38 research outputs found
Yeast prion protein derivative defective in aggregate shearing and production of new ‘seeds’
According to the nucleated polymerization model, in vivo prion proliferation occurs via dissociation (shearing) of the huge prion polymers into smaller oligomeric ‘seeds’, initiating new rounds of prion replication. Here, we identify the deletion derivative of yeast prion protein Sup35 (Sup35-Δ22/69) that is specifically defective in aggregate shearing and ‘seed’ production. This derivative, [PSI(+)], previously thought to be unable to turn into a prion state, in fact retains the ability to form a prion ([PSI(+)](Δ)(22/69)) that can be maintained in selective conditions and transmitted by cytoplasmic infection (cytoduction), but which is mitotically unstable in non-selective conditions. MorePSI(+)](Δ)(22/69) retains its mitotic stability defect. The [PSI(+)](Δ)(22/69) cells contain more Sup35 protein in the insoluble fraction and form larger Sup35 aggregates compared with the conventional [PSI(+)] cells. Moderate excess of Hsp104 disaggregase increases transmission of the [PSI(+)](Δ)(22/69) prion, while excess Hsp70-Ssa chaperone antagonizes it, opposite to their effects on conventional [PSI(+)]. Our results shed light on the mechanisms determining the differences between transmissible prions and non-transmissible protein aggregates
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High-current Y-Ba-Cu-O-coated conductor using metal organic chemical-vapor deposition and ion-beam-assisted deposition.
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The Los Alamos POP Project: FEL oscillator experiments in the ultraviolet and beyond
The Los Alamos POP Project will include a series of proof-of-principle FEL oscillator experiments in 1992 designed to extend FEL operation into the ultraviolet (UV) and vacuum ultraviolet (VUV). With beam energy extended to 50 MeV, enhanced beam brightness with a photoinjector, and appropriate UV and VUV resonator optics, the Los Alamos FEL oscillator should have sufficient single-pass gain (20--30%) to reach below 200 nm. The first goal will be lasing at 250 nm utilizing a permanent-magnet undulator with 5-mm period or alternatively on the third harmonic with a 1-cm period. To operate at VUV wavelengths of 200 and 150 nm (third harmonic), pulsed electromagnetic microwigglers with periods of 5.7- and 4.3 mm will be employed. 23 refs
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The Los Alamos POP Project: FEL oscillator experiments in the ultraviolet and beyond
The Los Alamos POP Project will include a series of proof-of-principle FEL oscillator experiments in 1992 designed to extend FEL operation into the ultraviolet (UV) and vacuum ultraviolet (VUV). With beam energy extended to 50 MeV, enhanced beam brightness with a photoinjector, and appropriate UV and VUV resonator optics, the Los Alamos FEL oscillator should have sufficient single-pass gain (20--30%) to reach below 200 nm. The first goal will be lasing at 250 nm utilizing a permanent-magnet undulator with 5-mm period or alternatively on the third harmonic with a 1-cm period. To operate at VUV wavelengths of 200 and 150 nm (third harmonic), pulsed electromagnetic microwigglers with periods of 5.7- and 4.3 mm will be employed. 23 refs