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1. Two-photon uncaging of bioactive thiols in live cells at wavelengths above 800 nm

   https://doi.org/10.1039/D0OB01986K  

   Hammers, Matthew D.; Hodny, Michael H.; Bader, Taysir K.; Mahmoodi, M. Mohsen; Fang, Sifei; Fenton, Alexander D.; Nurie, Kadiro; Trial, Hallie O.; Xu, Feng; Healy, Andrew T.; et al (March 2021, Organic & Biomolecular Chemistry)

   null (Ed.)

   Photoactivatable protecting groups (PPGs) are useful for a broad range of applications ranging from biology to materials science. In chemical biology, induction of biological processes via photoactivation is a powerful strategy for achieving spatiotemporal control. The importance of cysteine, glutathione, and other bioactive thiols in regulating protein structure/activity and cell redox homeostasis makes modulation of thiol activity particularly useful. One major objective for enhancing the utility of photoactivatable protecting groups (PPGs) in living systems is creating PPGs with longer wavelength absorption maxima and efficient two-photon (TP) absorption. Toward these objectives, we developed a carboxyl- and dimethylamine-functionalized nitrodibenzofuran PPG scaffold (cDMA-NDBF) for thiol photoactivation, which has a bathochromic shift in the one-photon absorption maximum from λ max = 315 nm with the unfunctionalized NDBF scaffold to λ max = 445 nm. While cDMA-NDBF-protected thiols are stable in the presence of UV irradiation, they undergo efficient broad-spectrum TP photolysis at wavelengths as long as 900 nm. To demonstrate the wavelength orthogonality of cDMA-NDBF and NDBF photolysis in a biological setting, caged farnesyltransferase enzyme inhibitors (FTI) were prepared and selectively photoactivated in live cells using 850–900 nm TP light for cDMA-NDBF-FTI and 300 nm UV light for NDBF-FTI. These experiments represent the first demonstration of thiol photoactivation at wavelengths above 800 nm. Consequently, cDMA-NDBF-caged thiols should have broad applicability in a wide range of experiments in chemical biology and materials science. 

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2. Control the Mechanical Properties and Degradation of Poly(Glycerol Sebacate) by Substitution of the Hydroxyl Groups with Palmitates

   https://doi.org/10.1002/mabi.202000101  

   Ding, Xiaochu; Chen, Ying; Chao, Corson Andrew; Wu, Yen‐Lin; Wang, Yadong (July 2020, Macromolecular Bioscience)

   Abstract Mechanical properties and degradation profile are important parameters for the applications of biodegradable polyester such as poly(glycerol sebacate) in biomedical engineering. Here, a strategy is reported to make palmitate functionalized poly(glycerol sebacate) (PPGS) to alter the polymer hydrophobicity, crystallinity, microstructures and thermal properties. The changes of these intrinsic properties impart tunable degradation profiles and mechanical properties to the resultant elastomers depending on the palmitate contents. When the palmitates reach up to 16 mol%, the elastic modulus is tuned from initially 838 ± 55 kPa for the PGS to 333 ± 21 kPa for the PPGS under the same crosslinking conditions. The elastomer undergoes reversible elastic deformations for at least 1000 cycles within 20% strain without failure and shows enhanced elasticity. The polymer degradation is simultaneously inhibited because of the increased hydrophobicity. This strategy is different with other PGS modifications which could form a softer elastomer with less crosslinks but typically lead to a quicker degradation. Because the materials are made from endogenous molecules, they possess good cytocompatibility similar to the PGS control. Although these materials are designed specifically for small arteries, it is expected that they will be useful for other soft tissues too. 

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3. Protocol for Palladium/N-Heterocyclic Carbene-Catalyzed Suzuki–Miyaura Cross-Coupling of Amides by N–C(O) Activation

   https://doi.org/10.1055/s-0040-1705956  

   Lei, Peng; Li, Guangchen; Ling, Yun; An, Jie; Nolan, Steven P.; Szostak, Michal (January 2021, Synthesis)

   null (Ed.)

   Abstract Amides are among the most important and ubiquitous functional groups in organic chemistry and process development. In this Practical Synthetic Procedure, a protocol for the Suzuki–Miyaura cross-coupling of amides by selective N–C(O) bond activation catalyzed by commercially available, air- and moisture-stable palladium/N-heterocyclic carbene (NHC) complexes is described. The procedure described involves [Pd(IPr)(cin)Cl] [IPr = 2,6-(diisopropylphenyl)imidazol-2-ylidene, cin = cinnamyl] at 0.10 mol% at room temperature and is performed on decagram scale. Furthermore, a procedure for the synthesis of amide starting materials is accomplished via selective N-tert-butoxycarbonylation, which is the preferred method over N-acylation. The present protocol carries advantages of operational simplicity, commercial availability of catalysts, and excellent conversions at low catalyst loadings. The method is generally useful for activation of N–C(O) amide bonds in a broad spectrum of amide precursors. The protocol should facilitate the implementation of amide cross-coupling reactions. 

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4. Synthetic feasibility of oxygen-driven photoisomerizations of alkenes and polyenes

   https://doi.org/10.1039/d0ob01993c  

   Turque, Oliver; Greer, Alexander; Wauchope, Orrette R. (November 2020, Organic & Biomolecular Chemistry)

   null (Ed.)

   This review describes O 2 -dependent photoreactions for possible routes to double-bond isomerizations. E , Z -isomerizations triggered by O 2 and visible light are a new area of potential synthetic interest. The reaction involves the reversible addition of O 2 to form a peroxy intermediate with oxygen evolution and partial regeneration of the compound as its isomer. Targeting of O 2 -dependent photoisomerizations also relates to a practical use of visible light, for example the improved light penetration depth for visible as opposed to UV photons in batch sensitized reactions. This review is intended to draw a link between visible-light formation of a peroxy intermediate and its dark degradation with O 2 release for unsaturated compound isomerization. This review should be of interest both to photochemists and synthetic organic chemists, as it ties together mechanistic and synthetic work, drawing attention to an overlooked subject. 

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5. Degradation of polyethylene glycols and polypropylene glycols in microcosms simulating a spill of produced water in shallow groundwater

   https://doi.org/10.1039/C8EM00291F  

   Rogers, Jessica D.; Thurman, E. Michael; Ferrer, Imma; Rosenblum, James S.; Evans, Morgan V.; Mouser, Paula J.; Ryan, Joseph N. (February 2019, Environmental Science: Processes & Impacts)

   Polyethylene glycols (PEGs) and polypropylene glycols (PPGs) are frequently used in hydraulic fracturing fluids and have been detected in water returning to the surface from hydraulically fractured oil and gas wells in multiple basins. We identified degradation pathways and kinetics for PEGs and PPGs under conditions simulating a spill of produced water to shallow groundwater. Sediment-groundwater microcosm experiments were conducted using four produced water samples from two Denver-Julesburg Basin wells at early and late production. High-resolution mass spectrometry was used to identify the formation of mono- and di-carboxylated PEGs and mono-carboxylated PPGs, which are products of PEG and PPG biodegradation, respectively. Under oxic conditions, first-order half-lives were more rapid for PEGs (<0.4–1.1 d) compared to PPGs (2.5–14 d). PEG and PPG degradation corresponded to increased relative abundance of primary alcohol dehydrogenase genes predicted from metagenome analysis of the 16S rRNA gene. Further degradation was not observed under anoxic conditions. Our results provide insight into the differences between the degradation rates and pathways of PEGs and PPGs, which may be utilized to better characterize shallow groundwater contamination following a release of produced water. 

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