Calcineurin (CN) exhibits a bimodal regulation by different
concentrations of vanadyl ions (VO[2+]) in the
presence of Mn[2+]. Low concentrations of VO[2+] inhibit
the enzyme, with 50 VO[2+] completely inhibiting CN
activity, while high concentrations, up to 500 VO[2+], stimulate the CN activity. A similar bimodal regulation of CN was not observed with either calcium or vanadate under the same conditions. Xband electron spin resonance spectroscopy, used to study the binding of VO[2+] to the catalytic subunit A of calcineurin, show that there are two kinds of binding sites in the A subunit.
A deletion mutant (V314) of the calcineurin A subunit
was constructed using site-directed mutagenesis. Its
phosphatase activity and function were then characterized.
The V314 deletion significantly altered the
phosphatase activity, which was more than ten times
higher than that of wild-type calcineurin, the calcineurin-
the effect of metal ions and calcineurin subunit interaction.
We propose that the change of the activity and
function of V314 is due to conformational changes of
calcineurin to benefit the binding of, or stimulation by,
Mn2+, or to affect the interaction between the A and B
Saccharomyces cerevisiae calcineurin (CN) consists of a catalytic subunit CNA1 or CNA2 and a regulatory subunit CNB1. The kinetics of activation of yeast CN holoenzymes and their catalytic domains by Mn2+ were investigated. We report that the in vitro phosphatase reaction activated by Mn2+ typically has a pronounced initial lag phase caused by slow conformational rearrangement of the holoenzyme-Mn2+. A similar lag phase was detected using just the catalytic domain of yeast CN, indicating that the slowness of Mn2+-induced conformational change of CN results from a rearrangement within the catalytic domain. The Mn2+-activation of CN was reversible. The dissociation constant of the CN heterodimer containing the CNA2 subunit in the presence of Mn2+ was 3-fold higher than that of CN containing the CNA1 subunit and that of the catalytic domains of CNA1 and CNA2, pointing to differences between the residues surrounding the Mn2+-binding sites of CNA1 and CNA2.
Acute respiratory distress syndrome is a common syndrome in clinical practice, particularly in the Intensive Care Unit (ICU), with a high morbidity and mortality rate. The prerequisite of its early treatment is early diagnosis. The early biomarkers hence have been gradually favored. While some new and original biomarkers continue to be the focus of research, some biomarkers such as C-reactive protein and procalcitonin have been widely used in clinical practice.
Mung bean starch has been manufactured by sour liquid processing for hundreds of years in China. Ions in sour liquid will impact the starch properties and vermicelli quality. To understand the role of the ions act on the processing and starch quality, different concentrations of NaCl or KCl effect on precipitation rate of starch slurry, starch properties and the potential quality of vermicelli were studied. Results showed that starch slurry took a shorter time to start precipitating when NaCl or KCl concentration increased from 0.027mol/L to 0.088 mol/L. Light transmittance, swelling power and peak viscosity of mung bean starch was significantly decreased from 0.02mol/L to 0.10mol/L NaCl or KCl. Increasing To, Tp, Tc and Tc-To was noticed from 0.02mol/L to 0.10 mol/L NaCl or 0.04mol/L to 0.08mol/L KCl. These changes would be helpful for improving vermicelli quality. However increasing solubility at test concentrations of NaCl and KCl was not good for vermicelli quality.
The effects of scandium (Sc) solute addition on the structural stability, mechanical strength, and electronic structure of magnesium-lithium (Mg-Li) ordered alloy were comprehensively studied by first-principles calculations. Two kinds of MgLi-Sc substitutional alloys (Mg-substituted Mg8−xLi8Scx and Li-substituted Mg8Li8−xScx) hold cubic lattice symmetry and become more stable with the increase in Sc content. The mechanical properties, including single crystal elastic constants, polycrystalline elastic moduli, and elastic anisotropy behaviors, have been systematically studied for two considered MgLi-Sc substitutional alloys. It was found that Mg8Li8−xScx exhibits larger elastic moduli than those of Mg8−xLi8Scx with the same Sc content; however, the derived elastic moduli of two substitutional alloys showed nonlinear variations as a function of Sc addition. Calculated stress–strain curves show an increasing of ideal tensile strengths and critical strains of the MgLi-Sc substitutional alloys along the <110> and <111> directions with Sc addition, indicating that the cubic MgLi-Sc substitutional alloy is mechanically harder and less brittle at higher Sc content. Furthermore, the developments of the electronic structures of two types of the studied alloys with increasing Sc addition were also investigated by the density of states and electronic localization function calculations.