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Jambovane, Sachin,Kim, Duck Jong,Duin, Evert C.,Kim, Se-Kwon,Hong, Jong Wook American Chemical Society 2011 ANALYTICAL CHEMISTRY - Vol.83 No.9
<P>We present a new methodology for generating a stepwise concentration gradient in a series of microdroplets by using monolithic micro valves that act as “faucets” in micrometer-scale. A distinct concentration gradient of a substrate was generated for the determination of the kinetic parameters of two different enzymes using only 10 picoliter-scale droplets. With a single experiment on a chip, we obtained <I>K</I><SUB>M</SUB> and <I>k</I><SUB>cat</SUB> values of matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9), and compared the catalytic competence of the two enzymes. The present system and method are highly suitable for applications where the reagents or samples are limited and precious.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2011/ancham.2011.83.issue-9/ac103217p/production/images/medium/ac-2010-03217p_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac103217p'>ACS Electronic Supporting Info</A></P>
Cell-Based Dose Responses from Open-Well Microchambers
Hamon, Morgan,Jambovane, Sachin,Bradley, Lauren,Khademhosseini, Ali,Hong, Jong Wook American Chemical Society 2013 ANALYTICAL CHEMISTRY - Vol.85 No.10
<P>Cell-based assays play a critical role in discovery of new drugs and facilitating research in cancer, immunology, and stem cells. Conventionally, they are performed in Petri dishes, tubes, or well plates, using milliliters of reagents and thousands of cells to obtain one data point. Here, we are introducing a new platform to realize cell-based assay capable of increased throughput and greater sensitivity with a limited number of cells. We integrated an array of open-well microchambers into a gradient generation system. Consequently, cell-based dose responses were examined with a single device. We measured IC<SUB>50</SUB> values of three cytotoxic chemicals, Triton X-100, H<SUB>2</SUB>O<SUB>2</SUB>, and cadmium chloride, as model compounds. The present system is highly suitable for the discovery of new drugs and studying the effect of chemicals on cell viability or mortality with limited samples and cells.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2013/ancham.2013.85.issue-10/ac400743w/production/images/medium/ac-2013-00743w_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac400743w'>ACS Electronic Supporting Info</A></P>
Log-Scale Dose Response of Inhibitors on a Chip
Yun, Jae Young,Jambovane, Sachin,Kim, Se-Kwon,Cho, Sung-Hak,Duin, Evert C.,Hong, Jong Wook American Chemical Society 2011 ANALYTICAL CHEMISTRY - Vol.83 No.16
<P>We demonstrate the accommodation of log-scale concentration gradients of inhibitors on a single microfluidic chip with a semidirect dilution capability of reagents for the determination of the half-inhibitory concentration or IC<SUB>50</SUB>. The chip provides a unique tool for hosting a wide-range of concentration gradient for studies that require an equal distribution of measuring points on a logarithmic scale. Using Matrix metalloproteinase IX and three of its inhibitors, marimastat, batimastat, and CP471474, we evaluated the IC<SUB>50</SUB> of each inhibitor with a single experiment. The present work could be applied to the systematic study of biochemical binding and inhibition processes particularly in the field of mechanistic enzymology and the pharmaceutical industry.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2011/ancham.2011.83.issue-16/ac201177g/production/images/medium/ac-2011-01177g_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac201177g'>ACS Electronic Supporting Info</A></P>