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  • 1
    Electronic Resource
    Electronic Resource
    Mass fragmentation and structure of siphonaxanthin, siphonein and derivatives (1971)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 5 (1971), S. 565-572 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High resolution mass spectrometry has been employed to establish the structural formulae of the unique carotenoid pigment siphonaxanthin, its natural ester, siphonein and several derivatives. Siphonaxanthin exhibits a fragmentation reaction that is unusual among carotenoid pigments, namely, the elimination of carbon dioxide, observed as [M - CO2] and [M - (CO2 + H2O)]. This reaction involves the migration of an oxygen atom. Siphonaxanthol, a partially hydrogenated siphonaxanthin, exhibits a similar reaction involving the elimination of carbon monoxide and formaldehyde. From the fragmentation of derivatives of siphonaxanthin, such as the triacetate, the dimethyl ether and siphonaxanthol, and also from the fragmentation of related pigments, such as loroxanthin and fucoxanthin, the unique structural units responsible for the elimination of the carbon dioxide and carbon monoxide have been identified.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210050508
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Mass spectrometric comparison of ordinary and fully deuterated α- and β-carotene (1972)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 6 (1972), S. 843-851 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The individual, deuterated, isomeric α- and β-carotenes were isolated from the green alga, Scenedesmus obliquus, cultivated in D2O containing 99·7 to 99·8 atom percent deuterium. Mass spectroscopy showed that both the α- and β-deuterio-carotene preparations contained principally the fully deuterated pigment molecules (C40D56), small quantities of deuterated molecules with one proton (C40D55H) and yet smaller quantities of deuterated molecules with two protons (C40D54H2). From statistical calculations the deuterio-carotene preparations also contained one to several isotopically-substituted deuterio-carotenes of each mass in the mass range 585 to 599 because of variation of the number of 13C and H atoms per molecule. The mass fragmentation of the deuterated pigments was analogous to that of the respective ordinary α- and β-carotene. It indicated that the protons in the C40D55H and C40D54H2 molecules were distributed approximately randomly in various parts of the structure as in the terminal rings and in the ends and central portions of the polyene chain.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210060804
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    Paper (German National Licenses)
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  • 3
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    A Precessing Disk in OJ 287? (1997)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Sillanpaa et al. have demonstrated that the active galactic nucleus OJ 287 has intensity peaks that recur within a period of about 12 yr. I suggest that this is the result of the sweeping of a precessing relativistic beam across our line of sight. In analogy to Hercules X-1 and SS 433, precession is attributed to the torque exerted by a companion mass on an accretion disk. Secondary maxima observed 1.2 yr after two of these peaks may be evidence of nodding motion.
    Keywords: Astrophysics
    Type: Astrophysical Journal; 478; 2; 478-527
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Single Close Encounters do not make Eccentric Planetary Orbits (1997)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The recent discovery of a planet in an orbit with eccentricity e = 0.63 +/- 0.08 around the solar-type star 16 Cyg B, together with earlier discoveries of other planets in orbits of significant eccentricity, raises the question of the origin of these orbits, so unlike the nearly circular orbits of our solar system. In this paper I consider close encounters between two planets, each initially in a nearly circular orbit (but with sufficient eccentricity to permit the encounter). Such encounters are described by a two-body approximation, in which the effect of the attracting star is neglected, and by the approximation that their separation vector follows a nearly parabolic path. A single encounter cannot produce the present state of these systems, in which one planet is in an eccentric orbit and the other has apparently been lost. Even if the requirement that the second planet be lost is dropped, nearly circular orbits cannot scatter into eccentric ones.
    Keywords: Astrophysics
    Type: Astrophysical Journal; 484; 2; 862-865
    Format: text
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    NASA TECHNICAL REPORTS
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