scholarly journals The effect of guanidinium chloride on the behaviour of human cervical-mucus glycoproteins. Evidence for unfolding regions of ordered structure in 6M-guanidinium chloride

1984 ◽  
Vol 221 (2) ◽  
pp. 499-504 ◽  
Author(s):  
J K Sheehan ◽  
I Carlstedt
Keyword(s):  
Frictional Coefficient ◽  
Correlation Spectroscopy ◽  
Cervical Mucus ◽  
Random Coil ◽  
Radius Of Gyration ◽  
Ordered Structure ◽  
Guanidinium Chloride ◽  
Photon Correlation ◽  
The Individual ◽  
Mucus Glycoproteins

The macromolecular properties of cervical-mucus glycoproteins (mucins) were studied as a function of the concentration of guanidinium chloride with conventional light-scattering, photon-correlation spectroscopy and sedimentation-velocity centrifugation. No evidence for an association of the mucins in 0.2M-NaCl as compared with 6M-guanidinium chloride was found at mucin concentrations below approx. 0.5 mg/ml. However, an increase in the frictional coefficient and in the radius of gyration occurred with increasing concentrations of guanidinium chloride, in particular between 4 M and 6 M, suggesting an expansion of the individual macromolecule. The change in the particle-scattering function is consistent with a transition from a ‘stiff’ random coil in 0.2 M-NaCl into a more flexible one in 6 M-guanidinium chloride. We suggest that the mucins contain regions of ‘ordered’ structure which can undergo a reversible ‘unfolding’ analogous to the behaviour of a conventional globular protein exposed to a denaturing solvent. Such regions might carry sites for specific interactions between mucins and/or be decisive for their conformation and macromolecular properties in physiological solvents.

scholarly journals The macromolecular structure of human cervical-mucus glycoproteins. Studies on fragments obtained after reduction of disulphide bridges and after subsequent trypsin digestion

1983 ◽  
Vol 213 (2) ◽  
pp. 427-435 ◽  
Author(s):  
I Carlstedt ◽  
H Lindgren ◽  
J K Sheehan
Keyword(s):  
Proteinase Inhibitors ◽  
Gradient Centrifugation ◽  
Cervical Mucus ◽  
Trypsin Digestion ◽  
Radius Of Gyration ◽  
Guanidinium Chloride ◽  
Disulphide Bonds ◽  
Tentative Model ◽  
The Relationship ◽  
Mucus Glycoproteins

Human cervical-mucus glycoproteins (mucins) were extracted with 6 M-guanidinium chloride in the presence of proteinase inhibitors and purified by isopycnic density-gradient centrifugation. The whole mucins (Mr approx. 10 × 10(6] were degraded into ‘subunits’ (Mr approx. 2 × 10(6] by reduction of disulphide bonds. Trypsin digestion of the ‘subunits’ produced glycopeptides with Mr approx. 380000, which appear to be rod-like with a length of approx. 105 nm. The relationship between the radius of gyration and the Mr value obtained by light-scattering for whole mucins, ‘subunits’ and ‘domains’ suggest that cervical-mucus glycoproteins are linear flexible macromolecules composed of, on the average, four or five ‘domains’/subunit and four subunits/whole mucin macromolecule. The shape-dependent particle scattering function for the whole mucins and the ‘subunits’ are in accordance with that of a linear flexible chain. No evidence for a branched or a star-like structure was found. A tentative model for cervical mucins is proposed.

scholarly journals Size heterogeneity of human cervical mucus glycoproteins. Studies performed with rate-zonal centrifugation and laser light-scattering

1987 ◽  
Vol 245 (3) ◽  
pp. 757-762 ◽  
Author(s):  
J K Sheehan ◽  
I Carlstedt
Keyword(s):  
Light Scattering ◽  
Laser Light ◽  
Laser Light Scattering ◽  
Correlation Spectroscopy ◽  
Radius Of Gyration ◽  
Intensity Measurements ◽  
The Individual ◽  
Size Heterogeneity ◽  
Mucus Glycoproteins ◽  
Good Agreement

