Characteristics of φT, the Temperate Bacteriophage Carried by Bacillus megaterium 899a

Phage T was the only phage observed in lysates of Bacillus megaterium 899a induced with mitomycin C, 0.35 mug/ml. The phage adsorbed slowly to its host in nutrient agar, giving rise to plaques of varying sizes and turbidity. Only clear plaques were observed when the phage and host cells were preincubated in an adsorption buffer and plated under optimum conditions. Plaque turbidity was caused by either the addition of 0.5 x 10(-2) to 1.0 x 10(-2) M CaCl(2) to the phage assay medium, or by raising the incubation temperature to 34 C. Phage T purified on a CsCl gradient had a density of 1.48 g/ml in CsCl and the extracted phage DNA had a buoyant density in CsCl of 1.6975 g/ml, equivalent to 38.2% guanine plus cytosine. The phage was rapidly inactivated at 75 C and was unstable in the presence of chloroform at 4 C, but it was stable in buffer stored in ice. When stage I sporulating cells were induced with mitomycin C, phage were carried into spores which when germinated lyse with the release of phi T. The burst size on induction of early-log vegetative cells was 52, whereas the burst size of induced T(0) sporulating cells, diluted in fresh medium, was 47 for a sporulating strain and 140 for an asporogenous mutant. A typical phage T had a long, noncontracting tail 240 nm long, 9 to 11 nm wide, with a repeating disk unit along the tail, 4 nm in size center to center. The tail ended in a small disk (15 nm wide) which is presumably for attachment to the host. The hexagonal head measures 68 by 57 nm and is composed of donut-shaped units 9 nm in diameter.     

Assembly of bacteriophage T7. Dimensions of the bacteriophage and its capsids.

The dimensions of bacteriophage T7 and T7 capsids have been investigated by small-angle x-ray scattering. Phage T7 behaves like a sphere of uniform density with an outer radius of 301 +/- 2 A (excluding the phage tail) and a calculated volume for protein plus nucleic acid of 1.14 +/- 0.05 x 10(-16) ml. The outer radius determined for T7 phage in solution is approximately 30% greater than the radius measured from electron micrographs, which indicates that considerable shrinkage occurs during preparation for electron microscopy. Capsids that have a phagelike envelope and do not contain DNA were obtained from lysates of T7-infected Escherichia coli (capsid II) and by separating the capsid component of T7 phage from the phage DNA by means of temperature shock (capsid IV). In both cases the peak protein density is at a radius of 275 A; the outer radius is 286 +/- 4 A, approximately 5% smaller than the envelope of T7 phage. The thickness of the envelope of capsid II is 22 +/- 4 A, consistent with the thickness of protein estimated to be 23 +/- 5 A in whole T7 phage, as seen on electron micrographs in which the internal DNA is positively stained. The volume in T7 phage available to package DNA is estimated to be 9.2 +/- 0.4 x 10(-17) ml. The packaged DNA adopts a regular packing with 23.6 A interplanar spacing between, DNA strands. The angular width of the 23.6 A reflection shows that the mean DNA-DNA spacing throughout the phage head is 27.5 +/- less than 2.2 A. A T7 precursor capsid (capsid I) expands when pelleted for x-ray scattering in the ultracentrifuge to essentially the same outer dimensions as for capsids II and IV. This expansion of capsid I can be prevented by fixing with glutaraldehyde; fixed capsid I has peak density at a radius of 247 A, 10% less than capsid II or IV.     

Bacteriophage phiNS11: a lipid-containing phage of acidophilic thermophilic bacteria. IV. Sedimentation coefficient, diffusion coefficient, partial specific volume, and particle weight of the phage.

