LASER SEEDING FOR BIOMOLECULAR CRYSTALLIZATION

Crystal seeding, which permits the decoupling of crystal nucleation an d growth, is a potentially powerful tool for biomolecular crystallizat ion. However, its usefulness is severely limited by the inability of c urrent techniques to manipulate single seeds and it is often considere d as a last resort in protein crystal growth trials. Remarkably, curre nt practice relies on the cumbersome technique of entraining seed crys tals on animal whiskers. Seeding by whisker entrainment is not reprodu cible and does not allow the observation, selection or individual tran sfer of seeds. Here, we present a novel approach in which optical forc es generated by a focused laser beam are used to select and transfer s ingle microscopic seed crystals in a growth solution. The technique pe rmits the non-mechanical, in situ manipulation of individual seed crys tals as small as one micron. The seed transfer is simple and efficient , and can be completed in a few minutes. To demonstrate the procedure we have successfully seeded and grown crystals of tomato bushy stunt v irus (TBSV), Applications to other situations which require the select ion and manipulation of delicate microcrystals are discussed briefly. (C) 1998 Elsevier Science B.V. All rights reserved.