Mucus glycoproteins (mucins) from cervical pregnancy mucus were fractionated by using rate-zonal centrifugation in a gradient of guanidinium chloride. The distribution of the macromolecules, as assessed by using sialic acid determination, suggested the presence of three populations of different size. Individual fractions were subjected to laser light-scattering performed as total-intensity measurements as well as photon correlation spectroscopy. The results showed that points of inflexion were present in the distribution of both Mr and DT (translational diffusion coefficient) and that the three populations have Mr values of approx. 24 × 10(6), 16 × 10(6) and 6 × 10(6) respectively. The weight-average Mr for the whole distribution, as calculated from the values obtained for the individual fractions, was 13.6 × 10(6), which is in good agreement with that found for the unfractionated material (11.1 × 10(6]. Plots of log RG (radius of gyration) and log (1/DT) versus log Mr are in keeping with the macromolecules being linear flexible chains.

scholarly journals Hydrodynamic properties of human cervical-mucus glycoproteins in 6m-guanidinium chloride

1984 ◽  
Vol 217 (1) ◽  
pp. 93-101 ◽  
Author(s):  
J K Sheehan ◽  
I Carlstedt
Keyword(s):  
Sedimentation Coefficient ◽  
Large Degree ◽  
Correlation Spectroscopy ◽  
Radius Of Gyration ◽  
Random Coils ◽  
Intensity Measurements ◽  
Hydrodynamic Behaviour ◽  
Stokes Radius ◽  
The Individual ◽  
The Relationship

Cervical mucins and fragments thereof were studied by sedimentation-velocity, rotatory viscometry and laser light-scattering performed as photon-correlation spectroscopy as well as low-angle total-intensity measurements. The Mr of the whole mucins is 10 × 10(6)-15 × 10(6), whereas fragments obtained after reduction of disulphide bonds (‘subunits’) have Mr 2.1 × 10(6)-2.9 × 10(6), depending on the method used. Subsequent trypsin digestion of subunits afforded glycopeptides with Mr approx. 0.4 × 10(6). The high frictional ratio for the whole mucins is interpreted as a large degree of expansion. The Stokes radius calculated from the diffusion coefficient is approx. 110nm for the whole mucins, which is in agreement with that estimated from the radius of gyration (130nm) by using the concept of the equivalent hydrodynamic sphere. The ratio of the concentration-dependence parameter for the reciprocal sedimentation coefficient (Ks) to the intrinsic viscosity ([eta]) for the whole mucins is 1.42, suggesting that the individual macromolecule occupies a spheroidal domain in solution. The relationship between [eta] and Mr for whole mucins, subunits and T-domains suggests that they are linear flexible macromolecules behaving as somewhat ‘stiff’ random coils. This conclusion is supported by the relationships between the sedimentation coefficients, the diffusion coefficients and the Mr. The hydrodynamic behaviour of the mucins is thus close to that expected for coiling macromolecules entrapping a lot of solvent, which is consistent with the postulated polymeric structure.

Production of Sols from Aggregated Titania Precipitates

1992 ◽  
Vol 271 ◽  
Author(s):  
John. R Bartlett ◽  
James L. Woolfrey
Keyword(s):  
Hydrodynamic Radius ◽  
Dlvo Theory ◽  
Correlation Spectroscopy ◽  
Radius Of Gyration ◽  
Chemical Methods ◽  
Photon Correlation ◽  
Solids Loading ◽  
Solids Concentration ◽  
Colloidal Species ◽  
Hydrolysis Of

