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S1 Supplementary information for Hydration-temperature dependent fluorescence spectra of Laurdan conformers in a DPPC membrane. S. Knippenberg,1* K. De,2 C. Aisenbrey,2 B. Bechinger,2,3 S. Osella,4,* 1 Hasselt University, Theory Lab, Agoralaan Building D, 3590 Diepenbeek, Belgium. 2 University of Strasbourg/CNRS, UMR7177, Institut de Chimie de Strasbourg, Strasbourg, France. 3 Institut Universitaire de France (IUF), Paris, France. 4 Chemical and Biological Systems Simulation Lab, Centre of New Technologies, University of Warsaw, Banacha 2C, 02-097 Warsaw, Poland. Email addresses: [email protected] (SK); [email protected] (SO)
S2 Figure S1 Variation of the angle of the Laurdan TDM with the z-axis for windows of 40 ns between 240 and 400 ns in both MD runs for 298K. The arrow in the inset indicate the orientation of the transition dipole moment vector considered for the analysis.
S3 Figure S2 Distributions of the angles of the transition state dipole moment (‘tdm’, at the left hand side) as well as the long molecular axis (‘alpha tilt’, at the right hand side) with respect to the z-axis of the DPPC (L’) membrane at different temperatures. The calculations have been done using the S1 excited state for Conf-I (top) and Conf-II (bottom).
S4 Figure S3 Comparison between the orientations of the tdm with respect to the z-axis and of the -tilt angle of the first excited and the ground state in DPPC at 298K.
S5 Figure S4 Distribution of the position of the N-atoms (left columns) and O-atoms (right columns) in the headgroup of Laurdan excited in the S1 state embedded in the DPPC membrane at different temperatures. As a guide to the eye, these densities have been magnified 400 times. The reported DPPC density has been considered for T=305K.
S6 Figure S5 Distribution of the DPPC membrane at different temperatures. The phosphorous atoms distribution is also reported and have been magnified 400 times. Figure S6 Distance (nm) of the density maxima of the Nand O-atoms in the head group of Laurdan in its S1 excited state with respect to the center of the DPPC membrane at different temperatures. Error bars have been computed considering HWHM of the distribution plots reported in Fig. S4.
S7 Figure S7 Distribution of the characteristic C-C-C-C dihedral angles of Laurdan embedded in the DPPC membrane at different temperatures, from MD using the charges of the S1 excited state for Conf-I (top) and Conf-II (bottom).
S8 Figure S8 Density distribution of the head group of Laurdan in the DPPC membrane at different temperatures. The calculations have been done using the S1 excited state for Conf-I (top) and Conf-II (bottom) of Laurdan. The reported DPPC density has been considered for T=305K.
S9 Figure S9 Radial distribution functions of water with respect to the Laurdan head of Conf-I (top) and Conf-II (bottom). The vertical purple and orange lines note the first and second solvation shells, respectively. Figure S10 Hydrogen bonds for Conf-I (left) and Conf-II (right) with cut-off at 3.5 Å (top row) and 5.0 Å (bottom row).
S16 Figure S17 Fluorescence spectra of Laurdan embedded in DPPC at different temperatures.