The particle weight (molecular weight) of phiNS11 was determined from the sedimentation coefficient, diffusion coefficient, and partial specific volume of the phage. The sedimentation coefficient of the phage (S(0)20, W) is 416 +/- 2.7S. The diffusion coefficient D(0)20, W), which was determined by quasielastic light scattering measurement, is (0.57 +/- 0.03) x 10(-7) cm2/s. The partial specific volume was determined by the mechanical oscillation technique to be 0.747 +/- 0.007 cm3/g. Based on these values, the particle weight of the phage was calculated to be (70.3 +/- 4.3) x 10(6) daltons, which agrees well with the particle weight (69--72 x 10(6) daltons) estimated from the molecular weight of phage DNA and the content of DNA. The Stokes radius of the phage particle was calculated to be 37.7 +/- 2 nm and hydration of the phage was estimated to be 1.18 cm3/g of dry phage. From the particle weight and the chemical composition of the phage, we estimated that one phage particle contains one double-stranded DNA molecule, 16,000 residues of fatty acid, 72 protein I molecules, 920 protein II, 42 protein III, 48 protein IV, 290 protein V molecules, and 3,700 molecules of polyamines.     

Isolation and characterization of a new bacteriophage, KF1, immunologically cross-reactive with F-type pyocins

Pseudomonas aeruginosa strain NIH S produced a bacteriophage, KF1, immunologically cross-reactive with F-type pyocins. Phage KF1 was neutralized by both anti-pyocin F1 and anti-pyocin F3 sera, although the efficiency was very low. About eleven polypeptides were detected by SDS-polyacrylamide gel electrophoresis of the phage. Most of the subunit proteins were different from those of F-type pyocins, but the molecular weights of minor subunit proteins P3 and P6 seemed to be the same as those of band 1 and band 5 of F-type pyocins, respectively. The head of the phage appeared to have an icosahedral structure, approximately 63 nm in diameter, with a long (190 nm, 11 nm wide and about 45 striations) flexuous tail connected to a fiber structure (about 53 nm in length). The density in CsCl and the sedimentation coefficient of the phage were 1.54 g/ml and 392S, respectively. Some other biochemical properties were described. The nucleic acid of the phage was linear, double stranded DNA of molecular weight 4 x 10(7). The density of the DNA in CsCl was 1.719 g/ml, the melting temperature was 95.4 degrees C. The guanine plus cytosine content was calculated to be 60 to 64%.     

Partial characterization of coliphage WPK and a comparison with coliphage T3.

Coliphage WPK was originally isolated from sewage in Kiel, Germany, because its plaque diameter continued to expand for days. Electron microscopy revealed an isometric capsid with dimensions of 54 nm between opposite apices, and a short, noncontractile tail 16 nm long, placing phage WPK into morphogroup C1. The nucleic acid of phage WPK was linear double stranded DNA. The host ranges of phages WPK and T3 were identical. Of ten E. coli strains tested for host range, two were resistant and of eighteen other Enterobacteriaceae only four were susceptible. Seven gram-negative species which are not members of the Enterobacteriaceae were refractory. However, there were differences in plaque morphology and plaque expansion between the two phages. Phage T3 plaques expanded for at least seven days on E. coli B only, while phage WPK plaques expanded for at least seven days on four strains of E. coli. The buoyant density of WPK, determined by isopycnic density gradient centrifugation in CsCl, was 1,508 g/ml which was significantly different than that of T3 at 1.493 g/ml (P less than 0.05). Phage-encoded proteins were examined for each phage using [35S]methionine incorporation, SDS-PAGE, and autoradiography. Of thirty proteins identified in phage WPK and twenty-eight in phage T3, only fourteen were of the same size in both. We concluded that phage WPK was distinct, but related to T3.     

Characteristics of PR5, a lipid-containing plasmid-dependent phage.

An extensive characterization of plasmid-dependent phage PR5 isolated from sewage has been carried out. The phage has a head diameter of 65--68 nm, is isometric with a double-layered capsid, and a minority possess tails. It adsorbs to many but not all types of bacteria possessing P, N, or W plasmids. The phage contains 20% lipid, 15.1% DNA, and 64.9% protein by weight and has a buoyant density of 1.265 g/ml in CsCl. The DNA is double-stranded with a G + C content of 49% and a molecular weight of 7.4 +/- 0.6 x 10 (6) as shown by electron microscopy. Phospholipid content is 66% of lipid and consists of cardiolipin (13%), phosphatidylethanolamine (43%), and phosphatidylglycerol (44%) and differ quantitatively from that of host bacteria. Anti-PR5 serum inactivates other similar phages, PR3 and PR4. Phage adsorption is impaired in deep rough mutants of Salmonella minnesota.     

