Avidin level

Multifloral New Zealand bee-collected pollen contains 1.85 0.08 jjiM biotin and New Zealand bee-bread contains 1.83 0.36 jjiM biotin (J.T. ChristeUer, personal communication). This suggests that pollen processing by the bees does not introduce additional biotin. Pollen avidin expression levels have not yet been measured (J.T. ChristeUer, personal communication). However, it is possible that avidin levels may exceed biotin levels in GM pollen. We have fed newly-emerged adult honeybees ad libitum with multifloral pollen with 6.7 or 20 jjlM avidin added and observed no significant change in the amounts of food consumed or in bee longevity, suggesting that such bees either have no need for biotin or can biosynthesize it (L.A. Malone, unpublished data). Further tests with bee larvae are under way. 

Isotope Dilution Assay. An isotope dilution assay for biotin, based on the high affinity of avidin for the ureido group of biotin, compares the binding of radioactive biotin and nonradio active biotin with avidin. This method is sensitive to a level of 1—10 ng biotin (82—84), and the radiotracers typically used are p C]biotin (83), [3H]biotin (84,85) or an I-labeled biotin derivative (86). A variation of this approach uses I-labeled avidin (87) for the assay. 

Metagenomics has been applied to the search for novel genes encoding the synthesis of vitamins such as biotin and vitamin C [47,76]. Seven cosmids were detected in metagenomic libraries obtained after avidin enrichment of environmental samples. The highest levels of biotin production in this study were detected in a cosmid... 

The physiologic sequelae of biotin deficiency are almost unexplored. Severe skin lesions, especially seborrheic dermatitis and Leiner s disease (Erythroderma desquamativum or exfoliative dermatitis), were increased in young infants bom of mothers on a restricted diet low in eggs, livers, and other biotin-rich foods. After biotin administration the lesions healed. There are claims that excess biotin produces a fatty liver characterized by heightened cholesterol content. Choline has no effect in the prevention of biotin-fatty livers (G2, M2). In mice with transplanted tumors, both the tumors and the blood levels of biotin are below normal (R8). More recent studies established a protection with avidin, the biotin-binding fraction of egg white, against tumor formation (K4). More data along these lines are still needed for confirmation. 

The amount of vaccine or therapeutic protein produced in a plant can reach industrial-scale levels. The typical yield of biopharmaceuticals produced in a plant-based system is 0.1%-1.0% of total soluble protein (Twyman et al., 2003). This value is competitive with other expression systems therefore, a plant expression platform for biopharmaceuticals is economically viable. As an example, one bushel of maize can produce as much avidin as one ton of chicken eggs but at 0.5% the cost. 

The avidin-biotin system was developed for detecting antigens at the electron microscope level (Heitzmann and Richards, 1974). Later Heggeness and Ash (1977) proposed the use of this system for fluorescence immunohistochemistry. Guesdon et al. (1979) proposed a variety of labeled avidin-biotin methods which were further supported by Warnke and Levy (1980). The avidin-biotin methods used today are similar to the system described by Hsu et al. (1981). This system is a significant improvement over the previous immuno-histochemical techniques. The problem of endogenous biotin is discussed on page 98. 

It has been suggested that the modification of the protein s isoelectric point could result in an alteration of its pharmacokinetic profile. Avidin acylation was performed by lysine amino group derivatization with succinyl anhydride or other anhydrides, which allowed the isoelectric point to be shifted to more acidic values, depending on the level of modification. Indeed, the protein anionization induced a reduction of accumulation in the liver, but resulted only in a limited prolongation of residence time in the circulation [30, 31]. 

Using the ELISA (with avidin-biotin bridges) and ELISPOT methods a stimulating effect of selected probiotic bacteria (Bifidobacterium longum, B animalis, Lactobacillus easel, L. salivarius) on the immune system of the rat and mouse has been demonstrated (higher level of specific as well as total IgGa and IgA content) (Nagy et al., 2002). 

Immobilized HRP and GOx on layered silicates using an avidin-biotin immobilization approach The immobilized enzymes retained high levels of activity compared to the native enzymes and showed improved thermal behavior. In addition, the immobilized GOx retained 65% of its initial activity at 58°C [30]... 

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