Showing papers by "University of Basel published in 1969"
TL;DR: The chapter describes that a bacterial strain can protect its own DNA from cleavage by its restriction endonucleases, which is brought about by site-specific methylation of the DNA, for which another activity, the DNA modification methylase, is responsible.
Abstract: Publisher Summary This chapter discusses the interaction of restriction endonucleases with double-stranded DNA molecules at specific sites leading to cleavage of the DNA into a number of fragments. The specificity of this interaction is thought to depend on the recognition by the enzyme of a particular sequence of base-pairs on the substrate DNA. Restriction endonucleases are found in many bacterial strains as products of genes carried either on the bacterial chromosome or on plasmid DNA. Among enzymes obtained from independent sources, each usually shows its own specificity of interaction. The chapter describes that a bacterial strain can protect its own DNA from cleavage by its restriction endonucleases. This protection is brought about by site-specific methylation of the DNA, for which another activity, the DNA modification methylase, is responsible. Both endonuclease and methylase are thought to recognize the same base sequences on their substrate DNA. Each independent system of restriction and modification activities would then recognize its own particular target on the DNA. Therefore, the modification given by a particular methylase protects the DNA only against restriction by the correlated endonuclease. The chapter also discusses that mostly for reasons of a historical and practical nature, laboratory strains such as Escherichia coli K12 and B or Haemophilus influenzae are widely used in the experimental investigation of DNA restriction and modification, although many other bacteria are either known or are likely to have restriction and modification systems.
634 citations
TL;DR: In this paper, a study of the solvolysis of NCCCX derivatives, where X equals halogen or OSO2R, shows that fragmentation may occur by a one-step mechanism or by several multi-step mechanisms depending on structural, electronic and steric factors.
Abstract: Heterolytic fragmentation can proceed by several mechanisms. A study of the solvolysis of γ-aminoalcohol derivatives NCCCX, where X equals halogen or OSO2R, shows that fragmentation may occur by a one-step mechanism or by several multi-step mechanisms depending on structural, electronic, and steric factors. The one-step synchronous mechanism has rigorous stereoelectronic requirements. It is associated with an increased reaction rate as evidenced by the “frangomeric” effect. Ketoxime derivatives RR′CNX may undergo Beckmann fragmentation by the synchronous mechanism or by prior rearrangement depending on their α-substituents. Fragmentation is frequently accompanied by conventional substitution, elimination, and rearrangement reactions. Under such circumstances knowledge of all possible mechanisms of a given substrate is essential to bring about a desired transformation.
292 citations
TL;DR: The interaction between the two nonconjugated π-bonds in 1, 4-cyclohexadiene, norbornadiene and bicyclo[2.2]octadiene has been determined by photoelectron spectroscopy to be 1.0, 0.85 and 0.6 eV respectively as mentioned in this paper.
Abstract: The interaction between the two non-conjugated π-bonds in 1, 4-cyclohexadiene, norbornadiene and bicyclo[2.2.2]octadiene has been determined by photoelectron spectroscopy to be 1.0, 0.85 and 0.6 eV respectively.
206 citations
TL;DR: In this paper, a synchrone fragmentierung is proposed, which is an strenge stereoelektronische Bedingungen gebunden and hat eine erhohte Reaktionsgeschwindigkeit zur Folge, die sich im "frangomeren Effekt" ausert.
Abstract: Heterolytische Fragmentierungen konnen nach mehreren Reaktionsmechanismen ablaufen. Am Beispiel von γ-Halogenalkylaminen und γ-Aminosulfonaten (NCCCX) kann gezeigt werden, das infolge struktureller und sterischer Faktoren ein- oder mehrstufige Mechanismen in Erscheinung treten. Die einstufige, synchrone Fragmentierung ist an strenge stereoelektronische Bedingungen gebunden und hat eine erhohte Reaktionsgeschwindigkeit zur Folge, die sich im „frangomeren Effekt” ausert. Ketoxim-Derivate RR′CNX reagieren je nach der Natur der α-Substituenten entweder unter synchroner Beckmann-Fragmentierung oder unter Beckmann-Umlagerung zu Nitrilium-Salzen, welche ebenfalls zu Fragmentierungsprodukten fuhren konnen. Da Fragmentierungen haufig von konventionellen Substitutionen, Eliminationen und Umlagerungen begleitet werden, setzt eine erfolgreiche Reaktionslenkung die Kenntnis aller moglichen Mechanismen voraus.
