An Approach for Characterization and Lumping of Plus Fractions of Heavy Oil

2010 ◽  
Vol 13 (02) ◽  
pp. 283-295 ◽  
Author(s):  
I.. Rodriguez ◽  
A.A.. A. Hamouda
Keyword(s):  
Molecular Weight ◽  
Mole Fraction ◽  
Heavy Oil ◽  
Equations Of State ◽  
Carbon Number ◽  
Compositional Analysis ◽  
Volume Depletion ◽  
Molecular Weights ◽  
Pvt Data ◽  
Light Oil

Summary Heavy-oil fluids contain large concentrations of high-molecular-weight components, including a large content of the plus fractions, such as C7+. Different approaches have been developed to characterize the petroleum plus fractions to improve prediction of the pseudocomponents properties by equations of state (EOSs). A method is developed in this work to split the plus fraction into single carbon numbers (SCN), generating the mole fraction and the respective molecular weight. The developed method is based on the relationships between three-parameter gamma (TPG) distribution, experimental mole fraction, molecular weight, and SCN data obtained from the literature and industrial contacts. TPG is used to fit the trend of the compositional analysis. The characterized mole distribution as a function of SCNs is generated by integrating the TPG between the limiting molecular weights (LMw). The limiting molecular weights are determined simultaneously during the integration process by fitting the characterized and experimental mole fractions. The developed method is easy to use. In addition, the approach is not dependent on the assumption that only normal carbon numbers exist in the composition resulting on fixed molecular weights for each single carbon number. There are several correlations generated to predict physicochemical properties as a function of SCNs. Those correlations have been originally developed to work with light oil. Our approach is combined with some of the correlations and is tested for heavy-oil samples to identify the ranges in which they can be applied. Two lumping schemes are used to group the SCNs into pseudocomponents. The properties for each pseudo-component in this work are used to predict pressure/volume/temperature (PVT) data, constant volume depletion, using the Peng-Robinson EOS (PR-EOS), and the PVTP™ commercial simulator.

Estimation of Optimal Salinity and Solubilization Parameters for Alkylorthoxylene Sulfonate Mixtures

1977 ◽  
Vol 17 (03) ◽  
pp. 193-200 ◽  
Author(s):  
M.C. Puerto ◽  
W.W. Gale
Keyword(s):  
Molecular Weight ◽  
Enhanced Oil Recovery ◽  
Mole Fraction ◽  
Oil Recovery ◽  
Carbon Number ◽  
Constant Weight ◽  
Optimal Salinity ◽  
Interfacial Tensions ◽  
Molecular Weight Distributions ◽  
Weight Distributions

Abstract Economic constraints are such that it is unlikely a pure surfactant will be used for major enhanced oil recovery projects. However, it is possible to manufacture at competitive prices classes of syntheic and natural petroleum sulfonates that have fairly narrow molecular-weight distributions. Under some reservoir conditions, one of these narrow-distribution sulfonates may serve quite well as the basic component of a surfactant flood, however, in many instances a mixture of two or more of these may be required. Since evaluation of a significant subset of "all possible combinations" is a formidable undertaking screening techniques must be established that can reduce the number of laboratory core floods required. It is well known that interfacial tension plays a dominant role in surfactant flooding. It has recently been shown that minimal interfacial tensions occur at optimal salinity, Cphi, where the solubilization parameters VO/Vs and Vw/Vs are equal. Additionally, it has been shown that interracial tensions are inversely proportional to the magnitude of the solubilization parameters. This paper demonstrates that optimal salinity and solubilization parameters for any mixture of orthoxylene sulfonates can be estimated by summation of mole-fraction-weighted component properties. Those properties, which could not be properties. Those properties, which could not be measured directly, were obtained by least-squares regression on mixture data. Moreover, for surfactants of known carbon number distributions, equations that are linear in mole fractions of components and logarithmic in alkyl carbon number were found to be excellent estimators of both Cphi and solubilization parameters evaluated at Cphi. parameters evaluated at Cphi. Optimal salinity and associated solubilization parameters were measured using constant weight parameters were measured using constant weight fractions of alcohol cosolvents and mixtures of seven products with narrow molecular weight distributions. The average alkyl carbon number of these products varied from about 8 to 19. Alkyl chain lengths of individual surfactant chemical species ranged from 6 to 24 carbon atoms. Introduction Optimal salinity and the amounts of oil and water contained in a microemulsion have been shown to play important roles in obtaining low interfacial tensions and high oil recoveries. Since economics of enhanced oil recovery projects demand use of inexpensive surfactants, broad-distribution products likely will be chosen. Knowledge of how to estimate optimal salinity and oil-water contents of microemulsions prepared from such products would reduce time involved in laboratory screening procedures. This paper presents a method for procedures. This paper presents a method for obtaining such estimates that should prove useful for all types of surfactant mixtures that involve homologous series. The basic concept used is that a given property of a mixture of components (Yi) is related to the sum of products of mole fraction of components in the mixture (Xij) and the "mixing value" of the property in question for that component (Y'j). In property in question for that component (Y'j). In other words, (1) This approach is similar, for example, to the pseudocritical method used by Kay to calculate pseudocritical method used by Kay to calculate gas deviation factors at high pressures. The properties of interest in this paper are optimal properties of interest in this paper are optimal salinity and solubilization parameters, Vo/Vs, and Vw/Vs, at optimal salinity. Two separate approaches were developed that depended on the degree of detail of the available surfactant-composition data. In the first approach, only average molecular weights of several surfactant products were assumed known. Optimal salinity and products were assumed known. Optimal salinity and solubilization parameters could be measured for some, but not all, of the products. Regression on mixture data was used to estimate these quantities for the remainder of the products. Those properties, either measured experimentally or estimated from mixture data, are referred to as surfactant product contributions since they can be used as mixing values of the property in question in Eq. 1 or Eq. 2. SPEJ P. 193