Characterization of two lipoproteins containing apolipoproteins B and E from lesion-free human aortic intima

Lesion-free areas of aortic intimas from seven men, 30 to 49 years old, were extracted with aqueous buffer within a few hours after an accidental or sudden death. Two lipoprotein fractions could be isolated by density gradient ultracentrifugation from all cases. The mean composition of fraction I (d less than 1.012 g/ml) resembled that reported for the cholesteryl ester-rich, beta-migrating very low density lipoprotein (beta-VLDL); the composition of fraction II (d 1.021-1.046 g/ml) resembled that of plasma low density lipoprotein (LDL). Mean diameter of the particles was 35 +/- 8 nm in fraction I and 25 +/- 5 nm in fraction II (22 +/- 2 nm in plasma LDL). Both fractions contained apolipoproteins B (apoB) and E (apoE), and had increased electrophoretic mobilities and reduced contents of linoleic acid. The immunoreactivity of apoB to a polyclonal and two monoclonal antibodies in both fractions was not different from that of plasma lipoproteins. The apoE isoform patterns in both fractions were similar to those obtained from the respective postmortem plasmas. When incubated with mouse peritoneal macrophages, fractions I and II enhanced the incorporation of radioactive oleate into cholesteryl esters by 10- to 20-fold and 3- to 4-fold, respectively, in comparison to plasma LDL. In conclusion, our results indicate that lesion-free human aortic intima contains two types of apoB- and apoE-containing lipoprotein particles, both of which might be potentially atherogenic.     

A novel cell line (Caco-2) for the study of intestinal lipoprotein synthesis

Lipoprotein synthesis by the colonic adenocarcinoma cell line Caco-2 was investigated to assess the utility of this cell line as a model for the in vitro study of human intestinal lipid metabolism. Electron micrographic analysis of conditioned medium revealed that under basal conditions of culture post-confluent Caco-2 cells synthesize and secrete lipoprotein particles. Lipoproteins of density (d) less than 1.063 g/ml consist of a heterogeneous population of particles (diameter from 10 to 90 nm). This fraction consists of very low density lipoproteins (d less than 1.006 g/ml) and low density lipoproteins (d = 1.019-1.063 g/ml). Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [35S]methionine-labeled Caco-2 lipoproteins revealed that very low density lipoproteins contain apolipoprotein E (apoE) and C apolipoproteins, while low density lipoproteins contained apoB-100, apoE, apoA-I, and C apolipoproteins. The 1.063-1.21 g/ml density fraction contained two morphological entities, discoidal (diameter 15.6 +/- 3.9 nm) and round high density lipoprotein particles (diameter 10.2 +/- 2.3 nm). The high density lipoproteins contained apoA-I, apoB-100, apoB-48, apoE, and the C apolipoproteins. Using isoelectric focusing polyacrylamide gel electrophoresis newly secreted apoA-I was identified as pro-apoA-I. ApoE and apoC-III released by Caco-2 cells were highly sialylated. mRNA species for apoA-I, apoC-III, and apoE, but not apoA-IV were identified by Northern blot analysis. ApoA-I, apoB, and apoE were visualized in Caco-2 cells by immunolocalization analysis. This intestinal cell line may be useful for in vitro studies of nutritional and hormonal regulation of lipoprotein synthesis.     

Human lymphedema fluid lipoproteins: particle size, cholesterol and apolipoprotein distributions, and electron microscopic structure

