33 research outputs found
Dense transcript profiling in single cells by image correlation decoding
Sequential barcoded fluorescent in situ hybridization (seqFISH) allows large numbers of molecular species to be accurately detected in single cells, but multiplexing is limited by the density of barcoded objects. We present correlation FISH (corrFISH), a method to resolve dense temporal barcodes in sequential hybridization experiments. Using corrFISH, we quantified highly expressed ribosomal protein genes in single cultured cells and mouse thymus sections, revealing cell-type-specific gene expression
Dark Matter Results from 225 Live Days of XENON100 Data
We report on a search for particle dark matter with the XENON100 experiment,
operated at the Laboratori Nazionali del Gran Sasso (LNGS) for 13 months during
2011 and 2012. XENON100 features an ultra-low electromagnetic background of
(5.3 \pm 0.6) \times 10^-3 events (kg day keVee)^-1 in the energy region of
interest. A blind analysis of 224.6 live days \times 34 kg exposure has yielded
no evidence for dark matter interactions. The two candidate events observed in
the pre-defined nuclear recoil energy range of 6.6-30.5 keVnr are consistent
with the background expectation of (1.0 \pm 0.2) events. A Profile Likelihood
analysis using a 6.6-43.3 keVnr energy range sets the most stringent limit on
the spin-independent elastic WIMP-nucleon scattering cross section for WIMP
masses above 8 GeV/c^2, with a minimum of 2 \times 10^-45 cm^2 at 55 GeV/c^2
and 90% confidence level.Comment: 6 pages, 5 figures. Matches version accepted by PRL. Includes limits
up to 10 TeV/c^2, published as supplementary material:
http://prl.aps.org/supplemental/PRL/v109/i18/e181301 Please cite high mass
limits as "Phys. Rev. Lett. 109, 181301 (2012), online supplementary
material.
In situ measurements of krypton in xenon gas with a quadrupole mass spectrometer following a cold-trap at a temporarily reduced pumping speed
A nanostructure-initiator mass spectrometry-based enzyme activity assay
We describe a Nanostructure-Initiator Mass Spectrometry (NIMS) enzymatic (Nimzyme) assay in which enzyme substrates are immobilized on the mass spectrometry surface by using fluorous-phase interactions. This “soft” immobilization allows efficient desorption/ionization while also enabling the use of surface-washing steps to reduce signal suppression from complex biological samples, which results from the preferential retention of the tagged products and reactants. The Nimzyme assay is sensitive to subpicogram levels of enzyme, detects both addition and cleavage reactions (sialyltransferase and galactosidase), is applicable over a wide range of pHs and temperatures, and can measure activity directly from crude cell lysates. The ability of the Nimzyme assay to analyze complex mixtures is illustrated by identifying and directly characterizing β-1,4-galactosidase activity from a thermophilic microbial community lysate. The optimal enzyme temperature and pH were found to be 65°C and 5.5, respectively, and the activity was inhibited by both phenylethyl-β-d-thiogalactopyranoside and deoxygalactonojirimycin. Metagenomic analysis of the community suggests that the activity is from an uncultured, unsequenced γ-proteobacterium. In general, this assay provides an efficient method for detection and characterization of enzymatic activities in complex biological mixtures prior to sequencing or cloning efforts. More generally, this approach may have important applications for screening both enzymatic and inhibitor libraries, constructing and screening glycan microarrays, and complementing fluorous-phase organic synthesis