Clock genes are expressed in cementum and regulate the proliferation and mineralization of cementoblasts.

Circadian clock genes are present in the ameloblasts, odontoblasts, and dental pulp cells. The cementum plays a vital role in connecting the roots of teeth to the alveolar bone by anchoring the periodontal ligament. The present study aimed at confirming the existence of clock genes and describing the potential regulatory effects of REV-ERBα in the cementum. The tooth-periodontal ligament-alveolar bone complexes of 6-week-old mice were analyzed using immunohistochemistry. OCCM-30 cells, an immortalized cementoblast cell line, were synchronized with dexamethasone. We used RT-PCR to detect the expression of clock genes in the absence or presence of SR8278, an effective antagonist of REV-ERBα. We performed a cell counting kit-8 (CCK-8) assay to determine the effect of SR8278 on cell proliferation. RT-PCR and Western blot were used to measure the expression of mineralization-related markers in mineralization-induced OCCM-30 cells, with or without SR8278 treatment. Finally, we used Alizarin red staining, and ALP staining and activity to further verify the effect of SR8278 on mineralization of OCCM-30 cells on macro-level. In our study, clock protein expression was confirmed in the murine cementum. Clock genes were shown to oscillate continuously in OCCM-30 cells. SR8278-induced inactivation of REV-ERBα inhibited the proliferation but promoted the mineralization of OCCM-30 cells. The present study confirmed the presence of clock genes in the cementum, where they potentially participate in cell proliferation and mineralization. Our findings may inspire new research directions for periodontal regeneration via clock gene manipulation.

Base-induced mechanistic variation in palladium-catalyzed carbonylation of aryl iodides.

A mechanism, which is distinct from the traditional one when sodium alkoxide was used instead of tertiary amines, was proposed for the alkoxycarbonylation of aryl iodides. The catalytic cycle was composed of oxidative addition, subsequent ArPdOR formation, CO insertion to Pd-OR, and final reductive elimination of ArPdCOOR. The kinetic simultaneity of the formation of deiodinated side product from the aryl iodide and aldehyde from corresponding alcohol provided strong evidence for the existence of ArPdOR species. The observation of thioether, as the other competitive product in palladium catalyzed thiocarbonylation of aryl iodides and sodium alkylthiolate, also indicate the possibility of metathesis between ArPdI and sodium alkylthiolate. Preliminary kinetic studies revealed that neither oxidative addition nor reductive elimination was rate limiting. DFT calculation displayed preference for CO insertion into Pd-OR bond. The advantage of this novel mechanism had been demonstrated in the facile alkoxycarbonylation and thiocarbonylation. The ethoxycarbonylation of aryl iodides under room temperature and balloon pressure of CO in the presence of EtONa were examined, and good to high yields were obtained; the t-butoxycarbonylation reactions in the presence of t-BuONa were achieved, and the alkylthiocarbonylation (including the t-butylthiocarbonylation) of aryl iodides in the presence of sodium alkylthiolate were also investigated.

Oxidative cross-coupling through double transmetallation: surprisingly high selectivity for palladium-catalyzed cross-coupling of alkylzinc and alkynylstannanes.

Two different organometallic reagents now can cross-couple together with the oxidative cross-coupling strategy. Palladium catalyzed oxidative cross-couplings of alkylzinc and alkynylstannane reagents using desyl chloride as the oxidant have been explored, which produce the desired Csp-Csp3 cross-coupling product in surprisingly high selectivity and yields. The current catalytic system tolerates the presence of beta-H, and the reactions using long chain alkyl zinc reagents gave the cross-coupling product in excellent yields and selectivities.