PubMed · 6791343
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J E Dees, E E Anderson. 1981. Coagulum pyelolithotomy.. https://pubmed.ncbi.nlm.nih.gov/6791343/
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Surfactant protein A (SP-A) is the major protein of pulmonary surfactant. This protein is implicated in regulating surfactant secretion, alveolar processing, recycling, and in non-serum-induced immune response. An increasing body of work indicates the importance of cations, particularly calcium, on SP-A function. However, little information exists on the effects of cations on SP-A quaternary structure. Here, the quaternary organisation of bovine surfactant protein A in the presence of cations has been quantitatively and systematically studied by transmission electron microscopy. The conformation of SP-A is altered by the presence of cations, especially calcium, then sodium, and to a small extent, magnesium. There is a transition concentration, unique for each cation, at which a conformational switch occurs. These transition concentrations are: 5 mM for CaCl2, 100 mM for NaCl and 1 mM for MgCl2. Below these concentrations, SP-A exists primarily in an opened form with a large head diameter of 20 nm; above it, SP-A is mostly in a closed form due to a compaction of the headgroups resulting in a head diameter of 11 nm. There is a corresponding increase in particle length from 17 nm for opened SP-A to 20 nm for closed SP-A. The fact that the transition concentrations are within physiological range suggests that cation-mediated conformational changes of SP-A could be operative in vivo.
The binding of warfarin to 10 mumol/L human serum albumin (HSA) was studied in vitro by equilibrium dialysis in presence of two different calcium concentrations. At 2.3 and 23 mmol/L calcium concentrations, the percentage binding decreased. The number of saturable sites of warfarin-HSA at these two calcium concentrations were 1.02 and 1.23 respectively; the number of saturables sites observed with warfarin alone was higher (n1 = 1.32). The association constant for saturable sites (K1 = 0.187 mumol-1) and the affinity coefficient for the nonsaturable sites (n2K2 = 0.0955) remained unchanged. The binding to HSA was 98 per cent at therapeutic levels, that is a physiological concentrations of protein and therapeutic levels of warfarin, in the presence of several concentrations of calcium (2.5; 5; 25; 50 and 100 mmol/L) or magnesium (1;2;10;50 and 100 mmol/L) as chloride compounds, the free fraction of warfarin remained constant until calcium or magnesium reached concentrations of 50 mmol/L, in which cases the percentage binding fell to 92 per cent. In conclusion a displacement of bound warfarin can be expected only if the plasma concentrations of calcium or magnesium and as well chloride concentration are raised by much.
In this work, affinity chromatography was used to remove endotoxin from human hemoglobin preparations with a Sterogene Acticlean Etox column. The effects of solution conditions on endotoxin removal efficiency and protein recovery have been investigated. It has been found that cations Na(+) or Ca(2+) reduced endotoxin removal efficiency from 73% (sample prepared with endotoxin-free water) to 31% (sample prepared with 0.15 M NaCl, ionic strength, I = 0.15 M), and from 73% sample prepared with endotoxin-free water) to 9% (sample prepared with 0.05 M CaCl2, ionic strength, I = 0.15 M). It has also been found that the protein recovery was increased from 90% to 99%, respectively.