The concentration of cholesterol, apolipoproteins A-I, B, and E has been determined in lymphedema fluid from nine patients with chronic primary lymphedema. The concentrations were: 38.14 +/- 21.06 mg/dl for cholesterol, 15.6 +/- 6.17 mg/dl for apolipoprotein A-I, 7.5 +/- 2.8 mg/dl for apolipoprotein B, and 1.87 +/- 0.50 mg/dl for apolipoprotein E. These values represent 23%, 12%, 6%, and 38% of plasma concentrations, respectively. The ratio of esterified to unesterified cholesterol in lymphedema fluid was 1.46 +/- 0.45. Lipoproteins of lymphedema fluid were fractionated according to particle size by gradient gel electrophoresis and by exclusion chromatography. Gradient gel electrophoresis showed that a majority of high density lipoproteins (HDL) of lymphedema fluid were larger than ferritin (mol wt 440,000) and smaller than low density lipoproteins (LDL); several discrete subpopulations could be seen with the large HDL region. Fractionation by exclusion chromatography showed that more than 25% of apolipoprotein A-I and all of apolipoprotein E in lymphedema fluid was associated with particles larger than plasma HDL2. Apolipoprotein A-I also eluted in fractions that contained particles the size of or smaller than albumin. Isolation of lipoproteins by sequential ultracentrifugation showed that less than 25% of lymphedema fluid cholesterol was associated with apolipoprotein B. The majority of apolipoprotein A-containing lipoproteins of lymphedema fluid were less dense than those in plasma. Ultracentrifugally separated fractions of lipoproteins were examined by electron microscopy. The fraction d less than 1.019 g/ml contained little material, while fraction d 1.019-1.063 g/ml contained two types of particles: round particles 17-26 nm in diameter and square-packing particles 13-17 nm on a side. Fractions d 1.063-1.085 g/ml had extensive arrays of square-packing particles 13-14 nm in size. Fractions d 1.085-1.11 g/ml and fractions d 1.11-1.21 g/ml contained round HDL, 12-13 nm diameter and 10 nm diameter, respectively. Discoidal particles were observed infrequently.     

Bacteriophages of Rhodopseudomonas spheroides: Isolation and Characterization of a Rhodopseudomonas spheroides Bacteriophage

A DNA-containing bacteriophage, designated RS1, infecting Rhodopseudomonas spheroides 2.4.1, has been isolated from sewage. The buoyant density of RS1 in CsCl equilibrium centrifugation is 1.50 g/cm(3), and the buoyant density of RS1 DNA is 1.706. The phage possesses a polyhedral head, approximately 65 nm in diameter, and a tail 60 nm long. When grown on aerobic cells, RS1 has a latent period of 120 min and an average burst size of 20. When grown on anaerobic cells, RS1 has a latent period of 150 min, and a burst size similar to that observed during aerobic infection. The adsorption rate constant of RS1 to aerobic cells is 1.2 x 10(-9) ml/min, and 0.58 x 10(-9) ml/min to anaerobic cells. Adsorption of RS1 to R. spheroides requires the presence of divalent cations.     

Density distribution and physicochemical properties of plasma lipoproteins and apolipoproteins in the goose, Anser anser, a potential model of liver steatosis

The fractionation and physicochemical characterization of the complex molecular components composing the plasma lipoprotein spectrum in the goose, a potential model of liver steatosis, are described. Twenty lipoprotein subfractions (d less than 1.222 g/ml) were separated by isopycnic density gradient ultracentrifugation, and characterized according to their chemical composition, particle size and particle heterogeneity, electrophoretic mobility, and apolipoprotein content. Analytical ultracentrifugal analyses showed high density lipoproteins (HDL) to predominate (approximately 450 mg/dl plasma), the peak of its distribution occurring at d approximately 1.090 g/ml (F1.21 approximately 2.5). The HDL class displayed marked density heterogeneity, HDL1-like particles being detected up to a lower density limit of approximately 1.020 g/ml, particle size decreasing progressively from 17-19 nm at d 1.024-1.028 g/ml to 10.5-12 nm (d 1.055-1.065 g/ml), and then remaining constant (approximately 9 nm) at densities greater than 1.065 g/ml. HDL subfractions displayed multiple size species; five subspecies were present over the range d 1.103-1.183 g/ml with diameters of 10.5, 9.9, 9.0, 8.2, and 7.5 nm, four in the range d 1.090-1.103 g/ml (diameters 10.5, 9.9, 9.0, and 8.2 nm) and three over the range d 1.076-1.090 g/ml (diameters 10.5, 9.9, and 9.0 nm). ApoA-I (Mr 25,000-27,000) was the major apolipoprotein in all goose HDL subfractions, while the minor components (apparent Mr 100,000, 91,000, 64,000, 58,000, approximately 42,000, 18,000 and apoC-like proteins) showed marked quantitative and qualitative variation across this density range (i.e., 1.055-1.165 g/ml). The d 1.063 g/ml boundary for separation of goose low density lipoproteins (LDL) from HDL was inappropriate, since HDL-like particles were present in the density interval 1.024-1.063 g/ml, while particles enriched in apoB (Mr approximately 540,000) and resembling LDL in size (approximately 20.5 nm) were detected up to a density of approximately 1.076 g/ml. Goose LDL itself was a major component of the profile (90-172 mg/dl) with a single peak of high flotation rate (Sf approximately 10.5). The physicochemical properties and apolipoprotein content of intermediate density lipoproteins (IDL) and LDL varied but little over the range d 1.013-1.040 g/ml, presenting as two particle species (diameters 20.5 and 21 nm) of essentially constant chemical composition; LDL (d 1.019-1.040 g/ml) were separated from HDL1 by gel filtration chromatography and appeared to contain primarily apoB with lesser amounts of apoA-I.(ABSTRACT TRUNCATED AT 400 WORDS)     

