th  - 1988 - 51st ENC Conference

186 (Poster)
The 13C Relaxation Behavior of Ethane Through Its Critical Point
Ronald F. Evilia and Scott L. WhittenSurg:' Dept. of Chemistry,
Univ. of New Orleans, New Orleans, La. 70148
, Jan M. Robert: Dept. of Chemistry, S.G. Mudd Bldg. #6, Lehigh
Univ., Bethlehem, Pa. 18015
The longitudinal relaxation time of 13C in the ethane molecule has been
measured over a temperature range of -i01 to +50°C, for a sample at the
critical density. T I appears to vary with temperature, as anticipated;
however, a discontinuity in the relaxation behavior is apparent at the
critical point. From the experimental data, the critical constant may
be obtained.
[~ 1 87 INMR INVESTIGATION OF THE CYCLOPHILIN:CYCLOSPORIN COMPLEX. Heald SL,
Gooley P, Armitage IM, Johnson C, Harding MW*, Handschumacher RE*. Departments of
Molecular Biophysics and Biochemistry, Diagnostic Radiology and *Pharmacology, Yale
University Schoor of Medicine, New Haven, CT 06510.
Cyclophllln (CyP) is a low molecular weight protein which specifically binds
the potent immunosuppressant, cyclosporin A (CsA). The amino acid sequence has been
determined (163 residues, Mr 17,737) on the major bovine isoform of CyP. The primary
goal of this work is to identify the CsA-binding site in cyclophilin. This
investigation has proceeded along 3 pathways: (I) conformational studies on the
drug, CsA; (II) probing the CsA:CyP complex by IH NMR and (III) through NMR-labelled
CsA analogues.
Cyclosporln A goes from a single averaged conformation observed in CDCI 3 to
multiple conformations in polar solvents. Several of the individual conformations
observed in the CH3OD/"H20 mixture are identified based on the HOHAHA and ROESY spin-
locking experiments.
Drug-free cyclophilin has been characterized by the IH 2D NMR experiments:
COSY, HOHAHA and NOESY. Amino acid types have been assigned in the aromatic and
upfield methyl spectral regions. A comparative study has been carried out on the
CsA:CyP complex. The amino acid residues predominately involved in complexation are
readily identified by this method. Site-specific assignment of these residues is
assisted by the use of NMR-labelled CsA analogues in conjunction with heteronuclear
multiple quantum and isotope-directed nOe NMR experiments. (Supported by NIH grant
DE 18778, American Cancer Society CH-67-28 and Merck & Co., Inc.).
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