The solid-phase radioimmunoassay (RIA) method developed in our laboratory for demonstrating rubella virus-specific immunoglobulin G (IgG) antibodies (Kalimo et al., 1976) was further developed for demonstrating IgM antibodies. A total of 188 serum specimens were tested. The statistical probability of obtaining a false-positive IgM result, based on determinations of 100 rubella-negative sera, wa...

One way of improving the resolution of particles by size is to minimize the difference in RCF between the top and bottom of the sample. Practically this is achieved by layering the sample as a narrow band over a continuous density gradient. This is called rate-zonal gradient (sedimentation velocity) centrifugation; the conditions are chosen such that ρρ always remains greater than ρl. In a cont...

The role of T7-induced exonuclease (gene 6) in molecular recombination was studied by examining the fate of parental DNA during parental-to-progeny recombination. The method used was to compare infections with T7(+), T7am-6-233 (am gene 6), or T7ts6-136 (ts gene 6) under permissive and nonpermissive conditions. CsCl density gradient analysis of replicative DNA indicated that T7 exonuclease is n...

The density distribution of human mononuclear blood leukocytes was studied in order to define the optimal conditions for the separation of monocytes and lymphocytes by isopycnic centrifugation. Under standardized conditions, two populations of cells with partially overlapping, normally distributed densities were consistently found. The cells with the lowest density were recognized as monocytes,...

1. Some mucus glycoproteins form soluble complexes with lysozyme at neutral pH values. 2. The extent of complex-formation was determined, by an ultracentrifugal difference method, for a range of glycoproteins covering the common blood-group specificities. 3. Interaction was strongest with those glycoproteins of blood-group Lea specificity; these were also richest in sialic acid. 4. Interaction ...

A new method for the isolation of lipid droplets from rat liver has been devised. The procedure involves tissue homogenization and discontinuous density gradient centrifugation. Six discrete bands of lipid particles, rich in triglyceride and cholesterol, are visible following 30 min of centrifugation at 25,770 g (max) in a swinging bucket rotor. An entire rat liver can be processed in 1-2 hr. D...

Because of their intrinsic low buoyant density, chitosomes can be separated from crude cell homogenates (1000 g or 35,000 g supernatants) of Mucor rouxii by isopycnic sedimentation in sucrose density gradients. To accelerate and simplify the isolation of chitosomes, we centrifuged the cell-free extracts at ultrahigh speed (in a fixed-angle rotor at forces up to 311,000 g Rav) and found that the...

Synaptoneurosomes (SNs) are obtained after homogenization and fractionation of mouse brain cortex. They are resealed vesicles or isolated terminals that break away from axon terminals when the cortical tissue is homogenized. The SNs retain pre- and postsynaptic characteristics, which makes them useful in the study of synaptic transmission. They retain the molecular machinery used in neuronal si...

Späth, G. F. and Beverley, S. M. 2001. A lipophosphoglycan-independent method for isolation of infective Leishmania metacyclic promastigotes by density gradient centrifugation. Experimental Parasitology 99, 97–103. At the end of their growth in the sand fly, Leishmania parasites differentiate into the infective metacyclic promastigote stage, which is transmitted to the mammalian host. Thus, in ...

The isolated, formaldehyde-fixed nucleoid of E. coli has been analyzed by isopycnic centrifugation in CsCl density gradients. The membrane-free nucleoid bands at a density of 1.69 +/- 0.02 g/cm3. The membrane-associated nucleoid bands at a density of 1.46 +/- 0.02 g/cm3. Both species sediment to equilibrium as nearly monodisperse bands in CsCl, suggesting that the nucleoid components of DNA, RN...