Nitrogen-Anchored Boridene Enables Mg–CO₂ Batteries with High Reversibility

Nanoscale defect engineering plays a crucial role in incorporating extraordinary catalytic properties in two-dimensional materials by varying the surface groups or site interactions. Herein, we synthesized high-loaded nitrogen-doped Boridene (N-Boridene (Mo4/3(BnN1–n)2–mTz), N-doped concentration up to 26.78 at %) nanosheets by chemical exfoliation followed by cyanamide intercalation. Three different nitrogen sites are observed in N-Boridene, wherein the site of boron vacancy substitution mainly accounts for its high chemical activity. Attractively, as a cathode for Mg–CO2 batteries, it delivers a long-term lifetime (305 cycles), high-energy efficiency (93.6%), and ultralow overpotential (∼0.09 V) at a high current of 200 mA g–1, which overwhelms all Mg–CO2 batteries reported so far. Experimental and computational studies suggest that N-Boridene can remarkably change the adsorption energy of the reaction products and lower the energy barrier of the rate-determining step (*MgCO2 → *MgCO3·xH2O), resulting in the rapid reversible formation/decomposition of new MgCO3·5H2O products. The surging Boridene materials with defects provide substantial opportunities to develop other heterogeneous catalysts for efficient capture and converting of CO2

Systemic Lupus Erythematosus Patients Contain Significantly Less IgM against Mono-Methylated Lysine than Healthy Subjects

<div><p>Post-translational modifications on proteins are important in biological processes but may create neo-epitopes that induce autoimmune responses. In this study, we measured the serum IgG and IgM response to a set of non-modified or acetyl- and methyl-modified peptides corresponding to residues 1–19 of the histone 3 N-terminal tail in systemic lupus erythematosus (SLE) patients and healthy subjects. Our results indicated that the SLE patients and healthy subjects produced antibodies (Abs) to the peptides, but the two groups had different Ab isotype and epitope preferences. Abs to the non-modified form, H3_1–19, were of the IgG isotype and produced by SLE patients. They could not recognize the scrambled H3_1–19, which contained the same amino acid composition but a different sequence as H3_1–19. In comparison, healthy subjects in general did not produce IgG against H3_1–19. However, about 70% of the healthy subjects produced IgM Abs against mono-methylated K9 of H3_1–19 (H3_1–19K9me). Our further studies revealed that ε-amine mono-methylated lysine could completely inhibit the IgM binding to H3_1–19K9me, but lysine had no inhibitory effect. In addition, the IgM Abs could bind peptides containing a mono-methylated lysine residue but with totally different sequences. Thus, mono-methylated lysine was the sole epitope for the IgM. Interestingly, SLE patients had much lower levels of this type of IgM. There was no obvious correlation between the IgM levels and disease activity and the decreased IgM was unlikely caused by medical treatments.We also found that the IgM Abs were not polyreactive to dsDNA, ssDNA, lipopolysaccharide (LPS) or insulin and they did not exist in umbilical cord serum, implying that they were not natural Abs. The IgM Abs against mono-methylated lysine are present in healthy subjects but are significantly lower in SLE patients, suggesting a distinct origin of production and special physiological functions.</p></div

Polyreactivity test by ELISA.

<p>dsDNA, ssDNA, LPS or insulin was coated on microtiter plates as described in Materials and Methods. Sera (1∶100 dilution) and Abs purified from the H3_1–19 or H3_1–19K9me beads (1∶200 dilution) were tested. KT47 anti-human IgG or KT16 anti-human IgM Ab was used as the primary Ab and HRP-conjugated goat anti-mouse IgG was used as the secondary Ab. a, IgG(1–19^low91^low)IgM(1–19^high91^high); b, IgG(1–19^low91^low)IgM(1–19^high91^low); c, IgG(1–19^low91^low)IgM(1–19^low91^high); d, IgG(1–19^low91^low)IgM(1–19^low91^low); e, IgG(1–19^high91^x)IgM(1–19^x91^x). 1–19E, Abs eluted from the H3_1–19 beads; 91E, Abs eluted from the H3_1–19K9me beads. Data are expressed as mean+SEM. The results are representative of two separate experiments.</p

Effect of medical treatments on total IgM and IgM anti-H3_1–19K9me.

<p>(A) and (C) Total IgM of pediatric and adult samples. (B) and (D) IgM anti-H3_1–19K9me of pediatric and adult samples. <i>P</i> values between the healthy controls and treated SLE were calculated using the Student’s <i>t</i> test. The horizontal bars indicate the mean values in each group. The results are representative of two independent experiments.</p

Western blot for IgG and IgM eluted from H3₁_–19 and H3_1–19K9me beads.

