Circular dichroism study of membrane dynamics. Effects of carboxymethyl-chitin.
The circular dichroism (CD) active phospholipid bis(4'-n-octanoxyazobenzene-4-carboxyl)-L-alpha-phosphatidylcholin e (CDPC) was used to study the effects of carboxymethyl-chitin (CM-chitin) on the membrane dynamics. For this purpose, CD and electronic spectra were observed for a mixture of CM-chitin and liposomes composed of CDPC and egg lecithin (EPC) (50% CDPC-EPC-liposomes), and for a mixture of CM-chitin, 50% CDPC-EPC-liposomes, and EPC-liposomes. CM-chitin at concentrations higher than ca. 10(-5) M induced the increase of absorbance at 600 nm synchronized with the dilution of CDPC in 50% CDPC-EPC-liposomes by EPC matrix, indicating that CM-chitin induces the fusion among a few liposomes and/or the lipid transfer through the transient liposome fusion. Temperature dependent CD spectra of a mixture of the 50% CDCP-EPC-liposomes and CM-chitin suggested that even high concentration of CM-chitin has no significant perturbation of the lipid organization in the membranes. The effects of CM-chitin on the leakage of [3H]sucrose from the EPC-liposomes were also studied. By the presence of 5 X 10(-6) M CM-chitin, the half-life for leakage of [3H]sucrose in plasma was increased by 4 times. This effect of CM-chitin was reduced by chitinase, while no effect was observed with lysozyme, suggesting that CM-chitin molecules are adsorbed on the liposome surface and stabilize the liposomes against the plasma proteins.
Nishiya
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T
Artificial Cells & Organs Research Centre, McGill University, Montreal PQ, Canada.
Ahmed
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S
D000818:Animals; D001798:Blood Proteins / Q000494:pharmacology; D003386:Brachyura; D002645:Chickens; D002686:Chitin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002942:Circular Dichroism; D004305:Dose-Response Relationship, Drug; D008081:Liposomes / Q000378:metabolism*; D008561:Membrane Fusion / Q000187:drug effects; D008563:Membrane Lipids / Q000378:metabolism; D008567:Membranes, Artificial; D010713:Phosphatidylcholines / Q000378:metabolism; D013053:Spectrophotometry; D013395:Sucrose / Q000378:metabolism; D013696:Temperature; D014316:Tritium
D001798:Blood Proteins; D008081:Liposomes; D008563:Membrane Lipids; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D014316:Tritium; C064527:bis(4'-n-octanoxyazobenzene-4-carboxyl)phosphatidylcholine; D002686:Chitin; C044872:O-(carboxymethyl)chitin; D013395:Sucrose