Characterizing Hydrocarbon Plus Fractions

1983 ◽  
Vol 23 (04) ◽  
pp. 683-694 ◽  
Author(s):  
Curtis H. Whitson
Keyword(s):  
Molecular Weight ◽  
Specific Gravity ◽  
Physical Properties ◽  
Critical Pressure ◽  
Probability Function ◽  
Carbon Number ◽  
Physical Property ◽  
Molecular Weights ◽  
Property Estimation ◽  
Boiling Points

Whitson, Curtis H., SPE, U. of Trondheim Abstract Methods are developed for characterizing the molar distribution (mole fraction/molecular weight relation) and physical properties of petroleum fractions such as heptanes-plus (C7 +). These methods should enhance equation-of-state (EOS) predictions when experimental data are lacking. predictions when experimental data are lacking. The three-parameter gamma probability function is used to characterize the molar distribution, as well as to fit experimental weight and molar distributions and to generate synthetic distributions of heptanes-plus fractions. Equations are provided for calculating physical properties such as critical pressure and temperature properties such as critical pressure and temperature of single-carbon-number (SCN) groups. A simple three-parameter equation is also presented for calculating the Watson characterization factor from molecular weight and specific gravity. Finally, a regrouping scheme is developed to reduce extended analyses to only a few multiple-carbon-number (MCN) groups. Two sets of mixing rules are considered, giving essentially the same results when used with the proposed regrouping procedure. Introduction During the development of the application of EOS's to naturally occurring hydrocarbon mixtures, it has become clear that insufficient description of heavier hydrocarbons (e.g., heptanes and heavier) reduces the accuracy of PVT predictions. Volatile oil and gas-condensate volumetric phase behavior is particularly sensitive to composition and properties of the heaviest components. properties of the heaviest components. Until recently there has not been published in technical journals a comprehensive method for characterizing compositional variation, which we call "molar distribution." Several authors have given lucid descriptions of petroleum fraction characterization, though they deal mainly with physical property estimation. Usually, only physical property estimation. Usually, only a single heptanes-plus (C7 + ) fraction lumps together thousands of compounds with a carbon number higher than six. Molecular weight and specific gravity (or density) of the C7 + fraction may be the only measured data available. Preferably, a complete true-boiling-point (TBP) analysis should be performed on fluids to be matched by an EOS. Distillation experiments yield boiling points, specific gravities, and molecular weights, from which molar distribution is found directly. Special analyses of TBP data can also provide estimates of the paraffin/napthene/ aromatic (PNA) content of SCN groups, which are useful in some property correlations. Unfortunately, such high-quality data are seldom available for fluids being matched or predicted by an EOS. If data other than lumped C7+ properties are available, they might include a partial component analysis (weight distribution) from chromatographic measurements. In this case. only weight fractions of SCN groups are reported; normal boiling points, specific gravities, and molecular weights (needed to convert to a molar basis) simply are not available. Compositional simulation based on an EOS involves two major problems:how to "split" a C7 + fraction into SCN groups with mole fractions. molecular weights, and specific gravities that match measured C7+ properties, andif a partial extended analysis (e.g., C 11 + ) is available, how to extend it to higher carbon numbers. The first step in addressing these problems is to find a versatile, easy-to-use probability function for describing molar distribution. The distribution function should allow consistent matching and reasonable extension of partial analyses. Also, it should not contain too many unknown or difficult-to-determine parameters. This paper presents such a probabilistic model and describes its application to several reservoir fluids under "Molar Distribution."The second step in characterizing plus fractions involves estimating SCN group specific gravities, which, together with estimated molecular weights (from the probabilistic model), could be used to estimate critical properties required by EOS's. We address this problem and suggest a simple method for specific gravity estimation under "Physical Properties Estimation." SPEJ p. 683

