title: The magic triangle goes MAD: experimental phasing with a bromine derivative.
abstract: Experimental phasing is an essential technique for the solution of macromolecular structures. Since many heavy-atom ion soaks suffer from nonspecific binding, a novel class of compounds has been developed that combines heavy atoms with functional groups for binding to proteins. The phasing tool 5-amino-2,4,6-tribromoisophthalic acid (B3C) contains three functional groups (two carboxylate groups and one amino group) that interact with proteins via hydrogen bonds. Three Br atoms suitable for anomalous dispersion phasing are arranged in an equilateral triangle and are thus readily identified in the heavy-atom substructure. B3C was incorporated into proteinase K and a multiwavelength anomalous dispersion (MAD) experiment at the Br K edge was successfully carried out. Radiation damage to the bromine-carbon bond was investigated. A comparison with the phasing tool I3C that contains three I atoms for single-wavelength anomalous dispersion (SAD) phasing was also carried out.
authors.affiliation: Department of Structural Chemistry, Georg-August-Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany. tbeck@shelx.uni-ac.gwdg.de
authors.forename: Tobias
authors.initials: T
authors.lastname: Beck
authors.forename: Tim
authors.initials: T
authors.lastname: Gruene
authors.forename: George M
authors.initials: GM
authors.lastname: Sheldrick
mesh_terms: D018360:Crystallography, X-Ray / Q000379:methods*; D019286:Endopeptidase K / Q000032:analysis / Q000737:chemistry; D006860:Hydrogen Bonding; D008958:Models, Molecular; D010795:Phthalic Acids / Q000737:chemistry*; D017434:Protein Structure, Tertiary
chemical_list: C542184:5-amino-2,4,6-tribromoisophthalic acid; D010795:Phthalic Acids; D019286:Endopeptidase K
references.citation: Structure. 2003 Feb;11(2):217-24
references.pmid: 12575941
references.citation: Acta Crystallogr D Biol Crystallogr. 2008 Nov;64(Pt 11):1172-8
references.pmid: 19020356
references.citation: Acta Crystallogr D Biol Crystallogr. 2008 Apr;64(Pt 4):354-67
references.pmid: 18391402
references.citation: Acta Crystallogr Sect F Struct Biol Cryst Commun. 2009 Oct 1;65(Pt 10):1068-70
references.pmid: 19851024
references.citation: J Synchrotron Radiat. 1996 Jan 1;3(Pt 1):24-34
references.pmid: 16702655
references.citation: Acta Crystallogr D Biol Crystallogr. 2003 Oct;59(Pt 10):1731-6
references.pmid: 14501111
references.citation: Acta Crystallogr D Biol Crystallogr. 2009 Oct;65(Pt 10):1089-97
references.pmid: 19770506
references.citation: Acta Crystallogr Sect E Struct Rep Online. 2008 Jun 19;64(Pt 7):o1286
references.pmid: 21202917
references.citation: Acta Crystallogr A. 2008 Jan;64(Pt 1):112-22
references.pmid: 18156677
references.citation: Acta Crystallogr D Biol Crystallogr. 2005 Sep;61(Pt 9):1302-5
references.pmid: 16131765
references.citation: Acta Crystallogr D Biol Crystallogr. 2009 Mar;65(Pt 3):220-8
references.pmid: 19237744
references.citation: Acta Crystallogr D Biol Crystallogr. 1997 May 1;53(Pt 3):240-55
references.pmid: 15299926
references.citation: Nucleic Acids Res. 2007 Jul;35(Web Server issue):W375-83
references.pmid: 17452350
references.citation: Acta Crystallogr D Biol Crystallogr. 2002 Oct;58(Pt 10 Pt 2):1772-9
references.pmid: 12351820
references.citation: Protein Sci. 2008 Jul;17(7):1175-87
references.pmid: 18445622
references.citation: RNA. 2009 Apr;15(4):707-15
references.pmid: 19228585
references.citation: Acta Crystallogr D Biol Crystallogr. 2010 Apr;66(Pt 4):420-5
references.pmid: 20382995
references.citation: Acta Crystallogr D Biol Crystallogr. 2008 Nov;64(Pt 11):1179-82
references.pmid: 19020357
references.citation: Acta Crystallogr D Biol Crystallogr. 2008 Jul;D64(Pt 7):711-29
references.pmid: 18566507
references.citation: Acta Crystallogr D Biol Crystallogr. 2002 Aug;58(Pt 8):1262-8
references.pmid: 12136136
references.citation: Acta Crystallogr D Biol Crystallogr. 2004 Dec;60(Pt 12 Pt 1):2126-32
references.pmid: 15572765
references.citation: Nat Struct Biol. 1999 May;6(5):458-63
references.pmid: 10331874
references.citation: Structure. 2000 Jul 15;8(7):R143-9
references.pmid: 10903954
references.citation: Acta Crystallogr C. 2009 May;65(Pt 5):o237-9
references.pmid: 19407425