Conformation Transition Kinetics of Silk Fibroin in Aqueous Solution Explored Using Circular Dichroism Spectroscopy

Vibrational circular dichoism spectra recorded for (2S,3S)-1-13C-1,2,3-d3-cyclopropane and for mixtures of it and the three related stereoisomers prepared through gas-phase thermal stereomutation reactions at 407°C lead to the rate constant for racemization: kα = (4k1 + 4k12) = (3.12 ± 0.04) x 10-5 s-1. This and the rate constant measured for geometrical equilibration between the two chiral and the two achiral stereoisomers of 1-13C-1,2,3-d3-cyclopropane, ki = (8k1 + 4k12) = (4.63 ± 0.20) x 10-5 s-1, give two equations in two unknowns, and allow one to solve for one-center (k1) and two-center (k12) epimerization rate constants for cyclopropane stereomutations. They are nearly equal, a clear indication of closely competitive reaction pathways.Key words: cyclopropane stereomutations, thermal epimerizations, chirality through deuterium and carbon-13 labeling, vibrational circular dichroism.

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Kinetics of the self-aggregation and film formation of poly-L-proline at high temperatures explored by circular dichroism spectroscopy

Biopolymers ◽

10.1002/bip.21361 ◽

2009 ◽

Vol 93 (5) ◽

pp. 451-457 ◽

Cited By ~ 16

Author(s):

Lonna Tooke ◽

Laura Duitch ◽

Thomas J. Measey ◽

Reinhard Schweitzer-Stenner

Keyword(s):

Circular Dichroism ◽

High Temperatures ◽

Film Formation ◽

Circular Dichroism Spectroscopy ◽

The Self ◽

Kinetics Of ◽

Circular Dichroïsm ◽

Self Aggregation

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Physicochemical Characterisation of KEIF—The Intrinsically Disordered N-Terminal Region of Magnesium Transporter A

Biomolecules ◽

10.3390/biom10040623 ◽

2020 ◽

Vol 10 (4) ◽

pp. 623

Author(s):

Stéphanie Jephthah ◽

Linda K. Månsson ◽

Domagoj Belić ◽

Jens Preben Morth ◽

Marie Skepö

Keyword(s):

Aqueous Solution ◽

Circular Dichroism ◽

Driving Forces ◽

Circular Dichroism Spectroscopy ◽

Terminal Region ◽

Single Chain ◽

Intrinsically Disordered ◽

Magnesium Transporter ◽

Dynamics Simulations ◽

Circular Dichroïsm

Magnesium transporter A (MgtA) is an active transporter responsible for importing magnesium ions into the cytoplasm of prokaryotic cells. This study focuses on the peptide corresponding to the intrinsically disordered N-terminal region of MgtA, referred to as KEIF. Primary-structure and bioinformatic analyses were performed, followed by studies of the undisturbed single chain using a combination of techniques including small-angle X-ray scattering, circular dichroism spectroscopy, and atomistic molecular-dynamics simulations. Moreover, interactions with large unilamellar vesicles were investigated by using dynamic light scattering, laser Doppler velocimetry, cryogenic transmission electron microscopy, and circular dichroism spectroscopy. KEIF was confirmed to be intrinsically disordered in aqueous solution, although extended and containing little β-structure and possibly PPII structure. An increase of helical content was observed in organic solvent, and a similar effect was also seen in aqueous solution containing anionic vesicles. Interactions of cationic KEIF with anionic vesicles led to the hypothesis that KEIF adsorbs to the vesicle surface through electrostatic and entropic driving forces. Considering this, there is a possibility that the biological role of KEIF is to anchor MgtA in the cell membrane, although further investigation is needed to confirm this hypothesis.

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