The temperature dependences of protein denaturing, H/D exchange and lipid fatty acyl chain disorder in different biological membranes. Comparison of H/D exchange rates (open circle) (panels A, C, and E), and the characteristic frequencies (open triangle) (panels B, D, and F) of the disappearing amide II band with the lipid disorder (open square) (νsymCH2) and with protein heat-denaturing (black circle) (prot. den.) in tobacco (panels A, B), in Synechococcus (panels C, D) thylakoids, and in mitochondrial membranes (panels E, F). Note that the scale of the disappearing amide II intensity changes is negative, thus lower values mean higher exchange rates. Vertical lines indicate the temperatures of the maximal H/D exchange rates; these temperatures do not correlate with the level of the corresponding lipid disorder (νsymCH2 points) indicated with horizontal lines in panels A, C and E. For the meaning of ISO and ΔT, see Methods – H/D exchange protocol.