S17 Figure S18 Evolution of the max and averaged emission for the S1 state with respect to the increase of temperature for both Conf-I and Conf-II. Error bars have been computed considering HWHM of the distribution plots reported in Fig. S13. Table S4 Detailed analysis of the transitions for the first excited state emission for both conformers at different temperatures. Max wavelength (nm) Aver wavelength (nm) o.s. Lambda transition 270-I 365 343 0.23 0.65 H → L 270-II 380 360 0.29 0.64 H → L 280-I 361 352 0.25 0.63 H → L 280-II 383 362 0.32 0.63 H → L 290-I 368 351 0.28 0.63 H → L 290-II 363 344 0.17 0.67 H → L 298-I 367 352 0.30 0.63 H → L 298-II 379 359 0.29 0.64 H → L 305-I 373 356 0.31 0.61 H → L 305-II 394 358 0.29 0.64 H → L 310-I 376 348 0.27 0.63 H → L 310-II 381 354 0.29 0.65 H → L 315-I 390 353 0.30 0.63 H → L 315-II 386 360 0.30 0.63 H → L 320-I 368 352 0.28 0.62 H → L 320-II 385 362 0.29 0.64 H → L
S18 Figure S19 Experimentally obtained emission decay curves for Laurdan obtained at 440 nm and 490 nm at different temperatures (given in °C). Table S5 Fitted time constants and coefficients for the anistropy decay of Laurdan at 440 nm and 490 nm (see Figure 8). °C 440 nm (time – ns) 440 nm (static)b 440 nm (decay) 490 nm (time – ns) 490 nm (static) 490 nm (decay) 15 3.61 ns 0.26 0.05 30 2.18 ns 0.25 0.06 39 1.46 ns 0.23 0.13 41a 1.39 ns 0.18 0.21 2.70 0.09 0.25 45 3.39 0 0.37 60 2.41 -0.01 0.36 a For 41°C, the fit has been performed on the first slope of the decay curve only.
S19 b Time resolved anisotropy curves were fitted with the sum of an exponential decay and a static contribution. The amplitude of the exponential decay signifies the free moving space with the indicated correlation time. The static fraction on the other hand characterizes orientation which are not reached and is closed linked to the order (parameter) of the system. Annex two component time resolved anisotropy Each component contributes to the anisotropy signal by: 𝑎𝑖(𝑡)=𝐴((1−𝑠𝑖)10−𝑡 𝜏𝑖𝑎+𝑠𝑖) With the anisotropy of the static molecules A, the fraction of restricted motion 𝑠𝑖, and the correlation time 𝜏𝑖𝑎 of the motion. The contribution is weighted with the signal intensity at time t: 𝜌𝑖(𝑡)=𝐼𝑖10−𝑡 𝜏𝑖 With the fluorescence lifetime𝜏𝑖,and the intensity 𝐼𝑖. The results are weighted as 𝑎𝑡𝑜𝑡(𝑡)=∑𝑎𝑖(𝑡)𝜌𝑖(𝑡) 𝑖∑𝜌𝑖(𝑡) 𝑖 The intensity 𝐼𝑖 is related to the integrated intensity by 𝐼𝑖𝑖𝑛𝑡=2.3 𝐼𝑖𝜏𝑖. Figure S20: simulation of the time resolved anisotropy recorded at 440nm and 41°C. 𝜏1= 3.58 𝑛𝑠, 𝜏2=7.46 𝑛𝑠, 𝑠1=0.23, 𝑠2=0.79, 𝜏1𝑎=1.7𝑛𝑠, 𝜏1𝑎=4.6𝑛𝑠, A=0.3 and 57% integrated signal of component 1 (corresponding to 73% of time resolved signal of component 1).
S20 Table S6 – S1 Charges of Conf-I and Conf-II used for the MD simulations Conf-I Conf-II C1 0.149987 0.090783 C2 -0.063341 -0.054328 C3 -0.141456 -0.104891 C4 0.198368 0.120561 C5 -0.144354 -0.099696 N1 0.100849 0.143498 C6 -0.192474 -0.090797 C7 -0.178828 -0.233771 C8 0.105220 0.059247 C9 -0.195617 -0.153508 C10 0.254657 0.204509 C11 0.544605 0.624376 O1 -0.589656 -0.582874 C12 -0.033513 -0.119036 C13 0.097138 0.075498 C14 0.077406 0.075622 C15 0.000553 0.032927 C16 0.020832 0.044544 C17 -0.019263 -0.053545 C18 0.024202 0.028150 C19 -0.044699 -0.025183 C20 0.085423 0.071581 C21 -0.092458 -0.097457 C22 0.022053 0.034643 C23 0.106697 0.098978 C24 -0.092333 -0.089833
