An Element-Substituted Cyclobutadiene Exhibiting High-Energy Blue Phosphorescence.

1,3,2,4-Diazadiboretidine, an isoelectronic heteroanalogue of cyclobutadiene, is an interesting chemical species in terms of comparison with the carbon system, whereas its properties have never been investigated experimentally. According to Baird's rule, Hückel antiaromatic cyclobutadiene acquires aromaticity in the lowest triplet state. Here we report experimental and theoretical studies on the ground- and excited-state antiaromaticity/aromaticity as well as the photophysical properties of an isolable 1,3,2,4-diazadiboretidine derivative. The crystal structure of the diazadiboretidine derivative revealed that the B2 N2 ring adopts a planar rhombic geometry in the ground state. Yet, theoretical calculations showed that the B2 N2 ring turns to a square geometry with a nonaromatic character in the lowest triplet state. Notably, the diazadiboretidine derivative has the lowest singlet and triplet states lying at close energy levels and displays blue phosphorescence.

SCML2 promotes heterochromatin organization in late spermatogenesis.

Spermatogenesis involves the progressive reorganization of heterochromatin. However, the mechanisms that underlie the dynamic remodeling of heterochromatin remain unknown. Here, we identify SCML2, a germline-specific Polycomb protein, as a critical regulator of heterochromatin organization in spermatogenesis. We show that SCML2 accumulates on pericentromeric heterochromatin (PCH) in male germ cells, where it suppresses PRC1-mediated monoubiquitylation of histone H2A at Lysine 119 (H2AK119ub) and promotes deposition of PRC2-mediated H3K27me3 during meiosis. In postmeiotic spermatids, SCML2 is required for heterochromatin organization, and the loss of SCML2 leads to the formation of ectopic patches of facultative heterochromatin. Our data suggest that, in the absence of SCML2, the ectopic expression of somatic lamins drives this process. Furthermore, the centromere protein CENP-V is a specific marker of PCH in postmeiotic spermatids, and SCML2 is required for CENP-V localization on PCH. Given the essential functions of PRC1 and PRC2 for genome-wide gene expression in spermatogenesis, our data suggest that heterochromatin organization and spermatogenesis-specific gene expression are functionally linked. We propose that SCML2 coordinates the organization of heterochromatin and gene expression through the regulation of Polycomb complexes.

A cable driven robotic palpation system with contact force sensing based on cable tension observation.

BACKGROUND: Prostate Cancer screening based on manual palpation is subjective. Robotic palpation systems can objectively acquire stiffness conditions of the prostate. METHODS: A 2DoF cable driven robotic system for prostate palpation is proposed. An indirect method to estimate the contact force based on cable tension observation is presented. Kinematic models and a joint angle estimation method to determine the tip position of the probe are derived. Positioning accuracy was verified using an optical marker tracking system and by displacement measurement, respectively. The contact force estimation method was validated on silicone phantom samples. RESULTS: A good consistence between the estimated and measured contact force was observed. The contact force was correlated with the elastic modulus of each silicone phantom. There was also a good agreement between the theoretical and the measured tip position. CONCLUSION: In the proposed palpation system, the indirect contact force estimation method is viable and holds potential for the stiffness assessment of the prostate. The tip position vital for palpation can be determined through estimated joint angles.