Solvation of platinum anti-cancer drugs in methanol-water mixtures

Solubilities and transfer chemical potentials of carboplatin, cisplatin, iproplatin, and several related platinum complexes have been determined in methanol-water mixtures. the range of solvation behaviour is discussed in relation to possible oral administration of complexes of this type.     

Matter production processes ofReineckia carnea Kunth,an evergreen forest floor herb in the warm-temperate region of Japan

The growth and matter production were examined forReineckia carnea, an evergreen herb growing on the forest floor in a warm-temperate region. Seasonal change in the biomass of plants growing in the field was estimated from the harvested sample plants. Carbohydrate contents and respiration rates were measured for analysis of dry matter economy. Light intensity and temperature on the forest floor were periodically measured. In mid-spring the biomass reached a maximum which was about half again its minimum value, found in autumn. Two phases, the productive phase in cooler seasons and the developmental phase in warmer seasons, were distinguished from the annual growth pattern of this plant. In cooler seasons, positive net production was found without any morphological changes, resulting in active accumulation of reserves which were mainly soluble sugars. This high net production seems to be closely related to the favorable light conditions and low respiratory losses. In warmer seasons, though new organs were developed, net production remained low or was even negative. The morphological development of this plant in these seasons depended mostly on reserves previously accumulated. This characteristic feature of annual matter economy is considered to be common to evergreen plants on the forest floor in warm regions.     

Molecular distribution of zinc in biliary and pancreatic secretions

Rat bile and pancreatic fluid were examined for the presence of low molecular weight zinc complexes. Fluids were collected separately by cannulation, and zinc distribution in collected samples was analyzed by gel filtration on Sephadex G-50. Most of the zinc in bile was associated with low molecular weight zinc complexes; only a small amount of zinc was present in the high molecular weight fraction. In contrast, pancreatic secretions did not contain low molecular weight zinc complexes, but there were considerable amounts of zinc bound to high molecular weight compounds. The addition of zinc to bile resulted in an increased amount of zinc in the low molecular weight fraction, while the addition of zinc to pancreatic fluid resulted primarily in an increase in zinc bound to the high molecular weight components. Like pancreatic fluid, homogenates of pancreatic tissue had no low molecular weight zinc complex. In rats whose bile and pancreatic fluid were removed and not returned into the intestine, the amount of zinc bound to low molecular weight complexes in intestinal homogenates was reduced. This alteration of the molecular distribution of zinc in intestinal homogenates by removal of bile and pancreatic fluid suggests the potential importance of low molecular weight zinc complexes for zinc homeostasis.     

Comparison of isolated peanut agglutinin receptor glycoproteins from human,bovine and porcine erythrocyte membranes

Affinity chromatography has been used to isolate and compare the peanut agglutinin receptors from neuraminidase-treated human, bovine and porcine erythrocyte membranes. Passage of Triton X-100-solubilised membrane material through either Sepharose- or acrylamide-based affinity columns resulted in the reversible binding of receptor molecules to the immobilised lectin. Elution with 0.2M galactose released specifically bound glycoprotein fractions, the composition and molecular weights of which were determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate.Carbohydrate analysis by gas chromatography identified these bound glycoprotein fractions as the major sources of the $\text{O-}\text{glycosidic-linked}$ disaccharide $\text{galactosyl}\text{-β-(1 → 3)-N-}\text{acetylgalactosamine}$ in these membranes. It is suggested that these isolated fractions represent a discrete population of glycoproteins within the membranes studied, which possess both $\text{O-}\text{glycosidic}$- and $\text{N-}\text{glycosidic-linked}$ carbohydrates.     

