8,684 research outputs found
Asymmetric opening of HIV-1 Env bound to CD4 and a coreceptor-mimicking antibody
The human immunodeficiency virus (HIV-1) envelope (Env) glycoprotein, a (gp120âgp41)â trimer, mediates fusion of viral and host cell membranes after gp120 binding to host receptor CD4. Receptor binding triggers conformational changes allowing coreceptor (CCR5) recognition through CCR5âs tyrosine-sulfated amino (N) terminus, release of the gp41 fusion peptide and fusion. We present 3.3âĂ
and 3.5âĂ
cryo-EM structures of E51, a tyrosine-sulfated coreceptor-mimicking antibody, complexed with a CD4-bound open HIV-1 native-like Env trimer. Two classes of asymmetric Env interact with E51, revealing tyrosine-sulfated interactions with gp120 mimicking CCR5 interactions, and two conformations of gp120âgp41 protomers (A and B protomers in AAB and ABB trimers) that differ in their degree of CD4-induced trimer opening and induction of changes to the fusion peptide. By integrating the new structural information with previous closed and open envelope trimer structures, we modeled the order of conformational changes on the path to coreceptor binding site exposure and subsequent viralâhost cell membrane fusion
Dorsoventral differences in intrinsic properties in developing CA1 pyramidal cells.
The dorsoventral and developmental gradients of entorhinal layer II cell grid properties correlate with their resonance properties and with their hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channel current characteristics. We investigated whether such correlation existed in rat hippocampal CA1 pyramidal cells, where place fields also show spatial and temporal gradients. Resonance was absent during the first postnatal week, and emerged during the second week. Resonance was stronger in dorsal than ventral cells, in accord with HCN current properties. Resonance responded to cAMP in ventral but not in dorsal cells. The dorsoventral distribution of HCN1 and HCN2 subunits and of the auxiliary protein tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b) could account for these differences between dorsal and ventral cells. The analogous distribution of the intrinsic properties of entorhinal stellate and hippocampal cells suggests the existence of general rules of organization among structures that process complementary features of the environment
Miniaturized optical fiber Bragg grating sensor interrogator based on echelle diffractive gratings
An Optical fiber Bragg grating sensor interrogation device based on monolithically integrated echelle diffractive grating and detector arrays on an InP chip is designed and prototyped. The device weighs less than 60 g and measures smaller than 45 mm Ă 30 mm Ă 15 mm, and it is specifically designed for potential integration into aerospace applications. This study discusses this device's operation principle and presents some initial experimental results reflecting its performance
Layer thickness dependence of the current induced effective field vector in Ta|CoFeB|MgO
The role of current induced effective magnetic field in ultrathin magnetic
heterostructures is increasingly gaining interest since it can provide
efficient ways of manipulating magnetization electrically. Two effects, known
as the Rashba spin orbit field and the spin Hall spin torque, have been
reported to be responsible for the generation of the effective field. However,
quantitative understanding of the effective field, including its direction with
respect to the current flow, is lacking. Here we show vector measurements of
the current induced effective field in Ta|CoFeB|MgO heterostructrures. The
effective field shows significant dependence on the Ta and CoFeB layers'
thickness. In particular, 1 nm thickness variation of the Ta layer can result
in nearly two orders of magnitude difference in the effective field. Moreover,
its sign changes when the Ta layer thickness is reduced, indicating that there
are two competing effects that contribute to the effective field. The relative
size of the effective field vector components, directed transverse and parallel
to the current flow, varies as the Ta thickness is changed. Our results
illustrate the profound characteristics of just a few atomic layer thick metals
and their influence on magnetization dynamics
Integrating fluctuations into distribution of resources in transportation networks
We propose a resource distribution strategy to reduce the average travel time
in a transportation network given a fixed generation rate. Suppose that there
are essential resources to avoid congestion in the network as well as some
extra resources. The strategy distributes the essential resources by the
average loads on the vertices and integrates the fluctuations of the
instantaneous loads into the distribution of the extra resources. The
fluctuations are calculated with the assumption of unlimited resources, where
the calculation is incorporated into the calculation of the average loads
without adding to the time complexity. Simulation results show that the
fluctuation-integrated strategy provides shorter average travel time than a
previous distribution strategy while keeping similar robustness. The strategy
is especially beneficial when the extra resources are scarce and the network is
heterogeneous and lowly loaded.Comment: 14 pages, 4 figure
Differential dorso-ventral distributions of Kv4.2 and HCN proteins confer distinct integrative properties to hippocampal CA1 pyramidal cell distal dendrites.
The dorsal and ventral regions of the hippocampus perform different functions. Whether the integrative properties of hippocampal cells reflect this heterogeneity is unknown. We focused on dendrites where most synaptic input integration takes place. We report enhanced backpropagation and theta resonance and decreased summation of synaptic inputs in ventral versus dorsal CA1 pyramidal cell distal dendrites. Transcriptional Kv4.2 down-regulation and post-transcriptional hyperpolarization-activated cyclic AMP-gated channel (HCN1/2) up-regulation may underlie these differences, respectively. Our results reveal differential dendritic integrative properties along the dorso-ventral axis, reflecting diverse computational needs
Power-referenced and self-calibrated PM-FBG vibroscope
A compact vibration sensing probe, in which a short section of polarization-maintained (PM) fiber stub containing a normal straight fiber Bragg grating (FBG) is spliced to another single-mode fiber without any lateral offset, is proposed and experimentally demonstrated. Two groups of well-defined resonances with ~ 7 nm wavelength separation have been achieved in reflection. Among them, the recoupled cladding modes at short wavelength side are extremely sensitive to fiber bending and provide the real-time vibration information by cost-effective power detection. Meanwhile, the unwanted power fluctuations and temperature perturbations can be referenced out by monitoring the core mode resonances at the longest wavelength.Department of Electrical EngineeringRefereed conference pape
Power-referenced and self-calibrated PM-FBG vibroscope
2012-2013 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe
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