Properties of the Deoxyribonucleic Acid Contained in the Defective Particle Coliphage 15

Escherichia coli strain 15 TAU, which requires thymine, arginine, and uracil for growth and harbors an apparently defective prophage, was induced by exposure to ultraviolet light (580 ergs/mm(2)) or to mitomycin C (5 mug/ml). Phage particles (coliphage 15) were recovered from the resulting lysate by treatment with deoxyribonuclease, filtration, and several cycles of differential centrifugation. Analysis of the phage particles obtained by using cesium chloride density gradient centrifugation in a preparative ultracentrifuge resulted in the resolution of three components. The major component had a peak density of 1.52 to 1.53 g/cm(3) followed by components with densities of 1.5 and 1.49 g/cm(3). The guanine plus cytosine content of coliphage 15 deoxyribonucleic acid (DNA) was determined by both analytical ultracentrifugation in cesium chloride and by thermal denaturation in standard saline citrate buffer. Respective values of 46.4 +/- 1% and 46.6 +/- 1% guanine plus cytosine content were obtained. Coliphage 15 DNA formed molecular hybrids with messenger ribonucleic acid (RNA) from both uninduced and ultraviolet-induced cultures of E. coli 15 TAU, but did not hybridize with E. coli ribosomal RNA. The molecular weight of coliphage 15 DNA was determined by constant velocity sucrose density gradient centrifugation to be about 33 x 10(6) daltons.     

Characterization of the bacteriophage B2 of Lactobacillus plantarum ATCC 8014

Bacteriophage B2 of Lactobacillus plantarum ATCC 8014, isolated in 1971, belonged to Bradley's group B. Electron microscopy revealed an isometric head (110 nm) and a long non-contractile and flexible tail (500 nm) containing about 75 regularly aligned lateral striations. Burst size was 12-14 phages per infectious centre. The latent period for phage development was 75 min and the rise period approximately 90 min. The phage particle contained 5 major proteins. The buoyant density of the phage in CsCl was measured as 1.575 g/cm3. B2 genome was a linear double-stranded DNA molecule of 37 +/- 1% guanosine-cytosine. Its size was 73 kilobase pairs (kbp). Restriction analysis of the genome showed that 4 restriction enzymes (Xba I, Sac I, Bgl II and Sma I) gave single site cuts in the DNA, while Ava I and Sal I formed 2 and 5 cuts, respectively.     

Characterization of Inducible Bacteriophages in Bacillus licheniformis

Two morphologically distinct and physically separable defective phages have been found in Bacillus licheniformis NRS 243 after induction by mitomycin C. One of them (PBLB) is similar to the defective phage PBSX of B. subtilis, which has a density of 1.373 g/cm(3) in CsCl and a sedimentation coefficient of 160S. PBLB incorporates into its head mainly bacterial deoxyribonucleic acid (DNA) which has a sedimentation coefficient of 22S and a buoyant density in CsCl of 1.706 g/cm(3). The other phage (PBLA) has a morphology similar to the temperate phage phi105 of B. subtilis; the head diameter is about 66 nm, and it possesses a long and noncontractile tail. PBLA has a density of 1.484 g/cm(3) in CsCl and the phage-specific DNA, which is exclusively synthesized after induction by mitomycin C, has a density of 1.701 g/cm(3). PBLA DNA is double-stranded and has a sedimentation coefficient of 36S, corresponding to a molecular weight of 34 x 10(6) to 35 x 10(6) daltons. The phage DNA has one interruption per single strand, giving single-stranded segments with molecular weights of 13 x 10(6) and 4 x 10(6) daltons. Common sequences between the two phage DNA species and with their host DNA have been demonstrated by DNA-DNA hybridization studies. Both phage particles kill sensitive bacteria. However, all attempts thus far to find an indicator strain to support plaque formation have been unsuccessful.     

