Labeling fractional

Extraction. Each dried plant part was Soxhlet-extracted with petroleum ether. The solvent was evaporated vacuo to give a residue labeled Fraction A (Scheme I). The marc was air-dried and extracted with ethanol in a Soxhlet apparatus. Evaporation of the solvent vacuo yielded Fraction B. The aqueous phase was removed by freeze-drying and the water-soluble residue was labeled Fraction C. 

Vaughan, D., Cheshire, M. V., and Mundie, C. M. (1974b). Uptake by beet root tissue and biological activity of 14C-labelled fractions of soil organic matter. Biochem. Soc. T. 2, 126-129. 

Fig. 11. Responses of the fractions of C-labeled fractions of isobutane (Z ) and isobutene (Ze) to a switch in the feed of pure isobutane to its equivalent (after 107).

In a direct competitive heterogeneous immunoassay, the competitor and the analyte present in solution compete for a limited amount of antibody-binding sites. A typical way of performing such an assay is shown in Fig. 9.6. In the most frequently employed format, the labelled competitor is mixed with the sample containing the analyte, and the formed mixture is added over a solid phase with immobilized antibody. When the equilibriinn is reached, the unbound analyte- and labelled competitor are removed from the solution and the labelled fraction bound to the solid phase is quantified. The obtained signal is inversely proportional to the analyte concentration. 

Most problems with this procedure have involved tracer impurities and the separation of bound and free labeled fractions. Several separation techniques have been used, including equilibrium dialysis, membrane ultrafiltration, and steady-state gel filtration. Their deficiencies include a requirement for a large sample volume, the need for complicated correction of sample volume changes that occur during the separation, and difficulties of collecting and measuring radioactivity in numerous fractions of each sample. Equilibrium dialysis has been used most often in the past, but serious errors often arise from the sample dilution required by this method. Symmetrical dialysis of undiluted samples is reported to be less susceptible to tracer contamination and dilution effects. Ultrafiltration also appears to overcome these problems and to obviate errors caused by dilution. 

The silk produced by these worms displayed — 15% labeling of the poly-alanine chains, while the glycine-rich domains only reached a five times lower labeling fraction. For these samples, double-quantum correlation spectroscopy (DOQSY) experimentswere performed. The 2D DOQSY spectra prove to be highly sensitive to the peptide... 

Table in. C-Labeled Fractions in the Tissues of Cows 48 Hours After Oral or Intravenous Dosing With C-Sulfamethazine ... 

C-Labeled Fraction From Tissue Oral Intravenous ... 

Table IV. Evidence for structure of C-labeled fractions in urine from cows after oral or intravenous dosing with " C-sulfamethazine... 

For labeling, fractions containing 0.5-1.0 mg/ml lamin were dialyzed against the labeling buffer (lamin A 8.0 M urea, 20 mM sodium phosphate, pH 7.0, 0.2 mM PMSF lamin LI 8.0 M urea, 20 mM sodium phosphate, pH 7.5,0.2 mM PMSF) for 2-3 hr at room temperature. Alternatively, lamins precipitated by the chloroform/methanol method were directly solubilized in labeling buffer. Typically, lamins at 0.5-1.0 mg/ml in 600 pX of labeling buffer were incubated... 

The solution is evaporated to about 4.5 1. either by gentle boiling or by blowing a stream of air over the surface of the heated solution. The solution is allowed to cool about one-sixth of the mass should crystallize. The liquor is poured from the crystals into another dish and is again evaporated. To the crystals is added about 200 ml. of water and the dish heated until these crystals are dissolved. The resulting solution is poured into a 2-1. pyrex Florence flask and the dish rinsed into the same container this flask is labeled fraction 1. From the remaining rare earth solution are then removed further fractions in the same way, and each is transferred to a 2-1. flask and labeled in sequence 2, 3, etc. The final liquor, which will have a volume of about 200 ml., forms the fraction with the highest number. The series will now consist of fractions 1 to 7 aU should be nearly the same size except the last. 

Based on the results of the test stop see Notes 7 and 8) combine all the labeled fractions you wish to keep into one tube. Usually about four to five fractions are kept (which equals 400-500 pL m total),... 

Collect fractions and identify labeled peptide(s) by scintillation counting of 1/10 of each fraction. Monitor OD220 to assess the concentration of peptides in each fraction. As a rule of thumb, 1 nmol of a 10-mer peptide yields an OD220 of about 0.2 Thus, a peak of 0.002 OD contains 10 pmol of peptide, which should be sufficient for microsequencing However, it is advisable to work with OD peaks of about O.l-.Ol for a better sensitivity of the Edman-degradation reaction and detection of the phenylthioazolinone (PTH) denvatives of amino acids Lyophilize the labeled fraction(s) in glass tubes... 

In a colloidal dispersion, the geometric parameters of the system determining the sensitivity are the particle radius and the packing density. Additional influence is imposed by the NMR parameters such as the gyromagnetic ratio and the natural abundance (or labelled fraction, respectively) of the nucleus employed, and most importantly the width of the lines, which can vary over orders of magnitude leading to correspondingly decreased intensities for motionally restricted molecules. 

VAUGHAN D., CHESHIRE M.V. and MUNDIE C.M. 1974. Uptake by beetroot tissue and biological activity of 14c-labelled fractions of soil organic matter. Biochemical Society Transactions, 126-129. 

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