th  - 1988 - 51st ENC Conference

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I A COMPLETELY INTEGRATED NETWORK OF HOME--BUILT
AND COMMERCIAL NMR SPECTROMETERS. Donald A. Bouchard*
and Stanley J. Opella, Department of Chemistry, Univ. of Pennsylvania,
Philadelphia, PA 19104-6323
A description of a local-area laboratory network consisting of three home-
built DEC microVAX-II controlled spectrometer nodes, two DEC PDP-
11/23 commercial spectrometer nodes, and a central data-processing node
will be presented. The design of the microVAX-II home--built spectrometers
will also be presented. The spectrometer software provides a system to de-
sign and execute NMR experiments of any complexity, integrating the large
base of existing applications with NMR spectroscopy. The local-area NMR
network is bridged to a departmental computer facility consisting of a VAX
11/785 and 1i/750 each utilizing DECnet and TCP/IP networking protocols,
providing transparent links to most national and international networks.
125 NMR vs. CIRCULAR DICHROISM: WrHAT CAN WE SAY ABOUT
HELICITY? Ronald W. Behling,* Peter A. Mirau, and Lynn W. Jelinski, AT&T Bell Laboratories,
Murray Hill, NJ 07974.
The S-peptide is formed by enzymatic cleavage of ribonuclease A, and is composed of amino acids 1 -
20. The S-peptide can be recombined with residues 21 - 124 (the S-protein), and this non-covalent
complex is enzymatically active and its crystal su'ucture is known. The crystal structure shows that
residues 3 - 13 form an a-helix that is virtually identical to the (x-helix formed by residues 3 - 13 in
intact ribonuclease A. Circular dichroism studies suggest that the S-peptide is approximately 50%
helical under certain salt, pH, and temperature conditions.
We present results that address the question: what does 50% helical mean? High resolution proton
NMR spectra were obtained for the S-peptide in 1.0 M NaC1, pD 5.3, and 0 *C. These spectra include
2D-double quantum filtered COSY, 2D-NOE, and selective and non-selective T: experiments. The
relaxation experiments suggest that the S-peptide in solution has dimensions that are substantially
different from those predicted from the crystal structure, and that considerable internal motions are
present. The measured 2D-NOE was compared with the 2D-NOE calculated from the crystal structure.
The experimental NOE's are substantially different from the predicted NOE's, illustrating that all of the
details of the peptide conformation are not preserved in solution.
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