Experimental Study of Compositional Factor on Asphaltene Deposition for Heavy Crude Oil Dilution in Offshore Production and Transportation

2016 ◽  
Author(s):  
Jiaqiang Jing ◽  
Cheng Wu ◽  
Xiaoshuang Chen ◽  
Junwen Chen ◽  
Ping Lu ◽  
...  
Keyword(s):  
Refractive Index ◽  
Heavy Oil ◽  
High Efficiency ◽  
Carbon Number ◽  
Prediction Method ◽  
Wire Mesh ◽  
Asphaltene Precipitation ◽  
Onset Point ◽  
Asphaltene Deposition ◽  
Light Oil

Heavy oil dilution has been widely used in the oil production and transportation due to its high efficiency in viscosity and drag reduction, and great convenience in operation. The composition of the heavy oil will change while being mixed with some diluents, thus the stability of the asphaltene in the heavy oil might be destroyed, which leads to a tremendous threat to the safe and economic operation of the production and transportation system. The asphaltene contents of eight onshore and offshore oil samples were measured using n-heptane and toluene, then the asphaltene deposition onset points of the oils diluted with n-alkanes (n-C7) were evaluated using viscosity methods. The reliability of the asphaltene deposition predicted by the refractive index of the diluted oils was verified, and meanwhile the impacts of n-C5, n-C7 and n-C8 on the asphaltene precipitation behavior were measured and analyzed. And then the status of the asphaltene deposition, suspending particle distribution and adhesion of the heavy oil diluted with diesel in the stainless wire mesh located in the visible loop pipe layout was investigated. The studied results demonstrate that the asphaltene deposition onset point has no direct relation to its content, and those of the eight diluted oils ranged from 15% to 30% at 70 °C. The onset point prediction method was verified to be reliable because it is based on that the critical solubility parameter and the square root of the diluent molar volume in the Asphaltene-Instability-Trend (ASIST) curve present a good linear relation. The relationship between the refractive index of the diluted oil and its asphaltene deposition onset point depends on the light oil type, and the smaller its carbon number, the more serious the asphaltene deposition in its diluted oil. The reasonable amount of a light oil blended with a heavy oil should well consider the light oil source, its economy and the asphaltene deposition risk at the same time.

PVT Behavior for Mixtures of Methane, Propane and C7 Hydrocarbons

1969 ◽  
Vol 9 (03) ◽  
pp. 338-342 ◽  
Author(s):  
Darryl S. Roberts ◽  
Charles R. Clark ◽  
George Swift
Keyword(s):  
Natural Gas ◽  
Mole Fraction ◽  
Carbon Number ◽  
Heavy Fraction ◽  
Gas Condensate ◽  
Reduced Pressure ◽  
Pvt Data ◽  
Naturally Occurring ◽  
Aromatic Components ◽  
Pvt Behavior

