| These 7 golden rules have been thoroughly tested | | | | Rule #3: When using established isotopic patterns |
| with an accuracy rate of 98%. Only 0.6% of the | | | | false positives/negatives are mostly eliminated. Mass |
| almost 1/2 million compounds the didn't pass all 7 of | | | | spectrometers measure isotopic abundance patterns |
| the rules. | | | | with only 2-5% relative standard deviation which is |
| | | | low enough to determine the correct patterns. |
| 1. restrictions for the number of elements | | | | Rule #4: More than 99.7% of all formulas were |
| 2. LEWIS and SENIOR chemical rules | | | | included in the Common hydrogen/carbon range of |
| 3. isotopic patterns | | | | ratios between 0.2-3.1. To cover extended range to |
| 4. hydrogen/carbon ratios, | | | | 99.99% of all formulas the hydrogen/carbon of 0.1-6 |
| 5. element ratio of nitrogen, oxygen, phosphor, and | | | | is measured. |
| sulphur versus carbon, | | | | Rule #5: Measuring the element ratio of nitrogen, |
| 6. element ratio probabilities | | | | oxygen, phosphor, and sulphur versus carbon strongly |
| 7. presence of trimethylsilylated compounds. Rule #1: | | | | reduce the number of candidates. This rule only |
| The restrictions for the number of elements were | | | | restricts unlikely high element ratios in molecular |
| calculated by simply dividing the mass range through | | | | formulas. |
| the element mass. The number of elements set in | | | | Rule #6: Using a multiple element count the element |
| formula generation for small molecules was devised | | | | ratio probabilities are determined by use of the |
| from the DNP and Wiley mass spectral databases. | | | | Dictionary of Natural Products, mass spectral libraries |
| Rule #2: LEWIS and SENIOR chemical rules | | | | of NIST02 and Wiley. |
| - The sum of valences or the total number of atoms | | | | Rule #7: The number of trimethylsilylated groups can |
| having odd valences is even | | | | easily be deduced by calculating isotope abundances, |
| - The sum of valences is greater than or equal to | | | | as shown in rule #3. |
| twice the maximum valence | | | | The software scripts and programs, source code and |
| - The sum of valences is greater than or equal to | | | | all supplement development data are freely available |
| twice the number of atoms minus 1Since this test | | | | from the Fiehnlab projects site. When specialized |
| does not allow for all variations in valences, the | | | | target libraries are used the correct identification can |
| maximum valence states for each element are | | | | be as high as 98%. |
| allowed. | | | | BMC Bioinformatics 2007, 8:105doi:10. |