<p>Equal volumes (1.5 ml) of pooled sera were first absorbed with the H3_1–19 beads and then with the H3_1–19K9me beads as described in the Materials and Methods. The beads were washed 5 times with 1 M NaCl, and the bound Abs were eluted with 50 µl elution buffer. 10 µl of the eluates underwent SDS-PAGE under reducing conditions and were then transferred onto nitrocellulose membranes. The membranes were cut at the 58 kDa position. IgG on the low molecular weight (<58 kDa) membrane and IgM on the high molecular weight (>58 kDa) membrane were detected. (A) Healthy adult samples; (B) aSLE patient samples. a, IgG(1–19^high91^x)IgM(1–19^x91^x); b, IgG(1–19^low91^low)IgM(1–19^high91^high); c, IgG(1–19^low91^low)IgM(1–19^high91^low); d, IgG(1–19^low91^low)IgM(1–19^low91^high); e, IgG(1–19^low91^low)IgM(1–19^low91^low). 1–19E, Abs eluted from the H3_1–19 beads; 91E, Abs eluted from the H3_1–19K9me beads. The percentages represent the sample proportion of each subgroup (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068520#pone-0068520-t001" target="_blank">Table 1</a>). The results are representative of two independent experiments.</p

Reactivity of purified IgG against H3 peptides.

<p>Equal volumes (1.5 ml) of the pooled serum samples from each subgroup were affinity purified using H3_1–19 and H3_1–19K9me beads in tandem (see Materials and Methods). Microtiter plates were coated with various peptides conjugated to BSA as indicated. Eluates from the H3_1–19 and H3_1–19K9me beads were separately tested for their reactivity against the peptides. KT47 anti-human IgG was used as the primary Ab and HRP-conjugated goat anti-mouse IgG was used as the secondary Ab. The samples were tested in duplicate. 1–19E, Abs eluted from the H3_1–19 beads; 91E, Abs eluted from the H3_1–19K9me beads. Data are expressed as mean+SEM. The results are representative of two independent experiments.</p

Distribution of IgG and IgM anti-H3_1–19 and H3_1–19K9me in SLE patients and healthy controls.

<p>1–19: H3_1–19; 91: H3_1–19K9me. Values over or below the mean+2SD of the healthy controls were set as high or below for IgG. Values over or below the mean of the total samples were set as high or low for IgM. x: high or low reactivity.</p

Reactivity of purified IgM against H3 peptides.

<p>Equal volumes (1.5 ml) of the pooled serum samples from each subgroup were affinity purified using H3_1–19 and H3_1–19K9me beads in tandem (see Materials and Methods). Microtiter plates were coated with various peptides conjugated to BSA as indicated. Eluates from the H3_1–19 and H3_1–19K9me beads were separately tested for their reactivity against the peptides. KT16 anti-human IgM was used as the primary Ab and HRP-conjugated goat anti-mouse IgG was used as the secondary Ab. The samples were tested in duplicate. 1–19E, Abs eluted from the H3_1–19 beads; 91E, Abs eluted from the H3_1–19K9me beads. Data are expressed as mean+SEM. The results are representative of two independent experiments.</p

Epitope analysis for IgG and IgM purified from the H3_1–19 or H3_1–19K9me beads.

<p>(A), (B) and (C) Microtiter plates were coated with H3_1–19, H3_1–19K9me, scrambled H3_1–19 (sH3_1–19) and scrambled H3_1–19K9me (sH3_1–19K9me) conjugated to BSA. IgM of healthy adults from the IgG(1–19^low91^low)IgM(1–19^high91^high) subgroup, IgM of aSLE patients from the IgG(1–19^low91^low)IgM(1–19^high91^high) subgroup and IgG of aSLE patients from the IgG(1–19^high91^x)IgM(1–19^x91^x) subgroup were tested. KT16 anti-human IgM mAb and KT47 anti-human IgG were used as the primary Abs. HRP-conjugated goat anti-mouse IgG was used as the secondary Ab. 1–19E, Abs eluted from the H3_1–19 beads; 91E, Abs eluted from the H3_1–19K9me beads. Data are expressed as mean+SEM. (D) Microtiter plates were coated with H3_1–19K9me or sH3_1–19K9me conjugated to BSA. IgM Abs of healthy adults from the IgG(1–19^low91^low)IgM(1–19^high91^high) subgroup were incubated with lysine (K) or ε-amine mono-methylated lysine (Kme) at indicated concentrations for 1 h at room temperature. KT16 anti-human IgM was used as the primary Ab. HRP-conjugated goat anti-mouse IgG was used as the secondary Ab. (E) Microtiter plates were coated with H3_1–19, H3_1–19K9me and GGK(me)GGSGGSGGSG (GGKme) conjugated to BSA. IgM of healthy adults from the IgG(1–19^low91^low)IgM(1–19^high91^high) subgroup was tested. KT16 anti-human IgM was used as the primary Ab. HRP-conjugated goat anti-mouse IgG was used as the secondary Ab. The results are representative of three separate experiments.</p

Reactivity of anti-H3_1–19K9me IgM against histones.

<p>Microtiter plates were coated with histones. IgM Abs purified from the H3_1–19K9me beads with or without prior absorption with lysine or mono-methylated lysine were tested. Background wells were not added with purified IgM. KT16 anti-human IgM was used as the primary Ab and HRP-conjugated goat anti-mouse IgG was used as the secondary Ab. Data are expressed as mean+SEM. The results are representative of three separate experiments.</p