The role of motivation on physical activity and screen time behaviors among parent-adolescent dyads: The FLASHE study.

Behavioral theories inform the development of lifestyle interventions to address low participation in physical activity (PA); however, relatively little is known about the value of self-determination theory (SDT) for explaining screen time (ST) behaviors or in extending SDT into a dyadic context. Actor-partner (i.e., parent-adolescent) interdependence models (APIMs) allow for examination of these interpersonal relationships. The purpose of this study was to examine PA and ST among parent-adolescent dyads using the cross-sectional Family Life, Activity, Sun, Health, and Eating (FLASHE) Study. Parent-adolescent dyads provided responses to online surveys addressing PA (n = 1177 dyads) and ST (n = 1489 dyads) behaviors. We examined the influence of SDT-based constructs (perceived competence and motivation) on PA and ST behaviors. Structural equations were used to estimate APIMs in STATA 15.1. Full models provided a good fit to the data. For both PA and ST, perceived competence was more strongly associated with motivation among adolescents compared with parents (PA: ß = 0.72 vs. 0.58, ST: ß = 0.34 vs. 0.22, p's < 0.001). Parental motivation was associated with parental PA and both adolescent motivation for PA and ST (p's < 0.001). Parental motivation was not associated with adolescent ST-behavior. Adolescent motivation was only associated with parent motivation for PA. In the FLASHE study, SDT constructs extend acceptably to the dyadic setting, with PA models providing a slightly better fit to the data than ST models. Longitudinal studies that target perceived competence and the self-regulation of motivation in parents and their adolescents are a next logical step to understanding both PA and ST behaviors.

Loss of PRP4K drives anoikis resistance in part by dysregulation of epidermal growth factor receptor endosomal trafficking.

Anoikis acts as a critical barrier to metastasis by inducing cell death upon cancer cell detachment from the extracellular matrix (ECM), thereby preventing tumor cell dissemination to secondary sites. The induction of anoikis requires the lysosomal-mediated downregulation of epidermal growth factor receptors (EGFRs) leading to termination of pro-survival signaling. In this study, we demonstrate that depletion of pre-mRNA splicing factor 4 kinase (PRP4K; also known as PRPF4B) causes dysregulation of EGFR trafficking and anoikis resistance. We also report a novel cytoplasmic localization of PRP4K at the late endosome, and demonstrate both nuclear and cytoplasmic localization in breast, lung and ovarian cancer tissue. Mechanistically, depletion of PRP4K leads to reduced EGFR degradation following cell detachment from the ECM and correlates with increased TrkB, vimentin and Zeb1 expression. As a result, PRP4K loss promotes sustained growth factor signaling and increased cellular resistance to anoikis in vitro and in a novel zebrafish xenotransplantation model of anoikis sensitivity, as well as increased metastasis in a mouse model of ovarian cancer. Thus, PRP4K may serve as a potential biomarker of anoikis sensitivity in ovarian and other epithelial cancers.

Electron transfer at the class II/III borderline of mixed valency: dependence of rates on solvent dynamics and observation of a localized-to-delocalized transition in freezing solvents.

The dependence of the rates of intramolecular electron transfer (ET) of mixed-valence complexes of the type {[Ru3O(OAc)6(CO)(L)]2-BL}-1, where L is the pyridyl ligand and BL is the pyrazine on solvent type and temperature is described. Complexes were reduced chemically to obtain the mixed-valence anions in acetonitrile (CH3CN) and methylene chloride (CH2Cl2). Rate constants for intramolecular ET were estimated by simulating the observed degree of nu(CO) infrared (IR) bandshape coalescence in the mixed-valence state. In the strongly coupled mixed-valence states of these complexes, the electronic coupling, HAB, approaches lambda/2, where lambda is the total reorganization energy. The activation energy is thus nearly zero, and rate constants are in the 'ultrafast' regime where they depend on the pre-exponential terms within the frequency factor, nuN. The frequency factor contains both external (solvent dynamics) and internal (molecular vibrations) contributions. In general, external solvent motions are slower than internal vibrations, and therefore control ET rates in fluid solution. A profound increase in the degree of nu(CO) IR bandshape coalescence is observed as the temperature approaches the freezing points of the solvents methylene chloride (f.p. -92 degrees C) and acetonitrile (f.p. -44 degrees C). Decoupling the slower solvent motions involved in the frequency factor nuN for ET by freezing the solvent causes a transition from solvent dynamics to internal vibration-limited rates. The solvent phase transition causes a localized-to-delocalized transition in the mixed-valence ions that accelerates the rate of ET.

