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PubMed2003

Latex particle size distribution by dynamic light scattering: novel data processing for multiangle measurements.

Multiangle dynamic light scattering (DLS) provides a better estimate of particle size distributions (PSD) than single-angle DLS. However, multiangle data treatment requires appropriate weighting of each autocorrelation measurement prior to calculation of the PSD. The weighting coefficients may be directly obtained from (i). the autocorrelation baselines or (ii). independent measurement of the average light intensity by elastic light scattering. However, the propagation of errors associated with such procedures may intolerably corrupt the PSD estimate. In this work, an alternative recursive least-squares calculation is proposed that estimates the weighting coefficients on the basis of the complete autocorrelation measurement. The method was validated through a numerical example that simulates the analysis of a polystyrene latex with a bimodal PSD and with "measurements" taken at 10 detection angles. The ill-conditioned nature of the problem determines that the "true" PSD cannot be recovered, even in the absence of errors. A sensitivity analysis was carried out to determine the effect of errors in the weighting coefficients on the PSD recoveries.

Journal Article↗

PubMed2002

Measurement of particle size distribution in multilayered skin phantoms using polarized light spectroscopy.

We report on the ability to use polarized light to measure the particle size distribution of thin layers of polystyrene microspheres on top of a solid Intralipid phantom. The optical properties of each layer were adjusted to match the absorption and scattering properties of the epidermis (polystyrene layer) and dermis (Intralipid layer). Polarized light was used to discriminate between light scattered from the top layer of polystyrene and the lower layer of Intralipid. In this paper we also study the effect of the thickness of the top layer on the ability to reconstruct the polystyrene size distribution.

Biophysical Phenomena↗

PubMed2005

The effect of the particle size on the kinetics of CO electrooxidation on high surface area Pt catalysts.

Using high-resolution transmission electron microscopy (TEM), infrared reflection-absorption spectroscopy (IRAS), and electrochemical (EC) measurements, platinum nanoparticles ranging in size from 1 to 30 nm are characterized and their catalytic activity for CO electrooxidation is evaluated. TEM analysis reveals that Pt crystallites are not perfect cubooctahedrons, and that large particles have "rougher" surfaces than small particles, which have some fairly smooth (111) facets. The importance of "defect" sites for the catalytic properties of nanoparticles is probed in IRAS experiments by monitoring how the vibrational frequencies of atop CO (nu(CO)) as well as the concomitant development of dissolved CO(2) are affected by the number of defects on the Pt nanoparticles. It is found that defects play a significant role in CO "clustering"on nanoparticles, causing CO to decrease/increase in local coverage, which yields to anomalous redshift/blueshift nu(CO) frequency deviations from the normal Stark-tuning behavior. The observed deviations are accompanied by CO(2) production, which increases by increasing the number of defects on the nanoparticles, that is, 1 < or = 2 < 5 << 30 nm. We suggest that the catalytic activity for CO adlayer oxidation is predominantly influenced by the ability of the surface to dissociate water and to form OH(ad) on defect sites rather than by CO energetics. These results are complemented by chronoamperometric and rotating disk electrode (RDE) data. In contrast to CO stripping experiments, we found that in the backsweep of CO bulk oxidation, the activity increases with decreasing particle size, that is, with increasing oxophilicity of the particles.

Journal Article↗

PubMed2003

Heterozygosity for ABCA1 gene mutations: effects on enzymes, apolipoproteins and lipoprotein particle size.

A cohort of 13 female and 14 male heterozygotes for ATP binding cassette A1 (ABCA1) gene defects was directly compared with 13 and 14 unaffected female and male family members of almost exact same age. The activities of three proteins that play key roles in HDL metabolism were measured in addition to extensive lipid and (apo) lipoprotein subfraction analysis. Compared to controls, LCAT activity was reduced by 15% in affected subjects (P < 0.001) while PLTP activity was unaffected. Interestingly, CETP activity was elevated by 50% in the heterozygote siblings of one kindred but was unaffected in heterozygotes of the three other families. With respect to lipids, the heterozygotes had normal total cholesterol (TC), and LDL-cholesterol concentrations but presented with a trend towards increased triglyceride levels (13%; P = 0.08). HDL metabolism, by contrast, was severely affected as illustrated by 40% reductions in HDL-cholesterol (P < 0.001) with concomitant reductions in apoAI (25%; P < 0.001) levels and in lipoprotein subfraction LpAI (28%; P < 0.001), LpAI:AII (24%; P=0.014), and LpCIII:nonB (34%; P < 0.001) concentrations. We furthermore observed reduced average HDL particle size (5%; P = 0.004; 16% in female and 3.6% in male) and reduced plasma apoCIII concentration (15%; P = 0.006) while apoAII, apoAIV, apoE and apoB levels were unchanged. In conclusion, heterozygosity for ABCA1 defects was associated with reduced LCAT activity in absence of effects on PLTP activity. Of special interest was our finding that the effects of compromised ABCA1 function on HDL were more pronounced in women than in men.

