Propriétés hydrodynamiques des conformations ordonnées et desordonnées du poly(γ-L-glutamate de benzyle): dimensions et flexibilité de la chaîne

1978 ◽  
Vol 56 (11) ◽  
pp. 1569-1574
Author(s):  
Nga Ho-Duc
Keyword(s):  
Quantitative Agreement ◽  
Dichloroacetic Acid ◽  
Random Coil ◽  
Hydrodynamic Properties ◽  
Molecular Weights ◽  
Coil Transition ◽  
Rigid Segment ◽  
Good Agreement ◽  
Stiff Chain

Theoretically we can determine the disordered or ordered structure of polypeptides and their dimensions in dilute solutions from hydrodynamic properties. We have presently a wealth of theories for random coil chains and a limited but sufficient number of theories for ordered chains for interpreting experimental results.Viscosity data for seven poly(γ-benzyl-L-glutamate) samples in 1,2-dichloroethane at 25 °C are analyzed and the length per monomeric residue (h) is calculated according to the equivalent ellipsoid approach. The degree of flexibility or rigidity is characterized by calculating Ns, the number of monomer units in a rigid segment or a Kuhn statistical segment; the determination of Ns is made by applying Yamakawa and Fujii's equation modified by Vitovskaya and Tsvetkov.Values obtained for h assuming the solute molecule to be a rigid, stiff chain, range between 1.3 to 2 Å. One notices that the h value close to 1.5 Å is found for the three following molecular weights: 1.8 × 105, 1.7 × 105, and 1.5 × 105. They are, in fact, the samples having a length in good quantitative agreement with that of the rigid segment determined by the method of Vitovskaya and Tsvetkov. This rigid segment corresponds to a sample of 700 ± 100 monomer units.The analysis of the experimental data of poly(γ-benzyl-L-glutamate) in dichloroacetic acid indicates that, in addition to the formation of hydrogen bonds, other interactions between the polypeptide and the solvent are present.In summary, we may conclude that the study of the helix–coil transition using hydrodynamic measurements is judged satisfactory but the determination of characteristic dimensions used to describe exactly the conformation of the macromolecule is somewhat ambiguous. One major problem is the degree of flexibility encountered with high molecular weight chains. However, to get around this difficulty, we propose, according to our results, a method which consists in determining the number of monomer units within a rigid segment from the different values found for h and then the dimensions from the samples for which the chain length is in good agreement with that of a rigid segment thus determined.

Measurement of the Isothermal Volume Dilation Accompanying the Unilateral Extension of Rubber

1959 ◽  
Vol 32 (2) ◽  
pp. 428-433
Author(s):  
Fred G. Hewitt ◽  
Robert L. Anthony
Keyword(s):  
Molecular Weight ◽  
Young’S Modulus ◽  
Experimental Results ◽  
Molecular Weights ◽  
Rubber Specimen ◽  
A Value ◽  
Fractional Increase ◽  
Internal Agreement ◽  
Good Agreement

Abstract The fractional increase in volume accompanying the isothermal extension of soft gum rubber was measured for four rubber samples at mean extensions of 14, 33, and 51%. The chain molecular weights Mc of the four samples were 5500, 5100, 4400, and 3000, with an estimated uncertainty of about 10% in each value of Mc. The observed fractional increase in volume ranged from 3.2×10−5 to 142×10−5, the latter value being observed for the sample of lowest chain molecular weight and at the extension of 51%. The experimental results for each sample have been represented by theoretical curves based on Gee's expression for the fractional increase in volume as a function of the sample extension. The theoretical curves exhibit good agreement with those of Gee, Stern, and Treloar. The process of fitting the theoretical curves to the experimental points constituted a determination of Young's modulus E for each rubber specimen. As a check on the experimental results, and also on the theory employed, determinations of E were also made by two additional methods, namely, from rough stess-strain curves, and from the relation E=3γρRT/Mc. With one exception, the internal agreement between the three determinations of E for the four different samples was satisfactory. The exception noted can probably be ascribed to the use of too small a value of Mc for the sample of lowest chain molecular weight.

MOLECULAR WEIGHT AND HYDRODYNAMIC PROPERTIES OF SODIUM ALGINATE

1954 ◽  
Vol 32 (3) ◽  
pp. 227-239 ◽  
Author(s):  
W. H. Cook ◽  
David B. Smith
Keyword(s):  
Molecular Weight ◽  
Sodium Alginate ◽  
Intrinsic Viscosity ◽  
Diffusion Coefficients ◽  
Linear Relation ◽  
Hydrodynamic Properties ◽  
Viscosity Measurements ◽  
Molecular Weights ◽  
Extension Ratio ◽  
Good Agreement

Sedimentation, diffusion, and viscosity measurements were made on five unfractionated samples of sodium alginate ranging in intrinsic viscosity from 3.1 to 17.5. Diffusion coefficients were subject to large errors and are believed to be overestimated.Though the molecular weights obtained from sedimentation–diffusion (Svedberg equation) and sedimentation – intrinsic viscosity (Perrin–Simha equations) showed good agreement and yielded values of 3 to 21 × 104, higher values (4.6 to 37 × 104) from sedimentation–viscosity (Mandelkern–Flory equation) appear to be the better estimates. A linear relation between intrinsic viscosity and molecular weight was found with a slope (Mandelkern–Flory equation values) equivalent to Km = 13.9 × 10−3. The results indicate that sodium alginate has a relatively high extension ratio.

