Enzymes polysaccharides

This process, frequently called lyophilisation, is necessary when water is to be removed from solutions containing heat-labile materials so that conventional distillation, even under reduced pressure, would cause extensive losses by decomposition. Examples are to be found in the removal of water from aqueous solutions of enzymes, polysaccharides, peptides, etc. In principle the aqueous solution is frozen in a suitable solid carbon dioxide freezing mixture (see Section 2.12), and the ice is sublimed off to leave a dry residue.42... 

In the absence of enzymes, polysaccharide hydrolysis is relatively slow (Table 3.7), with the OC-linked polymers (e.g. amylose) being slightly more stable than their (3-linked counterparts (e.g. cellulose and chitin). It appears that glycosidases can accelerate hydrolysis by a factor of c.1017 (Wolfenden et al. 1998). 

Furthermore, analytes involved in food immunoassays are of extremely different chemical nature, and are present in a very broad range of concentrations. Whereas macromolecules (such as protein, enzymes, polysaccharides, and microbial cell-wall components) are generally present in the mg per kg range, environmental contaminants, residues from farming practices, antibiotics, toxins, and pathogens are often present at much lower concentration, as low as 0.1 pg per kg. Food analytes for which immunoassays have been developed and are commercially available are listed in Table 1. 

Macromolecules Proteins (enzymes), polysaccharides, nucleic acids 10 to 10 ... 

Proteins, enzymes, polysaccharides, and nucleic acids are natural biologically active polymers, but no attempt will be made to review these diverse systems here several recent books and review articles are available.20-22,58-60 synthetic analogs have been prepared of essentially every type of natural macromolecule and many of these have exhibited biological activity. These analogs will be considered briefly in the next several sections. 

Bioactive polymeric materials have existed from the creation of life itself. Many firmly believe that life could not even exist unless polymeric materials are used to form the basic building blocks. Although this assumption can not be rigorously proven, it is a fact that most, if not all, of the major biochemical pathways involve polymeric species, such as the proteins (including enzymes), polysaccharides and nucleic acids. Among the many reasons for this fact, must be the observation that the natural polymeric materials can be made into an enormous variety of different, but inter-related, species. It is now well established that a DNA chain, which only contains four different primary repeating units, can encode an enormous wealth of data permitting not only the replication processes, but protein synthesis and the entire life scheme as well. 

The raw pulp of Aloe vera contains approximately 98.5 % water, while the mucilage or gel consists of about 99.5% water. The remaining 0.5-1% solid material consists of a range of compounds including water soluble and fat soluble vitamins, minerals, enzymes, polysaccharides, phenatic compounds and organic acids. It has been hypothesized that this heterogeneous composition of the Aloe vera pulp may contribute to the diverse pharmacological and therapeutic activities which have been observed for aloe gel products [62, 63]. 

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