Fig. 4. (a) Possible homotrimeric (left) and heterotrimeric (right) helices formed in a mixture of CMPs E and F. For the heterotrimers, only the most favored A₂B and AB₂-type heterotrimers are shown. (b) CD spectroscopic thermal denaturation studies (50 μM in 10 mM aq. NH₄Ac at pH 7, heating rate of 1 °C min^–1) of CMP E (blue), CMP F (orange), and annealed mixtures of CMPs E : F 2 : 1 (black), 1 : 1 (dark grey), and 1 : 2 (brown). (c) Native MS spectra of CMPs E and F and an annealed 1 : 1 mixture thereof. The detected trimers are colored as follows: E·E·E (blue), F·F·F (orange), E·F·F (green), and E·E·F (purple). (d) The thermal denaturation study of a 1 : 1 mixture of CMPs E and F by temperature-controlled native MS shows the unfolding of four coexisting trimeric species. T_m,MS values were determined as follows: 35 °C (E·E·E), 38 °C (E·E·F), 42 °C (E·F·F) and 43 °C (F·F·F).