Synthesis and characterization of three covalently linked porphyrin-phthalocyanine pentamers with nucleophilic substitution

In this paper the synthetic methods of three covalently linked porphyrin-phthalocyanine heteropentamers, containing four units of porphyrin linked to a central phthalocyanine (Mpor-LPc; M = 2H, Fe, L = Zn, Fe), are described. The synthetic strategy is on the basis of nucleophilic substitution reactions between [1,8,15,22-tetra nitro phthalocyanines] and [5-(4-hydroxy phenyl)-10,15,20-triphenyl porphyrins] as the phenolic alcohols. Porphyrins are linked with oxygen as spacer through meso position of phenyl group to phthalocyanines. These macromolecules were characterized by ¹H NMR, UV-Vis, IR, fluorescence and mass spectroscopy. The electronic absorption spectrums of the hetero-dyad systems changed significantly upon coupling and showed a great red shift in the phthalocyanine Q-bands. These changes confirm the electron-donating effects of the porphyrin units and the extension of conjugated п-systems. The emission spectra of the products supports intramolecular energy and charge transfer between the sub-units.     

Inhibition of lipid peroxide decomposition by compounds which bind with cytochrome p-450

The kinetics of lipid peroxide decomposition catalysed by microsomal enzymes and inhibited by SKF-525 A, hexobarbital, phenobarbital and aniline were investigated. The results indicate that the in vitro interaction of hexobarbital and SKF-525 A (type I binding compounds) with microsomal cytochrome p-450 inhibits the peroxidase activity while the in vitro interaction of aniline (type II binding compound) only slightly affect the peroxidase activity. It is suggested that LAHPO and type I binding compounds are competing for the hydrophobic binding site on cytochrome p-450, while type II binding compounds such as aniline negate electron transfer non-competitively by combining with the heme.     

Seasonal variations in sterol composition of Delesseria sanguinea (Ceramiales,Rhodophyta)

On Normandy coasts, the red alga Delesseria sanguinea perennates by its stipe; fronds grow in January and disappear in June. Seasonal variations in sterol composition in relation to the biology of D. sanguinea are reported. Sterols in cellular membranes are free or conjugated by esterification with fatty acids, heterosides or lipid complexes like phospholipids. Both kinds of sterols were analyzed by GC-MS. The major sterol (80%) found in fronds was cholesterol whereas in stipes, cholesterol was also the major sterol in spring, but in September, an important reduction in cholesterol yield was noted with proportional increase in sitosterol content. It appears that cholesterol is synthesized in fronds in spring, then transferred to the stipe, which loses an important amount of cholesterol with loss of the blades.     

High Expression of the HNK-1/L2 Carbohydrate Epitope in the Major Glycoproteins of Shark Myelin

The major 24- and 28-kDa glycoproteins in shark PNS and CNS myelin express high levels of the adhesion-associated HNK-1/L2 carbohydrate epitope. The 28-kDa protein, but not the 24-kDa protein, cross-reacts strongly with one of two anti-bovine P0 antisera not previously tested against fish myelin proteins. Shark PNS and CNS myelin also contains smaller amounts of high-molecular-weight HNK-1-positive proteins, including a prominent broad band in the 65-85-kDa range. Although myelin-associated glycoprotein (MAG) is well known to react with HNK-1 in some mammals, monoclonal and polyclonal anti-MAG antibodies did not react with the high-molecular-weight HNK-1-positive material in shark myelin, a result suggesting that it is not a MAG-like protein. The high expression of the HNK-1/L2 epitope in glycoproteins of shark myelin, including the major P0-related ones, suggests that this adhesion-related carbohydrate structure may have had an important role in the molecular evolution of the myelinating process.     

Circular dichroism studies on the alpha-D-galactopyranosyl binding lectin isolated from the seeds of Bandeiraea simplicifolia.

The conformation of the alpha-D-galactopyranosyl binding lectin isolated from Bandeiraea simplicifolia seeds has been investigated over a broad range of pH in the presence of various solvents by circular dichroism (CD) spectroscopy in the region 200-300 nm. Analyses of the spectra obtained on the native protein show the lectin to contain a considerable proportion of beta structure (30-40%). The native conformation was found to be largely insensitive to changes in pH, but was influenced by sodium dodecyl sulfate or trifluoroethanol. Alterations in conformation in the presence of these agents were reflected in the CD spectra and show the presence of alpha helix under these conditions. These changes in conformation are accompanied by a loss in polysaccharide-precipitating activity. The protein is irreversibly denatured in 8 M urea. Neither removal of the intrinsic calcium ions from the protein nor addition of methyl alpha-D-galactopyranoside induces any appreciable change in the CD spectra of the protein although the former treatment abolishes the polysaccharide-precipitating capacity of the lectin. The conformational data obtained in the present study are compared with data available from conformational studies of other lectins and leads to the hypothesis that most lectins probably contain beta structure as the predominant conformational feature.     

The solution behavior of the bovine myelin basic protein in the presence of anionic ligands. Binding behavior with the red component of trypan blue and sodium dodecyl sulfate.

The interaction of the azo dye (2,3'-dimethyldiphenyl-7-azo-8-amino-1-napthol 3,6-disulfonic acid (TBR) and sodium dodecyl sulfate with the bovine myelin basic protein has been studied using absorbance, circular dichroism and 220 MHz PMR spectroscopy. Additional analyses of the binding reaction were carried out using light scattering, ultracentrifugal and electrophoretic techniques. A procedure for preparing pure TBR was developed. A modified structure for this synthesized TBR has been suggested. The mechanism of TBR binding to the myelin basic protein was found to be metachromatic. In addition, the interaction of TBR with the basic protein which gives rise to aggregation of the dye bound species was found to be analogous to the model proposed by Schwarz, G. and Seelig-L?ffler, A. ((1975) Biochim. Biophys. Acta 379, 125-138) to explain the binding of acridine orange with poly (alpha-L-glutamic acid). PMR spectral analyses suggested that arginine residues provide the majority of primary sites of attachment on the basic protein for TBR. The effect of sodium dodecyl sulfate binding with the bovine myelin basic protein was found to induce a minimal change in the conformation of the protein. The induction of only about 20% alpha helial structure could be demonstrated and the binding was reversed by raising the solution temperature to 73 degrees C. The difference in the observed behavior of basic protein arising from TBR binding as opposed to the binding of sodium dodecyl sulfate is viewed as resulting from two different binding mechanisms. The binding behavior of TBR is primarily a consequence of charge-charge interaction while the binding effects of sodium dodecyl sulfate are a consequence of hydrophobic interaction. The sodium dodecyl sulfate binding acts as a shield which limits charge-charge interaction in the basic protein molecule thus preventing aggregate formation while TBR imposes no such restraints.