Single-detector micro-electro-mechanical scanning grating spectrometer.

A compact, robust grating spectrometer based on an optimised micro-electro-mechanical grating mirror component has been developed, built, and characterised. The application of an oscillating reflection grating micro-mirror component as scanning dispersive element in a modified Czerny-Turner monochromator layout enables the design of compact grating spectrometers capable of acquiring full spectra using a single detector element. Designed for a wavelength range between 1200 and 1900 nm, the spectrometer features a spectral resolution of 10 nm with wavelength stability better than +/-0.5 nm. One-hundred scan spectra can be acquired in less than one second, or spectral changes can be monitored at time a resolution of less than 10 ms. In combination with a fibre-optic interface and a typical weight of less than 1 kg, this makes this novel type of fully portable micro-electro-mechanical near-IR scanning spectrometer an interesting alternative to existing spectrometers and opens a range of new applications, in particular the detection of major and minor components in the near-IR.

Purification and partial characterization of a novel lectin from elder (Sambucus nigra L.) fruit.

A previously unknown haemagglutinin, named Sambucus nigra agglutinin-III (SNA-III), has been purified from the fruit of the elder (Sambucus nigra). Whereas elder bark agglutinin I (SNA-I) is highly specific for terminal alpha 2,6-linked sialic acid residues, SNA-III displays a high affinity for oligosaccharides containing exposed N-acetylgalactosamine and galactose residues. Different N-terminal sequences and the amino acid composition distinguish the fruit lectin from elder bark agglutinin II (SNA-II), which shows a similar carbohydrate specificity. The 40-fold higher affinity of SNA-III for asialofetuin than for human asialo-alpha 1-acid glycoprotein and human asialotransferrin respectively suggests a preference for O-linked glycans. SNA-III occurs mainly as a monomeric glycoprotein, but tends to form di- and oligo-meric aggregates. This aggregation seems to mediate the multivalent interaction, leading to agglutination. SDS/PAGE revealed two major polypeptides with apparent molecular masses of 32 and 33 kDa respectively. This heterogeneity is probably a result of proteolysis in the C-terminal region. Binding to concanavalin A and susceptibility to peptide: N-glycosidase F indicated the presence of N-glycosidically linked oligosaccharides.