The spectral properties of protonated water clusters, especially the difference between Eigen (H3O+) and Zundel (H5O2+) conformers and the difference between their unhydrated and dominant hydrated forms are investigated with the first principles molecular dynamics simulations as well as with the high level ab initio calculations. The vibrational modes of the excess proton in H3O+ are sensitive to the hydration, while those in H5O2+ are sensitive to the messenger atom such as Ar (which was assumed to be weakly bound to the water cluster during acquisitions of experimental spectra). The spectral feature around approximately 2700 cm-1 (experimental value: 2665 cm-1) for the Eigen moiety appears when H3O+ is hydrated. This feature corresponds to the hydrating water interacting with H3O+, so it cannot appear in the Eigen core. Thus, H3O+ alone would be somewhat different from the Eigen forms in water. For the Zundel form (in particular, H5O2+), there have been some differences in spectral features among different experiments as well as between experiments and theory. When an Ar messenger atom is introduced at a specific temperature corresponding to the experimental condition, the calculated vibrational spectra for H5O2+.Ar are in good agreement with the experimental infrared spectra showing the characteristic Zundel frequency at approximately 1770 cm-1. Thus, the effect of hydration, messenger atom Ar, and temperature are crucial to elucidating the nature of vibrational spectra of Eigen and Zundel forms and to assigning the vibrational modes of small protonated water clusters.

The acceleration of electron transfer (ET) rates in redox proteins relative to aqueous solutes can be attributed to the protein's ability to reduce the nuclear response or reorganization upon ET, while maintaining sufficiently high electronic coupling. Quantitative predictions of reorganization free energy remain a challenge, both experimentally and computationally. Using density functional calculations and molecular dynamics simulation with an electronically polarizable force field, we report reorganization free energies for intraprotein ET in four heme-containing ET proteins that differ in their protein fold, hydrophilicity, and solvent accessibility of the electron-accepting group. The reorganization free energies for ET from the heme cofactors of cytochrome c and b(5) to solvent exposed Ru-complexes docked to histidine residues at the surface of these proteins fall within a narrow range of 1.2-1.3 eV. Reorganization free energy is significantly lowered in a designed 4-helix bundle protein where both redox active cofactors are protected from the solvent. For all ET reactions investigated, the major components of reorganization are the solvent and the protein, with the solvent contributing close to or more than 50% of the total. In three out of four proteins, the protein reorganization free energy can be viewed as a collective effect including many residues, each of which contributing a small fraction. These results have important implications for the design of artificial electron transport proteins. They suggest that reorganization free energy may in general not be effectively controlled by single point mutations, but to a large extent by the degree of solvent exposure of the ionizable cofactors.

It's a kinda magic! Contrary to conventional wisdom that OH bonds associated with dangling hydrogen atoms and those in the H3O+ ion in molecular clusters display characteristic peaks in IR spectra, a dynamic effect makes such peaks disappear, even in the gas phase at low temperatures. This finding helps solve the long‐standing problems of magic and antimagic protonated water clusters with 21 (top structures) and 22 (bottom structures) water molecules.

The objective of this study was to investigate how patterns of maternal depressive symptoms from mid-pregnancy to 3 years postpartum are associated with children's behavior at age 3 years and executive functions. Maternal depressive symptoms were measured from mid-pregnancy to 3 years postpartum. Growth mixture modeling was used on standardized maternal depression scores (n = 147) to identify trajectories. Children's behavioral problems and mental health symptomatology (internalizing, externalizing, and attention deficit hyperactivity disorder) were obtained at 3 and 6 years. EFs were assessed by a laboratory-based computerized task and maternal-report at 6 years. Multivariable linear regressions of children's outcomes against maternal depressive symptom trajectories were conducted (n = 103). Three distinct patterns of maternal depressive symptom trajectories were identified: low (n = 105), increasing (n = 27), and decreasing (n = 15). Children of mothers whose depressive symptoms increased reported more problem behaviors at 3 years and poorer EFs at 6 years as assessed by both instruments, but no significant differences in mental health symptomatology at 6 years, relative to those whose mothers had consistently low depressive symptoms. Children whose mothers became less depressed over time had comparable levels of behavioral problems at age 3, executive functions, and internalizing and externalizing scores at age 6; and fewer reported ADHD behaviors at age 6, than those whose mothers remained less depressed over time. If mothers' depressive symptoms improve over the first 3 years postpartum, their children's outlook may be comparable to those whose mothers had consistently low depressive symptoms.