Here we report a successful use of a recently developed isoprenoid-chained lipid family for in meso crystallization of membrane proteins. The isoprenoid-chained lipid 1-O-(3,7,11,15-tetramethylhexadecyl)-beta-D-xyloside (beta-XylOC(16+4)) used as a host lipid for in meso crystallization provided high quality bacteriorhodopsin (bR) crystals (P6(3) space group) diffracting to high resolution and characterized by low twinning ratio. beta-XylOC(16+4) has an isoprenoid chain with methyl branches at each 4th position and a xylose group in the water-soluble part. These peculiarities make the lipid clearly distinguishable in the bR crystalline lattice and provides a unique opportunity to study the role of the host lipid in the in meso crystallization. We conclude that beta-XylOC(16+4) may have a general application for in meso crystallization for a wide range of membrane proteins. The cubic phase of beta-XylOC(16+4) is present over a wide range of temperatures and is stable at low temperature (down to about 8 degrees C). This opens up the possibility of using temperature as a tool for the optimization of in meso crystallization with additional advantages for the crystallization of membrane proteins at lower temperatures where the proteins of interest may be more stable. (C) 2010 Elsevier B.V. All rights reserved.