Single cobalt atoms anchored on Ti3C2Tx with dual reaction sites for efficient adsorption-degradation of antibiotic resistance genes.

The assimilation of antibiotic resistance genes (ARGs) by pathogenic bacteria poses a severe threat to public health. Here, we reported a dual-reaction-site-modified CoSA/Ti3C2Tx (single cobalt atoms immobilized on Ti3C2Tx MXene) for effectively deactivating extracellular ARGs via peroxymonosulfate (PMS) activation. The enhanced removal of ARGs was attributed to the synergistic effect of adsorption (Ti sites) and degradation (Co-O3 sites). The Ti sites on CoSA/Ti3C2Tx nanosheets bound with PO43- on the phosphate skeletons of ARGs via Ti-O-P coordination interactions, achieving excellent adsorption capacity (10.21 × 1010 copies mg-1) for tetA, and the Co-O3 sites activated PMS into surface-bond hydroxyl radicals (•OHsurface), which can quickly attack the backbones and bases of the adsorbed ARGs, resulting in the efficient in situ degradation of ARGs into inactive small molecular organics and NO3. This dual-reaction-site Fenton-like system exhibited ultrahigh extracellular ARG degradation rate (k > 0.9 min-1) and showed the potential for practical wastewater treatment in a membrane filtration process, which provided insights for extracellular ARG removal via catalysts design.

Visible-Light-Induced Heptacene Generation under Ambient Conditions: Utilization of Single-crystal Interior as an Isolated Reaction Site.

The photo-induced generation of unstable molecules generally requires stringent conditions to prevent oxidation and the concomitant decomposition of the products. The visible-light-induced conversion of two heptacene precursors to heptacene was studied. Single crystals of bis- and mono-α-diketone-type heptacene precursors (7-DK2 and 7-DK1, respectively), were prepared to investigate the effect of precursor structure on reactivity. The photoirradiation of a 7-DK2 single crystal cleaved only one α-diketone group, forming an intermediate bearing a pentacene subunit, while that of a 7-DK1 single crystal gave rise to characteristic absorption peaks of heptacene and their increase in intensity with photoirradiation time, indicating the generation of heptacene without decomposition. Heptacene production was not observed when the precursors were photoirradiated in solution, implying that the single crystal interior provided isolation from the external environment, thus preventing heptacene oxidation.

A study of bias and increasing organismal complexity from their post-translational modifications and reaction site interplays.

Post-translational modifications (PTMs) are important steps in the biosynthesis of proteins. Aside from their integral contributions to protein development, i.e. perform specialized proteolytic cleavage of regulatory subunits, the covalent addition of functional groups of proteins or the degradation of entire proteins, PTMs are also involved in enabling proteins to withstand and recover from temporary environmental stresses (heat shock, microgravity and many others). The literature supports evidence of thousands of recently discovered PTMs, many of which may likely contribute similarly (perhaps, even, interchangeably) to protein stress response. Although there are many PTM actors on the biological stage, our study determines that these PTMs are generally cast into organism-specific, preferential roles. In this work, we study the PTM compositions across the mitochondrial (Mt) and non-Mt proteomes of 11 diverse organisms to illustrate that each organism appears to have a unique list of PTMs, and an equally unique list of PTM-associated residue reaction sites (RSs), where PTMs interact with protein. Despite the present limitation of available PTM data across different species, we apply existing and current protein data to illustrate particular organismal biases. We explore the relative frequencies of observed PTMs, the RSs and general amino-acid compositions of Mt and non-Mt proteomes. We apply these data to create networks and heatmaps to illustrate the evidence of bias. We show that the number of PTMs and RSs appears to grow along with organismal complexity, which may imply that environmental stress could play a role in this bias.

Insight into disparate nonradical mechanisms of peroxymonosulfate and peroxydisulfate activation by N-doped oxygen-rich biochar: Unraveling the role of active sites.

In this study, we first comprehensively studied peroxymonosulfate (PMS) and peroxydisulfate (PDS) activation mechanisms using N, O codoped sludge biochar (NOSB) to degrade organics from water. Among the catalysts, NOSB with a higher content of graphitic N, optimal edge nitrogen (pyridinic N and pyrrolic N), CO groups, sp2-hybridized C, and rich defects were demonstrated to be a superior catalyst. Therefore, by activating PDS and PMS, NOSB exhibited the highest rate of BPA degradation, which was 22-fold and 13-fold that of pristine sludge biochar, respectively. However, owing to different oxidation potentials and molecular structures, PMS and PDS show different degradation performances due to various catalytic mechanisms occurring, even with the same biochar. Due to the asymmetrical structure of PMS, electrons passed from PMS to NOSB and further generated singlet oxygen (1O2), which governs the degradation of bisphenol A with an auxiliary contribution of single electron transfer. Meanwhile, PDS is reduced at the Lewis basic sites of NOSB, forming inner-surface-bound {PDS-NOSB}, which was oxidizing around neighboring carbon and decomposed targets through transferring single and double electrons. NOSB is promising for practical applications because of its adaptation to a wide pH range, anions, high total organic carbon removal, tunable active sites, and re-usability for degrading organics via PMS/PDS activation. This study unveils knowledge about N, O codoped sludge biochar catalysts for activating PMS/PDS and advocates a great approach for organics' degradation in the environment.