ABSTRACTTitania and titania/zirconia sols, with solids loadings exceeding 1000 g dm3, have been prepared on a 10 kg scale by chemical methods involving the hydrolysis of an appropriate mixture of alkoxides, followed by peptisation with dilute nitric acid. The rate of peptisation of the hydrolysates was determined by static light-scattering and photon-correlation spectroscopy, enabling the hydrodynamic radius, the radius of gyration and the fractal dimension of colloidal species to be monitored as a function of peptisation time.The peptisation kinetics were influenced by a range of factors including the initial solids loading, the acid concentration, the reaction temperature and the age of the alkoxide hydrolysate. Hydrolysate peptisation is first order with respect to concentration of acid and exhibited a non-integer reaction rate order (complex mechanism) with respect to solids concentration. Sols produced from freshly-precipitated hydrolysate peptised at a faster rate than aged precipitates but slowly re-aggregated after peptising, yielding “equilibrium” aggregate sizes often exceeding 100 nm. This effect was not observed in sols produced from aged hydrolysate. These differences are interpreted using DLVO theory.

scholarly journals Conformational Ensembles by NMR and MD Simulations in Model Heptapeptides with Select Tri-Peptide Motifs

2021 ◽  
Vol 22 (3) ◽  
pp. 1364
Author(s):  
V. V. Krishnan ◽  
Timothy Bentley ◽  
Alina Xiong ◽  
Kalyani Maitra
Keyword(s):  
Principal Component ◽  
Md Simulations ◽  
Conformational Space ◽  
Random Coil ◽  
Radius Of Gyration ◽  
Small Peptides ◽  
Conformational Ensembles ◽  
Solution State ◽  
Peptide Motifs ◽  
Explicit Solvent

Both nuclear magnetic resonance (NMR) and molecular dynamics (MD) simulations are routinely used in understanding the conformational space sampled by peptides in the solution state. To investigate the role of single-residue change in the ensemble of conformations sampled by a set of heptapeptides, AEVXEVG with X = L, F, A, or G, comprehensive NMR, and MD simulations were performed. The rationale for selecting the particular model peptides is based on the high variability in the occurrence of tri-peptide E*L between the transmembrane β-barrel (TMB) than in globular proteins. The ensemble of conformations sampled by E*L was compared between the three sets of ensembles derived from NMR spectroscopy, MD simulations with explicit solvent, and the random coil conformations. In addition to the estimation of global determinants such as the radius of gyration of a large sample of structures, the ensembles were analyzed using principal component analysis (PCA). In general, the results suggest that the -EVL- peptide indeed adopts a conformational preference that is distinctly different not only from a random distribution but also from other peptides studied here. The relatively straightforward approach presented herein could help understand the conformational preferences of small peptides in the solution state.

scholarly journals From Femtoseconds to Hours–Measuring Dynamics over 18 Orders of Magnitude with Coherent X-rays

2021 ◽  
Vol 11 (13) ◽  
pp. 6179
Author(s):  
Felix Lehmkühler ◽  
Wojciech Roseker ◽  
Gerhard Grübel
Keyword(s):  
Time Scales ◽  
Free Electron Laser ◽  
Photon Correlation Spectroscopy ◽  
Signal To Noise Ratio ◽  
Coherent Scattering ◽  
Correlation Spectroscopy ◽  
X Rays ◽  
Photon Correlation ◽  
X Ray ◽  
Scattering Technique

X-ray photon correlation spectroscopy (XPCS) enables the study of sample dynamics between micrometer and atomic length scales. As a coherent scattering technique, it benefits from the increased brilliance of the next-generation synchrotron radiation and Free-Electron Laser (FEL) sources. In this article, we will introduce the XPCS concepts and review the latest developments of XPCS with special attention on the extension of accessible time scales to sub-μs and the application of XPCS at FELs. Furthermore, we will discuss future opportunities of XPCS and the related technique X-ray speckle visibility spectroscopy (XSVS) at new X-ray sources. Due to its particular signal-to-noise ratio, the time scales accessible by XPCS scale with the square of the coherent flux, allowing to dramatically extend its applications. This will soon enable studies over more than 18 orders of magnitude in time by XPCS and XSVS.

Sign in / Sign up

Export Citation Format

Share Document