Spherical Macromolecules Research Articles

The Characterization of a Discrete Series of Low Density Lipoproteins in the Disease, Hyper-pre-β-lipoproteinemia: IMPLICATIONS RELATING TO THE STRUCTURE OF PLASMA LIPOPROTEINS

Abstract Five separate low density lipoproteins (LD lipoproteins) have been isolated from the plasma of a group of subjects with the disease hyper-pre-β-lipoproteinemia. These lipoproteins have been shown to be discrete, stable components within the LD lipoprotein class which may be isolated repeatedly, by differential density ultracentrifugation, from the serum of these subjects. Immunological study of the delipidized apoproteins shows only a reactivity with the LD lipoprotein antiserum. Electron microscopy reveals spherical macromolecules. Their sedimentation coefficients and hydrated densities have been measured, and their calculated average molecular weights are 4.9, 4.3, 3.2, 2.5, and 1.3 million. Compositional studies show an increasing lipid content with increasing molecular size. Of particular interest is the observation that the mass of protein per mole of lipoprotein remains constant although the molecular weight of these lipoproteins more than doubles, and thus the LD liproprotein components differ only in their lipid content. On the basis of equilibrium-banding experiments in linear density gradients, it is concluded that these lipoproteins exist within the LD lipoprotein class as discrete entities which presumably constitute energetically favorable associations of lipid and protein. Based on the sequential nature of their molecular weights and their known composition, it appears that these lipoproteins may be generated by the addition of specific increments or packets of lipid consisting of multiples of 6.25 x 105 g per mole of lipoprotein. It is postulated that the periodicity observed in the molecular weights reflects the structural limitations imposed upon these macromolecules by the apoprotein which determines the amount of lipid which may be bound. The marked density and molecular weight heterogeneity observed within the lipoproteins constituting the LD lipoprotein class in these subjects with the disease hyper-pre-β-lipoproteinemia is in apparent contrast to that observed with LD lipoprotein from normal subjects. It is thus tempting to speculate that a structurally altered apoprotein occurs in these patients which binds lipid in an atypical fashion and thus generates the multiple components found within the LD lipoprotein class of these subjects with this familial disease.

The Characterization and Occurrence of an Sf 20 Serum Lipoprotein

Abstract In the serum of patients with hyper-pre-β-lipoproteinemia there frequently occurs in abundance an ultracentrifugally distinct low density lipoprotein component of the Sf 20 class. This study concerns the characterization of this component, present in the serum of 14 of 15 patients. The lipoprotein has been isolated ultracentrifugally; it has the electrophoretic and immunological properties of a β-lipoprotein but is distinct from very low density lipoproteins. It has a buoyant density of 1.004 g per ml which is lighter than the major low density lipoproteins of normal serum, and this observation is consistent with its higher triglyceride content. This lipoprotein has a sedimentation coefficient corrected for concentration and viscosity of -68 S, measured in a solvent of density 1.20 g per ml, and a molecular weight of approximately 4.2 million. Electron microscopy of this larger low density lipoprotein shows spherical macromolecules with a diameter approximating 256 A.

On the estimation of the shape of macromolecules from sedimentation and viscosity measurements.

Current theories for the interpretation of sedimentation and viscosity data are discussed, with particular reference to those substances where experimental uncertainties preclude the application of the Scheraga-Mandelkern β function. Attention is directed to the ratio of Ks (the coefficient of concentration-dependence of the reciprocal sedimentation coefficient) to [η], the intrinsic viscosity. This ratio was reported by Wales and Van Holde to be a constant equal to about 1.6 for all random-coil polymers, and a theoretical basis for this constancy was derived; the ratio is also of fundamental importance in the “porous-plug” theory of Ogston and the polymer theory of Yamakawa. From a survey of existing data, it is shown here that compact spherical macromolecules also give Ks/[η] values of about 1.6, whereas those macromolecules known to be asymmetric give lower values. These observations form the basis of a method for distinguishing between the separate contributions of asymmetry and expansion of form to the intrinsic viscosity.

A periodic acid schiff-staining macromolecular component of human hepatic bile

A method has been developed for isolating and purifying a macromolecular water-soluble component from human hepatic bile by precipitation from barbital solution. The purity and homogeneity of the component have been demonstrated by paper electrophoresis, ultracentrifugation and electron microscopy. The component is a mucoprotein composed of nearly spherical macromolecules 150 Å in diameter with an extrapolated sedimentation constant in water of 22.6 S. The presence of the mucoprotein in human bile may be correlated with the occurrence of cholecystitis and biliary calculi.

