CLINICAL LAB SCIENEC

CHAPTER 14: CLINICAL CHEMISTRY 369
determining the level of protein. Plasma has an abundance of fibrinogen that will
affect the results of a total protein determination.
Total protein determinations test simultaneously for both albumin and globulin
through a dye-binding procedure. Albumin, which comprises more than one-half
of the total protein value, is often measured in a second and separate test. The difference
between the total protein and the albumin is roughly equal to the globulin
value. Albumin is important in maintaining fluid balance within the body, while
globulin includes antibodies, blood coagulation proteins, and proteins that transport
elements such as iron throughout the body. The ratio among these major proteins
will be altered in diseases that affect the functions of the liver, where albumin is
synthesized.
In this procedure, the student will perform a serum total protein determination by
using a simple dye that colors the protein molecules. The intensity of the color is proportional
to the level of protein in the sample. This type of reaction is called an endpoint
colorimetric determination (Figure 14-1). The color development is proportional
to the absorbance level.
The Stanbio Total Protein Method is available as a simple test kit that will
enable the student to perform a totally manual method for protein. The kit contains
both the standards and the reagent for the quantitative colorimetric determination
of total protein in serum or plasma. In addition to the reagents provided in the kit,
a spectrophotometer capable of absorbance readings at 500 nanometers (nm) is
needed.
Y
.7
.6
.5
Absorbance
.4
.3
.2
.1
0
0 5 10 15
Hemoglobin concentration (g/dl)
20
X
FIGURE 14-1 The graph shows a typical end-point reaction observed
in a variety of chemistry procedures.
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