1. Osmotic pressure determinations of dissociated arachins are a particularly suitable method for determination of the number of sub-units in the protein, because they yield a number-average molecular weight. 2. Arachin, in 8m-urea-0.1m-sulphite, produces 12 sub-units from the form of molecular weight 345000. 3. When the urea concentration is varied the molecules became fully dissociated at 6m-urea-0.1m-sulphite. Although sulphite is necessary to break disulphide bridges, concentrations greater than 0.1m cause a re-aggregation of the sub-units. Similar results were obtained in guanidine solutions. 4. A new form of arachin has been discovered, A1, migrating more rapidly than arachin A. 5. The N-terminal residues of arachin have been re-investigated on more highly purified samples: they are glycine, valine and (iso)leucine in the proportions 4:1:1. 6. The three forms of arachin have the structure (B) beta(4)gammadelta, (A) alpha(2)beta(2)gammadelta and (A1) alpha(4)gammadelta, for the forms of molecular weight 170000. 7. Dissociation in 8m-urea produces some fragments, detected by gel electrophoresis, which appear to be dimers of the type alpha-S-S-beta, beta-S-S-beta, held together by disulphide bonds.

A simple, convenient method is described for the detection in human urine of three major classes of drugs of abuse: amphetamines, barbiturates, and alkaloids. The drugs are adsorbed from urine by a column of non-ionic resin (Amberlite XAD-2), eluted with methanol, and chromatographed on a thin-layer silica gel plate. The drugs are made visible and identified by a series of procedures involving exposure to ultraviolet radiation, heat treatment, sequential spraying with group-specific reagents, and measurement of Rf values. Detection limits for 5-ml urine specimens are: 0.4 µg per ml for amphetamines and barbiturates, and 0.8 g per ml for alkaloids. The test requires 6 h to perform. One technologist can process 50 specimens per day.

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A simple microfluorometric method is described for measuring glucose-6-phosphate dehydrogenase (GPD) and 6-phosphogluconate dehydrogenase (PGD) activities in human erythrocytes. Only 50 µl of whole blood is required. The cells are lysed with digitonin and the rate of NADPH generated in the enzymatic reactions is followed kinetically with a recording fluorometer. GPD activity is measured by subtracting the PGD activity from the combined activities of GPD and PGD. A correction is made for the quenching effect caused by hemoglobin. The entire analysis requires less than 1 h. No significant sex-related difference was observed. Both enzymes are stable at 30°C for seven days in samples collected either with heparin or in Alsever’s solution.