Search PubMed⌕ Search

Biomedical subjects

S J Hayes

Publications and source records attributed to S J Hayes.

44 records · Page 3Linked to original sources
PubMed1986

Exclusion of spheres by agarose gels during agarose gel electrophoresis: dependence on the sphere's radius and the gel's concentration.

Agarose gel electrophoresis of spheres (radius = R) has been used to determine the effective radius (PE) of the pores of an agarose gel (percentage of agarose in a gel = A). The value of PE at a given A was taken to be the R of the largest sphere that enters the gel. When log PE is plotted as a function of log A, the results can be represented by: PE = 118A-0.74 for 0.2 less than or equal to A less than or equal to 4.0 (PE in nm). However, the data suggest significant nonlinearity in this plot, the magnitude of the exponent of the PE vs A relationship increasing by about 20% as A increases from 0.2 to 4.0. From these data, PE's as big as 1500 nm and as small as 36 nm can be achieved with agarose gels formed with unmodified, unadulterated agarose and usable for electrophoresis.

Electrophoresis↗
PubMed1985

Heterogeneity of the procapsid of bacteriophage T3.

Like other double-stranded DNA bacteriophages, bacteriophage T3 assembles a DNA-free procapsid that subsequently packages the bacteriophage DNA. By agarose gel electrophoresis, it has been found that the T3 procapsid has a negative electrophoretic mobility (mu) that progressively increases in magnitude by as much as 3% after assembly of the procapsid. This increase is (i) caused by an increase in the solid support-free mu (muo) of the procapsid, not a decrease in its radius, and (ii) not prevented by either genetically or chemically (use of proflavine) blocking DNA packaging. However, inhibition of the formation of high-energy compounds with a mixture of cyanide and fluoride ions does block the time-dependent increase in the magnitude of muo. This increase appears to be accompanied by addition of an unidentified T3 protein to the procapsid.

Capsid↗
PubMed1983

Comparison of the physical properties and assembly pathways of the related bacteriophages T7, T3 and phi II.

To understand constraints on the evolution of bacteriophage assembly, the structures, electrophoretic mobilities (mu) and assembly pathways of the related double-stranded DNA bacteriophages T7, T3 and phi II, have been compared. The characteristics of the following T7, T3 and phi II capsids in these assembly pathways have also been compared: (1) a DNA-free procapsid (capsid I) that packages DNA during assembly; (b) a DNA packaging-associated conversion product of capsid I (capsid II). The molecular weights of the T3 and phi II genomes were 25.2 X 10(6) and 25.9 (+/- 0.2) X 10(6) (26.44 X 10(6) for T7, as previously determined), as determined by agarose gel electrophoresis of intact genomes. The radii of T7, T3 and phi II bacteriophages were indistinguishable by sieving during agarose gel electrophoresis (+/- 4%) and measurement of the bacteriophage hydration (+/- 2%) (30.1 nm for T7, as previously determined). Assuming a T = 7 icosahedral lattice for the arrangement of the major capsid subunits (p10A) of T7, T3 and phi II best explains these data and data previously obtained for T7. At pH 7.4 and an ionic strength of 1.2, the solid-support-free mu values (mu 0 values) of T7, T3 and phi II bacteriophages, obtained by extrapolation of mu during agarose gel electrophoresis to an agarose concentration of 0 and correction for electro-osmosis, were -0.71, -0.91 and -1.17(X 10(-4) cm2V-1 s-1. The mu 0 values of T7, T3 and phi II capsids I were -1.51, -1.58 and -2.07(X 10(-4] cm2V-1 s-1. For the capsids II, these mu 0 values were -0.82, -1.07 and -1.37(X 10(-4] cm2V-1 s-1. The tails of all three bacteriophages were positively charged and the capsid envelopes (heads) were negatively charged. In all cases the procapsid had a negative mu 0 value larger in magnitude than the negative mu 0 value for bacteriophage or capsid II. A trypsin-sensitive region in capsid I-associated, but not capsid II-associated, T3 p10A was observed (previously observed for T7). The largest fragment of trypsinized capsid I-associated p10A had the same molecular weight in T7 and T3, although the T3 p10A is 18% more massive than the T7 p10A. It is suggested that the trypsin-resistant region of capsid I-associated p10A determines the radius of the bacteriophage capsid.

Capsid↗
PubMed1982

Detection and characterization of agarose-binding, capsid-like particles produced during assembly of a bacteriophage T7 procapsid.

It has previously been shown that: (i) during infection of its host, the DNA bacteriophage T7 assembles a DNA-free procapsid (capsid I), a capsid with an envelope differing physically and chemically from the capsid of the mature bacteriophage, and (ii) capsid I converts to a capsid (capsid II) with a bacteriophage-like envelope as it packages DNA. Lysates of phage T7-infected Escherichia coli contained a particle (AG particle) which copurified with capsid II during buoyant density sedimentation, velocity sedimentation, and solid support-free electrophoresis, but was distinguished from capsid II by its apparent diversity during electrophoresis in agarose gels. Treatment of AG particles with trypsin converted most of them to particles that comigrated with trypsin-treated capsid II during electrophoresis in agarose gels. Irreversible binding of AG particles to agarose gels was shown to contribute to the apparent diversity of AG particles during agarose gel electrophoresis. The results of quantitation of AG particles and of capsid I and capsid II in lysates of a nonpermissive host infected with T7 amber mutants suggested that, in site of their capsid II-like properties, most AG particles were produced during assembly of capsid I and not during DNA packaging. The presence of AG particles in T7 lysates explains contradictions in previous data concerning the pathway of T7 assembly.

Capsid↗
PubMedDate not supplied

Discontinuous genetic variation among mesophilic Naegleria isolates: further evidence that N. gruberi is not a single species.

Naegleria isolates which are currently placed in the type species N. gruberi display great genetic, physiological and morphological heterogeneity. There are two possible interpretations of the nature of this species--that N. gruberi is a species complex or that it is a single continuously variable species. To distinguish between these alternatives, allelic states were determined for 33 loci in 74 new isolates selected to represent wide geographic sources and diverse temperature limits for growth. The results were compared with data for culture collection strains of N. gruberi and other species in the genus. The isolates formed a discontinuous series of clusters, separated by genetic distances similar to those separating the better-characterised taxa N. fowleri, N. lovaniensis, N. jadini, N. australiensis australiensis and N. australiensis italica. Culture collection strains assigned to N. gruberi fell into six distinct clusters, while other clusters were not represented by reference strains. The data are most consistent with the interpretation that N. gruberi is a group of several distinct species, each equivalent to the recently described species in the genus. Naegleria andersoni andersoni and N. andersoni jamiesoni also formed two distinct clusters, equivalent to species. Characteristics temperature limits for growth show that the mesophilic species are ecological as well as genetic entities.

Alleles↗