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Title
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Differences in crystal properties and ligand affinities of an antifluorescyl Fab (4-4-20) in two solvent systems.
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Authors
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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.
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Ref.
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Proteins, 1988,
3,
155-160.
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PubMed id
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Abstract
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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-methyl-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 x 10(10) 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 Fab during
crystallization trials. In PEG, the ligand remained firmly bound to the protein.
The liganded Fab crystallized in the monoclinic space group P2(1) in PEG, with a
= 58.6, b = 97.2, c = 44.5 A and beta = 95.2 degrees. In MPD the space group was
triclinic P1, with a = 58.3, b = 43.4, c = 42.3 A, alpha = 83.9 degrees, beta =
87.6 degrees, and gamma = 84.5 degrees. X-ray diffraction data were collected
for both forms to 2.5-A resolution. Surprisingly, the triclinic form of the
liganed antifluorescyl Fab 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.
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