Abstract The purpose of this investigation was to measure PVT behavior of various types and combinations of PVT behavior of various types and combinations of heavy hydrocarbon components from the paraffinic, naphthenic and aromatic classes where the relative proportions of the various components were selected proportions of the various components were selected to approximate those of natural gas or gas condensate systems. Synthetic mixtures were used so that the compositions of the various components could be measured accurately. n-Heptane, methylcyclohexane and methylhenzene were used to represent the paraffinic, naphthenic and aromatic components of paraffinic, naphthenic and aromatic components of the heavy fraction. In the mixtures studied, the heavy fraction composition was held constant at 0.05-mole fraction, the balance being methane except for one mixture where 0.10-mole fraction of an intermediate component, propane, was added. The PVT data for the mixtures were determined in a variable-volume, constant-mass apparatus at psuedo-reduced temperatures from 1.84 to 2.00, over psuedo-reduced temperatures from 1.84 to 2.00, over a pseudo-reduced pressure range from 2.3 to 12.0. The experimental results showed that, regardless of the type of heavy material (paraffinic, naphthenic, aromatic, or combinations thereof) mixed with methane or methane and propane, the compressibility factors at equal values of pseudo-reduced temperature and pressure varied by less than 2.2 percent. pressure varied by less than 2.2 percent Introduction PVT data is used for natural gas and gas condensate fluids in determining reserves of reservoirs and performance of wells, in metering produced fluids, performance of wells, in metering produced fluids, and in recombining samples for laboratory studies. While there are vast amounts of PVT data reported for natural gas and gas condensate systems from which useful correlations have been developed, the compositional analyses for these systems and the resultant correlations typically were made with components analyzed through some arbitrary carbon number, usually C6, with the residue reported as a lumped "heavy" fraction. The heavy fraction was stoichiometrically recombined on the basis of an apparent molecular weight to give the final compositional analysis. It is virtually impossible to make a systematic analysis of the effect that variation of the relative amounts of paraffinic, naphthenic and aromatic constituents of the heavy fraction of natural systems might have on PVT behavior. Because there is considerable latitude in the relative amounts of these constituents, one speaks of crudes or condensate liquids as being "paraffin base", etc. It is of interest to determine if changes in the relative amounts of these three types of hydrocarbons in the heavy fraction cause significant changes in PVT behavior. If so, steps should be Taken to PVT behavior. If so, steps should be Taken to describe better the nature of the heavy fraction in PVT correlations. If not, more confidence can be PVT correlations. If not, more confidence can be placed in the correlations presently employed. placed in the correlations presently employed. DESIGN OF THE EXPERIMENTAL INVESTIGATION We attempted to determine if changes in the base of the heavy fraction would cause significant changes in the PVT behavior of gas or gas condensate fluids. Synthetic mixtures were used to enable us to systematically vary the base of the heavy fraction and to analyze accurately the fluids. We found that the heavy fraction of naturally occurring condensate systems seldom exceeds 0.05-mole fraction. Thus, the mole fraction of the heavy fraction in the synthetic systems studied was set arbitrarily at 0.05, to maximize whatever deviations in PVT behavior that might occur. Further, we judged that since the C7 hydrocarbons normally are present in greater quantities than higher carbon number hydrocarbons in naturally occurring systems, the use of n-heptane, methylcyclohexane, and methylbenzene to represent the paraffinic, naphthenic, and aromatic species in the heavy fraction would be most appropriate. SPEJ P. 338

Investigation by HPLC of the Catabolism of Recombinant Tissue Plasminogen Activator in the Rat

1988 ◽  
Vol 60 (01) ◽  
pp. 107-112 ◽  
Author(s):  
Roy Harris ◽  
Louis Garcia Frade ◽  
Lesley J Creighton ◽  
Paul S Gascoine ◽  
Maher M Alexandroni ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Half Life ◽  
Recombinant Tissue Plasminogen Activator ◽  
Rat Plasma ◽  
High Molecular Weight Complex ◽  
Molecular Weights ◽  
Major Activity ◽  
Tissue Plasminogen

SummaryThe catabolism of recombinant tissue plasminogen activator (rt-PA) was investigated after injection of radiolabelled material into rats. Both Iodogen and Chloramine T iodination procedures yielded similar biological activity loss in the resultant labelled rt-PA and had half lives in the rat circulation of 1 and 3 min respectively. Complex formation of rt-PA was investigated by HPLC gel exclusion (TSK G3000 SW) fractionation of rat plasma samples taken 1-2 min after 125I-rt-PA injection. A series of radiolabelled complexes of varying molecular weights were found. However, 60% of the counts were associated with a single large molecular weight complex (350–500 kDa) which was undetectable by immunologically based assays (ELISA and BIA) and showed only low activity with a functional promoter-type t-PA assay. Two major activity peaks in the HPLC fractions were associated with Tree t-PA and a complex having a molecular weight of ̴ 180 kDa. HPLC fractionation to produce these three peaks at various timed intervals after injection of 125I-rt-PA showed each to have a similar initial rate half life in the rat circulation of 4-5 min. The function of these complexes as yet is unclear but since a high proportion of rt-PA is associated with a high molecular weight complex with a short half life in the rat, we suggest that the formation of this complex may be a mechanism by which t-PA activity is initially regulated and finally cleared from the rat circulation.

