Effect of prostaglandin E1 on the cyclic adenosine-3',5'--monophosphate system and radiosensitivity of B-82 cells cultured in vitro

The cyclic AMP (cAMP) system of mice fibroblasts L, clone B-82 has been studied. B-82 cells possess receptors to prostaglandin E1 (PGE1) and are deficient in beta-adrenoreceptors. It has been shown that 10 mM NaF, 1.10(-4) M GTP and 1.10(-5) M PGE1 stimulate adenylate cyclase of B-82 cells. PGE1 causes increase in the intracellular content of cAMP and protects B-82 cells against irradiation. Specifict beta-agonist isoproterenol fails to modulate adenylate cyclase activity and does not change cAMP content in B-82 cells. Isoproterenol has no effect on the B-82 cells radiosensitivity, although it is known to be a potent radioprotector. It is presumed that the stimulation of cAMP system by radioprotector is necessary for the performance of radioprotective effect.     

Prenylated stilbenes from peanut root mucilage

Seven prenylated stilbenes were identified by combined HPLC-PAD-APCI/MSn analysis of an extract of mucilage isolated from peanut (Arachis hypogaea L.) root tips. The principal constituent was assigned the structure 4-(3-methyl-but-1-enyl)-3, 5-dimethoxy-4'-hydroxy-trans-stilbene. The common name mucilagin A is proposed for this novel compound. Its concentration in the mucilage was estimated at 250 microg/g (wet weight basis). The large body of literature on the anti-microbial properties of plant-derived stilbenes suggests that compounds detected in peanut mucilage may play a role in regulating root-soil pathogen interactions.     

Population Dynamics of Atlantic Chub Mackerel Scomber colias at the Multispecies Fishery

Journal of Ichthyology - Population dynamics of Atlantic chub mackerel Scomber colias in the central-eastern Atlantic Ocean is described by the Schaefer production model using the fish abundance...     

Modular Nanotransporter with P21 Fragment Inhibits DNA Repair after Bleomycin Treatment

Modular nanotransporter (MNT) with C-terminal fragment of the p21 protein was synthesized and characterized, and its effect on DNA lesions was studied. This p21 fragment in MNT can significantly inhibit DNA repair in A431 human carcinoma cells after bleomycin treatment.     

Targeted intracellular site-specific drug delivery: photosensitizer targeting to melanoma cell nuclei

A number of drugs are regarded as possessing local activity because their effects take place at an extremely short distance from their location site in the cell. The response of different cellular compartments to these effects is different. Such substances as photosensitizers (PSs), which are used in photodynamic cancer therapy, should be targeted to the cell compartments where their effect is the most pronounced. This study describes the construction and properties of the chimeric modular recombinant transporters (MRTs) expressed in Escherichia coli and used for PS targeting. These constructs include (1) the alpha-melanocyte-stimulating hormone as a ligand module, which is internalized by the target cells (mouse melanoma); (2) the optimized SV40 large T-antigen nuclear localization signal; (3) the hemoglobin-like protein from E. coli as a carrier module; (4) the endosomolytic module, the translocation domain of the diphtheria toxin. These MRTs were used for PS targeting to the mouse melanoma cell nuclei, the most PS-damaged intracellular compartment, which resulted in a PS photocytotoxic effect increase of several orders of magnitude. In our opinion, MRTs, which target locally active drugs into the desired cell compartment and thereby enhance the drug response, represent a new generation of the pharmacological agents.     

The limit of accuracy of protein modeling: influence of crystal packing on protein structure

The size of the protein database (PDB) makes it now feasible to arrive at statistical conclusions regarding structural effects of crystal packing. These effects are relevant for setting upper practical limits of accuracy on protein modeling. Proteins whose crystals have more than one molecule in the asymmetric unit or whose structures were determined at least twice by X-ray crystallography were paired and their differences analyzed. We demonstrate a clear influence of crystal environment on protein structure, including backbone conformations, hinge-like motions and side-chain conformations. The positions of surface water molecules tend to be variable in different crystal environments while those of ligands are not. Structures determined by independent groups vary more than structures determined by the same authors. The use of different refinement methods is a major source for this effect. Our pair-wise analysis derives a practical limit to the accuracy of protein modeling. For different crystal forms, the limit of accuracy (C(alpha), root-mean-square deviation (RMSD)) is approximately 0.8A for the entire protein, which includes approximately 0.3A due to crystal packing. For organized secondary elements, the upper limit of C(alpha) RMSD is 0.5-0.6A while for loops or protein surface it reaches 1.0A. Twenty percent of exposed side- chains exhibit different chi(1+2) conformations with approximately half of the effect also resulting from crystal packing. A web based tool for analysis and graphic presentation of surface areas of crystal contacts is available (http://ligin.weizmann.ac.il/cryco).     

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.