feat(mf-parser): add info about number of isotopologues

Author: lpatiny

packages/mf-parser/src/__tests__/MF.test.ts

@@ -70,6 +70,7 @@ describe('MF', () => {
         },
       ],
       monoisotopicMass: 24,
+      nbIsotopologues: 3,
       mass: 24.021471793470496,
       charge: 0,
       unsaturation: 4,
@@ -205,6 +206,7 @@ describe('MF', () => {
         },
       ],
       monoisotopicMass: 137.09712720211002,
+      nbIsotopologues: 476,
       mass: 137.6511082393577,
       charge: 0,
       unsaturation: 0,

packages/mf-parser/src/util/__tests__/getNumberOfIopologues.test.ts

@@ -0,0 +1,21 @@
+import { test, expect } from 'vitest';
+
+import { MF } from '../../MF';
+import { getNumberOfIsotopologues } from '../getNumberOfIsotopologues';
+
+const tests = [
+  { mf: 'C2', expected: 3 },
+  { mf: 'C1000', expected: 1001 },
+  { mf: 'CH', expected: 4 },
+  { mf: 'CH2', expected: 6 },
+  { mf: 'S', expected: 4 },
+  { mf: 'S2', expected: 10 },
+];
+
+test.each(tests)(
+  'getNumberOfIsotopologues $mf to be $expected',
+  ({ mf, expected }) => {
+    const atoms = new MF(mf).getInfo().atoms;
+    expect(getNumberOfIsotopologues(atoms)).toBe(expected);
+  },
+);

packages/mf-parser/src/util/__tests__/toDisplay.test.js

@@ -110,9 +110,10 @@ let tests = [
   },
 ];
 
-test.each(tests)('toDisplay', (aTest) => {
-  let display = toDisplay(aTest.parsed);
-  expect(display).toMatchObject(aTest.result);
+// eslint-disable-next-line no-unused-vars
+test.each(tests)('toDisplay $mf', ({ mf, parsed, result }) => {
+  let display = toDisplay(parsed);
+  expect(display).toMatchObject(result);
 });
 
 const testsCharges = [
@@ -174,10 +175,10 @@ const testsCharges = [
   },
 ];
 
-test.each(testsCharges)('toDisplay simple charges', (aTest) => {
-  const parsed = new MFInternal(aTest.mf).parsed;
+test.each(testsCharges)('toDisplay simple charges $mf', ({ mf, result }) => {
+  const parsed = new MFInternal(mf).parsed;
   let display = toDisplay(parsed);
-  expect(display).toMatchObject(aTest.result);
+  expect(display).toMatchObject(result);
 });
 
 const testsParenthesis = [
@@ -243,8 +244,8 @@ const testsParenthesis = [
   },
 ];
 
-test.each(testsParenthesis)('toDisplay parenthesis', (aTest) => {
-  const parsed = new MFInternal(aTest.mf).parsed;
+test.each(testsParenthesis)('toDisplay parenthesis $mf', ({ mf, result }) => {
+  const parsed = new MFInternal(mf).parsed;
   let display = toDisplay(parsed);
-  expect(display).toMatchObject(aTest.result);
+  expect(display).toMatchObject(result);
 });

packages/mf-parser/src/util/getInfoInternal.js

@@ -9,6 +9,7 @@ import { groupsObject as groups } from 'chemical-groups';
 import { Kind } from '../Kind';
 
 import { getIsotopeRatioInfo } from './getIsotopeRatioInfo';
+import { getNumberOfIsotopologues } from './getNumberOfIsotopologues';
 import { partToAtoms } from './partToAtoms';
 import { partToMF } from './partToMF';
 
@@ -65,6 +66,7 @@ export function getInfoInternal(parts, options = {}) {
       result.atoms[atom] += part.atoms[atom];
     }
   }
+  result.nbIsotopologues = getNumberOfIsotopologues(result.atoms);
   return result;
 }
 

packages/mf-parser/src/util/getNumberOfIsotopologues.ts

@@ -0,0 +1,40 @@
+import { elementsAndStableIsotopesObject } from 'chemical-elements';
+
+import type { AtomsMap } from './partToAtoms';
+
+/**
+ * Return the theoretical number of isotopologues for a given MF.
+ * This method will not take into account possible non natural isotopic distribution (e.g. 13C enrichment)
+ * @param atoms
+ * @returns
+ */
+export function getNumberOfIsotopologues(atoms: AtomsMap) {
+  let result = 1;
+  for (const atom in atoms) {
+    const nbIsotopes = elementsAndStableIsotopesObject[atom]?.isotopes.length;
+    if (!nbIsotopes) {
+      throw new Error(`No stable isotopes found for ${atom}`);
+    }
+    const nbAtoms = atoms[atom];
+    result *= getNbCombinationsPerAtom(nbAtoms, nbIsotopes);
+  }
+  return result;
+}
+
+/**
+ * Returns the number of isotopologues for one specific atom
+ *
+ * @param nbAtoms
+ * @param nbIsotopes
+ * @returns
+ */
+function getNbCombinationsPerAtom(nbAtoms: number, nbIsotopes: number) {
+  let result = 1;
+  for (let i = nbAtoms + 1; i < nbAtoms + nbIsotopes; i++) {
+    result *= i;
+  }
+  for (let i = 2; i < nbIsotopes; i++) {
+    result /= i;
+  }
+  return result;
+}