Quadratic Binding Fit

Liu Lab Kd拟合工具Liu Lab Kd Fitting Tool

保留原始严格二次结合模型，同时新增误差棒、曲线点位导出、以及可选 PNG/JPG 和 PPI 的图片导出。Retains the original strict quadratic binding model, while adding error bars, curve point export, and optional PNG/JPG and PPI image export.

v0.23

Kd 计算原理：基于二次结合模型，用实验浓度 X 与信号 Y 的关系进行非线性拟合，求出最能解释数据的解离常数 Kd。Kd calculation principle: based on the quadratic binding model, the program performs nonlinear fitting on the relationship between experimental concentration X and signal Y to obtain the dissociation constant Kd that best explains the data.

Excel 风格表格Excel-style tables 支持手动方差Manual variance input 支持重复数据自动算误差棒Error bars from replicates 支持曲线 CSV 导出与图片导出Curve CSV & image export
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Model

Y = Ybase + alpha * [AT]

[AT] = 0.5 * (X + fixed + Kd - sqrt((X + fixed + Kd)^2 - 4 * X * fixed))

X     = 可变一方总浓度Total concentration of the variable component
fixed = 另一方固定总浓度Total concentration of the fixed component
Kd    = 解离常数Dissociation constant

Y free拟合：Ybase作为自由参数进行拟合，允许背景信号浮动以获得最佳拟合。Y free fit: Ybase is fitted as a free parameter, allowing the background signal to float for optimal fit.

Y fixed拟合：Ybase固定为用户指定的值，通常用于已知背景信号的情况。Y fixed fit: Ybase is fixed to a user-specified value, typically used when the background signal is known.

参数与导出Parameters and Export

导出曲线的取样点数默认 1000；图片导出按所选 PPI 等比例放大像素尺寸。Default sampling points for exported curves: 1000; image export scales pixel size proportionally based on the selected PPI.

主表可直接粘贴 Excel 的两列或三列数据。误差棒为“手动方差”模式时，第 3 列填写 Var(Y)，程序用 sqrt(Var) 作误差棒长度。Paste two or three columns straight from Excel into the main table. In “manual variance” mode, put Var(Y) in the third column — the error bar length is sqrt(Var).

重复数据模式时，请在下方“重复数据表”输入 X、Y1...Yn。每行至少需要 2 个重复值，程序使用样本方差计算误差棒。In replicate mode, enter X, Y1…Yn in the replicate table below. Each row needs at least 2 replicate values; sample variance drives the error bars.

拟合结果Fitting Results

同时给出 Ybase 自由拟合和 Ybase 固定拟合的结果。Provides results for both the Ybase free fit and the Ybase fixed fit.

主数据表Main Data Table

支持粘贴 Excel 两列或三列：X、Y、Var(Y)。Supports pasting two or three columns from Excel: X, Y, Var(Y).

序号Index 浓度 XConcentration X 信号 YSignal Y 方差 Var(Y)Variance Var(Y) 操作Action

重复数据表Replicate Data Table

在“输入 n 组数据自动计算”模式下使用。每行填一个浓度及其重复信号。Used in “auto-calculate from n replicates” mode. Each row holds one concentration and its replicate signals.

拟合曲线Fitted Curve

黑点为数据点，蓝色误差棒为误差，红色实线为自由拟合，蓝色虚线为固定拟合。Black dots are data points, blue error bars are errors, the red solid line is the free fit, the blue dashed line is the fixed fit.

点击“开始拟合”后，这里会显示拟合曲线。The fitted curve appears here after you press “Start Fitting”.
数据点Data Points Ybase 自由拟合Ybase Free Fit Ybase 固定拟合Ybase Fixed Fit