Biliprotein assembly in the hemidiscoidal phycobilisomes of the thermophilic cyanobacterium Mastigocladus laminosus Cohn. Characterization of dissociation products with special reference to the peripheral phycoerythrocyanin-phycocyanin complexes

The dissociation products of isolated phycobilisomes of Mastigocladus laminosus were separated and analyzed by ultracentrifugation and, in part, by isoelectric focusing. With the exception of the allophycocyanin core, the sedimentation constants of peripheral phycocyanin- and phycoerythrocyanin-phycocyanin complexes lay in the range of 6 to 17S. The latter was represented by a 17S aggregate of two hexameric phycocyanins (dodecamer, dipartite unit). A complex with an absorption maximum at 610 nm (phycocyanin) and a shoulder at 580 nm (phycoerythrocyanin), a fluorescence emission maximum at 645 nm and a sedimentation constant of 11 S is described as a heterogeneously composed hexamer of ()₃-phycoerythrocyanin-()₃-phycocyanin. It was stable under extended dissociation in the cold and under isoelectric focusing. An aggregate of 14 S with an absorption maximum at 576 nm and a shoulder in the fluorescence emission spectrum at 625 nm (phycoerythrocyanin) in addition to the maximum at 645 nm (phycocyanin) is interpreted as a polar phycoerythrocyanin/ phycoerythrocyanin-phycocyanin complex. Combining these complexes with phycocyanin dodecamers creates peripheral rods of the phycobilisome. A proposal of the phycobiliprotein distribution within the phycobilisome of M. laminosus is presented.Abbreviations APC allophycocyanin - PC phycocyanin - PE phycoerythrin - PEC phycoerythrocyanin     

Uptake and metabolism of carbohydrates by epidermal tissue

Isolated epidermis of Commelina communis L. and Tulipa gesneriana L. assimilated ¹⁴CO₂ into malic acid and its metabolites but not into sugars or their phosphates; epidermis could not reduce CO₂ by photosynthesis and therefore must be heterotrophic (Raschke and Dittrich, 1977). If, however, isolated epidermis of Commelina communis was placed on prelabelled mesophyll (obtained by an exposure to ¹⁴CO₂ for 10 min), radioactive sugars appeared in the epidermis, most likely by transfer from the mesophyll. Of the radioactivity in the epidermis, 60% was in sucrose, glucose, fructose, 3-phosphoglyceric acid and sugar phosphates. During a 10-min exposure to ¹⁴CO₂, epidermis in situ incorporated 16 times more radioactivity than isolated epidermal strips. Isolated epidermis of Commelina communis and Tulipa gesneriana took up ¹⁴C-labelled glucose-1-phosphate (without dephosphorylation), glucose, sucrose and maltose. These substances were transformed into other sugars and, simultaneously, into malic acid. Carbons-1 through-3 of malic acid in guard cells can thus be derived from sugars. Radioactivity appeared also in the hydrolysate of the ethanol-insoluble residue and in compounds of the tricarboxylic-acid cycle, including their transamination products. The hydrolysate contained glucose as the only radioactive compound. Radioactivity in the hydrolysate was therefore considered an indication of starch. Starch formation in the epidermis began within 5 min of exposure to glucose-1-phosphate. Autoradiograms of epidermal sections were blackened above the guard cells. Formation of starch from radioactive sugars therefore occurred predominantly in these cells. Epidermis of tulip consistently incorporated more ¹⁴C into malic and aspartic acids than that of Commelina communis (e.g. after a 4-h exposure to [¹⁴C]glucose in the dark, epidermis, with open stomata, of tulip contained 31% of its radioactivity in malate and aspartate, that of Commelina communis only 2%). The results of our experiments allow a merger of the old observations on the involvement of starch metabolism in stomatal movement with the more recent recognition of ion transfer and acid metabolism as causes of stomatal opening and closing.Abbreviation G-1-P glucose-1-phosphate     

Transference of the high molecular weight carbohydrate sequences of fetuin to the surface of carrot embryo protoplasts

