Ultracentrifugation tests

Scotch-tape test [13,16-20] Abrasion test [18,21] Bend and stretch test [15,22] Shearing stress test [22-24] Direct pull-off method [15,25-39] Moment or topple test [40-43] Electromagnetic tensile test [44] Laser spalation test [45] Ultracentrifuge test [13,22,46-50] Ultrasonic test [13,76] Peeling test (13, 51-54] Tangential-shear test [55,56] Scratch test [50,52, 57-73]... 

The microcentrifuge test may also be used in conjunction with an ultracentrifuge test to generate additional size separation data, allowing separation of drug in nanoparticles from free drug and drug partitioned into bile salt micelles. 

Each interferon preparation was ultracentrifuged at 20,000 revolutions per minute for one hour to remove tissue debris and inactivated virus. The supernatant was dialyzed against distilled water (1 400) for 24 hours at4°C. The material was then freeze-dried. The dried product was reconstituted in one-tenth of the original volume in distilled water and dispensed into ampoules. Reconstituted solutions were assayed for interferon activity, examined for toxicity, and tested for sterility. 

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). 

Our approach utilized the metals gold, platinum, then later gold, platinum, and nickel electroplated in succession because the catalytic decomposition of hydrogen peroxide reaction we tested was most efficiently catalyzed with platinum.After fabrication of the nanowires they were freed by removing the conductive silver backing with nitric acid and the sacrificial template with a strong base, sodium hydroxide. Then nanorods were washed with deionized water and ultracentrifuged to achieve a neutral pH. 

To test this hypothesis, very low density lipoprotein (VLDL, d<1.0 gm/ml), low density lipoprotein (LDL, d=l.02-1.063) and high density lipoprotein (HDL, d=l.09-1.21) were isolated from outdated human plasma by ultracentrifugation according to established procedures (27,28), using potassium bromide for density adjustments and stored at -20° C in the presence of 20% sucrose before use. The purity of individual lipoprotein fractions thus obtained was established by polyacrylamide gel electrophoresis in sodium dodecyl buffer system (2 ) and filtration through a Sepha-rose 6B column, equilibrated with 0.2 M potassium bromide in 0.1 M sodium phosphate buffer, pH 7.2. Protein (30) and cholesterol... 

The sedimentation constants and molecular weights calculated from ultracentrifugation data for both types of antibodies were 7s and 150,000 respectively. Agar diffusion tests with goat antisera against rabbit IgA, IgG and IgM showed that both antibody sets are of the IgG immunoglobulin type (29). 

Autosampler vials are available in different sizes, shapes, and materials. In terms of volume, vials from 300-/al ultracentrifuge tubes to 25-ml glass test tubes exist. For analytical work the standard autosampler vials are from 1 to 4 ml. Smaller vials, known as limited volume inserts, which fit inside the standard vials, are also available when the sample size is limited. 

Depending on the available ultracentrifuge different relative centrifugation forces have been used, ranging from 120000 g up to 436000 g (Nakai et al. 2003). Depending on the affinity of the test substrate for nonspecific binding different material of ultracentrifuge tubes can be applied. 

Fig. 3.15. Analytical size-exclusion chromatography distinguishes between dimeric and monomeric chorismate mutases [97]. Wild-type MjCM (top trace) was found to be a mixture of dimer and higher-order aggregates. Most selected variants (e.g. traces A, B and C) were dimers or mixtures of dimers and monomers. Only oneof26 variants tested (mMjCM, bottom trace) eluted as a monomer. It had the six amino acid insert shown. Analytical ultracentrifugation confirmed that this protein is monomeric in solution.

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. 

In a round-robin test series Mueller [81] found the ultracentrifuge to be the most satisfactory size analysis method for the sub-pm range a sample containing nine monodisperse components with 10% diameter difference being resolved. 

Table IV. Ultrafiltration (UF) and ultracentrifugation (UC) tests of surfactant solubility and particle size of surfactant-water systems, which were stirred well and allowed to settle for two days at 25°C.

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