scholarly journals Characterization of structural and folding properties of streptokinase by n.m.r. spectroscopy

1993 ◽  
Vol 290 (2) ◽  
pp. 313-319 ◽  
Author(s):  
A J Teuten ◽  
R W Broadhurst ◽  
R A G Smith ◽  
C M Dobson
Keyword(s):  
Protein Structure ◽  
Nuclear Polarization ◽  
Guanidine Hydrochloride ◽  
Two Dimensional ◽  
Polarization Spectroscopy ◽  
Histidine Residues ◽  
Chemically Induced ◽  
Dynamical Nuclear Polarization ◽  
Partially Folded States

The structure and physical properties of the fibrinolytic protein streptokinase have been investigated by 1H-n.m.r. spectroscopy. Well-resolved one- and two-dimensional spectra have been obtained for this molecule of molecular mass 47 kDa. Titration of all nine histidine residues has shown that these display a range of pKa values, between 5.6 and 8.2, revealing a variety of environments for these residues in the protein structure. Although at least eight histidine residues can be reversibly modified by diethylpyrocarbonate, only one is sufficiently exposed to be reactive towards photo-excited dye in chemically induced dynamical nuclear polarization spectroscopy experiments. Unfolding studies have been performed by thermal and chemical means. Evidence is presented here for several distinct unfolding transitions suggesting that the protein consists of at least three domains which have independent stability, and that the protein can exist in a number of partially folded states. For one of these, that formed in 2 M guanidine hydrochloride, it has been shown that the N-terminal region of the molecule is extensively unfolded, while other regions of the protein remain in native-like folded states.

Characterization of compounds in crude oils by gas purge micro-syringe extraction coupled to comprehensive two-dimensional gas chromatography

2014 ◽  
Vol 32 (10) ◽  
pp. 1144
Author(s):  
Ting TONG ◽  
Wanfeng ZHANG ◽  
Donghao LI ◽  
Jinhua ZHAO ◽  
Zhenyang CHANG ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Crude Oils ◽  
Two Dimensional ◽  
Gas Purge

Dynamical Nuclear Polarization

2018 ◽  
Author(s):  
M. M. Glazov
Keyword(s):  
Spin Polarization ◽  
Nuclear Spin ◽  
Nuclear Polarization ◽  
Magnetic Moments ◽  
Nonlinear Effects ◽  
Many Body ◽  
Nuclear Spin Polarization ◽  
Optical Resonances ◽  
Dynamical Nuclear Polarization ◽  
Temperature Concept

The transfer of nonequilibrium spin polarization between the electron and nuclear subsystems is studied in detail. Usually, a thermal orientation of nuclei in magnetic field is negligible due to their small magnetic moments, but if electron spins are optically oriented, efficient nuclear spin polarization can occur. The microscopic approach to the dynamical nuclear polarization effect based on the kinetic equation method, along with a phenomenological but very powerful description of dynamical nuclear polarization in terms of the nuclear spin temperature concept is given. In this way, one can account for the interaction between neighbouring nuclei without solving a complex many-body problem. The hyperfine interaction also induces the feedback of polarized nuclei on the electron spin system giving rise to a number of nonlinear effects: bistability of nuclear spin polarization and anomalous Hanle effect, dragging and locking of optical resonances in quantum dots. Theory is illustrated by experimental data on dynamical nuclear polarization.

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