Permeability Enhancing and Chemotactic Activities of Lower Molecular Weight Degradation Products of Human Fibrinogen

1981 ◽  
Vol 45 (01) ◽  
pp. 090-094 ◽  
Author(s):  
Katsuo Sueishi ◽  
Shigeru Nanno ◽  
Kenzo Tanaka
Keyword(s):  
Molecular Weight ◽  
Degradation Products ◽  
Electron Microscopic Observation ◽  
Chemotactic Activity ◽  
Lower Molecular Weight ◽  
Electron Microscopic ◽  
Human Fibrinogen ◽  
Rabbit Skin ◽  
Molecular Weights ◽  
Active Fragments

SummaryFibrinogen degradation products were investigated for leukocyte chemotactic activity and for enhancement of vascular permeability. Both activities increased progressively with plasmin digestion of fibrinogen. Active fragments were partially purified from 24 hr-plasmin digests. Molecular weights of the permeability increasing and chemotactic activity fractions were 25,000-15,000 and 25,000 respectively. Both fractions had much higher activities than the fragment X, Y, D or E. Electron microscopic observation of the small blood vessels in rabbit skin correlated increased permeability with the formation of characteristic gaps between adjoining endothelial cells and their contraction.These findings suggest that lower molecular weight degradation products of fibrinogen may be influential in contributing to granulocytic infiltration and enhanced permeability in lesions characterized by deposits of fibrin and/or fibrinogen.

Toxicity of Heparinoids, with Special Reference to the Precipitation of Fibrinogen

1964 ◽  
Vol 12 (01) ◽  
pp. 232-261 ◽  
Author(s):  
S Sasaki ◽  
T Takemoto ◽  
S Oka
Keyword(s):  
Molecular Weight ◽  
Dextran Sulfate ◽  
Anticoagulant Activity ◽  
Molecular Structures ◽  
Severe Reaction ◽  
Clinical Use ◽  
Molecular Weights ◽  
Close Relationship

SummaryTo demonstrate whether the intravascular precipitation of fibrinogen is responsible for the toxicity of heparinoid, the relation between the toxicity of heparinoid in vivo and the precipitation of fibrinogen in vitro was investigated, using dextran sulfate of various molecular weights and various heparinoids.1. There are close relationships between the molecular weight of dextran sulfate, its toxicity, and the quantity of fibrinogen precipitated.2. The close relationship between the toxicity and the precipitation of fibrinogen found for dextran sulfate holds good for other heparinoids regardless of their molecular structures.3. Histological findings suggest strongly that the pathological changes produced with dextran sulfate are caused primarily by the intravascular precipitates with occlusion of the capillaries.From these facts, it is concluded that the precipitates of fibrinogen with heparinoid may be the cause or at least the major cause of the toxicity of heparinoid.4. The most suitable molecular weight of dextran sulfate for clinical use was found to be 5,300 ~ 6,700, from the maximum value of the product (LD50 · Anticoagulant activity). This product (LD50 · Anticoagulant activity) can be employed generally to assess the comparative merits of various heparinoids.5. Clinical use of the dextran sulfate prepared on this basis gave satisfactory results. No severe reaction was observed. However, two delayed reactions, alopecia and thrombocytopenia, were observed. These two reactions seem to come from the cause other than intravascular precipitation.

