TY  - JOUR
A1  - Seiler, Martin
A1  - Sremcevic, Miodrag
A1  - Seiss, Martin
A1  - Hoffmann, Holger
A1  - Spahn, Frank
T1  - A Librational Model for the Propeller Bleriot in the Saturnian Ring System
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
KW  - planets and satellites: individual (Saturn)
KW  - planets and satellites: rings
Y1  - 2017
U6  - https://doi.org/10.3847/2041-8213/aa6d73
SN  - 2041-8205
SN  - 2041-8213
VL  - 840
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Hoffmann, Holger
A1  - Ott, Christiane
A1  - Raupbach, Jana
A1  - Andernach, Lars
A1  - Renz, Matthias
A1  - Grune, Tilman
A1  - Hanschen, Franziska S.
T1  - Assessing bioavailability and bioactivity of 4-Hydroxythiazolidine-2-Thiones, newly discovered glucosinolate degradation products formed during domestic boiling of cabbage
JF  - Frontiers in nutrition
N2  - Glucosinolates are plant secondary metabolites found in cruciferous vegetables (Brassicaceae) that are valued for their potential health benefits. Frequently consumed representatives of these vegetables, for example, are white or red cabbage, which are typically boiled before consumption. Recently, 3-alk(en)yl-4-hydroxythiazolidine-2-thiones were identified as a class of thermal glucosinolate degradation products that are formed during the boiling of cabbage. Since these newly discovered compounds are frequently consumed, this raises questions about their potential uptake and their possible bioactive functions. Therefore, 3-allyl-4-hydroxythiazolidine-2-thione (allyl HTT) and 4-hydroxy-3-(4-(methylsulfinyl) butyl)thiazolidine-2-thione (4-MSOB HTT) as degradation products of the respective glucosinolates sinigrin and glucoraphanin were investigated. After consumption of boiled red cabbage broth, recoveries of consumed amounts of the degradation products in urine collected for 24 h were 18 +/- 5% for allyl HTT and 21 +/- 4% for 4-MSOB HTT (mean +/- SD, n = 3). To investigate the stability of the degradation products during uptake and to elucidate the uptake mechanism, both an in vitro stomach and an in vitro intestinal model were applied. The results indicate that the uptake of allyl HTT and 4-MSOB HTT occurs by passive diffusion. Both compounds show no acute cell toxicity, no antioxidant potential, and no change in NAD(P)H dehydrogenase quinone 1 (NQO1) activity up to 100 mu M. However, inhibition of glycogen synthase kinases-3 (GSK-3) in the range of 20% for allyl HTT for the isoform GSK-3 beta and 29% for 4-MSOB HTT for the isoform GSK-3 alpha at a concentration of 100 mu M was found. Neither health-promoting nor toxic effects of 3-alk(en)yl-4-hydroxythiazolidine-2-thiones were found in the four tested assays carried out in this study, which contrasts with the properties of other glucosinolate degradation products, such as isothiocyanates.
KW  - stomach model
KW  - glycogen synthase kinase-3
KW  - cytotoxicity
KW  - antioxidant potential
KW  - intestinal model
KW  - cellular uptake
KW  - isothiocyanate
Y1  - 2022
U6  - https://doi.org/10.3389/fnut.2022.941286
SN  - 2296-861X
VL  - 9
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Buratti, Bonnie J.
A1  - Thomas, P. C.
A1  - Roussos, E.
A1  - Howett, Carly
A1  - Seiss, Martin
A1  - Hendrix, A. R.
A1  - Helfenstein, Paul
A1  - Brown, R. H.
A1  - Clark, R. N.
A1  - Denk, Tilmann
A1  - Filacchione, Gianrico
A1  - Hoffmann, Holger
A1  - Jones, Geraint H.
A1  - Khawaja, N.
A1  - Kollmann, Peter
A1  - Krupp, Norbert
A1  - Lunine, Jonathan
A1  - Momary, T. W.
