engleski

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

Application of liposomes in immunology and particularly those relating to vaccines have demonstrated that liposomes may have considerable practical utility as carriers of antigens and adjuvants (1). Our studies concern the immunomodulatory peptidoglycan monomer (PGM, GlcNAc-MurNAc-L-Ala-D-isoGln-mesoDAP(wNH2)-D-Ala-D-Ala), the natural compound originating from the B. divaricatum peptidoglycan, as a potential adjuvant (2). We have been examining its encapsulation into liposomes with the aim to possibly increase and optimize its therapeutic effect. The preliminary results showed that encapsulation of PGM in liposomes improved its adjuvant effect. In order to study the possible interactions between the incorporated glycopeptide 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 to the time-scale of rotational motions of lipids and proteins in biological membrane. The nitroxide is introduced as a reporter group in examined molecule. For this purpose the PGM was spin labelled at w-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 type 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, multilamellar, negatively charged liposomes. ESR spectra demonstrated there are no interactions between spin labelled PGM and lipid bilayer in liposome.

liposomes; peptidoglycan monomer; electron spin resonance (ESR)

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