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- Larsson, Göran, et al.
(författare)
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A high-resolution HCANH experiment with enhanced sensitivity via multiple quantum line narrowing
- 1999
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Ingår i: Journal of Biomolecular NMR. - 0925-2738 .- 1573-5001. ; 14:2, s. 169-174
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Tidskriftsartikel (refereegranskat)abstract
- We report a 3D constant-time HCANH experiment (CTSL-HCANH) that uses the slower relaxation of multiple-quantum coherence to increase sensitivity and provides high C(α) resolution. In this experiment the H(α) of the (H(α), C(α)) multiple quanta are selectively spin locked, so that H(α) chemical shift evolution and (1) H-(1)H J-dephasing become ineffective during the relatively long delay needed for C(α) to N coherence transfer. As compared to an HCANH experiment that uses C(α) single-quantum coherence, an average enhancement of 20% was observed on calmodulin in complex with the binding domain of the transcription factor SEF2-1. Compared to CBCANH the signal intensity is approximately twice as good. The favorable relaxation properties of multiple quanta, together with the outstanding C(α) resolution, make the experiment a very good complement to CBCANH and CBCA(CO)NH for sequential assignment of larger proteins for which deuteration is not yet necessary.
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- Schleucher, Jürgen, et al.
(författare)
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Intramolecular deuterium distributions of glucose reveal disequilibrium of chloroplast phosphoglucose isomerase
- 1999
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Ingår i: Plant, Cell and Environment. - : Wiley. - 0140-7791 .- 1365-3040. ; 22:5, s. 525-533
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Tidskriftsartikel (refereegranskat)abstract
- D, deuterium δD(NMR), chemical shift axis in a deuterium NMR spectrum F6P, fructose-6-phosphate G6P, glucose-6-phosphate IRMS, isotope ratio mass spectrometry NMR, nuclear magnetic resonance PGI, phosphoglucose isomerase Intramolecular deuterium distributions of the carbon-bound hydrogens of glucose were measured using deuterium nuclear magnetic resonance. Glucose isolated from leaf starch of common bean (Phaseolus vulgaris cv. Linden) or spinach (Spinacia oleracea cv. Giant nobel) was depleted in deuterium in the C(2) position, compared with glucose isolated from leaf sucrose or bean endosperm starch. In beans, the depletion of C(2) was independent of the light intensity during growth (150 or 700 μmol photons s–1 m–2). The ratio of glucose-6-phosphate to fructose-6-phosphate ([G6P]/[F6P]) in bean chloroplasts was 0·9 in high light, indicating that the phosphoglucose isomerase reaction was not in equilibrium ([G6P]/[F6P]) ≈ 3). This implies that the kinetic isotope effect of phosphoglucose isomerase depleted deuterium in the C(2) position of G6P. Because the depletion was the same, the chloroplastic ([G6P]/[F6P]) ratio was in disequilibrium irrespective of the light intensity. If the ([G6P]/[F6P]) ratio was in equilibrium, a large chloroplastic pool of G6P would be unavailable for regeneration of ribulose-1,5-bisphospate. We argue that chloroplast phosphoglucose isomerase activity is regulated to avoid this. The deuterium depletion of C(2) explains the known low overall deuterium abundance of leaf starch. This example shows that measurements of intramolecular deuterium distributions can be essential to understand overall deuterium abundances of plant material.
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