This Python module contains a Formula class for working with chemical formulas, as well as methods for creating, manipulating, and analyzing formulas. It also includes functionality for dealing with adducts and calculating monoisotopic masses.
This Python module provides a Formula class that allows you to work with chemical formulas. It includes the following features:
- Create Formula objects from Hill notation, SMILES, and InChI.
- Perform basic mathematical operations on formulas (addition, subtraction, multiplication).
- Calculate the monoisotopic mass of a formula.
- Check if a given mass is within a specified tolerance of the formula's mass.
- Analyze possible fragment masses explained by a formula and adduct.
To use this module, you'll need Python 3.x and the required dependencies. You can install the dependencies using pip:
pip install rdkit urllib3
## Usage
### Creating Formula Objects
You can create a Formula object using various methods:
- `Formula.formula_from_str_hill(formula_str: str, adduct: str) -> 'Formula'`: Create a Formula object from a chemical formula string in Hill notation.
- `Formula.formula_from_str(formula_str: str, adduct: str, no_api: bool = False) -> 'Formula'`: Create a Formula object from a chemical formula string. You can disable API calls for formula resolution by setting `no_api` to `True`.
- `Formula.formula_from_smiles(smiles: str, adduct: str, no_api: bool = False) -> 'Formula'`: Create a Formula object from a SMILES string representing a molecular structure.
- `Formula.formula_from_inchi(inchi: str, adduct: str, no_api: bool = False) -> 'Formula'`: Create a Formula object from an InChI string representing a molecular structure.
### Basic Operations
You can perform various operations on Formula objects:
- Addition: `formula1 + formula2`
- Subtraction: `formula1 - formula2`
- Multiplication: `formula * num`
### Calculating Mass
You can calculate the monoisotopic mass of a formula and check if it matches an external mass:
- `get_monoisotopic_mass() -> float`: Get the monoisotopic mass of the formula.
- `get_monoisotopic_mass_with_adduct() -> float`: Get the monoisotopic mass of the formula, considering the adduct.
- `check_monoisotopic_mass(external_mass: Union[float, int], mass_tolerance_in_ppm: Union[int, float] = __default_ppm) -> bool`: Check if the monoisotopic mass is within a specified tolerance of an external mass.
- `check_monoisotopic_mass_with_adduct(external_mass: Union[float, int], mass_tolerance_in_ppm: Union[int, float] = __default_ppm) -> bool`: Check if the monoisotopic mass, considering the adduct, is within a specified tolerance of an external mass.
### Fragment Analysis
You can analyze potential fragment masses explained by a formula and adduct:
- `check_possible_fragment_mz(fragment_mz: Union[float, int], ppm: Union[float, int] = __default_ppm) -> bool`: Check if a fragment mass can be explained by the formula and adduct.
- `percentage_intensity_fragments_explained_by_formula(fragments_mz_intensities: Dict[Union[float, int], Union[float, int]], ppm: Union[float, int] = __default_ppm) -> float`: Calculate the percentage of intensity of fragments explained by the formula and adduct.
## Examples
Here are some examples of how to use the Formula class:
```python
# Create Formula objects
formula1 = Formula.formula_from_str_hill("C5H5O4", "[M+H]+")
formula2 = Formula.formula_from_smiles("CCO", "[M+NH4]+")
formula3 = formula1 + formula2
# Calculate monoisotopic mass
mass1 = formula1.get_monoisotopic_mass()
mass2 = formula2.get_monoisotopic_mass_with_adduct()
print(f"Mass of formula1: {mass1}")
print(f"Mass of formula2 with adduct: {mass2}")
# Check mass against an external mass with a tolerance of 5 ppm
check_monoisotopic_mass = formula1.check_monoisotopic_mass(121.05142,5)
check_monoisotopic_mass_with_adduct = formula1.check_monoisotopic_mass_with_adduct(122.05862,5)