An investigation of human oxyhemoglobin beta tetramer dissociation using haptoglobin binding

Haptoglobin was used as a macromolecular probe to investigate the formation of human oxyhemoglobin beta chain dimers from tetramers in 0.1 M potassium phosphate buffer, 20 degrees C at pH 7 and pH 8. Monitoring of spectral changes upon mixing haptoglobin with beta heme chains (2.5 and 5 micromolar) revealed an overall decrease in absorbance accompanied by a shift of the Soret spectral peak from 415 to 417 nm. The magnitude of the absorbance decrease was proportional to the beta concentration; the time courses consistently yielded greater color at pH 8 than at pH 7. At pH 8, two exponential phases of 0.47 min-1 and 0.084 min-1 were seen whose rates remained invariant with concentration. In contrast, only one exponential process was evident at pH 7, yielding a first order rate constant of 0.21 min-1. We have spectrophotometrically followed the beta chain tetramer to dimer dissociation reaction, thus providing information about the contribution of this step to hemoglobin assembly.     

New synthetic approach to nucleoside phosphorofluoridates and fluoridites. Novel type of phosphitylating reagents containing 4-nitrophenoxy group.

New DNA analogues which have -OP(O)F-O internucleotide linkage are prepared by two methods. One route is based on transformation of a deoxynucleoside phosphoroimidazolidate by benzoylfluoride into the corresponding phosphorofluoridate. Alternative route begins with condensing of a new type of phosphoroamidites containing 4-nitrophenoxy group: N,N,N',-tetraisopropyl-O-4-nitrophenylphosphorodiamidite 9 to yield the dideoxynucleoside-4-nitrophenylphosphites which are readily converted into the corresponding dideoxynucleoside phosphorofluoridates and their sulfur analogues. Second part of this paper illustrates application of the N,N-diisopropyl-O-methyl-O-4-nitrophenylphosphoroamidite 12 and N,N-diisopropyl-O-4-nitrophenyl-P-methylphosphonoamidite 16 in efficient synthesis of dideoxynucleotides and their thio- and selenoanalogues.     

Cu,Zn superoxide dismutase from chicken erythrocytes.

1. Copper, zinc superoxide dismutase (Cu,Zn SOD) has been purified to homogeneity from chicken erythrocytes by anion-exchange, immobilized metal affinity and size exclusion chromatography. 2. Molecular properties (amino acid composition, molecular mass, subunit composition and spec. act.) of the chicken enzyme are similar to those of a bovine erythrocyte Cu,Zn SOD. 3. The chicken and bovine enzymes are immunologically similar since antisera raised against each enzyme are cross-reactive.