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Incorporation of membrane proteins into large single bilayer vesicles. Application to rhodopsin.
A general procedure to incorporate membrane proteins in a native state into large single bilayer vesicles is described. The results obtained with rhodopsin from vertebrate and invertebrate retinas are presented. The technique involves: (a) the direct transfer of rhodopsin-lipid complexes from native membranes into ether or pentane, and (b) the sonication of the complex in apolar solvent with aqueous buffer followed by solvent evaporation under reduced pressure. The spectral properties of rhodopsin in the large vesicles are similar to those of rhodopsin in photoreceptors; furthermore, bleached bovine rhodopsin is chemically regenerable with 9-cis retinal. These results establish the presence of photochemically functional rhodopsin in the large vesicles. Freeze-fracture replicas of the vesicles reveal that both internal and external leaflets contain numerous particles approximately 80 A in diameter, indicating that rhodopsin is symmetrically distributed within the bilayer. More than 75% of the membrane area is incorporated into vesicles larger than 0.5 micron and approximately 40% into vesicles larger than 1 micron
Fiducial Stellar Population Sequences for the VJKs Photometric System
We have obtained broad-band near-infrared photometry for seven Galactic star
clusters (M92, M15, M13, M5, NGC1851, M71 and NGC6791) using the WIRCam
wide-field imager on the Canada-France-Hawaii Telescope, supplemented by images
of NGC1851 taken with HAWK-I on the VLT. In addition, 2MASS observations of the
[Fe/H] ~ 0.0 open cluster M67 were added to the cluster database. From the
resultant (V-J)-V and (V-Ks)-V colour-magnitude diagrams (CMDs), fiducial
sequences spanning the range in metallicity, -2.4 < [Fe/H] < +0.3, have been
defined which extend (for most clusters) from the tip of the red-giant branch
(RGB) to ~ 2.5 magnitudes below the main-sequence turnoff. These fiducials
provide a valuable set of empirical isochrones for the interpretation of
stellar population data in the 2MASS system. We also compare our newly derived
CMDs to Victoria isochrones that have been transformed to the observed plane
using recent empirical and theoretical colour-Teff relations. The models are
able to reproduce the entire CMDs of clusters more metal rich than [Fe/H] ~
-1.4 quite well, on the assumption of the same reddenings and distance moduli
that yield good fits of the same isochrones to Johnson-Cousins BV(RI)C
photometry. However, the predicted giant branches become systematically redder
than the observed RGBs as the cluster metallicity decreases. Possible
explanations for these discrepancies are discussed.Comment: 18 pages, 20 figures, Accepted for publication in A
Color-Magnitude Diagram Constraints on the Metallicities, Ages, and Star Formation History of the Stellar Populations in the Carina Dwarf Spheroidal Galaxy
Victoria-Regina isochrones for [alpha/Fe] and a wide
range in [Fe/H], along with complementary zero-age horizontal branch (ZAHB)
loci, have been applied to the color-magnitude diagram (CMD) of Carina. The
color transformations that we have used have been "calibrated" so that
isochrones provide excellent fits to the -diagrams of M3 and
M92, when well supported estimates of the globular cluster (GC) reddenings and
metallicities are assumed. The adopted distance moduli, for both the GCs and
Carina, are based on our ZAHB models, which are able to reproduce the old HB
component (as well as the luminosity of the HB clump) of the dwarf spheroidal
galaxy quite well --- even if it spans a range in [Fe/H] of ~ 1.5 dex, provided
that [alpha/Fe] varies with [Fe/H] in approximately the way that has been
derived spectroscopically. Ages derived here agree reasonably well with those
found previously for the old and intermediate-age turnoff stars, as well as for
the period of negligible star formation (SF) activity (~ 6-10 Gyr ago). CMD
simulations have been carried out for the faintest turnoff and subgiant stars.
They indicate a clear preference for SF that lasted several Gyr instead of a
short burst, with some indication that ages decrease with increasing [Fe/H]. In
general, stellar models that assume spectroscopic metallicities provide
satisfactory fits to the observations, including the thin giant branch of
Carina, though higher oxygen abundances than those implied by the adopted
values of [alpha/Fe] would have favorable consequences.Comment: 15 pages, including 12 figures; accepted for publication in the
Astrophysical Journa
Seed size in lentil: iMapping at the U of S
Non-Peer Reviewe
Seed size in lentil: iMapping at the U of S
Non-Peer Reviewe
Do grasshoppers prefer one species of lentil over another?
