Raman spectroscopy of Na/K-ATPase with special focus on low-frequency vibrations

Na/K-ATPase powder samples were analyzed, both in lyophilized and rehydrated states, by a latest generation Raman spectrometer mounting Ultra Low Frequency (ULF) filters that allowed investigating even the lower frequencies (<500 cm−1 = 15 THz). While several known peaks, which are assigned in the literature to molecular vibrations of chemical groups or amino acids, were recognised in the 500-3500 cm−1 range, the analysis of the sub-500 cm−1 region, performed with two different resolutions, allowed finding unassigned peaks. Such low-frequency peaks are apparently unknown in the current literature for Na/K-ATPase. Recent studies suggested that low-frequency collective vibrations that involve large protein portions are strictly correlated to protein functions. Thus, the present results could be of interest with regard to possible connections between low-frequency mechanical vibrations and the operating mechanism of the sodium-potassium pump.