Parameters obtained in the analyses of the ESE and ESEEM data.§

§Estimated errors: 5%(TM), 10%(x), 13% (Cex), 5% (kD), 10% (Π). Abbreviations: n3-s-a (the n3-s is within SBA15a containing pure water); n3-s-b (the n3-s is within SBA15b containing pure water); n3-s-sol(s) (the n3-s is in a vitrified bulk solvent containing 40 wt% sucrose, (s), in D2O or H2O); PPm3-s-sol(g) (PPm3-s is in a vitrified bulk solvent containing 40v/v% glycerol in H2O; deuterated glycerol is used if the solvent is D2O, a condition of which is represented by sol(dg)/D2O in main text); PPm3-s-sol(s) (PPm3-s is in a vitrified bulk solvent containing 40 wt% sucrose in D2O or H2O). In all of the experiments, the surface group of the nanochannels is modified to –SiOD in advance if D2O is used. See Method for details.#The values of TM and x are obtained in the analysis of the pulsed ESE measurements using a stretched exponential function, , where τ is the time between the two pulses, x the exponent, and Y(0) is the echo intensity at τ = 0. The obtained values are used to yield Cex using Eq. (2). The Cex represents ESE-based water accessibility within the range of ∼2 nm from the nitroxide spin.¶The kD values are obtained in the theoretical analysis of the ESEEM measurements as described in Figure 3. The best-fit values for the damping constant (τ0) and phase (φ) are very close together (2.9∼3.0). The Π represents ESEEM-based water accessibility within the range of ∼0.35 nm from the nitroxide spin.