Showing papers by "University of Seville published in 1973"
TL;DR: A model with a photoreceptor, early and late linear transducers, a logarithmic transducer and a growth-controlling element is proposed for the information channel of the phototropic response.
Abstract: A collection of mutants of Phycomyces blakesleeanus with abnormal phototropism is divided into phenotypic groups on the basis of the results of five routine tests of sensory function. The three classes of mutants found permit the formulation of a network of sensory pathways, linking the three types of receptor (light, chemical, gravity) with the three types of response (sporangiophore tropisms, initiation of sporangiophores, induction of β-carotene synthesis). A model with a photoreceptor, early and late linear transducers, a logarithmic transducer and a growth-controlling element is proposed for the information channel of the phototropic response. Mutagenesis and the possible functional relationship between carotenes and phototropism are discussed.
200 citations
TL;DR: Tungstate very efficiently inhibits growth of the microorganism in media with nitrate when either nitrite or ammonia are substituted for nitrate as the nitrogen source, growth is unaffected by tungstate concentrations which otherwise completely suppress growth on nitrate.
Abstract: The assimilatory nitrate reductase of the N2-fixing bacterium Azotobacter chroococcum has been prepared in a soluble form from cells grown with nitrate as the nitrogen source, and some of its properties (electron donors and cofactors, Kmvalues for substrates, molecular weight, inhibitors, activators, etc.) have been studied. The enzyme is of an inducible nature and can exist in two interconvertible forms, either active or inactive.
70 citations
TL;DR: Ammonia promotes in vivo the conversion of the active form of nitrate reductase into its inactive form by indirectly causing the reduction of the enzyme.
66 citations
TL;DR: The active form of Chlorella fusca nitrate reductase can be reversibly converted into its inactive form by reduction with NADH in the presence of ADP as mentioned in this paper.
61 citations
TL;DR: The assimilatory nitrite reductase of the N(2)-fixing bacterium Azotobacter chroococcum was prepared in a soluble form from cells grown aerobically with nitrate as the nitrogen source, and some of its properties have been studied.
Abstract: 1. The assimilatory nitrite reductase of the N2-fixing bacterium Azotobacter chroococcum was prepared in a soluble form from cells grown aerobically with nitrate as the nitrogen source, and some of its properties have been studied. 2. The enzyme is a FAD-dependent metalloprotein (mol.wt. about 67000), which stoicheiometrically catalyses the direct reduction of nitrite to NH3 with NADH as the electron donor. 3. NADH–nitrite reductase can exist in two either active or inactive interconvertible forms. Inactivation in vitro can be achieved by preincubation with NADH. Nitrite can specifically protect the enzyme against this inactivation and reverse the process once it has occurred. 4. A. chroococcum nitrite reductase is an adaptive enzyme whose formation depends on the presence of either nitrate or nitrite in the nutrient solution. 5. Tungstate inhibits growth of the microorganism very efficiently, by competition with molybdate, when nitrate is the nitrogen source, but does not interfere when nitrite or NH3 is substituted for nitrate. The addition of tungstate to the culture media results in the loss of nitrate reductase activity but does not affect nitrite reductase.
50 citations
TL;DR: The assimilatory nitrate-reducing system of the yeast Torulopsis nitratophila has been characterized and it is shown that this enzyme may exist in an active or inactive interconvertible form, according to its redox state.
35 citations
TL;DR: The Cu(II)-hydrazine-6-methylpicolinaldehyde system in solution is studied and a new mode of homogeneous colour development, based on the exchange of groups in the ligand with the metal ion present, is described.
14 citations
TL;DR: The synthesis and analytical properties of 3-hydroxypicolinaldehyde azine (3-OH-PAA), salicyladealdehyde azine and picolinalde Hyde azine are described and 3-OH -PAA is isolated for the first time.
10 citations
TL;DR: Both ferrous complexes can be oxidized to the ferric complex; this reaction is reversible.
9 citations
TL;DR: The use of furfural thiosemicarbazone as a gravimetric reagent for palladium is described and the optimum analytical conditions for precipitation of the palladium complex are investigated.
9 citations
TL;DR: These results support the concept that the F factor is integrated into the Hfr chromosome during vegetative growth, but is autonomous in the F(+) strains and could serve as an assay for episomal localization.
Abstract: Mutations affecting utilization of lactose and resistance to the male-specific phages f1, f2, and Qβ tend to occur simultaneously more often than expected by chance in Hfr strains whose origin of transfer is close to the genes for lactose utilization, but not in F+ strains. Strains derived from the Hfr, but exhibiting poor ability to transfer early chromosomal genes, may or may not show this comutation phenomenon. These results support the concept that the F factor is integrated into the Hfr chromosome during vegetative growth, but is autonomous in the F+ strains and could serve as an assay for episomal localization.