Postnatal Development and Isolation of Peroxisomes from Brain

We analyzed the postnatal peroxisome development in rat brain by measuring the enzyme activities of catalase and acyl-CoA oxidase and beta-oxidation of [1-14C]lignoceric acid. These enzyme activities were higher between 10 and 16 days of postnatal life and then decreased. We developed and compared two different methods for isolation of enriched peroxisomes from 10-day-old rat brain by using a combination of differential and density gradient centrifugation techniques. Peroxisomes in Percoll (self-generating gradient) banded at a density of 1.036 +/- 0.012 g/ml and in Nycodenz continuous gradient at 1.125 +/- 0.014 g/ml. Acyl-CoA oxidase, D-amino acid oxidase, L-pipecolic acid oxidase, and dihydroxyacetone phosphate acyltransferase activities and activities for the oxidation of very long chain fatty acid (lignoceric acid) were almost exclusively associated with catalase activity (a marker enzyme for peroxisomes) in the gradient. The postnatal increase in peroxisomal activity with the onset of myelination and the presence of enzyme for the biosynthesis of plasmalogens and oxidation of very long chain fatty acid (both predominant constituents of myelin) suggest that brain peroxisomes may play an important role in the assembly and turnover of myelin.     

Distribution of cholesterol and apolipoprotein A-I and A-II in human high density lipoprotein subfractions separated by CsCl equilibrium gradient centrifugation: evidence for HDL subpopulations with differing A-I/A-II molar ratios.

The purpose of this experiment was to characterize the high density lipoproteins (HDL) as a function of hydrated density. HDL was subfractionated on the basis of hydrated density by CsCl density gradient centrifugation of whole serum or the d 1.063-1.25 g/ml HDL fraction isolated from three men and three women. Apolipoprotein A-I and A-II quantitation by radial immunodiffusion showed that the A-I/A-II ratio varied with the lipoprotein hydrated density. The A-I/A-II molar ratio of HDL lipoproteins banding between d 1.106 and 1.150 g/ml was nearly constant at 2.2 +/- 0.2. In the density range 1.151-1.25 g/ml the A-I/A-II ratio increased as the density increased. On the other hand, in the density range between 1.077 and 1.105 the A-I/A-II ratio increased as the density decreased, ranging from 2.8 +/- 0.5 for the d 1.093-1.105 g/ml fraction to 5.6 +/- 1.3 for the d 1.077-1.082 g/ml fraction. The d 1.063-1.076 g/ml fraction and the d 1.077-1.082 g/ml fractions had comparable A-I/A-II ratios. Serum and the d 1.063-1.25 g/ml HDL fraction exhibited similar trends. The cholesterol/(A-I + A-II) ratio decreased as the density increased in all 12 samples (six serum and six HDL) examined. Gradient gel electrophoresis of the density gradient fractions showed that as the density increased from 1.063 to 1.200 g/ml the apparent molecular weight decreased from 3.9 x 10(5) to 1.1 x 10(5). HDL subfractions with the same hydrated densities had comparable molecular weights and A-I/A-II and cholesterol/(A-I + A-II) ratios when isolated from men or women. HDL contains subpopulations that differ in the A-I/A-II molar ratio.-Cheung, M. C., and J. J. Albers. Distribution of cholesterol and apolipoprotein A-I and A-II in human high density lipoprotein subfractions separated by CsCl equilibrium gradient centrifugation: evidence for HDL subpopulations with differing A-I/A-II molar ratios.     

