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

Abstract

The quaternary structural transition between the R and T states of human hemoglobin was investigated using the transient grating technique. The results presented herein reveal that the quaternary structural change accompanied by the R-T transition occurs within a few microseconds.

Photocycle of Photoactive Yellow Protein in Cell-Mimetic Environments: Molecular Volume Changes and Kinetics

“…The setup for TG experiments was similar to that reported in our previous work. − Briefly, a 460 nm pulsed laser beam from an optical parametric oscillator (LT-2144-PC; LOTIS TII, Belarus) pumped by an Nd:YAG laser (NL301G; EKSPLA, Lithuania) was split into two equivalent beams. The two excitation beams and the 830 nm continuous-wave laser beam intersected each other on the sample.…”

“…Experimental setup for TA measurement was similar to that reported in our previous work. − Briefly, the probe white light (continuous wave) was got through the sample position in an angle as acute as possible against the 460 nm pump laser beam to maximize the overlap between pump and probe beams. The TA signal was detected by the combination of a spectrometer (ACTON 2300i; Princeton Instruments, U.S.A.) and an ICCD (iStar; Andor Technology, U.K.) or a PMT.…”

“…In this study, ethylene glycol (EG), poly­(ethylene glycol) (PEG) 400, PEG 1000, PEG 8000, Ficoll PM 70, Dextran 40, and bovine serum albumin (BSA) were used as molecular crowding agents to generate a cell-mimetic environment. , Although EG and PEG with a low molecular weight (MW) are good crowding agents for mimicking the intracellular environment, they can also induce dehydration, owing to the release of protein-binding water molecules. In contrast, PEG with a high MW, Ficoll PM 70, Dextran 40, and BSA have only a pure excluded volume effect for proteins. ,− The TG technique was utilized to probe the global structural change of a protein on the basis of the change in the diffusion coefficient ( D ), which is directly related to the size and shape of a chemical species. ,− The TA technique is used to monitor the local structural change around the chromophore. The results obtained in this study clearly demonstrate that the molecular volume change accompanied by the photocycle of PYP in molecularly crowded environments is significantly influenced by the excluded volume effect, whereas the kinetics of the photocycle of PYP is greatly affected by the dehydration of a protein.…”

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).…”