The labelling of nucleic acids by radioactive precursors in the blue-green algae Anacystis nidulans and Synechocystis aquatilis Sanv.

Summary The labelling of nucleic acids of growing cells of the blue-green algae Anacystis nidulans and Synechocystis aquatilis by radioactive precursors has been studies. A. nidulans cells most actively incorporate radioactivity from [2-¹⁴C]uracil into both RNA and DNA, while S. aquatilis cells incorporate most effectively [2-¹⁴C]uracil and [2-¹⁴C]thymine.Deoxyadenosine does not affect incorporation of label from [2-¹⁴C]thymidine into DNA, but weakly inhibits [2-¹⁴C]thymine incorporation into both nucleic acids and significantly suppresses the incorporation of [2-¹⁴C]uracil.The radioactivity from [2-¹⁴C]uracil and [2-¹⁴C]thymine is found in RNA uracil and cytosine and DNA thymine and cytosine. The radioactivity of [2-¹⁴C]thymidine is incorporated into DNA thymine and cytosine. These results and data of comparative studies of nucleic acid labelling by [2-¹⁴C]thymine and [5-methyl-¹⁴C]thymine suggest that the incorporation of thymine and thymidine into nucleic acids of A. nidulans and S. aquatilis is accompanied by demethylation of these precursors. In this respect blue-green algae resemble fungi and certain green algae.     

Prediction of the three-dimensional structure of aflatoxin of Aspergillus flavus by homology modelling

Aflatoxins are polyketide-derived secondary metabolites produced by Aspergillus spp. The toxic effects of aflatoxins have adverse consequences for human health and agricultural economics. The aflR gene, a regulatory gene for aflatoxin biosynthesis, encodes a protein containing a zinc-finger DNA-binding motif. AFLR-Protein three-dimensional model was generated using Robetta server. The modeled AFLR-Protein was further optimization and validation using Rampage. In the simulations, we monitored the backbone atoms and the C-α-helix of the modeled protein. The low RMSD and the simulation time indicate that, as expected, the 3D structural model of AFLR-protein represents a stable folding conformation. This study paves the way for generating computer molecular models for proteins whose crystal structures are not available and which would aid in detailed molecular mechanism of inhibition of aflatoxin.     

Role of NAD(P)H:Quinone Oxidoreductase Encoded by drgA Gene in Reduction of Exogenous Quinones in Cyanobacterium Synechocystis sp. PCC 6803 Cells

Insertion mutant Ins2 of the cyanobacterium Synechocystis sp. PCC 6803, lacking NAD(P)H:quinone oxidoreductase (NQR) encoded by drgA gene, was characterized by higher sensitivity to quinone-type inhibitors (menadione and plumbagin) than wild type (WT) cells. In photoautotrophically grown cyanobacterial cells more than 60% of NADPH:quinone-reductase activity, as well as all NADPH:dinoseb-reductase activity, was associated with the function of NQR. NQR activity was observed only in soluble fraction of cyanobacterial cells, but not in membrane fraction. The effects of menadione and menadiol on the reduction of Photosystem I reaction center (P700(+)) after its photooxidation in the presence of DCMU were studied using the EPR spectroscopy. The addition of menadione increased the rate of P700(+) reduction in WT cells, whereas in Ins2 mutant the reduction of P700(+) was strongly inhibited. In the presence of menadiol the reduction of P700(+) was accelerated both in WT and Ins2 mutant cells. These data suggest that NQR protects the cyanobacterial cells from the toxic effect of exogenous quinones by their reduction to hydroquinones. These data may also indicate the probable functional homology of Synechocystis sp. PCC 6803 NQR with mammalian and plant NAD(P)H:quinone oxidoreductases (DT-diaphorases).     

Mapping the amino acid properties of constituent nucleoporins onto the yeast nuclear pore complex

Visualization of molecular structures aids in the understanding of structural and functional roles of biological macromolecules. Macromolecular transport between the cell nucleus and cytoplasm is facilitated by the nuclear pore complex (NPC). The ring structure of the NPC is large and contains several distinct proteins (nucleoporins) which function as a selective gate for the passage of certain molecules into and out of the nucleus. In this note we demonstrate the utility of a python code that allows direct mapping of the physiochemical properties of the constituent nucleoporins on the scaffold of the yeast NPC׳s cytoplasmic view. We expect this tool to be useful for researchers to visualize the NPC based on their physiochemical properties and how it alters when specific mutations are introduced in one or more of the nucleoporins. The code developed using Python is available freely from the authors.     

Dual-photon excitation of albumin

Fluorescence emission after two-photon excitation at 580 nm is observed in albumin by means of Nd:YAG laser at room temperature. The two-photon excitation spectral range 550-590 nm was obtained. The experimental results show that albumin fluorescence originates from tryptophan residues.     

Mycelial wastes of penicillin fermentation as glue components]

A new trend in the rational use of micelial wastes after antibiotics fermentation was elaborated. The modification of P. chrysogenum micelium by means of acid and alkaline solutions allows to use it as bone glue component. As a result physico-mechanical characteristics of the mixture increase, while the ratio cost-price decreases. The obtained glue composition can be used in the production of glue paper tape, for paper and wood glue.     

The treatment of isolated genera

Problems presented by genera, or small groups of genera, which have been given family rank are reviewed, and the genera are divided into a number of categories according to the closeness of their affinity to other genera or families. Satellite genera that stand in close relation to families should be united with them. Binary families, that have been divided into two (or more) related families, should be re–united. Families connected by linking genera, should, logically, be united but practical considerations usually prevent this. Clusters of diverse but more or less distantly related genera present unusual problems, being treated either as several, often monogeneric families or as a loosely structured family. Truly isolated genera must be given family and often ordinal rank.