75 research outputs found
Evidence for bipolar jets in late stages of AGB winds
Bipolar expansion at various stages of evolution has been recently observed
in a number of AGB stars. The expansion is driven by bipolar jets that emerge
late in the evolution of AGB winds. The wind traps the jets, resulting in an
expanding, elongated cocoon. Eventually the jets break-out from the confining
spherical wind, as recently observed in W43A. This source displays the most
advanced evolutionary stage of jets in AGB winds. The earliest example is
IRC+10011, where the asymmetry is revealed in high-resolution near-IR imaging.
In this source the jets turned on only ~200 years ago, while the spherical wind
is ~4000 years old.Comment: 6 pages, to appear in "Asymmetrical Planetary Nebulae III" editors M.
Meixner, J. Kastner, N. Soker, & B. Balick (ASP Conf. Series
An artificial CO-releasing metalloprotein built by histidine-selective metallation.
We report the design and synthesis of an aquacarbonyl Ru(II) dication cis-[Ru(CO)2(H2O)4](2+) reagent for histidine (His)-selective metallation of interleukin (IL)-8 at site 33. The artificial, non-toxic interleukin (IL)-8-Ru(II)(CO)2 metalloprotein retained IL-8-dependent neutrophil chemotactic activity and was shown to spontaneously release CO in live cells.We thank the European Commission (Marie Curie CIG to
G.J.L.B., Marie Curie IEF to O.B.), FCT Portugal (FCT Investigator
to G.J.L.B.) and the EPSRC for generous funding.This is the final published version. It first appeared at http://pubs.rsc.org/en/Content/ArticleLanding/2015/CC/c4cc10204e#!divAbstract
Effect of DMSO on Protein Structure and Interactions Assessed by Collision-Induced Dissociation and Unfolding
Given the frequent use of DMSO in biochemical and biophysical assays, it is desirable to understand the influence of DMSO concentration on the dissociation or unfolding behavior of proteins. In this study, the effects of DMSO on the structure and interactions of avidin and Mycobacterium tuberculosis (Mtb) CYP142A1 were assessed through collision-induced dissociation (CID) and collision-induced unfolding (CIU) as monitored by nanoelectrospray ionizationâion mobilityâmass spectrometry (nESI-IM-MS). DMSO concentrations higher than 4% (v/v) destabilize the avidin tetramer toward dissociation and unfolding, via both its effects on charge state distribution (CSD) as well as at the level of individual charge states. In contrast, DMSO both protects against heme loss and increases the stability of CYP142A1 toward unfolding even up to 40% DMSO. Tandem MS/MS experiments showed that DMSO could modify the dissociation pathway of CYP142A1, while CIU revealed the protective effect of the heme group on the structure of CYP142A1.D.S.-H.C. acknowledges the Croucher Foundation and the Cambridge Commonwealth, European and International Trust for receipt of a Croucher Cambridge International Scholarship. M.E.K. was supported by a Commonwealth (University of Cambridge) Scholarship awarded in conjunc-tion with the Cambridge Commonwealth Trust and Cam-bridge Overseas Trust. K.J.M. and A.G.C. were supported by grants from the UK BBSRC (Biotechnology and Biological Sciences Research Council (BB/I019669/1 and BB/I019227/1)
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Insight into Protein Conformation and Subcharging by DMSO from Native Ion Mobility Mass Spectrometry
Electrospray ionization-mass spectrometry (ESI-MS) interfaced with ion-mobility (IM) spectrometry has enabled the study of protein structure and interactions under native-like conditions. In biological assays, dimethyl sulfoxide (DMSO) is often included as a co-solvent to dissolve organic molecules. While low levels of DMSO are known to reduce the charge of protein ions generated by ESI, the exact mechanism by which this occurs has been debated. In this study, we describe the first application of IMâMS to study the effect of DMSO subcharging on native protein conformation. We find that at low concentrations, DMSO induces modest (1-2â%), but repeatable, reductions in protein collision-cross sections (CCSs) of four different protein complexes, avidin, concanavalin A, alcohol dehydrogenase, and pyruvate kinase, as measured by traveling-wave (TW) IMâMS. Individual protein charge states also experienced compaction in size, suggesting that this effect could not be attributed to the shift of charge state distribution by DMSO alone.D.S.-H. Chan acknowledges the support of the Croucher Foundation and the Cambridge Commonwealth, European and International Trust for receipt of a Croucher Cambridge International Scholarship
Efecto del injerto en las propiedades antioxidantes del tomate (Solanum lycopersicum L.)
