engleski

SYNTHESIS OF SPIN LABELLED PEPTIDOGLYCAN MONOMER AND ESR STUDY OF INTERACTIONS WITH LIPOSOMES

Application of liposomes in immunology and particulary those relating to vaccines have demonstrated that liposomes may have considerable practical utility as carriers of antigens and adjuvants. Our studies concern two groups of immunomodulators as potential adjuvants, peptidoglycan monomer (PGM, GlcNAc-MurNAc-L-Ala-D-isoGln-mesoDAP(ω NH2)-D-Ala-D-Ala) the natural compound originating from B. Divaricatum peptydoglycan and synthetic adamantyltripeptides D- and L-(adamant-2-yl)-Gly-L-Ala-D-isoGln. We have been examining their encapsulation into liposomes with the aim to increase and optimize their therapeutic effect. The preliminary results showed that encapsulation of PGM and AdTP2 in liposomes improved their adjuvant effect. In order to study the possible interactions between the incorporated peptides and lipid bilayers the electron spin resonance (ESR) was used. ESR is a spin labeling technique, which is based on dynamic sensitivity of the nitroxide label on the time-scale of rotational motions of lipids and proteins in biological membrane. The nitroxide is introduced as a reporter group in examined molecules. For this purpose the PGM was spin labelled at ω -amino group of the meso-diaminopimelic acid (SL-PGM). It was prepared by condensation of unprotected peptidoglycan monomer and symmetrical anhydride of 3-carboxy-proxyl molecules. Two types of studies of the SL-PGM were carried out: a) ESR study of spin labelled PGM at different pH and different temperature. The results showed that SL-PGM undergoes a conformational changes at about 300 K. b) The study of possible interactions of SL-PGM and lipid membranes. SL-PGM was incorporated into large, multilamelar, negativly charged liposomes. ESR spectra demonstrated there are no interactions between spin labelled PGM and lipid bilayer in liposome.

PGM; liposomes; adamantyltripeptides; ESR

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