Rhizobia synthesize a class of lipo-chitin oligosaccharides that induce root hair deformation and induce the initiation of nodule structures on legume roots. These lipo-chitin oligosaccharides are tetra-and penta-lipo-oligosaccharides of N-acetylglucosamine with an acyl substitution on the nonreducing end and are commonly known as Nod factors. In this study, we demonstrate that synthetic analogs of natural product Nod factors have the same biological activities. To determine structure-activity relationships, a collection of synthetic and natural product lipo-chitin oligosaccharides was assayed on Glycine soja. All biologically active lipo-chitin oligosaccharides induced both root hair deformation and nodule initiations on C. soja. The most active lipo-chitin oligosaccharides deformed root hairs at 1O-l' M and induced nodules at 1 ng of lipo-chitin oligosaccharide per spot inoculation. Plant responses demonstrate an interdependence of backbone length and the presence of substitutions on the reducing end. Lipo-chitin oligosaccharides containing four Kacetylglucosamine residues were active only without a reducing end modification, whereas lipo-chitin oligosaccharides containing five N-acetylglucosamine residues were active only with reducing end modification. The plant thus recognizes lipo-chitin oligosaccharides without reducing end substitutions despite the importance of these modifications for host range.Signal exchange between symbiotic organisms is best understood in the Xhizobium-legume symbiosis. Species of Rhizobium, Bradyrhizobium, and Azorhizobium (collectively known as rhizobia) enter into a mutualistic association with legumes in which the bacteria provide reduced nitrogen to the plant and the plant provides carbon and energy '

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4,4 0 -Diphenylmethane bismaleimide (BMI)/2,2 0 -diallylbisphenol A (DABPA) resin was modified with a multifunctional thiol containing isocyanuric ring and long-chain aliphatic unit (tris[(3-mercaptopropionyloxy)-ethyl]-isocyanurate (TEMPIC)). To investigate the relationship of the curing reaction and properties of cured BMI/DABPA resin modified with TEMPIC, the temporal change in the functional groups during the curing reaction process was analyzed using Fourier transform infrared analysis. Despite the decreased cross-link density with increasing TEMPIC concentration, the glass transition temperature of BMI/DABPA resin was not decreased by modification with TEMPIC. The storage modulus of BMI/DABPA/ TEMPIC resin maintained a value on the order of 10 9 Pa in the rubber region, which is similar to that of the unmodified resin. The fracture toughness and flexural strength were also improved by modification with TEMPIC. Moreover, the observation of the fracture surface of BMI/DABPA/TEMPIC resin using scanning electron microscopy showed a uniform structure with no phase separation. These results were consistent with the single -relaxation peak in the loss tangent curve of the dynamic viscoelastic behavior.

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