A Comparison of Three Different Biodegradable Aliphatic Oligoesters (PGA,PLLA, and PCL) with Similar Linear Alkyl End Groups by DSC and SAXS

The biodegradable aliphatic oligoesters polyglycolide (PGA), poly(L-lactide) (PLLA), and poly(?-caprolactone) (PCL) with similar number-average molecular weight M_n values but different linear alkyl end groups [CH₃?[CH₂?CH₂]_m?CH₂?] were compared in terms of their physical properties, parameters such as melting temperature (T_m), crystallinity (x_i), long period (L), and lamella thickness (D). They were analyzed by DSC and SAXS. The effect of a longer and nonpolar alkyl end group such as docosyl [CH₃?[CH₂?CH₂]₁₀?CH₂?] on the long period (L) was more evident for PCL because it was the most nonpolar species in the family of oligoesters analyzed.     

Cholesterol Hydroperoxides as Substrates for Cholesterol‐Metabolizing Cytochrome P450 Enzymes and Alternative Sources of 25‐Hydroxycholesterol and other Oxysterols

The interaction of the primary autoxidation products of cholesterol, namely 25‐ and 20ξ‐hydroperoxides, with the four principal cholesterol‐metabolizing cytochrome P450 enzymes is reported. Addition of cholesterol 25‐hydroperoxide to the enzymes CYP27A1 and CYP11A1 induced well‐defined spectral changes while generating 25‐hydroxycholesterol as the major product. The 20ξ‐hydroperoxides induced spectral shifts in CYP27A1 and CYP11A1 but glycol metabolites were detected only with CYP11A1. CYP7A1 and CYP46A1 failed to give metabolites with any of the hydroperoxides. A P450 hydroperoxide‐shunt reaction is proposed, where the hydroperoxides serve as both donor for reduced oxygen and substrate. CYP27A1 was shown to mediate the reduction of cholesterol 25‐hydroperoxide to 25‐hydroxycholesterol, a role of potential significance for cholesterol‐rich tissues with high oxidative stress. CYP27A1 may participate in the removal of harmful autoxidation products in these tissues, while providing a complementary source of 25‐hydroxycholesterol, a modulator of immune cell function and mediator of viral cell entry.     

Olefin‐Directed Palladium‐Catalyzed Regio‐ and Stereoselective Oxidative Arylation of Allenes

An olefin‐directed palladium‐catalyzed oxidative regio‐ and stereoselective arylation of allenes to afford 1,3,6‐trienes has been established. A number of functionalized allenes, including 2,3‐ and 3,4‐dienoates and 3,4‐dienol derivatives, have been investigated and found to undergo the olefin‐directed allene arylation. The olefin moiety has been proven to be a crucial element for the arylating transformation.     

A Zinc(II) Photocage Based on a Decarboxylation Metal Ion Release Mechanism for Investigating Homeostasis and Biological Signaling

Metal ion signaling in biology has been studied extensively with ortho‐nitrobenzyl photocages; however, the low quantum yields and other optical properties are not ideal for these applications. We describe the synthesis and characterization of NTAdeCage, the first member in a new class of Zn²⁺ photocages that utilizes a light‐driven decarboxylation reaction in the metal ion release mechanism. NTAdeCage binds Zn²⁺ with sub‐pM affinity using a modified nitrilotriacetate chelator and exhibits an almost 6 order of magnitude decrease in metal binding affinity upon uncaging. In contrast to other metal ion photocages, NTAdeCage and the corresponding Zn²⁺ complex undergo efficient photolysis with quantum yields approaching 30 %. The ability of NTAdeCage to mediate the uptake of ⁶⁵Zn²⁺ by Xenopus laevis oocytes expressing hZIP4 demonstrates the viability of this photocaging strategy to execute biological assays.     

Analysis of volatile organic compounds released from the decay of surrogate human models simulating victims of collapsed buildings by thermal desorption–comprehensive two-dimensional gas chromatography–time of flight mass spectrometry

Field experiments were devised to mimic the entrapment conditions under the rubble of collapsed buildings aiming to investigate the evolution of volatile organic compounds (VOCs) during the early dead body decomposition stage. Three pig carcasses were placed inside concrete tunnels of a search and rescue (SAR) operational field terrain for simulating the entrapment environment after a building collapse. The experimental campaign employed both laboratory and on-site analytical methods running in parallel. The current work focuses only on the results of the laboratory method using thermal desorption coupled to comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (TD-GC × GC-TOF MS). The flow-modulated TD-GC × GC-TOF MS provided enhanced separation of the VOC profile and served as a reference method for the evaluation of the on-site analytical methods in the current experimental campaign. Bespoke software was used to deconvolve the VOC profile to extract as much information as possible into peak lists. In total, 288 unique VOCs were identified (i.e., not found in blank samples). The majority were aliphatics (172), aromatics (25) and nitrogen compounds (19), followed by ketones (17), esters (13), alcohols (12), aldehydes (11), sulfur (9), miscellaneous (8) and acid compounds (2). The TD-GC × GC-TOF MS proved to be a sensitive and powerful system for resolving the chemical puzzle of above-ground “scent of death”.