2,017 research outputs found
The NAD(P)H-utilizing glutamate dehydrogenase of Bacteroides thetaiotamicron belongs to enzyme family I, and its activity is affected by trans-acting gene(s) positioned downstream of gdhA
Previous studies have suggested that regulation of the enzymes of ammonia assimilation in human colonic Bacteroides species is coordinated differently than in other eubacteria. The gene encoding an NAD(P)H-dependent glutamate dehydrogenase (gdhA) in Bacteroides thetaiotaomicron was tinned and expressed in Escherichia coli by mutant complementation from the recombinant plasmid pANS100. Examination of the predicted GdhA amino acid sequence revealed that this enzyme possesses motifs typical of the family I-type hexameric GDH proteins. Northern blot analysis with a gdhA-specific probe indicated that a single transcript with an electrophoretic mobility of ~1.6 kb was produced in both B. thetaiotaomicron and E. coli gdhA transformants. Although gdhA transcription was unaffected, no GdhA enzyme activity could be detected in E. coli transformants when smaller DNA fragments from pANS100, which contained the entire gdhA gene, were analyzed. Enzyme activity was restored if these E. coli strains were cotransformed with a second plasmid, which contained a 3-kb segment of DNA located downstream of the gdhA coding region. Frameshift mutagenesis within the DNA downstream of gdhA in pANS100 also resulted in the loss of GdhA enzyme activity. Collectively, these results are interpreted as evidence for the role of an additional gene product(s) in modulating the activity of GDH enzyme activity. Insertional mutagenesis experiments which led to disruption of the gdhA gene on the B. thetaiotaomicron chromosome indicated that gdhA mutants were not glutamate auxotrophs, but attempts to isolate similar mutants with insertion mutations in the region downstream of the gdhA gene were unsuccessful
Decoding a Three-Dimensional Conformal Manifold
We study the one-dimensional complex conformal manifold that controls the
infrared dynamics of a three-dimensional supersymmetric theory
of three chiral superfields with a cubic superpotential. Two special points on
this conformal manifold are the well-known XYZ model and three decoupled copies
of the critical Wess-Zumino model. The conformal manifold enjoys a discrete
duality group isomorphic to and can be thought of as an orbifold of
. We use the expansion and the numerical
conformal bootstrap to calculate the spectrum of conformal dimensions of
low-lying operators and their OPE coefficients, and find a very good
quantitative agreement between the two approaches.Comment: 59 pages, 13 figure
A non-renormalization theorem for chiral primary 3-point functions
In this note we prove a non-renormalization theorem for the 3-point functions
of 1/2 BPS primaries in the four-dimensional N = 4 SYM and chiral primaries in
two dimensional N =(4,4) SCFTs. Our proof is rather elementary: it is based on
Ward identities and the structure of the short multiplets of the superconformal
algebra and it does not rely on superspace techniques. We also discuss some
possible generalizations to less supersymmetric multiplets.Comment: 32 pages, added references, corrected typo
Recreational Marijuana Laws and Junk Food Consumption: Evidence Using Border Analysis and Retail Sales Data
We use retail scanner data on purchases of high calorie food to study the link between recreational marijuana laws (RMLs) and consumption of high calorie food. To do this we exploit differences in the timing of introduction of marijuana laws among states and find that they are complements. Specifically, in counties located in RML states, monthly sales of high calorie food increased by 3.1 percent for ice cream, 4.1 for cookies, and 5.3 percent for chips. Results are robust to including placebo effective dates for RMLs in treated states as well as when using synthetic control methods as an alternative methodology
High coercivity induced by mechanical milling in cobalt ferrite powders
In this work we report a study of the magnetic behavior of ferrimagnetic
oxide CoFe2O4 treated by mechanical milling with different grinding balls. The
cobalt ferrite nanoparticles were prepared using a simple hydrothermal method
and annealed at 500oC. The non-milled sample presented coercivity of about 1.9
kOe, saturation magnetization of 69.5 emu/g, and a remanence ratio of 0.42.
After milling, two samples attained coercivity of 4.2 and 4.1 kOe, and
saturation magnetization of 67.0 and 71.4 emu/g respectively. The remanence
ratio MR/MS for these samples increase to 0.49 and 0.51, respectively. To
investigate the influence of the microstructure on the magnetic behavior of
these samples, we used X-ray powder diffraction (XPD), transmission electron
microscopy (TEM), and vibrating sample magnetometry (VSM). The XPD analysis by
the Williamson-Hall plot was used to estimate the average crystallite size and
strain induced by mechanical milling in the samples
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