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High-Density Arrays of Submicron Spherical Supported Lipid Bilayers
Wittenberg, Nathan J.,Johnson, Timothy W.,Oh, Sang-Hyun American Chemical Society 2012 ANALYTICAL CHEMISTRY - Vol.84 No.19
<P>Lipid bilayer membranes found in nature are heterogeneous mixtures of lipids and proteins. Model systems, such as supported lipid bilayers (SLBs), are often employed to simplify experimental systems while mimicking the properties of natural lipid bilayers. Here, we demonstrate a new method to form SLB arrays by first forming spherical supported lipid bilayers (SSLBs) on submicrometer-diameter SiO<SUB>2</SUB> beads. The SSLBs are then arrayed into microwells using a simple physical assembly method that requires no chemical modification of the substrate nor modification of the lipid membrane with recognition moieties. The resulting arrays have submicrometer SSLBs with 3 μm periodicity where >75% of the microwells are occupied by an individual SSLB. Because the arrays have high density, fluorescence from >1000 discrete SSLBs can be acquired with a single image capture. We show that 2-component random arrays can be formed, and we also use the arrays to determine the equilibrium dissociation constant for cholera toxin binding to ganglioside GM1. SSLB arrays are robust and are stable for at least one week in buffer.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2012/ancham.2012.84.issue-19/ac3014274/production/images/medium/ac-2012-014274_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac3014274'>ACS Electronic Supporting Info</A></P>
Nanopore-Induced Spontaneous Concentration for Optofluidic Sensing and Particle Assembly
Kumar, Shailabh,Wittenberg, Nathan J.,Oh, Sang-Hyun American Chemical Society 2013 ANALYTICAL CHEMISTRY - Vol.85 No.2
<P>Metallic nanopore arrays have emerged as optofluidic platforms with multifarious sensing and analytical capabilities such as label-free surface plasmon resonance (SPR) sensing of molecular binding interactions and surface-enhanced Raman spectroscopy (SERS). However, directed delivery of analytes through open nanopores using traditional methods such as external electric fields or pressure gradients still remains difficult. We demonstrate that nanopore arrays have an intrinsic ability to promote flow through them via capillary flow and evaporation. This passive “nano-drain” mechanism is utilized to concentrate biomolecules on the surface of nanopores for improved detection sensitivity or create ordered nanoscale arrays of beads and liposomes. Without using any external pump or fluidic interconnects, we can concentrate and detect the presence of less than a femtomole of streptavidin in 10 μL of sample using fluorescence imaging. Liposome nanoarrays are also prepared in less than 5 min and used to detect lipid–protein interactions. We also demonstrate label-free SPR detection of analytes using metallic nanopore arrays. This method provides a fast, simple, transportable, and small-volume platform for labeled as well as label-free plasmonic analysis while improving the detection time and sensitivity.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2013/ancham.2013.85.issue-2/ac302690w/production/images/medium/ac-2012-02690w_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac302690w'>ACS Electronic Supporting Info</A></P>
Revisiting ENSO/Indian Ocean Dipole phase relationships : REVISITING ENSO/IOD PHASE RELATIONSHIPS
Stuecker, Malte F.,Timmermann, Axel,Jin, Fei-Fei,Chikamoto, Yoshimitsu,Zhang, Wenjun,Wittenberg, Andrew T.,Widiasih, Esther,Zhao, Sen American Geophysical Union 2017 Geophysical research letters Vol.44 No.5
Ryu, Yong-Sang,Yun, Hansik,Chung, Taerin,Suh, Jeng-Hun,Kim, Sungho,Lee, Kyookeun,Wittenberg, Nathan J.,Oh, Sang-Hyun,Lee, Byoungho,Lee, Sin-Doo Elsevier Applied Science 2019 Biosensors & bioelectronics Vol. No.