Solvent dynamical control of ultrafast ground state electron transfer: implications for Class II-III mixed valency.

We relate the solvent and temperature dependence of the rates of intramolecular electron transfer (ET) of mixed valence complexes of the type {[Ru3O(OAc)6(CO)(L)]2-BL}-1, where L = pyridyl ligand and BL = pyrazine. Complexes were reduced chemically or electrochemically to obtain the mixed valence anions in seven solvents: acetonitrile, methylene chloride, dimethylformamide, tetrahydrofuran, dimethylsulfoxide, chloroform, and hexamethylphosphoramide. Rate constants for intramolecular ET were estimated by simulating the observed degree of nu(CO) IR band shape coalescence in the mixed valence state. Correlations between rate constants for ET and solvent properties including static dielectric constant, optical dielectric constant, the quantity 1/epsilonop - 1/epsilonS, microscopic solvent polarity, viscosity, cardinal rotational moments of inertia, and solvent relaxation times were examined. In the temperature study, the complexes displayed a sharp increase in the ket as the freezing points of the solvents methylene chloride and acetonitrile were approached. The solvent phase transition causes a localized-to-delocalized transition in the mixed valence ions and an acceleration in the rate of ET. This is explained in terms of decoupling the slower solvent motions involved in the frequency factor nuN which increases the value of nuN. The observed solvent and temperature dependence of the ket for these complexes is used in order to formulate a new definition for Robin-Day class II-III mixed valence compounds. Specifically, it is proposed that class II-III compounds are those for which thermodynamic properties of the solvent exert no control over ket, but the dynamic properties of the solvent still influence ket.

Tuning the electronic communication and rates of intramolecular electron transfer of dimers of trinuclear ruthenium clusters: bridging and ancillary ligand effects.

Ten new bridged dimers of oxo-centered triruthenium clusters with CO and 4-(dimethylamino)pyridine (dmap), pyridine (py), or 4-cyanopyridine (cpy) as terminal ligands and pyrazine-d(4) (d(4)-pz), 2,5-dimethylpyrazine (dmpz), 2-methylpyrazine (mpz), and 2-chloropyrazine (clpz) as bridging ligands were prepared. The carbonyl stretching frequency, nu(CO), was used as a probe for infrared spectroelectrochemical measurements. In the neutral and doubly reduced states, a single band was observed for each of the dimers, with a shift in frequency due to the oxidation state of the triruthenium clusters. In the singly reduced state, a range of nu(CO) line shapes was observed, depending on the nature of the ligands, from two bands centered at the frequencies of the bands of the neutral and doubly reduced species to one broad band at the average of these two frequencies. By synthesizing new combinations of bridging and ancillary ligands, electronic communication between two bridged triruthenium clusters was effectively tuned, and electron-transfer rates were estimated by IR spectral line-shape analysis. In dimers bridged by the asymmetric ligand mpz, it was possible through selective isotope labeling of one CO ligand to observe "mixed-valence isomers," the two alternate charge distributions of a mixed-valence complex.

Intervalence-resonant Raman spectroscopy of strongly coupled mixed-valence cluster dimers of ruthenium.

