Degradation of Perfluoropolyether Fluids With Metal Ions

1999 ◽  
Vol 121 (2) ◽  
pp. 348-351 ◽  
Author(s):  
Takashi Fukuchi
Keyword(s):  
Metal Ions ◽  
Reaction Mechanisms ◽  
Metal Ion ◽  
Chemical Degradation ◽  
Bivalent Metal ◽  
Ether Cleavage ◽  
Cleavage Process ◽  
Metal Atoms ◽  
Bivalent Metal Ions ◽  
Fomblin Z

Chemical degradation of lubricant fluids of perfluoropolyether (PFPE), such as Fomblin Z-DOL, Fomblin AM-2001, Fomblin Z-25, Demnum SP-3, and Demnum SA, with bivalent metal ions was examined. The respective reaction mechanisms involve an ether cleavage process which is caused by the coordination of metal ions with oxygen atoms in the main chains of the PFPE. Metal ions were evaluated for their ability to degrade the PFPE, and the results demonstrate that the ions ranking in terms of this ability is as follows: Cu2+ > Ni2+ > Co2+ > Fe2+ > Mn2+ > Mg2+. This trend can be explained by the ionization potentials of the metal atoms. For an identical metal ion, the Demnum lubricants showed a greater stability than the Fomblin lubricants.

scholarly journals Activation of membrane-bound high-affinity calcium ion-sensitive adenosine triphosphatase of human erythrocytes by bivalent metal ions

1975 ◽  
Vol 147 (2) ◽  
pp. 359-361 ◽  
Author(s):  
H Pfleger ◽  
H U Wolf
Keyword(s):  
Metal Ions ◽  
Calcium Ion ◽  
Metal Ion ◽  
Adenosine Triphosphatase ◽  
Erythrocyte Membranes ◽  
Bivalent Metal ◽  
High Affinity ◽  
Human Erythrocyte Membranes ◽  
Bivalent Metal Ions ◽  
Membrane Bound

The Ca2+-sensitive ATPase (adenosine triphosphatase) of human erythrocyte membranes is activated, not only by Ca2+ ions, but also by a series of other bivalent metal ions including Sr2+, Ba2+, Mn2+, Ni2+, Co2+, Cd2+, Cu2+, Zn2+ and Pb2+. The degree of activation is dependent on the radius of the ion rather than on its nature, in contrast with the dissociation constant of the enzyme--metal ion complex.

scholarly journals The specificity of yeast low-Km cyclic AMP phosphodiesterase towards free bivalent metal ions and the diastereoisomers of cyclic adenosine phosphorothioate

1985 ◽  
Vol 226 (3) ◽  
pp. 897-900 ◽  
Author(s):  
K Suoranta ◽  
J Londesborough
Keyword(s):  
Cyclic Amp ◽  
Metal Ions ◽  
Metal Ion ◽  
Relative Activity ◽  
Bivalent Metal ◽  
Cyclic Amp Phosphodiesterase ◽  
Bivalent Metal Ions

The relative activity of a zinc-containing cyclic AMP phosphodiesterase towards the (Sp)- compared with the (Rp)-diastereoisomer of cyclic adensine phosphorothioate varied with the identity of the free bivalent metal ion from more than 35 to 0.074 along the series Mg2+ greater than Mn2+ greater than Co2+ greater than Zn2+ greater than Cd2+, showing that this ion, and not the tightly bound zinc, bonds to the phosphorothioate moiety of the substrate.

scholarly journals The kinetics of bivalent metal ion dissociation from myosin subfragments

1986 ◽  
Vol 233 (1) ◽  
pp. 173-177 ◽  
Author(s):  
A J Bennett ◽  
C R Bagshaw
Keyword(s):  
Metal Ions ◽  
Rate Constant ◽  
Metal Ion ◽  
Specific Site ◽  
Ph Change ◽  
Bivalent Metal ◽  
Skeletal Muscle Myosin ◽  
Adductor Muscles ◽  
Bivalent Metal Ions ◽  
Muscle Myosin

Bivalent metal ions have multiple roles in subunit association and ATPase regulation in scallop adductor-muscle myosin. To help elucidate these functions, the rates of Ca2+ and Mg2+ dissociation from the non-specific high-affinity sites on the regulatory light chains were measured and compared with those of rabbit skeletal-muscle myosin subfragments. Ca2+ dissociation had a rate constant of about 0.7 s-1 in both species, as measured by the time course of the pH change on EDTA addition. Mg2+ dissociation had a rate constant of 0.05 s-1, as monitored by its displacement with the paramagnetic Mn2+ ion. It is concluded that the exchange between Ca2+ and Mg2+ at the non-specific site, on excitation of both skeletal and adductor muscles, is too slow to contribute to the activation itself. The release of bivalent metal ions from the non-specific site is, however, the first step in release of the scallop regulatory light chain (Bennett & Bagshaw (1986) Biochem. J. 233, 179-186). In scallop myosin additional specific sites are present, which can bind Ca2+ rapidly, to effect activation of the ATPase. In the course of this work, Ca2+ dissociation from EGTA was studied as a model system. This gave rates of 1 s-1 and 0.3 s-1 at pH 7.0 and pH 8.0 respectively.

scholarly journals Metal-ion-promoted binding of triazine dyes to proteins. The interaction of Cibacron Blue F3G-A with yeast hexokinase

1982 ◽  
Vol 205 (2) ◽  
pp. 453-456 ◽  
Author(s):  
P Hughes ◽  
R F Sherwood ◽  
C R Lowe
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Difference Spectroscopy ◽  
Bivalent Metal ◽  
Cibacron Blue ◽  
Transition Series ◽  
Bivalent Metal Ions ◽  
A Site ◽  
Active Site Region ◽  
Yeast Hexokinase

Bivalent metal ions, particularly Zn2+ and other members of the first-row transition series, promote irreversible inactivation of yeast hexokinase by Cibacron Blue F3G-A at a site competitive with both ATP and D-glucose. Difference spectroscopy indicates that the protein-dye dissociation constant is decreased from 250 micrometers in the absence of metal ions to less than 100 micrometers in the presence of appropriate concentrations of metal ions, with specificity displayed in the sequence of Zn2+ greater than Cu2+ greater than Ni2+ greater than Mn2+. Quantitative inactivation of yeast hexokinase leads to the incorporation of approx. 1 mol of Cibacron Blue F3G-A/mol of subunit of mol. wt. 51 000 in both the presence and the absence of metal ion. These results suggest the formation of a highly specific ternary complex involving enzyme, dye and metal ion at the active-site region of the enzyme, and correlate well with the known effects of metal ions in promoting the binding of hexokinase to immobilized Cibacron Blue F3G-A.

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