The use of grafted plants in vegetable crop production is now being expanded greatly. However, few data are available on the nutritional composition of grafted vegetables with emphasis on antioxidant properties. Therefore, the major objective of this study was to evaluate antioxidant components of tomatoes influenced by grafting technique. The tomato plants were grown in a greenhouse located at KrizËevci, Croatia. The cultivars âEfialtoâ, âHemanâ, and âMaxifortâ were used as rootstocks, while âTamarisâ was used as scion. Grafting resulted in increase of number of marketable fruits per plant by 30%. Content of total vitamin C and total phenolics significantly decreased after grafting. The concentration of total extractable phenolics in tomatoes ranged from 287.1 to 977.4 mg gallic acid equivalents (GAE) kgâ1 fresh weight, whereas lycopene content ranged from 11.44 to 60.99 mg kgâ1 fresh weight. Antioxidant activities determined by 1,1-diphenyl-2 picrylhydrazyl (DPPH) method of grafts were significantly different compared to their respective rootstocks. The overall results showed that tomato grafting on suitable rootstocks has positive effects on the cultivation performance, but decreases nutritional quality of tomatoes. En la producción de cultivos hortícolas se está expandiendo actualmente de forma considerable el uso de plantas injertadas. Sin embargo, hay pocos datos disponibles sobre la composición nutricional de las hortícolas injertadas, especialmente sobre sus propiedades antioxidantes. El principal objetivo de este estudio fue evaluar los componentes antioxidantes de tomates influenciados por la técnica de injerto. Se cultivaron plantas de tomate en un invernadero de KrizËevcii, Croacia. Se utilizaron como portainjertos los cultivares ‘Efialto’, ‘Heman’, y ‘Maxifort’, mientras que ‘Tamaris’ fue utilizado como injerto. El resultado del injerto fue un aumento del 30% en el número de frutos comerciales por planta, mientras que el contenido de vitamina C y de fenoles totales disminuyó significativamente. La concentración del total de fenoles extraíbles en los tomates varió entre 287,1 y 977,4 mg de equivalentes de ácido gálico (GAE) por kilo sobre la base de peso fresco, mientras que el contenido de licopeno varió desde 11,44 hasta 60,99 mg kg–1 de peso fresco. Las actividades antioxidantes determinadas por el método DPPH (2,2-difenil-1-picrilhidrazilo) de los injertos fueron significativamente diferentes respecto de sus respectivos patrones. Los resultados globales muestran que el injerto de tomate sobre patrones adecuados tiene efectos positivos sobre el rendimiento de cultivo, pero la calidad nutricional de los frutos disminuye
Solvent content of protein crystals from diffraction intensities by Independent Component Analysis
An analysis of the protein content of several crystal forms of proteins has
been performed. We apply a new numerical technique, the Independent Component
Analysis (ICA), to determine the volume fraction of the asymmetric unit
occupied by the protein. This technique requires only the crystallographic data
of structure factors as input.Comment: 9 pages, 2 figures, 1 tabl
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Mining 2:2 Complexes from 1:1 Stoichiometry: Formation of Cucurbit[8]urilâDiarylviologen Quaternary Complexes Favored by Electron-Donating Substituents
A 1:1 binding stoichiometry of a hostâguest complex need not consist of a single host and guest. Diarylviologens containing electron-donating substituents complexed with cucurbit[8]uril (CB[8]) in a 1:1 stoichiometry exhibit abnormally large binding enthalpies compared to typical enthalpy changes observed for 1:1 binary complexes. Here, several CB[8]-mediated hostâguest complexes, which were previously reported as 1:1 binary complexes, are verified to be 2:2 quaternary complexes by a combination of isothermal titration calorimetry, H, NOESY, and ROESY NMR, and ion mobility mass spectrometry, clearly indicating a binding motif of two partially overlapping diarylviologens held in place with two CB[8] molecules. Formation of 2:2 quaternary complexes is favored by electron-donating substituents, while electron-withdrawing substituents typically result in 1:1 binary complexes. The stacking of two highly conjugated diarylviologens in one quaternary motif affords the complexes enhanced conductance when considered as a single-molecular conductor. Moreover, an additional conducting signal previously observed for this âsupramolecularâ conductor can be readily understood with our 2:2 complexation model, corresponding to a parallel conductance pathway. Therefore, a 2:2 quaternary complex model grants a greater understanding of such supramolecular complexes, enabling the design of engineered, hierarchical structures and functional materials.The authors thank the Leverhulme Trust (project: âNatural material innovation for sustainable livingâ), the Marie Curie FP7 SASSYPOL ITN (607602) programme, and EPSRC (EP/ L504920/1) for funding
Revealing the sub-AU asymmetries of the inner dust rim in the disk around the Herbig Ae star R CrA
Models predict that in the innermost AU of the disk around Herbig Ae/Be star,
the dust disk forms a "puffed-up" inner rim, which should result in a strongly
asymmetric brightness distribution for disks seen under intermediate
inclination. Using the VLTI/AMBER long-baseline interferometer, we obtained 24
near-infrared (H- and K-band) spectro-interferometric observations on the
Herbig Ae star R CrA. In the derived visibility function, we detect the
signatures of an extended (25 mas) and a compact component (5.8 mas), with the
compact component contributing about 2/3 of the total flux. The brightness
distribution is highly asymmetric, as indicated by the strong closure phases
(up to 40 deg) and the detected position angle dependence of the visibilities
and closure phases. To interpret these asymmetries, we employ geometric as well
as physical models, including a binary model, a skewed ring model, and a
puffed-up inner rim model with a vertical or curved rim shape. Our curved
puffed-up rim model can reasonably well reproduce the interferometric
observables and the SED simultaneously and suggests a luminosity of 29 L_sun
and the presence of relatively large (> 1.2 micron) Silicate dust grains.
Perpendicular to the disk, two bow shock-like structures appear in the
associated reflection nebula NGC 6729, suggesting that the resolved sub-AU size
disk is the driving engine of a large-scale outflow. Detecting, for the first
time, strong non-localized asymmetries in the inner regions of a Herbig Ae
disk, our study supports the existence of a puffed-up inner rim in YSO disks.Comment: 17 pages; 15 figures; Accepted by A&
Strong Near-Infrared Emission Interior to the Dust-Sublimation Radius of Young Stellar Objects MWC275 and AB Aur
Using the longest optical-interferometeric baselines currently available, we
have detected strong near-infrared (NIR) emission from inside the
dust-destruction radius of Herbig Ae stars MWC275 and AB Aur. Our
sub-milli-arcsecond resolution observations unambiguously place the emission
between the dust-destruction radius and the magnetospheric co-rotation radius.
We argue that this new component corresponds to hot gas inside the
dust-sublimation radius, confirming recent claims based on spectrally-resolved
interferometry and dust evaporation front modeling.Comment: 12 pages, 4 figures, Accepted for publication in ApJ
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