Coherent differential scattering cross section per unit volume and unit of PEG volume fraction I/ϕPEG vs. scattering vector q for PEG solutions at T = 20 °C. Lines are best fits following Eq. (2).
Mean short distance, ξ/a, and curvilinear distance, g = m(ξ)/m a , between neighboring PEG chains vs. volume fraction ϕPEG, measured at T = 20 °C, with m a the molar mass of the monomer and a its length from Ref. 15. Straight lines are best power law fits corresponding to and , respectively.
Molar ellipticity θ at 222 nm per amino acid of poly(L-glutamic acid) solutions vs. temperature for different pH. The horizontal dashed line has an ordinate θ1/2 corresponding to the helix fraction 1/2.
Ellipticity θ at 222 nm per amino acid of poly(L-glutamic acid) solutions at pH = 3.75 vs. temperature for different volume fractions of PEG. Full and open symbols correspond to rising and decreasing temperature curves, respectively. The horizontal line has an ordinate θ1/2 corresponding to the helix fraction x h = 1/2.
Helix fraction x h of poly(L-glutamic acid) solutions at pH = 3.75 vs. reduced temperature T/T* for different volume fractions of PEG.
Reverse transition temperature 1/T* vs. logarithm of the accessible volume fraction ln (1 − ϕPEG). Straight lines are guides for the eyes with slopes equal to 1/560 K (Ref. 30) for fully protonated (dashed lines) and 1/317 K (Ref. 31) for fully dissociated (full lines) glutamic acid monomers, respectively. Full symbols: present work (pH = 3.75). Open symbols: from Fig. 5 in Ref. 5 (pH = 5.8). At this latter pH, T*(0) (intercept of dashed and full lines) is not accessible. It has been arbitrary set to 235 K in order the green dashed line fits the data points of Ref. 5.
(Top) Reverse correlation length L h (T*) of helices at the transition vs. reverse mesh size ξ of the PEG network. (Bottom) Average number N h (T*) of amino acid per helix at the transition vs. the ratio L h (T*)/ξ. The close symbol at x-coordinate equal to 0 corresponds to ϕPEG = 0 (i.e., ξ → ∞). Either ξ measured at 20 °C (circles) or ξ(T*) (squares) calculated from Eq. (3) and Ref. 16 are used to compute the x-coordinate.
Summary of the results obtained by circular dichroism measurements: transition temperature T*; Zimm-Bragg parameter σ deduced from the slope at T* of θ(T); extent N h and correlation length L h of helical domains at the transition.
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