Physiologo-biochemical properties of a strain of Beijerinckia mobilis 1phi Phn+--a degrader of polycyclic aromatic hydrocarbons

Beijerinckia mobilis 1f capable of degrading polycyclic aromatic hydrocarbons (PAHs) was isolated from a soil contaminated with creosote. Strain 1f could utilize phenanthrene and naphthalene as the sole sources of carbon. The mean rate of phenanthrene degradation during culture growth was 7-8 micrograms/(ml h). After cultivation under nonselective conditions, strain 1f retained its ability to degrade phenanthrene. Cometabolism considerably widened the range of PAHs that could be transformed by strain 1f. The strain was able to grow in a mineral medium with creosote as the sole source of carbon. After 30 days of cultivation in this medium, the total concentration of PAHs decreased from 665.5 mg/l to 170 mg/l.     

Endocytosis of EGF-receptor complexes at various cell cycle stages

Parameters of EGF-receptor complex endocytosis have been studied in the early and late G1 phase and in mitosis. As a model, mouse mammary epithelial cells HC11 were used, whose growth depends on EGF presence in the medium. The Scatchard analysis has demonstrated that the surface receptors are represented by two receptor populations: 4800 high affinity (KD = 10(-11) M) receptors, and 73,000 low affinity (KD = 4.10(-9) M) receptors. Incubation of cells with the growth factor (5 ng/ml) resulted in a decrease in 125I-EGF binding, with its level being low until entering the S-phase. Under these conditions, receptors disposed on the plasma membrane presented a homogeneous population (KD = 8.10(-11) M, 14,000 receptors per cell). No reliable difference was revealed between the EGF-receptor complexes, internalized in early and late G1 phases, in respect to the internalization rate, level of recycling, degradation, and dynamics of compartmentalization. However, endocytosis of EGF-receptor complexes was found to be completely blocked in mitosis at the stage of internalization.     

Sensitized photomodification of DNA with binary systems of oligonucleotide conjugates. IV. Photoinduced electron transfer

The photomodification of single-stranded DNA sensitized to visible light (450-580 nm) by a binary system of oligonucleotide conjugates complementary to adjacent DNA sequences was studied. One oligonucleotide carries a residue of the photoreagent p-azidotetrafluorobenzaldehyde hydrazone at its 3'-terminal phosphate, and the other has a residue of the sensitizer, perylene or 1,2-benzanthracene, at the 5'-terminal phosphate. The rate of photomodification sensitized by the perylene derivative is 300,000-fold higher than the rate of photomodification in the absence of the sensitizer. Since the excitation energy of perylene is lower than the energy necessary for the initiation of azide photodecomposition, it is likely that the sensitization in the complementary complex occurs by electron transfer from the azido group of the photoreagent to the excited sensitizer. The sensitization by the 1,2-benzanthracene oligonucleotide derivative occurs by means of singlet-singlet energy transfer, which enables this sensitizer to act as a unconsumable catalyst each molecule of which is able to initiate the photomodification of more than 20 DNA molecules. By both mechanisms, the photomodification occurs with high specificity on the G11 residue of the target DNA. The degree of sensitized photomodification reaches 72%.