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Protein & Biochemistry calculators

Protein work starts with numbers: the molecular weight and isoelectric point from a sequence, the extinction coefficient that turns an absorbance into a concentration, and the colorimetric assays (Bradford, BCA, Lowry) that measure protein in a mixture against a standard curve.

The second half covers what proteins do: enzyme activity and specific activity, Michaelis-Menten kinetics with a nonlinear fit, IC50 and EC50 from dose-response curves, binding affinity, and the thermodynamics (free energy and equilibrium constants) that connect them. Calibration models are stated explicitly on every assay page, and fitted values come with their uncertainty.

Protein and Peptide Molecular Weight CalculatorAverage or monoisotopic mass from a sequence, with end groupsOpen calculatorAmino Acid Composition CalculatorResidue counts, GRAVY, aliphatic index and charge contentOpen calculatorProtein Isoelectric Point (pI) CalculatorEstimated pI and the net charge at any pHOpen calculatorProtein Extinction Coefficient Calculatorε280 and A 0.1% from sequence, with optional concentrationOpen calculatorProtein Concentration Calculator (A280, A205)Concentration from absorbance, and mg/mL ⇄ µMOpen calculatorBradford Protein Assay CalculatorProtein concentration from a Bradford standard curveOpen calculatorBCA Protein Assay CalculatorProtein concentration from a BCA standard curveOpen calculatorLowry Protein Assay CalculatorProtein concentration from a Lowry standard curveOpen calculatorEnzyme Activity Calculator (Units, Specific Activity)U/mL from an absorbance rate, specific activity and unit conversionOpen calculatorMichaelis-Menten CalculatorRate at a given [S], or [S] for a target rate, with the curveOpen calculatorEnzyme Kinetics Calculator (Km, Vmax Fit)Nonlinear Michaelis-Menten fit, with Lineweaver-Burk for comparisonOpen calculatorIC50 CalculatorFour-parameter logistic fit, with Ki by Cheng-PrusoffOpen calculatorEC50 CalculatorFour-parameter logistic fit for a rising dose-response curveOpen calculatorProtein Binding Affinity (Kd) CalculatorKd and Bmax from a saturation curve, and fraction boundOpen calculatorGibbs Free Energy CalculatorΔG from K, from ΔH and ΔS, and under non-standard conditionsOpen calculatorEquilibrium Constant CalculatorK from concentrations, Ka ⇄ Kd ⇄ pKd, and K at another temperatureOpen calculator

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Service documentation, failure modes and parts for the instruments these calculations are used with.

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