Densitometer scans, linear

Errors in sample application are among the most significant sources of inaccuracy. The technique of spotting can have a marked effect on delivery volumes between I and 5 pL. A constant slat ting zone size should be maintained so that a given amount of substance applied in the form of different volumes will yield spots with identical areas, whereas different amounts spotted at constant volume will exhibit a linear relationship in a plot of peak area (from recordings of densitometer scans) versus mass. 

Figure 9 Densitometer scans of 102-1016 ng of cholesterol standards and duplicate S- il aliquots of an egg yolk extract, made at an integrator attenuation setting of x8. The standard areas (shown below the peaks) had a linearity correlation (R value) of O.S>98, and the sample peak areas represent 12.8 (A) and 13.0 (B) mg of cholesterol per gram of yolk. Reproduced from Ref. 87.

For linear slit scanning densitometers it is well established that chromatographic resolution and sample -... 

As has been commented upon in other papers in this symposium, methods for measurement of intensities in fiber diagrams have received little attention in the last 15 years, during which time considerable progress has been made in handling the atomic coordinates for least squares refinement. Most intensity data has been obtained from linear densitometer traces through the x-ray reflections. We used these procedures for our work on cellulose I and 6-chitin. For cellulose I, (1 ) the area under the peak on a radial scan was determined after subtraction of an estimated Current addresses ... 

In addition to verifying the specificity of probes, the experiment in Fig. 1 also determines the range of sample concentrations in which a linear response is obtained for the probes. The autoradiograms are scanned with a densitometer equipped with an integrator to determine the peak areas for each slot. The peak areas are then plotted against the amount of RNA loaded per slot. A linear increase in peak areas is observed when between 0.1 and 0.75 fig of RNA is applied per slot. We find that the signal response is nonlinear above 1 fig per dot, suggesting that at this point filter-bound sequences are present in excess of the probe.19 Thus, quantitation is accu-... 

Quantification Zones were scanned at 222 nm with a dual-wavelength flying-spot densitometer standard curves were prepared by quadratic regression analysis, which gave a higher correlation coefficient than linear regression. 

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