Gibberellin metabolites from ent-kaura-2,16-dien-19-ol and its succinate in Gibberella fujikuroi

Exposure of ent-kaura-2,16-dien-19-ol (1) or its succinate (2) to resuspended mycelia of G. fujikuroi has produced a complex mixture of acids which after methylation gave the esters of two C₁₉ (24) and (30) and five C₂₀ gibberellins (4, 11, 20, 32 and 33). The triester (32) and the lactone ester (24) have been prepared before from the esters of gibberellin A₁₃ (8) and gibberellin A₄ (26) respectively. The structures of the other metabolites were assigned on spectroscopic data and by chemical transformations. Thus the lactone diester (4) has been converted to the known keto triester (6). The epoxide (11) has been related to gibberellin A₁₄ (14) and the aldehyde (33) has been related to gibberellin A₁₃ trimethyl ester (8) by way of the triol (34). Selective de-epoxidation of the 16,17-epoxy function in diepoxides has provided a route from the dienes (20 and 24) to the epoxides (11 and 30) respectively, but not from the ester of gibberellin A₅ (23) to that of gibberellin A₆ (29). On the other hand the latter can be obtained by epoxidation of gibberellin A₅ methyl ester trifluoroacetate. Backfeeding experiments carried out with the epoxy diacid (12), the diene diacid (21) and the derived diol (39) indicate pathways connecting the various metabolites. The natural gibberellins A₅ and A₆ were shown to be formed in some of the backfeeding experiments.     

The Spectrophotometric Determination of Gallium (III) with Glycine Thymol Blue

The reaction between gallium (III) and glycine thymol blue has been studied spectrophoptometrically in order to establish the optimum conditions for determining traces of gallium. The gallium (III) glycine thymol blue complex has an absorption maximum at 560 nm against a reagent blank and is stable between pH 4.0 and 5.5. The complex has a composition 1 : 2 and a formation constant of 6.4×10⁷ under the conditions studied. Beer's law is obeyed upto 126 μg of gallium. The net molar absorptivity has been found to be 11,000. The present method is very sensitive and rapid. Anions such as citrate and tartrate inhibit the colour development of the complex.     

Étude du dihydrate de l'acide chlorhydrique par spectroscopie infrarouge et raman: Spectres de vibration de l'ion H5O

An infrared and Raman study of crystalline hydrochloric acid dihydrate is made between 50 and 4000 cm⁻¹. This confirms the occurrence of the diaquohydrogen ion and allows the assignment of its fundamental vibrations. A comparison with the known spectra of H₅O₂⁺ salts with different anions shows that the formation of “external” hydrogen bonds perturbs the central short hydrogen bond vibrations.     

Polymerization of pyromellitic dianhydride with 3,3′-diaminobenzidine in aprotic solvents I. Reaction variables

The solution polymerization of pyromellitic dianhydride with 3,3′-diaminobenzidine to form poly(amide acid amine) was investigated under a variety of reaction conditions. Polymer viscosity and gel formation were highly affected by changes in the order of monomer addition, the type of process (powder or solution), monomer concentration, monomer stoichiometry, and type of solvent. Minor effects were noted with changes in polymerization temperature and the presence of small amounts of water. A limiting intrinsic viscosity of 1.2–1.5 dl/g was observed, regardless of polymerization conditions. The polymerization had a strong tendency to gel at high concentrations and when monomer molar ratios approached 1:1. The conditions which retarded or promoted the formation of macrogel were well-defined, and macrogel but not microgel could be prevented. The polymerization was conducted successfully only in aprotic solvents. No imidazopyrrol-one units were detected in polymer made in polyphosphoric acid at elevated temperatures.     

