Influence of CO<Subscript>2</Subscript> on the micro-structural properties of spider dragline silk: X-ray microdiffraction results

The mechanical properties of spider dragline fibres are altered by CO₂ exposure under anaesthetizing conditions during the spinning process. In order to relate these macroscopic changes to a microscopic model, the extrusion of dragline silk was studied by synchrotron radiation microdiffraction. A brief exposure of a female Nephila senigalensis spider to CO₂ results after an incubation time of less than 7 min in the extrusion of a thread (two fibres) swollen with water. The data are interpreted for a model of crystalline -sheet domains containing nanofibrils, which reinforce a network of protein chains. The protein network absorbs water, leaving the nanofibrils unaffected. A continuous flow of CO₂ results in a co-extrusion of a dragline thread and an isotropic silk fraction, which probably has a glycine-rich sequence. Long CO₂ exposure reduces the axial alignment of nanofibrils, presumably due to a partial destruction of the amorphous network.     

Survey of selected mycotoxins in food

The contamination of a variety of foods with the mycotoxins aflatoxins B1, B2, G1, M1, ochratoxin A, patulin, and byssochlamic acid was investigated. With the developed methods, the identification was made possible by in situ fluorescence spectral analysis with a far reaching exclusion of substances which simulate sycotoxins. Aflatoxin B1 was detected in 2 samples of 105 spontaneously moulded food specimens and only in 1 of a group of 198 food samples that were obviously not moulded. Aflatoxin M1 was identified in 4 of 60 samples of the so-called wintermilk. Investigated dairy products did not contain aflatoxin M1. Ochratoxin A could be detected twice in 49 spontaneously moulded corn samples, aflatoxin, however, was not found. Further investigations of 50 samples of moulded food revealed ochratoxin A in 2 samples of raw coffee. Food samples obviously not moulded did not contain ochratoxin A. Patulin was detected in 19 of 110 samples of fruit and fruit products, especially in commercial apple juice, in rotten parts of apples, and in moulded fruit products. Byssochlamic acid was not detected in fruit juices or in fruit. The toxicological consequences of mycotoxins in food and possibilities to reduce mycotoxins are discussed.