Tunable alignment of macromolecules by filamentous phage yields dipolar coupling interactions

Dipolar coupling interactions represent an extremely valuable source of lon g-range distance and angle information that was previously not available fo r solution structure determinations of macromolecules. This is because obse rvation of these dipolar coupling data requires creating an anisotropic env ironment for the macromolecule. Here we introduce a new method for generati ng tunable degrees of alignment of macromolecules by addition of magnetical ly aligned Pf1 filamentous bacteriophage as a cosolute. This phage-induced alignment technique has been used to study H-1-H-1, H-1-C-13, and H-1-N-15 dipolar coupling interactions in a DNA duplex, an RNA hairpin and several p roteins including thioredoxin and apo-calmodulin, The phage allow alignment of macromolecules over a wide range of temperature and solution conditions and thus represent a stable versatile method for generating partially alig ned macromolecules in solution.