171 citations
TL;DR: In this paper, a new formulae for the 7 Calotropis glycosides: calactin, calotropin, uscharidin (19), calotoxin (20), procerosid (21), uscharin, and voruscharin (32).
Abstract: Reduction of uscharidin (19) with NaBH4 gave a crystalline product C29H42O9 which we formulate as β-tetrahydro-uscharidin (12), it was characterised as a crystalline tri-O-acetyl-derivative 14. The same compound 12 was obtained from calactin (18) and calotropin (18A), thus confirming earlier results of HESSEet al. about the close interrelationship of the three compounds. New formulae are suggested for the 7 Calotropis glycosides: calactin (18), calotropin (18A), uscharidin (19), calotoxin (20), procerosid (21), uscharin (31), and voruscharin (32). These formulae are consistent with the chemical reactions and spectra of the mentioned compounds. They are constructed in analogy to the formula of gomphoside (11) advanced by WATSONet al. with only an additional oxo group at C-19.
62 citations
TL;DR: It is concluded that the π-system of the ligands is important for such a great increase in stability of the ternary Cu2+ complexes, since it is suggested for several enzymes that the imidazole group of histidine is involved with the binding of metal ions
Abstract: The stability constants of the ternary Cu2+ complexes, ethylenediamine-Cu2+-pyrocatechol and histamine-Cu2+-pyrocatechol dianion, were determined. Both complexes are more stable than one would expect on pure statistical reasons. The imidazole-containing ternary Cu2+ complex is, however, especially stable. For the equilibrium, Cu(histamine)2+ Cu(pyrocatechol)2⇋ 2[(histamine)Cu(pyrocatechnol)], the constant is log X= 4.86 (I= 0.1; T= 25°), while the statistical value is 0.6. These results were compared with those taken (or calculated) from the literature; it is concluded that the π-system of the ligands is important for such a great increase in stability. Furthermore, the Cu2+-histamine 1:1 complex selectively binds to O-ligands rather than to N-ligands. Thus, the first coordinated ligand has an influence on the kind of the second to be coordinated, i. e. the Cu2+-histamine 1:1 complex shows discriminating qualities. The significance of these results is discussed with regard to Cu-proteins, since it is suggested for several enzymes that the imidazole group of histidine is involved with the binding of metal ions.
61 citations
54 citations
TL;DR: A massive decrease of the neurosecretory granules already at a dehydration of 36 hours is found and at the same time a significant increase of fat vacuoles in the pituicytes.
Abstract: Der Hypophysenhinterlappen von Ratten, die einer Dehydratation unterworfen waren, wurde ultrastrukturell-morphometrisch untersucht. Als wichtigster Befund wurde bereits nach 36stundiger Dehydratation eine massive Abnahme der Neurosekretgranula festgestellt. Gleichzeitig ist ein signifikanter Anstieg der Fettkorper in den Pituicyten zu verzeichnen. Die Fettkorper konnen nach Ansicht der Autoren als Endprodukt der Membranreste oder der Tragersubstanz des Neurohormons interpretiert werden. Eine Mitbeteiligung der Lysosomen bei ihrer Verarbeitung wird diskutiert.
49 citations
TL;DR: In this paper, the δ bands (C 2 Π- X 2 2 − Π) of the NO molecule, emitted by the blue afterglow in a N 2 + O 2 mixture, are photographed with high resolution.
46 citations
TL;DR: Three additional compounds are obtained from the latex of Calotropis procera: uzarigenin, syriogenin and proceroside, which is a new glycoside containing a sugar moiety identical or stereoisomeric with those present in gomphosides, calactin and calotropin.
Abstract: From the latex of Calotropis procera, HESSEet al. [2] had isolated free calotropagenin (8) and six of its glycosides. We now obtained three additional compounds: uzarigenin (4), syriogenin [10] (a 3 β, 14α, x-trihydroxy-card-(20:22)-enolide) and proceroside. The latter is a new glycoside containing a sugar moiety identical or stereoisomeric with those present in gomphoside, calactin and calotropin. Its aglycone, not yet known in free form, contains one (probably secondary) hydroxyl group more than calotropagenin and is most probably a 2α, 3β, 14β, x-tetrahydroxy-card-(20:22)-enolide.
45 citations
TL;DR: The supraoptic nucleus of the dehydrated rat has been analysed and it appears, that the relative volumes of the different cell compartments are striking constant, and expression of an accelerated move of the neurosecretory material during increased synthesis is demonstrated.
