Hemoglobin is the main protein of red blood cells that provides oxygen transport to all cells of the human body. The ability of hemoglobin to bind the main low-molecular-weight thiol of the cell glutathione, both covalently and noncovalently, is not only an important part of the antioxidant protection of red blood cells, but also affects its affinity for oxygen in both cases. In this study, the properties of oxyhemoglobin in complex with reduced glutathione (GSH) and properties of glutathionylated hemoglobin bound to glutathione via an SS bond were characterized. For this purpose, the methods of circular dichroism, Raman spectroscopy, infrared spectroscopy, tryptophan fluorescence, differential scanning fluorimetry, and molecular modeling were used. It was found that the glutathionylation of oxyhemoglobin caused changes in the secondary structure of the protein, reducing the alpha helicity, but did not affect the heme environment, tryptophan fluorescence, and the thermostability of the protein. In the noncovalent complex of oxyhemoglobin with reduced glutathione, the secondary structure of hemoglobin remained almost unchanged; however, changes in the heme environment and the microenvironment of tryptophans, as well as a decrease in the protein’s thermal stability, were observed. Thus, the formation of a noncovalent complex of hemoglobin with glutathione makes a more significant effect on the tertiary and quaternary structure of hemoglobin than glutathionylation, which mainly affects the secondary structure of the protein. The obtained data are important for understanding the functioning of glutathionylated hemoglobin, which is a marker of oxidative stress, and hemoglobin in complex with GSH, which appears to deposit GSH and release it during deoxygenation to increase the antioxidant protection of cells.

Cardiotonic steroids (CTS) are a group of steroid compounds derived from certain plants and animals. CTS are selective inhibitors of Na,K-ATPase, so for a long time they were widely used for medical purposes to treat heart failure and some other diseases. However, over time, doctors gradually began to refuse this group of drugs due to their narrow therapeutic range and a number of serious side effects. However, in parallel with the rise and fall of interest in CTS as a drug, interest in them as a single class of high-affinity Na,K-ATPase inhibitors has only increased. Numerous data on the effect of CTS on signaling cascades and cell viability made impelling a search for a rationale for the existence of such a subtle biological regulator. A large number of studies devoted to the potential use of CTS in the treatment of neurodegenerative, oncological, immune and other diseases "revitalized" the already "written off" group of the drugs. If initially the role of exogenous (mainly plant origin) CTS was studied, then by the 90s of the XX century the study of the role of endogenous CTS and their regulatory effects became a popular trend in biology and physiology. The role of endogenous CTS was studied in details in the pathogenesis of cardiovascular diseases [1]. A large number of researchers have unanimously stated that endogenous CTS are very complex regulators of the development of pathological processes; however, the exact cause-and-effect relationship that would unambiguously explain the processes of synthesis, utilization, and the role of endogenous CTS has not yet been established. The effects of CTS in the frame of various regulatory schemes have been described, but the predominant number of studies was devoted to arterial hypertension, heart and renal failure, cancer [2–4], aging [5,6], and neuroinflammation. The effects of both endo- and exogenous CTS on blood cells and have been studied to a much lesser extent.

This review highlights key advances in chemical biology reported in 2025, curated by students in the Advanced Chemical Biology course (Ch/Bi145) at the California Institute of Technology (Caltech). The selected studies span advances in bioconjugation and bioorthogonal chemistry, visualization and sensing, interaction profiling, precision control of biological systems, emerging therapeutic modalities, and synthetic chemical biology. Together, they illustrate how innovative molecular design continues to expand our ability to interrogate and manipulate biological systems.