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Albumin, denaturation

Heat, strong acids or bases, ethanol, or heavy-metal ions irreversibly alter the secondary structure of proteins (see below). This process, known as denaturation, is exemplified by the heat-induced coagulation and hardening of egg white (albumin). Denaturation destroys the physiological activity of proteins. [Pg.487]

The temperature for salting out need be only as high as is required to prevent crystallization of the salt (R16). For 1.8 M sodiiun sulfate and 2.1 Af sodium sulfite the minimum working temperature is 25°C. A mixture of sulfate and sulfite has been proposed (R7), but solubility is not appreciably increased and the mixture still requires storing in a warm place, i.e., above 25°C, to prevent crystallization. In practice, sulfite holds no advantage over sulfate when a 37 C incubator for storing the concentrated solution is available. Warm sulfite solutions also deteriorate and must be made fresh every week (L8). Furthermore, sulfite increases the danger of albumin denaturation by ether, while sulfate has a protective influence (B31, S4). [Pg.240]

Owing to the low temperature requirement, this type of method has not been extensively used or investigated for quantitative microanalysis. It should be noted, however, that the albumin separation is satisfactory even when the temperature during filtration rises as high as 7°C (PIO). Careful control at temperatures below zero is demanded for the ethanol fractionation scheme of Cohn et al. (C14). The higher dielectric constant of methanol undoubtedly renders the earlier method less sensitive to small changes in the many variables—temperature, molarity, pH of buffer, concentration of solvent and serum— and less likely to be adversely affected by albumin denaturation. ... [Pg.241]

Furthermore, polarization time and electrode type are responsible for the number of reducible disulfide groups (Table 1). For instance at the d.m.e. only the two interstrand disulfide bridges A7—B7 and A20—B19 of insulin are split at -0.6 V vs. SCE, whereas in the case of albumin s only 4 out of the 16 disulfide bridges are broken. At the stationary electrode (h.m.d.e.) about 3 disulfide bridges in insulin and 9 in albumin are broken. Albumin denatured by 8 M urea shows practically the same result, which means that... [Pg.192]

Weber and Laurence (1953) have described a series of substances that although completely nonfluorescent in water solution become strongly fluorescent on adsorption by native serum albumin, denatured ovalbumin, filter paper, or alumina. They are also spontaneously fluorescent in certain solvents. These substances are derivatives of 3-chloro-6-meth-oxy-9-aminoacridine or of one of several aminonaphthalene sulfonic acids, in which one of the amino hydrogens has been substituted by a benzene ring derivative. The explanation of the behavior on adsorption lies apparently in that the radiative transition is forbidden for the nonplanar molecule but is allowed when the molecule lies on a plane as it presumably does on adsorption. This is extensively discussed by Forster (1951). Although the causes of the phenomenon are interesting in themselves, its practical applications may be of importance. Laurence and Rees (1953) have developed a method for the rapid and accurate determination of albumin in blood serum by fluorimetry using 1 N phenyl-aminonaphthalene-5 sulfonic acid. The detection of ovalbumin dena-turation by this method also deserves consideration. The appearance of fluorescence on adsorption of auramin O by nucleic acids has been described by Oster (1951). [Pg.456]

Lipoproteins may denature on heating and if present during pasteurization can result in the formation of haze or turbidity in the final product. This material was removed traditionally by filtration through asbestos (qv) sheets (6) however, health hazards associated with asbestos have led to its replacement by alternative filter materials (23,37,193). These media have been less effective than asbestos and further measures have been required to ensure the visual clarity of albumin products, eg, further filtration developments for Hpid removal (194), preferential denaturation of contaminants using in-process heat treatment, and anion-exchange chromatography (49). [Pg.533]

Casein. Milk contains proteins and essential amino acids lacking in many other foods. Casein is the principal protein in the skimmed milk (nonfat) portion of milk (3—4% of the weight). After it is removed from the Hquid portion of milk, whey remains. Whey can be denatured by heat treatment of 85°C for 15 minutes. Various protein fractions are identified as a-, P-, and y-casein, and 5-lactoglobulin and blood—semm albumin, each having specific characteristics for various uses. Table 21 gives the concentration and composition of milk proteins. [Pg.370]

Denaturation is accompanied by changes in both physical and biological properties. Solubility is drastically decreased, as occurs when egg white is cooked and the albumins unfold and coagulate. Most enzymes also lose all catalytic activity when denatured, since a precisely defined tertiary structure is required for their action. Although most denaturation is irreversible, some cases are known where spontaneous renaturation of an unfolded protein to its stable tertiary structure occurs. Renaturation is accompanied by a full recovery of biological activity. [Pg.1040]

FIGURE 9.6 DSC of (a) recombinant resilin in water showing no enthalpic events, (b) bovine serum albumin in phosphate-buffered saline (PBS) showing denaturing occurring at 62°C, and (c) wool fiber in water showing denaturing of the a-helix at 145°C (Endotherm up). [Pg.261]

Structured proteins have also been investigated by thermal analysis [40,41], denaturing resulting in an endotherm which is readily detected by differential scanning calorimetry (DSC). DSC of recombinant resilin in the swollen state showed no transitions over a wide temperature range (25°C-140°C), further evidence of the absence of any strucmre. This is in contrast to the strucmred proteins wool and bovine serum albumin, which show denamration endotherms at 145°C and 62°C, respectively (Figure 9.6). [Pg.261]

The preparation of microspheres can be accomplished by either of two methods thermal denaturation, in which the microspheres are heated to between 95 and 170°C, and chemical crosslinking with glutaraldehyde in a water-in-oil emulsion. Well-defined microspheres can be easily prepared using these methods in large batches which are usually physically and chemically stable. Newer preparation methods for the preparation of albumin microspheres have been described by several authors (84-88). [Pg.240]

Apart from its natural occurrence, Co may find its way into other proteins either adventitiously or deliberately. A study was undertaken where the blood, serum, and plasma of workers occupationally exposed to Co were analyzed for the element.1189 When separated by gel electrophoresis under denaturing conditions, the Co fractions in all blood, serum, and plasma samples showed a similar protein pattern. A variety of proteins of differing size were found to bind Co in fractions collected at pFl 5, whereas only hemoglobin was found in the pH 7 fractions. The conclusions were that in vivo Co is bound to plasma proteins, perhaps albumin and hemoglobin. [Pg.107]


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See also in sourсe #XX -- [ Pg.219 , Pg.220 ]

See also in sourсe #XX -- [ Pg.472 , Pg.473 ]




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