Description
Return one ionizable group's fractional occupancy and charge.
Biochemical amounts, ionization and free energies depend on units, standard states, activities and molecular composition. A supplied concentration ratio or independent-group formula is one local model relation rather than a complete equilibrium or verified molecular characterization.
Return one ionizable group's fractional occupancy and charge.
When to use this tool
Use Protein Net Charge One Group Term when checking the stated biochemical amount, charge, equilibrium or material-basis convention.
How to use the tool and how it works
- Enter ph, pka, groupCount, acidic. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read ionizedFraction, charge. Use the output convention below.
Return one ionizable group's fractional occupancy and charge. Require nonnegative whole groupCount; acidic fraction = 1/(1+10^(pKa-pH)) with negative charge, basic fraction uses 10^(pH-pKa) with positive charge.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| ph | Ph | Required. Finite number. |
| pka | Pka | Required. Finite number. |
| groupCount | Group Count | Required. Safe integer; minimum 0. |
| acidic | Acidic | Required. Boolean. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| ionizedFraction | Ionized Fraction | Required. Finite number. |
| charge | Charge | Required. Finite number. |
{
"input": {
"ph": 7,
"pka": 7,
"groupCount": 4,
"acidic": true
},
"output": {
"ionizedFraction": 0.5,
"charge": -2
}
}Limitations and assumptions
- This assumes independent identical monoprotic groups; no full protein sequence, coupled titration or isoelectric point is solved.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use compatible standard states, verified chemical identity and an appropriate complete activity/speciation or measurement model for physical interpretation.
References
Similar or alternative tools
- Henderson Hasselbalch Species Ratio Term
Return monoprotic acid/base concentrations from supplied pH/pKa.
- Buffer Total Species Count
Return total supplied conjugate-species amount and base share.