Figure 1.

Hsp21 protein associates with thylakoid membranes at increased temperature. Mass spectra are shown for three different Hsp21 peptides (ISVEDNVLVIK, ENSIDVVQQGQQK, KVIDVQIQ, all charged 2+), showing an increased proportion of the 14N‐peaks at 45°C compared to 20°C, in relation to the reference 15N‐peaks. Isolated thylakoid membranes were incubated with recombinantly expressed and purified unlabeled (¹⁴N) Hsp21 for 15 min and samples spiked with known amounts of 15N‐labeled Hsp21 before sample processing, tryptic digestion and LC‐MSMS.