th  - 1988 - 51st ENC Conference

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A HYPO-RELAXATION AGENT; SIMULTANEOUS USE WITH HYPER-RELAXATION
AGENTS TO IMPROVE LOCALIZED CONTRAST IN NMR IMAGING.
Jonathan P. Lee *
Department of Diagnostic Radiology
The New England Deaconess Hospital and Harvard Medical School
There are at least six types of i~rac~ions which can contribute to spin-
lattice (Tl) relaxation in NMR of solutionsl The relative difference in the
amount thaf any specific interaction contributes to the total relaxation rate
at discrete locations is believed to be a major contributing factor in image
contrast. So called "contrast agents" (CAs) act in part by increasing the
contribution of paramagnetic interaction to the rate of T 1 relaxation. While
the relative difference between T 1 relaxation at discrete locations is increased,
it can be argued that there is an overall decrease in the potential dynamic
range for image contrast.
If one were to decrease the contribution of another type of interaction
which contributes to T I relaxation, and furthermore be able to simultaneously
effect spatial localization between this decrease and the increase observed
from CAs, then it follows that the potential dynamic range of image contrast
would be extended. In practice this would "push" one location's T] up, and
another's down, thus extending in both directions the relative differences in
T I relaxation and thereby the relative image contrast.
I. Becker, Edwin D.; in High Resolution NMR, Academic Press, 1980.
4 9
]
l Sequence-specific H NMR Assignments for Cobrotoxin
Chin Yu*, Chi-Yina ~Jano
Chemistry Department , National Tsing Hua University, Hsinchu, Taiwan
Cobrotoxin is a neurotoxic protein isolated from the venom of
Taiwan cobra (Naja naja atra). This protein, which blocks the
neuromuscular transmission at the post-synaptic membrane by the
specific binding to the acetylcholine receptors, contains 62 amino
acid residues (Mr 6949) with four disulfide brid~es.
The assignment of the IH NIIR spectr~n at 30°C of cobrotoxin is
described and ducumented. The assignments are based entirely on the
amino acid sequence, phase-sensitive homonuclear 2D NMR experiments,
idenfication of complete spin systems, NOEs, and studies of pH
dependence of NMR spectrum on 400 MHz.
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