MOLECULAR WEIGHT AND HYDRODYNAMIC PROPERTIES OF SODIUM ALGINATE

1954 ◽  
Vol 32 (1) ◽  
pp. 227-239 ◽  
Author(s):  
W. H. Cook ◽  
David B. Smith
Keyword(s):  
Molecular Weight ◽  
Sodium Alginate ◽  
Intrinsic Viscosity ◽  
Diffusion Coefficients ◽  
Linear Relation ◽  
Hydrodynamic Properties ◽  
Viscosity Measurements ◽  
Molecular Weights ◽  
Extension Ratio ◽  
Good Agreement

Sedimentation, diffusion, and viscosity measurements were made on five unfractionated samples of sodium alginate ranging in intrinsic viscosity from 3.1 to 17.5. Diffusion coefficients were subject to large errors and are believed to be overestimated.Though the molecular weights obtained from sedimentation–diffusion (Svedberg equation) and sedimentation – intrinsic viscosity (Perrin–Simha equations) showed good agreement and yielded values of 3 to 21 × 104, higher values (4.6 to 37 × 104) from sedimentation–viscosity (Mandelkern–Flory equation) appear to be the better estimates. A linear relation between intrinsic viscosity and molecular weight was found with a slope (Mandelkern–Flory equation values) equivalent to Km = 13.9 × 10−3. The results indicate that sodium alginate has a relatively high extension ratio.

Helix to coil transition in poly-L-amino acids. II. N.M.R. study of model compounds and Poly-γ-benzyl-L-glutamate

1969 ◽  
Vol 22 (2) ◽  
pp. 357 ◽  
Author(s):  
JH Bradbury ◽  
MD Fenn
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Magnetic Resonance ◽  
Amide Group ◽  
Dichloroacetic Acid ◽  
Model Systems ◽  
Optical Rotatory Dispersion ◽  
Random Coil ◽  
Low Molecular Weight ◽  
Coil Transition

The proton magnetic resonance spectroscopy of simple amides and poly-L- amino acids has been investigated with particular reference to the question of charging of the amide group in strong acids. It is found that the downfield chemical shift of the α-CH resonance of poly-γ- benzyl-L-glutamate (PBG) which accompanies the helix to coil transition can be conveniently divided into two parts on the basis of experiments with model systems. The first is due to the collapse of the helix to an uncharged random coil and the second represents the charging of the amide groups of the random coil. For PBG samples of low molecular weight, two α-CH resonances are observed due to residues in helical (uncharged) and random-coil (charged) forms. The rate of exchange between them is of the order of 400 sec-1. The proton resonances of the NH proton, COOH proton of the acid, and α-CH proton of dichloroacetic acid (DCA) are shown to be less useful than the α-CH proton. A critical evaluation has been made of all the evidence relevant to the charging of the amide group of polypeptides in mixtures of non-interacting solvents and organic acids e.g. trifluoroacetic acid (TFA) and DCA. It is concluded that viscosity, infrared, dielectric constant, electric birefringence, and conductivity studies give overwhelming support to the concept of charging. Nuclear magnetic resonance, circular dichroism, and optical rotatory dispersion are less sensitive indicators of small amounts of charging, and hence studies should be made with samples of low molecular weight (where there is a greater fractional degree of charging). Such studies made here by n.m.r. methods give strong support for charging. The features of the flexible helix model first proposed in Part I are delineated. It consists of helical segments separated by short, charged random-coil breaks at both ends and in the interior of the molecule. Although elaborated in some detail for the case of PBG, it is likely to occur quite generally for those polypeptides which are soluble in organic solvents and undergo the helix to coil transition.

Transmission Electron Microscopy of Protein Macromolecules

1971 ◽  
Vol 29 ◽  
pp. 424-425
Author(s):  
Henry S. Slayter
Keyword(s):  
Biological Systems ◽  
Metal Vapor ◽  
Resolving Power ◽  
Electron Microscopic ◽  
Chemical Methods ◽  
Molecular Weights ◽  
The Past ◽  
Physical Chemical ◽  
Transmission Electron

Electron microscopic methods have been applied increasingly during the past fifteen years, to problems in structural molecular biology. Used in conjunction with physical chemical methods and/or Fourier methods of analysis, they constitute powerful tools for determining sizes, shapes and modes of aggregation of biopolymers with molecular weights greater than 50, 000. However, the application of the e.m. to the determination of very fine structure approaching the limit of instrumental resolving power in biological systems has not been productive, due to various difficulties such as the destructive effects of dehydration, damage to the specimen by the electron beam, and lack of adequate and specific contrast. One of the most satisfactory methods for contrasting individual macromolecules involves the deposition of heavy metal vapor upon the specimen. We have investigated this process, and present here what we believe to be the more important considerations for optimizing it. Results of the application of these methods to several biological systems including muscle proteins, fibrinogen, ribosomes and chromatin will be discussed.

