Table I.
Assignments of amino acid and ammonium 15N chemical shifts
| Sample | D2O | Gln Amide | Asn Amide | Ala | Gln Amino | Glu | Asn Amino | Asp | γ-Aminobutyric Acid (GABA) | NH4+ |
|---|---|---|---|---|---|---|---|---|---|---|
| % | ppm | |||||||||
| Authentic 15N standards (pH 7) | 10 | 90.86 | 90.51 | – | 19.85 | 19.65 | 18.90 | 18.34 | 11.75 | −0.26 |
| Dead 15N-enriched pea nodules immersed in buffer (pH 6) | 20 | – | 90.6 | – | – | – | 18.8 | – | 11.6 | – |
| Extract from dead nodules (pH 5.8) | 4 | – | 90.48 | 22.06 | – | – | 19.07 | – | 11.79 | −0.14 |
| Metabolically active, 15N2-fixing pea nodules | 10 | – | 90.7 | – | 19.6 | 19.6 | – | – | – | −4.2 |
| Metabolically active, 15N2-fixing L. japonicum nodules | 10 | – | 90.7 | – | 19.6 | 19.6 | 18.4 | 18.4 | 11.3 | −4.1 |