1.Effects of conformational ordering on protein/polyelectrolyte electrostatic complexation: ionic binding and chain stiffening.
Cao Y1, Fang Y1,2, Nishinari K1,2, Phillips GO1. Sci Rep. 2016 Mar 31;6:23739. doi: 10.1038/srep23739.
Coupling of electrostatic complexation with conformational transition is rather general in protein/polyelectrolyte interaction and has important implications in many biological processes and practical applications. This work studied the electrostatic complexation between κ-carrageenan (κ-car) and type B gelatin, and analyzed the effects of the conformational ordering of κ-car induced upon cooling in the presence of potassium chloride (KCl) or tetramethylammonium iodide (Me4NI). Experimental results showed that the effects of conformational ordering on protein/polyelectrolyte electrostatic complexation can be decomposed into ionic binding and chain stiffening. At the initial stage of conformational ordering, electrostatic complexation can be either suppressed or enhanced due to the ionic bindings of K(+) and I(-) ions, which significantly alter the charge density of κ-car or occupy the binding sites of gelatin. Beyond a certain stage of conformational ordering, i.
2.A General Copper-Catalyzed Vinylic Halogen Exchange Reaction.
Nitelet A1, Evano G1. Org Lett. 2016 Apr 15;18(8):1904-7. doi: 10.1021/acs.orglett.6b00678. Epub 2016 Mar 31.
An efficient and general system for the halogen exchange reaction in alkenyl halides has been developed. Upon reaction with catalytic amounts of copper iodide and trans-N,N'-dimethylcyclohexane-1,2-diamine in the presence of tetramethylammonium chloride or bromide, a wide range of easily accessible alkenyl iodides can be smoothly transformed to their far less available chlorinated and brominated derivatives in excellent yields and with full retention of the double bond geometry. This reaction also enables the chlorination of bromoalkenes and could be extended to the use of gem-dibromoalkenes.
3.Biodegradation of tetramethylammonium hydroxide (TMAH) in completely autotrophic nitrogen removal over nitrite (CANON) process.
Chen SY1, Lu LA2, Lin JG3. Bioresour Technol. 2016 Feb 12. pii: S0960-8524(16)30103-1. doi: 10.1016/j.biortech.2016.01.127. [Epub ahead of print]
This study conducted a completely autotrophic nitrogen removal over nitrite (CANON) process in a continuous anoxic upflow bioreactor to treat synthetic wastewater with TMAH (tetramethylammonium hydroxide) ranging from 200 to 1000mg/L. The intermediates were analyzed for understanding the metabolic pathway of TMAH biodegradation in CANON process. In addition, 15N-labeled TMAH was used as the substrate in a batch anoxic bioreactor to confirm that TMAH was converted to nitrogen gas in CANON process. The results indicated that TMAH was almost completely biodegraded in CANON system at different influent TMAH concentrations of 200, 500, and 1000mg/L. The average removal efficiencies of total nitrogen were higher than 90% during the experiments. Trimethylamine (TMA) and methylamine (MA) were found to be the main biodegradation intermediates of TMAH in CANON process. The production of nitrogen gas with 15N-labeled during the batch anaerobic bioreactor indicated that CANON process successfully converted TMAH into nitrogen gas.
4.Quantitative Survey and Structural Classification of Hydraulic Fracturing Chemicals Reported in Unconventional Gas Production.
Elsner M1, Hoelzer K1. Environ Sci Technol. 2016 Apr 5;50(7):3290-314. doi: 10.1021/acs.est.5b02818. Epub 2016 Mar 9.
Much interest is directed at the chemical structure of hydraulic fracturing (HF) additives in unconventional gas exploitation. To bridge the gap between existing alphabetical disclosures by function/CAS number and emerging scientific contributions on fate and toxicity, we review the structural properties which motivate HF applications, and which determine environmental fate and toxicity. Our quantitative overview relied on voluntary U.S. disclosures evaluated from the FracFocus registry by different sources and on a House of Representatives ("Waxman") list. Out of over 1000 reported substances, classification by chemistry yielded succinct subsets able to illustrate the rationale of their use, and physicochemical properties relevant for environmental fate, toxicity and chemical analysis. While many substances were nontoxic, frequent disclosures also included notorious groundwater contaminants like petroleum hydrocarbons (solvents), precursors of endocrine disruptors like nonylphenols (nonemulsifiers), toxic propargyl alcohol (corrosion inhibitor), tetramethylammonium (clay stabilizer), biocides or strong oxidants.