3,295 research outputs found
Site-selective protein modification via disulfide rebridging for fast tetrazine/trans-cyclooctene bioconjugation
An inverse electron demand DielsâAlder reaction between tetrazine and trans-cyclooctene (TCO) holds great promise for protein modification and manipulation. Herein, we report the design and synthesis of a tetrazine-based disulfide rebridging reagent, which allows the site-selective installation of a tetrazine group into disulfide-containing peptides and proteins such as the hormone somatostatin (SST) and the antigen binding fragment (Fab) of human immunoglobulin G (IgG). The fast and efficient conjugation of the tetrazine modified proteins with three different TCO-containing substrates to form a set of bioconjugates in a site-selective manner was successfully demonstrated for the first time. Homogeneous, well-defined bioconjugates were obtained underlining the great potential of our method for fast bioconjugation in emerging protein therapeutics. The formed bioconjugates were stable against glutathione and in serum, and they maintained their secondary structure. With this work, we broaden the scope of tetrazine chemistry for site-selective protein modification to prepare well-defined SST and Fab conjugates with preserved structures and good stability under biologically relevant conditions
Manipulating the magnetic state of a carbon nanotube Josephson junction using the superconducting phase
The magnetic state of a quantum dot attached to superconducting leads is
experimentally shown to be controlled by the superconducting phase difference
across the dot. This is done by probing the relation between the Josephson
current and the superconducting phase difference of a carbon nanotube junction
whose Kondo energy and superconducting gap are of comparable size. It exhibits
distinctively anharmonic behavior, revealing a phase mediated singlet to
doublet transition. We obtain an excellent quantitative agreement with
numerically exact quantum Monte Carlo calculations. This provides strong
support that we indeed observed the finite temperature signatures of the phase
controlled zero temperature level-crossing transition originating from strong
local electronic correlations.Comment: 5 pages, 4 figures + supp. material
Angular Momentum Profiles of Warm Dark Matter Halos
We compare the specific angular momentum profiles of virialized dark halos in
cold dark matter (CDM) and warm dark matter (WDM) models using high-resolution
dissipationless simulations. The simulations were initialized using the same
set of modes, except on small scales, where the power was suppressed in WDM
below the filtering length. Remarkably, WDM as well as CDM halos are
well-described by the two-parameter angular momentum profile of Bullock et al.
(2001), even though the halo masses are below the filtering scale of the WDM.
Although the best-fit shape parameters change quantitatively for individual
halos in the two simulations, we find no systematic variation in profile shapes
as a function of the dark matter type. The scatter in shape parameters is
significantly smaller for the WDM halos, suggesting that substructure and/or
merging history plays a role producing scatter about the mean angular momentum
distribution, but that the average angular momentum profiles of halos originate
from larger-scale phenomena or a mechanism associated with the virialization
process. The known mismatch between the angular momentum distributions of dark
halos and disk galaxies is therefore present in WDM as well as CDM models. Our
WDM halos tend to have a less coherent (more misaligned) angular momentum
structure and smaller spin parameters than do their CDM counterparts, although
we caution that this result is based on a small number of halos.Comment: 5 pages, 1 figure, Submitted to ApJ
Mg II Absorption Systems in SDSS QSO Spectra
We present the results of a MgII absorption-line survey using QSO spectra
from the SDSS EDR. Over 1,300 doublets with rest equivalent widths greater than
0.3\AA and redshifts were identified and measured. We
find that the rest equivalent width ()
distribution is described very well by an exponential function , with
and \AA. Previously reported power law
fits drastically over-predict the number of strong lines. Extrapolating our
exponential fit under-predicts the number of \AA systems,
indicating a transition in near \AA. A combination of
two exponentials reproduces the observed distribution well, suggesting that
MgII absorbers are the superposition of at least two physically distinct
populations of absorbing clouds. We also derive a new redshift parameterization
for the number density of \AA lines:
