The article "Photoremovable Protecting Groups in Chemistry and Biology: Reaction Mechanisms and Efficacy" by Petr Klán et al. provides a comprehensive review of photoremovable protecting groups (PPGs) used in both organic synthesis and biological applications. PPGs are chemical moieties that can be released upon exposure to light, allowing for spatial and temporal control over the release of various chemicals such as bioagents, acids, bases, and inorganic species. The review covers the design criteria for effective PPGs, including strong absorption at wavelengths above 300 nm, high quantum yield for release, purity, stability, solubility, and biocompatibility. The article discusses several types of PPGs, including arylcarbonylmethyl groups, nitroaryl groups, coumarin-4-ylmethyl groups, and arylmethyl groups. Each section details the photophysical properties, reaction mechanisms, and applications of these groups. For example, phenacyl and related arylcarbonylmethyl groups are discussed in detail, including their photorelease mechanisms and the role of substituents on the chromophore. The article also explores the photochemistry of p-hydroxyphenacyl groups, which have emerged as a promising candidate due to their quantitative chemical yield and clean reaction products. The review highlights the importance of water in the photorelease process, particularly in the case of p-hydroxyphenacyl groups, where a photo-Favorskii rearrangement occurs. The article provides detailed kinetic and spectroscopic data, including the formation of transient species and the role of solvent effects. Additionally, it discusses the use of PPGs in various biological applications, such as enzyme catalysis and neurobiology, emphasizing their advantages in terms of efficiency, selectivity, and biocompatibility. Overall, the article serves as a valuable resource for researchers interested in the design, synthesis, and application of photoremovable protecting groups in both chemical and biological contexts.The article "Photoremovable Protecting Groups in Chemistry and Biology: Reaction Mechanisms and Efficacy" by Petr Klán et al. provides a comprehensive review of photoremovable protecting groups (PPGs) used in both organic synthesis and biological applications. PPGs are chemical moieties that can be released upon exposure to light, allowing for spatial and temporal control over the release of various chemicals such as bioagents, acids, bases, and inorganic species. The review covers the design criteria for effective PPGs, including strong absorption at wavelengths above 300 nm, high quantum yield for release, purity, stability, solubility, and biocompatibility. The article discusses several types of PPGs, including arylcarbonylmethyl groups, nitroaryl groups, coumarin-4-ylmethyl groups, and arylmethyl groups. Each section details the photophysical properties, reaction mechanisms, and applications of these groups. For example, phenacyl and related arylcarbonylmethyl groups are discussed in detail, including their photorelease mechanisms and the role of substituents on the chromophore. The article also explores the photochemistry of p-hydroxyphenacyl groups, which have emerged as a promising candidate due to their quantitative chemical yield and clean reaction products. The review highlights the importance of water in the photorelease process, particularly in the case of p-hydroxyphenacyl groups, where a photo-Favorskii rearrangement occurs. The article provides detailed kinetic and spectroscopic data, including the formation of transient species and the role of solvent effects. Additionally, it discusses the use of PPGs in various biological applications, such as enzyme catalysis and neurobiology, emphasizing their advantages in terms of efficiency, selectivity, and biocompatibility. Overall, the article serves as a valuable resource for researchers interested in the design, synthesis, and application of photoremovable protecting groups in both chemical and biological contexts.