Field quality of quadrupole R&D models for the LHC IR

Superconducting quadrupole magnets operating in superfluid helium at 1.9 K, with 70 mm bore and nominal field gradient of 205 T/m at collision optics, are being developed by the US LHC Accelerator Project for the Interaction Regions of the Large Hadron Collider (LHC). A magnet model program to validate and optimize the design is underway. This paper reports results of field quality measurements of four model magnets. (3 refs)

Quench performance of Fermilab high gradient quadrupole short models for the LHC Interaction Regions

Fermilab and LBNL are in the midst of superconducting magnet R&D program to test and optimize the design of quadrupoles to be used in the LHC Interaction Region inner triplets. The magnets are required to deliver a 215 T/m gradient across a 70 mm aperture. Five quadrupole short models have been fabricated and four of them have been tested. This paper describes the last model design details and reports the results of the magnet quench performance study. (5 refs)

Quench Performance of Fermilab High Gradient Quadrupole Short Models for the LHC Interaction Regions

Abstract Fermilab and LBNL are in the midst of a superconducting magnet R&D program to test and optimize the design of quadrupoles to be used in the LHC Interaction Region inner triplets. The magnets are required to deliver a 215 T/m gradient across a 70mm aperture. Five quadrupole short models have been fabricated and four of them have been tested. This paper describes the last model design details and reports the results of the magnet quench performance study

Metabolic Regulation of Invadopodia and Invasion by Acetyl-CoA Carboxylase 1 and De novo Lipogenesis

Invadopodia are membrane protrusions that facilitate matrix degradation and cellular invasion. Although lipids have been implicated in several aspects of invadopodia formation, the contributions of de novo fatty acid synthesis and lipogenesis have not been defined. Inhibition of acetyl-CoA carboxylase 1 (ACC1), the committed step of fatty acid synthesis, reduced invadopodia formation in Src-transformed 3T3 (3T3-Src) cells, and also decreased the ability to degrade gelatin. Inhibition of fatty acid synthesis through AMP-activated kinase (AMPK) activation and ACC phosphorylation also decreased invadopodia incidence. The addition of exogenous 16∶0 and 18∶1 fatty acid, products of de novo fatty acid synthesis, restored invadopodia and gelatin degradation to cells with decreased ACC1 activity. Pharmacological inhibition of ACC also altered the phospholipid profile of 3T3-Src cells, with the majority of changes occurring in the phosphatidylcholine (PC) species. Exogenous supplementation with the most abundant PC species, 34∶1 PC, restored invadopodia incidence, the ability to degrade gelatin and the ability to invade through matrigel to cells deficient in ACC1 activity. On the other hand, 30∶0 PC did not restore invadopodia and 36∶2 PC only restored invadopodia incidence and gelatin degradation, but not cellular invasion through matrigel. Pharmacological inhibition of ACC also reduced the ability of MDA-MB-231 breast, Snb19 glioblastoma, and PC-3 prostate cancer cells to invade through matrigel. Invasion of PC-3 cells through matrigel was also restored by 34∶1 PC supplementation. Collectively, the data elucidate the novel metabolic regulation of invadopodia and the invasive process by de novo fatty acid synthesis and lipogenesis

Retroviral matrix and lipids, the intimate interaction

Retroviruses are enveloped viruses that assemble on the inner leaflet of cellular membranes. Improving biophysical techniques has recently unveiled many molecular aspects of the interaction between the retroviral structural protein Gag and the cellular membrane lipids. This interaction is driven by the N-terminal matrix domain of the protein, which probably undergoes important structural modifications during this process, and could induce membrane lipid distribution changes as well. This review aims at describing the molecular events occurring during MA-membrane interaction, and pointing out their consequences in terms of viral assembly. The striking conservation of the matrix membrane binding mode among retroviruses indicates that this particular step is most probably a relevant target for antiviral research

Structural basis for a unique ATP synthase core complex from nanoarcheaum equitans

Background: Structural asymmetry upon nucleotide binding is crucial for catalytic activity of ATP synthases. Results: The structures of apo and bound A3B3 hexamer of N. equitans ATP synthase show conformational inflexibility. Conclusion: The N. equitans A3B3 hexamer is an inactive form. Significance: The structure of inactive form of N. equitans ATP synthase A3B3 is shown for the first time.Peer Reviewe

Structural basis for the interaction of unstructured neuron specific substrates neuromodulin and neurogranin with calmodulin

9 pags, 6 figs, 2 tabs. -- Supplementary information is available at the Publisher's webNeuromodulin (Nm) and neurogranin (Ng) are neuron-specific substrates of protein kinase C (PKC). Their interactions with Calmodulin (CaM) are crucial for learning and memory formation in neurons. Here, we report the structure of IQ peptides (24aa) of Nm/Ng complexed with CaM and their functional studies with full-length proteins. Nm/Ng and their respective IQ peptides are intrinsically unstructured; however, upon binding with CaM, IQ motifs adopt a helical conformation. Ser41 (Ser36) of Nm (Ng) is located in a negatively charged pocket in the apo CaM and, when phosphorylated, it will repel Nm/Ng from CaM. These observations explain the mechanism by which PKC-induced Ser phosphorylation blocks the association of Nm/Ng with CaM and interrupts several learning-and memory-associated functions. Moreover, the present study identified Arg as a key CaM interacting residue from Nm/Ng. This residue is crucial for CaM-mediated function, as evidenced by the inability of the Ng mutant (Arg-to-Ala) to potentiate synaptic transmission in CA1 hippocampal neurons.We are grateful to the Biomedical Research Council of Singapore (BMRC), A*STAR, (R154000461305) and AcRF (Tier 1) National University of Singapore (NUS), for the partial support of this study. NZG was supported by grants from US National Institute on Aging (AG032320) and Alzheimer’s Association. FWS was supported by Ministry of Education, Singapore (R-154-000-228-112). X-ray diffraction data for this study were measured at beamline 13B1 of National Synchrotron Radiation Research Centre (NSRRC), Taiwan, and BNL New York, USA. We also acknowledge Yi-Hui Chen from NSRRC for her assistance during data collection. Veerendra Kumar is a graduate scholar in receipt of a research scholarship from the NUS and from R-154-000-228-112

Mechanical design and performance of the Fermilab high gradient quadrupole model magnets for the LHC interaction regions

The mechanical design of the Fermilab high gradient quadrupole (HGQ) magnet cold mass is presented, along with its expected behavior and performance under fabrication and operational conditions. Coil stresses, end forces and $9 collared coil diameter measurements obtained during fabrication and cryogenic testing are also presented, and are discussed in the context of expected behavior and feedback into the design. (10 refs)

Large Aperture Nb3_{3}Sn Quadrupoles for 2nd Generation LHC IRs

The 1/sup st/ generation of low-beta quadrupoles for the LHC interaction region (IR) was designed to achieve the nominal LHC luminosity of 10/sup 34/ cm/sup -2/s/sup -1/. Given that the lifetime of the 1/sup st/ generation IR quadrupoles is limited by ionizing radiation to 6-7 years, the 2/sup nd/ generation of IR quadrupoles has to be developed with the goal to achieve the ultimate luminosity up to 10/sup 35/ cm/sup -2/s/sup -1/. The IR quadrupole parameters such as nominal gradient, dynamic aperture and physical aperture, operation margins are the main factors limiting the machine performance. Conceptual designs of 90-mm aperture high-gradient quadrupoles, suitable for use in 2/sup nd/ generation high-luminosity LHC IRs with the similar optics, are presented. The issues related to the field gradient, field quality and operation margins are discussed. (5 refs)