A1  - Paranicas, Christopher
A1  - Postberg, Frank
A1  - Sachse, Manuel
A1  - Spahn, Frank
A1  - Spencer, John
A1  - Srama, Ralf
A1  - Albin, T.
A1  - Baines, K. H.
A1  - Ciarniello, Mauro
A1  - Economou, Thanasis
A1  - Hsu, Hsiang-Wen
A1  - Kempf, Sascha
A1  - Krimigis, Stamatios M.
A1  - Mitchell, Donald
A1  - Moragas-Klostermeyer, Georg
A1  - Nicholson, Philip D.
A1  - Porco, C. C.
A1  - Rosenberg, Heike
A1  - Simolka, Jonas
A1  - Soderblom, Laurence A.
T1  - Close Cassini flybys of Saturn’s ring moons Pan, Daphnis, Atlas, Pandora, and Epimetheus
JF  - Science
N2  - Saturn’s main ring system is associated with a set of small moons that either are embedded within it or interact with the rings to alter their shape and composition. Five close flybys of the moons Pan, Daphnis, Atlas, Pandora, and Epimetheus were performed between December 2016 and April 2017 during the ring-grazing orbits of the Cassini mission. Data on the moons’ morphology, structure, particle environment, and composition were returned, along with images in the ultraviolet and thermal infrared. We find that the optical properties of the moons’ surfaces are determined by two competing processes: contamination by a red material formed in Saturn’s main ring system and accretion of bright icy particles or water vapor from volcanic plumes originating on the moon Enceladus.
Y1  - 2019
U6  - https://doi.org/10.1126/science.aat2349
SN  - 0036-8075
SN  - 1095-9203
VL  - 364
IS  - 6445
SP  - 1053
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Seiler, Michael
A1  - Seiß, Martin
A1  - Hoffmann, Holger
A1  - Spahn, Frank
T1  - Hydrodynamic Simulations of Asymmetric Propeller Structures in Saturn's Rings
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series
N2  - The observation of the non-Keplerian behavior of propeller structures in Saturn's outer A ring raises the question: how does the propeller respond to the wandering of the central embedded moonlet? Here, we study numerically how the structural imprint of the propeller changes for a libration of the moonlet. It turns out that the libration induces an asymmetry in the propeller, which depends on the libration period and amplitude of the moonlet. Further, we study the dependence of the asymmetry on the libration period and amplitude for a moonlet with a 400 m Hill radius, which is located in the outer A ring. This allows us to apply our findings to the largest known propeller Blériot, which is expected to be of a similar size. For Blériot, we can conclude that, supposing the moonlet is librating with the largest observed period of 11.1 yr and an azimuthal amplitude of about 1845 km, a small asymmetry should be measurable but depends on the moonlet's libration phase at the observation time. The longitude residuals of other trans-Encke propellers (e.g., Earhart) show amplitudes similar to Blériot, which might allow us to observe larger asymmetries due to their smaller azimuthal extent, allowing us to scan the whole gap structure for asymmetries in one observation. Although the librational model of the moonlet is a simplification, our results are a first step toward the development of a consistent model for the description of the formation of asymmetric propellers caused by a freely moving moonlet.
