th  - 1988 - 51st ENC Conference

1 22 I IMULTINUCLEAR TWO-DIMENSIONAL APPROACHES TO SEQUENCE-SPECIFIC
RESONANCE ASSIGNMENTS IN A PROTEIN: 13C-13C, 13C-15N, IH-13C, IH-15N, AND IH-IH
CORRELATIONS IN ANABAENA 7120 FLAVODOXIN: Brian J. Stockman*, William M. Westler, Ed
S. Mooberry, and John L. Markley. Department of Biochemistry, College of Agricultural
and Life Sciences, 420 Henry Mall, University of Wisconsln-Madlson, Madison, WI 53706.
A sequential assignment procedure based on heteronuclear correlations is presented. A
two-dlmensional (2D) 13C[13C] Double Quantum Correlation (DQC) NMR experiment (125.76
MHz) has been applied to [26% ul 13C]flavodoxin (MW 21,000). The uniqueness of the
carbon spin systems for 18 of the 20 amino acid types (Asx and Glx degeneracies can be
distinguished via 13C-15N correlations) allowed many aliphatic and aromatic side
chains to be completely outlined, ending with the carbonyl carbon. Carbon spin
systems were then sequentially assigned in the following way. Carbonyl assignments
were extended across the peptide bond to the alpha nitrogen of the following residue
using 2D 13C-15N correlations of [26% ul 13C, 95% ul 15N]flavodoxin. Amide protons
were assigned using 2D IH-15N correlations (H20 solvent), and were correlated to the
alpha carbon protons of the same residue by a double-quantum-filtered COSY experiment.
2D IH-13C correlations were then used to cross assign alpha protons to alpha carbons,
thus allowing identification of the following residue via its carbon spin system.
Alternatively, 13C-15N correlations could be used to assign the alpha carbons of the
next residue (both procedures could be used for redundancy or to overcome unfavorable
resolution). The advantages of using this strategy for sequential assignments
compared to a homonuclear iH-IH strategy are the relative ease with which carbon spin
systems can be assigned in comparison to proton spin systems, and the reliability of
correlations based on scalar coupling as opposed to dipolar coupling. Assignments can
be extended to side-chain proton spin systems via IH-Ioc correlations to carbon spin
systems. [Supported by USDA Competitive Research Grant 85-CRCR-I-1589, NSF Grant
RR023021, and NIH Grants RR023021, RR02781, and GM07215.]
SOLID STATE NUCLEAR MAGNETIC RESONANCE INVESTIGATIONS OF
123 I ORGANOPHOSPHONIC ACID ADSORPTION ON ALUMINA
Neal R. Dando; Larry F. Weiserman and Edward S. Martin
Aluminum Company of America, Alcoa Technical Center, Alcoa Center, PA 15069
Methyl and phenyl phosphonic acid adsorption on gan~na alumina was investigated by
phosphorus-31, carbon-13, and aluminum-27 solid state NMR spectrometry. The
population of chemisorbed and physisorbed species was investigated over a 5-20%
loading range. Physisorption was observed at the lowest loading studied (5%) and
increased monotonically as a function of loading. The population of chemisorbed
species remained constant throughout the loading range studied. Motional dynamics
of the adsorbed species were evaluated by a series of static, magic angle spinning,
high power decoupling and relaxation experiments. Carbon-13 and aluminum-27 data,
while less sensitive to surface phenomena, allowed for more complete characterization
of the substrate and adsorbates.
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