Multiple m/z peaks in ESI-MS for one protein likely result from:
A single purified protein subjected to electrospray appears as multiple peaks not indicating heterogeneity but reflecting distribution of protonation states. Each molecule acquires varying numbers of protons at basic sites during desolvation, forming species [M+10H]10+ , [M+11H]11+ and so on, each with distinct mass-to-charge ratio. Mass spectrometer detects this envelope, and deconvolution algorithm calculates neutral mass. Multiple peaks therefore result from multiple charge states, intrinsic to ESI. Degradation, impurities or dimerization would alter neutral mass or produce additional decon
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
