Macromolecules In Aqueous Solution Research Articles

Crude‐tissue‐extract analysis by micro‐electrophoresis in cylindrical continuous polyacrylamide gradient gels

AbstractContinuous gradient gels in capillaries with acrylamide concentrations ranging from 2–20 % or alternatively from 2–40 % are equally suited for the fractionation of complex mixtures of macromolecules in aqueous solutions within a range of molecular weights from 103‐106. A time‐saving method for the simultaneous preparation of up to 48 identical linear micro‐gradient polyacrylamide gels is described. With this method it was possible to compare the patterns of aqueous extracts and to determine tissue‐specific bands of the moss Funaria hygrometrica L. Sibth. in the low molecular weight range for the first time.

The thermodynamic properties of aqueous polyacrylamide solutions

The molecular weight, the magnitude and the second virial coefficient, A 2, of polyacrylamide macromolecules in aqueous solutions have been determined by light scattering. The large A 2 value indicates water to be a very good solvent of the polyacrylamide (PAA). A 2 has been found to decrease in the 20–80°C range while the radius of inertia of the coils ( R z 2) 1 2 and the intrinsic viscosity remain constant in practice.

Dilute solutions of polyelectrolytes—III. Unperturbed dimensions of poly(methylene) N, N-dimethylpiperidinium chloride) in aqueous and methanolic solutions in presence of tetraethylammonium bromide

The behaviour of poly(methylene N, N-dimethylpiperidinium chloride) in aqueous and methanolic solutions in the presence of tetraethylammonium bromide has been investigated by light scattering; the parameters characterizing the macromolecular chain have been calculated. Peculiar behaviour of the macromolecules in aqueous solutions was attributed to the influence of the simple electrolyte co-ion due to hydrophobic interactions.

A solution to the rotational diffusion equation to describe molecular orientation due to a time dependent torque

When aqueous solutions of macromolecules are placed in a square, pulsed, orienting electric field they frequently become dichroic and birefrigent. By following the rise of the optical anisotropy as a function of time after application of the pulse one can frequently distinguish between permanent and induced dipole orientation modes. Occasionally, molecules which for symmetry or other reasons are known to have no permanent dipole moment mimic permanent moment orientation. A possible explanation for this phenomenon is that the induced dipole is time dependent. Here we present a formal solution to the rotary diffusion equation for a molecule subjected to a time dependent torque due to an induced dipole mechanism. A new method of solution which can have broad application has been employed. The results are seen to be a viable explanation for the subject in question.

Ion effects on macromolecules in aqueous solution

APART from their nonspecific electrostatic interactions, ions can produce specific effects on the conformation and solubility of macromolecules in aqueous solution1. The relative effectiveness of anions and cations in altering macromolecular configurations is remarkably independent of the nature of the macromolecule and is generally referred to as the lyotropic or Hofmeister series. To explain the generality of the effects, the influence of the ions on the structure of the solvent has often been invoked, but as yet no theory has been able to link satisfactorily ion–water interactions with the effects of ions on macromolecules. We argue here that it is the effect of the ions on the empty volume of the solvent which underlies the Hofmeister series and we derive a simple thermodynamic equation which accounts for the effect of a salt on the transition temperature for a polymer chain aggregation process. To test the equation we have taken data from the literature relating to the cloud point of polyvinylmethylether (PVME; intermolecular aggregation); and to the thermal transition temperature of ribonuclease (intramolecular aggregation).

Molecular conformation of bovine A1 basic protein, a coiling macromolecule in aqueous solution.

Aqueous solutions of bovine A1 protein, the major component of the basic protein fraction of myelin, were studied by small angle X-ray diffraction. The experimentally determined molecular weight, 17,800, is within 3% of that corresponding to the amino acid sequence, 18, 395, and the radius of gyration was found to be 46.3 A. No equivalent scattering particle of uniform electron density could be found which was compatible with all parameters evaluated from the diffraction measurements. The possibility of a coiled shape was therefore investigated using a worm-like chain model. This yielded a contour length of 439 A and a persistence length of 15.7 A. The radius of gyration of this model chain, 47.1 A, is in quite reasonable accord with the experimental value. The latter, after correction for excluded volume effects and finite chain length, yields for the characteristic ratio, ro2/nplp-2, 5.4. This may be compared with the value, 6.1, obtained after applying a correction for finite chain length to the viscosity data given by Tanford et al. for 12 proteins in 6 M guanidine hydrochloride and 0.1 M beta-mercaptoethanol. These two experimental values fall in the expected order, since the 15% glycine content of the A1 protein is considerably higher than the average for other proteins, which is about 8%. The corresponding values predicted from conformational calculations by Miller et al. for random copolymers of the L-alanine-glycine type are 5.9 (18% glycine) and 7.0 (8% glycine). We conclude that the A1 protein exists predominately, if not exclusively, as a random coil in aqueous solution.

