Stereochemical requirements for intercalation of platinum complexes into double-stranded DNA's

The complexes 1,10-phenanthrolineethylenediamineplatinum(II) and 2,2'-bipyridineethylenediamineplatinum(II) have a planar, aromatic ligand system that facilitates intercalation, as shown by their ability to unwind closed circular duplex DNA. Nonbonded steric interactions can rotate the pryidine ligands out of the coordination plane in bis(pyridine)ethylenediamineplatinum(II), thus preventing intercalation. Fiber x-ray diffraction patterns of the two metallointeracalators indicate that the binding is governed by the neighbor exclusion principle.     

Bronchoalveolar lavage fluid--a new material in pulmonology

Bronchoalveolar lavage is a new method of evaluating the inflammatory and immune processes of the human lung. Sufficient material are obtained from normal individuals to allow characterization of cells and proteins. Comparisons with lung biopsies show that these constituents are representative for the composition of the alveolar structures. With the use of lavage new insights will be obtained into the pathogenesis of interstitial and other lung disorders.     

The effects of zinc and copper salts on Cyprinus carpio and Ctenopharyngodon idellus

The effects of zinc and copper salts on the survival of the two species of freshwater fish, common carp, Cyprinus carpio, and grass carp, Ctenopharyngodon idellus, were investigated. It was discovered that the levels of tolerance to the concentration of the metals were species-specific. Cyprinus carpio was found to be more susceptible to copper, whereas Ctenopharyngodon idellus was more susceptible to zinc. In general, copper was more toxic than zinc, as revealed by the survival times. The body and the gills of dead fish seemed to be covered by a veil-like film which looked like coagulated mucus and which was formed by the heavy-metal ions reacting with some constituents of the mucus and which was formed by the heavy-metal ions reacting with some constituents of the mucus secreted by the gill. The histopathological assessment of the gill and liver of Cyprinus carpio was also carried out. Particles were observed around the gills of the dead fish treated with zinc and copper salts, although no other major changes were found in the gill. Several histopathological changes were observed in the livers, including the presence of particles. The symptoms of the liver suggested that the internal injury was also an important feature of the intoxicants.     

Comparison of the esterase and human plasminogen activator activities of various activated forms of human plasminogen and their equimolar streptokinase complexes

A comparison was made of the esterase and activator activities of the various activated forms of human plasminogen and their streptokinase complexes with Nalpha-Cbz-L-lysine-p-nitrophenyl ester as the substrate. The steady state kinetic properties of Glu- and Lys-plasmins, and Glu- and Lys-plasminogen-streptokinase complexes were identical, while the Lys-plasmin-streptokinase complex showed a 2-fold increase in Km with the same kcat and a 3-fold increase in Ki for the competitive inhibitor leupeptin. Lys-plasminogen (zymogen with an active site) was prepared which incorporated 0.7 mol of [3H]idisopropyl phosphorofluoridate and 0.43 mol of p-nitrophenyl-p'-guanidinobenzoate/mol of protein. The Km for Lys-plasminogen was 3-fold higher than that of Lys-plasmin, and its maximum velocity 10-fold lower. The steady state kinetic parameters of a plasmin-derived light (B) chain (CmCys)3, and a derived equimolar light (B) chain-streptokinase complex (CmCys)3, isolated from human plasmin and equimolar plasmin-streptokinase, or plasminogen-streptokinase, complexes, respectively, were determined. When the light (B) chain-streptokinase complex is isolated from its parent complexes, there is a complete retention of the original parent's esterase activities, with respect to Km and kcat, and interaction with the competitive inhibitors benzamidine and leupeptin. The plasmin-derived light (B) chain does not retain its parent esterase activities. This chain has very similar kinetic properties to Lys-plasminogen except that streptokinase, in an equal molar amount, does not impart full esterase activity to the light (B) chain whereas the zymogen can be completely activated by streptokinase. The kcat of the plasmin-derived light (B) chain, and its streptokinase complex can be enhanced by 50 and 30%, respectively, in the presence of 10(-4) M leupeptin, a competitive inhibitor of plasmin, attesting to the increased structural flexibility within the active site of this enzyme species. Urokinase hydrolyzes Nalpha-Cbz-L-lysine p-nitrophenyl ester efficiently with a kcat/Km of one-third that of plasmin. The human plasminogen activator activities of various activated forms of human plasminogen and their equimolar streptokinase complexes were compared in a kinetic assay. The Lys-plasmin-streptokinase complex, and streptokinase were the least active of the activator species and were approximately equal in their activator activities. Glu- and Lys-plasminogen-streptokinase complexes had approximately 1.5 times the activity of streptokinase, whereas the equimolar light (B) chain-streptokinase complexes had approximately 2- to 3-times the activator activity of streptokinase. Since the esterase activity remained unchanged, this indicates a greater degree of specificity in the active site of the equimolar light (B) chain-streptokinase activator complex. Urokinase proved to be a poor activator species...     

A New Study on the Doped Mott–Hubbard Insulator

By introducing a rotationally invariant Stratonovich–Hubbard (S-H) field we studied the doped Mott insulator phase of the two-dimension Hubbard model for U/t4–8. The static spin is decoupled by the S–H field and the static charge interaction is then treated by Hartree–Fock approximation. We sample random spin configurations by Monte Carlo simulation with the Metropolis updating algorithm. The Mott–Hubbard gap and static susceptibilities are studied near the half-filling at low temperature.