Rapid PROTAC Discovery Platform: Nanomole-Scale Array Synthesis and Direct Screening of Reaction Mixtures

Precise length, shape, and linker attachment points are all integral components to designing efficacious proteolysis targeting chimeras (PROTACs). Due to the synthetic complexity of these heterobifunctional degraders and the difficulty of computational modeling to aid PROTAC design, the exploration of structure-activity relationships remains mostly empirical, which requires a significant investment of time and resources. To facilitate rapid hit finding, we developed capabilities for PROTAC parallel synthesis and purification by harnessing an array of preformed E3-ligand-linker intermediates. In the next iteration of this approach, we developed a rapid, nanomole-scale PROTAC synthesis methodology using amide coupling that enables direct screening of nonpurified reaction mixtures in cell-based degradation assays, as well as logD and EPSA measurements. This approach greatly expands and accelerates PROTAC SAR exploration (5 days instead of several weeks) as well as avoids laborious and solvent-demanding purification of the reaction mixtures, thus making it an economical and more sustainable methodology for PROTAC hit finding.

Pain relief in the elderly: are we doing enough?

Focal points

The recruitment times and firing patterns of the medullary respiratory neurones of the cat

The brainstem of anaesthetized cats was explored for respiratory neurones with microelectrodes in the regions of the nucleus retroambigualis (ventrolateral region) and the nucleus tractus solitarius (dorsomedial region). These neurones were analysed with respect to their firing patterns and recruitment times, as referenced to the respiratory cycle. All of the respiratory neurones showed a stable and ordered pattern of firing. Four groups of neurones with similar characteristics within each group, but differing from each other, were statistically examined; the inspiratory neurones of the dorsomedial region, the 'late' inspiratory neurones of the ventrolateral region, the 'early' inspiratory neurones of the ventrolateral region and the expiratory neurones of the ventrolateral region.

Primary structure of wheat germ phenylalanine transfer RNA

The complete nucleotide sequence of wheat germ phenylalanine transfer RNA (tRNA(Phe)) is presented. This RNA, which is an acceptable substrate for yeast phenylalanine tRNA synthetase, has a structure very similar to that of yeast tRNA(Phe). Only 16 of the 76 nucleotides are different, and all but two of the nucleotide changes are located in regions that are doublestranded in the cloverleaf model. The two changes in single-stranded regions involve minor modifications of the same nucleotide. The dihydrouridine loop and its supporting stem are completely free of nucleotide changes.