Abstract:Ab initio calculations on O₃, FeO₂, Fe(Ⅰ)O₂, Fe(Ⅱ)O₂, CoO₂ and Co(Ⅱ)O₂ were carried out by the spin unrestricted Hartree-Fock method. The results show that the Mulliken population of Fe^(Ⅱ), central Oc and terminal Or are 24.18, 8.19 and 7.64 respectively for π-system in oxyhemoglobin. This is contrary to the suggestion by Weiss that the Fe-O₂ bond is similar to Fe³⁺O₂^-. The result appears to fit the experimental data very well and provides good mechanistic evidence for explaining the oxygenation-deoxygenation of oxyhemoglobin in the life of living organisms.

Abstract:A simple radioassay of HDL-binding sites on purified rat liver plasma membranes with polyethyleneglycol (PEG) precipitation separation of B/F was developed. ¹²⁵I-labeled apoE-deficient human HDL₃ was prepared as the ligand. 12.5％ of the final PEG concentration could effeciently sediment the ¹²⁵I-labeled HDL₃-membrane complex, and more than 94％ of the total binding was specific (non-specific binding was determined at the presence of 25fold excess HDL₃). A saturable and high affinity HDL-binding site on liver membranes with kd 14.5+0.86μg/ml (16.6×10^-8mol/L) and B_max 15.6+6.8μgg/mg membrane protein was found. The B_max of this HDL-binding appeared to increase as the reactiontemperature rose. The binding activity of this HDL receptor was not inhibited by 0—30 m mol/L EDTA and not activated by 0—5.0 mmol/L Ca²⁺, as well as insensitive to trypsin. Human HDL₃ and rat HDL, but not human VLDL, LDL and albumin, could effectively inhibit the ¹²⁵I-labeled HDL₃ binding to the liver membranes. The ¹²⁵I-labeled HDL₃ binding activity (μg/mg membrane protein) increased with the increasing of the liver membrane purity. These results suggest that there was a saturable and highly specific HDL-receptor on liver plasma membranes, and its biologic properties are different from LDL-and apoE-receptors.

Abstract:The UV, FTIR and fluorescence spectra differences of glucoamylase in the presence and absence of organic solvent e. g. acetone, methanol, propanol, dioxane, ethylane glycol etc. show that the aromatic amino acid (Trp, Tyr, Phe) are exposed after solvent-perturbation and then the conformational change of glucoamylase may be occurred with fast inactivation of the enzyme.