TY - JOUR

T1 - Low-Temperature Dynamical Transition in Lipid Bilayers Detected by Spin-Label ESE Spectroscopy

AU - Golysheva, Elena A.

AU - De Zotti, Marta

AU - Toniolo, Claudio

AU - Formaggio, Fernando

AU - Dzuba, Sergei A.

PY - 2018/12/1

Y1 - 2018/12/1

N2 - Data on neutron scattering in biological systems show low-temperature dynamical transition between 170 and 230 K manifesting itself as a drastic increase of the atomic mean-squared displacement, 〈x2〉, detected for hydrogen atoms in the nano- to picosecond time scale. For spin-labeled systems, electron spin echo (ESE) spectroscopy—a pulsed version of electron paramagnetic resonance—is also capable of detection of dynamical transition. A two-pulse ESE decay in frozen matrixes is induced by spin relaxation arising from stochastic molecular librations, and allows to obtain the 〈α2〉τc parameter, where 〈α2〉 is a mean-squared angular amplitude of the motion and τc is the correlation time lying in the sub- and nanosecond time ranges. In this work, the ESE technique was applied to spin-labeled amphiphilic molecules of three different kinds embedded in bilayers of fully saturated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and mono-unsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipids. Two-pulse ESE data revealed the appearance of stochastic librations above 130 K, with the parameter 〈α2〉τc obeying the Arrhenius type of temperature dependence and increasing remarkably above 170–180 K. A comparison with a dry sample suggests that onset of motions is not related with lipid internal motions. Three-pulse ESE experiments (resulting in stimulated echos) in DPPC bilayers showed the appearance of slow molecular rotations above 170–180 K. For D2O-hydrated bilayers, ESE envelope modulation experiments indicate that isotropic water molecular motions in the nearest hydration shell of the bilayer appear with a rate of ~ 105 s−1 in the narrow temperature range between 175 and 179 K. The similarity of the experimental data found for three different spin-labeled compounds suggests a cooperative character for the ESE-detected molecular motions. The data were interpreted within a model suggesting that dynamical transition is related with overcoming barriers, of 10–20 kJ/mol height, existing in the system for the molecular reorientations.

AB - Data on neutron scattering in biological systems show low-temperature dynamical transition between 170 and 230 K manifesting itself as a drastic increase of the atomic mean-squared displacement, 〈x2〉, detected for hydrogen atoms in the nano- to picosecond time scale. For spin-labeled systems, electron spin echo (ESE) spectroscopy—a pulsed version of electron paramagnetic resonance—is also capable of detection of dynamical transition. A two-pulse ESE decay in frozen matrixes is induced by spin relaxation arising from stochastic molecular librations, and allows to obtain the 〈α2〉τc parameter, where 〈α2〉 is a mean-squared angular amplitude of the motion and τc is the correlation time lying in the sub- and nanosecond time ranges. In this work, the ESE technique was applied to spin-labeled amphiphilic molecules of three different kinds embedded in bilayers of fully saturated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and mono-unsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipids. Two-pulse ESE data revealed the appearance of stochastic librations above 130 K, with the parameter 〈α2〉τc obeying the Arrhenius type of temperature dependence and increasing remarkably above 170–180 K. A comparison with a dry sample suggests that onset of motions is not related with lipid internal motions. Three-pulse ESE experiments (resulting in stimulated echos) in DPPC bilayers showed the appearance of slow molecular rotations above 170–180 K. For D2O-hydrated bilayers, ESE envelope modulation experiments indicate that isotropic water molecular motions in the nearest hydration shell of the bilayer appear with a rate of ~ 105 s−1 in the narrow temperature range between 175 and 179 K. The similarity of the experimental data found for three different spin-labeled compounds suggests a cooperative character for the ESE-detected molecular motions. The data were interpreted within a model suggesting that dynamical transition is related with overcoming barriers, of 10–20 kJ/mol height, existing in the system for the molecular reorientations.

KW - NEUTRON-SCATTERING

KW - MOLECULAR MOTIONS

KW - PROTEIN DYNAMICS

KW - HYDRATION WATER

KW - ECHO

KW - RESONANCE

KW - GLASS

KW - EPR

KW - LIBRATIONS

KW - MEMBRANES

UR - http://www.scopus.com/inward/record.url?scp=85054611666&partnerID=8YFLogxK

U2 - 10.1007/s00723-018-1066-2

DO - 10.1007/s00723-018-1066-2

M3 - Article

AN - SCOPUS:85054611666

VL - 49

SP - 1369

EP - 1383

JO - Applied Magnetic Resonance

JF - Applied Magnetic Resonance

SN - 0937-9347

IS - 12

ER -