Which MS mode shows a single peak for intact peptide?
Electrospray ionization inherently produces distribution of charge states due to multiple proton attachment, leading to envelope of peaks for single protein species. Tandem mass spectrometry deliberately fragments ions giving many product peaks. Time-of-flight is an analyzer, not ionization mode. MALDI predominantly generates singly protonated species [M+H]+ because matrix-assisted desorption transfers single proton without extensive multiple charging. Consequently, MALDI spectrum of intact peptide typically shows one major monoisotopic peak cluster representing intact molecular weight, simpli
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.