Non-Peer ReviewedSevere outbreaks of grasshoppers cause yield losses in many economically important crops. Lentil (Lens culinaris) is particularly susceptible to grasshopper damage. The weather patterns of 2001-2002 in most of the lentil production regions of Saskatchewan contributed to the outbreak in grasshopper populations resulting in major damage to the lentil crop. Grasshoppers preferentially target the flowers and young pods of lentil plants. Lentil plants, due to their indeterminate growth habit, will re-grow if moisture is available, leading to development of new pods, resulting in delayed maturity and further grasshopper damage. Pods that are damaged or not consumed entirely may shatter or not fill properly. Grasshoppers are known to have very specific feeding habits and may show a range of preference from one plant species to another based on taste or texture. One of the seven known species of lentil has hairy pods. Grasshopper
feeding preferences were examined on five lentil species, including the cultivated lentil. The purpose was to determine if grasshoppers prefer to feed on the cultivated lentil compared to four wild species. If they do, it may be possible in future to breed lentil varieties that are less damaged by grasshoppers by using the wild lentil species in the breeding program
Using Lens lamottei to transfer anthracnose resistance to lentil varieties
Non-Peer ReviewedAnthracnose is a serious fungal disease of lentil that can cause severe yield loss. It is now widespread in Saskatchewan and can be devastating in years with warm wet weather. Producers are limited to controlling this disease by crop rotation, foliar spray or development of varieties with resistance to anthracnose. Pathology research shows that we have two major strains of lentil anthracnose. Varieties like CDC Robin have resistance to one of the strains, but after exhaustive screening of cultivated lentil germplasm, no resistance was found to the second strain of anthracnose. One of the newly discovered wild species of lentil, Lens lamottei, has recently been discovered to have resistance to a combination of both strains of anthracnose when grown under field conditions in an inoculated disease nursery. The objective of this project is to determine if L. lamottei can be by crossed with L. culinaris in order to transfer anthracnose resistance into lentil varieties
Age Constraints for an M31 Globular Cluster from Main Sequence Photometry
We present a color-magnitude diagram (CMD) of the globular cluster SKHB-312
in the Andromeda galaxy (M31), obtained with the Advanced Camera for Surveys on
the Hubble Space Telescope. The cluster was included in deep observations taken
to measure the star formation history of the M31 halo. Overcoming a very
crowded field, our photometry of SKHB-312 reaches V ~ 30.5 mag, more than 1 mag
below the main sequence turnoff. These are the first observations to allow a
direct age estimate from the turnoff in an old M31 cluster. We analyze its CMD
and luminosity function using a finely-spaced grid of isochrones that have been
calibrated using observations of Galactic clusters taken with the same camera
and filters. The luminosity difference between the subgiant and horizontal
branches is ~0.2 mag smaller in SKHB-312 than in the Galactic clusters 47 Tuc
and NGC 5927, implying SKHB-312 is 2-3 Gyr younger. A quantitative comparison
to isochrones yields an age of 10 +2.5/-1 Gyr
The SNARE Protein Syntaxin 3 Confers Specificity for Polarized Axonal Trafficking in Neurons.
Cell polarity and precise subcellular protein localization are pivotal to neuronal function. The SNARE machinery underlies intracellular membrane fusion events, but its role in neuronal polarity and selective protein targeting remain unclear. Here we report that syntaxin 3 is involved in orchestrating polarized trafficking in cultured rat hippocampal neurons. We show that syntaxin 3 localizes to the axonal plasma membrane, particularly to axonal tips, whereas syntaxin 4 localizes to the somatodendritic plasma membrane. Disruption of a conserved N-terminal targeting motif, which causes mislocalization of syntaxin 3, results in coincident mistargeting of the axonal cargos neuron-glia cell adhesion molecule (NgCAM) and neurexin, but not transferrin receptor, a somatodendritic cargo. Similarly, RNAi-mediated knockdown of endogenous syntaxin 3 leads to partial mistargeting of NgCAM, demonstrating that syntaxin 3 plays an important role in its targeting. Additionally, overexpression of syntaxin 3 results in increased axonal growth. Our findings suggest an important role for syntaxin 3 in maintaining neuronal polarity and in the critical task of selective trafficking of membrane protein to axons
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