Carbohydrates sample contamination

In the reductive animation method, it is important to use reagents and reactants of high purity. The carbohydrate sample should not contain carbohydrate contaminants, as, if they were present, an adsorbent containing more than one type of ligand would be obtained. The sodium cyanoborohydride should be of high purity, because reduction of the Schiff base may not occur with impure preparations. Special procedures have been developed for purifying sodium cyanoborohydride, and these should be employed.25... 

The type of data produced in a f.a.b. experiment is affected by the pH and ionic strength of the matrix. The former may be controlled either by the addition of acids or bases, although, in practice, it is usually preferable to keep the matrix acidic. The ionic strength is partly dictated by the purity of the sample (many biological compounds are still contaminated with salts, even after extensive purification) and partly by exogenous additives. Three additives are especially useful for carbohydrate work. They are as follows. 

Next, the removal of any suspected contaminants—such as carbohydrates (e.g., glucose), free amino acids, nucleotides and so on—can be accomplished by the procedure of Wells and Dittmer (1963). The lipid sample, dissolved in a mixture of chloroform-methanol-water (60 30 4.5, v/v), is passed through a previously washed column of Sephadex G-25, the effluent is collected and saved, and the column is then washed with a mixture of chloroform-methanol (2 1, v/v). The second eluent is collected and combined with the first and will contain all the phospholipid, free of contaminants. The two eluates are combined, phased by the addition of water, and then the chloroform-rich layer is removed and evaporated to dryness under nitrogen. The residue is dissolved in chloroform-methanol (2 1, v/v) and made to volume in a glass-stoppered volumetric flask. 

A lignin sample free of contaminants not chemically bonded to lignin such as carbohydrates, extractives, and monomeric, dimeric, and oligomeric lignin degradation products... 

If the amounts of contaminants in the lignin sample are not negligible, e.g., the carbohydrate and protein contents are each more than 2% of the lignin, then... 

Any study of collagen by similar procedures is hampered by several drawbacks. The most difficult problem is that of purity of the original protein. With insoluble collagen, especially, it is very difficult to prepare a sample free from impurities. As the impurities include mucoproteins and elastin, which have carbohydrate components, it will be essential to avoid confusion with these possible contaminants. 

The 1950s also saw the first evidence that chromium might be a dietary essential. Chromium is believed to promote the action of insulin and thus influences the metabolism of carbohydrates, fats, and proteins. Reports of severe human deficiency of chromium are rare and have been found primarily in people receiving only intravenous feedings for several months or years. Only a few laboratories in the world can accurately measure the amount of chromium in foods and body tissues because chromium is present in stainless steel, which is ubiquitous in analytical laboratories and easily contaminates biological samples. 

Miniaturization of sample handling and processing steps should significantly reduce losses associated with adsorption at the surfaces, sample transfers, as well as potential contamination. Integration and concomitant minimization of the analysis steps on-chip, including purification, concentration, separation, and detection, will ultimately enhance sensitivity and efficiency of the carbohydrate analysis, and glycan screening in particular. 

The DNA is not free from contaminants such as carbohydrates, but is of a suitable grade for enzyme digestion, Southern blotting (2, and Chapter 4), and analysis by polymerase chain reaction (PCR), such as the RAPD technique (S, and Chapter 34). We have used this procedure on wheat, barley, maize, oilseed rape, vegetable Brassicas, peas, and onions. A benefit of the method is that it requires little hands-on time by the operator, and can therefore be used to process large numbers of samples on a daily basis. 

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