Determination of the structures of trisaccharides by 13C-n.m.r. spectroscopy

A literature survey of the ¹³C-n.m.r. chemical-shift data for aqueous solutions of monosaccharides, disaccharides, oligosaccharides, and their methyl derivatives is reported. Analysis of these data reveals a set of empirical rules which may be used in the elucidation of the structure of trisaccharides of known monosaccharide composition, and an example is reported. However, it is not possible to extend the rules to tetrasaccharides and higher saccharides without additional chemical-shift data for related model compounds.     

Further experimental investigations on the formation of plant compression fossils

Experimental work has been conducted on the formation of plant compression fossils using a simple compression apparatus in which actual plant material was compressed in wet sediment. Pressure was applied through a single perforated piston which only allowed the passage of water upwards out of the compacting sediment. Several lines of investigation were followed to establish the principal factors that dictate the form of a plant compression fossil. It is demonstrated that these include the grain size and the compressibility of the sediment, the degree of sediment fill of hollow structures within the plant organ prior to the compression, and finally the rigidity or degree of decay of the plant tissues before the deformation. The results of this work indicate that the horizontal dimensions of the plant organ change during compression. This is directly related to the compressibility of the sediment the plant was buried in; stems buried in clay matrices increased in horizontal dimensions, whereas stems buried in sand matrices underwent reductions in horizontal dimensions. This is associated with the difference in the response of these sediments to the hydrostatic stress that exists within the system during the initial stages of compaction. The results of this experimental study are used to interpret the structure and form of some plant compression fossils.     

Expression of A mating type genes of Coprinus cinereus in a heterologous basidiomycete host

The A mating factor of Coprinus cinereus determines compatibility in mating by regulating part of a developmental sequence that leads to dikaryon formation. The A genes that trigger development encode two different classes of homeodomain proteins, and for a successful mating, a protein of one class, HD 1, must interact with a protein of the other class, HD 2. In this report we show that C. cinereus A genes that encode HD 2 proteins, a2-1 and b2-1, can elicit A-regulated development in the heterologous host C. bilanatus. Transformation rates were very low, suggesting that the genes were poorly transcribed. The fact that the HD 2 genes are functionally expressed implies successful heteromultimeric association of putative DNA-binding proteins coded by the two Coprinus species. This interaction was sufficient to satisfy the need for different A factors in the formation of a fertile C. bilanatus dikaryon, but fertile dikaryons were more readily produced in matings with the a2-1 gene transformants. The C. cinereus A genes, b1-1 and d1-1, which encode HD1 proteins, were either not expressed or their proteins were non-functional in C. bilanatus. These experiments raise some interesting questions regarding HD1–HD2 protein interactions.