Efficiency of labeling

Figure 4. The efficiency of labelling of N-blocked or nonblocked heparins with FITC versus F-D. See text for details of experiment a, F1TC b, F-D.

Maximum labelling of heparin with F-D was achieved at 5 hours at 25 °C, pH 8.4. In the case of heparin, the efficiency of labelling was not dependent on molecular weight, but solely a function of the ratio of the concentrations of labelling reagent to monosaccharide subunit in the reaction mixture. Similar results were encountered in the labelling of dextrans of different molecular weight (9). 

Add to the glycan solution the molecule to be labeled containing an available amine, hydrazine, or hydrazide group. For small molecule derivatization, the final concentration of the nucleophile in the glycan solution should be about 0.3 M to result in maximal efficiency of labeling. For protein modification, an aqueous reaction buffer should be used, and the protein should be as concentrated as possible. 

In analytical chemistry there is an ever-increasing demand for rapid, sensitive, low-cost, and selective detection methods. When POCL has been employed as a detection method in combination with separation techniques, it has been shown to meet many of these requirements. Since 1977, when the first application dealing with detection of fluorophores was published [60], numerous articles have appeared in the literature [6-8], However, significant problems are still encountered with derivatization reactions, as outlined earlier. Consequently, improvements in the efficiency of labeling reactions will ultimately lead to significant improvements in the detection of these analytes by the POCL reaction. A promising trend is to apply this sensitive chemistry in other techniques, e.g., in supercritical fluid chromatography [186] and capillary electrophoresis [56-59], An alter-... 

Biases introduced during the isolation or labeling of the mRNA transcripts or in the hybridization process are also commonplace. These biases can be minimized by ensuring consistent RNA quality and quantity prior to labeling, as well as ensuring that the efficiency of labeling is consistent among samples. 

Goeldner, Hirth and colleagues have presented evidence that the efficiency of labeling by certain photoaffinity reagents is improved in the environment provided by the receptor. They define a photosuicide inhibitor as a ligand analog of an enzyme or a receptor, the photodecomposition of which is selectively induced by the intrinsic physico-chemical properties of an active site (Goeldner et al., 1982). 

To further define the stage of development at which optimal efficiency of labeling edible portions of soybeans and wheat, a series of pots were dosed sequentially beginning with the first... 

In the original system, biotin is attached to the deoxy analog of y-UTP via a spacer arm. Biodnylated dUTP is incorporated into DNA strands by a conventional labeling reaction, nick translation, which is also widely used to prepare radioactive probes (3). The presence of a spacer arm between biotin and dUTP separates these two molecules far apart, and thus, reduces the steric hindrance caused between them. Therefore, the efficiency of labeling, hybridization, and detection is greatly increased. 

Detectability (target concentration at which signal/noise ratio just exceeds that of blanks) and sensitivity ( = efficiency of hybridization times efficiency of label detection)... 

Fluorochrome labeling of streptavidin or antibody Conjugation procedures should yield optimal fluorochrome/protein (F/P) ratios. Most economically, the desired F/P ratio is regulated by the initial weight of dye in the reaction mixture and the reaction is allowed to go to completion. Alternatively, with relatively more dye, the reaction is interrupted after a specific incubation period. The efficiency of labeling depends on the protein, the protein concentration, the specific fluorochrome and the purity of the fluorochrome (some preparations only 30%). Over- or undercoupling leads to nonspecificity or low detectability, respectively. 

Further evidence implicating (68) as an intermediate in isoquinoline biosynthesis comes from the efficient incorporation of labelled (68) into (70) and with the specific incorporation, albeit with low efficiency, of labelled (68) into morphine (71). The amino-acid (72) was a very poor precursor for morphine, which indicates that both aromatic building blocks must be dihydroxylated before they are joined together. Simple chemical decarboxylation of (68) affords (69), which was found to act as a precursor for morphine [the triphenol (73) was incorporated too but at a lower level]. These observations taken with the labelling of (69) by dopa in P. orientale suggest that the imine (69) may also be an intermediate in isoquinoline biosynthesis. 

Determine the efficiency of labeling with an Agilent Bioanalyser or equivalent. 

Poly(vinyl pyrrolidone) Pyrex glass Improves separation efficiency of labeled amino acids and small peptides... 

A recent report suggests that use of a pH 9 buffer to dilute S-NHS-biotin would enhance the efficiency of labeling of surface proteins (Gottardi and Caplan, 1993). In our experience this is not always true and depends on different proteins and cell lines. 

From this, and from the fact that feeding experiments by Haslam s and Stafford s groups have shown that the efficiency of labelling in procyanidin units is much higher than for the flavan-3-ol terminal units of dimers, it is tempting to speculate that the two types of unit may sometimes be derived from quite distinct biosynthetic pathways in the plant, so that these pathways are not always in direct sequence. The oxidation pattern and stereochemistry of the proanthocyanidin and chain-terminating groups will, therefore, not always be the same. 

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