A Turn-On Fluorescent Amino Acid Sensor Reveals Chloroquine's Effect on Cellular Amino Acids via Inhibiting Cathepsin L

Chemical and linguistic considerations for encoding Chinese characters: an embodiment using chain-end degradable sequence-defined oligourethanes created by consecutive solid phase click chemistry

Sequence-defined polymers (SDPs) are currently being investigated for use as information storage media. As the number of monomers in the SDPs increases, with a corresponding increase in mathematical base, the use of tandem-MS for de novo sequencing becomes more challenging. In contrast, chain-end degradation routines are truly de novo, potentially allowing very large mathematical bases for encoding. While alphabetic scripts have a few dozen symbols, logographic scripts, such as Chinese, can have several thousand symbols. Using a new in situ consecutive click reaction approach on an oligourethane backbone for writing, and a previously reported chain-end degradation routine for reading, we encoded/decoded a confucius proverb written in Chinese characters using two encoding schemes: Unicode and Zhèng Mă. Unicode is an internationally standardized arbitrary string of hexadecimal (base-16) symbols which efficiently encodes uniquely identifiable symbols but requires complete fidelity of transmission, or context-based inferential strategies to be interpreted. The Zhèng Mă approach encodes with a base-26 system using the visual characteristics and internal composition of Chinese characters themselves, which leads to greater ambiguity of encoded strings, but more robust retrievability of information from partial or corrupted encodings. The application of information-encoded oligourethanes to two different encoding systems allowed us to establish their flexibility and versatility for data storage. We found the oligourethanes immensely adaptable to both encoding schemes for Chinese characters, and we highlight the expected tradeoff between the efficiency and uniqueness of Unicode encoding on the one hand, and the fidelity to a scripts' particular visual characteristics on the other.

Synthesis of a Near-Infrared Fluorescent Probe for Imaging Catecholamines via a Tandem Nucleophilic Aromatic Substitution

A near-infrared (NIR) fluorescent probe NS667 was developed using a novel synthetic strategy by integrating an electron-rich 1,2,3,4-tetrahydroquinoxaline (THQ) into the scaffold from NS510, which binds to catecholamines with high affinity. The fluorophore core was constructed with a tandem nucleophilic aromatic substitution. Upon binding to catecholamines, the fluorescence of this probe shifted, with the emission in the NIR region. Live cell imaging results demonstrate that NS667 can effectively image norepinephrine in chromaffin cells with shifted fluorescence, which highlights the potential of the probe for neuroimaging in tissues.

Colorimetric Sensor Based on the Oxidase-Mimic Supramolecular Catalyst for Selective and Sensitive Biomolecular Detection

We have engineered a colorimetric sensor capable of selective and sensitive detection of amino acids. This sensor employs a supramolecular copper-dependent oxidase mimic as the probe, stemming from our prior research. The oxidase mimic is constructed through the self-assembly of commercially available guanosine monophosphate (GMP), Fmoc-lysine, and Cu2+. It catalyzes the formation of a red product with a maximum absorbance at 510 nm. The changes in color and absorbance are responsive to both the concentrations and types of amino acids present. This effect is most pronounced in the presence of histidine, with a detection limit (LOD) of 6.4 nM. Furthermore, the catalytic probe can distinguish histidine from histamine and imidazole propionate, as well as 1-methyl-histidine from 3-methyl-histidine, based on their distinct coordination capacities with copper. This underscores the high selectivity of the sensing platform. Both theoretical simulations and experimental results (including UV-vis spectra, fluorescence, and EPR) indicate that the amino acids may engage in copper center coordination, thereby impeding O2 access to copper─a pivotal aspect of the oxidase catalysis. This sensing platform, characteristic of its swift response, simple fabrication, and exceptional sensitivity and selectivity, can also be applied to detect other biological analytes such as nucleotides. It holds potential for use in environmental and biochemical analyses.