Hi,

Adolfo López

Note: Tm is "melting temperature"

Tc is "Phase Transition Temperature".

In general, Tc is lowered by decreased length of the fatty acyls of phospholipid molecules, by unsaturation of the acyl chains, as well as presence of branched chains and bulky head groups (e.g. cyclopropane rings).

See attached graph.

Source:

Danaei, M., Kalantari, M., Raji, M., Fekri, H.S., Saber, R., Asnani, G.P., Mortazavi, S.M., Mozafari, M.R., Rasti, B. and Taheriazam, A., 2018. Probing nanoliposomes using single particle analytical techniques: effect of excipients, solvents, phase transition and zeta potential. Heliyon, 4(12), p.e01088.

Thank you so much M.R. Mozafari

Dear Adolfo López ,

In addition to what is already said by M. R. Mozafari the basics comes down to: saturated acyl chains are lying closer to one another and have more surface area bound to each other and therefore more van der Waals binding. Unsaturation causes the acyl chains to be more ‘kinked’ and the loss of surface area bound causing lowering of the van der Waals binding and consequently a lower melting point. See also depicted figure.

Best regards.