Revealing protonation states and tracking substrate in serine hydroxymethyltransferase with room-temperature X-ray and neutron crystallography.

Pyridoxal 5'-phosphate (PLP)-dependent enzymes utilize a vitamin B-derived cofactor to perform a myriad of chemical transformations on amino acids and other small molecules. Some PLP-dependent enzymes, such as serine hydroxymethyltransferase (SHMT), are promising drug targets for the design of small-molecule antimicrobials and anticancer therapeutics, while others have been used to synthesize pharmaceutical building blocks. Understanding PLP-dependent catalysis and the reaction specificity is crucial to advance structure-assisted drug design and enzyme engineering.

Thienylpiperidine Donor NIR Xanthene-Based Dye for Photoacoustic Imaging.

Few xanthene-based near-infrared (NIR) photoacoustic (PA) dyes with absorbance >800 nm exist. As accessibility to these dyes requires long and tedious synthetic steps, we designed a NIR dye () with thienylpiperidine donors and a xanthene acceptor that is accessible in 3-4 synthetic steps. The dye boasts a strong PA signal at 880 nm with good biological compatibility and photostability, yields multiplexed imaging with an aza-BODIPY reference dye, and is detected at a depth of 4 cm.