Protein Dynamics Measurements by 3D HNCO Based NMR Experiments

Protein dynamics can be characterized by relaxation parameters obtained from traditional 2D HSQC based NMR experiments. This approach is hampered when applied to proteins with severe spectral overlap. In the present work, several novel 3D TROSY-HNCO and 3D HSQC-HNCO based NMR experiments were applied for measuring15NT1,T2and1H-15N NOE with improved spectral dispersion by introducing a third13C dimension. The number of phase cycling steps in these 3D pulse sequences was restricted to two in order to minimize the time required to perform the dynamics measurements. For a uniformly 100%15N, 100%13C, and 70%2H-labelled trichosanthin sample (~27 kDa, 1.0 mM) at 30°C, the sensitivity of 3D TROSY-HNCO based experiment was, on the average, enhanced by 72% compared to that of 3D HSQC-HNCO based experiments. However, the 3D HSQC-HNCO based experiments should be more effective for non-deuterated proteins with smaller molecular weights and seriously overlapped 2D HSQC spectra. Results from the 3D TROSY-HNCO and 3D HSQC-HNCO based experiments were in good agreement with those obtained from traditional 2D HSQC based experiments.

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The Reduction of Bias Error in Transfer Function Estimates Using FFT-Based Analyzers

Journal of Vibration and Acoustics ◽

10.1115/1.3269148 ◽

1984 ◽

Vol 106 (1) ◽

pp. 29-35 ◽

Cited By ~ 7

Author(s):

P. Cawley

Keyword(s):

Transfer Function ◽

Random Excitation ◽

Analogue Computer ◽

Bias Error ◽

Testing Time ◽

Theoretical Predictions ◽

Set Up ◽

Modal Mass ◽

Time Required ◽

Good Agreement

The susceptibility to bias error of two methods for computing transfer (frequency response) functions from spectra produced by FFT-based analyzers using random excitation has been investigated. Results from tests with an FFT analyzer on a single degree-of-freedom system set up on an analogue computer show good agreement with the theoretical predictions. It has been shown that, around resonance, the bias error in the transfer function estimate H2 (Syy/Sxy*) is considerably less than that in the more commonly used estimate, H1 (Sxy/Sxx). The record length, and hence the testing time, required for a given accuracy is reduced by over 50 percent if the H2 calculation procedure is used. The analysis has also shown that if shaker excitation is used on lightly damped structures with low modal mass, it is important to minimize the mass of the force gage and the moving element of the shaker.

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Partition of tert-dodecyl mercaptan in systems containing styrene, polystyrene, and polybutadiene. Its effect on the macromolecular characteristics of high-impact poly styrene

e-Polymers ◽

10.1515/epoly.2007.7.1.980 ◽

2007 ◽

Vol 7 (1) ◽

Cited By ~ 1

Author(s):

Natalia Casís ◽

Carla Vanesa Luciani ◽

Diana Alejandra Estenoz ◽

Marisa Martinelli ◽

Miriam Strumia ◽

...

Keyword(s):

Total Concentration ◽

Strong Dependence ◽

Monomer Conversion ◽

Theoretical Work ◽

High Impact ◽

Proton Nuclear Magnetic Resonance ◽

Molecular Weights ◽

H Nmr ◽

Dodecyl Mercaptan ◽

Good Agreement

AbstractThis work investigates the distribution between phases of tert-dodecyl mercaptan (t-DDM) in systems containing styrene (St), polystyrene (PS), and polybutadiene (PB) with the aim of studying its effect on the molecular macrostructure of High-Impact Polystyrene (HIPS) produced via the bulk process. Experimental work involved the study of several St/PS/PB/t-DDM blends, and of 2 polymerizations of St in presence of PB (with and without t-DDM). Blends were prepared with increasing PS/St ratios to emulate monomer conversions of 7, 9, 11, 13, and 15%, employing 2 base PSs of different molar masses, and several total concentrations of t-DDM. Measurements by Proton Nuclear Magnetic Resonance (1H NMR) indicate that t-DDM is almost evenly distributed between the phases at room temperature. In addition, for samples taken along the 2 investigated polymerizations, monomer conversion, grafting efficiency, and free PS molecular weights were measured. Theoretical work involved first to model the species partitions through the Flory-Huggins theory [1]; and then, to combine such partition model with a polymerization model extended from that by Casís et al. [2]. Theoretical estimations were in good agreement with experimental determinations. Simulations suggest that t-DDM partition coefficients exhibit a weak dependence with temperature, but a strong dependence with its total concentration. Also, the combined partition/polymerization model indicates that the free PS contained in the occlusion regions exhibits lower molecular weights than that in the continuous matrix.

