Extending the Chemistry of Layered Solids and Nanosheets: Chemistry and Structure of MAX Phases, MAB Phases and MXenes.

MAX phases are layered solids with unique properties combining characteristics of ceramics and metals. MXenes are their two-dimensional siblings that can be synthesized as van der Waals-stacked and multi-/single-layer nanosheets, which possess chemical and physical properties that make them interesting for a plethora of applications. Both families of materials are highly versatile in terms of their chemical composition and theoretical studies suggest that many more members are stable and can be synthesized. This is very intriguing because new combinations of elements, and potentially new structures, can lead to further (tunable) properties. In this review, we focus on the synthesis science (including non-conventional approaches) and structure of members less investigated, namely compounds with more exotic M-, A-, and X-elements, for example nitrides and (carbo)nitrides, and the related family of MAB phases.

Detailed Analysis of the Synthesis and Structure of MAX Phase (Mo0.75V0.25)5AlC4 and Its MXene Sibling (Mo0.75V0.25)5C4.

MAX phases with the general formula Mn+1AXn are layered carbides, nitrides, and carbonitrides with varying stacking sequence of layers of M6X octahedra and the A element depending on n. While "211" MAXphases (n = 1) are very common, MAX phases with higher n, especially n ≥ 3, have hardly been prepared. This work addresses open questions regarding the synthesis conditions, structure, and chemical composition of the "514" MAX phase. In contrast to literature reports, no oxide is needed to form the MAX phase, yet multiple heating steps at 1,600 °C are required. Using high-resolution X-ray diffraction, the structure of (Mo1-xVx)5AlC4 is thoroughly investigated, and Rietveld refinement suggests P-6c2 as the most fitting space group. SEM/EDS and XPS show that the chemical composition of the MAX phase is (Mo0.75V0.25)5AlC4. It was also exfoliated into its MXene sibling (Mo0.75V0.25)5C4 using two different techniques (using HF and an HF/HCl mixture) that lead to different surface terminations as shown by XPS/HAXPES measurements. Initial investigations of the electrocatalytic properties of both MXene versions show that, depending on the etchant, (Mo0.75V0.25)5C4 can reduce hydrogen at 10 mA cm-2 with an overpotential of 166 mV (HF only) or 425 mV (HF/HCl) after cycling the samples, which makes them a potential candidate as an HER catalyst.

Myelodysplastic Syndrome and Sweet's Syndrome Are Associated with a Mutation in Isocitrate Dehydrogenase 1.

BACKGROUND: Sweet's syndrome (SS) is a febrile neutrophilic dermatosis that has been clinically linked to hematological malignancies, particularly myelodysplastic syndrome (MDS), in a number of case series. Many epigenetic changes underlying MDS have been identified, such as a mutation in the isocitrate dehydrogenase 1 (IDH1) gene, which causes DNA hypermethylation and alteration of a number of genes that lead to leukemogenesis. However, the pathogenesis of malignancy-associated SS is unknown. CASE REPORT: We present two patients who were diagnosed with SS and concomitant IDH1-mutated MDS. Immunohistochemical staining of their skin lesions showed neutrophils diffusely positive for the IDH1 mutation. CONCLUSION: These cases demonstrate that IDH1 mutation may be implicated in the pathogenesis of malignancy-associated SS. Future investigation to elucidate this pathway is warranted. Establishing this molecular link can provide an earlier identification of patients with SS who are also at increased risk for developing MDS.

Hispanic ethnicity is associated with younger age at presentation but worse survival in acute myeloid leukemia.

SEER data and a Bronx validation cohort demonstrate that Hispanics present with AML at younger age but have shorter survival than whites.Increased frequency of high-risk mutations in Hispanics provides a potential biologic explanation for poorer outcomes in Hispanics.

Resveratrol prevents rapamycin-induced upregulation of autophagy and selectively induces apoptosis in TSC2-deficient cells.

The mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway is hyperactivated in a variety of cancers and disorders, including lymphangioleiomyomatosis (LAM) and tuberous sclerosis complex (TSC), which are characterized by mutations in tumor suppressors TSC1 or TSC2. The concern with the use of mTORC1 inhibitors, such as rapamycin or its analogs (rapalogs), is that they cause upregulation of autophagy and suppress the negative feedback loop to Akt, which promotes cell survival, causing the therapy to be only partially effective, and relapse occurs upon cessation of treatment. In this study, we investigate the use of rapamycin in combination with resveratrol, a naturally occurring polyphenol, in TSC2-deficient cells. We tested whether such combination would prevent rapamycin-induced upregulation of autophagy and shift the cell fate toward apoptosis. We found that this combination treatment blocked rapamycin-induced upregulation of autophagy and restored inhibition of Akt. Interestingly, the combination of rapamycin and resveratrol selectively promoted apoptosis of TSC2-deficient cells. Thus, the addition of resveratrol to rapamycin treatment may be a promising option for selective and targeted therapy for diseases with TSC loss and mTORC1 hyperactivation.