Showing papers in "Advances in Carbohydrate Chemistry and Biochemistry in 1975"
TL;DR: These interactions are important in many of the industrial applications of galactomannans, and a study of them may also help provide an understanding of the associations among polysaccharide chains, contributing to biological cohesion and texture.
Abstract: Publisher Summary This chapter discusses the interaction of galactomannans with other polysaccharides. The general chemistry of the galactomannans has been reviewed by Whistler and Smart and others. The chapter discusses the uses of guar and locust-bean gums in various industrial applications and investigates the structural chemistry of galactomannans, especially as revealed by enzymic studies. Mixtures of locust-bean gum with the non-gelling polysaccharide from Xanthomonas campestris have been shown to interact synergistically to give firm, rubbery gels, whereas the use of the galactomannan from C yamopsis tetragonolobus (guar gum) results only in viscosity enhancement. These interactions are important in many of the industrial applications of galactomannans, and a study of them may also help provide an understanding of the associations among polysaccharide chains, contributing to biological cohesion and texture. The two main groups of galactomannan polysaccharides are those derived from (1) the endosperm of plant seeds, the vast majority of which originate in the Leguminoseae, and (2) microbial sources, in particular, the yeasts and other fungi. D-Mannose and D galactose are also found in numerous other plant polysaccharides—for example, glucomannansm, mannans, and galactans.
614 citations
TL;DR: In this article, the chemical methods for specific or selective degradation of polysaccharides and their applications for structural analysis are discussed, including the application of consecutive degradations, each of which should ideally be quantitative, should facilitate determination of complicated structures with moderate effort.
Abstract: Publisher Summary This chapter discusses the chemical methods for specific or selective degradation of polysaccharides and applications of polysaccharides for structural analysis. The degradation of polysaccharides by the action of acids, followed by the fractionation and identification of the oligosaccharides formed, is one of the methods used frequently in structural polysaccharide chemistry, and it gives information both on sequences and anomeric configurations. In principle, any reaction that can be performed at the monomer level should be applicable to polysaccharides and rapid development in this field will be seen. Application of consecutive degradations, each of which should ideally be quantitative, should facilitate determination of complicated structures with moderate effort. G.l.c. an established method for the separation of the low-molecular weight products formed. Mass spectrometry and nuclear magnetic resonance spectroscopy, especially when combined with pulse Fourier transformation (PFT-n.m.r.), are becoming increasingly important for the characterization of the degradation products.
162 citations
TL;DR: In this article, an attempt is made to rationalize the different kinds of behavior of carbohydrate amines, including the cyclitol amines upon deamination, and the potential use and limitations of these reactions in synthesis and elucidation of structure are discussed.
Abstract: Publisher Summary This chapter discusses the deamination of carbohydrates amine and related compounds. An attempt is made to rationalize the different kinds of behavior of carbohydrate amines—including the cyclitol amines, upon deamination. In addition, the potential use and limitations of these reactions in synthesis and in elucidation of structure are discussed in the chapter. A characteristic feature of deamination reactions is that rearrangement occurs to a greater extent, and more products are often formed, than in related solvolyses. This behavior has been related to the low activation-energies involved in the conversion of the diazonium ion into products, there being smaller differences in the activation energies for the competing pathways than for solvolysis. The activation energy for heterolysis of the alkanediazonium ion is presumed to be very low and according to the Hammond postulate, there should be relatively little bond-formation in the transition state. The relative unimportance of the “migratory aptitude” of a neighboring group in deamination is consistent with a nonconcerted mechanism.
77 citations
TL;DR: This chapter discusses the chemistry and biochemistry of apiose, and the elucidation of the biosynthetic pathway ofapiose was found on extensive, isotope-incorporation experiments in L.minor, L.gibba, and P.crispum.
Abstract: Publisher Summary This chapter discusses the chemistry and biochemistry of apiose. The chemical synthesis of D-apiose and some of its derivatives is defined in the chapter. Apiose is usually isolated as glycosides in which it is linked to compounds of low molecular weight. These include only derivatives of flavone, isoflavone, phenol, and anthraquinone. The large number of branched-chain sugars that have been isolated and the widespread occurrence of apiose led to speculation regarding the natural role of apiose-containing polysaccharides. The elucidation of the biosynthetic pathway of apiose was found on extensive, isotope-incorporation experiments in L.minor , L.gibba, and P.crispum. Biosynthetic reactions forming apiose can be divided into decarboxylative reactions, resulting in the biosynthesis of UDP-apiose, and transglycosylation reactions, resulting in the transfer of apiose from one compound to another.
53 citations
TL;DR: In the chapter, the specific immunoglobulin-hapten interaction is discussed and characterized, and carbohydrate chemistry may find a tool that can be increasingly applied to the unraveling of its own unsolved problems in the structural analysis of polysaccharides.
Abstract: Publisher Summary A new potential in polysaccharide immunochemistry is provided by homogeneous immunoglobulin that bind carbohydrate polymers.In the chapter, the specific immunoglobulin-hapten interaction is discussed and characterized. The discipline of carbohydrate chemistry can make a real contribution to the elucidation of the structure of immunoglobulin. In return, carbohydrate chemistry may find a tool that can be increasingly applied to the unraveling of its own unsolved problems in the structural analysis of polysaccharides. The chapter discusses the structure of immunoglobulins. The cellular component of the immune system that synthesizes and secretes immunoglobulin differentiates in a highly specialized way. The largest groups of anticarbohydrate, myeloma immunoglobulins are that of antifructans having specificity for β-D-(2 →1)-linkages. It is convenient to combine the discussion of this group with that of the anti-(2 →6)-β–D-fructan immunoglobulins.
51 citations
TL;DR: This chapter provides a general description of the facts and a discussion of the different variables that play a role in the yield of products formed and in the mechanisms involved in the reaction of ammonia with acylated mono- and disaccharides.
Abstract: Publisher Summary This chapter discusses the reaction of ammonia with acyl esters of carbohydrates. The processes that take place in this reaction include migrations, degradations, transesterifications, and deacylations, and their simultaneous occurrence makes the interpretation of the whole scheme very difficult. The chapter provides a general description of the facts and a discussion of the different variables that play a role in the yield of products formed and in the mechanisms involved. The reaction of acyl esters of aldoses and aldobioses with ammonia consists of a set of competitive pathways—including intramolecular 0 →N migrations of acyl groups, deacylations, and transesterifications, with formation of “aldose amides” and variable proportions of the free sugar as the principal products. Examination of acyl derivatives indicates whether a cyclic or an acyclic structure is present. A table of derivatives in the chapter, enlists the yield and properties of the products isolated from the reaction of ammonia with acylated mono- and disaccharides.
7 citations
1 citations