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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 355 (1992), S. 595-596 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] FRITZ ET AL. REPLY — By means of an argument based on our recent description of the vsr DNA mismatch endonuclease1 and a statistical analysis of available E. coli sequence data, McClelland and Bhagwat describe a plausible mechanism by which certain tetranucleotide sequences are ...
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 297 (1982), S. 159-162 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] IS5 was first identified among clear plaque mutants of bac-teriophage A (AKH100), and was accordingly localized to the C-terminus of the cl represser gene13'14. IS5 was estimated to be 1,200-1,250 bp long, and electron microscopy revealed short inverted sequence repetitions at its ends. The 185 ...
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 339 (1989), S. 330-330 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR-I read with interest Alun Anderson's report from Tokyo (Nature 338, 283; 1989) about the project to sequence in Japan the entire Escherichia coli genome. Unfortunately, this report contains a misleading number, namely that about 450 kilobase pairs have been sequenced by researchers around the ...
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 194 (1984), S. 65-72 
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The pri gene locus of the conjugative broad host range plasmid RP4 maps between coordinates 40.3 and 43.5 and encodes two antigenically related forms of a DNA primase with a molecular mass of 118 and 80 kDa (kilodalton). Genesis of these two products has been examined using Pri+-recombinant plasmids. As shown by deletion analysis, the primase polypeptides are two separate translation products which arise from an in-phase overlapping gene arrangement. It is suggested that transcription of a set of RP4 genes including the pri gene starts at a promoter site within the Tra1 region. In vivo, RP4 mutant primase can apparently substitute for Escherichia coli primase as demonstrated by measuring suppression of the dnaG3(ts) mutant.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 109 (1976), S. 3615-3625 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Intramolecular Catalysis of Hydrolysis of (Pyrimidinylthio)carboxamides by Pyrimidine Ring-SystemsOn treatment of 2-thiocytosine (3) with iodoacetamide, in water the formation of the carboxylic acid 5 and in alcoholic solution the formation of ester 6 or 7 respectively was observed. The amide 4 could only be prepared in alkaline medium. After alkylation of 3 with 3-iodopropionamide (12) instead of iodoacetamide a marked reduction in the rate of hydrolysis is observed. The amide hydrolysis is completely prevented, if the N-1-nitrogen of 3 is alkylated. Kinetic analysis of the pH-dependent amide hydrolysis suggests a mechanism for intramolecular catalysis by pyrimidine ring-systems.
    Notes: Bei der Umsetzung von 2-Thiocytosin (3) mit Jodacetamid in Wasser wird die Carbonsäure 5, in alkoholischer Lösung der Ester 6 bzw. 7 gebildet. Die Darstellung des Amids 4 gelingt nur in alkalischer Lösung. Nach Alkylierung von 3 mit 3-Jodpropionamid (12) anstelle von Jodacetamid verlangsamt sich die Hydrolyse deutlich. Die Amidhydrolyse wird vollständing unterdrückt, wenn 2-Thiocytosin an N-1 alkyliert ist. Die kinetische Analyse der pH-abhängigen Amidhydrolyse führt zu einem Mechanismus-Vorschlag für die intramolekulare Katalyse unter Beteiligung des Pyrimidinsystems.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 353-360 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Crystal and Molecular Structure of 4-Amino-1-methyl-2-(methylthio)pyrimidinium Chloride - A Model for S-Alkylated 2-ThiocytidineCrystals of 4-amino-1-methyl-2-(methylthio)pyrimidinium chloride (3) are triclinic, space group P1, with two molecules in the asymmetric unit. The structure was solved by direct methods and refined to R = 0.054. The molecules are planar with the S-methyl group in a cis-relationship with the C(2)-N(3)-bond. Bond lengths and angles for the two molecules are equal within standard error limits, and indicate largely aromatic structures. In the crystal matrix, one of the two chloride ions in the asymmetric unit forms three hydrogen-bonds, the other only one.
    Notes: 4-Amino-1-methyl-2-(methylthio)pyrimidinium-chlorid (3) kristallisiert in der triklinen Raumgruppe P1 mit zwei Molekülen in der asymmetrischen Einheit. Die Lösung der Struktur durch direkte Methoden führte nach Verfeinerung zu einem R-Faktor von 0.054. Die Moleküle sind planar mit den S-Methyl-Gruppen in cis-Stellung zur C(2)-N(3)-Bindung. Bindungsabstände und -winkel der beiden Moleküle sind innerhalb der Standardabweichungen gleich und deuten auf weitgehend aromatische Konstitutionen. Im Kristallgitter bildet eines der beiden Chlorid-Ionen in der asymmetrischen Einheit drei, das andere dagegen nur eine Wasserstoffbrücken-bindung aus.
    Additional Material: 4 Ill.
