Figure 3.

Hsp21 associates with thylakoid membranes in heat‐stressed plants. Mass spectra are shown for the Hsp21 peptide ENSIDVVQQGQQK detected in samples of Thylakoid membranes (upper), from control plants (¹⁴N) and from a 1:1 mix of control (¹⁴N) and heat‐stressed plants (¹⁵N), and samples of Stroma (lower), from control plants (¹⁴N) and from a 1:1 mix of control (¹⁴N) and heat‐stressed plants (¹⁵N). The Hsp21 peptide ENSIDVVQQGQQK is singly charged and has a mass difference of 19 Da between the 14N‐peptide (m/z = 1472.7) and the 15N‐peptide (m/z = 1491.7) due to 13 N‐atoms in each amido‐group, and 1 extra N‐atom in the amino acid side‐chains of N, Q and K. The quantification of the amount of Hsp21 in stroma and thylakoid membranes is shown as L/H‐ratios in Table 3.