TABLE 1.
List of compounds used in the project as well as LC-MS/MS parametersa
| Compound (abbreviation) | Structure | Mol wt (g/ mol) | Retention time (min) | MRM parent product m/zb | LOD (nM) |
|---|---|---|---|---|---|
| 1,3-Diamino-propane (DAP) |
|
74.1 | 1.90 | 75.1–58.1 | 4.51 |
| Putrescine (PUT) |
|
88.2 | 1.92 | 89.1–72 | 2.29 |
| Cadaverine (CAD) |
|
102.2 | 1.95 | 103.1– 69, 86 | 1.29 |
| Agmatine (AGM) |
|
130.2 | 2.01 | 131.2–72, 60 | 1.85 |
| Norspermidine (NSD) |
|
131.2 | 1.74 | 132.2–115, 98 | 2.06 |
| Spermidine (SPD) |
|
145.3 | 1.75 | 146.1–112.1, 72 | 1.25 |
| 13C-spermidine (IS) |
|
149.2 | 1.78 | 150.2–116.1, 76.1 | |
| Homospermidine (HSD) |
|
159.3 | 1.71 | 160.2–126.0, 83.8 | 5.58 |
aThe instrumental limit of detection (LOD) for the LC-MS/MS was calculated as three times the standard deviation of the lowest detectable concentration of standards used (5 nM). The actual LOD of samples varied based on how much the samples were concentrated but was generally 2 to 1,000-fold lower than the instrumental LOD. A collision energy of 20 eV was used for all analytes except 1,3-diaminopropane, which had a CE of 10 eV, and homospermidine, which had a CE of 30 eV.
bThe first listed product m/z was used for quantification; the second was used for verification. In cases where no second product is listed, the other products were too small for accurate identification.