Von Willebrand factor (VWF) is a multimeric plasma glycoprotein involved in both hemostasis and thrombosis. VWF conformational changes, especially unfolding of the A2 domain, may be required for efficient enzymatic cleavage in vivo. It has been shown that a single A2 domain unfolds at most probable unfolding forces of 7-14 pN at force loading rates of 0.35-350 pN/s and A2 unfolding facilitates A2 cleavage in vitro. However, it remains unknown how much force is required to unfold the A2 domain in the context of a VWF multimer where A2 may be stabilized by other domains like A1 and A3. With the optical trap, we stretched VWF multimers and a poly-protein (A1A2A3)3 that contains three repeats of the triplet A1A2A3 domains at constant speeds of 2000 nm/s and 400 nm/s, respectively, which yielded corresponding average force loading rates of 90 and 22 pN/s. We found that VWF multimers became stiffer when they were stretched and extended by force. After force increased to a certain level, sudden extensional jumps that signify domain unfolding were often observed. Histograms of the unfolding force and the unfolded contour length showed two or three peaks that were integral multiples of approximately 21 pN and approximately 63 nm, respectively. Stretching of (A1A2A3)3 yielded comparable distributions of unfolding force and unfolded contour length, showing that unfolding of the A2 domain accounts for the behavior of VWF multimers under tension. These results show that the A2 domain can be indeed unfolded in the presence of A1, A3, and other domains. Compared with the value in the literature, the larger most probable unfolding force measured in this study suggests that the A2 domain is mechanically stabilized by A1 or A3 although variations in experimental setups and conditions may complicate this interpretation.

Flagella and cilia are thin, active organelles protruding from cells that are used to propel the cell or move fluid. The flagellated alga Chlamydomonas reinhardtii is a uni-cellular model organism well-suited for the study of flagellar and cilia mechanics.

Junyi Ying (Eric), a senior high school student in Shanghai, China, spent two weeks actively engaged in a research project involving the colorimetric analysis of phosphates in designated locations along the Shanghai tributary of the Yangtze River. Ying is a student at Shanghai Guanghua College. He is an excellent student seeking to pursue a career in chemistry at a major US University commencing the 2018-2019 academic year.He has received several outstanding accommodations for his work in honors chemistry at Shanghai Guanghua College. Mr. Cyrus SafaiCyrus is an undergraduate student majoring in Mechanical Engineering at Salt Lake Community College (SLCC). Cyrus has teamed up and worked with a group of four other students from Mechanical, Civil, Electrical, and Computer engineering departments on the Vertical, Hydroponic, Smart Garden With Global and Universal (Space) Applications. He has worked at the SLCC Slick Science Summer Camp for the past 7 years. Mr. Junior onyeagbaJunior Onyeagba, a former student at Salt Lake Community College, who is currently attending the University of Utah with the purpose of attaining a Bachelor's degree in Biology with cell and molecular emphasis. Junior has worked with phosphate over a year now with the intention of finding a more effective way to measure the concentration of phosphate in waterbodies using Flow Injection Analysis.Dr. Nick M. Safai, Salt Lake Community College Dr. Nick M. Safai has been an ASEE officer and member for the past 24 years. He has been the six-time elected as the Program Chair of the ASEE International Division for approximately the past 13 years. Nick has had a major role in development and expansion of the division. Under his term as the International Division Program Chair the international division expanded, broadened in topics, and the number of sessions increased from a few technical sessions to over eighteen sessions in the recent years. The