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  • 1
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-0743
    Keywords: aortic aneurym ; transesophageal echocardiography ; thrombus ; prognosis ; preoperative examination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Transesophageal echocardiography (TEE) was performed in 17 cases of aortic aneurysms referred to our hospital for further examination and treatment. All 17 cases were treated surgically and TEE was performed as a preoperative examination. In nine of the 17 cases, there were already some signs of bleeding upon admission and in all of these nine cases, rupture of the aneurysm was confirmed during surgery. Measurement on cross-sectional TEE imaging disclosed large aneurysmal diameters in eight of these nine cases, suggesting a close relationship between diameter and rupture. Moreover, observation of the lesions by TEE suggested a relationship between the risk of rupture and morphological characteristics of the thrombus. In seven of the nine bleeding cases, TEE imaging revealed destructive features of the aneurysmal thrombus, such as exfoliation from the aortic wall and/or tearing-off, suggesting expansion of the aortic diameter. Detailed findings of the aneurysm and thrombus on TEE corresponded with surgical findings. Thus, we concluded that TEE is a useful method of obtaining information about aortic aneury sms not only as a preoperative examination but also as an independent examination to determine treatment options and prognosis.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-3904
    Keywords: Biological activity ; Isomer ratio ; RP-HPLC analysis ; Topological isomer ; Two-step disulfide bond formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In a two-step selective disulfide-bond-forming reaction of human uroguanylin, a 16-residue peptide with two intramolecular disulfide bonds, two compounds (I and II) were formed, which could be detected by RP-HPLC after the second disulfide-bond-forming reaction and were isolated as single entities. Their primary structures, molecular weights, and disulfide connectivities proved to be identical, but their optical rotation values were different, suggesting that they are topological isomers. Only compound I was found to increase the cGMP levels in cultured T84 cells significantly. The ratio of these compounds was affected by the order of the disulfide-bond-forming reactions, but not by the solvent used. The presence of a carboxyl-terminal leucine residue seems to be crucial for stabilizing the conformation of the two isomers.
    Type of Medium: Electronic Resource
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  • 4
    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
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  • 5
    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
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  • 6
    ISSN: 1075-2617
    Keywords: Solution synthesis ; human midkine ; powerful solvent system ; powerful solvent system ; active region ; Chemistry ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Human midkine (hMK), a novel heparin-binding neurotrophic factor consisting of 121 amino acid residues with five intramolecular disulphide bonds, was synthesized by solution procedure in order to demonstrate the usefulness of our newly developed solvent system, a mixture of dichloromethane or chloroform and trifluoroethanol. The final protected 121-residue peptide was assembled from two large fully protected intermediates, Boc-(1-5 9)-OH and H-(60-121)-OBzl, in CHL/TFE (3:1, v/v) using water-soluble carbodiimide in the presence of HOOBt as coupling reagents. After removal of the protecting groups by HF followed by treatment with Hg(OAc)2 in 50% acetic acid, the fully deprotected peptide was subjected to the oxidative folding reaction. The final product was confirmed to have the correct disulphide structure from its tryptic peptide mapping and to possess the same biological activities as those of the natural product. In order to clarify the active region of the hMK molecule, the N-terminal and C-terminal half domains [(1-59) and (60-121)] were also synthesized by the same procedure used for the hMK synthesis. The C-half domain was confirmed to show the full pattern of bioactivities except for the neuronal cell survival activity, while the N-half one showed much less activity in general.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 733-744 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidative folding of ο-conotoxin MVIIC, a highly basic 26-amino acid peptide with three disulfide bonds, predominantly gave two products with mismatched disulfide bonds in 0.1M NH4OAc buffer (pH 7.7) at 21°C both in the presence and absence of redox reagents such as reduced and oxidized glutathione. A low reaction temperature (5°C) and a high salt concentration in buffer such as 2M (NH4)2SO4 were necessary to obtain the correctly folded biologically active product. The folding reaction was found to proceed via a two-stage pathway of (I) the formation and (II) the rearrangement of the mismatched disulfide bonds. Both the reaction temperature and the salt strongly affected the equilibrium between mismatched and correctly formed disulfide bonds in the second stage. Such an effect of salts on the rearrangement reaction could be explained by anion binding at a low concentration and the salting out effect at a high concentration by analyzing the rank order of their effectiveness. The anion-binding effect was also confirmed by examining the folding of the tetra-acetylated peptide at the Lys side chains. CD study suggested that the yield of the biologically active product was correlated with its conformational change as functions of temperature and salt concentration. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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