Roles of ADAM10 and 17 in the shedding of LRP1 in human macrophages

The inflammatory cytokine TNF has a central role in regulating the inflammatory response, and prolonged TNF release is observed in many chronic inflammatory diseases. The endocytic scavenger receptor LRP1 is involved in regulating TNF release from macrophages via the TIMP-3/ADAM17 axis. LRP1 can be shed from macrophages leading to an accumulation of TIMP-3, which inhibits ADAM17, and subsequently inhibits TNF release. In this thesis I aimed to investigate how LRP1 was shed from human macrophages in response to inflammatory stimuli and which protease(s) were responsible for this shedding. I first investigated LRP1 shedding in THP-1 and U937 human monocytic cell lines. However, as I was unable to detect shed LRP1 from U937 cells, and THP-1 cells were insensitive to LPS stimulation, I concluded that neither cell line was an appropriate model system for my investigations. I next tested primary human monocyte-derived macrophages isolated from peripheral blood. Using these cells, I was able to detect constitutive LRP1 shedding after 2 hours of culture and LPS-stimulated LRP1 shedding after 6 hours of stimulation. I used various protease inhibitors and blocking antibodies to target individual proteases to investigate which protease(s) were involved. I found that none of the broad specificity protease inhibitors significantly decreased LPS-stimulated LRP1 shedding and that a specific inhibitory blocking antibody against ADAM17 also had no effect. However, selective inhibition of ADAM10 inhibited both the constitutive and LPS-stimulated shedding of LRP1. Furthermore, I observed that activation of ADAM10 increased LRP1 shedding. In conclusion, I have found that ADAM10 plays a key role in both the constitutive and stimulated shedding of LRP1 from human macrophages. Therefore, ADAM10 is involved in controlling the resolution of the inflammatory response by shedding LRP1 from macrophages to inhibit the continued release of TNF, which might otherwise result in chronic inflammation

One-second coherence for a single electron spin coupled to a multi-qubit nuclear-spin environment

Single electron spins coupled to multiple nuclear spins provide promising multi-qubit registers for quantum sensing and quantum networks. The obtainable level of control is determined by how well the electron spin can be selectively coupled to, and decoupled from, the surrounding nuclear spins. Here we realize a coherence time exceeding a second for a single electron spin through decoupling sequences tailored to its microscopic nuclear-spin environment. We first use the electron spin to probe the environment, which is accurately described by seven individual and six pairs of coupled carbon-13 spins. We develop initialization, control and readout of the carbon-13 pairs in order to directly reveal their atomic structure. We then exploit this knowledge to store quantum states for over a second by carefully avoiding unwanted interactions. These results provide a proof-of-principle for quantum sensing of complex multi-spin systems and an opportunity for multi-qubit quantum registers with long coherence times

Full stress tensor measurement using colour centres in diamond

Stress and strain are important factors in determining the mechanical, electronic, and optical properties of materials, relating to each other by the material's elasticity or stiffness. Both are represented by second rank field tensors with, in general, six independent components. Measurements of these quantities are usually achieved by measuring a property that depends on the translational symmetry and periodicity of the crystal lattice, such as optical phonon energies using Raman spectroscopy, the electronic band gap using cathodoluminescence, photoelasticity via the optical birefringence, or Electron Back Scattering Diffraction (EBSD). A reciprocal relationship therefore exists between the maximum sensitivity of the measurements and the spatial resolution. Furthermore, of these techniques, only EBSD and off-axis Raman spectroscopy allow measurement of all six components of the stress tensor, but neither is able to provide full 3D maps. Here we demonstrate a method for measuring the full stress tensor in diamond, using the spectral and optical polarization properties of the photoluminescence from individual nitrogen vacancy (NV) colour centres. We demonstrate a sensitivity of order 10 MPa, limited by local fluctuations in the stress in the sample, and corresponding to a strain of about 10^-5, comparable with the best sensitivity provided by other techniques. By using the colour centres as built-in local sensors, the technique overcomes the reciprocal relationship between spatial resolution and sensitivity and offers the potential for measuring strains as small as 10^-9 at spatial resolution of order 10 nm. Furthermore it provides a straightforward route to volumetric stress mapping. Aside from its value in understanding strain distributions in diamond, this new approach to stress and strain measurement could be adapted for use in micro or nanoscale sensors.Comment: 12 pages, 5 figures - supplementary informations included in appendi

Robust quantum-network memory using decoherence-protected subspaces of nuclear spins

The realization of a network of quantum registers is an outstanding challenge in quantum science and technology. We experimentally investigate a network node that consists of a single nitrogen-vacancy (NV) center electronic spin hyperfine-coupled to nearby nuclear spins. We demonstrate individual control and readout of five nuclear spin qubits within one node. We then characterize the storage of quantum superpositions in individual nuclear spins under repeated application of a probabilistic optical inter-node entangling protocol. We find that the storage fidelity is limited by dephasing during the electronic spin reset after failed attempts. By encoding quantum states into a decoherence-protected subspace of two nuclear spins we show that quantum coherence can be maintained for over 1000 repetitions of the remote entangling protocol. These results and insights pave the way towards remote entanglement purification and the realisation of a quantum repeater using NV center quantum network nodes