Optimization of enzyme-producing conditions of Micrococcus sp. S-11 for L-cysteine production

Micrococcus sp.S-11 is capable of converting racemic 2-amino-Ä2-thiazoline-4-carboxylic acid (DL-ATC) to L-cysteine. The enzyme-producing conditions were optimized by using response surface methodology to maximize enzyme activity. Glucose, DL-ATC·3H2O and rotational speed have significant effects on enzyme activity. Their optimal values were 21.7 g/l glucose, 7.3 g/l DL-ATC·3H2O and 141 rpm rotational speed. Then validation experiments were conducted under optimal conditions. The enzyme activity was up to 2291 U/g, which was close to the predicted maximum enzyme activity (2284 U/g) and 31.4% higher than the initial activity (1743 U/g). A two-step culture was performed with the optimal conditions for cell growth in the first step and enzyme activity in the second step. The results suggested that high carbon/nitrogen (C/N) mass ratio was favorable to enzyme activity and the two-step culture strategy was proposed to be adopted for achieving both high biomass and enzyme production simultaneously.Key words: L-Cysteine, enzyme activity, Plackett-Burman design, response surface methodology, two-step culture

Study of e+e−→ppˉe^+e^- \rightarrow p\bar{p} in the vicinity of ψ(3770)\psi(3770)

Using 2917 $\rm{pb}^{-1}$ of data accumulated at 3.773~$\rm{GeV}$, 44.5~$\rm{pb}^{-1}$ of data accumulated at 3.65~$\rm{GeV}$ and data accumulated during a $\psi(3770)$ line-shape scan with the BESIII detector, the reaction $e^+e^-\rightarrow p\bar{p}$ is studied considering a possible interference between resonant and continuum amplitudes. The cross section of $e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p}$, $\sigma(e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p})$, is found to have two solutions, determined to be ($0.059\pm0.032\pm0.012$) pb with the phase angle $\phi = (255.8\pm37.9\pm4.8)^\circ$ ($<$0.11 pb at the 90% confidence level), or $\sigma(e^+e^-\rightarrow\psi(3770)\rightarrow p\bar{p}) = (2.57\pm0.12\pm0.12$) pb with $\phi = (266.9\pm6.1\pm0.9)^\circ$ both of which agree with a destructive interference. Using the obtained cross section of $\psi(3770)\rightarrow p\bar{p}$, the cross section of $p\bar{p}\rightarrow \psi(3770)$, which is useful information for the future PANDA experiment, is estimated to be either ($9.8\pm5.7$) nb ($<17.2$ nb at 90% C.L.) or $(425.6\pm42.9)$ nb

Recent developments in protein–ligand affinity mass spectrometry

This review provides an overview of direct and indirect technologies to screen protein–ligand interactions with mass spectrometry. These technologies have as a key feature the selection or affinity purification of ligands in mixtures prior to detection. Specific fields of interest for these technologies are metabolic profiling of bioactive metabolites, natural extract screening, and the screening of libraries for bioactives, such as parallel synthesis libraries and small combichem libraries. The review addresses the principles of each of the methods discussed, with a focus on developments in recent years, and the applicability of the methods to lead generation and development in drug discovery

ICAM-1 expression and organization in human endothelial cells is sensitive to gravity

Transendothelial migration (TEM) of immune cells is a crucial process during a multitude of physiological and pathological conditions such as development, defense against infections and wound healing. Migration within the body tissues and through endothelial barriers is strongly dependent and regulated both by cytoskeletal processes and by expression of surface adhesion molecules such as ICAM-1 and VCAM-1. Space flight experiments have confirmed that TEM will be inhibited and may cause astronauts’ immune function decreased and make them easy for infection. We used NASA RCCS to provide a simulated microgravity environment; endothelial cells were cultured on microcarrier beads and activated by TNF-α. Results demonstrate after clinorotation ICAM-1 expression increased, consistent with the notion in parabolic flights. However, VCAM-1 showed no significant change between activated or inactivated cells. Depolymerization of F-actin and clustering of ICAM-1 on cell membrane were also observed in short-term simulated microgravity, and after 24 h clinorotation, actin fiber rearrangement was initiated and clustering of ICAM-1 became stable. ICAM-1 mRNA and VCAM-1 mRNA were up-regulated after 30 min clinorotation, and returned to the same level with controls after 24 h clinorotation

Dynamic evolution and the caloric curve for medium mass nuclei

International audienceSelf-consistent coalescence model analyses of light particle emission have been used to follow the evolution of the temperatures and densities of A≈110 nuclei produced in violent collisions induced by four different 47 AMeV projectiles. The degree of expansion of the emitting system increases with increasing projectile mass. The caloric curve derived for these expanding A≈110 nuclei plateaus near T=7 MeV. The plateau extends from 3.5 to 6.9 MeV/u excitation energy