RECOVERY OF HAEMOPHILUS INFLUENZAE FROM ULTRAVIOLET AND X-RAY DAMAGE

Abstract— Results of experiments on reactivation of ultraviolet (u.v.)-irradiated Haemophilus influenzae and cellular reactivation of u.v.-damaged transforming deoxyribonucleic acid (DNA) and bacteriophage are reported. Liquid-holding recovery (LHR) is small for the u.v.-sensitive mutant BC100 which, relative to the wild type, also has greatly reduced host-cell reactivation (HCR) of u.v.-inactivated phage, and competent cultures show reduced competent cell reactivation (CCR) of u.v.-inactivated transforming DNA. BC100 cells can be transformed with DNA isolated from the wild type strain Rd to a u.v. resistance similar to that of Rd, and irradiation of the DNA reduces the transformation frequency for this marker (uvr). The u.v.-resistant mutant BC200 displays very little LHR under the usual conditions where reactivation occurs after plating. The colony-forming ability (cfa) of irradiated BC200 is greater than that of Rd, but HCR and CCR are the same on this mutant as on the wild type. The major difference between Rd and BC200 is the enhanced u.v. survival of cfa of the latter. It was determined that this difference reflects cell lysis of irradiated Rd and lack of lysis in BC200 cultures. That lysis is closely correlated with damage to the bacterial chromosome is suggested by the finding that the lytic response of Rd (as determined turbidimetrically) can be negated by the liquid-holding procedure, but lysis of BC100 (which lacks comparable DNA-repair ability) can be only partially inhibited by this procedure. LHR occurs when post-plating dark recovery is incomplete, is temperature-sensitive, and occurs unimpeded when post-u.v. protein synthesis is inhibited by chloramphenicol. It is suggested that enzymatically catalyzed reactivation of DNA occurs or is initiated during liquid-holding of u.v.-irradiated H. influenzae Rd and that the necessary enzyme(s) exists prior to appearance of u.v. lesions in the DNA. Results are reported for X-ray inactivation of transforming DNA as assayed on BC100, Rd and BC200 and of the cfa of the three strains.     

Metal derivatives of azoles,part VII. Pyrazolato-bridged dinuclear complexes containing either cyclopalladated or -platinated trimesitylphosphine or -arsine

Summary The halogen bridges of the dimeric, cyclometallated trimesityl-arsine and -phosphine complexes of palladium(II) and platinum(II), where M=Pd or Pt and E=P or As have been replaced with pyrazolate groups to give the corresponding and less symmetric pyrazolato-bridged complexes, where M=Pd or Pt, E=P or As, Pz=pyrazolato anion, and M=Pd, E=As, Pz=3,5-dimethylpyrazolato anion. In the case of the palladium complexes,¹H. n.m.r. clearly indicates the presence of only one isomer which is most likely to have thetrans configuration while the platinum complexes are mixtures of bothcis andtrans forms.Part VI, ref. 3c     

Angular momentum decoupling approximations in the quantum dynamics of reactive systems

Two methods for implementing angular momentum decoupling approximations in quantum mechanical reactive scattering examined. Applications of both reactive and nonreactive H + H₂ collisions indicate that for the most intense individual reactive transitions and for all degeneracy-averaged ones, these decoupling methods (especially the “proper” decoupling method) yield results in good agreement with those of fully-coupled calculations. However, for the less intense reactive transitions and all individual nonreactive transitions, very large errors can result from use of these approximate methods.     

A hydrodynamic voltammetric study of the ferricyanide/ferrocyanide system with convective electrodes of platinum,gold, glassy carbon,carbon film,and boron carbide

Hydrodynamic voltammetry employing empirically determined mass transport coefficients is used to determine heterogeneous rate constants and transport coefficients for the ferricyanide/ferrocyanide system in 0.1 M phosphate buffer and other supporting electrolytes with turbulent tubular and rotated disk electrodes of platinum, gold, glassy carbon, carbon film, and boron carbide. Different kinetic parameters are obtained at the various electrode materials. For the platinum, gold, and boron carbide electrodes, the magnitudes of the rate parameters depend on scan direction. The nature of this hysteresis varies with the electrode material and is explained in terms of adsorbed oxide and ionic layers or other phenomena not described by simple double layer theory.