The situation appears similar for C20d in DMPC membranes (Figure ). In this system, the DMPC gel-to-liquid transition should occur at a lower temperature than the crystallization temperature for bulk C20d. Still, at 30 • C, below the crystallization temperature of the alkane and above the DMPC gel-to-liquid transition, the 2 H spectrum of C20d does not show any sign of crystallization, retaining the shape characteristic of anisotropic, liquid hydrocarbon chains. Only a slight broadening is observed which is a natural consequence of the decrease in temperature, since temperature strongly affects alkane order parameters in lipid membranes . Similar to DPPC, both reduced hydration and addition of long-chain n-alkanes will increase the DMPC main transition temperature. However, it is clearly not elevated above the bulk C20d transition temperature in this sample; otherwise the 30 • C spectrum would also show gel-like features. This indicates that the crystallization temperature of C20d is reduced inside the membrane environment, similarly to what happens in mixtures composed of short and long alkanes. This is also observed in the 2 H NMR spectra of 10 vol% C20d in DOPC (Figure ), which still shows anisotropicfluid characteristics at 25 • C. However, the DOPC/C20d sample contains a large amount of bulk n-alkane, making further analysis difficult. We therefore mostly concentrated our efforts on C30d, having a melting temperature well above the main transition temperatures of DMPC and DPPC. In the following sections we demonstrate that C30d can crystallize within a lipid membrane environment.