scholarly journals Kinetics of the urea-induced dissociation of human plasma α2-macroglobulin as measured by small-angle neutron scattering

1991 ◽  
Vol 278 (2) ◽  
pp. 325-328 ◽  
Author(s):  
B Sjöberg ◽  
S Pap ◽  
S E Järnberg ◽  
K Mortensen
Keyword(s):  
Neutron Scattering ◽  
Human Plasma ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Binding Activity ◽  
Radius Of Gyration ◽  
Covalent Interaction ◽  
Α2 Macroglobulin ◽  
Relative Change ◽  
Kinetics Of

The kinetics of the urea-induced dissociation of human plasma alpha 2-macroglobulin into two half-molecular fragments was investigated at 21.0 degrees C by using small-angle neutron scattering. The relative change in molecular mass that occurs upon dissociation was monitored by recording the forward scattering of neutrons as a function of time. All these kinetic data can be explained by a reaction that is first-order with respect to the concentration of undissociated alpha 2-macroglobulin. The velocity constant is a function of urea concentration and it varies within wide limits. For instance, the half-life of the reaction at the lowest concentration of [2H]urea studied (2.70 M) is 328 h, whereas the same value at the highest concentration of [2H]urea (6.24 M) is only 8 min. Measurements were made both with [1H]urea in 1H2O and with [2H]urea in 99% 2H2O, and it was found that there is a pronounced kinetic isotope effect, i.e. the dissociation is 4 times faster in the 1H-containing medium as compared with the 2H-containing medium at the same molar concentration of urea. From the angular dependence of the neutron scattering it can be concluded that the dissociation is associated with a drastic change in structure. This is directly shown by the radius of gyration, which increases from about 7.4 nm immediately after the addition of urea up to about 9.4 nm when the protein is fully dissociated. A structural analysis shows that the scattering curve of urea-dissociated alpha 2-macroglobulin can best be explained by that of a Gaussian coil with a radius of gyration equal to 9.44 nm. These data indicate that the so-called non-covalent interaction of alpha 2-macroglobulin probably is more complicated than just a pure hydrophobic interaction. Finally, it is also shown that the dissociation is accompanied by a loss in trypsin-binding activity, which is directly related to the fraction of dissociated protein.

scholarly journals Nanoscale disintegration kinetics of mesoglobules in aqueous poly(N-isopropylacrylamide) solutions revealed by small-angle neutron scattering and pressure jumps

Nanoscale ◽  
2021 ◽  
Author(s):  
Bart-Jan Niebuur ◽  
Leonardo Chiappisi ◽  
Florian A. Jung ◽  
Xiaohan Zhang ◽  
Alfons Schulte ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Polymeric Nanoparticles ◽  
Target Pressure ◽  
Kinetics Of ◽  
Rapid Pressure

Two types of disintegration processes are revealed for polymeric nanoparticles using rapid pressure jumps and kinetic small-angle neutron scattering, namely chain release or swelling of the nanoparticle, depending on the target pressure.

scholarly journals Structural aspects of human lactoferrin in the iron-binding process studied by molecular dynamics and small-angle neutron scattering

2018 ◽  
Vol 41 (9) ◽  
Author(s):  
Lilia Anghel ◽  
Aurel Radulescu ◽  
Raul Victor Erhan
Keyword(s):  
Molecular Dynamics ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
The Body ◽  
Human Lactoferrin ◽  
Radius Of Gyration ◽  
Scattering Method ◽  
Iron Binding ◽  
Binding Process

Abstract. Lactoferrin is a non-heme protein known for its ability to bind tightly Fe(III) ions in various physiological environments. Due to this feature lactoferrin plays an important role in the processes of iron regulation at the cellular level preventing the body from damages produced by high levels of free iron ions. The X-ray crystal structure of human lactoferrin shows that the iron-binding process leads to conformational changes within the protein structure. The present study was addressed to conformation stability of human lactoferrin in solution. Using molecular dynamics simulations, it was shown that Arg121 is the key amino acid in the stabilization of the Fe(III) ion in the N-lobe of human lactoferrin. The small-angle neutron scattering method allowed us to detect the structural differences between the open and closed conformation of human lactoferrin in solution. Our results indicate that the radius of gyration of apolactoferrin appears to be smaller than that of the hololactoferrin, $R_{g}=24.16(\pm 0.707)$ R g = 24 . 16 ( ± 0 . 707 ) Å and $R_{g}= 26.20(\pm 1.191)$ R g = 26 . 20 ( ± 1 . 191 ) Å, respectively. The low-resolution three-dimensional models computed for both forms of human lactoferrin in solution also show visible differences, both having a more compact conformation compared to the high-resolution structure. Graphical abstract

scholarly journals Open-Bundle Structure as the Unfolding Intermediate of Cytochrome c’ Revealed by Small Angle Neutron Scattering