Fragmentation method for assigning oxidation numbers in organic and bioorganic compounds.

Oxidation number (ON) is taught as an electron-counting concept for redox reactions in chemistry curriculum. The molecular formula method, the Lewis formula method, and the structural formula method have all been used to determine ON. However, the task of assigning ON still poses problems for some teachers and students. This paper explores a new method, the fragmentation method, which is a visual approach for counting the individual ON of any atom according to its structural formula. The critical step is to break the carbon-heteroatom bond into organic fragments and inorganic fragments. The individual ON of carbon atoms and heteroatoms can be determined by the bond cleavages in the organic and biological compounds. The mean ON of carbons can be calculated by the arithmetic mean of all individual ON of carbons in a molecule or molecular ion. The step-by-step operating procedures and examples are provided. When comparing corresponding molecules in organic conversions, the change of individual ON of atoms can be used as a tool for determining the number of transferred electrons. Furthermore, a reaction site can be identified by their changes of individual ON, chemical composition, and bond order in metabolic redox reactions.

Photo-transformation of atrazine in aqueous solution in the presence of Fe3+-montmorillonite clay and humic substances.

As one of the most troublesome herbicides, the natural behavior of atrazine has drawn great attentions. Currently, most studies investigated the adsorption of atrazine on clay minerals and humic substances (HSs), whereas, the transformation of atrazine catalyzed by clay and HSs was still unknown. In the present study, photo-degradation of atrazine in the presence of Fe3+-montmorillonite and Suwannee river fulvic acid (SRFA) in aqueous solution was systematically studied. In the Fe3+-montmorillonite system, the hydroxyl radical (OH) induced removal of atrazine was strongly pH-dependent and the reaction rate increased with the decrease of pH. The presence of SRFA suppressed the atrazine degradation by Fe3+-montmorillonite at pH 3 but promoted its removal rate in the pH range of 4-6. Our results demonstrated that both OH and singlet oxygen are responsible for the degradation process in the Fe3+-montmorillonite/SRFA hybrid system. The degradation of atrazine followed the cleavage of the CN bonds in aliphatic chains of atrazine, and three major products, desethylatrazine, desisopropylatrazine and desethyldesisopropylatrazine were detected. The toxicity assessment showed that the toxicity of the reaction solution significantly decreased after the radical reactions, indicating that the transformation of atrazine on natural clay minerals with/without HSs could be considered as a detoxification pathway, which might be important to evaluate the environmental risk of atrazine in a natural system.

Rapid characterization of structure-dependency gas-phase ion/ion reaction via accumulative tandem MS.

To enable the rapid detection of biomolecule reactivity and reaction sites, we developed a method based on gas-phase ion/ion reaction and accumulative tandem mass spectrometry (MS). Structure-dependency reactions in gas-phase were performed between biomolecule ions and their reaction partner ions with opposite polarities in a quadrupole ion trap. Gas-phase peptide bioconjugation with pyridoxal-5-phosphate (PLP) was chosen as a proof-of-principle example. It is found that the Coulomb attraction force holds reaction partners close together, which increasing the reaction probability. Post reaction, reaction sites were identified by the consequent accumulative tandem MS method, in which informative product ions in low abundance were enriched by more than 100 times in another quadrupole ion trap. With enough product ions, tandem MS was performed, and reaction sites could be identified unambiguously. Since those reactions are normally biomolecular structure dependent, density functional theory (DFT) calculations were also carried out to understand the reaction mechanism. The method allows for rapid characterization of structure dependent reactivity of a biomolecule, and opens a new avenue for drug development and biomolecule structure analyses.

Inoculation site from a cutaneous melanoma patient treated with an allogeneic therapeutic vaccine: a case report.

We have developed a therapeutic vaccine consisting of a mixture of lethally-irradiated allogeneic cutaneous melanoma cell lines with BCG and GM-CSF as adjuvants. The CSF-470 vaccine is currently being assayed in a Phase II-III trial against medium-dose IFN-α2b. All vaccinated patients immunized intradermally developed large edematous erythema reactions, which then transformed into subcutaneous nodules active for several months. However, vaccine injection sites were not routinely biopsied. We describe the case of a female patient, previously classified as stage III, but who, due to the simultaneous discovery of bone metastases only received one vaccination was withdrawn from the study, and continued her treatment elsewhere. This patient developed a post-vaccination nodule which was surgically removed 7 weeks later, and allowed to analyze the reactivity and immune profiling of the inoculation site. An inflammatory reaction with zones of fibrosis, high irrigation, and brisk lymphoid infiltration, primarily composed of CD8(+) and CD20(+) lymphocytes, was observed. There were no remaining BCG bacilli, and scarce CD4(+) and Foxp3(+) T cells were determined. MART-1 Ag was found throughout the vaccination site. CD11c(+) Ag presenting cells were either dispersed or forming dense nests. Some CD11c(+) cells proliferated; most of them contained intracellular MART-1 Ag, and some interacted with CD8(+) lymphocytes. These observations suggest a potent, long-lasting local inflammatory response with recruitment of Ag-presenting cells that incorporate melanoma Ags, probably leading to Ag presentation to naïve T cells.