacity is significantly enhanced. Regardless of the mixing amount of PVC aggregate, greater strain rate can significantly enhance the dynamic compressive strength and the specific energy absorption per MPa. After the uniaxial compression test or the SHPB impact test, the relative integrity of the specimen is positively correlated with the mixing amount of PVC aggregate. In addition, the specimens are seriously damaged with the increase of the impact strain rate. When the PVC aggregate content is 20%, the compressive strength and splitting strength of concrete are 33.8 MPa and 3.26 MPa, respectively, the slump is 165 mm, the energy absorption rate under low-speed impact is 89.5%, the dynamic compressive strength under 0.65 Mpa impact air pressure is 58.77 mpa, and the specific energy absorption value per MPa is 13.33, which meets the requirements of shotcrete used in tunnel, roadway support and other impact loads. There is a linear relationship between the energy absorption characteristics under low-speed impact and high-speed impact. The greater the impact pressure, the larger the slope of the fitting straight line. The slope and intercept of the fitting line also show a good linear relationship with the increase of impact pressure. The conclusions can be used to predict the energy absorption characteristics under different PVC aggregate content or higher-speed impact pressure, which can provide important reference for safer, more economical, and environmental protection engineering structure design.

Perceptions of Change and Reform Efforats by Secondary School Mathematics Teachers in the People's Republic of China and the inited States

Jack, Carter,Lu, Shihu,Ferrucci, Beverly J. 한국수학교육학회 1999 수학교육연구 Vol.3 No.1

The present study extends previous research in this area by investigating perceptions of change and reactions to reform efforts by pre-service and practicing secondary school mathematics teachers in the People's Republic of China (PRC) and the United States of America. Interviews were used to gather data about school experiences, teaching practices, and planned changes in mathematics programs. Analysis of the interview data supported earlier findings with respect to the well-planned nature of lessons by PRC teachers and the influence of mathematics contents and examination systems in the PRC. Findings also indicated a general agreement among teachers from both countries favoring less lecturing and more discussion and interactive activities. There were contrasts by nationality in descriptions of future teaching, ideal lessons, sources of teaching ideas, and preferences about school mathematics programs.

Bone Morphogenetic Protein Receptor in the Osteogenic Differentiation of Rat Bone Marrow Stromal Cells

Anxun Wang,Xueqiang Ding,Shihu Sheng,Zhaoyou Yao 연세대학교의과대학 2010 Yonsei medical journal Vol.51 No.5

Purpose: Several signaling pathways have been shown to regulate the lineage commitment and terminal differentiation of bone marrow stromal cells (BMSCs). Bone morphogenetic protein (BMP) signaling has important effects on the process of skeletogenesis. In the present study, we tested the role of bone morphogenetic protein receptor (BMPR) in the osteogenic differentiation of rat bone marrow stromal cells in osteogenic medium (OM) with or without BMP-2. Materials and Methods: BMSCs were harvested from rats and cultured in OM containing dexamethasone,β-glycerophosphate, and ascorbic acid, with or without BMP-2 in order to induce osteogenic differentiation. The alkaline phosphatase (ALP) activity assay and von kossa staining were used to assess the osteogenic differentiation of the BMSCs. BMPR mRNA expression was assessed using reverse transcriptionpolymerase chain reaction (RT-PCR). Results: The BMSCs that underwent osteogenic differentiation in OM showed a higher level of ALP activity and matrix mineralization. BMP-2 alone induced a low level of ALP activity and matrix mineralization in BMSCs, but enhanced the osteogenic differentiation of BMSCs when combined with OM. The OM significantly induced the expression of type IA receptor of BMPR (BMPRIA) and type II receptor of BMPR (BMPRII) in BMSCs after three days of stimulation, while BMP-2 significantly induced BMPRIA and BMPRII in BMSCs after nine or six days of stimulation, respectively. Conclusion: BMSCs commit to osteoblastic differentiation in OM, which is enhanced by BMP-2. In addition, BMP signaling through BMPRIA and BMPRII regulates the osteogenic differentiation of rat BMSCs in OM with or without BMP-2.

Understanding Online Consumer Stickiness in E-commerce Environment : A Relationship Formation Model

Haiping Wang,Guona Gu,Shihu An,Guangchun Zhou 보안공학연구지원센터(IJUNESST) 2014 International Journal of u- and e- Service, Scienc Vol.7 No.3