Complex of praseodymium with lipid as a NMR temperature sensor and probe of liposome states
The goal of the research was to show the limits within which Pr3+ can be used as a linear response probe. The temperature-dependence of lanthanide-induced chemical shifts (LISs) was studied using examples of different phospholipids (POPC, DPPC and the mixture DPPC + DOPC) by means of NMR spectroscopy. It was demonstrated that this dependence is strongly influenced by the lipid composition, and features of the temperature-dependence indicate the features of the thermal changes of the structure of liposomes. Features of the temperature-dependence were detected for DPPC and the mixture of DPPC + DOPC. The width of these features corresponds to the width of the phase transitions. The analysis of paramagnetic properties such as the temperature sensitivity of LIS indicates the prospect of using kinetically unstable lanthanide complexes as shifting temperature-sensitive probes for determining local temperature and prospective diagnosis of diseases using MRI technology. In the long term, nonlinear changes in the LIS in the inflection region can be useful for practical use (to obtain a very sensitive temperature response, similar to classical titration, when a sharp change close to equivalence makes the measurement sensitive).