24 research outputs found
Characterization of O-glycosylated precursors of insulin-like growth factor II by matrix-assisted laser desorption/ionization mass spectrometry
High molecular weight precursors of insulin-like growth factor II (IGF-II) were isolated from Cohn fraction IV of human plasma by ultrafiltration, affinity chromatography and reversed-phase high-performance liquid chromatography. Molecular weight determination by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) of two high molecular weight IGF-II preparations revealed heterogeneous glycosylation. A combination of enzymatic degradation and MALDI-MS were applied for further structural characterization of the glycosylated precursors of IGF-II. The first step was molecular weight determination of intact high molecular weight IGF-IIs prior to and after treatment with neuraminidase and O-glycosidase. This, together with a comparison of molecular weight information available from the cDNA, revealed that both high molecular weight IGF-II species contain an identical C-terminal extension of 20 residues but different degrees of glycosylation. Second, comparative Endo Glu-C digestion of the preparations prior to and after enzymatic release of carbohydrates and subsequent remeasurement of the molecular weight by MALDI-MS confirmed the primary structure of precursor IGF-II1-87. The O-linked carbohydrates were found to be associated with the C-terminal extension and the heterogeneity was identified as varied sialylated forms of one and two HexNAc-Hex groups
The human insulin-like growth factor II gene contains two development-specific promoters
The insulin-like growth factors (IGF) play an important role in fetal and postnatal development. Recently, the nucleotide sequences of the cDNAs encoding IGF-I and IGF-II and part of the human IGF genes were reported. In this communication we describe two distinct IGF-II cDNAs isolated from a human adult liver and a human hepatoma cDNA library, respectively. Using these two cDNAs, we have established that the human IGF-II gene contains at least 7 exons. Two different IGF-II promoters have been identified, 19 kilobases (kb) apart, which are active in a development-specific manner. The promoter, active in the adult stage, is located only 1.4 kb downstream from the insulin gene
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Clouds and Clarity: Revisiting Atmospheric Feature Trends in Neptune-size Exoplanets
Over the last decade, precise exoplanet transmission spectroscopy has revealed the atmospheres of dozens of exoplanets, driven largely by observatories like the Hubble Space Telescope. One major discovery has been the ubiquity of atmospheric aerosols, often blocking access to exoplanet chemical inventories. Tentative trends have been identified, showing that the clarity of planetary atmospheres may depend on equilibrium temperature. Previous work has often grouped dissimilar planets together in order to increase the statistical power of any trends, but it remains unclear from observed transmission spectra whether these planets exhibit the same atmospheric physics and chemistry. We present a reanalysis of a smaller, more physically similar sample of 15 exo-Neptune transmission spectra across a wide range of temperatures (200-1000 K). Using condensation cloud and hydrocarbon haze models, we find that the exo-Neptune population is best described by low cloud sedimentation efficiency (f sed ∼ 0.1) and high metallicity (100 × solar). There is an intrinsic scatter of ∼0.5 scale height, perhaps evidence of stochasticity in these planets’ formation processes. Observers should expect significant attenuation in transmission spectra of Neptune-size exoplanets, up to 6 scale heights for equilibrium temperatures between 500 and 800 K. With JWST's greater wavelength sensitivity, colder (<500 K) planets should be high-priority targets given their clearer atmospheres, and the need to distinguish between the “super-puffs” and more typical gas-dominated planets. © 2024. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]