Recovery efficiency of a hydrophilic ionic-liquid aqueous biphasic system for the primary purification of cytochrome c from simulated Saccharomyces cerevisiae fermentation broth
PROCESS BIOCHEMISTRY
Authors: Lin, Yu-Yu; Kee, Phei Er; Ng, Hui-Suan; Lan, John Chi-Wei
Abstract
Ionic liquid-based aqueous biphasic system (ILABS) has emerged as an attractive green approach for the extraction and separation of various biomolecules. The growing market demands of cytochrome c (cyt c) due to its vast uses in medical applications have urged the search for cost-efficient approaches for the production and purification of cyt c. In this study, the feasibility of ILABS to recover cyt c from simulated Saccharomyces cerevisiae cell cultures was investigated by evaluating the effects of phase composition, pH, and additives concentration on the recovery efficiency of cyt c. The ILABS was developed using the hydrophilic ionic liquids, 1-hexyl-3-methylimidazolium bromide ((C6mim)Br) and potassium citrate. The optimal separation conditions for recovery of cyt c from simulated cells cultures were attained with ILABS of pH 9 comprising of 28% (w/w) of (C6mim)Br and 24% (w/w) of potassium citrate and the addition of 0.2% (w/w) NaCl at room temperature (25 degrees C). Cyt c was recovered in the IL-rich phase with partition coefficient (Kc) of 364.00 +/- 1.09, recovery yield (Y) of 99.76% +/- 0.03 and selectivity (S) of 223.31 +/- 0.56. The results suggest that ILABS can efficiently recover cyt c from microbial fermentation broth with high recovery yields and separation efficiency.
Cysteine Oxidations in Mitochondrial Membrane Proteins: The Case of VDAC Isoforms in Mammals
FRONTIERS IN CELL AND DEVELOPMENTAL BIOLOGY
Authors: Reina, Simona; Pittala, Maria Gaetana Giovanna; Guarino, Francesca; Messina, Angela; De Pinto, Vito; Foti, Salvatore; Saletti, Rosaria
Abstract
Cysteine residues are reactive amino acids that can undergo several modifications driven by redox reagents. Mitochondria are the source of an abundant production of radical species, and it is surprising that such a large availability of highly reactive chemicals is compatible with viable and active organelles, needed for the cell functions. In this work, we review the results highlighting the modifications of cysteines in the most abundant proteins of the outer mitochondrial membrane (OMM), that is, the voltage-dependent anion selective channel (VDAC) isoforms. This interesting protein family carries several cysteines exposed to the oxidative intermembrane space (IMS). Through mass spectrometry (MS) analysis, cysteine posttranslational modifications (PTMs) were precisely determined, and it was discovered that such cysteines can be subject to several oxidization degrees, ranging from the disulfide bridge to the most oxidized, the sulfonic acid, one. The large spectra of VDAC cysteine oxidations, which is unique for OMM proteins, indicate that they have both a regulative function and a buffering capacity able to counteract excess of mitochondrial reactive oxygen species (ROS) load. The consequence of these peculiar cysteine PTMs is discussed.