Polysaccharides general aspects

In an earlier article1 on the application of enzymic techniques to the analysis of the structure of polysaccharides, the -d- and /3-D-glucans were discussed, as well as more-general aspects of the preparation and use of catabolic enzymes in such analyses. The present article describes enzymic contributions to knowledge of the structures of other polysaccharides, but an account of subsequent research on a- and jS-D-glucans is also included. 

Monosaccharides. Polysaccharides, and General Aspects of their Pvroivsis. 

As mentioned, molecular and mesoscopic approaches will be needed. The first part of the book mainly considers molecules. We start with some basic thermodynamics, interaction forces, and chemical kinetics (Chapters 2-4). The next chapter is also concerned with kinetic aspects it covers various transport phenomena (which means that a few mesoscopic aspects are involved) and includes some basic fluid rheology. Chapters 6 and 7 treat macromolecules Chapter 6 gives general aspects of polymers and discusses food polysaccharides in particular, with a largish section on starch Chapter 7 separately discusses proteins, highly intricate food polymers with several specific properties. Chapter 8 treats the interactions between water and food components and the consequences for food properties and processes. 

Polysaccharides. There is considerable variation among gelling polysaccharides in molecular structure, in type of junctions, and in the dependence of gel properties on external conditions. Treatment of all of these systems and their particulars is outside the scope of this book, so the discussion will be restricted to some general aspects. An important... 

This book is written for students who have taken elementary/introductory biochemistry and would like to take further courses in biochemistry related to special topics in nucleic acids, proteins, and/or polysaccharides. Thus it is designed for students who are familiar with the general aspects of biochemistry and would like to further their... 

Twenty-two different metal Ions have been shown to crosslink water-soluble polysaccharides . Water-soluble synthetic polymers can also be crosslinked by several types of metal Ions. This section will briefly summarize the state of knowledge regarding general aspects of metal ion crosslinked gels. Then, the most common EOR gel systems of this type, aluminum citrate, chromium redox, complexed chromium, and chromlum/blopolymer, will be described In detail. 

The sedimentation coefficient provides a useful indicator of polysaccharide conformation and flexibility in solution, particiflarly if the dependence of on Mw is known [62]. There are two levels of approach (i) a general level in which we are delineating between overall conformation types (coil, rod, sphere) (ii) a more detailed representation where we are trying to specify particle aspect ratios in the case of rigid structures or persistence lengths for linear, flexible structures. 

Once a general conformation type or preliminary classification has been established it is possible to use sedimentation data to obtain more detailed information about polysaccharide conformation. For example, the low value of ks/[v 0 25 found for the bacterial polysaccharide xylinan has been considered to be due to asymmetry [115]. If we then assume a rigid structure the approximate theory of Rowe [36,37] can be applied in terms of a prolate ellipsoid of revolution to estimate the aspect ratio p L/d for a rod, where L is the rod length and d is its diameter) 80. 

In an attempt to make this account as complete as possible, certain related aspects, such as the hydrolysis of polysaccharides, are briefly discussed, but, in general, the only references cited are to those papers that have also mentioned use of gas-liquid chromatography. These ancillary sections must, therefore, not be considered exhaustive in treatment, but rather to be representative. 

From the standpoint of synthesis of polysaccharides, the most significant aspect of a polymerization mechanism is whether or not it involves regio- and stereo-selective control. However, the structural and stereochemical problems with polysaccharide synthesis are generally simpler than those that obtain with a racemic, unsymmetrical monomer, such as (R, S)-propylene oxide. For example, a variable percentage of head-to-head and tail-to-tail sequences is found in... 

This chapter is primarily intended for plant biochemists and nutritionists who are interested in the chemical aspects, but carbohydrate chemists would also benefit from the biochemical approach to cell wall analysis. In general, chemical methods for analyzing polysaccharides will not be described because several reviews dealing with this subject are available (Aspinall, 1973,1976,1982a). However, attention will be drawn to certain aspects of the methods that may be of interest in the context of the analysis of specific cell wall polymers. 

The chemistry and biochemistry of carbohydrates in general is detailed in a four-volume series (31), and a comprehensive treatment of polysaccharides can be found in the three volumes edited by AspinaU (32). A multiauthored treatise on polysaccharides published in 2005 (33) covers a wide range of aspects of the structural diversity, biological relevance, and technological apphcations of polysaccharides. A volume in the series Comprehensive Natural Product Chemistry edited by Pinto (34) provides extensive detail on the biosynthesis and biological role of carbohydrates. 

The book is organized in several chapters and deals with the most important biopolymer classes like the different polysaccharides (starch, cellulose, chitin), lignin, proteins and (polyhydroxy alkanoates) as raw materials for bio-based plastics, as well as with materials derived from bio-based monomers like lipids, poly(lactic acid), polyesters, polyamides and polyolefines. Additional chapters on general topics - the market and availability of renewable raw materials, the importance of bio-based content and the aspect of biodegradability - provide important information related to all bio-based polymer classes. 

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