COMPARATIVE ACTION OF VARIOUS OESTROGENIC COMPOUNDS ON MOUSE VAGINAL SIALIC ACIDS (II)

1969 ◽  
Vol 62 (4) ◽  
pp. 663-670 ◽  
Author(s):  
Lars Carlborg
Keyword(s):  
Sialic Acid ◽  
Response Curve ◽  
Sialic Acids ◽  
Clear Cut ◽  
Suitable Parameter ◽  
Sufficient Degree ◽  
Comparative Action ◽  
Relative Potencies ◽  
Good Agreement

ABSTRACT Oestrogens administered in lower doses than necessary to induce full cornification of the mouse vagina induce mucification. It was shown previously that the degree of mucification could be estimated by quantitative determination of sialic acids. A suitable parameter for oestrogen assay was the measurement of vaginal sialic acid concentration which exhibited a clear cut dose response curve. Eleven assays of various oestrogens were performed with this method. Their estimated relative potencies were in good agreement with other routine oestrogen assays. A statistically sufficient degree of precision was found. The sensitivity was of the same order, or slightly higher, than the Allen-Doisy test.

Preparation of graft copolymers by the reaction of polymeric acyl chlorides with monohydroxy-terminated polymers: An introductory study

1988 ◽  
Vol 53 (8) ◽  
pp. 1735-1744 ◽  
Author(s):  
Jitka Horská ◽  
Jaroslav Stejskal ◽  
Pavel Kratochvíl ◽  
Aubrey D. Jenkins ◽  
Eugenia Tsartolia ◽  
...  
Keyword(s):  
Light Scattering ◽  
Chemical Composition ◽  
Statistical Model ◽  
Graft Copolymers ◽  
Coupling Reaction ◽  
Molecular Characteristics ◽  
Gel Formation ◽  
Acyl Chlorides ◽  
Molecular Weights

An attempt was made to prepare well-defined graft copolymers by the coupling reaction between acyl chloride groups located along the backbone chain and monohydroxy-terminated grafts prepared separately. The molecular weights and the parameters of heterogeneity in chemical composition of the products were determined by light scattering and osmometry. The determination of molecular characteristics revealed that the degree of grafting was low. The results therefore could not be confronted with a statistical model at this stage. The problems encountered in the synthesis, e.g., gel formation, and the data relating to the soluble products are discussed.

An Automated Method for the Determination of Serum Calcium with Glyoxal Bis (2-Hydroxyanil)

1967 ◽  
Vol 13 (6) ◽  
pp. 515-520 ◽  
Author(s):  
Genevieve Farese ◽  
Janice L Schmidt ◽  
Milton Mager
Keyword(s):  
Serum Calcium ◽  
Automated Analysis ◽  
Automated Method ◽  
Good Agreement

Abstract A completely automated analysis is described for the determination of serum calcium with glyoxal bis (2-hydroxyanil) solution (GBHA). The method is simple and precise, and the data obtained are in good agreement with results obtained by the manual GBHA procedure.

Numerical evaluation of hydrodynamic characteristics of planing hulls by using a hybrid method

2021 ◽  
pp. 147509022199024
Author(s):  
Emre Kahramanoglu ◽  
Silvia Pennino ◽  
Huseyin Yilmaz
Keyword(s):  
Experimental Data ◽  
Hybrid Method ◽  
Design Stage ◽  
Hydrodynamic Characteristics ◽  
Calm Water ◽  
Preliminary Design Stage ◽  
Reduction Function ◽  
Hull Forms ◽  
Good Agreement

The hydrodynamic characteristics of the planing hulls in particular at the planing regime are completely different from the conventional hull forms and the determination of these characteristics is more complicated. In the present study, calm water hydrodynamic characteristics of planing hulls are investigated using a hybrid method. The hybrid method combines the dynamic trim and sinkage from the Zarnick approach with the Savitsky method in order to calculate the total resistance of the planing hull. Since the obtained dynamic trim and sinkage values by using the original Zarnick approach are not in good agreement with experimental data, an improvement is applied to the hybrid method using a reduction function proposed by Garme. The numerical results obtained by the hybrid and improved hybrid method are compared with each other and available experimental data. The results indicate that the improved hybrid method gives better results compared to the hybrid method, especially for the dynamic trim and resistance. Although the results have some discrepancies with experimental data in terms of resistance, trim and sinkage, the improved hybrid method becomes appealing particularly for the preliminary design stage of the planing hulls.

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