Lowry-calculator

An interactive web application for calculating protein concentrations from Lowry assay data. Built with Streamlit, it handles calibration curve fitting, sample concentration calculation, and PDF report generation.

---

Features

• Interactive data entry for calibration standards and samples
• Linear regression of the calibration curve with R² quality feedback
• Automatic protein concentration calculation from up to three absorbance replicates
• Mean and standard deviation per sample
• Dilution factor support
• Warnings for negative absorbances and out-of-range concentrations
• Bar chart of results with error bars
• Downloadable PDF report with calibration curve equation, results table, and chart

---

Requirements

• Python 3.13.9
• The following packages: fpdf2==2.8.7 matplotlib==3.10.9 numpy==2.4.6 pandas==3.0.3 pytest==8.4.2 scipy==1.17.1 streamlit==1.51.0

Install all dependencies with:

```bash
pip install streamlit pandas numpy scipy matplotlib fpdf2

---

Running the App

streamlit run calculator.py

The app will open in your browser at http://localhost:.....

---

Usage

1. Enter calibration data

Fill in the calibration table with your standard concentrations (mg/mL) and their corresponding absorbance values. At least two points with different concentrations are required.

2. Enter sample data

Fill in the sample table with:

• Sample name — left blank defaults to Unknown
• Dilution factor — defaults to 1 if not changed
• Absorbance1, 2, 3 — up to three replicates; at least one is required per sample

3. Calculate

Click Calculate to:

• Fit the calibration curve and display R²
• Calculate protein concentrations for all samples
• Display results as a table and bar chart

4. Download report

Click Download PDF Report to save a report containing the calibration equation, results table, and bar chart.

---

Warnings

The app will notify you if:

• Fewer than two calibration points are entered
• All calibration concentrations are identical
• Negative absorbance values are detected in standards or samples
• Calculated protein concentrations are negative (sample likely below the detection range of the standards)

---

Project Structure

.
├── calculator.py        # Main application
├── test_calculator.py   # Unit tests
└── README.md

---

Limitations

• Sample names longer than approximately 20 characters may be truncated in the PDF table
• The app is designed for single-session use; no data is saved between sessions
• PDF report does not include the calibration curve plot, only the sample concentration chart and calibration equation