Many plant pathogens are host-selective, and specificity between varieties is often observed among cultured plants. In a few cases, the cause of the specificity is attributable to the toxins produced by pathogens, which are called host-specific toxins in these cases. So far, 13 microbes are known to produce 15 host-specific toxins, and 8 of them have their structures elucidated. Recent revelation by the studies we have been concerned with, that HMT- toxins, produced by H. maydis, race T, have structures analogous to PM-toxins produced by P. maydis, a microbe alien to H. maydis, gave stimulus to the re-recognition of importance of these toxins as pathotoxins, that are the conceived ultimate causal agents of plant diseases. Studies on structure-activity relationships and active molecular sites in progress, aided by synthetic chemical techniques. The chemical and biological aspects of these host-specific toxins are reviewed, including the results of our recent studies on ACRL-toxins, which are produced by 1 of 3 varieties of A. citri, which are specifically pathogenic to different citrus varieties.
Plant hormones are very important bio-active compounds which regulate the physiology of higher plants. There are five kinds of known plant hormones, auxin, gibberellin, cytokinin, abscisic acid and ethylene. Besides, there are some other plant hormone-like substances as brassinolide, polyamines and unknown flower-inducing substances. The studies of plant hormones concerning activity, practical use, fluctuation of endogenous level in intact plants, biosynthesis and structure-activity relationship are explained. The organic syntheses in these studies are important especially in production of plant hormones and their related compounds enough for their application test in the agricultural field, and various kinds of derivatization of plant hormones for the investigation of action mechanism and for the modern analysis methods with highest reliability and sensitivity. Some other importance of organic synthesis in plant hormone research is discussed.
This review deals with a research trend regarding the production of plant pigments by plant tissue and cell culture. In addition, here is introduced the production technology of shikonin derivatives by the cell culture of Lithospermum erythrorhizon, which is the only example of industrialization achieved by the author et al.
Contribution of organic chemistry in the field of chemical senses (taste and olfaction) was discussed. Organic chemistry has contributed to determination of the structure of chemicals which stimulate the chemical senses. The studies on structure-activity relationship of “umami” compounds have been carried out successfully. On the other hand, simple application of organic chemistry to structure-activity relationship for bitter compounds and odorants has a certain limit for elucidating the relationship. Combination of the technique of organic synthesis with other methods (e.g. measurements of the interaction of these stimuli with receptor membranes) will bring about fruitful results.
Newly developed artificial receptors and their clinical application are briefly described from the standpoint of biomimetic organic chemistry. Artificial receptors dealt with here are those for immune complexes in immune complex diseases, for anti-acetylcholine receptor antibodies in myasthenia gravis, and for low density lipoprotein in familial hypercholesterolemia, and are classified by intermolecular interaction forces, which are hydrophobic and electrostatic.
Preparations and characterization of bilayer lipid membranes (liposomes, synthetic bilayer vesicles, polymerized vesicles, bilayer-corked capsule membranes, and bilayer-immobilized films) are reviewed. Polymerized vesicles can form stable liposomes relative to natural ones. Bilayer-corked capsule membrane has a large inner aqueous phase and bilayers on the membrane act as a permeation valve, responding to stimuli from outside. Bilayer-immobilized films can be prepared from various methods and still have a characteristics of bilayers.
There are strong demands for innovative antithrombogenic materials in the field of clinical medicine, because of their necessity in fabricating implantable artificial organs and progressive surgical prosthesis. This paper reviews the present status of the development of antithrombogenic materials. Special emphasis was placed on the promising feature of microdomain structured polymers as antithrombogenic materials. A series of studies reviewed in this paper demonstrates that contact-induced activation of blood platelets, a triggering phenomenon of thrombosis, could be eliminated by designing a polymer surface to have appropriate microdomain structure. As a possible mechanism involved in this suppressive effect on activation of platelets, we have proposed a mechanism of “capping control”. In this proposed mechanism, we emphasize the close relationship between reorganization of cytoskeletal components and assemblage of membrane glycoproteins at polymer/platelet interface.
The use of modified base or alteration of base sequences, and chemical modifications are reviewed for the study of nucleic acid functions and structures. The examples included are the point mutation of promoter region of rDNA gene, replacement of the certain bases with modified ones in the recognition sequence of restriction endonuclease Bgl II and Sau 3AI, ozone-degradation of supercoiled plasmid DNA, replacement of nucleotides in the anticodon region of formylmethionine tRNA, and chemical modification of mouse 5S ribosomal RNA.
Studies on fluorine-modified vitamin D3 analogs : the design, synthesis and biological activity are reviewed. On the basis of the metabolism of vitamin D3 and the characteristic features of fluorine and fluorinated compounds, fluorine-modified vitamin D3 analogs were designed, synthesized and their biological activity was investigated to clarify the physiological significance of the metabolic hydroxylation of vitamin D3.