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A commercially available enzymic method for the quantitative measurement of (1 → 3),(1 → 4)‐β‐glucan has been simplified to allow analysis of up to 10 grain samples in 70 min or of 100–200 samples by a single operator in a day. These improvements have been achieved with no loss in accuracy or precision and with an increase in reliability. The glucose oxidase/peroxidase reagent has been significantly improved to ensure colour stability for periods of up to 1 h after development. Some problems experienced with the original method have been addressed and resolved, and further experiments to demonstrate the quantitative nature of the assay have been designed and performed.

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New resonance Raman (RR) spectra at 15 K are reported for poplar (Populus nigra) and oleander (Oleander nerium) plastocyanins and for Alcaligenes faecalis pseudoazurin. The spectra are compared with those of other blue copper proteins (cupredoxins). In all cases, nine or more vibrational modes between 330 and 460 cm-1 can be assigned to a coupling of the Cu-S(Cys) stretch with Cys ligand deformations. The fact that these vibrations occur at a relatively constant set of frequencies is testimony to the highly conserved ground-state structure of the Cu-Cys moiety. Shifts of the vibrational modes by 1-3 cm-1 upon deuterium exchange can be correlated with N-H...S hydrogen bonds from the protein backbone to the sulfur of the Cys ligand. There is marked variability in the intensities of these Cys-related vibrations, such that each class of cupredoxin has its own pattern of RR intensities. For example, plastocyanins from poplar, oleander, French bean, and spinach have their most intense feature at approximately 425 cm-1; azurins show greatest intensity at approximately 410 cm-1, stellacyanin and ascorbate oxidase at approximately 385 cm-1, and nitrite reductase at approximately 360 cm-1. These variable intensity patterns are related to differences in the electronic excited-state structures. We propose that they have a basis in the protein environment of the copper-cysteinate chromophore. A further insight into the vibrational spectra is provided by the structures of the six cupredoxins for which crystallographic refinements at high resolution are available (plastocyanins from P. nigra, O. nerium, and Enteromorpha prolifera, pseudoazurin from A. faecalis, azurin from Alcaligenes denitrificans, and cucumber basic blue protein). The average of the Cu-S(Cys) bond lengths is 2.12 +/- 0.05 A. Since the observed range of bond lengths falls within the precision of the determinations, this variation is considered insignificant. The Cys ligand dihedral angles are also highly conserved. Cu-S gamma-C beta-C alpha is always near -170 degrees and S gamma-C beta-C alpha-N near 170 degrees. As a result, the Cu-S gamma bond is coplanar with the Cys side-chain atoms and part of the polypeptide backbone. The coplanarity accounts for the extensive coupling of Cu-S stretching and Cys deformation modes as seen in the RR spectrum. The conservation of this copper-cysteinate conformation in cupredoxins may indicate a favored pathway for electron transfer.

The quantitative in situ generation of a range of Cr(IV) carboxylato complexes in aqueous media has been achieved by a combination of the newly-developed Cr(IV) ligand exchange chemistry together with the existing methods of reduction of Cr(VI) or Cr(V) complexes. The reactions Cr(VI) + As(III) and Cr(V) + V(IV) in buffer solutions of the corresponding ligands were used for generation of Cr(IV) complexes with 2-hydroxy-2-methylbutanoate (hmba), 2-ethyl-2-hydroxybutanoate (ehba), and (−)-quinate (qa) ligands. Addition of oxalate (ox), malonate (mal), or 2-picolinate (pic) to the generated Cr(IV) complexes led to the quantitative formation of the new Cr(IV) species. Spectral and chemical properties of Cr(IV) complexes with the mentioned ligands have been described for the first time (except for the known Cr(IV)−ehba complexes). In excess ligand, Cr(IV) appears to exist mainly as bis-chelated oxo complexes, on the basis of UV−visible and CD spectroscopic data. All of the studied Cr(IV) complexes exhibit bell-shaped pH dependences of their stabilities. The regions of maximum stabilities and maximal half-lives ([Cr(IV)]0 = 0.1 mM; 25 °C) are as follows:  pH ∼ 3 and ∼30 min for Cr(IV)−hmba and Cr(IV)−ehba; pH ∼ 5 and ∼1.5 h for Cr(IV)−ox; pH ∼ 5 and ∼1.5 min for Cr(IV)−mal; pH ∼ 5 and ∼20 min for Cr(IV)−pic; pH ∼ 6 and ∼1 h for Cr(IV)−qa. The stabilities of Cr(IV) complexes have been compared with those of the corresponding Cr(V) complexes (studied by EPR spectroscopy). The results are discussed in terms of the possible roles of Cr(IV) and Cr(V) complexes as the DNA-damaging agents in chromium-induced genotoxicities.