Abstract: Der Nucleus supraopticus der Ratte, die einer Dehydratation ausgesetzt war, wurde ultrastrukturell-morphometrisch analysiert. Dabei zeigte sich, das die relativen Volumenanteile der einzelnen Zellkompartimente wahrend der funftagigen Durstperiode eine auffallende Konstanz aufweisen. Hingegen last sich eine absolute Zunahme der Einzelzellvolumina und somit auch der an der Synthese und Sekretion der Neurohormone beteiligten Zellkompartimente feststellen. Die vorliegenden Befunde sprechen fur einen beschleunigten Abtransport des neurosekretorischen Materials bei gesteigerter Synthese. Auf eine optimale Standardisierung der Perfusionsmethode bei Untersuchungen am neurosekretorischen Zwischenhirnsystem wird hingewiesen.
TL;DR: In this article, a method for determining the degree of order from the relative intensities of the parallel and perpendicular components of the hyperfine spectrum of vanadyl acetylacetonate was discussed.
Abstract: The E.S.R. spectrum of vanadyl acetylacetonate dissolved in a liquid crystal which is nematic at room temperature has been investigated. The spectrum differs from other E.S.R. studies in liquid crystals with nematic ranges at elevated temperatures in that the molecular tumbling time has slowed enough to produce a ‘glassy’ type spectrum. Previous theories are no longer applicable and a method is discussed for determining the degree of order from the relative intensities of the parallel and perpendicular components of the hyperfine spectrum. The method is supported by the drastic change in intensities upon application of a transverse electric field.
TL;DR: It is assumed, that phenetidine is the main toxic agent in nephropathy due to phenacetin abusus, and an unusual dose-dependence of the metabolic pattern is revealed.
Abstract: Experiments on the metabolism of phenacetin in the rat are reported. Estimations of phenacetin, total acetyl-p-aminophenol,p-phenetidine and 2-hydroxyphenetidine-sulfate in the urine excreted after ingestion of phenacetin reveal an unusual dose-dependence of the metabolic pattern. The degradation of phenacetin through deacetylation to phenetidine is greatly enhanced by raising the dose. The results are briefly discussed in view of their possible significance in the development of analgesic nephropathy in man. As a working hypothesis for further experiments it is assumed, that phenetidine is the main toxic agent in nephropathy due to phenacetin abusus.
TL;DR: In this paper, an enantiomeric (+)-Camphorquinone (1) was transformed to a mixture of 3-exo-hydroxy-Camphor (3a) (30%) by an aqueous suspension of Absidia orchidis (Vuill.) Hagem.
Abstract: (—)-Camphorquinone (1a) was transformed to a mixture consisting of 3-endo-hydroxy-camphor (2a) (40%), 3-exo-hydroxy-camphor (3a) (30%) and 2-endo-hydroxy-epicamphor (4a) (30%) by an aqueous suspension of the mycelium of Absidia orchidis (Vuill.) Hagem. The composition of the reduction products was determined by the NMR. spectra. Incubation of the enantiomeric (+)-camphorquinone (1b) under the same condition yielded 3-exohydroxy-camphor (3b) as single product. Since both substrates form their products immediately and in the same ratio the possibility of a posterior isomerization of 3a yielding the ketols 2a and 4a can be ruled out. For comparison the course of the chemical reduction of camphorquinone (1) to the ketols (Zn in acetic acid, hydrogenation with Raney-Ni as catalyst, NaBH4) was investigated. Camphor was not transformed by Absidia orchidis. (—)-Isofenchonequinone (6a) yielded upon incubation with an aqueous suspension of the mycelium of Absidia orchidis exclusively 2-endo-hydroxy-epi-isofenchone (7a). The enantiomer diketone 6b gave the same result, i. e. the ketol 7b as the only transformation product. Also with isofenchonequinone the chemical reduction to the ketols by Zn in acetic acid, hydrogenation with Raney-Ni as catalyst and NaBH4 was studied.
TL;DR: Antilymphocytic serum protected mice with allogeneic bone-marrow grafts against lethal doses of a cytotoxic drug and donor-type haemopoiesis was shown by erythrocyte chimaerism.
Abstract: Antilymphocytic serum protected mice with allogeneic bone-marrow grafts against lethal doses of a cytotoxic drug. Donor-type haemopoiesis was shown by erythrocyte chimaerism.
TL;DR: In this paper, the NMR spectra of nearly all bufadienolides (steroidal toad poisons) of known structure (aglycones and acetyl derivatives) were measured (some in various solvents) and evaluated.
