Serums, viscosity measurement

Serum viscosity measurements are best performed using a Wells-Brookfield viscometer, which permits measurements at different shear rates and variable temperatures (K36). These measurements are warranted when monoclonal IgM concentrations exceed 40 g/L or when IgA or IgG levels exceed 60 g/L. 

This method is an adaptation of the Basic Protocol for measuring the viscosity of pure liquids and solutions. The °brix (unithi.4) of the sample is adjusted to a desired value by dilution. In many protocols, a nominal value of 5 °brix is the accepted target value for dilution. The sample is then filtered to remove particles that would plug the capillary tube of the viscometer, and the serum viscosity is measured in a Cannon-Fenske viscometer. 

In the food industry it has often been difficult to obtain true viscosity measurements (unithj.j) of complex fluid foods such as coarse fruit suspensions. These are usually non-Newtonian suspensions. Fruit concentrates are dispersions of solid particles (pulp) in aqueous media (serum). Their rheological properties are of interest in practical applications related to processing, storage stability, and sensory properties. Expensive rheometers are often not available in quality control and product development laboratories. However, viscosity is nonetheless an important quality factor of these products. 

Guidelines for clinical and laboratory evaluation of patients with monoclonal gammopathies have been proposed (K7). These proposals address in addition electrophoretic, immunofixation, and quantitative techniques for measurement of M protein, and also provide guidelines for serum viscosity and cryoglobulin measurements. 

Since the original description by Waldenstrom, it has become clear that this syndrome is not confined to raacroglobulinemia, and so it is better called viscosity syndrome. It has been found in some 4% of IgG-inyelomatosis H22), occasionally with IgA paraprotein and even with Bence Jones proteinemia, usually due to polymerization [reviewed by Somer (S19)], and it is also recorded with IgE (01). With regard to viscosity syndromes due to paraproteins the relevant abnormality is detected in viscosity measurements on either whole blood, plasma, or serum (S19) the latter is the most convenient. This is not the case in polycythemia, etc. (W5). 

N3. Neurath, H., and Saum, A. M., The denaturation of serum albumin Diffusion and viscosity measurements of serum albumin in the presence of urea. J. Biol. Chem. 128, 347-362 (1939). 

Masuelli M. A. 2013. Study of bovine serum albumin solubility in aqueous solutions by intrinsic viscosity measurements. Ady hy Chem., 2013, Article ID 360239, 8 pages. 

As an example of the different results which are obtainable by the two procedures, we shall consider data on urea-denatured horse serum albumin. These data were obtained from parallel diffusion and viscosity measurements in solvents containing various amounts of urea (Neurath and Saum, 1939). The intrinsic viscosity increased and the diffusion coefficient decreased with increasing urea concentration. The value of w (and, therefore, 7,) was arbitrarily fixed. This then permitted a calculation of p to be made from a single hydrodynamic measurement since the value of 7 was assumed known at each concentration of urea. Thus, p was computed from V, determined from an equation equivalent to Eq. (1-3), using the viscosity data. An independent value of p was computed from 1/f, determined from Eqs. (I-IO) and (I-ll), using the diffusion data. The values of the dimensions computed from the viscosity and from the diffusion data are shown in Table IV. 

Viscosity measurements by Neurath and Putnam (101) have verified the existence of interaction in protein-detergent mixtures and have revealed a unique dependence of the viscosity increment on detergent/ protein weight ratio. This work showed that both cationic and anionic detergents produce a large increase in the relative viscosity of serum... 

After purification by molecular distillation, the monomer was polymerized in bulk, at slightly elevated temperatures. Typically, 250 to 300 mg of monomer were placed in a dry test tube under nitrogen, sealed with a serum cap, and the initiator was added as a solution in diethyl ether. The polymerization was conducted under a positive pressure of dry, deoxygenated nitrogen, and excess diethyl ether was entrained. After the specified period of time had elapsed, the reaction mixture was dissolved in chloroform and the polymer was precipitated from petroleum ether F as a sticky, resinous solid. Viscosity measurements were made on chloroform solutions at 25 . 

Capillary viscometers are ideal for measuring the viscosity of Newtonian fluids. However, they are unsuitable for non-Newtonian fluids since variations in hydrostatic pressure during sample efflux results in variations in shear rate and thus viscosity. This unit contains protocols for measuring the viscosity of pure liquids and solutions (see Basic Protocol) and serums from fruit juices and pastes (see Alternate Protocol). 

However, they may not indicate the true bulk viscosity of a suspension that forms a thin layer of the continuous phase (e.g., serum of tomato juice) around the immersed probe or when the probe is covered by a higher viscosity gel due to fouling. Vibrational viscometers are suitable for measuring viscosities of Newtonian fluids, but not the shear-dependent rheological behavior of a non-Newtonian fluid (e.g., to calculate values of the power law parameters). 

Paraproteinaemia poses a special problem, since an increased viscosity may be measured both in whole blood and in serum or plasma. Paraproteinaemia occurs in Waldenstrom s disease (osteochondrosis of the capital femoral epiphysis), in multiple myeloma or non-Hodgkin lymphoma. Samples taken from these patients may reveal a change in flow properties due to viscosity. A change in the flow properties, however, will slow down the penetration of the sample material into the reagent layers so that the reaction can take place only with some delay. This results in analysis data that are too low. If the sample material (serum or plasma) is diluted, as in the case of the Seralyzer system, these problems are absent. 

The compression or decompression of bovine serum albumin monolayers spread on an aqueous substrate at a pH near the isoelectric point can effect surface tension. The surface pressure changes depend on the distance between the position of the surface pressure measuring device and the compression barrier. This effect is minimal at a pH above or below the isoelectric point and undetected for small molecules (myristic acid and eicosyl sodium sulfate) even when the substrate contains substituted alkyl amines. A theory is proposed which attributes the above observation to surface drag viscosity or the dragging of a substantial amount of substrate with the BSA monolayer. This assertion has been experimentally confirmed by measuring the amount of water dragged per monolayer using the technique of surface distillation. 

Figure 1 Shear-induced aggregation of bovine serum albumin (BSA), ovalbumin (OV) and /3-lactoglobulin (BLG) in aqueous solution. Viscosity of the solutions was measured against time under a steady shear rate (10"3 s 1 for BSA, 6.3 10 3 s 1 for OV, and 10 4 s-1 for BLG). Solvent 0.1 M NaCI, pH 7, 20°C. The concentrations of the solutions were 0.75%, 1.25%, and 1.5% for BSA, OV, and BLG, respectively. (Replotted from Refs. 28 and 29.)...

Earlier FAAS techniques for measuring serum copper levels which included protein precipitation with trichloroacetic acid (Olson and Hamlin, 1968) and/or solvent extraction have been superseded by simpler procedures using either large sample dilution or viscosity adjusted reference solutions with minimal dilution. The analyses are made mainly using continuous nebulization, discrete sample injection or by flow injection techniques with little advantage gained from flame adaptors to increase sensitivity. 

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