751 research outputs found
Modifying the Steric Properties in the Second Coordination Sphere of Designed Peptides Leads to Enhancement of Nitrite Reductase Activity
Protein design is a useful strategy to interrogate the protein structureâ function relationship. We demonstrate using a highly modular 3â stranded coiled coil (TRIâ peptide system) that a functional typeâ 2 copper center exhibiting copper nitrite reductase (NiR) activity exhibits the highest homogeneous catalytic efficiency under aqueous conditions for the reduction of nitrite to NO and H2O. Modification of the amino acids in the second coordination sphere of the copper center increases the nitrite reductase activity up to 75â fold compared to previously reported systems. We find also that steric bulk can be used to enforce a threeâ coordinate CuI in a site, which tends toward twoâ coordination with decreased steric bulk. This study demonstrates the importance of the second coordination sphere environment both for controlling metalâ center ligation and enhancing the catalytic efficiency of metalloenzymes and their analogues.Second is best: A significant increase in nitrite reductase activity is achieved by modification of the steric properties of the second coordination sphere of a typeâ 2 copper center. The steric properties can be harnessed to control metal coordination and reactivity in a 3â stranded coiled coil TRI peptide scaffold (TRIWâ H).Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142897/1/anie201712757.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142897/2/anie201712757-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142897/3/anie201712757_am.pd
Modifying the Steric Properties in the Second Coordination Sphere of Designed Peptides Leads to Enhancement of Nitrite Reductase Activity
Protein design is a useful strategy to interrogate the protein structureâ function relationship. We demonstrate using a highly modular 3â stranded coiled coil (TRIâ peptide system) that a functional typeâ 2 copper center exhibiting copper nitrite reductase (NiR) activity exhibits the highest homogeneous catalytic efficiency under aqueous conditions for the reduction of nitrite to NO and H2O. Modification of the amino acids in the second coordination sphere of the copper center increases the nitrite reductase activity up to 75â fold compared to previously reported systems. We find also that steric bulk can be used to enforce a threeâ coordinate CuI in a site, which tends toward twoâ coordination with decreased steric bulk. This study demonstrates the importance of the second coordination sphere environment both for controlling metalâ center ligation and enhancing the catalytic efficiency of metalloenzymes and their analogues.Erstklassiges aus der zweiten Reihe: Die Aktivität der Nitritreduktase kann durch Modifikation der sterischen Eigenschaften in der zweiten Koordinationssphäre eines Typâ 2â Kupferzentrums deutlich erhöht werden. à ber die Sterik lassen sich die Koordination und Reaktivität des Metalls in einem dreisträngigen â Coiledâ coilâ â TRIâ Peptidgerüst (TRIWâ H) vorgeben.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142882/1/ange201712757_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142882/2/ange201712757-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142882/3/ange201712757.pd
Cold-atom clock based on a diffractive optic
Clocks based on cold atoms offer unbeatable accuracy and long-term stability, but their use in portable quantum technologies is hampered by a large physical footprint. Here, we use the compact optical layout of a grating magneto-optical trap (gMOT) for a precise frequency reference. The gMOT collects 10 7 87Rb atoms, which are subsequently cooled to 20 µK in optical molasses. We optically probe the microwave atomic ground-state splitting using lin┴lin polarised coherent population trapping and a Raman-Ramsey sequence. With ballistic drop distances of only 0.5 mm, the measured short-term fractional frequency stability is 2 × 10 −11/√τ
Primordial non-Gaussianity with Angular correlation function: Integral constraint and validation for DES
Local primordial non-Gaussianity (PNG) is a promising observable of the
underlying physics of inflation, characterised by . We
present the methodology to measure from the Dark Energy
Survey (DES) data using the 2-point angular correlation function (ACF) with
scale-dependent bias. One of the focuses of the work is the integral
constraint. This condition appears when estimating the mean number density of
galaxies from the data and is key in obtaining unbiased
constraints. The methods are analysed for two types of simulations:
GOLIAT-PNG N-body small area simulations with equal to -100 and
100, and 1952 Gaussian ICE-COLA mocks with that follow the DES
angular and redshift distribution. We use the ensemble of GOLIAT-PNG mocks to
show the importance of the integral constraint when measuring PNG, where we
recover the fiducial values of within the when including
the integral constraint. In contrast, we found a bias of when not including it. For a DES-like scenario, we forecast a bias of
, equivalent to , when not using the IC
for a fiducial value of . We use the ICE-COLA mocks to validate
our analysis in a realistic DES-like setup finding it robust to different
analysis choices: best-fit estimator, the effect of IC, BAO damping,
covariance, and scale choices. We forecast a measurement of within
when using the DES-Y3 BAO sample, with the ACF in the
range.Comment: Version after MNRAS reviewer comments. Improved discussion in Section
7. 16 pages, 11 figure
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