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Kinetik und Mechanismus der enzymatischen Dextransynthese und Wirkung der Akzeptoren auf diese Reaktion

Zeitschrift für Naturforschung B ◽

10.1515/znb-1968-0606 ◽

1968 ◽

Vol 23 (6) ◽

pp. 788-797 ◽

Cited By ~ 14

Author(s):

K. H. Ebert ◽

G. Schenk

Keyword(s):

Reaction Rate ◽

Polymer Chains ◽

Low Molecular Weight ◽

Michaelis Constant ◽

Acceptor Reaction ◽

General Applicability ◽

Polymer Molecules ◽

Molecular Weights ◽

Reaction Constants ◽

Good Agreement

According to the proposed mechanism, the enzymic formation of dextran from sucrose consists of two reaction steps: the propagation reaction forming polymer molecules by an insertion type growth, and the acceptor reaction leading to the termination of the polymer chains. This mechanism is of a more general applicability; it explains hydrolysis, transfer and poly reactions.A complete kinetic analysis is given for the dextran formation and values for the reaction constants Vm, Km and Ka (the Michaelis constant of the acceptor reaction) have been evaluated. Very good agreement between the rate data calculated from the mechanism and the experimental data has been obtained.From experiments with a series of radioactively labelled acceptors it was established that the acceptor reaction, in fact, proceeds as proposed by the mechanism. Further, it was found that strong acceptors, leading to the formation of low molecular weight dextrans, do not inhibit the reaction rate, and that weak acceptors, which inhibit the reaction rate, have only a small effect on the molecular weights. This correlation has also been demonstrated in terms of the proposed reaction mechanism.

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Evaluation of polydispersity index Mw/Mn by quasielastic light scattering

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19871235 ◽

1987 ◽

Vol 52 (5) ◽

pp. 1235-1245 ◽

Cited By ~ 2

Author(s):

Petr Štěpánek ◽

Zdeněk Tuzar ◽

Čestmír Koňák

Keyword(s):

Molecular Weight ◽

Light Scattering ◽

Decay Time ◽

Sampling Time ◽

Polydispersity Index ◽

New Method ◽

Molecular Weights ◽

Quasielastic Light Scattering ◽

Good Agreement

The response of quasielastic light scattering to the polydispersity of scattering objects has been investigated. A new method of the polydispersity index determination has been suggested, suitable for the range 1.02 ⪬ Mw/Mn ⪬ 2.0 and consisting in the measurement of the dependence of the apparent decay time on the correlator sampling time. The polydispersity index can be determined by comparing these dependences with the theoretical ones obtained using correlation curves simulated for various values of the polydispersity index, assuming lognormal and Schulz-Zimm distributions of molecular weights. The test measurements on polystyrene standards having molecular weights in the range 9 103 – 20.6 106 give polydispersity index values Mw/Mn that are in a good agreement with those given by the manufacturer. The polydispersity index for polystyrene having the molecular weight Mw = 20.6 106 thus determined was Mw/Mn = 1.35.

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

Canadian Journal of Chemistry ◽

10.1139/v78-254 ◽

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.

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Drift and Trapping in Biased Diffusion on Disordered Lattices

International Journal of Modern Physics C ◽

10.1142/s0129183198000273 ◽

1998 ◽

Vol 09 (02) ◽

pp. 349-355 ◽

Cited By ~ 24

Author(s):

Deepak Dhar ◽

Dietrich Stauffer

Keyword(s):

Average Velocity ◽

Three Dimensional ◽

Bias Field ◽

Critical Value ◽

Intermediate Time ◽

Biased Diffusion ◽

Time Required ◽

Moderate Bias ◽

Percolation Network ◽

Good Agreement

We re-examine the theory of transition from drift to no-drift in biased diffusion on percolation networks. We argue that for the bias field B equal to the critical value Bc, the average velocity at large times t decreases to zero as 1/ log (t). For B<Bc, the time required to reach the steady-state velocity diverges as exp ( const /|Bc-B|). We propose an extrapolation form that describes the behavior of average velocity as a function of time at intermediate time scales. This form is found to have a very good agreement with the results of extensive Monte Carlo simulations on a three-dimensional site-percolation network and moderate bias.

