Carbohydrates structure factors

It is to be emphasized that, in the absence of elements of symmetry, as is the case for carbohydrates, determination of the molecular structure should be based on both the experimental, vibrational spectra and the calculated frequencies. In order to minimize the differences between experimental and calculated results, the structure factors utilized in the calculation should take into account the previous conformational studies. The peculiarities of carbohydrate structures, such as anomeric and exo-anomeric effects, are revealed by bond shortening and torsion-angle modifications. These modifications are accompanied by a change in the vibrational-energy level, and hence, by the corresponding information in their infrared or Raman spectra. 

G. M. Lipkind, A. S. Shashkov, S. S. Mamyan, and N. K. Kochetkov, The nuclear Overhauser effect and structural factors determining the conformations of disaccharide glycosides, Carbohydr. Res., 181 (1988) 1-12. 

Sialic acids are a family of nonulosonic acids that have been predominantly found as the outermost carbohydrate units on glycoproteins and glycolipids of vertebrates, or as components of polysaccharides in certain types of bacteria (I, 2). Sialic acids play vital roles in a variety of physiological and pathological processes in vertebrates, such as cellular recognition and communication (1, 2). They are also believed to be important virulence factors in bacteria, used by bacteria to mimic sialylated host cell surface carbohydrate structures to evade detection and attacking by the immune defense mechanisms of the host (3-6). 

Not only does carbohydrate structure affect properties such as chemical reactivity, but the structure and shape of carbohydrates are also major factors in a number of biological processes that depend on interactions between molecules—a phenomenon known as molecular recognition. In this section, we will consider mainly the conformations of carbohydrates in their pyranose forms. We will return to some familiar concepts of chair conformations and axial versus equatorial groups, but you will see that the presence of an oxygen atom in a six-membered ring leads to some surprising consequences. 

Huang, R., Rajapakse, N., and Kim, S. W. 2006. Structural factors affecting radical scavenging activity of chi-tooligosaccharides (COS) and its derivatives. Carbohydrate Polymers 63 122-129. 

These interactions involve adhesion proteins called selectins, which are found both on the rolling leukocytes and on the endothelial cells of the vascular walls. Selectins have a characteristic domain structure, consisting of an N-terminal extracellular lectin domain, a single epidermal growth factor (EGR) domain, a series of two to nine short consensus repeat (SCR) domains, a single transmembrane segment, and a short cytoplasmic domain. Lectin domains, first characterized in plants, bind carbohydrates... 

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