Soluble ultracentrifuge studies

Nash AM and Wolf WJ. Solubility and ultracentrifugal studies on soybean globulins. Cereal Chem. 1967 44 183-192. 

Changes in the solubility, ultracentrifugal behavior, and number of SH groups in frozen myosin from trout were studied by Buttkus (71,72). 

The nature of molybdic acid in water and in acidified solutions has been studied by relatively few workers, JONES (1) proposed the existence of isopoly-cations of molybdenum to explain the solubility of molybdic acid in acid solutions. More recently, AVESTON, ANACKER, and JOHNSON (2) report ultracentrifuge studies of molybdic acid in hydrochloric acid medium. They find a degree of polymerization of about 3 in 0,8 M HCl, but note that equilibrium is not attained. On the other hand they find no aggregation and apparent equilibrium in 6 M HCl, No quantitative results were reported of experiments in HCIO medium. 

In our previous studies on the sulfate conjugation of phenols by fish livers, all the liver slices of the test fish and shellfish exhibited sulfate conjugation activities with phenol(14), and among various liver cell fractions separated by ultracentrifugation, only the soluble fraction displayed the sulfate conjugation activity for phenol and various phenolic compounds(15). 

Actomyosin. At high salt concentrations ( . . 0.6 M KC1), actin and myosin combine to form actomyosin filaments giving a highly viscous solution. Actomyosin retains the ATPase activity of myosin and demonstrates "super-precipitation" on the addition of ATP (24,34). As expected, there are differences between actomyosins of rabbit and fish with respect to solubility (10,22,35,36), viscosity (46) and ultracentrifugal behavior (477. Since actomyosin is the most readily available form of myofibrillar proteins from fish muscle, its behavior relative to deterioration during frozen storage has been most frequently studied. 

Cytochrome 62 is found as a soluble protein in the autolysates of Sac-charomyces cerevisiae. The crystalline preparations of Appleby and Morton 278) were shown to sediment as a single peak in the ultracentrifuge. Minimum molecular weight based on amino acid analysis and a heme extinction coefficient of 232 mM cm was calculated to be 53,000 283). The heme extinction coefficient was then corrected to 183 mM- cm-, and the minimum molecular weight per mole of heme recalculated to be 58,600 284). It was concluded that cytochrome 6 is a tetrameric structure. This conclusion agreed with the results of X-ray diffraction studies on type I and type II crystals, which indicated molecular weights of 235,000 10,000 and 234,000 8,000, respectively, for these two preparations of cytochrome 2 285). The oxidized and reduced spectral bands of cytochrome ba are given in Table XIV. 

This method allows for the accurate determination of K i only within the -1000 to +1000 region or approximately within six orders of magnitude span. These experiments could be complicated by solubility and equilibration kinetics and the properties of a substance. For example, if a studied compound has a property of nonionic surfactant, it will be mainly accumulated at the water-organic interface, and shaking of this two-phase system will create a stable emulsion difficult for analytical sampling. The ultracentrifugation at speed of 14,000 rpm for 15-20 min can be enough in most cases to separate two phases. Actual equilibration of the system is tested by several measurements of the equilibrium concentration at different time intervals. 

Here we describe studies of the interaction of interleukin-6 (IL-6) with a soluble form of its cell surface receptor (sIL-6R). A procedure utilising a competition approach is presented which allows the determination of the equilibrium constant in solution thus avoiding any potential problems associated with deviation in kinetic characteristics upon surface immobilisation. In addition, binding characteristics of stable monomeric and dimeric forms of IL-6 are presented to demonstrate both the drastic influence of solute multivalency on kinetic and equilibrium properties and the importance of auxiliary techniques such as analytical ultracentrifugation for the interpretation of SPR data. 

Spectroturbidimetry, conductimetry, ultrafiltration, ultracentrifugation, vapor sorption, polarizing microscopy, and nuclear magnetic resonance spectroscopy were used to study phase behavior of pure sodium 8-phenyl-n-hexadecyl-p-sulfonate in water as a function of temperature and sodium chloride concentration, and in decane. The first four techniques gave information on solubility and states of dispersion ranging from visible, settling suspensions to transparent, stably dispersed submicro-scopic particles. Surfactant solubility in water was only 0.06 wt% at 25°C, increased 11-fold at 90°C, but decreased 300-fold with 3 wt% salt at 25°C. The surfactant-rich phase in... 

The historical emphasis on the trinitrate ester as the derivative of choice for early experimental work on the SEC analysis of cellulose and cellulosics and the continued use of the trinitrate in this capacity are readily understandable. Cellulose nitrate was known to be soluble in organic solvents, and a mild method for its preparation with a high nitrogen content (approximately 13.4% N compared to 14.1% N theoretically) was reported (130). In addition, cellulose trinitrate was extensively used in previous studies of cellulose by viscometry, osmometry, ultracentrifugation, and fractional precipitation. Thus, SEC data could be readily compared with existing data for the trinitrate derivative. 

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