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Activities and Ionic Distributions in Cobalt Silicate Melts

Canadian Journal of Chemistry ◽

10.1139/v71-115 ◽

1971 ◽

Vol 49 (5) ◽

pp. 683-690 ◽

Cited By ~ 16

Author(s):

I. B. Smith ◽

C. R. Masson

Keyword(s):

Silica Content ◽

Silicate Melts ◽

Molecular Weights ◽

Polymer Theory ◽

Linear Chains ◽

Experimental Values ◽

The Relationship ◽

Gas Chromatographic Separation ◽

Good Agreement ◽

Binary Silicate

Activities of CoO in CoO–SiO2 melts were measured at 1450–1500 °C by equilibrating the melts, held in Pt–Rh containers, with atmospheres of known oxygen potential. Activities were calculated by the relationship[Formula: see text]where aCo, the activity of cobalt in the container, was determined in separate experiments.The results were compared with theoretical activity–composition curves based on the application of polymer theory to silicate melts. The results were in good agreement with theoretical curves calculated on the assumption of linear chains. In contrast, for all other binary silicate melts so far investigated the results are best represented in terms of theory in which all chain configurations are allowed. Ionic distributions and number average and weight average molecular weights were calculated as functions of the silica content from the experimental data. The calculated proportions of monomeric ion, SiO44−, dimer Si2O76−, and trimer Si3O108− were in reasonable agreement with experimental values based on trimethylsilylation and gas-chromatographic separation of the ionic constituents in quenched melts.

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Phase Behaviour of the System Propene/Polypropene at High Pressure

Journal of Thermodynamics ◽

10.1155/2011/282354 ◽

2011 ◽

Vol 2011 ◽

pp. 1-5

Author(s):

Oliver Ruhl ◽

Gerhard Luft ◽

Patrick Brant ◽

John Richard Shutt

Keyword(s):

Cloud Point ◽

High Pressures ◽

Weight Fraction ◽

Phase Behaviour ◽

Critical Weight ◽

Molecular Weights ◽

Metal Bellows ◽

Similar Density ◽

Increasing Temperature ◽

Good Agreement

The phase behaviour of mixtures of supercritical propene and a number of polypropenes, which have a similar density but significantly different molecular weights and tacticities, was investigated in a broad range of polymer weight fractions and temperatures at high pressures. The cloud-point pressures were measured optically, using a view cell which was equipped with two windows made of synthetic sapphire and a metal bellows to accurately adjust the pressure. The cloud-point pressures were found in the range from 29 to 37 MPa decreasing with increasing polymer weight fraction and increasing with increasing temperature and polymer molecular weight. The critical weight fraction was found below 2 to 6 wt.-%. Whereas the cloud-point pressures of atactic and syndiotactic samples were high and very similar, the isotactic species exhibit distinctly lower values. The results, extrapolated to lower temperatures, show good agreement with the literature data.

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

Rubber Chemistry and Technology ◽

10.5254/1.3542406 ◽

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.

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SAMPLING METHODS FOR ARTHROPOD COLONIZATION STUDIES IN SOYBEAN

The Canadian Entomologist ◽

10.4039/ent110265-3 ◽

1978 ◽

Vol 110 (3) ◽

pp. 265-274 ◽

Cited By ~ 5

Author(s):

Mark A. Mayse ◽

Peter W. Price ◽

Marcos Kogan

Keyword(s):

Direct Observation ◽

East Central ◽

Absolute Method ◽

Row Crop ◽

Soybean Plants ◽

Time Required ◽

Central Illinois ◽

A Site ◽

Short Time ◽

Good Agreement

AbstractDirect observation (DO) of arthropods on soybean plants was compared with another absolute method, clam trap (CT), and with sweepnet (SW) sampling during a season-long investigation of the colonization by arthropods of two east central Illinois soybean fields. In terms of number of species detected, DO vs. CT showed good agreement between the two fields, while DO vs. SW showed poor between-field agreement. Proportion of similarity (PS) and quotient of similarity (QS) values were higher in a DO-CT comparison than in a DO-SW comparison. Performance similar to that of the other absolute method, consistency of results, ability to use the method throughout the entire season, relatively high numbers of species and individuals detected per unit area sampled, relatively short time required to sample a site, and the capability of yielding a precise record of important interactions among soybean arthropods indicate that direct observation is an effective method for sampling the arthropod community on a row crop such as soybean.

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