Resonance Raman spectroelectrochemistry (RR-SEC) at -20 degrees C has been performed on the pyrazine-bridged dimer of mu-oxo-centered trinuclear ruthenium-acetate "clusters"--[(dmap)(CO)(mu-OAc)6(mu3-O)Ru3(mu-L(b))Ru3(mu3-O)(mu-OAc)6(CO)(dmap)]n (where dmap = 4-(dimethylamino)pyridine and L(b) = pyrazine-h4 and pyrazine-d4)-in three oxidation states: n = 0, -1, and -2. In the one-electron reduced, "mixed-valent" state (overall -1 charge and a single odd electron; formal oxidation states [II, II, III]-[III, III, II] on the metal centers), the Raman excitation at 800 nm is resonant with a cluster-to-cluster intervalence charge-transfer (IVCT) band. Under these conditions, scattering enhancement is observed for all four totally symmetric vibrational modes of the bridging pyrazine ligand (nu8a, nu9a, nu1, and nu6a) in the investigated spectral range (100-2000 cm(-1)), and there is no evidence of activity in non-totally symmetric vibrations. Resonantly enhanced Raman peaks related to peripheral pyridyl (dmap) ligand modes and low-frequency features arising from the trigonal Ru3O cluster core and the cluster[Ru]-[N]ligand vibrations were also observed in the spectra of the intermediate-valence (n = -1) cluster dimer. The vibrational assignments and interpretations proposed in this work were reinforced by observation of characteristic isotopic frequency shifts accompanying deuteration of the bridging pyrazine. The results reveal that the fully symmetric (A(g)) vibrational motions of the organic bridge are coupled to the nominally metal cluster-to-metal cluster fast intramolecular electron transfer (ET) and provide validation of the near-delocalized description according to a predicted three-site/three-state (e.g., metal-bridge-metal) vibronic coupling model, in which the important role of the bridging ligand in mediating electronic communication and delocalization between charge centers is explicitly considered. Further compelling evidence supporting an extended five-state model, which incorporates the peripheral cluster-bound pyridyl ligands, is also presented.

Mixed valence isomers.

The infrared spectroscopic observation of mixed valence isomers, the two alternate charge distributions of a mixed valence complex, is reported. Asymmetry induced by the 2-methylpyrazine bridging ligand was used to energetically differentiate the two states, and isotopic labeling of CO was used to spectroscopically observe the two states. Infrared line shape analysis was used to determine rate constants for electron transfer of 6.5 x 1011 s-1 and equilibrium constants of 2.2 for the mixed valence isomers.

Infrared activity of symmetric bridging ligand modes in pyrazine-bridged hexaruthenium mixed-valence clusters.

A fully symmetric (A(g)) vibrational mode of pyrazine is observed in the infrared spectrum of four pyrazine-bridged hexaruthenium mixed-valence complexes with varying degrees of electronic coupling between clusters. Deuteration of the bridging pyrazine ligand and the accompanying shift in frequency confirm the assignment of this mode. Previous observation of infrared line coalescence in the carbonyl stretching region assigns all of these complexes to Robin-Day class II (partial localization of charge) on the picosecond time scale. The infrared activity of the fully symmetric bridging ligand mode could provide a complementary assignment of these complexes to class II on a faster, femtosecond time scale. However, the extinction coefficient for this band is much greater than that observed in similar asymmetric, non-mixed-valence complexes and suggests that its strong IR activity is due to vibronic enhancement rather than electronic asymmetry.

Solvent dynamical control of electron-transfer rates in mixed-valence complexes observed by infrared spectral line shape coalescence.

Rate constants for intramolecular electron transfer within the intervalence charge transfer (-1) states of the complexes [{Ru3O(OAc)6(L)(CO)}2(mu-pz)] (where L= 4-(dimethylamino)pyridine (1), pyridine (2), 3-cyanopyridine (3), or 4-cyanopyridine (4) and pz = pyrazine) were determined by coalescence of infrared (IR) vibrational spectral line shapes in seven solvents. The electron-transfer times (kET-1) show a strong correlation with solvent relaxation times determined in separate ultrafast time-resolved fluorescence experiments. The best comparison is found with the parameter t1e, which is ascribed to inertial solvent relaxation. The IR spectra of these mixed-valence complexes are thus a steady-state spectral probe of ultrafast, dynamic solvent relaxation processes which are otherwise only accessible using laser-pumped, ultrafast time-resolved measurements.