ATP Binding Cassette Transporter 1↗

PubMed2003

Forms and distribution of selenium at different depths and among particle size fractions of three Taiwan soils.

The bioavailability of selenium in soils for plants depends more on its forms than on its total concentration. The purpose of the present study was to examine the solid-phase forms of selenium at different depths of three soil series representing major farming soil groups in Taiwan as well as the amounts of selenium in sand, silt and clay fractions of the soils. The study was conducted by means of sequential extraction to obtain the amounts of selenium and the distribution of various solid-phase forms of selenium at different depths of Pinchen (121 degrees 11(')E, 24 degrees 55(')N), Toulun-Sheto (120 degrees 55(')E, 24 degrees 50(')N), and Chunliao (120 degrees 25(')E, 23 degrees 57(')N) soil series. The amounts of metal oxide-bound form of selenium in the three soil series were the largest, with those of Pinchen and Toulun-Sheto soil series exceeding 50% of the total amounts of selenium and that of Chunliao soil series maintained at 30-40%. In the Pinchen and Toulun-Sheto soil series, the amounts of selenium in clay fractions were the largest, with a significant difference between the clays with and without metal oxides and organic matter removed. The amounts of selenium remained high in silt and/or sand fractions of the Chunliao soil series with metal oxides and organic matter removed. Metal oxide and organic matter contents of the three soil series mainly affect the amounts of various solid-phase forms of selenium and their distribution in different depths and particle size fractions of the soils. This observation of selenium associated with soil constituents was in good agreement with the results of the adsorption of selenite and selenate by the three soil series.

Adsorption↗

PubMed2000

Purified eicosapentaenoic and docosahexaenoic acids have differential effects on serum lipids and lipoproteins, LDL particle size, glucose, and insulin in mildly hyperlipidemic men.

BACKGROUND: Regular consumption of n-3 fatty acids of marine origin can improve serum lipids and reduce cardiovascular risk. OBJECTIVE: This study aimed to determine whether eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids have differential effects on serum lipids and lipoproteins, glucose, and insulin in humans. DESIGN: In a double-blind, placebo-controlled trial of parallel design, 59 overweight, nonsmoking, mildly hyperlipidemic men were randomly assigned to receive 4 g purified EPA, DHA, or olive oil (placebo) daily while continuing their usual diets for 6 wk. RESULTS: Fifty-six men aged 48.8 +/- 1.1 y completed the study. Relative to those in the olive oil group, triacylglycerols fell by 0.45 +/- 0.15 mmol/L ( approximately 20%; P = 0.003) in the DHA group and by 0.37 +/- 0.14 mmol/L ( approximately 18%; P = 0.012) in the EPA group. Neither EPA nor DHA had any effect on total cholesterol. LDL, HDL, and HDL(2) cholesterol were not affected significantly by EPA, but HDL(3) cholesterol decreased significantly (6.7%; P = 0.032). Although HDL cholesterol was not significantly increased by DHA (3. 1%), HDL(2) cholesterol increased by approximately 29% (P = 0.004). DHA increased LDL cholesterol by 8% (P = 0.019). Adjusted LDL particle size increased by 0.25 +/- 0.08 nm (P = 0.002) with DHA but not with EPA. EPA supplementation increased plasma and platelet phospholipid EPA but reduced DHA. DHA supplementation increased DHA and EPA in plasma and platelet phospholipids. Both EPA and DHA increased fasting insulin significantly. EPA, but not DHA, tended to increase fasting glucose, but not significantly so. CONCLUSIONS: EPA and DHA had differential effects on lipids, fatty acids, and glucose metabolism in overweight men with mild hyperlipidemia.

Adult↗

PubMed2006

Lipoprotein subclass and particle size differences in Afro-Caribbeans, African Americans, and white Americans: associations with hepatic lipase gene variation.