Molecular Weights of Factor VIII (AHF) and Factor IX (PTC) by Electron Irradiation

1962 ◽  
Vol 08 (02) ◽  
pp. 270-275 ◽  
Author(s):  
David L Aronson ◽  
John W Preiss ◽  
Michael W Mosesson
Keyword(s):  
Molecular Weight ◽  
Factor Viii ◽  
Electron Irradiation ◽  
Factor Ix ◽  
Molecular Weights

SummaryThe molecular weights of AHF (factor VIII) and of PTC (factor IX) have been estimated by their sensitivity to inactivation by 7 kilovolt electrons. The molecular weight of AHF was found to be 180 000 by this method and that of PTC was found to be 110 000.

scholarly journals Effects of Molecular Weight of Functionalized Liquid Butadiene Rubber as a Processing Aid on the Properties of SSBR/Silica Compounds

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 850
Author(s):  
Donghyuk Kim ◽  
Byungkyu Ahn ◽  
Kihyun Kim ◽  
JongYeop Lee ◽  
Il Jin Kim ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Anionic Polymerization ◽  
High Performance ◽  
Crosslink Density ◽  
Functional Group ◽  
Vital Role ◽  
Butadiene Rubber ◽  
Molecular Weights ◽  
Mooney Viscosity ◽  
Silica Dispersion

Liquid butadiene rubber (LqBR) which used as a processing aid play a vital role in the manufacturing of high-performance tire tread compounds. However, the studies on the effect of molecular weight, microstructure, and functionalization of LqBR on the properties of compounds are still insufficient. In this study, non-functionalized and center-functionalized liquid butadiene rubbers (N-LqBR and C-LqBR modified with ethoxysilyl group, respectively) were synthesized with low vinyl content and different molecular weights using anionic polymerization. In addition, LqBR was added to the silica-filled SSBR compounds as an alternative to treated distillate aromatic extract (TDAE) oil, and the effect of molecular weight and functionalization on the properties of the silica-filled SSBR compound was examined. C-LqBR showed a low Payne effect and Mooney viscosity because of improved silica dispersion due to the ethoxysilyl functional group. Furthermore, C-LqBR showed an increased crosslink density, improved mechanical properties, and reduced organic matter extraction compared to the N-LqBR compound. LqBR reduced the glass transition temperature (Tg) of the compound significantly, thereby improving snow traction and abrasion resistance compared to TDAE oil. Furthermore, the energy loss characteristics revealed that the hysteresis loss attributable to the free chain ends of LqBR was dominant.

scholarly journals Nuclear matrix of HeLa S3 cells. Polypeptide composition during adenovirus infection and in phases of the cell cycle.

1977 ◽  
Vol 72 (1) ◽  
pp. 194-208 ◽  
Author(s):  
L D Hodge ◽  
P Mancini ◽  
F M Davis ◽  
P Heywood
Keyword(s):  
Cell Cycle ◽  
Molecular Weight ◽  
Nuclear Matrix ◽  
Apparent Molecular Weight ◽  
Molecular Weight Range ◽  
Weight Range ◽  
Molecular Weights ◽  
Liver Nuclei ◽  
Hela S3 ◽  
Biochemical Analyses

A subnuclear fraction has been isolated from HeLa S3 nuclei after treatment with high salt buffer, deoxyribonuclease, and dithiothreitol. This fraction retains the approximate size and shape of nuclei and resembles the nuclear matrix recently isolated from rat liver nuclei. Ultrastructural and biochemical analyses indicate that this structure consists of nonmembranous elements as well as some membranous elements. Its chemical composition is 87% protein, 12% phospholipid, 1% DNA, and 0.1% RNA by weight. The protein constituents are resolved in SDS-polyacrylamide slab gels into 30-35 distinguishable bands in the apparent molecular weight range of 14,000 - 200,000 with major peptides at 14,000 - 18,000 and 45,000 - 75,000. Analysis of newly synthesized polypeptides by cylindrical gel electrophoresis reveals another cluster in the 90,000-130,000 molecular weight range. Infection with adenovirus results in an altered polypeptide profile. Additional polypeptides with apparent molecular weights of 21,000, 23,000, and 92,000 become major components by 22 h after infection. Concomitantly, some peptides in the 45,000-75,000 mol wt range become less prominent. In synchronized cells the relative staining capacity of the six bands in the 45,000-75,000 mol wt range changes during the cell cycle. Synthesis of at least some matrix polypeptides occures in all phases of the cell cycle, although there is decreased synthesis in late S/G2. In the absence of protein synthesis after cell division, at least some polypeptides in the 45,000-75,000 mol wt range survive nuclear dispersal and subsequent reformation during mitosis. The possible significance of this subnuclear structure with regard to structure-function relationships within the nucleus during virus replication and during the life cycle of the cell is discussed.

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