Interaction between particles suspended in solutions of macromolecules

AbstractAn attractive force appears between particles suspended in solutions of macromolecules when there is neither direct interaction between two particles nor energetic interaction between particles and solute macromolecules. The magnitude of this force is of the order of the osmotic pressure of the solution of macromolecules and the range is of the order of the diameter of macromolecules. This force is calculated as a function of concentration, shape, and charge of macromolecules, and it is shown that it becomes stronger in solutions of chain macromolecules or of macromolecules of dissymmetrical shape than in solutions of rigid spherical macromolecules at the same net concentration. If macromolecules have charge, the force can be greatly intensified. In every case numerical estimation is made, and it is found that actually this kind of force can have a remarkable influence on the state of suspended particles. Numerical examples of the critical concentration of particles at their macroscopic aggregation are given. Finally a short description is added on the effect of energetic interaction between particles and macromolecules.

The Lennard-Jones Potential for Spherical Macromolecules

The Lennard-Jones Potential for Spherical Macromolecules

An X-ray investigation of the sizes and hydrations of three spherical virus macromolecules in solution

We have measured the small-angle X-ray scattering from dilute aqueous solutions of southern bean mosaic virus, tobacco necrosis virus, and tomato bushy stunt virus. All of these virus particles are nearly spherical. Values of the sphere diameter obtained by a comparison of our curves with curves of the exact scattering function for spheres are SBMV = 286 A, TNV = 280 A and TBSV = 309 A. A comparison of these values with other molecular constants strongly suggests that they are internally hydrated. The effects upon the experimental curves of interparticle interference and of slit dimensions for the X-ray collimating system are considerable and have been taken into account.

A macromolecular mono-layer in the cell wall of Spirillum spec

The flagella and the cell wall have been studied in a bacterium apparently belonging to the genus Spirillum. Owing to the twined condition of each bundle of flagella the bundles are easily visible in the phase-contrast microscope. The cell wall is composed of at least two membranes. The outer one contains or consists of a single layer of what may be spherical macromolecules with a diameter of 120–140 A. These are arranged in a hexagonal pattern.

The radical distribution functions of electrically charged macromolecules in solution

AbstractRepresentative radial distribution functions of electrically charged spherical macromolecules, interacting with a screened Coulomb potential, in electrolytic solutions, are determined by means of the statistical mechanical theory of distribution functions in fluid mixtures. At high concentrations locally ordered clusters, characteristic of liquid structure, are established. The degree of local order in the clusters increases with the magnitude of the double layer potential and decreases with increasing ionic strength of the solution.

Multiplication of the T3 Bacteriophage Against E. coli.

SummaryCultures of young, rapidly growing susceptible colon bacilli obtained after hourly transplants to fresh broth appear quickly lysed by the addition of T3 bacteriophage. Electron micrographs show that the bacterial membranes rupture very soon after adsorption of bacteriophage and that colonies of new phage particles rapidly appear in the protoplasmic masses. This protoplasm from young cells is the same assemblage of spherical macromolecules seen after lysis with T2 phage. As was the case with this other phage the observed phenomena are those to be expected of particles behaving as if they were minute microorganisms multiplying by division at the expense of the bacterial protoplasm.

Cellulose, Starch and Glycogen

A VALUABLE article on recent work on cellulose, starch and glycogen, by Prof. H. Staudinger, has appeared in a recent issue of Die Naturwissenschaften (25, 673 ; 1937). The fact that cellulose, starch and glycogen can be converted into esters without altering the degree of polymerization, and can be reconverted into the original substances, as shown by molecular weight determinations, optical rotation and other properties, shows that the glucose residues in the colloidal particles of these substances are linked by principal valencies. The colloidal particles are therefore macro-molecules. The determination of the molecular weights of these substances is discussed. The ebullioscopic and cryoscopic methods are difficult to apply owing to the smallness of the effect, and other anomalies ; but molecular weights can be satisfactorily determined from osmotic pressure data using the equation of Schulz, or by Svedberg's method using the ultra-centrifuge. It is also possible to determine them from viscosity data by an equation due to Staudinger. All these methods agree in giving a value about 200,000 for the molecular weight. X-ray analysis shows the molecule of solid cellulose to be extended, and there is reason for believing that this is also the case in solution. Viscosity determinations show, however, that in starch there is a bending back of the molecules. Starch molecules are only about one eighth as long as they should be if extended. With glycogen, solutions of the same concentration have the same viscosity, no matter what the degree of polymerization. This points to the existence of spherical macro molecules in this case. The linking of the glucose residues in these three compounds is discussed, and the connexion between physical properties and the shape of the molecule is emphasized.