Photoisomers of Azobenzene Star with a Flat Core: Theoretical Insights into Multiple States from DFT and MD Perspective

This study focuses on comparing physical properties of photoisomers of an azobenzene star with benzene-1,3,5-tricarboxamide core. Three azobenzene arms of the molecule undergo a reversible trans–cis isomerization upon UV–vis light illumination giving rise to multiple states from the planar all-trans one, via two mixed states to the kinked all-cis isomer. Employing density functional theory, we characterize the structural and photophysical properties of each state indicating a role the planar core plays in the coupling between azobenzene chromophores. To characterize the light-triggered switching of solvophilicity/solvophobicity of the star, the difference in solvation free energy is calculated for the transfer of an azobenzene star from its gas phase to implicit or explicit solvents. For the latter case, classical all-atom molecular dynamics simulations of aqueous solutions of azobenzene star are performed employing the polymer consistent force field to shed light on the thermodynamics of explicit hydration as a function of the isomerization state and on the structuring of water around the star. From the analysis of two contributions to the free energy of hydration, the nonpolar van der Waals and the electrostatic terms, it is concluded that isomerization specificity largely determines the polarity of the molecule and the solute–solvent electrostatic interactions. This convertible hydrophilicity/hydrophobicity together with readjustable occupied volume and the surface area accessible to water, affects the self-assembly/disassembly of the azobenzene star with a flat core triggered by light

Linear mixed model with full day absolute duration of arm inclination exposure (minutes) and shoulder pain^*.

<p>Linear mixed model with full day absolute duration of arm inclination exposure (minutes) and shoulder pain^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188372#t007fn008" target="_blank">*</a>}.</p

Association of objectively measured arm inclination with shoulder pain: A 6-month follow-up prospective study of construction and health care workers

<div><p>Objectives</p><p>The aim was to determine the association of occupational arm inclination with shoulder pain in construction and health care workers.</p><p>Methods</p><p>Arm inclination relative to the vertical was measured with an accelerometer placed on the dominant upper arm for up to four full days at baseline in 62 construction workers and 63 health care workers. The pain intensity in the shoulder and mechanical and psychosocial work factors were measured by self-reports at baseline and prospectively after 6 months. The associations between exposures and shoulder pain were analyzed with multilevel mixed-effects linear regressions.</p><p>Results</p><p>For the total study population working with the dominant arm at inclinations > 30° and >120° was associated with lower levels of shoulder pain both cross-sectionally and after 6 months. Associations were attenuated when adjusting for individual and social factors, psychological state, and exposure during leisure time, especially for the high inclination levels. Analyses, only including subjects with no pain at baseline revealed no significant associations. While stratified analysis showed negative associations in the construction worker group, there were no significant association in health care workers. Compared to the number of hypotheses tested, the number of significant findings was low. Adjustment by Bonferroni-correction made almost all findings insignificant.</p><p>Conclusions</p><p>All analyses reflected a negative association between arm inclination and shoulder pain, but few analyses showed these associations to be statistically significant. If there is a relationship between arm inclination and shoulder pain, these findings could indicate that pain-avoidance may modify how workers perform their tasks.</p></div

Linear mixed model with absolute duration of arm inclination exposure (minutes) and shoulder pain^*.

<p>Linear mixed model with absolute duration of arm inclination exposure (minutes) and shoulder pain^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188372#t005fn008" target="_blank">*</a>}.</p

Estimated splines for the effect of arm inclination >120° on shoulder pain.

<p>A: Total group at baseline. B: Total group at 6 months. C: Construction work at baseline. D: Construction work at 6 months. E: Health care work at baseline. F: Health care work at 6 months. Black solid lines represent the estimated splines for arm inclination effects on pain levels from GAM models, and the black dashed lines represent 95% confidence bands.</p

Descriptive statistics of the study population.

<p>Descriptive statistics of the study population.</p

Linear mixed model with full day arm-inclination exposure (percentage of 24 hours) and shoulder pain^*.

<p>Linear mixed model with full day arm-inclination exposure (percentage of 24 hours) and shoulder pain^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188372#t006fn008" target="_blank">*</a>}.</p

Linear regression models with arm-inclination exposure at work [% of total time at work] and shoulder pain (excluded participants reporting pain at baseline).

<p>Linear regression models with arm-inclination exposure at work [% of total time at work] and shoulder pain (excluded participants reporting pain at baseline).</p

Estimated splines for the effect of arm inclination >30° on shoulder pain.

<p>A: Total group at baseline. B: Total group at 6 months. C: Construction work at baseline. D: Construction work at 6 months. E: Health care work at baseline. F: Health care work at 6 months. The black solid lines represent the estimated splines for arm inclination effects on pain levels from GAM models, and the black dashed lines represent 95% confidence bands.</p

Linear mixed model with arm inclination exposure at work [% of total time at work] and shoulder pain: stratified analyses for construction and health care work^*.

<p>Linear mixed model with arm inclination exposure at work [% of total time at work] and shoulder pain: stratified analyses for construction and health care work^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188372#t004fn008" target="_blank">*</a>}.</p