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Structural insights into metal-metalloid glasses from mass spectrometry.

ABSTRACT: Despite being studied for nearly 50 years, smallest chemically stable moieties in the metallic glass (MG) could not be found experimentally. Herein, we demonstrate a novel experimental approach based on electrochemical etching of amorphous alloys in inert solvent (acetonitrile) in the presence of a high voltage (1 kV) followed by detection of the ions using electrolytic spray ionization mass spectrometry (ESI MS). The experiment shows stable signals corresponding to Pd, PdSi and PdSi2 ions, which emerges due to the electrochemical etching of the Pd80Si20 metallic glass electrode. These fragments are observed from the controlled dissolution of the Pd80Si20 melt-spun ribbon (MSR) electrode. Annealed electrode releases different fragments in the same experimental condition. These specific species are expected to be the smallest and most stable chemical units from the metallic glass which survived the chemical dissolution and complexation (with acetonitrile) process. Theoretically, these units can be produced from the cluster based models for the MG. Similar treatment on Pd40Ni40P20 MSR resulted several complex peaks consisting of Pd, Ni and P in various combinations suggesting this can be adopted for any metal-metalloid glass.

SUBMITTER: Baksi A

PROVIDER: S-EPMC7567878 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Structural insights into metal-metalloid glasses from mass spectrometry.

Baksi Ananya A Bag Soumabha S Kruk Robert R Nandam Sree Harsha SH Hahn Horst H

Scientific reports 20201015 1

Despite being studied for nearly 50 years, smallest chemically stable moieties in the metallic glass (MG) could not be found experimentally. Herein, we demonstrate a novel experimental approach based on electrochemical etching of amorphous alloys in inert solvent (acetonitrile) in the presence of a high voltage (1 kV) followed by detection of the ions using electrolytic spray ionization mass spectrometry (ESI MS). The experiment shows stable signals corresponding to Pd, PdSi and PdSi<sub>2</sub> ...[more]

PMID: 33060717

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Project description:Laforin and starch excess 4 (SEX4) are founding members of a class of phosphatases that dephosphorylate phosphoglucans. Each protein contains a carbohydrate binding module (CBM) and a dual-specificity phosphatase (DSP) domain. The gene encoding laforin is mutated in a fatal neurodegenerative disease called Lafora disease (LD). In the absence of laforin function, insoluble glucans that are hyperphosphorylated and exhibit sparse branching accumulate. It is hypothesized that these accumulations trigger the neurodegeneration and premature death of LD patients. We recently demonstrated that laforin removes phosphate from phosphoglucans and hypothesized that this function inhibits insoluble glucan accumulation. Loss of SEX4 function in plants yields a similar cellular phenotype; an excess amount of insoluble, hyperphosphorylated glucans accumulates in cells. While multiple groups have shown that these phosphatases dephosphorylate phosphoglucans, there is no structure of a glucan phosphatase and little is known about the mechanism whereby they perform this action. We utilized hydrogen-deuterium exchange mass spectrometry (DXMS) and structural modeling to probe the conformational and structural dynamics of the glucan phosphatase SEX4. We found that the enzyme does not undergo a global conformational change upon glucan binding but instead undergoes minimal rearrangement upon binding. The CBM has improved protection from deuteration when bound to glucans, confirming its role in glucan binding. More interestingly, we identified structural components of the DSP that also have improved protection from deuteration upon glucan addition. To determine the position of these regions, we generated a homology model of the SEX4 DSP. The homology model shows that all of these regions are adjacent to the DSP active site. Therefore, our results suggest that these regions of the DSP participate in the presentation of the phosphoglucan to the active site and provide the first structural analysis and mode of action of this unique class of phosphatases.

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Structural insights into metal-metalloid glasses from mass spectrometry.

Publications

Structural insights into metal-metalloid glasses from mass spectrometry.

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