Thermomyces lanuginosus lipase in the liquid-crystalline phases of aqueous phytantriol: X-ray diffraction and vibrational spectroscopic studies

The influence of Thermomyces lanuginosus lipase (TLL) on the phase behaviour of liquid-crystalline phases of aqueous phytantriol as well as conformational changes of TLL entrapped in the cubic Q(230) phase have been studied by small angle X-ray diffraction (SAXD), FT-Raman, and FT-IR techniques. It was found that the lipidic Q(230) Phase is able to accommodate up to 10 wt.% of TLL, and the temperature of phase transition to the inverted hexagonal phase H-11 increases indicating stabilizing effect of the protein. FT-Raman analysis of Trp amino acid marker band W3 revealed that the average rotation angle around the C-3 - C-beta bond of four TLL residues of TLL in the Q(230) phase increases. Reasoning from available TLL crystallographic data, this result is explained by structural transition of entrapped protein to so-called "open" and more related to the enzymaticallyactive conformation. TLL secondary structure analysis by amide I and amide III vibrational bands showed that content of alpha-helixes does not change, while a part of beta-sheet structures transforms to less ordered elements upon incorporation of protein into the Q230 phase of aqueous phytantriol. (c) 2008 Elsevier B.V. All rights served.