Pressure-jump relaxation kinetics of magnesium(II), manganese(II), nickel(II), cobalt(II), copper(II), and zinc(II) m-benzenedisulfonates in anhydrous methanol at 25.deg.

1970 ◽  
Vol 9 (5) ◽  
pp. 1009-1014 ◽  
Author(s):  
G. Macri ◽  
Sergio Petrucci
Keyword(s):  
Anhydrous Methanol ◽  
Pressure Jump ◽  
Relaxation Kinetics ◽  
Pressure Jump Relaxation ◽  
Kinetics Of

Pressure-jump Relaxation Kinetics of Unfolding and Refolding Transitions of Staphylococcal Nuclease and Proline Isomerization Mutants

1996 ◽  
Author(s):  
Gedlminas J. A. Vidugiris ◽  
Raj Thomas
Keyword(s):  
Globular Proteins ◽  
Staphylococcal Nuclease ◽  
Site Directed Mutagenesis ◽  
Pressure Jump ◽  
Wild Type ◽  
Relaxation Kinetics ◽  
Signal Activity ◽  
In The Wild ◽  
Pressure Jump Relaxation ◽  
Kinetics Of

We present here the first report of the pressure dependence of pressure-jump relaxation kinetics for protein folding transitions. We have studied the relaxation kinetics for the unfolding/refolding of wild-type Staphylococcal nuclease and have found that the relaxation kinetics observed at high pressure are much slower than those observed by pH or denaturant jumps at atmospheric pressure. This indicates that these processes have large, positive values for the activation volumes, most likely stemming from exclusion of solvent from a transition state that is less well packed than the native state. We examined the pressure-jump relaxation kinetics of three single-site mutations in nuclease that lead to alterations in the interactions between the two domains of the protein and changes in the equilibrium constant for isomerization of the lysine-116 to proline 117 peptide bond away from the cis form that predominates in the wild-type enzyme. At comparable pressures, the relaxation times for these mutants were significantly shorter than those observed for the wild type, indicating lower values of the activation volumes. We propose that these mutations cause a decrease in the cooperativity of the unfolding of the two domains, leading to a decrease in the degree of solvent exclusion at the rate-limiting step. The mechanism by which a particular amino acid sequence determines the fold and stability of globular proteins remains one of the most interesting and important unresolved issues in biophysical chemistry. The approaches to increasing our understanding of this phenomenon typically have involved perturbation of the proteins by chemical means or by temperature extremes. The equilibrium or time-dependent responses to these perturbations are then monitored (using a spectroscopic signal, activity, or some other observable) to extract the energetic or kinetic aspects of the unfolding or refolding transitions. Another means of perturbing the system is to modify the protein itself, either chemically or by site-directed mutagenesis, and to assess the effects of modification on the equilibrium or kinetic folding or refolding profiles. This approach has generated a great deal of information about small globular proteins that denature reversibly.

scholarly journals Kinetics of the Hydrolysis of Zeolite 4A Surface by the Pressure-jump Relaxation Method

1981 ◽  
Vol 54 (6) ◽  
pp. 1885-1886 ◽  
Author(s):  
Tetsuya Ikeda ◽  
Minoru Sasaki ◽  
Raymond D. Astumian ◽  
Tatsuya Yasunaga
Keyword(s):  
Relaxation Method ◽  
Pressure Jump ◽  
Zeolite 4A ◽  
Pressure Jump Relaxation ◽  
Kinetics Of ◽  
Hydrolysis Of

scholarly journals The effects of cosolutes and crowding on the kinetics of protein condensate formation based on liquid–liquid phase separation: a pressure-jump relaxation study

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Hasan Cinar ◽  
Roland Winter
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Liquid Phase Separation ◽  
Pressure Jump ◽  
Transformation Kinetics ◽  
Biologically Relevant ◽  
Pressure Jump Relaxation ◽  
The Stability ◽  
Kinetics Of ◽  
Liquid Liquid Phase Separation

Abstract Biomolecular assembly processes based on liquid–liquid phase separation (LLPS) are ubiquitous in the biological cell. To fully understand the role of LLPS in biological self-assembly, it is necessary to characterize also their kinetics of formation and dissolution. Here, we introduce the pressure-jump relaxation technique in concert with UV/Vis and FTIR spectroscopy as well as light microscopy to characterize the evolution of LLPS formation and dissolution in a time-dependent manner. As a model system undergoing LLPS we used the globular eye-lens protein γD-crystallin. As cosolutes and macromolecular crowding are known to affect the stability and dynamics of biomolecular condensates in cellulo, we extended our kinetic study by addressing also the impact of urea, the deep-sea osmolyte trimethylamine-N-oxide (TMAO) and a crowding agent on the transformation kinetics of the LLPS system. As a prerequisite for the kinetic studies, the phase diagram of γD-crystallin at the different solution conditions also had to be determined. The formation of the droplet phase was found to be a very rapid process and can be switched on and off on the 1–4 s timescale. Theoretical treatment using the Johnson–Mehl–Avrami–Kolmogorov model indicates that the LLPS proceeds via a diffusion-limited nucleation and growth mechanism at subcritical protein concentrations, a scenario which is also expected to prevail within biologically relevant crowded systems. Compared to the marked effect the cosolutes take on the stability of the LLPS region, their effect at biologically relevant concentrations on the phase transformation kinetics is very small, which might be a particular advantage in the cellular context, as a fast switching capability of the transition should not be compromised by the presence of cellular cosolutes.

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