# Protein Quantification, Enzyme Kinetics, and Sequence Analysis Tools Plan protein assays, convert concentrations, analyze sequences, and interpret enzyme activity, kinetics, inhibition, and binding measurements in one lab workflow. > Canonical page: https://elysiatools.com/en/hubs/protein-quantification-enzyme-kinetics-sequence-tools - **Category:** analyze-calculate - **Keywords:** protein quantification tools, BCA assay calculator, Bradford assay calculator, enzyme kinetics calculator, kcat calculator, Ki IC50 calculator, protein molecular weight, protein pI calculator, protein concentration converter, specific activity calculator ## Overview This hub follows the routine protein-lab path from a sequence or peptide to a quantified and characterized sample. Estimate molecular mass, composition, pI, and extinction coefficient; use Bradford or BCA readings to quantify the preparation; then connect enzyme activity, specific activity, kcat, Km, Ki, catalytic efficiency, and binding affinity. The calculators make units and assumptions explicit for lab planning, education, and result checking. ## Tools - Amino Acid Composition Analyzer: Per-residue counts and mol%, group tallies, Kyte–Doolittle GRAVY score, and ProtParam MW from a sequence. Educational use only. - BCA Assay Calculator (Protein Standard Curve): Least-squares A562 curve fit, back-calculated unknowns with dilution factor, extrapolation flags, and detergent/reducing-agent compatibility notes. Educational use only. - Bradford Assay Calculator (BSA Standard Curve): Least-squares BSA curve, back-calculated unknowns with dilution factor, extrapolation flags, and protein-specific dye-response caveats. Educational use only. - Enzyme Activity Unit Calculator (U, µmol/min): Converts product-amount or ΔA/min assay data into enzyme units: 1 U = 1 µmol/min = 16.67 nkat, with Beer–Lambert absorbance conversion and linear-window checks. Educational use only. - Catalytic Efficiency Calculator (kcat/Km): kcat/Km in M⁻¹s⁻¹ from direct kcat or from Vmax/\[E\], with scientific-notation output and bands up to the diffusion-controlled perfection limit. Educational use only. - Enzyme Inhibition Ki Calculator (Cheng–Prusoff IC50 Conversion): IC50 ↔ Ki conversion for competitive, uncompetitive, and pure noncompetitive inhibition with mechanism notes, potency bands, and tight-binding caveats. Educational use only. - Enzyme Kinetics Calculator (Michaelis-Menten): Calculate reaction velocity with Michaelis-Menten, estimate Km/Vmax via Lineweaver-Burk, and model enzyme inhibition. - Enzyme Turnover Number Calculator (kcat): kcat = Vmax ÷ \[E\]total in min⁻¹ and s⁻¹, entered as enzyme amount, enzyme concentration, or protein concentration + molecular weight; bands results from very slow to catalase-class. Educational use only. - Enzyme Activity Unit Converter (U ↔ katal): Converts activity values exactly between U/mU/µU and katal/mkat/µkat/nkat/pkat (1 U = 16.67 nkat, 1 kat = 6×10⁷ U). Educational use only. - Peptide Mass Calculator (Monoisotopic/Average): Sums ProtParam residue masses for a peptide sequence (mono or average) and reports M, \[M+H\]⁺, \[M+Na\]⁺, \[M+2H\]²⁺. Educational use only. - Protein Concentration Converter (mg/mL ↔ µM ↔ %): One-step protein unit conversion across mg/mL, µg/mL, g/L, % w/v, µM, nM, mM, and pmol/µL via molecular weight, with bench landmarks. Educational use only. - Protein–DNA Binding Affinity Calculator (Kd Estimate): Single-point 1:1 Kd estimate: Kd = \[P\] × (1−f)/f from a direct fraction or anisotropy-derived fraction, plus ΔG° = RT·ln(Kd) and affinity bands from very tight (<1 nM) to weak (>1 µM). Cantor & Schimmel / Heyduk & Lee / Lakowicz derived. Educational use only. - Protein Extinction Coefficient Calculator (ε280): ε280 = 5500×Trp + 1490×Tyr + 125×cystine (Pace 1995, ±5%) from a sequence or residue counts, with reduced/oxidized brackets, ProtParam molecular weight, A0.1% = ε/MW, and c = A280/ε concentration conversion. Gill & von Hippel / Pace / ProtParam derived. Educational use only. - Protein Isoelectric Point Calculator (pI by Composition): Theoretical pI via the simplified ExPASy/Bjellqvist pKa set with bisection to zero net charge, plus net charge at pH 7.4, ProtParam average molecular weight, and charged composition. Bjellqvist 1993 / Gasteiger 2003 derived. Educational use only. - Protein Molecular Weight Calculator (from Sequence): MW = Σ ProtParam average residue masses + H₂O, with ambiguity-code handling, kDa/mean-residue output, and unmodified-chain caveats. Educational use only. - Specific Activity Calculator (U/mg protein): Specific activity = U ÷ mg protein (or U/mL ÷ mg/mL): the purity metric of every purification table, with nkat/mg conversion and the kcat/MW purity ceiling. Educational use only. ## Frequently asked questions ### What protein-lab tasks does this hub cover? It covers sequence properties, peptide and protein mass, concentration conversion, Bradford and BCA standard curves, enzyme activity and kinetics, inhibitor potency, specific activity, and protein-DNA binding estimates. ### When should I use Bradford, BCA, or A280? Their compatibility differs by sample matrix. Bradford can be sensitive to protein composition and detergents; BCA is commonly more detergent-tolerant but is affected by reducing agents; A280 depends on aromatic residues and nucleic-acid correction. Review the tool caveats and validate against an appropriate standard. ### Are these calculators a substitute for an assay protocol? No. They calculate from the values you supply. 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