Differences in crystal properties and ligand affinities of an antifluorescyl fab (4‐4‐20) in two solvent systems

A. L. Gibson, J. N. Herron, X. ‐M He, V. A. Patrick, M. L. Mason, J. ‐N Lin, D. M. Kranz, E. W. Voss, A. B. Edmundson

Research output: Contribution to journalArticlepeer-review


An antigen‐binding fragment (Fab) from a murine monoclonal antibody (4‐4‐20) with high affinity for fluorescein was cocrystallized with ligand in polyethylene glycol (PEG) and 2‐methl‐2,4‐pentanediol (MPD) in forms suitable for X‐ray analyses. In MPD the affinity of the intact antibody for fluorescein was 300 times lower than the value (3.4 × 1010 M−1) obtained in aqueous buffers. This decreased affinity was manifested by the partial release of bound fluorescein when MPD was added to solutions of liganded Feb during crystallization trials, In PEG, the ligand remained firmly bound to the protein. The liganded Feb crystallized in the monoclinic space group P21 in PEG, with a = 58.6, b = 97.2, c = 44.5 Å and β = 95.2°. In MPD the space group was triclinic P1, with a = 58.3, b = 43.4, c = 42.3 Å, α = 83.9°, β = 87.6°, and γ = 84.5°. X‐ray diffraction data were collected for both forms to 2.5‐Å resolution. Surprisingly, the triclinic form of the liganed antifluorescyl Feb had the same space group, closely similar cell dimensions, and practically the same orientation in the unit cell as an unliganded Fab (BV04‐01) with activity against single‐stranded DNA.

Original languageEnglish (US)
Pages (from-to)155-160
Number of pages6
JournalProteins: Structure, Function, and Bioinformatics
Issue number3
StatePublished - 1988


  • Effects of fluorescein binding
  • MPD
  • high‐affinity combining sites
  • monoclonal antibodies

ASJC Scopus subject areas

  • Structural Biology
  • Biochemistry
  • Molecular Biology


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