Affinity of young and old human erythrocytes for alkyl-sepharose 6MB gels

Liposome chromatography: liposomes immobilized in gel beads as a stationary phase for aqueous column chromatography

Liposomes have been used as a stationary phase for column chromatography with an aqueous mobile phase. They were immobilized in the pores of carrier gel beads by two methods: (A) hydrophobic ligands were coupled to the matrix of gel beads, which then were packed into a column and liposomes were applied and became associated with the ligands by hydrophobic interaction; and (B) phospholipids and detergent were dialysed in the presence of gel beads; many of the liposomes that formed in the pores of the beads were sterically immobilized by the gel matrix. Proteoliposomes containing red cell glucose transport protein in the lipid bilayers were immobilized in a column by method A. This column retained D-glucose longer than L-glucose. In contrast to L-glucose, D-glucose was transported into and out of the immobilized liposomes, causing an increased retention. Liposomes with (stearylamine)+ or (phosphatidylserine)- in their lipid bilayers were immobilized by method B and the gel beads were packed into a column. A protein of opposite charge was applied in excess. Under suitable conditions, the protein molecules became close-packed on the liposome surfaces. Ion-exchange chromatographic experiments with proteins showed that these sterically immobilized liposomes were also stable enough to be used as a stationary phase. The loss of lipids was 5-23% in the first run at high protein load and with sodium chloride gradient elution but was lower in subsequent runs. It is proposed that water-soluble molecules can be separated and their interactions with liposome surfaces studied by chromatography on immobilized liposomes in detergent-free aqueous solution. Membrane proteins can be inserted and ligands can be anchored in the lipid bilayers for chromatographic purposes.

Binding of lectins to "young" and "old" human erythrocytes

"Old" human erythrocytes showed a 21.2% decrease in cell surface area and a 2% decrease in the number of WGA receptor sites, but a 27% increase in the distribution density of the WGA (lectin) receptor site, when compared with "young" human erythrocytes. For a list of lectin abbreviations, see Materials and methods). Both "young" and "old" erythrocytes exhibited very weak binding activity for 125I-labeled PNA, but there was no difference in binding activity for PNA between "young" erythrocytes and "old" ones. Compared with "young" erythrocytes, decreases in the number and distribution density of receptor sites for five lectins including LPA, Con A, RCA-II, SBA and BPA on the cell surface were observed in aged erythrocytes. "Old" erythrocytes also showed a decrease in the number of PHA-E receptor sites, while the distribution density of the same receptor site remained unchanged. In view of these and other observations, it is thought that human erythrocyte aging is accompanied by elimination of some glycoconjugates which have affinity for six lectins, LPA, Con A, RCA-II, PHA-E, SBA and BPA, whereas no WGA receptor-containing glycoconjugates are released from erythrocyte membranes. Elimination of the glycoconjugates results in shrinkage of erythrocytes to reduce their cell surface areas.

Comparative study on the main membrane-surface sialoglycopeptides released from young and old human erythrocytes with trypsin

1. The amount of sialoglycopeptide (SGP) mixture released from young (Y) erythrocytes by trypsin treatment was significantly larger than that from old (O) ones. 2. The two main membrane-surface sialoglycopeptides (Y-SGP and O-SGP) were isolated in yields of about 45% and 42% from the mixtures by a combination of Sephadex G-50 superfine gel filtration with DEAE-cellulose chromatography, respectively. Molecular weights of 12,000 and 12,100, respectively, were found for the Y-SGP and the O-SGP. 3. The Y-SGP showed a greater proportion of sialic acid than the O-SGP. The contents of galactose, N-acetylglucosamine and N-acetylgalactosamine of the Y-SGP were significantly lower than those of the O-SGP. 4. Both the SGPs exhibited the same reactivities against the MN reagents, but the reactivities against the lectins of Limulus polyphemus and Phaseolus vulgaris (E) were stronger in the Y-SGP than in the O-SGP. Neither the Y-SGP nor the O-SGP showed the reactivity to Arachis hypogaea (anti-T) lectin.

Number and distribution density of ABH and MN antigen sites on young and old human erythrocyte surfaces

There were no differences in the number of A and M antigen sites between young and old human erythrocyte surfaces. No essential differences in the number of A1, N and Vicia graminea N antigen sites could be observed between young and old erythrocytes. The number of B and H antigen sites on cell surface was significantly higher in young erythrocytes than in old ones. The distribution density of A and M antigen sites on young erythrocyte was remarkably higher than that on old ones. Compared with young erythrocytes, significant increases in the distribution density of A1, B, H, N and Vicia graminea N antigen sites were observed in aged erythrocytes. It is suggested from these and other observations that human erythrocyte aging is accompanied by elimination of a small amount of B and H antigens from cell membranes, while A, A1, M, N and Vicia graminea N antigens are not released from cell membranes during in vivo aging.