## Introduction

When enabled, the **MS1 correlation column** shows a value ranging from 0 to 1. The closer the value is to 1, the higher the correlation of the observed isotopic distribution is to the expected.

By clicking the red framed button in the picture below, the theoretical isotope distribution of the suggested peptide match is shown in the plot (applicable for Byos version 5.0 and higher):

The green bars show the height of the theoretical isotopes.

The MS1 correlation column value must be enabled at project creation with the following advanced command:

[Byologic]

EnableMS1Correlation=1

## How is the MS1 correlation calculated?

The relative heights of the observed isotopes and the theoretical one can be represented as vectors. The calculated value of the cosine distance between the two vectors is equivalent to the MS1 correlation.