alignment of lipid nanotubular structures over a wide temperature range a deterioration of signal noise with increase in temperature is also noticeable this can be attributed to the decrease in population difference between the spin states in equilibrium as well as to the decreased probe performance and higher thermal noise originating from the probe itself the downfield resonance shift of up to 8 ppm at higher temperatures could be attributed to a variety of factors such as 1 changes in the chemical shift tensor components and 2 contributions of nonaxial tumbling modes nonaxial tumbling modes could also be responsible for broadening of the carbonyl u03b4 u2248 178 ppm resonance with temperature gramicidin a conducts a wide variety of monovalent cations including protons here we provide an example of an nmr titration experiment in which we monitored the 17 o resonance of d leu 10 carbonyl in aao aligned ga the titration was started at ph 7 0 by exposing the sample to an excess about 20 ml of 10 mm phosphate buffer with successive ph changes to 5 2 2 8 lt 1 1 4 m h 3 po 4 8 4 and 0 12 0 1 m naoh all at t about 43 u00b0 c the entire titration experiment was carried out with the same dmpc ga sample by immersing the stack of aao substrate chips into a desired buffer for 20 min remarkably from ph lt 1 0 to ph 8 4 i e over 7 orders of magnitude in proton concentration no changes in the 17 o peak position were observed fig5 at ph lt 1 0 1 4 m h.