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  • 1
    ISSN: 1432-1017
    Keywords: Key words Kinetic folding ; Minimun free energy structures ; RNA secondary structures ; Sequence structure relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Algorithms predicting RNA secondary structures based on different folding criteria – minimum free energies (mfe), kinetic folding (kin), maximum matching (mm) – and different parameter sets are studied systematically. Two base pairing alphabets were used: the binary GC and the natural four-letter AUGC alphabet. Computed structures and free energies depend strongly on both the algorithm and the parameter set. Statistical properties, such as mean number of base pairs, mean numbers of stacks, mean loop sizes, etc., are much less sensitive to the choice of parameter set and even of algorithm. Some features of RNA secondary structures, such as structure correlation functions, shape space covering and neutral networks, seem to depend only on the base pairing logic (GC or AUGC alphabet).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 101 (1979), S. 4708-4713 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of organic chemistry 44 (1979), S. 374-379 
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 82 (1978), S. 459-463 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The paper presents a qualitative analysis of the following systems ofn differential equations: $$\dot x_i = x_i x_j - x_i \sum\nolimits_r^n { = 1} x_r x_s {\mathbf{ }}(j = i - 1 + n\delta _{i1} {\mathbf{ }}and{\mathbf{ }}s = r - 1 + n\delta _{r1} )$$ , which show cyclic symmetry. These dynamical systems are of particular interest in the theory of selforganization and biological evolution as well as for application to other fields.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 99 (1968), S. 601-605 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Zusammenfassung 1,2-Dimethyl-3,5-dioxopyrazolidin wird durch direkte Umsetzung von Malonsäuredimethylester und sym-Dimethylhydrazin erhalten. Kondensation dieser Verbindung mit aliphatischen und aromatischen Aldehyden liefert elektrisch neutrale organische Lewissäuren, die in bezug auf die UV-Absorption weitestgehend den entsprechenden cyclischen Isopropylidenacylalen von Alkylund Aryl-methylenmalonsäuren gleichen. 1,2-Dimethyl-3,5-pyrazolidinedione obtained directly from dimethyl malonate and sym.-dimethylhydrazine. Condensation with aliphatic and aromatic aldehydes leads to electrically neutral organic Lewis acids. Their UV-spectra are similar to those of the corresponding cyclic isopropylidene acylals of substituted malonic acids.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract The reaction is described of the condensation products ofMeldrum's acid with aldehydes1–3 2 with diazomethane in methanol/ether, which leads to the cyclopropane compounds1 b-3 b. This is a known mode of reaction and is predicted by quantum chemical calculations ofP. Schuster. A reaction hitherto unobserved was found in the case of the compound4. The reaction with CH2N2 in methanol/ether at various temperatures yields the compound4 c as well as4 a and4 b. In CHCl3 the reactions yields only4 b in addition to many other high molecular weight products.
    Notes: Zusammenfassung Es wird die Reaktion der Kondensationsprodukte (1–3) vonMeldrumsäuren mit Diazomethan in Methanol/Äther beschrieben, die zu den Cyclopropanverbindungen1 b-3 b führt. Diese Reaktionsweise ist bekannt und auch nach quantenchemischen Berechnungen des einen von uns (P. Schuster) zu erwarten. Eine neue, bisher nicht beobachtete Reaktion wurde bei der Verbindung4 gefunden. Bei verschiedenen Temperaturen führt die Reaktion mit CH2N2 in Methanol/Äther (außer zu den Verbindungen4 a und4 b) zu4 c. In CHCl3 entsteht nur4 b neben viel allem Anschein nach hochmolekularen Produkten.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 96 (1965), S. 396-410 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract The π electron structures of diazo compounds are discussed and 19 examples calculated by means of the Hückel MO method (HMO) after selection of suitable parameters for the heteroatoms. The results obtained are presented as molecular diagrams (Figs. 3 to 21). The chemical behaviour of the compounds investigated can be understood to a great extent with the aid of these molecular diagrams.
    Notes: Zusammenfassung Es wird die π-Elektronenstruktur von Diazoverbindungen diskutiert und nach Wahl geeigneter Parameter für die Heteroatome mittels der Hückelmethode (HMO) für 19 Beispiele berechnet. Die dabei erhaltenen Resultate sind in den Moleküldiagrammen dieser Verbindungen (Abb. 3 bis Abb. 21) niedergelegt. Das chemische Verhalten der untersuchten Verbindungen läßt sich weitgehend an Hand der Moleküldiagramme verstehen.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 97 (1966), S. 1365-1383 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Using the experimental values for theK bands of nitro-, m-and p-dinitro- and sym-trinitrobenzene, the parameters of the resonance integrals of the nitro group were calculated to be ρCN=1,1 and ρNO=1,6, and the parameters of the Coulomb integrals estimated as ωO=1,5,ωN=1,8 and ωC=0,25 on the basis of plausibility considerations. The UV-spectra of the above compounds were measured in cyclohexane. The parameters obtained are used to calculate the molecular diagrams and energy levels. The calculated data are in good agreement with the experimental findings, above all when the more extensive inductive effects of the nitro group are suitably taken into account.
    Notes: Zusammenfassung Unter Benutzung der experimentellen Werte derK-Banden von Nitro-, m- und p-Dinitro- und sym-Trinitrobenzol wurden die Parameter der Resonanzintegrale der Nitrogruppe zu ρCN=1,1 und ρNO=1,6 bestimmt, die Parameter der Coulombintegrale auf Grund von Plausibilitätsbetrachtungen zu ωO=1,5, ωN=1,8 und ωC=0,25 abgeschätzt. Die UV-Spektren der vier genannten Verbindungen wurden in Cyclohexan vermessen. Die erhaltenen Parameter werden zur Berechnung der Moleküldiagramme und Energieniveaus der vier Strukturen benutzt. Die Rechendaten stehen in guter Übereinstimmung mit den experimentellen Befunden, vor allem dann, wenn den weiterreichenden induktiven Effekten der Nitrogruppe in geeigneter Weise Rechnung getragen wird.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 99 (1968), S. 832-837 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Zusammenfassung Erstmalig dargestellt und charakterisiert wurden 2-Chlor-4-amino-5-methylpyrimidin, 2-Trimethylammonium-4-dimethylamino-5-methylpyrimidin, 2-Cyan-4-dimethylamino-5-methylpyrimidin, 2-Amido-4-dimethylamino-5-methylpyrimidin und 2-Carboxy-4-dimethylamino-5-methylpyrimidin. Das 2-Cyan-4-dimethylamino-5-methylpyrimidin ist nicht zum Amin reduzierbar, wofür eine theoretische Erklärung gegeben wird.
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