KW  - Hydrodynamics
KW  - methods: data analysis
KW  - methods: numerical
KW  - planets and satellites: dynamical evolution and stability
KW  - planets and satellites: individual (Saturn)
KW  - planets and satellites: rings
Y1  - 2019
U6  - https://doi.org/10.3847/1538-4365/ab26b0
SN  - 0067-0049
SN  - 1538-4365
VL  - 243
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Seiß, Martin
A1  - Albers, Nicole
A1  - Sremčević, Miodrag
A1  - Schmidt, Jürgen
A1  - Salo, Heikki
A1  - Seiler, Michael
A1  - Hoffmann, Holger
A1  - Spahn, Frank
T1  - Hydrodynamic Simulations of Moonlet-induced Propellers in Saturn's Rings
BT  - Application to Bleriot
JF  - The astronomical journal
N2  - One of the biggest successes of the Cassini mission is the detection of small moons (moonlets) embedded in Saturns rings that cause S-shaped density structures in their close vicinity, called propellers. Here, we present isothermal hydrodynamic simulations of moonlet-induced propellers in Saturn's A ring that denote a further development of the original model. We find excellent agreement between these new hydrodynamic and corresponding N-body simulations. Furthermore, the hydrodynamic simulations confirm the predicted scaling laws and the analytical solution for the density in the propeller gaps. Finally, this mean field approach allows us to simulate the pattern of the giant propeller Blériot, which is too large to be modeled by direct N-body simulations. Our results are compared to two stellar occultation observations by the Cassini Ultraviolet Imaging Spectrometer (UVIS), which intersect the propeller Blériot. Best fits to the UVIS optical depth profiles are achieved for a Hill radius of 590 m, which implies a moonlet diameter of about 860 m. Furthermore, the model favors a kinematic shear viscosity of the surrounding ring material of ν0 = 340 cm2 s−1, a dispersion velocity in the range of 0.3 cm s−1 < c0 < 1.5 cm s−1, and a fairly high bulk viscosity 7 < ξ0/ν0 < 17. These large transport values might be overestimated by our isothermal ring model and should be reviewed by an extended model including thermal fluctuations.
KW  - diffusion
KW  - hydrodynamics
KW  - planets and satellites: rings
Y1  - 2018
U6  - https://doi.org/10.3847/1538-3881/aaed44
SN  - 0004-6256
SN  - 1538-3881
VL  - 157
IS  - 1
PB  - IOP Publishing Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Hsu, Hsiang-Wen
A1  - Schmidt, Jürgen
A1  - Kempf, Sascha
A1  - Postberg, Frank
A1  - Moragas-Klostermeyer, Georg
A1  - Seiss, Martin
A1  - Hoffmann, Holger
A1  - Burton, Marcia
A1  - Ye, ShengYi
A1  - Kurth, William S.
A1  - Horanyi, Mihaly
A1  - Khawaja, Nozair
A1  - Spahn, Frank
A1  - Schirdewahn, Daniel
A1  - Moore, Luke
A1  - Cuzzi, Jeff
A1  - Jones, Geraint H.
A1  - Srama, Ralf
T1  - In situ collection of dust grains falling from Saturn’s rings into its atmosphere
JF  - Science
N2  - Saturn’s main rings are composed of >95% water ice, and the nature of the remaining few percent has remained unclear. The Cassini spacecraft’s traversals between Saturn and its innermost D ring allowed its cosmic dust analyzer (CDA) to collect material released from the main rings and to characterize the ring material infall into Saturn. We report the direct in situ detection of material from Saturn’s dense rings by the CDA impact mass spectrometer. Most detected grains are a few tens of nanometers in size and dynamically associated with the previously inferred “ring rain.” Silicate and water-ice grains were identified, in proportions that vary with latitude. Silicate grains constitute up to 30% of infalling grains, a higher percentage than the bulk silicate content of the rings.
Y1  - 2018
U6  - https://doi.org/10.1126/science.aat3185
SN  - 0036-8075
SN  - 1095-9203
VL  - 362
IS  - 6410
SP  - 49
EP  - +
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Abbas, Ioana M.
A1  - Vranic, Marija
A1  - Hoffmann, Holger
A1  - El-Khatib, Ahmed H.
A1  - Montes-Bayón, María
A1  - Möller, Heiko Michael
A1  - Weller, Michael G.
T1  - Investigations of the Copper Peptide Hepcidin-25 by
LC-MS/MS and NMR⁺
JF  - International Journal of Molecular Sciences
N2  - Hepcidin-25 was identified as themain iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II) binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandemmass spectrometry (MS/MS), high-resolutionmass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or referencematerial comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others.