2021 ◽  
Author(s):  
Takahide Yamaguchi ◽  
Kouhei Akao ◽  
Alexandros Koutsioubas ◽  
Henrich Frielinghaus ◽  
Takamitsu Kohzuma
Keyword(s):  
Cytochrome C ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Alpha Helix ◽  
Random Coil ◽  
Radius Of Gyration ◽  
Alpha Helices ◽  
Cyt C ◽  
Bundle Structure

The open-bundle structure of cytochrome c’ as an unfolding intermediate was determined by small-angle neutron scattering experiment (SANS). The four-α-helix bundle structure of Cyt c’ at neutral pH was transited to an open-bundle structure (at pD ~13), which is a joint-clubs consisting of four clubs (α-helices) connected by short loops. The compactly folded structure of Cyt c’ (radius of gyration, Rg = 18 Å for the Cyt c’ dimer) at neutral or mildly alkaline pD transitioned to a remarkably larger “open-bundle” structure at pD ~13 (Rg = 25 Å for the Cyt c’ monomer). Cyt c’ adopts an unstructured random coil structure at pD = 1.7 (Rg = 25 Å for the Cyt c’ monomer). Numerical partial scattering function analysis (joint-clubs) and ab initio modelling gave structures similar to the “open-bundle”, which retains the α-helices but loses the bundle structure.

scholarly journals Small-angle neutron scattering studies suggest the mechanism of BinAB protein internalization

IUCrJ ◽  
2020 ◽  
Vol 7 (2) ◽  
pp. 166-172
Author(s):  
Mahima Sharma ◽  
Vinod K. Aswal ◽  
Vinay Kumar ◽  
R. Chidambaram
Keyword(s):  
Neutron Scattering ◽  
Conformational Changes ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Solution Structure ◽  
Expression System ◽  
Radius Of Gyration ◽  
Macromolecular Systems ◽  
Approaches To Study ◽  
Protein Components

Small-angle neutron scattering (SANS) is one of the most widely used neutron-based approaches to study the solution structure of biological macromolecular systems. The selective deuterium labelling of different protein components of a complex provides a means to probe conformational changes in multiprotein complexes. The Lysinibacillus sphaericus mosquito-larvicidal BinAB proteins exert toxicity through interaction with the receptor Cqm1 protein; however, the nature of the complex is not known. Rationally engineered deuterated BinB (dBinB) protein from the L. sphaericus ISPC-8 species was synthesized using an Escherichia coli-based protein-expression system in M9 medium in D2O for `contrast-matched' SANS experiments. SANS data were independently analysed by ab initio indirect Fourier transform-based modelling and using crystal structures. These studies confirm the dimeric status of Cqm1 in 100% D2O with a longest intramolecular vector (D max) of ∼94 Å and a radius of gyration (R g) of ∼31 Å. Notably, BinB binds to Cqm1, forming a heterodimeric complex (D max of ∼129 Å and R g of ∼40 Å) and alters its oligomeric status from a dimer to a monomer, as confirmed by matched-out Cqm1–dBinB (D max of ∼70 Å and R g of ∼22 Å). The present study thus provides the first insight into the events involved in the internalization of larvicidal proteins, likely by raft-dependent endocytosis.

Determination of Deuterium Incorporation into RNA and Protein Components of the Escherichia Coli Ribosome at Biosynthetic Deuteration by Small-Angle Neutron Scattering

1997 ◽  
Vol 30 (1) ◽  
pp. 59-64
Author(s):  
L. Fan ◽  
E. I. Zgurskaya ◽  
I. Shcherbakova ◽  
I. N. Serdyuk
Keyword(s):  
Escherichia Coli ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Standard Procedure ◽  
Radius Of Gyration ◽  
Deuterium Incorporation ◽  
Simple Method ◽  
Protein Components

A simple method for the determination of deuterium incorporation into nonexchangeable (C-bonded) positions of RNA and protein components of the Escherichia coli ribosome at biosynthetic deuteration has been proposed using small-angle neutron scattering. The theory of the method is based on the joint use of two measurements: one of them is the dependence of neutron scattering intensity at zero angle on the contrast; the second is the dependence of the radius of gyration on the contrast. The main advantage of the method over the standard procedure is that it requires neither separation of the ribosome into RNA and protein components nor a subsequent time-consuming analysis of the hydrolysis products by nuclear magnetic resonance or mass spectrometry.

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