Some physico-chemical properties and sorption ability of benzylated polyethyleneimines in aqueous solutions

An investigation has been made on the change in the physico-chemical properties of aqueous solutions of branched and linear polyethyleneimine (a high mol. wt catalyst for hydrolysis of nitrophenyl esters) occurring on its being alkylated by benzyl chloride. The first result of alkylation is benzyldiethylamine fragments in PEI. Provided that the degree of conversion is below 0–3, the reaction is second order. Then the rate constant decreases, probably due to a decrease in the steric factor. Alkylation diminishes p K a 's of nitrogen atoms of PEI. Accumulation of benzyl groups in PEI results in a marked contraction of its macromolecules in aqueous solutions and enhances the sorption ability with respect to n-nitroanilides. The free energy of sorption is −4 · 1 to − 5·5 kcal/mole.

Nucleic acid-solvent interactions: temperature dependence of the heat of solution of thymine in water and ethanol.

AbstractThe heats of solution of thymine in water and ethanol have been determined calorimetrically as a function of temperature. These data, along with solubility data, have been used to calculate the thermodynamic quantities (ΔGt, ΔHt, ΔSt and ΔCp,t) associated with the transfer of thymine from ethanol to water. Since ΔSt = −2 cal/mole deg and ΔCp,t = 0, it has been concluded that hydrophobic bonding does not play an important role in the thermocynamic stability of nucleic acids.However, large heat capacities of solution of thymine are observed in both solvents (ΔC°p2 = 45 ± 4 cal/mole deg). This is explained in terms of temperature variation in the degree of solvent–solute hydrogen bonding. It is our proposal that the components of macromolecules (i.e., nucleic acid bases and amino acids) do not make all possible hydrogen bonds with the solvent in the vicinity of room temperature. Thus the thermodynamic contribution of hydrogen bonding to the stability of macromolecules in aqueous solution must be reassessed.

Kinetic and hydrodynamic studies relating to the structure of the amylose macromolecule in aqueous solution.

Kinetic and hydrodynamic studies relating to the structure of the amylose macromolecule in aqueous solution.

Volume effects in aqueous solutions of macromolecules containing non‐polar groups

AbstractSpecific volumes at 25° of aqueous solutions of poly(N‐methyl acrylamide) and poly‐(ethylene oxide) have been measured, and the data obtained is compared with corresponding data on low‐molecular‐weight compounds. The results support the notion, that the volume changes following the interaction between aliphatic groups and water are positive. They are discussed with particular reference to pressure effects on protein conformations.

The application of polyethylene glycol solubility-concentration gradients in plant virus research

A simple method for determining the solubility of plant viruses and other macromolecules in aqueous solutions of polyethylene glycol (PEG) is described. The method involves centrifugation of PEG-precipitated virus through a reverse concentration gradient of PEG, MW 6000, incorporated and stabilized in a positive sucrose gradient. The concentration of PEG at which the virus particles resolubilize is termed the solubility concentration. The solubility concentration of virus particles for a number of model systems was dependent upon their surface/volume ratio and their surface charge characteristics, the latter in turn depending on the pH and ionic conditions existing within the solubility gradient. Solubility gradient centrifugations were of value both analytically, in providing information for purification procedures and in the characterization of viruses and virus strains, and preparatively, allowing separation of certain morphologically or electrophoretically distinct components. The technique of solubility gradient centrifugation is potentially applicable to other systems having distinct solubility characteristics in an appropriate solvent.

Polymerization of 4-vinylpyridine on polyphosphate macromolecules in aqueous solution

Polymerization of 4-vinylpyridine on polyphosphate macromolecules in aqueous solution

Polyethylene glycol solubility gradients, a new and rapid technique for investigations of plant viruses

A simple method for determining the solubility of plant viruses and other macromolecules in aqueous solutions of polyethylene glycol (PEG) is described. The method involves centrifugation of PEG-precipitated virus through a reverse concentration gradient of PEG, MW 6000, incorporated and stabilized in a positive sucrose gradient. The concentration of PEG at which the virus particles resolubilize is termed the solubility concentration.The solubility concentration of virus particles for a number of model systems was dependent upon their surface/volume ratio and their surface charge characteristics, the latter in turn depending on the pH and ionic conditions existing within the solubility gradient.Solubility gradient centrifugations were of value both analytically, in providing information for purification procedures and in the characterization of viruses and virus strains, and preparatively, allowing separation of certain morphologically or electrophoretically distinct components. The technique of solubility gradient centrifugation is potentially applicable to other systems having distinct solubility characteristics in an appropriate solvent.

Thermostating Capillary Cells for a Laser—Raman Spectrophotometer

An important application of laser-Raman spectroscopy is for the study of structures and interactions of biological macromolecules in aqueous solution.1 A number of nucleic acids, proteins, and related model compounds have recently been studied using this method.2–6 In such investigations, control of thesample temperature is critical because biopolymers generally undergo changes in conformation with temperature. Thermal control at the sample may also be required in other Raman applications.7

Freezing of Aqueous Solutions of Macromolecules

Freezing of Aqueous Solutions of Macromolecules

Liquid Chromatographic Separation of Mixtures of Polymers and Mineral Oil

Porath and Flodin1 have shown that macromolecules in aqueous solutions may be separated from low molecular weight compounds by liquid chromatography using a cross-linked dextran (‘Sephadex’) as the stationary phase, and water as the mobile phase. It has now been found in these laboratories that polymers dissolved in mineral oil can be separated by a similar Chromatographic technique. Small pieces of thin vulcanized natural rubber latex are used as the stationary phase, and a light paraffin hydrocarbon as the mobile phase.