Practice question

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 deconvoluted masses, so pattern recognition is essential for quality assessment.