34 research outputs found
Microfluidics for biological measurements with single-molecule resolution
Single-molecule approaches in biology have been critical in studies ranging from the examination of physical properties of biological macromolecules to the extraction of genetic information from DNA. The variation intrinsic to many biological processes necessitates measurements with single-molecule resolution in order to accurately recapitulate population distributions. Microfluidic technology has proven to be useful in the facilitation and even enhancement of single-molecule studies because of the precise liquid handling, small volume manipulation, and high throughput capabilities of microfluidic devices. In this review we survey the microfluidic âtoolboxâ available to the single-molecule specialist and summarize some recent biological applications of single-molecule detection on chip
High-throughput single-molecule optofluidic analysis
We describe a high-throughput, automated single-molecule measurement system, equipped with microfluidics. The microfluidic mixing device has
integrated valves and pumps to accurately accomplish titration of
biomolecules with picoliter resolution. We demonstrate that the
approach enabled rapid sampling of biomolecule conformational landscape
and of enzymatic activity, in the form of transcription by Escherichia
coli RNA polymerase, as a function of the chemical environment
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Sources, distribution, and acidity of sulfateâammonium aerosol in the Arctic in winterâspring
We use GEOS-Chem chemical transport model simulations of sulfateâammonium aerosol data from the NASA ARCTAS and NOAA ARCPAC aircraft campaigns in the North American Arctic in April 2008, together with longer-term data from surface sites, to better understand aerosol sources in the Arctic in winterâspring and the implications for aerosol acidity. Arctic pollution is dominated by transport from mid-latitudes, and we test the relevant ammonia and sulfur dioxide emission inventories in the model by comparison with wet deposition flux data over the source continents. We find that a complicated mix of natural and anthropogenic sources with different vertical signatures is responsible for sulfate concentrations in the Arctic. East Asian pollution influence is weak in winter but becomes important in spring through transport in the free troposphere. European influence is important at all altitudes but never dominant. West Asia (non-Arctic Russia and Kazakhstan) is the largest contributor to Arctic sulfate in surface air in winter, reflecting a southward extension of the Arctic front over that region. Ammonium in Arctic spring mostly originates from anthropogenic sources in East Asia and Europe, with added contribution from boreal fires, resulting in a more neutralized aerosol in the free troposphere than at the surface. The ARCTAS and ARCPAC data indicate a median aerosol neutralization fraction [NH4+]/(2[SO42â] + [NO3â]) of 0.5 mol molâ1 below 2 km and 0.7 mol molâ1 above. We find that East Asian and European aerosol transported to the Arctic is mostly neutralized, whereas West Asian and North American aerosol is highly acidic. Growth of sulfur emissions in West Asia may be responsible for the observed increase in aerosol acidity at Barrow over the past decade. As global sulfur emissions decline over the next decades, increasing aerosol neutralization in the Arctic is expected, potentially accelerating Arctic warming through indirect radiative forcing and feedbacks.Chemistry and Chemical Biolog
Transboundary health impacts of transported global air pollution and international trade
Millions of people die every year from diseases caused by exposure to outdoor air pollution1, 2, 3, 4, 5. Some studies have estimated premature mortality related to local sources of air pollution6, 7, but local air quality can also be affected by atmospheric transport of pollution from distant sources8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18. International trade is contributing to the globalization of emission and pollution as a result of the production of goods (and their associated emissions) in one region for consumption in another region14, 19, 20, 21, 22. The effects of international trade on air pollutant emissions23, air quality14 and health24 have been investigated regionally, but a combined, global assessment of the health impacts related to international trade and the transport of atmospheric air pollution is lacking. Here we combine four global models to estimate premature mortality caused by fine particulate matter (PM2.5) pollution as a result of atmospheric transport and the production and consumption of goods and services in different world regions. We find that, of the 3.45 million premature deaths related to PM2.5 pollution in 2007 worldwide, about 12 per cent (411,100 deaths) were related to air pollutants emitted in a region of the world other than that in which the death occurred, and about 22 per cent (762,400 deaths) were associated with goods and services produced in one region for consumption in another. For example, PM2.5 pollution produced in China in 2007 is linked to more than 64,800 premature deaths in regions other than China, including more than 3,100 premature deaths in western Europe and the USA; on the other hand, consumption in western Europe and the USA is linked to more than 108,600 premature deaths in China. Our results reveal that the transboundary health impacts of PM2.5 pollution associated with international trade are greater than those associated with long-distance atmospheric pollutant transport
Transboundary health impacts of transported global air pollution and international trade
Controller for microfluidic large-scale integration
Microfluidic devices with integrated valves provide precise, programmable fluid handling platforms for high-throughput biological or chemical assays. However, setting up the infrastructure to control such platforms often requires specific engineering expertise or expensive commercial solutions. To address these obstacles, we present a Kit for Arduino-based Transistor Array Actuation (KATARA), an open-source and low-cost Arduino-based controller that can drive 70 solenoid valves to pneumatically actuate integrated microfluidic valves. We include a python package with a GUI to control the KATARA from a personal computer. No programming experience is required. Keywords: Python, Arduino shield, Open source hardware, Solenoid valve, Microfluidics, Multi-layer soft lithograph
Direct Observation of Ostwald Ripening in Free-Interface Diffusion Based Protein Crystallization
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Quantitative imaging of lipid droplets in single cells
The combination of next generation sequencing (NGS) and automated liquid handling platforms has led to a revolution in single-cell genomic studies. However, many molecules that are critical to understanding the functional roles of cells in a complex tissue or organs, are not directly encoded in the genome, and therefore cannot be profiled with NGS. Lipids, for example, play a critical role in many metabolic processes but cannot be detected by sequencing. Recent developments in quantitative imaging, particularly coherent Raman scattering (CRS) techniques, have produced a suite of tools for studying lipid content in single cells. This article reviews CRS imaging and computational image processing techniques for non-destructive profiling of dynamic changes in lipid composition and spatial distribution at the single-cell level. As quantitative CRS imaging progresses synergistically with microfluidic and microscopic platforms for single-cell genomic analysis, we anticipate that these techniques will bring researchers closer towards combined lipidomic and genomic analysis
Label-Free Digital Quantification of Lipid Droplets in Single Cells by Stimulated Raman Microscopy on a Microfluidic Platform
Quantitative characterization of
a single-cell phenotype remains
challenging. We combined a scalable microfluidic array of parallel
cell culture chambers and stimulated Raman scattering (SRS) microscopy
to quantitatively characterize the response of lipid droplet (LD)
formation to free-fatty-acid stimuli with single-LD resolution at
the single-cell level. By enabling the systematic live-cell imaging
with SRS microscopy in a microfluidic device, we were able to quantify
the morphology of over a thousand live cells in 10 different chemical
environments and with 8 replicates for each culture condition, in
a single experiment, and without relying on fluorescent labeling.
We developed an image processing pipeline for cell segmentation and
LD morphology quantification using dual-channel SRS images. This allows
us to construct distributions of the morphological parameters of LDs
in the cellular population and expose the vast phenotypic heterogeneity
among genetically similar cells. Specifically, this approach provides
an analytical tool for quantitatively investigating LD morphology
in live cells in situ. With this high-throughput, high-resolution,
and label-free method, we found that LD growth dynamics showed considerable
cell to cell variation. Lipid accumulation in nonadipocyte cells is
mainly reflected in the increase of LD number, as opposed to an increase
in their size or lipid concentration. Our method allows statistical
single-cell quantification of the LD distribution for further investigation
of lipid metabolism and dynamic behavior, and also extends the possibility
to couple with other âomicsâ technologies in the future