KW  - hepcidin-25
KW  - copper
KW  - nickel
KW  - copper complex
KW  - ATCUN motif
KW  - metal complex
KW  - MS
KW  - NMR structure
KW  - metal peptide
KW  - metalloprotein
KW  - metallopeptide
KW  - isomerization
KW  - racemization
KW  - purity
KW  - reference material
Y1  - 2018
U6  - https://doi.org/10.3390/ijms19082271
SN  - 1422-0067
SN  - 1661-6596
VL  - 19
IS  - 8
PB  - Molecular Diversity Preservation International
CY  - Basel
ER  - 
TY  - GEN
A1  - Abbas, Ioana M.
A1  - Vranic, Marija
A1  - Hoffmann, Holger
A1  - El-Khatib, Ahmed H.
A1  - Montes-Bayón, María
A1  - Möller, Heiko Michael
A1  - Weller, Michael G.
T1  - Investigations of the Copper Peptide Hepcidin-25 by
LC-MS/MS and NMR⁺
T2  - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
N2  - Hepcidin-25 was identified as themain iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II) binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandemmass spectrometry (MS/MS), high-resolutionmass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or referencematerial comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 701 
KW  - hepcidin-25
KW  - copper
KW  - nickel
KW  - copper complex
KW  - ATCUN motif
KW  - metal complex
KW  - MS
KW  - NMR structure
KW  - metal peptide
KW  - metalloprotein
KW  - metallopeptide
KW  - isomerization
KW  - racemization
KW  - purity
KW  - reference material
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-427926
SN  - 1866-8372
IS  - 701
ER  - 
TY  - JOUR
A1  - Hoffmann, Holger
A1  - Seiss, Martin
A1  - Salo, Heikki
A1  - Spahn, Frank
T1  - Vertical structures induced by embedded moonlets in Saturn's rings
JF  - Icarus : international journal of solar system studies
N2  - We study the vertical extent of propeller structures in Saturn's rings (i) by extending the model of Spahn and Sremcevic (Spahn, F., Sremcevic, M. [2000]. Astron. Astrophys., 358, 368-372) to include the vertical direction and (ii) by performing N-body box simulations of a perturbing moonlet embedded into the rings. We find that the gravitational interaction of ring particles with a non-inclined moonlet does not induce considerable vertical excursions of ring particles, but causes a considerable thermal motion in the ring plane. We expect ring particle collisions to partly convert the lateral induced thermal motion into vertical excursions of ring particles in the course of a quasi-thermalization. The N-body box simulations lead to maximal propeller heights of about 0.6-0.8 Hill radii of the embedded perturbing moonlet. Moonlet sizes estimated by this relation are in good agreement with size estimates from radial propeller scalings for the propellers Bleriot and Earhart. For large propellers, the extended hydrodynamical propeller model predicts an exponential propeller height relaxation, confirmed by N-body box simulations of non-self gravitating ring particles. Exponential cooling constants, calculated from the hydrodynamical propeller model agree fairly well with values from fits to the tail of the azimuthal height decay of the N-body box simulations. From exponential cooling constants, determined from shadows cast by the propeller Earhart and imaged by the Cassini spacecraft, we estimate collision frequencies of about 6 collisions per particle per orbit in the propeller gap region and about 11 collisions per particle per orbit in the propeller wake region. (C) 2015 Elsevier Inc. All rights reserved.
KW  - Planetary rings
KW  - Saturn, rings
KW  - Saturn, satellites
KW  - Disks
Y1  - 2015
U6  - https://doi.org/10.1016/j.icarus.2015.02.003
SN  - 0019-1035
SN  - 1090-2643
VL  - 252
SP  - 400
EP  - 414
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - THES
A1  - Hoffmann, Holger
T1  - Vertical structures induced by embedded propeller moonlets in Saturn's rings
Y1  - 2013
CY  - Potsdam
ER  -