Photophysics of Molecular Probes for Amyloid-ß Detection: Computational Insights into the Roles of Probe Linker and Functional Groups.

In this computational study, density functional theory (DFT) and time-dependent DFT methods (TD-DFT) were employed to study the optical properties of six families of molecules with donor (D), bridge (B), and acceptor (A) fragments that have potential for use as fluorescent molecular probes for the early detection of Alzheimer's disease. After validating our computational method against experimental data, using X-ray and absorption data, the equilibrium geometries and wave functions of the ground and first singlet excited states were systematically studied. Our simulations demonstrate that the S1 states of these rod-like D-B-A fluorescent probes are twisted intramolecular charge transfer states with a predominant highest occupied molecular orbital-least unoccupied molecular orbital (HOMO-LUMO) character, the former localized primarily at the donor, whereas the latter at the acceptor site. Moreover, the influence of the bridge, donor, and acceptor fragments on molecules' absorption energies is explored, highlighting the influence of double and triple bonds and some specific modifications on the acceptor side, including the addition of electronegative atoms, pyranone derivatives, and their functionalization. By having the absorption energies of 324 probes in hand, machine learning models were trained to predict the absorption energies of molecules. The models were found to be predictive, which suggests a potential that predictive models for other crucial properties, such as emission and quantum yield, can also be trained if suitable training data sets are made available.

Burrowing bug pigmentation.

Cydnidae bug (also termed the burrowing bug) are arthropods of the order Hemiptera, that are recognized by their morphological adaptations for digging. They release an odorous substance from special glands that serve as self-defense, causing pigmented macules when in contact with human skin, especially during the rainy season. Knowledge of this rarely described condition can help avoid unnecessary investigation(s).

Behind the scenes of spin-forbidden decay pathways in transition metal complexes.

The interpretation of the ultrafast photophysics of transition metal complexes following photo-absorption is quite involved as the heavy metal center leads to a complicated and entangled singlet-triplet manifold. This opens up multiple pathways for deactivation, often with competitive rates. As a result, intersystem crossing (ISC) and phosphorescence are commonly observed in transition metal complexes. A detailed understanding of such an excited-state structure and dynamics calls for state-of-the-art experimental and theoretical methodologies. In this review, we delve into the inability of non-relativistic quantum theory to describe spin-forbidden transitions, which can be overcome by taking into account spin-orbit coupling, whose importance grows with increasing atomic number. We present the quantum chemical theory of phosphorescence and ISC together with illustrative examples. Finally, a few applications are highlighted, bridging the gap between theoretical studies and experimental applications, such as photofunctional materials.

Symmetric blaschkoid pityriasis rosea in a child.

Pityriasis rosea (PR) is a common papulosquamous disorder that may be related to primary infection or endogenous reactivation of human herpesvirus 7 and 6. Based on morphology, distribution, and size of lesions, several atypical variants of PR have been described. PR following the lines of Blaschko represents an atypical variant that has seldom been described in the literature. Here, we describe a child with diabetes who developed PR in a symmetrical, blaschkolinear configuration.

Blaschkoid lichen planus occurring in childhood systemic lupus erythematosus.

Lupus erythematosus-lichen planus (LE-LP) overlap syndrome represents a rare disorder with clinical and histopathological features of both lichen planus and lupus erythematosus presenting in the same lesions. However, lichen planus and lupus erythematosus can also coexist in the same patient. Blaschkoid lichen planus in the setting of concurrent childhood-onset systemic lupus erythematosus has not been previously described.