Conformer-specific and two-fold adiabatic photoisomerization of ZZ-1,4-di-(2-quinolylethenyl)benzene.

Irradiation of the ZZ stereoisomer of 1,4-di-(2'-quinolylethenyl)-benzene was found to cause direct adiabatic (one photon-two bond) isomerization to a product having the same lifetime as the EE isomer but a rather different spectrum with respect to that obtained by direct excitation of the EE one. To clarify this unexpected behaviour, the conformational equilibria of the EE stereoisomer have been studied in non-polar solvent by fluorimetry. The most abundant conformers, formed by the hindered rotation of the condensed-ring groups around the quasi-single bond with the ethenic carbons, have been characterized by the selective effect of the excitation energy on the fluorescence spectrum. The combined application of the principal component analysis allowed the separation of the spectral properties of three conformers to be achieved. Information on their structures was obtained by theoretical calculations. The results of the present conformational study clearly indicated that the fluorescence spectrum of the photoproduct of ZZ belongs to a specific component of the conformer mixture of the EE isomer.     

Application of carbon balance to submerged citric acid production by Aspergillus niger

Summary In an air-lift fermenter, the following production was obtained from 125 g sucrose in mineral medium at pH 2.5 : 15.76 g mycelium dry wt, 107.2 g citric acid anhydrous and 0.594 mol CO₂ within 138 h (run I) and 13.72 g mycelium dry wt, 114.28 g citric acid and 0.516 mol CO₂ within 144 h (run II). Initially, the carbon content of consumed sugar and products did not balance. At the end of fermentation, the carbon content of the products was 0.9%–5.5% higher than that of the consumed sugar. For the purpose of the calculations the carbon content in mycelium was accepted as 0.462.The work was a part of Project No 04.11 CPBP, topic No 2.24     

Free and conjugated gibberellins in dormancy and germination of apple seeds

Halińska, A. and Lewak, St. 1987. Free and conjugated gibberellins in dormancy and germination of apple seeds.
The presence of gibberellin A₄ (GA₄) was confirmed in partly stratified seeds of apple ( Malus domestica Borb., cv. Antonówka) by mass spectrometry of the methyl ester. Levels of free and conjugated gibberellins A₄₊₇ and A₉ changed during drying of mature seeds, during cold and warm stratification, as well as during germination of dormant and non-dormant embryos. The temporary rise in GA₄₊₇ during cold stratification and during the culture of dormant embryos as well as the lack of it under conditions of warm stratification, allowed us to postulate a role for GA₄₊₇ in the removal of dormancy. In addition, GA₉ was absent in dormant embryos and increased during cold stratification and during the culture of non-dormant embryos. This suggests the involvement of GA₉, in induction of normal development of the seedling. The equivalence between changes in free and conjugated GAs suggests that formation and hydrolysis of conjugates are involved in the control of the physiologically active levels of free GA₄₊₇ and GA₉.     

A new species of the genusLotus (Fabaceae) in North Africa

A new species,Lotus digii, has been found in Morocco growing on the coastal sandy soils. Further localities are from Algeria and Egypt. It should be expected also in Libya.     

Comparison of two methods for detection of Mollicutes (Mycoplasmatales and Acholeplasmatales) in cell cultures in The Netherlands

A total of 1949 cell cultures was tested for contamination with mollicutes by cultivation on and in mycoplasma media, 25.7% of the cell cultures was positive, 243 strains of Mycoplasma hyorhinis were isolated. Furthermore, mainly M. arginini and M. orale were detected, less often Acholeplasma laidlawii, M. fermentans and M. pneumoniae. Optimal conditions for isolation were discussed. About one third of 217 hybridoma cultures and two third of 57 myeloma cultures proved to be contaminated, all with M. hyorhinis. A DNA fluorochrome staining method (DAPI-test) was compared to cultivation for testing 1039 cell cultures. The efficiency of the DAPI-test could be estimated to be about 96% that of cultivation about 89%, but cultivation is more specific. The highest assurance is obtained when both methods are applied.