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  • 7
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Alkaline Hydrolysis of the N-Clycosidic Bond of the Product of Alkylation of 2-Thiocytidine by IodoacetamideTeil der Diplom- und Doktorarbeit von M. Kröger, Univ. Hamburg 1974, und Techn. Univ. Braunschweig, in Vorbereitung.The alkylation of the rare nucleoside 2-thiocytidine (1) by halogenoacetamide (2) leads to a product with the cationic structure 3. The optimal rate of the alkylation is at ∽ pH 6. The isolated 3 is not stable in water at any pH: Between pH 3 and 8 a hydrolysis of the glycosidic bond is observed the rate of which is almost directly proportional to the OH--concentration. Above pH 9 a change in the reaction mechanism is observed, and products with intact glycosidic bonds are formed. 4-Amino-2-carbamoylmethylthio-1-(β-D-ribofuranosyl)pyrimidinium chloride (3a) is the first example of a base catalyzed hydrolysis of the glycosidic bond in the pyrimidine nucleoside series.
    Notes: Die Alkylierung des seltenen Nucleosids 2-Thiocytidin (1) mit Halogenacetamid (2) führt zu einem Produkt der kationischen Struktur 3. Die optimale Alkylierungsgeschwindigkeit wird bei pH 6 erreicht. Isoliertes 3 zersetzt sich in Wasser unabhängig vom pH-Wert: Für den Bereich von pH 3 bis 8 wird eine Hydrolyse der glycosidischen Bindung beobachtet, deren Geschwindigkeit der Konzentration an OH--Ionen nahezu proportional ist. Bei pH 9 findet ein Wechsel im Zersetzungsmechanismus statt, so daß im pH-Bereich oberhalb von 9 Produkte unter Erhaltung der glycosidischen Bindung beobachtet werden. 4-Amino-2-carbamoylmethylthio-1-(β-D-ribofuranosyl)pyrimidinium-chlorid (3a) ist das erste Beispiel für einen basenkatalysierten Hydrolysemechanismus in der Pyrimidin-Nucleosid-Reihe.
    Additional Material: 5 Ill.
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  • 8
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Nucleophilic Substitution at S-Alkylated 1-Methyl-2-thiocytosineThe 2-alkylthio-4-amino-1-methylpyrimidinium iodide (5) - accessible by alkylation of1-methyl-2-thiocytosine (4) - can be substituted at C-2 by the nucleophilic reagents H2S and NH3 under mild conditions. While thiols and primary amines lead to products stable towards hydrolytic attack, hydroxylamines and hydrazines as well as azide and rhodanide ions give products which are easily hydrolysed to the cytosine derivative 10. Aniline and substituted hydrazines lead only to 10. The chemical and spectroscopic properties of the products are discussed.
    Notes: Das durch Alkylierung von 1-Methyl-2-thiocytosin (4) mit Alkylhalogeniden entstehende 2-Alkylthio-4-amino-1-methylpyrimidiniumiodid (5) ist an C-2 unter milden Bedingungen durch H2S und NH3 nucleophil substituierbar. Thioalkohole und primäre Amine geben hydrolysestabile Produkte, während Hydroxylamine und Hydrazine sowie Azid- und Rhodanidionen Produkte geben, die sich leicht zum Cytosin-Derivat 10 hydrolysieren lassen. Anilin und substituierte Hydrazine geben nur 10. Die chemischen und spektroskopischen Eigenschaften der Produkte werden diskutiert.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 14 (1984), S. 60-61 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 10
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of S-Alkyl-2-thiocytosine Derivatives with Bifunctional Nucleophiles and their Application to Chemical Modifications of Transfer Ribonucleic AcidsThe chemical properties of 4-amino-I -methyl-2-(methylthio)pyrimidinium iodide (4) which is an alkylated derivative of 2-thiocytosine (3), were investigated. This compound reacts easily with nucleophilic reagents leading to an exchange of the substituent at the C-2 of the pyrimidine ring. Using an appropriate bifunctional nucleophile, derived from ethylene an intramolecular reaction occurs. Thus treatment with 2-mercaptoethanol or 1,2-ethanedithiol leads to 1-methylcytosine (9) or I-methyl-2-thiocytosine (8), respectively. If primary alkyl- amines are used for this exchange reaction 2-alkylamino-4-amino-I-methylpyrimidinium halides are formed (4 → 5, 6,7). Experiments o n 3 containing transfer ribonucleic acid from baker's yeast show that these reactions can be used for chemical modification of ribonucleic acids under mild conditions.
    Notes: 4-Amino-l-methyl-2-(methylthio)pyrimidiniumjodid (4) - ein alkyliertes Derivat des 2-Thiocytosins (3) - reagiert sehr leicht mit Nucleophilen unter Austausch des Substituenten am C-2 des Pyrimidinringes. Wird diese Austauschreaktion mit bifunktionellen Äthylderivaten durchgeführt, so erhält man in der Folgereaktion intramolekular eine Substitution. Mit 2-Mercaptoathanol entsteht I-Methylcytosin (9), mit 1,2-Athandithiol I-Methyl-2-thiocytosin (8). Die Austauschreaktion mit primären Aminen führt zu 2-Alkylamino-4-amino-1 -methyl-pyrimidiniumhalogeniden (4 → 5, 6, 7). Wie durch geeignete Experimente mit 3 enthaltender transfer-Ribonucleinsäure aus Hefe gezeigt werden konnte, sind diese Reaktionen zur schonenden Modifizierung von Ribonucleinsäuren anwendbar.
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