Protein Conformational Dynamics of Homodimeric Hemoglobin Revealed by Combined Time‐Resolved Spectroscopic Probes

Protein Structural Dynamics of Wild-Type and Mutant Homodimeric Hemoglobin Studied by Time-Resolved X-Ray Solution Scattering

“…In a study of WT HbI using transient grating (TG) spectroscopy [ 36 ], which is a time-resolved experiment measuring refractive index changes of the sample that can detect the diffusion coefficients of the intermediates and reactant, we explained the TG results by adopting a sequential kinetic model. The kinetic parameters determined by the fitting of TG signals of WT HbI are three reaction rates, two diffusion coefficients corresponding to HbI and CO, and a thermal diffusion coefficient.…”

“…However, the allosteric structural transition of Hb is still elusive because of the complex kinetics arising from its heteromeric tetramer structure. In this respect, homodimeric hemoglobin (HbI) from Scapharca inaequivalvis has served as an excellent model system for investigating the allosteric structural transition between a ligated R state with high ligand affinity and a deoxygenated T state with low ligand affinity [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ] due to its simpler dimeric structure. In the HbI, the E and F helices of monomers are located at the interface of homodimer [ 11 , 12 , 39 ], which is often referred to as EF dimer.…”

Regulation of Protein Structural Changes by Incorporation of a Small-Molecule Linker

“…TA measurement was performed by following previously reported procedures [26,27,28,29]. A pump beam (460 nm) was produced by an optical parametric oscillator (LT-2214-PC, LOTIS, Minsk, Belarus) pumped by a third harmonics (355 nm) of an Nd:YAG laser (NL 301G, EKSPLA, Vilnius, Lithuania).…”

The time scale of the quaternary structural changes in hemoglobin revealed using the transient grating technique

“…[29][30][31][32][33][34][35][36][37][38][39][40] Before using the TG technique, for comparison with previous studies, we first measured the TA spectra of HbCO in 100 mM sodium phosphate buffer (pH 7.0) and observed four relaxation times of 1.2 ms, 48 ms, 310 ms, and 6.0 ms (Fig. One of the key questions is which kinetics within this broad time window is primarily responsible for the quaternary structural change associated with the R-T transition.…”

“…[29][30][31][32][33][34][35][36][37][38][39][40] Theoretically, the species grating (dn spe ) arises from the change in the absorption spectrum (population grating, dn p ) and the change in the molecular volume (volume grating, dn v ), as follows: dn spe = dn p + dn v . It is known that the TG signal is very sensitive to the volume change induced by the conformational change of a protein.…”