Ultracentrifuge, analysis

Fujita H (1975) Foundations of Ultracentrifugal Analysis. WUey, New York... 

With methods for the quantitative analysis of amino acids to hand, the way was now open for the determination of amino acid sequences. Purified bovine insulin was relatively freely available. On the basis of ultracentrifugal analysis (Gutfreund and Ogston), a molecular weight of 12,000 was assumed—as it later emerged, a factor of 2 too high. One of the advantages from the choice of insulin as the protein to sequence was that tryptophan is absent. A 100% recovery of the amino acids could therefore be obtained easily by simple hydrolysis with HC1. In 1948 Tristram reported the complete amino acid composition of the protein. 

The humates present in soil are polyelectrolytes and bear some similarity to polyacrylic acid and polymethacrylic acid (49, 50). The molecular weight distribution for the humates is considerable fulvic acid fractions of 1,000 daltons have been isolated (51) while humic acid molecular weights obtained by gel chromatography are in the range 17,000 to 100,000 daltons according to the type of soil from which it was extracted (52). However, ultracentrifugation analysis indicates a molecular range of 2,000 to 1,500,000 daltons for humic acids (55). 

Potl inhibitors differ from other protease inhibitors, and from all other defense peptides mentioned thus far, in their relative lack of disulfide bonds. This means that the loop with the reactive site is not fixed, as it is in the Bowman-Birk inhibitors, yet they still form a stable fold, as shown in Figure 11. An interesting feature of some Potl inhibitors is their tendency to form stable, noncovalently bound oligomers. This has, for example, been shown for chymotrypsin inhibitor I from tomato. This peptide has a monomer weight of 8300 Da under dissociating sodium dodecyl sulfate (SDS) gel conditions. Gel filtration and ultracentrifugal analysis revealed a... 

Fujita, H.Foundations of Ultracentrifugal Analysis (Chemical Analysis Series Monographs, Vol. 42) Wiley New York, 1975. 

Cathepsin D (from bovine spleen) [9025-26-7] [EC 3.4.23.5]. Purified on a CM column after ammonium sulphate fractionation and dialysis, then starch-gel electrophoresis and by ultracentrifugal analysis. Finally chromatographed on a DEAE column [Press et al. BJ 74 501 I960]. 

Ultracentrifugal analysis of Con A in solution revealed two components, the relative proportions of which depended on the experimental conditions. In Figure 6 (A), the Schlieren pattern of Con A at a concentration of 5 mg/ml in PBS at 5°C shows these two components. An s.. value of 5.52 S was obtained for the fast component and 4.15 S for the slower component. By comparing the relative areas under the peaks it was found that at this temperature 66% of the Con A molecules sedimented as the faster 5.52 S species. Higher temperatures favoured this species (Table II),... 

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