H-1 NMR relaxation measurements in highly concentrated water protein solutions

Measurements performed on biological systems, such as parts of plants, seed s and animals reveal non-exponential decay of the spin-spin relaxation func tion. Such behaviour has also been observed in the eye lens, which is a rel ative simple system mainly built from water, 65% of total weight, and 35% o rganic material, mainly structural proteins. To understand this phenomena o ne has to find a simplified system which will allow measurement and descrip tion of magnetic relaxation processes and compare them to the biological sy stem. One such system can be water solution of bovine serum albumin (BSA) w ith concentration higher than 30%. It was found that nuclear magnetic relax ation time, T-2, in aqueous solution of albumin for low concentration depen ds mainly on fast proton exchange between free water and water adsorbed on the protein surface. For higher concentration of BSA (30%-55%) a second pro ton exchange process starts to play a role and in consequence the spin-spin relaxation function is a sum of two exponential functions. Copyright (C) 1 999 John Wiley & Sons, Ltd.