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  • Ascidian  (2)
  • KR-ET-1  (2)
  • Springer  (4)
  • 1995-1999  (4)
  • 1960-1964
  • 1935-1939
  • 1930-1934
  • 1920-1924
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  • Springer  (4)
Years
  • 1995-1999  (4)
  • 1960-1964
  • 1935-1939
  • 1930-1934
  • 1920-1924
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  • 1
    Electronic Resource
    Electronic Resource
    New cellulose synthesizing complexes (terminal complexes) involved in animal cellulose biosynthesis in the tunicateMetandrocarpa uedai (1996)
    Springer
    Protoplasma 194 (1996), S. 151-163 
    Details
    ISSN: 1615-6102
    Keywords: Cellulose microfibril ; Freeze-fracture ; Terminal complex ; Tunic ; Tunicate ; Ascidian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cellulose synthesizing enzyme complexes (terminal complexes, TCs) have been found in the plasma membrane of epidermal cells in the tunicateMetandrocarpa uedai by using freeze-fracture replication techniques for electron microscopy. Assembly of cellulose microfibrils by TCs is a universal phenomenon in the biological kingdoms. The TCs are locally distributed in the plasma membrane of the epidermal cells facing the tunic, and no TCs are observed on the lateral membranes bordered by tight junctions. The TCs consist of two types of membrane subunits: large particles (14.5 nm in diameter) on the periphery and small subunit particles (7.2 nm) filling the center; the latter are hypothesized to be involved in cellulose synthesis. The TCs are the linear type (ca. 195 nm in length and 78 nm in width). Direct connections of TCs with the termini of microfibrils were observed. Amorphous regions, which were hypothesized the nascent microfibrils, were associated with the depressions of the TCs. The distortion of microfibrils on their terminus indicates that the crystallization may occur at the margin of TCs from which the microfibrils are discharged. This report provides evidence that: (1) The outer cell membrane of epidermis is the site for the assembly of cellulose microfibrils in the tunic; (2) a new type of TC is involved in the biosynthesis of cellulose microfibrils in the tunicates; (3) disorganized glucan chains may be synthesized in the depression of TCs and crystallized outside the E-surface of the epidermal cell membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01882023
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  • 2
    Electronic Resource
    Electronic Resource
    A new cellulosic structure, the tunic cord in the ascidianPolyandrocarpa misakiensis (1998)
    Springer
    Protoplasma 204 (1998), S. 94-102 
    Details
    ISSN: 1615-6102
    Keywords: Ascidian ; Cellulose microfibril ; Hemocoel ; Polyandrocarpa misakiensis ; Tunic cord
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A specialized structure of tunic cord inPolyandrocarpa misakiensis is investigated by electron microscopy. The tunic cord is a cord-like coiled structure of 5–30 μm in diameter and 0.1–9.0 mm in length. The tunic cords originate and elongate from the dorsal tunic, and their termini have a swollen and ornamented structure. Scanning and transmission electron micrographs and the electron diffractogram show that the tunic cords are composed of bundled microfibrils of cellulose I with high crystallinity. The tunic cord is completely surrounded by single-layered epidermal cells, which have been found as the site of cellulose biosynthesis. A number of tunic cords are connected to the internal tunic of the siphon by forming “eyelet” structures at their termini. These observations suggest that the tunic cords act as a connector between dorsal and internal tunic of the siphon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01282297
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  • 3
    Electronic Resource
    Electronic Resource
    Improvement in the oxidative folding of endothelin-1 by a Lys-Arg extension at the amino terminus: Implication of a salt bridge between Arg-1 and Asp8 (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 185-192 
    Details
    ISSN: 1573-3904
    Keywords: α-Helix ; Carboxamide substitution ; Circular dichroism ; Disulfide isomer ; KR-ET-1 ; Prosequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An amino-terminal extension of endothelin-1 by the Lys-Arg dipeptide in the prosequence (KR-ET-1) greatly increased the ratio of native-type to non-native-type disulfide isomer (96/4 versus 71/29) during the oxidative folding reaction. This improvement was completely abolished by substituting Asn for Asp at position 8 (D8N-KR-ET-1), whereas most of it was maintained with similar carboxamide analogues replaced at Glu10 or Asp18. Structure analyses by circular dichroism spectroscopy revealed that (i) in the carboxylate state, the α-helical content of the native-type isomer of KR-ET-1 is higher than that of the native-type isomer of ET-1, while such a variation is not observed in the corresponding non-native-type isomer of KR-ET-1; and (ii) the enhanced α-helicity resulting from the Lys-Arg extension is largely diminished in D8N-KR-ET-1. From these results and our previous findings that the helical structure in KR-ET-1 is stabilized by a particular salt bridge between the extended Arg-1 basic moiety and either the Asp8 or Glu10 acidic side chain in ET-1 [Aumelas, A. et al., Biochemistry, 34 (1995) 4546], we conclude that the formation of a specific salt bridge between the side chains of Arg-1 and Asp8 in KR-ET-1 is critical for the predominant generation of the native-type disulfide isomer, probably because it stabilizes the helical structure of parental ET-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008835323518
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  • 4
    Electronic Resource
    Electronic Resource
    Improvement in the oxidative folding of endothelin-1 by a lys-Arg extension at the amino terminus: Implication of a salt bridge between Arg−1 and Asp8 (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 185-192 
    Details
    ISSN: 1573-3904
    Keywords: α-Helix ; Carboxamide substitution ; Circular dichroism ; Disulfide isomer ; KR-ET-1 ; Prosequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An amino-terminal extension of endothelin-l by the lys-Arg dipeptide in the prosequence (KR-ET-1) greatly increased the ratio of native-type to non-native-type disulfide isomer (96/4 versus 71/29) during the oxidative folding reaction. This improvement was completely abolished by substituting Asn for Asp at position 8 (D8N-KR-ET-1), whereas most of it was maintained with similar carboxamide analogues replaced at Glu10 or Asp18. Structure analyses by circular dichroism spectroscopy revealed that (i) in the carboxylate state, the α-helical content of the native-type isomer of KR-ET-l is higher than that of the native-type isomer of ET-1, while such a variation is not observed in the corresponding non-native-type isomer of KR-ET-l; and (ii) the enhanced α-helicity resulting from the Lys-Arg extension is largely diminished in D8N-KR-ET-l. From these results and our previous findings that the helical structure in KR-ET-l is stabilized by a particular salt bridge between the extended Arg−1 basic moiety and either the Asp8 or Glu10 acidic side chain in Et-1 [Aumelas, A. et al., Biochemistry, 34 (1995) 4546], we conclude that the formation of a specific salt bridge between the side chains of Arg−1 and Asp8 in KR-ET-1 is critical for the predominant generation of the native-type disulfide isomer, probably because it stabilizes the helical structure of parental ET-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02443532
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