Despite a higher prevalence of coronary heart disease risk factors, men of African origin have less coronary atherosclerosis, as measured by coronary calcification, than whites. In part, this is thought to be because of the less atherogenic lipoprotein profile observed in men of African origin, characterized by lower triglycerides and higher high-density lipoprotein (HDL) cholesterol. We hypothesized that the -514C>T polymorphism in the hepatic lipase gene (LIPC) plays a significant role in determining a less atherogenic lipoprotein profile observed in men of African origin. Previously conducted studies of the LIPC -514C>T polymorphism in African Americans may have been confounded by a higher level of European admixture; in addition, the results from these studies do not necessarily apply to other African populations because gene-environment interactions may differ. Thus, we compared nuclear magnetic resonance spectroscopy-measured lipoprotein subclass patterns and LIPC -514C>T genotypes in population-based samples of older white American (n = 532) and African American (n = 97) men from the Cardiovascular Health Study to those among older, less admixed, Afro-Caribbean men (n = 205) from the Tobago Health Study. Men of African origin had a more favorable lipoprotein profile than whites. In addition, levels of low-density lipoprotein cholesterol, total cholesterol, and triglyceride, and large and small very low-density lipoprotein, small low-density lipoprotein, as well as very low-density lipoprotein particle size, were remarkably lower in Afro-Caribbean men than in either African American or white men. The frequency of the LIPC -514T allele was much higher in Afro-Caribbeans (0.57) and in African Americans (0.49) than in whites (0.20). The -514T allele in both populations of African origin, but not in whites, was associated with elevated large HDL and greater HDL size. Our findings indicate that the higher frequency of the LIPC -514T allele found in men of African origin living in different environments significantly contributes to the more favorable distribution of HDL subclasses compared with whites.

Adult↗

PubMed2006

Probing particle size distributions in natural surface waters from 15 nm to 2 microm by a combination of LIBD and single-particle counting.

We present a technique for measuring colloid size distributions between 15 nm and 2 microm at concentrations relevant to natural surface waters. Two particle-measuring methods are combined: laser-induced breakdown detection (LIBD), which allows the quantification of colloid size distributions below 400 nm, and a commercial single-particle counter that extends the accessible size range up to two mum. Centrifugation was used in order to separate micrometer sized particles for the LIBD measurement. The feasibility is demonstrated on water of Lake Brienz (Switzerland) and the River Pfinz (Germany) and the particle size distributions follow Pareto's law even down to 15 nm in both cases.

Journal Article↗

PubMed2004

Low-density lipoprotein particle size loci in familial combined hyperlipidemia: evidence for multiple loci from a genome scan.

OBJECTIVE: Low-density lipoprotein (LDL) size is associated with vascular disease and with familial combined hyperlipidemia (FCHL). METHODS AND RESULTS: We used logarithm of odds (lod) score and Bayesian Markov chain Monte Carlo (MCMC) linkage analysis methods to perform a 10-cM genome scan of LDL size, measured as peak particle diameter (PPD) and adjusted for age, sex, body mass index, and triglycerides in 4 large families with FCHL (n=185). We identified significant evidence of linkage to a chromosome 9p locus (multipoint lod(max)=3.70; MCMC intensity ratio [IR]=21) in a single family, and across all 4 families to chromosomes 16q23 (lod(max)=3.00; IR=43) near cholesteryl ester transfer protein (CETP) and to 11q22 (lod(max)=3.71; IR=120). Chromosome 14q24-31, a region with previous suggestive LDL PPD linkage evidence, yielded an IR of 71 but an lod(max)=1.79 in the combined families. CONCLUSIONS: These results of significant evidence of linkage to 3 regions (9p, 16q, and 11q) and confirmatory support of previous reported linkage to 14q in large FCHL pedigrees demonstrate that LDL size is a trait influenced by multiple loci and illustrate the complementary use of lod score and MCMC methods in analysis of a complex trait.

Adult↗

PubMed2002

Effects of pravastatin treatment on lipoprotein subclass profiles and particle size in the PLAC-I trial.

