On trifactorized soluble minimax groups

This research was done while the last two authors were visitors at the University of Mainz. They are grateful to the Department of Mathematics for its excellent hospitality.     

Über eine Modifikation der kolorimetrischen Bestimmung von Guanidingruppen mit dem Nitroprussiatreagens

Zusammenfassung Die Guanidingruppen in der Substanz P₇ und in Arginin lassen sich mit Nitroprussiat, Cyanoferrat(III) und Natronlauge bestimmen. Die Verwendung eines Lösungsmittelgemisches aus Isopropanol und Wasser verhindert die Bildung unlöslicher Niederschläge und erhöht in beträchtlichem Maß die Farbintensität und damit die Empfindlichkeit der Methode.

---

A modification of the colorimetric determination of guanidine groups with the nitroprusside reagent

Summary The guanidine groups in the substance P₇ (dichlorohydrate of 2,4-diguanidino-phenyl-lauryl ester monohydrate) and in arginine may be determined by means of nitroprussiate, cyanoferrate(III) and caustic soda solution. The employment of a solvent mixture consisting of isopropanol and water prevents the formation of insoluble precipitates and enhances to a high degree the color intensity and hence the sensitivity of the method.

     

Synthesis and Mesomorphic Properties of 2,6-Disubstituted Tetralins

Synthesis and mesomorphic behavior of nine members of each of the two classes of 6-phenyl- and 2-phenyltetralins and five members of the 2-trans-cyclohexyltetralins are reported. The synthesis of one member of each class is described in detail. Besides the target compounds, more than twenty intermediates showed liquid crystalline properties; their transition temperatures are recorded (see Tables 1-6).     

Sulle « catene » di numeri primi consecutivi a differenza limitata

Sunto Si considerano certi aggregati di numeri primi consecutivi, le cui differenze soddisfano a particolari disuguaglianze; aggregati a cui si attribuisce il nome di ? catene ?. Fra i vari tipi di catene (caratterizzate dalle disuguaglianze a cui soddisfano i numeri primi in esse contenuti) se ne studiano in particolare alcuni per i quali si giunge a fissare qualche limitazione relativa all'ampiezza massima della catena, oppure al numero delle catene presenti in un certo intervallo.     

Signs of heteronuclear spin–spin coupling constants in 15N-acetamide

By using digital deconvolution to improve spectral resolution, earlier NMR studies on ¹⁵N-enriched acetamide have been revised and extended to determine the signs of the heteronuclear spin-spin coupling constants. ¹J(¹³CO¹⁵N), ²J(¹³CH₃¹⁵N) and ³J(C¹H₃¹⁵N) are negative while ³J(¹H¹³CH₃)>0. The results, interpreted on the basis of the ‘selective decoupling’ formalism, were confirmed by computer simulation of the double resonance spectra. It is shown that ²J(¹H-α¹³CO) is significantly larger than ²J(¹H^{N 13}CO). Thus, jointly with {¹H-β}-¹³C′ double resonance experiments, {¹H-α}-¹³C′ experiments ought to be most helpful when assigning peptide group carbonyl resonances. The study provides valuable information for the interpretation of heteronuclear coupling constants in polypeptides.