Globulin behavior

Early ultracentrifuges were extremely expensive and were therefore located in only a small number of laboratories. Nevertheless, rapid strides were made in the theory and practice of ultracentrifugation. By 1940 the behavior of proteins with molecular weights ranging from that of cytochrome c (13.4 kDa) to serum globulin (ca.170 kDa) had been studied. 

Some 100 different proteins occur in human blood plasma. Based on their behavior during electrophoresis (see below), they are broadly divided into five fractions albumins and ai-, tt2-, P- and y-globulins. Historically, the distinction between the albumins and globulins was based on differences in the proteins solubility -albumins are soluble in pure water, whereas globulins only dissolve in the presence of salts. 

Figures 7.20a-b show the physical/chemical states of soy globulins (7S and IIS soy globulins, respectively) as a function of moisture content and temperature. At low temperatures and at low moisture contents, the soy globulins are in the glassy state. Above the glass transition, a rubbery region is observed. Comparison of the glass transition behavior of 7S and 1 IS globulins shows that the transition of 1 IS globulin...

With several other proteins, such as bovine serum albiunin (Tanford and Roberts, 1952), lysozyme (Tanford and Wagner, 1954), and/3-lacto-globulin (Tanford and Swanson, 1957), pK shifts of the phenolic OH groups of tyrosine residues are observed, but these are of a qualitatively different nature. Thus, the tyrosines of any one of these proteins cannot be readily differentiated into a normal and an abnormal variety, since the spectrophotometric titration data for these proteins are reversible and fall on single smooth curves, in contrast to the situation with RNase. On the other hand, the tyrosine residues of ovalbumin show comparable behavior to the three abnormal tyrosine groups of RNase (Crammer and Neuberger, 1943). About 2 of the total of 9 tyrosine residues appear to titrate normally, but the remainder are not titrated up to pH 12. At pH 13, these anomalous tyrosines become titratable, and this is accompanied by the irreversible denaturation of the ovalbumin molecule. 

A great number of proteins have been purified on Sephadex G-75 (Bjork and Porath, 1959 Hanson and Johansson, 1960 Pr aux and Lontie, 1961 Bjork, 1961 Palmstierna, 1961 Ames et al., 1961 Pettersson et al., 1962). Considerably improved gel types have been introduced recently thanks to pioneering work by Flodin. These gel substances, named Sephadex G-lOO and G-200, are produced in the form of spherical beads. They can be packed in beds with excellent filtering properties this is particularly true for G-100. The behavior of serum proteins has been studied by Flodin and Killander (1962). As is seen in Fig. 6, 7 S and 19 S 7-globulins can be separated on Sephadex G-200. 

The Behavior of Albumin in Plasma at the Oxidized Silicon Surface. A chance for albumin to be adsorbed out of plasma, not yet encountered on any of the materials tested, could be provided by removing fibrinogen and some globulins from competition. Some normal intact plasma was... 

Equilibrium spreading pressures (iTe) of proteins and LMWE at the air-water interface as a function of pH and temperature were also studied (Patino and Martin, 1994 Nino et al., 2001,2005). The equilibrium spreading pressure is a measure of the surface activity of spread films at equilibrium. The magnitude of He was dependent on the emulsifier and on the aqueous phase composition. Eor example, the minimum for 7 and 11S soy globulin fractions at pH 5 as compared with Tig on aqueous solutions at pH different to pi can be explained by the fact that the protein is more difficult to convert into a monolayer at its isoelectric point. This behavior is not observed for globular milk proteins (like WPl). 

C. Attempts to Correlate Conformational Changes and Surface Behavior of the Succinylated 11-S-Globulins Cruciferin and Legumin... 

Cyclic Voltammetry—5 V/min. Figures la-e present the j-U behavior for the first cycle of copper-2% zinc in phosphated saline and in protein solutions. The corrosion potentials (ia—ic) during the forward scans were between -0.35 to -0.40 V in all cases. Two anodic peaks were observed for all protein solutions at —0.25 to —0.10 V and +0.10 to +0.30 V. The first peak in the supporting electrolyte was also observed, whereas j continued to increase, never reaching a peak up to the reversal potential of +0.5 V. Two main cathodic peaks were observed at —0.30 to —0.45 V and —0.65 to —0.75 V in all cases. A prepeak inflection also occurred at -0.2 to -0.3 V for both the albumin and globulin systems, and a small peak at —1.1 to —1.2 V for most systems. Cathodic currents increase sharply below about —1.5 V. Figures 2a-b represent the surface appearances after the first cycle of polar-... 

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