and \AA. We find that the distribution steepens with decreasing redshift,
with decreasing from \AA at to \AA at
. The incidence of moderately strong MgII lines does not
show evidence for evolution with redshift. However, lines stronger than
\AA show a decrease relative to the no-evolution prediction with
decreasing redshift for . The evolution is stronger for
increasingly stronger lines. Since in saturated absorption lines is an
indicator of the velocity spread of the absorbing clouds, we interpret this as
an evolution in the kinematic properties of galaxies from moderate to low z.Comment: 50 pages, 26 figures, accepted for publication in Ap
On integration of the Kowalevski gyrostat and the Clebsch problems
For the Kowalevski gyrostat change of variables similar to that of the
Kowalevski top is done. We establish one to one correspondence between the
Kowalevski gyrostat and the Clebsch system and demonstrate that Kowalevski
variables for the gyrostat practically coincide with elliptic coordinates on
sphere for the Clebsch case. Equivalence of considered integrable systems
allows to construct two Lax matrices for the gyrostat using known rational and
elliptic Lax matrices for the Clebsch model. Associated with these matrices
solutions of the Clebsch system and, therefore, of the Kowalevski gyrostat
problem are discussed. The Kotter solution of the Clebsch system in modern
notation is presented in detail.Comment: LaTeX, 24 page
Thoracic duct fistula and renal transplantation
Thoracic duct drainage (TDD) was established for 21-115 days in 40 kidney recipients with an average removal per patient day of 4.7 1 lymph and 1.88 billion cells. Cellular and humoral immunity were depressed. TDD and immunosuppressive drugs were started at transplantation in 35 recipients of cross-match negative grafts. Although the results were better than in precedent non-TDD controls, eight patients rejected their grafts before a full TDD effect, and three of the eight developed predominantly anti-B lymphocyte cytotoxic antibodies which were probably responsible for positive cross-matches with their next donors. With continuing TDD, all eight patients had good initial function after early retransplantation. In five more 'nontransplantable' patients with performed cytotoxic antibodies, TDD was started 30-56 days before transplantation. In these five pretreated patients, antibodies persisted with positive antidonor cross-matches. Hyperacute rejection occurred repeatedly in two patients with high anti-T (and anti-B) titers, but was surmounted in three patients with lower titers. From the clinical and immunologic data, we have concluded that TDD should be used for pretreatment of all cases with or without prior antibodies, and have suggested an adjustable management plan that takes into account new developments in antibody monitoring
On Foundation of the Generalized Nambu Mechanics
We outline the basic principles of canonical formalism for the Nambu
mechanics---a generalization of Hamiltonian mechanics proposed by Yoichiro
Nambu in 1973. It is based on the notion of Nambu bracket which generalizes the
Poisson bracket to the multiple operation of higher order on
classical observables and is described by Hambu-Hamilton equations of motion
given by Hamiltonians. We introduce the fundamental identity for the
Nambu bracket which replaces Jacobi identity as a consistency condition for the
dynamics. We show that Nambu structure of given order defines a family of
subordinated structures of lower order, including the Poisson structure,
satisfying certain matching conditions. We introduce analogs of action from and
principle of the least action for the Nambu mechanics and show how dynamics of
loops (-dimensional objects) naturally appears in this formalism. We
discuss several approaches to the quantization problem and present explicit
representation of Nambu-Heisenberg commutation relation for case. We
emphasize the role higher order algebraic operations and mathematical
structures related with them play in passing from Hamilton's to Nambu's
dynamical picture.Comment: 27 page
On compression of Bruhat-Tits buildings
We obtain an analog of the compression of angles theorem in symmetric spaces
for Bruhat--Tits buildings of the type .
More precisely, consider a -adic linear space and the set of
all lattices in . The complex distance in is a complete system of
invariants of a pair of points of under the action of the complete
linear group. An element of a Nazarov semigroup is a lattice in the duplicated
linear space . We investigate behavior of the complex distance under
the action of the Nazarov semigroup on the set .Comment: 6 page
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