Chemistry

This article reports a detailed reinvestigation of the reaction of bis(dialkyldithiocarbamato)zinc(II) (ZDAC) with amines. The reaction of primary amines with bis(dimethyldithiocarbamato)zinc(II) (ZDMC) results in the formation of a 1,1,3-trisubstituted thiourea, a 1,3-disubstituted thiourea, dimethylammonium dimethyldithiocarbamate (DMADC), ZnS, and H 2 S. The ratio of formation between the two thiourea products strongly depends on the reaction conditions chosen. A new mechanism is proposed, which involves the formation of an amine-dithiocarbamic intermediate, from which the two most important products, a 1,1,3-trisubstituted and a 1,3-disubstituted thiourea, are formed. Also, direct transformation of the 1,1,3-trisubstituted thiourea into the 1,3-disubstituted thiourea via nucleophilic attack of the primary amine onto the thiocarboxy of the 1,1,3trisubstituted thiourea was found to occur, catalyzed by ZnCl 2 . The reaction of primary amines with ZDACs is catalyzed by elemental sulfur, which has been attributed to sulfur insertion in the zinc-ligand ring of the ZDAC, resulting in a higher reactivity of the ZDAC complex. Finally, when ZDACs are reacted with a secondary amine, no thiourea products are formed and only a mixture of zinc dithiocarbamates is obtained.

This article reports a detailed reinvestigation of the reaction of bis(dialkyldithiocarbamato)zinc(II) (ZDAC) with amines. The reaction of primary amines with bis(dimethyldithiocarbamato)zinc(II) (ZDMC) results in the formation of a 1,1,3-trisubstituted thiourea, a 1,3-disubstituted thiourea, dimethylammonium dimethyldithiocarbamate (DMADC), ZnS, and H 2 S. The ratio of formation between the two thiourea products strongly depends on the reaction conditions chosen. A new mechanism is proposed, which involves the formation of an amine-dithiocarbamic intermediate, from which the two most important products, a 1,1,3-trisubstituted and a 1,3-disubstituted thiourea, are formed. Also, direct transformation of the 1,1,3-trisubstituted thiourea into the 1,3-disubstituted thiourea via nucleophilic attack of the primary amine onto the thiocarboxy of the 1,1,3trisubstituted thiourea was found to occur, catalyzed by ZnCl 2 . The reaction of primary amines with ZDACs is catalyzed by elemental sulfur, which has been attributed to sulfur insertion in the zinc-ligand ring of the ZDAC, resulting in a higher reactivity of the ZDAC complex. Finally, when ZDACs are reacted with a secondary amine, no thiourea products are formed and only a mixture of zinc dithiocarbamates is obtained.

The ability to transport and use haemin as an iron source is frequently observed in clinical isolates of Shigella spp. and pathogenic Escherichia coli. We found that many of these haem-utilizing E. coli strains contain a gene that hybridizes at high stringency to the S. dysenteriae type 1 haem receptor gene, shuA. These shuA-positive strains belong to multiple phylogenetic groups and include clinical isolates from enteric, urinary tract and systemic infections. The distribution of shuA in these strains suggests horizontal transfer of the haem transport locus. Some haemutilizing pathogenic E. coli strains did not hybridize with shuA, so at least one other haem transport system is present in this group. We also characterized the chromosomal region containing shuA in S. dysenteriae. The shuA gene is present in a discrete locus, designated the haem transport locus, containing eight open reading frames. Several of the proteins encoded in this locus participate with ShuA in haem transport, as a Salmonella typhimurium strain containing the entire haem transport locus used haem much more efficiently than the same strain containing only shuA. The haem transport locus is not present in E. coli K-12 strains, but the sequences flanking the haem transport locus in S. dysenteriae matched those at the 78.7 minute region of E. coli K-12. The junctions and flanking sequences in the shuA-positive pathogenic E. coli strains tested were nearly identical to those in S. dysenteriae, indicating that, in these strains, the haem transport locus has an organization similar to that in S. dysenteriae, and it is located in the same relative position on the chromosome.

It has been demonstrated that protein ingestion before sleep increases muscle protein synthesis rates during overnight recovery from an exercise bout. However, it remains to be established whether dietary protein ingestion before sleep can effectively augment the muscle adaptive response to resistance-type exercise training. Here we assessed the impact of dietary protein supplementation before sleep on muscle mass and strength gains during resistance-type exercise training. Forty-four young men (22 ± 1 y) were randomly assigned to a progressive, 12-wk resistance exercise training program. One group consumed a protein supplement containing 27.5 g of protein, 15 g of carbohydrate, and 0.1 g of fat every night before sleep. The other group received a noncaloric placebo. Muscle hypertrophy was assessed on a whole-body (dual-energy X-ray absorptiometry), limb (computed tomography scan), and muscle fiber (muscle biopsy specimen) level before and after exercise training. Strength was asses...

Nitrogen (N) can be recovered from different types of wastewaters. Among these wastewaters, anaerobically digested swine manure (digestate) has the highest N content in ammonia form (NH3). It is desirable to reduce N in digestate effluents to safely incorporate them in arable soil in N vulnerable zones (NVZ) and to mitigate NH3 emissions during N land application. Additional benefit is to minimize inhibition of the anaerobic process by removing NH3 during the anaerobic digestion process. This work aimed to apply the gas-permeable membrane technology to evaluate ammonia (NH3) recovery from high-ammonia digested swine manure. Anaerobically digested swine manure with NH4 + content of 4,293 mg N L −1 was reduced by 91 % (to 381 mg N L −1) during the 32-day experiment. Although the results showed a total N recovery efficiency of 71 %, it is possible to increase this recovery efficiency to > 90 % by adjusting the area of the membrane system to match the high free ammonia concentration (FA) in digested swine manure. Moreover, final digestate pH and alkalinity were kept around 8.1 and 8,923 mgCaCO3 L −1 , which are convenient for the anaerobic process or incorporation in arable soil when the process is finished.