G-133: A soft x ray solar telescope

The GOLDHELOX Project, NASA payload number G-133, is a robotic soft x ray solar telescope designed and built by an organization of undergraduate students. The telescope is designed to observe the sun at a wavelength of 171 to 181 A. Since we require observations free from atmospheric interference, the telescope will be launched in a NASA Get-Away-Special (GAS) canister with a Motorized Door Assembly (MDA). In this paper we primarily discuss the most important elements of the telescope itself. We also elaborate on some of the technical difficulties associated with doing good science in space on a small budget (about $100,000) and mention ways in which controlling the instrument environment has reduced the complexity of the system and thus saved us money

Total synthesis of the post-translationally modified polyazole peptide antibiotic plantazolicin A

The power of rhodium carbene methodology in chemistry is demonstrated by the synthesis of a structurally complex polyazole antibiotic. Plantazolicin A, a novel soil bacterium metabolite, comprises a linear array of 10 five-membered rings in two pentacyclic regions that derive from ribosomal peptide synthesis followed by extensive post-translational modification. The compound possesses potent antimicrobial activity, and is selectively active against the anthrax causing organism. A conceptually different synthesis of plantazolicin A is reported in which the key steps are the use of rhodium(II)-catalyzed reactions of diazocarbonyl compounds to generate up to six of the seven oxazole rings of the antibiotic. NMR Spectroscopic studies and molecular modeling, reveal a likely dynamic hairpin conformation with a hinge region around the two isoleucine residues.The compound has modest activity against methicillin-resistant Staphylococcus aureus (MRSA)

SNX27–Retromer directly binds ESCPE-1 to transfer cargo proteins during endosomal recycling

Coat complexes coordinate cargo recognition through cargo adaptors with biogenesis of transport carriers during integral membrane protein trafficking. Here, we combine biochemical, structural, and cellular analyses to establish the mechanistic basis through which SNX27-Retromer, a major endosomal cargo adaptor, couples to the membrane remodeling endosomal SNX-BAR sorting complex for promoting exit 1 (ESCPE-1). In showing that the SNX27 FERM (4.1/ezrin/radixin/moesin) domain directly binds acidic-Asp-Leu-Phe (aDLF) motifs in the SNX1/SNX2 subunits of ESCPE-1, we propose a handover model where SNX27-Retromer captured cargo proteins are transferred into ESCPE-1 transport carriers to promote endosome-to-plasma membrane recycling. By revealing that assembly of the SNX27:Retromer:ESCPE-1 coat evolved in a stepwise manner during early metazoan evolution, likely reflecting the increasing complexity of endosome-to-plasma membrane recycling from the ancestral opisthokont to modern animals, we provide further evidence of the functional diversification of yeast pentameric Retromer in the recycling of hundreds of integral membrane proteins in metazoans

Four-wave-mixing microscopy reveals non-colocalisation between gold nanoparticles and fluorophore conjugates inside cells

Gold nanoparticles have been researched for many biomedical applications in diagnostics, theranostics, and as drug delivery systems. When conjugated to fluorophores, their interaction with biological cells can be studied in situ and real time using fluorescence microscopy. However, an important question that has remained elusive to answer is whether the fluorophore is a faithful reporter of the nanoparticle location. Here, our recently developed four-wave-mixing optical microscopy is applied to image individual gold nanoparticles and in turn investigate their co-localisation with fluorophores inside cells. Nanoparticles from 10 nm to 40 nm diameter were conjugated to fluorescently-labeled transferrin, for internalisation via clathrin-mediated endocytosis, or to non-targeting fluorescently-labelled antibodies. Human (HeLa) and murine (3T3-L1) cells were imaged at different time points after incubation with these conjugates. Our technique identified that, in most cases, fluorescence originated from unbound fluorophores rather than from fluorophores attached to nanoparticles. Fluorescence detection was also severely limited by photobleaching, quenching and autofluorescence background. Notably, correlative extinction/fluorescence microscopy of individual particles on a glass surface indicated that commercial constructs contain large amounts of unbound fluorophores. These findings highlight the potential problems of data interpretation when reliance is solely placed on the detection of fluorescence within the cell, and are of significant importance in the context of correlative light electron microscopy

Measuring Reaction Probability Ratios to Simulate Neutron-Induced Cross-sections of Short-Lived Nuclei

Measuring the neutron-induced fission cross-sections of short-lived nuclei represents an experimental challenge due to target activity and the low intensity of neutron beams. One way to alleviate the problems inherent in the direct measurement is to use the surrogate method, where one measures the decay probability of the same compound nucleus formed using a charged beam and a stable target. The decay probability of the compound nucleus is then used to estimate the neutron-induced cross-section. As an extension to the surrogate method, we introduce a new method of reporting the fission probabilities of two compound nuclei as a ratio, which has the advantage of removing most of the systematic uncertainties. The ratio method was checked in a known case, the 236U (n, f) /238U (n, f) cross-section ratio, which turned out to be the same as the probability ratio of P (236U (d, pf))/P (238U (d, pf)). As an application, the 237U(n, f )/235U(n, f ) cross-section ratio was inferred, on the basis of the measured P(238U(d, d f ))/P (236U(d, d f )) probability ratio

Estimation of (\u3cem\u3en, f\u3c/em\u3e) Cross Sections by Measuring Reaction Probability Ratios

Neutron-induced reaction cross sections on unstable nuclei are inherently difficult to measure due to target activity and the low intensity of neutron beams. In an alternative approach, named the “surrogate” technique, one measures the decay probability of the same compound nucleus produced using a stable beam on a stable target to estimate the neutron-induced reaction cross section. As an extension of the surrogate method, in this paper we introduce a new technique of measuring the fission probabilities of two different compound nuclei as a ratio, which has the advantage of removing most of the systematic uncertainties. This method was benchmarked in this report by measuring the probability of deuteron-induced fission events in coincidence with protons, and forming the ratio P[236U(d,pf)]/P [238U(d,pf)], which serves as a surrogate for the known cross section ratio of 236U(n, f)/238U(n, f). In addition, the P[238U(d, d f)]/P [236U(d, df)] ratio as a surrogate for the 237U(n, f)/235U(n, f) cross section ratio was measured for the first time in an unprecedented range of excitation energies

Estimation of (\u3cem\u3en, f\u3c/em\u3e) Cross Sections by Measuring Reaction Probability Ratios

Neutron-induced reaction cross sections on unstable nuclei are inherently difficult to measure due to target activity and the low intensity of neutron beams. In an alternative approach, named the “surrogate” technique, one measures the decay probability of the same compound nucleus produced using a stable beam on a stable target to estimate the neutron-induced reaction cross section. As an extension of the surrogate method, in this paper we introduce a new technique of measuring the fission probabilities of two different compound nuclei as a ratio, which has the advantage of removing most of the systematic uncertainties. This method was benchmarked in this report by measuring the probability of deuteron-induced fission events in coincidence with protons, and forming the ratio P[236U(d,pf)]/P [238U(d,pf)], which serves as a surrogate for the known cross section ratio of 236U(n, f)/238U(n, f). In addition, the P[238U(d, d f)]/P [236U(d, df)] ratio as a surrogate for the 237U(n, f)/235U(n, f) cross section ratio was measured for the first time in an unprecedented range of excitation energies