Abstract: The NMR. spectra of nearly all bufadienolides (steroidal toad poisons) of known structure (aglycones and acetyl derivatives) were measured (some in various solvents) and evaluated. The results obtained allow the application of the principle of the self-consistent chemical shift values (‘rule of additivity’) for the calculation of the chemical shifts of the 18- and 19- methyl groups. The frequencies of resonance and the coupling of the protons of the 17β-pentadienolide ring and of the α-protons of the functional groups were analysed. For the determination of the NMR. spectra of polyhydroxylated bufadienolides and cardenolides d6-dimethylsulfoxide proved to be the most suitable solvent. In this solvent not only the nature but also the relative positions of several hydroxyl groups can be recognized, the rule of additivity being also applicable.
On the basis of the data recorded the position and stereochemistry of functional groups in steroidal toad poisons of unknown structure can be determined with a high degree of probability.
TL;DR: The results suggest that dimethylsufoxid enhances the biological permeability of lysosomal membranes.
Abstract: Der Einflus von Dimethylsulfoxid auf die quantitative biochemische und histochemische Darstellung der sauren Phosphatase der Rattenleber wurde untersucht. Sowohl histochemisch an Schnittpraparaten als auch quantitativ in Gewebshomogenaten konnen intensivere bzw. hohere Enzymaktivitaten beobachtet werden. Dies last darauf schliesen, das Dimethylsulfoxid die Permeabilitat der Lysosomenmembranen erhoht.
TL;DR: In this paper, a set of phase shifts for 6Li(p, p)6Li tensor polarization has been measured to an accuracy of 0.01 at 11 energies from 1.2 to 3.2 MeV with a target of 20 keV thickness at 2 MeV.
TL;DR: Since evidence has been given that only those groups are oxidized by H 2 O 2 which are in the coordination sphere of Cu(II), this peroxidase-like “probe” was used to investigate 1:1 molar mixtures ofCu(II) and l -histidine or histamine, and the results suggested that l-histidine forms a histamine-like complex with Cu( II).
TL;DR: In this article, the influence of an electric field, applied in a direction perpendicular to the magnetic field, on the NMR spectra of ( cis ) 1,2-dichloroethylene, furan, thiophene and benzene, oriented in the nematic phase of a liquid crystal, is studied.
TL;DR: In this article, an investigation has been made on the coordination of Mn2+, Cu2+, and Zn2+, by several simple carboxylic acids and certain of α-oxy-and α-thiocarboxyly acids which have biochemical significance.
TL;DR: In this paper, a model for the dispersive interaction of a nonpolar solute with a non-polar solvent was derived for the behavior of the electronic spectrum of a polyene dissolved in binary mixed solvents.
TL;DR: In this paper, the synthesis of the hitherto unknown 14-epi-digitoxigenin (8) and 3-deoxy-digioxigenin(16) was described.
Abstract: The synthesis of the hitherto unknown 14-epi-digitoxigenin (8) and of 3-deoxy-digitoxigenin (16) is described. The 15,15-propylene-thio-sulfoxides 6 and 7 proved to be valuable intermediates. The results of the cardiotonic activity (ATPase test) of the cardenolides 8 and 16 are reported.
TL;DR: The theory for deceptive simplicity in the NMR spectra of oriented molecules is discussed in terms of degeneracy of subspectra as discussed by the authors, and conditions for the degeneracy leading to deceptive simplicity are discussed.
Abstract: The theory for deceptive simplicity in the NMR spectra of oriented molecules is discussed in terms of degeneracy of subspectra. The conditions for the degeneracy of AB, AB2 and AA′BB′ spectra leading to deceptive simplicity in the spectra of the type ABX, AB2X, AA′BB′X and AA′XX′ are reported.
It is shown that the conditions for deceptive simplicity are easily fulfilled for ABX, AA′BB′X and AA′XX′ cases. It is further demonstrated that deceptive simplicity is not so common in AB2X spectra.
The proton spectra of partially oriented 2,4,5-trichloronitrobenzene (AB) and 2,6-dibromo-pyridine (AB2) are use to illustrate degeneracy and those of p-chloro- and p-bromo-fluorobenzenes are reported to demonstrate deceptive simplicity.
TL;DR: These studies demonstrate the presence of a 17α-hydroxyprogesterone C17C20 lyase and indicate a pathway for the formation of androst-4-ene-3,17-dione from 17 α-hydroxylprogestersterone similar to that in mammalian testes and ovaries.