Incomplete and Aberrant Particles of Actinophage MSP2 from Lysates of Streptomyces venezuelae

Lysates of actinophage MSP2, propagated on Streptomyces venezuelae S13, contain at least 10(11) PFU/ml. During purification by centrifugation methods and by adsorption chromatography, a number of types of aberrant and incomplete phage particles were seen by electron microscopy. Infectious MSP2 had a buoyant density in CsCl of 1.52 g/cm(3) and an absorbance at 260 nm relative to that at 280 nm (A(260)/A(280)) of 1.53. Empty capsids banded at 1.276 g/cm(3) and partially filled capsids banded at 1.351 g/cm(3), and A(260)/A(280) ratios were 0.77 and 1.24, respectively. Two kinds of light capsids found in CsCl fractions of 1.278 g/cm(3) probably include the 1.276 component. Some capsids were joined by tail-like structures. Ghosts and polyheads also were present. Aberrant particles observed by electron microscopy included two-tailed actinophage, phage with abnormal tail positions, and large-headed phage.     

Rapid isolation of vesicular and micellar carriers of biliary lipids by ultracentrifugation

A simple, rapid, and new method has been developed to isolate and to quantitate the vesicular carrier of biliary lipids by isopycnic ultracentrifugation. The method combines the use of Metrizamide, as an inert centrifugation media to change the density of bile for isopycnic separation of vesicles, and a vertical rotor, to decrease both the time of centrifugation and the pressure of the hydrostatic column in the ultracentrifuge tube. Vesicles harvested from bile-Metrizamide density gradients were identified by negative staining electron microscopy. The buoyant densitites of biliary vesicles varied between 1.010 and 1.030 g/ml. The diameter of vesicles in fractions with d less than 1.020 g/ml was 82 +/- 10 nm and in fraction with d approximately 1.030 g/ml was 57 +/- 8 nm. Gel filtration chromatography with Ultrogel AcA 34 was used to validate the quantitive isolation of vesicles by the ultracentrifugal method. In experiments with bile-Metrizamide continuous preformed density gradients, greater than 93% of vesicular cholesterol was found in fractions with d less than 1.030 g/ml after 285 min of centrifugation at 50,000 rpm in a VTi vertical rotor (Beckman Instruments, Inc.). When 16% Metrizamide was dissolved in bile and centrifuged for 120 min, greater than 96% of total vesicular cholesterol was found in the top 0.4 ml of the 5-ml centrifuge tube, as assessed by gel filtration chromatography. This fraction contained less than 8% of cholesterol carried in micelles, as assessed by gel filtration chromatography. The variation coefficient of this short ultracentrifugal method to isolate biliary vesicles was 4.6%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Structure of the dimyristoylphosphatidylcholine vesicle and the complex formed by its interaction with apolipoprotein C-III: X-ray small-angle scattering studies.

Single bilayer vesicles of dimyristoylphosphatidylcholine have been investigated by small-angle X-ray scattering at 28 degrees C. The results indicate that these vesicles are hollow spherical shell structures with an outer radius of approximately 12 nm and a molecular weight of (3.2 +/- 0.5) X 10(6). The shell was found to be 4.4 +/- 0.2 nm thick with a cross-sectional electron-density profile characteristic for a single phospholipid bilayer. Upon interaction of these vesicles with apolipoprotein C-III from human very low density lipoproteins at a protein/lipid ratio greater than 0.08 (g/g), a complex containing 0.25 g of protein/g of lipid, with molecular weight of (3.9 +/- 0.4) X 10(5), is formed. The shape analysis indicates a highly asymmetric particle with an internal partition of low and high electron density resembling that produced by a bilayer structure. Model calculations and curve-fitting procedures show good agreement between the experimental scattering curve and that computed for an oblate ellipsoidal structure with dimensions of 17 X 17 X 5 nm and a 1 nm thick shell of high electron density surrounding the core of low electron density.     

Physicochemical properties of pyocin F1.

The physiochemical properties of pyocin F1 were studied. Pyocin F1 consists of flexuous rod-like particles homogenous in size. Each particle was composed of rod and fiber parts. The rod part was 105.5 +/- 9.5 nm long and 10.0 +/- 1.4 nm wide, and showed regular striations amounting to 23 layers. The fiber part was composed of several filaments; the length of the longest filament was 43.0 +/- 12.0 nm. The amino acid composition, the partial specific volume (0.720 ml/g), the sedimentation coefficient (S020,W = 35.1S), and the translational diffusion constant (0.94 +/- 0.01 x 10(-7) cm2/s) were determined. The particle weight was calculated to be 3.23 x 10(6) daltons.