No abstract

No abstract

The effect of pH on plant protease activity was investigated ysing bufered, gamma-irradiated aqueous extract of ryegrass Lolium multiflorum. Rapid protein breakdown occurred in the first f e w days but was followed by a longer period of reduced activity. The overall pH optimum for ryegrass proteases was between 5.0 and 7.0 but there was still considerable activity at the acid pH levels found, eg in silage. Proteolysis did not proceed to completion even when the pH was not inhibiting.

Summary Radioimmunoassay techniques involve counts of radioactivity of fractions of labelled samples. For potency estimation, account must be taken of dependence of variance of count on expectation of count, the variance usually being substantially greater than Poissonian. The paper is concerned with maximum likelihood estimation of the variance function, using either a quadratic or an exponential model. Only two parameters are of interest, but hundreds of nuisance parameters may be present. The numerical example that illustrates the technique of estimation shows a poor fit: the reasons are discussed, as also are reasons for regarding the estimated function as useful.