Spectral features of amines of 2-phenylbenzazoles upon interaction with DNA

Absorption and fluorescent spectra of various synthetic aminophenyl derivatives of benzoxazole, benzothiazole and benzimidazole have been studied to estimate the efficiency of their binding with DNA. The significance of different functional groups of the fluorochromes for their interaction with DNA was determined, and main demands are formulated to the compounds to be used as potential fluorescent probes for DNA studies.     

Conformation-activity relations of dermorphin and its pentapeptide analogs

Low-energy peptide backbone structures of dermorphin (DM), amide of its N-terminal pentapeptide (DM 1-5) and DM 1-5 analogues with substitutions of Gly4 for Leu, D-Gln, Aal or Tal were determined by energy calculations. The above analogues were shown to possess different affinities toward opiate receptors of mu-type. The comparison of low-energy backbone structures of DM, DM 1-5 and its analogues resulted in development of the dermorphin "biologically active" conformation being characteristic of its binding with mu-type receptors. The specific binding of dermorphin to this receptor apparently depends on the conformation of the whole N-terminal pentapeptide.     

Cyclic analogs of des-Arg9-[Leu8]bradykinin

Four cyclic derivatives of des-Arg9[Leu8]bradykinin have been obtained by classical methods of peptide chemistry. They are cyclo-(-X-Arg-Pro-Pro-Gly-Phe-Gly-Pro-Leu-), where X=Lys or none, and cyclo-(Y-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Leu-), where Y= Lys or Orn. Peptide bonds have been formed by the pentafluorophenylester method, and cyclization has been carried out in a diluted dioxane solution with 40% yield. Subsequent cleavage of protecting groups was made by treatment with hydrogen fluoride. The products obtained were purified by droplet counter-current chromatography. These substances liberate histamine from the rat mast cells comparably to bradykinin and fail to produce myotripic and vascular effects.     

Isolation and physico-chemical properties of a protein, included in an endotoxin from Yersinia pseudotuberculosis

A major protein of the endotoxin from Yersinia pseudotuberculosis was isolated from the complex lipid A--protein by treatment with SDS and triton X-100 followed by gel-chromatography on Sephacryl S-300. Protein has apparent molecular mass 40 kDa and alanine as N-terminal amino acid residue. CD and IR spectroscopy conformational changes of the protein molecule in the process of its isolation. The thermal and pH stabilities of the protein were investigated by the methods of intrinsic fluorescence and differential scanning microcalorimetry. The isolated protein revealed two thermal transitions (at 30-35 and 50-55 degrees C), which depend on Ca2+ concentration.     

Correction of lipid peroxidation in stress with the peptide bioregulator thymopentin

Experiments on rats subjected to acute stress have revealed protective effect of thymopentin pentapeptide on somatic disorders and the state of the antioxidation system and the processes of lipid peroxidation in blood and brain.     

The effect of Mg 2+ ions on the properties of various strains of Yersinia pestis

The strains of Yersinia pestis that restrict their growth on the media deficient for Mg2+ ions at 37 degrees C have been found. The bacterial cell lysis is registered under these conditions. The effect of Yersinia pestis own plasmids on the level of growth restriction in the absence of Mg2+ ions has been studied. The phenomenon is not connected with the presence of the plasmid determining Ca2(+)-dependence. The presence of 6Md plasmid coding for pesticinogenicity increased the frequency of colony formation, while the heavy plasmid determining the production of "mouse" toxin favoured the increase in growth restriction on Mg2(+)-less media. The clones growing under the latter conditions acquire the rearrangements in the DNA of the plasmid coding for the "mouse" toxin.     

Lactate dehydrogenase-induced conformational changes of F-actin in myosin-free ghost single fibres

The changes in conformation of F-actin induced by the binding of the glycolytic enzyme lactate dehydrogenase were studied in myosin-free single ghost muscle fibres. The formation of the lactate dehydrogenase-F-actin complex was accompanied by changes in the parameters of intrinsic (tryptophan) and extrinsic (rhodaminyl-phalloin) polarized fluorescence of ghost muscle fibre F-actin. Lactate dehydrogenase stimulated actin-activated Mg2+-ATPase of myosin subfragment 1 by 30%. F-actin of ghost fibres depressed lactate dehydrogenase activity to 20% of the initial values. It is suggested that the energy-providing mechanism is coupled with that of muscle contraction through conformational changes in F-actin.     

Improved chemistry for oligodeoxyribonucleotide synthesis substantially improves restriction enzyme cleavage of a synthetic 35mer.

Two DNA duplexes of identical sequence and 35 nt in length were synthesized by an original and a highly improved version of phosphoramidite chemistry. By base composition analysis, DNA synthesized by improved chemistry (termed DMTS-imp) contained no detectable modified bases while DNA synthesized by the original chemistry (termed DMTS-std) had a large number of modifications. Under optimal reaction conditions, HhaI and RsaI cleaved the DMTS-std duplex to 76-77% completion and the DMTS-imp duplex to 96-99% completion. Restriction analysis and piperidine treatment yielded estimates of approximately 3.0% modified nucleotides in DMTS-std and approximately 1.0% in DMTS-imp. Overall, the improvements in chemistry increased the restriction efficiency of synthetic DNA up to 10-fold.     

400 MHz two-dimensional nuclear Overhauser spectroscopy on anesthetic interaction with lipid bilayer

Interaction between a volatile anesthetic, methoxyflurane, and dipalmitoylphosphatidylcholine (DPPC) vesicle membrane was analyzed by nuclear Overhauser effect (NOE) difference spectroscopy and two-dimensional nuclear Overhauser spectroscopy (NOESY). The NOE difference spectra were obtained by selectively irradiating methoxy protons (hydrophobic end) of the anesthetic: a negative nuclear Overhauser effect of -2.94% was observed with the choline methyl protons of DPPC. The NOESY spectra revealed a cross-peak between the anesthetic methoxy protons and the choline methyl protons. A dipole-dipole interaction exists between the hydrophobic end of the anesthetic and the hydrophilic head group of DPPC. No other cross-peaks were observed. The anesthetic orients itself at the membrane/water interface by interacting with the hydrophilic surface of the DPPC membrane, leaving the hydrophilic end of the anesthetic molecule in the aqueous phase. The preferred residence site of dipolar volatile anesthetics is the membrane/water interface.     

Elevated levels of the guanine nucleotide binding protein, Go, are associated with differentiation of neuroblastoma x glioma hybrid cells

Each of a range of pharmacological agents which function to increase intracellular levels of cAMP caused a morphological 'differentiation' of neuroblastoma x glioma hybrid, NG108-15, cells grown in tissue culture. Associated with this differentiation, increased incorporation of [32P]ADP-ribose catalysed by pertussis toxin was noted into a band of some 39-40 kDa in membranes derived from these cells. Immunoblotting using two antipeptide antisera which identify different regions of Go alpha demonstrated marked increases in the levels of this polypeptide in membranes of the differentiated cells. However, levels of the beta-subunit did not increase appreciably with differentiation.