title: Improved success of sparse matrix protein crystallization screening with heterogeneous nucleating agents.
abstract: BACKGROUND
  Crystallization is a major bottleneck in the process of macromolecular structure determination by X-ray crystallography. Successful crystallization requires the formation of nuclei and their subsequent growth to crystals of suitable size. Crystal growth generally occurs spontaneously in a supersaturated solution as a result of homogenous nucleation. However, in a typical sparse matrix screening experiment, precipitant and protein concentration are not sampled extensively, and supersaturation conditions suitable for nucleation are often missed.
  
  
  RESULTS
  We tested the effect of nine potential heterogenous nucleating agents on crystallization of ten test proteins in a sparse matrix screen. Several nucleating agents induced crystal formation under conditions where no crystallization occurred in the absence of the nucleating agent. Four nucleating agents: dried seaweed; horse hair; cellulose and hydroxyapatite, had a considerable overall positive effect on crystallization success. This effect was further enhanced when these nucleating agents were used in combination with each other.
  
  
  CONCLUSIONS
  Our results suggest that the addition of heterogeneous nucleating agents increases the chances of crystal formation when using sparse matrix screens.
authors.affiliation: School of Molecular and Microbial Sciences, University of Queensland, St. Lucia, Brisbane, Queensland, Australia.
authors.forename: Anil S
authors.initials: AS
authors.lastname: Thakur
authors.forename: Gautier
authors.initials: G
authors.lastname: Robin
authors.forename: Gregor
authors.initials: G
authors.lastname: Guncar
authors.forename: Neil F W
authors.initials: NF
authors.lastname: Saunders
authors.forename: Janet
authors.initials: J
authors.lastname: Newman
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Martin
authors.forename: Bostjan
authors.initials: B
authors.lastname: Kobe
mesh_terms: D001671:Biochemistry / Q000379:methods; D002482:Cellulose / Q000737:chemistry; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods*; D003911:Dextrans / Q000737:chemistry; D004058:Diffusion; D017886:Durapatite / Q000737:chemistry; D008954:Models, Biological; D015394:Molecular Structure; D011489:Protein Denaturation; D011506:Proteins / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D012995:Solubility; D014025:Titanium / Q000737:chemistry
chemical_list: D003911:Dextrans; D011506:Proteins; C009495:titanium dioxide; D012822:Silicon Dioxide; D002482:Cellulose; C025614:sephadex; D017886:Durapatite; D014025:Titanium