<P><B>Abstract</B></P> <P>A label-free, non-dispruptive, and real-time analytical device to monitor the dynamic features of biomolecules and their interactions with neighboring molecules is an essential prerequisite for biochip- and diagonostic assays. To explore one of the central questions on the lipid-lipid interactions in the course of the liquid-ordered (<I>l</I> <SUB> <I>o</I> </SUB>) domain formation, called rafts, we developed a method of reconstituting continuous but spatially heterogeneous lipid membrane platforms with molayer-bilayer juntions (MBJs) that enable to form the <I>l</I> <SUB> <I>o</I> </SUB> domains in a spatiotemporally controlled manner. This allows us to detect the time-lapse dynamics of the lipid-lipid interactions during raft formation and resultant membrane phase changes together with the raft-associated receptor-ligand binding through the surface plasmon resonance (SPR). For cross-validation, using epifluorescence microscopy, we demonstrated the underlying mechanisms for raft formations that the infiltration of cholesterols into the sphingolipid-enriched domains plays a crucial roles in the membrane phase-separation. Our membrane platform, being capable of monitoring dynamic interactions among lipids and performing the systematic optical analysis, will unveil physiological roles of cholesterols in a variety of biological events.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Continuous but spatially heterogeneous membranes were probed by the SPR for monitoring the kinetic behavior of lipid-lipid interactions </LI> <LI> The accompanying biochemical activity of ligand-receptor binding. Our monolayer-bilayer junction methodology of manipulating the bio-membranes enables to precisely control the phase-separation of l<SUB>o</SUB> domains at pre-defined regions on a SPR-based biochip and to unveil the kinetics of the raft formation together with raft-associated receptor-ligand interactions </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Continuous but spatially heterogeneous membranes were probed by the SPR for monitoring the kinetic behavior of lipid-lipid interactions (a) and the accompanying biochemical activity of ligand-receptor binding. Our monolayer-bilayer junction methodology of manipulating the bio-membranes enables to precisely control the phase-separation of <I>l</I> <SUB> <I>o</I> </SUB> domains at pre-defined regions (b) on a SPR-based biochip and to unveil the kinetics of the raft formation together with raft-associated receptor-ligand interactions (c).</P> <P>[DISPLAY OMISSION]</P>
On the Fragile Relationship Between El Niño and California Rainfall
Lee, Sang‐,Ki,Lopez, Hosmay,Chung, Eui‐,Seok,DiNezio, Pedro,Yeh, Sang‐,Wook,Wittenberg, Andrew T. American Geophysical Union 2018 Geophysical Research Letters Vol.45 No.2
<P>The failed influence of the 2015-2016 El Nino on California rainfall has renewed interest in the relationship between El Nino and U.S. rainfall variability. Here we perform statistical data analyses and simple model experiments to show that sufficiently warm and persistent sea surface temperature anomalies (SSTAs) in the far eastern equatorial Pacific are required to excite an anomalous cyclone in the North Pacific that extends to the east across the U.S. West Coast and thus increases rainfall over California. Among the four most frequently recurring El Nino patterns considered in this study, only the persistent El Nino, which is often characterized by the warm SSTAs in the far eastern equatorial Pacific persisting throughout the winter and spring, is linked to such extratropical teleconnection patterns and significantly increased rainfall over the entire state of California. During the last 69 years, only three of the 25 El Nino events (i.e., 1957-1958, 1982-1983, and 1997-1998) are clearly identified as the persistent El Nino. In addition, the monthly rainfall variance explained by El Nino is less than half that caused by internal variability during the 25 El Nino. Therefore, the rarity of persistent El Nino events combined with the large influence of internal variability effectively explains the fragile relationship between El Nino and California rainfall.</P>
Uncertainty in the ENSO amplitude change from the past to the future
Watanabe, Masahiro,Kug, Jong‐,Seong,Jin, Fei‐,Fei,Collins, Mat,Ohba, Masamichi,Wittenberg, Andrew T. American Geophysical Union 2012 Geophysical research letters Vol.39 No.20
<P>Due to errors in complex coupled feedbacks that compensate differently in different global climate models, as well as nonlinear nature of El Niño-Southern Oscillation (ENSO), there remain difficulties in detecting and evaluating the reason for the past and future changes in the ENSO amplitude,σnino. Here we use physics parameter ensembles, in which error compensation was eliminated by perturbing model parameters, to explore relationships between mean climate and variability. With four such ensembles we find a strong relationship between σniño and the mean precipitation over the eastern equatorial Pacific ( urn:x-wiley:00948276:media:grl29646:grl29646-math-0001). This involves a two?way interaction, in which the wetter mean state with greater urn:x-wiley:00948276:media:grl29646:grl29646-math-0001acts to increase the ENSO amplitude by strengthening positive coupled feedbacks. Such a relationship is also identified in 11 single?model historical climate simulations in the Coupled Model Intercomparison Project phase 5 despite mean precipitation biases apparently masking the relationship in the multi?model ensemble (MME). Taking changes inσniño and urn:x-wiley:00948276:media:grl29646:grl29646-math-0001between pre-industrial and recent periods eliminates the bias, and therefore results in a robustσnino-urn:x-wiley:00948276:media:grl29646:grl29646-math-0001connection in MME, which suggests a 10-15% increase in the ENSO amplitude since pre-industrial era mainly due to changing mean state. However, theσniño– urn:x-wiley:00948276:media:grl29646:grl29646-math-0001 connection is less clear for their future changes, which are still greatly uncertain.</P>
Author Correction: El Niño-Southern Oscillation complexity
Timmermann, Axel,An, Soon-Il,Kug, Jong-Seong,Jin, Fei-Fei,Cai, Wenju,Capotondi, Antonietta,Cobb, Kim M.,Lengaigne, Matthieu,McPhaden, Michael J.,Stuecker, Malte F.,Stein, Karl,Wittenberg, Andrew T.,Yu Springer Science and Business Media LLC 2019 Nature Vol.567 No.7746
The impact of global warming on the tropical Pacific Ocean and El Niño
Collins, Mat,An, Soon-Il,Cai, Wenju,Ganachaud, Alexandre,Guilyardi, Eric,Jin, Fei-Fei,Jochum, Markus,Lengaigne, Matthieu,Power, Scott,Timmermann, Axel,Vecchi, Gabe,Wittenberg, Andrew Springer Science and Business Media LLC 2010 Nature geoscience Vol.3 No.6