Arsenic speciation in food in Belgium. Part 2: Cereals and cereal products.

This study reports results of total arsenic (Astot) and various As species in 75 samples of cereals and cereal products bought on the Belgian market. In addition to rice, the samples were wheat, pasta, bread and some breakfast cereals. The inorganic species arsenite (AsIII) and arsenate (AsV), and the organic As compounds dimethyl arsinate (DMA) and monomethyl arsonate (MA) were the only As species detected. Mean Astot was 0.150 ±â€¯0.089 mg kg-1 in rice and 0.012 ±â€¯0.008 mg kg- in the non-rice cereals. The inorganic arsenic fraction (Asi = AsIII + AsV) dominated in all samples and was in the range 55%-100%. Significantly higher Astot and Asi concentrations were observed in white rice and brown rice compared to Basmati rice. Within the group of non-rice cereals bread and pasta showed significantly lower concentrations compared to wheat. All 30 rice samples were conform to the European maximum limits for Asi, laid down in Commission Regulation (EU) 2015/1006. Although regulatory limits certainly can help to protect consumer health, our results suggest that the currently fixed European maximum levels are, in Belgium, not expected to have any impact on the human exposure to Asi, which is a known carcinogenic substance.

A simple and traceless solid phase method simplifies the assembly of large peptides and the access to challenging proteins.

Chemical protein synthesis gives access to well-defined native or modified proteins that are useful for studying protein structure and function. The majority of proteins synthesized up to now have been produced using native chemical ligation (NCL) in solution. Although there are significant advantages to assembling large peptides or proteins by solid phase ligation, reports of such approaches are rare. We report a novel solid phase method for protein synthesis which relies on the chemistry of the acetoacetyl group and ketoxime ligation for the attachment of the peptide to the solid support, and on a tandem transoximation/rearrangement process for the detachment of the target protein. Importantly, we show that the combination of solid phase and solution ligation techniques facilitates the production of a challenging and biologically active protein made of 180 amino acids. We show also that the solid phase method enables the purification of complex peptide segments through a chemoselective solid phase capture/release approach.

Correction: A simple and traceless solid phase method simplifies the assembly of large peptides and the access to challenging proteins.

[This corrects the article DOI: 10.1039/C7SC01912B.].