Lipoprotein subclass analyses may facilitate coronary heart disease (CHD) risk stratification and provide insight into the cardioprotective benefits of statins (3-hydroxymethylglutaryl-coenzyme A reductase inhibitors). This study evaluated the influence of pravastatin on lipoprotein subclass profiles to determine whether subjects with predominantly large LDL (LDL size >20.5 nm) or small LDL (LDL size < or =20.5 nm) at baseline differ in responsiveness to drug treatment. Frozen plasma specimens were analyzed from a subset of participants in the Pravastatin Limitation of Atherosclerosis in the Coronaries (PLAC-I) trial at baseline and after treatment for 6 months with pravastatin (n=154) or placebo (n=138). Lipids were measured by standard chemical methods and lipoprotein subclasses by nuclear magnetic resonance (NMR) spectroscopy. Pravastatin-induced changes in lipid levels were similar in subjects with large or small LDL at baseline. Levels of the most abundant LDL subclass were preferentially lowered by pravastatin, resulting in an increase in average LDL size for those with a predominance of small LDL. High-risk CHD subjects with small LDL particles gain at least as much pharmacological benefit from pravastatin as those with large LDL, as evidenced by reductions in the numbers of total and small LDL particles, and increases in average LDL and HDL particle size.

Aged↗

PubMed2000

Experimental measurement of particle size distribution and voidage in an expanded bed adsorption system.

This paper presents an experimental analysis of matrix bead size distribution and voidage variations with axial height in an expanded bed adsorption system. Use of a specially constructed expanded bed with side ports has enabled sampling from within the expanded bed along the vertical axis. Particles removed from within the bed were measured for their size distributions. Residence time distribution studies were used to estimate bed voidage. Measurements of axial and radial particle size distributions and axial voidage distribution have been made at different flow rates. Particle size was found to be radially constant, indicating constant stratification in the column. The particle size was found to decrease with increasing axial height. Voidage increased with axial height from a settled bed value of 0.39 to approaching unity for high liquid velocities and increased at a constant axial position with increased flowrate. This information provides key insight into bed stability and data for the improved modeling of this important unit operation.

Adsorption↗

PubMed2004

Relation between cell disruption conditions, cell debris particle size, and inclusion body release.

The efficiency of physical separation of inclusion bodies from cell debris is related to cell debris size and inclusion body release and both factors should be taken into account when designing a process. In this work, cell disruption by enzymatic treatment with lysozyme and cellulase, by homogenization, and by homogenization with ammonia pretreatment is discussed. These disruption methods are compared on the basis of inclusion body release, operating costs, and cell debris particle size. The latter was measured with cumulative sedimentation analysis in combination with membrane-associated protein quantification by SDS-PAGE and a spectrophotometric peptidoglycan quantification method. Comparison of the results obtained with these two cell debris quantification methods shows that enzymatic treatment yields cell debris particles with varying chemical composition, while this is not the case with the other disruption methods that were investigated. Furthermore, the experiments show that ammonia pretreatment with homogenization increases inclusion body release compared to homogenization without pretreatment and that this pretreatment may be used to control the cell debris size to some extent. The enzymatic disruption process gives a higher product release than homogenization with or without ammonia pretreatment at lower operating costs, but it also yields a much smaller cell debris size than the other disruption process. This is unfavorable for centrifugal inclusion body purification in this case, where cell debris is the component going to the sediment and the inclusion body is the floating component. Nevertheless, calculations show that centrifugal separation of inclusion bodies from the enzymatically treated cells gives a high inclusion body yield and purity.

Biotechnology↗

PubMed2005

Extension of the graphical technique for estimation of particle size distribution parameters for the consistent intercomparison of diverse sets of multiwavelength lidar derived optical coefficients.

In applying the graphical technique to the estimation of the particle size distribution (PSD) parameters, determination of proper bounds surrounding the solution space for a particular confidence level is essential to the consistent intercomparison of diverse multiwavelength lidar optical data sets. The graphical technique utilizes ratios of backscatter and/or extinction coefficients, and it is shown that if the correlation between ratios is not taken into account in calculating the error bounds, the solution space will be overestimated, resulting in relatively larger discrepancies for a larger number of optical coefficients. A method for correcting the bounds, to account for the correlation is developed for various numbers of wavelengths. These improved bounds are then applied, for the case of a monomodal lognormal PSD, with an assumed refractive index, to assess the role additional Raman extinction channels play in improving retrieval capability of a typical three-channel backscatter lidar (1064, 532, and 355 nm) under varying noise levels. Applying the same formalism to underlying bimodal distributions of coarse and fine particles can result in false monomodal solutions. However, when both Raman optical extinction channels are available, no solution is obtained. This can potentially serve as a quick and simple method, prior to a more complex regularization analysis, to differentiate between cases in which the fine mode is dominant versus the cases in which the contribution from the coarse mode is significant.

