Glycine-Induced Synthesis of Vaterite via Direct Aqueous Mineral Carbonation of Flue Gas Desulfurization Gypsum

Mineral carbonation of flue gas desulfurization gypsum (FGDG) can not only sequester CO2 to mitigate the greenhouse effect, but also produce CaCO3 to generate economic benefit. A mixture of calcite and vaterite CaCO3 was produced by FGDG carbonation in our previous study. Nevertheless, the production of uniform crystalline CaCO3, especially for vaterite, still maintains a big challenge via carbonation of FGDG. Herein, nearly pure vaterite was synthesized via FGDG carbonation in the presence of glycine was reported firstly. The results show that the content of vaterite increased from 60% to 97% with increasing glycine concentration and then kept a constant value, indicating that glycine can promote the formation of vaterite and inhibit the growth of calcite. Additionally, the investigation of vaterite growth mechanism in the presence of glycine demonstrated that the formation of intermediate, glycinate calcium, played an important role to stimulate the growth of vaterite. This study provides a new insight to produce a high-valued vaterite CaCO3 during the direct mineral carbonation of FGDG.

SHMT1-RNA interaction dynamically regulates serine and glycine concentration in cells

Serine hydroxymethyltransferase (SHMT) regulates the serine-glycine one carbon metabolism and plays a role in cancer metabolic reprogramming. Two SHMT isozymes are acting in the cell: SHMT1 encoding the cytoplasmic isozyme (SHMT1) and SHMT2 encoding the mitochondrial one (SHMT2). Here we present a molecular model built on experimental data reporting the interaction between SHMT1 protein and SHMT2 mRNA, recently discovered in lung cancer cells. Using a stochastic dynamic model, we show that RNA moieties dynamically regulate serine and glycine concentration, shaping the system behaviour. For the first time we observe an active functional role of the RNA in the regulation of the serine-glycine metabolism and availability, which unravels a complex layer of regulation that cancer cells exploit to fine tune aminoacids availability according to their metabolic needs. The quantitative model presented herein exploits RNA molecules as metabolic switches of the SHMT1 activity. Our results pave the way for the development of RNA-based molecules able to unbalance serine metabolism in cancer cells.

Glycine by MR spectroscopy is an imaging biomarker of glioma aggressiveness

Background High-grade gliomas likely remodel the metabolic machinery to meet the increased demands for amino acids and nucleotides during rapid cell proliferation. Glycine, a non-essential amino acid and intermediate of nucleotide biosynthesis, may increase with proliferation. Non-invasive measurement of glycine by magnetic resonance spectroscopy (MRS) was evaluated as an imaging biomarker for assessment of tumor aggressiveness. Methods We measured glycine, 2-hydroxyglutarate (2HG), and other tumor-related metabolites in 35 glioma patients using an MRS sequence tailored for co-detection of glycine and 2HG in gadolinium-enhancing and non-enhancing tumor regions on 3T MRI. Glycine and 2HG concentrations as measured by MRS were correlated with tumor cell proliferation (MIB-1 labeling index), expression of mitochondrial serine hydroxymethyltransferase (SHMT2), and glycine decarboxylase (GLDC) enzymes, and patient overall survival. Results Elevated glycine was strongly associated with presence of gadolinium enhancement, indicating more rapidly proliferative disease. Glycine concentration was positively correlated with MIB-1, and levels higher than 2.5 mM showed significant association with shorter patient survival, irrespective of isocitrate dehydrogenase status. Concentration of 2HG did not correlate with MIB-1 index. A high glycine/2HG concentration ratio, >2.5, was strongly associated with shorter survival (P < 0.0001). GLDC and SHMT2 expression were detectable in all tumors with glycine concentration, demonstrating an inverse correlation with GLDC. Conclusions The data suggest that aggressive gliomas reprogram glycine-mediated one-carbon metabolism to meet the biosynthetic demands for rapid cell proliferation. MRS evaluation of glycine provides a non-invasive metabolic imaging biomarker that is predictive of tumor progression and clinical outcome. Key Points 1. Glycine and 2-hydroxyglutarate in glioma patients are precisely co-detected using MRS at 3T. 2. Tumors with elevated glycine proliferate and progress rapidly. 3. A high glycine/2HG ratio is predictive of shortened patient survival.

Kinetics of iron(III) hydrolysis and precipitation in aqueous glycine solutions assessed by voltammetry

The kinetics of iron(III) hydrolysis and precipitation in aqueous glycine solutions were studied by cathodic voltammetry with a mercury drop electrode. The kinetics was controlled by changing ionic strength (I), pH and glycine concentration. Voltammetric measurements clearly showed formation and dissociation of a soluble Fe(III)–glycine complex, formation of iron(III) hydroxide and its precipitation. The rate constants of iron(III) hydroxide precipitation were assessed. The precipitation is first-order with respect to dissolved inorganic iron(III). The calculated rate constants of iron(III) precipitation varied from 0.18 × 10–5 s–1 (at 0.2 M total glycine, pH 7.30, I = 0.6 mol dm–3) to 2.22 × 10–3 s–1 (at 0.1 M total glycine, pH 7.30, I = 0.2 mol dm–3). At 0.5 M total glycine and I = 0.6 mol dm–3, the iron(III) precipitation was not observed.