A method is described for the removal of the carbohydrate sequences of glycoproteins, and their covalent attachment to hydrocarbon chains. These synthetic membrane components may then be incorporated into liposome and cell membranes. Pronase-liberated glycopeptides derived from fetuin were linked by a reduced Schiff's base linkage to tetradecyl aldehyde. The resulting glycolipid was incorporated by external addition, into phosphatidylcholine liposomes. Glycolipid transfer to these liposomes rendered them suseptible to agglutination by wheat germ lectin, which binds N-acetylneuraminic acid, the terminal carbohydrate of the high molecular weight fetuin sugar sequence. Sequential removal of the terminal sugars, and subsequent agglutination behaviour towards various lectins, suggests that the carbohydrate sequence had been transfered intact. The glycolipid was incorporated into plant protoplast membranes by incubation with glycolipid-containing liposomes for 2 h at 37°C. These synthetic glycolipids may find a use in the study of carbohydrate-based recognition systems in animal and plant membranes. In addition they may prove useful in the development of cell and membrane tagging and handling techniques, by the insertion of sugar groups not normally present in these membranes.     

C-n.m.r. spectral study of C reductively methylated glycopeptides derived from glycophorin A

¹³C-n.m.r. spectral data for ¹³C reductively methylated intact homozygous and heterozygous glycophorins A were compared with the ¹³C-n.m.r. spectral data for the ¹³C reductively methylated homozygous and heterozygous N-terminal glycopeptides derived from the trypsin digest of glycophorin A. The results indicate that pronounced aggregation of this glycoprotein in solution does not affect the structural differences that we have previously observed for glycophorins A^M and A^N at and/or near the N-terminal amino acid. Moreover, the data suggest that two structural states exist for glycophorin A^M.     

RexAB proteins of bacteriophage lambda enhance the effect of photolyase-dimer complexes on lacZ gene expression in Escherichia coli.

Summary Expression of the lacZ gene in Escherichia coli is inactivated by exposure to ultraviolet light (UV). Inactivation is exceptionally effective when cells contain amplified levels of DNA photolyase (which forms complexes with pyrimidine dimers in the absence of light for actual photoreversal) and a prophage. Without amplified photolyase, the prophage or both, inactivation rates are similar and much lower. UV-inactivation of lacZ gene expression in the presence of both amplified photolyase and is even more effective if cI857 is used in place of the wildtype prophage but is wholly unexceptional if the prophage carries defects in the genes rexA or rexB. When Rex AB proteins are provided by expression from a plasmid and the cell also contains amplified photolyase, exceptional inactivation rates again obtain; in fact inactivation is most effective under these conditions. The data are considered to reveal a role for Rex AB proteins, which mediate superinfection exclusion, in the exceptional inactivation of gene expression by photolyase bound to pyrimidine dimers in DNA. Photolyase-dimer complexes may mimic the structure of certain complexes that arise during phage development and thus influence Rex A and/or B proteins, thereby shutting down cell metabolism.     

Freeze fracture immunocytochemistry of light-harvesting pigment complexes in a cryptophyte

Summary Immunocytochemical techniques using colloidal gold as the marker have been used to examine the location of the two light harvesting pigment-protein complexes in cryptophyte chloroplasts. A comparison of post-embedding thin section labelling and freeze fracture labelling has been carried out onRhodomonas salina using polyclonal antibodies to a chlorophylla/c ₂ light-harvesting complex, phycoerythrin and the -subunit of phycoerythrin. The effect of different fixation procedures on the intensity of labelling and ac curacy of antigen location have been examined and the effectiveness of uranyl acetate and tannic acid in improving both the preservation of thylakoid structure and labelling density of phycoerythrin has been demonstrated. Freeze fracture labelling gives better spatial res olution of the different antigens than post-embedding labelling, as well as better definition of thylakoid membranes. It confirms the location of phycoerythrin in the thylakoid lumen and the location of the chlorophylla/c ₂ LHC in both appressed and unappressed thylakoid membranes.Abbreviations PE phycoerythrin - chl chlorophyll - LHC light-har-vesting complex