Journal Article↗

PubMed1999

Effects of particle size and adding sequence of fine lactose on the deposition of salbutamol sulphate from a dry powder formulation.

Ternary mixtures composed of coarse lactose (CL) (90.8 microm), salbutamol sulphate (SS) (5.8 microm) and either micronised lactose (ML) (5 microm) or intermediate sized lactose (IML) (15.9 microm) in a ratio of 66.5:1:1 w/w were prepared using different mixing sequences of the various components. In addition, a binary mixture composed of CL and SS (67.5:1 w/w) was also prepared as the control. The in vitro deposition of SS was measured using a twin stage impinger after aerosolisation at 60 and 90 l min-1 via a Rotahaler. The aerodynamic particle size distribution of both the aerosolised SS and lactose was further analysed using an Andersen cascade impactor at 60 l min-1. All ternary mixtures produced a significantly higher (analysis of variance, P<0.01) fine particle fraction (FPF) and fine particle dose (FPD) of SS than the control after aerosolisation at either 60 or 90 l min-1. Formulations containing the ML produced significantly (P<0.05) higher FPF and FPD of SS than those containing the IML at both aerosolisation flow rates. Different mixing sequences were also shown to result in different deposition profiles of both SS and lactose after aerosolisation of the ternary mixtures containing ML at 60 l min-1. The formulation prepared by first blending ML with CL before mixing with SS produced a higher FPF and FPD of SS but a lower FPF of lactose than the same formulation in terms of composition but prepared using different mixing orders of the three components. In contrast, the formulations containing IML produced a similar deposition profile to SS, regardless of the mixing sequences, and so did the formulations containing ML aerosolised at 90 l min-1. These results suggest that the effect of mixing sequences on drug deposition may become more prominent at lower aerosolisation flow rates and by reducing the size of any added fine lactose.

Albuterol↗

PubMed2002

Size analysis of a pressurized metered dose inhaler-delivered solution formulation by an Aerosizer-LD time-of-flight aerosol particle size spectrometer.

In a previous study, an Aerosizer-LD time-of-flight (TOF) aerosol spectrometer was shown to underestimate significantly the aerodynamic size of airborne particles produced following actuation of a suspension-based formulation delivered from a pressurized metered-dose inhaler (pMDI) via a nonelectrostatic valved holding chamber (VHC). It was postulated that the nonspecific nature of the particle detection system in terms of chemical composition was responsible for the inclusion of smaller non-drug-containing excipient particles in the measured size distribution data from this analyzer. This limitation may not apply to certain solution formulations in which the only particles remaining after the evaporation of propellant and volatile excipient (solubilizer) are composed of pure drug substance. Such a formulation (QVAR, HFA-formulated beclomethasone di-propionate [BDP]) has recently become available, and the present investigation was therefore designed to test this hypothesis. Aerosizer-LD measured mass-weighted size distribution data for QVAR had a mass median aerodynamic diameter (MMAD) close to 1.1 microm, very similar to published data for this parameter, based on measurement of the aerosol by cascade impactor followed by drug-specific assay. However, the Aerosizer-LD underestimated the spread of the size distribution significantly. The causes are believed to be a combination of two separate effects: (1) lack of sensitivity of the particle detection system to particles finer than about 0.7 microm aerodynamic diameter and (2) preferential removal of particles larger than the MMAD, either by evaporation of residual solvent (ethanol) or by inertial/gravitational deposition in the sampling arrangement upstream of the measurement zone.

Aerosols↗

PubMed2003

Exposure to dust and its particle size distribution in shoe manufacture and repair workplaces measured with GRIMM laser dust monitor.

OBJECTIVES: Owing to a diversified technological process and a great variety of products and materials used in shoe manufacture, workers may be exposed to dusts that contain different chemicals and particles of various shapes and sizes. The aim of this study was to assess the dust exposure, taking account of concentration of particular size fractions according to the European Standard Norm, and to analyze particle size distribution in inhalable dust at selected workplaces in a modern shoe manufacture plant and in a small shoe repair workshop in comparison with other industrial branches. MATERIALS AND METHODS: In these two workplaces, the concentrations of dust, representing the inhalable, thoracic, and respirable fractions, were measured with the GRIMM 1.105 laser dust monitor. RESULTS: The particle size distribution in inhaled dust in the most characteristic workposts was analyzed. In the shoe manufacture plant, the concentrations ranged from 124 microg/m3 (leather cutting out) to 724 microg/m3 (scouring and milling of soles); concentrations of the thoracic and respirable fractions in the same workposts ranged from 74 microg/m3 to 412 microg/m3 and from 24 microg/m3 to 120 microg/m3, respectively. In the shoe repair workshop, the recorded concentrations were higher: the values ranged from 521 microg/m3 (gluing of shoes and soles, zipper exchange and heel abrasion) to 916 microg/m3 (uppers sewing and heel scouring) for the inhaled fraction; from 335 microg/m3 to 499 microg/m3 for the thoracic fraction; and from 88 microg/m3 to 120 microg/m3 for the respirable fraction. The mass median aerodynamic diameters of inhalable dust particles fell within the limits of 6.2-25.0 mm. Dust with the smallest particles (MMAD = 6.2 mm) was observed in shoe brushing and polishing, and with the largest particles (MMAD = 25.0 mm) in uppers sewing. CONCLUSIONS: The modern process of shoe manufacture is characterized by very low concentrations of inhalable dust and its fractions, they are considerably lower than occupational exposure limits in Poland for inhaled (4000 microg/m3) and respirable (2000 microg/m3) dust. In the workplaces under study, a relatively high proportion of extrathoracic fraction of leather dust was found, which supports a hypothesis on a potential etiologic role of this factor in the development of pathologies in the upper airways region.

Air Pollutants, Occupational↗

PubMed2001

17beta-estradiol affects in vivo the low density lipoprotein composition, particle size, and oxidizability.

The aim of this study was to explore the possible modifications induced by 17beta-estradiol (E(2)) in vivo on low-density lipoprotein (LDL) lipid composition, particle size, and oxidizability. For this purpose, women were recruited from an in vitro fertilization program, ranging their plasma E(2) levels from less than 12 pg/ml to more than 2000 pg/ml at the end of the treatment. The LDL lipid constituents were analyzed by thin layer chromatography and image analysis, and the LDL diameter was calculated from the lipid data. The results showed that high plasma E(2) levels were associated with smaller LDL particles, with lower amounts of free and esterified cholesterol and an increased relative content of alpha-tocopherol. The hormonal treatment produced a remodelation of the LDL acyl composition, rendering a lipoprotein enriched in saturated fatty acids, with a poorer polyunsaturated fatty acid content. These alterations in the physicochemical properties of LDL paralleled changes in the susceptibility of LDL to in vitro oxidation induced by both Cu(2+) and the peroxyl radical generator, 2,2'-azobis (2-amidinopropane), these changes being mainly reflected in a reduced maximum oxidation rate. The in vivo changes in the physicochemical properties of LDL induced by E(2) could explain some of the antiatherogenic actions of estrogens.

Adult↗

PubMed1999

Identification of retroviral late domains as determinants of particle size.

Retroviral Gag proteins, in the absence of any other viral products, induce budding and release of spherical, virus-like particles from the plasma membrane. Gag-produced particles, like those of authentic retrovirions, are not uniform in diameter but nevertheless fall within a fairly narrow distribution of sizes. For the human immunodeficiency virus type 1 (HIV-1) Gag protein, we recently reported that elements important for controlling particle size are contained within the C-terminal region of Gag, especially within the p6 sequence (L. Garnier, L. Ratner, B. Rovinski, S.-X. Cao, and J. W. Wills, J. Virol. 72:4667-4677, 1998). Deletions and substitutions throughout this sequence result in the release of very large particles. Because the size determinant could not be mapped to any one of the previously defined functions within p6, it seemed likely that its activity requires the overall proper folding of this region of Gag. This left open the possibility of the size determinant residing in a subdomain of p6, and in this study, we examined whether the late domain (the region of Gag that is critical for the virus-cell separation step) is involved in controlling particle size. We found that particles of normal size are produced when p6 is replaced with the totally unrelated late domain sequences from Rous sarcoma virus (contained in its p2b sequence) or equine infectious anemia virus (contained in p9). In addition, we found that the large particles released in the absence of p6 require the entire CA and adjacent spacer peptide sequences, whereas these internal sequences of HIV-1 Gag are not needed for budding (or proper size) when a late domain is present. Thus, it appears the requirements for budding are very different in the presence and absence of p6.

Animals↗