Hydrogen bond revealed: In a cobalt(II) porphyrin complex which serves as a model for the dioxygen binding site of myoglobin (Mb) and hemoglobin, a distal hydrogen bond to the bound O2 was identified and characterized by pulse ENDOR spectroscopy. A similar but stronger hydrogen bond was revealed with the same methods in natural Co‐Mb‐O2.

Distal hydrogen bonding in natural dioxygen binding proteins is crucial for the discrimination between different potential ligands such as O(2) or CO. In the present study, we probe the chemical requirements for proper distal hydrogen bonding in a series of synthetic model compounds for dioxygen-binding heme proteins. The model compounds 1-Co to 7-Co bear different distal residues. The hydrogen bonding in their corresponding dioxygen adducts is directly measured by pulse EPR spectroscopy. The geometrical requirements for this interaction to take place were found to be narrow and very specific. Only two model complexes, 1-Co and 7-Co, form a hydrogen bond to bound dioxygen, which was characterized in terms of geometry and nature of the bond. The geometry and dipolar nature of this interaction in 1-Co-O(2) is more similar to the one in natural cobalt myoglobin (Co-Mb), making 1-Co the best model compound in the entire series.

Hyperfein detektiert: Mit Puls‐ENDOR‐Spektroskopie wurde im gezeigten Cobalt(II)‐Porphyrinkomplex, der als Modell für die Bindungstasche des Myoglobins und Hämoglobins dient, eine distale Wasserstoffbrücke zum gebundenen Disauerstoff direkt nachgewiesen und charakterisiert. Mit denselben Methoden wurde eine gleichartige, aber stärkere Wechselwirkung im natürlichen Co‐Mb‐O2 nachgewiesen.

Data on the response to the COVID‐19 vaccine in patients with myeloid malignancy, who are at severe risk in case of infection, have not emerged. In a study of 69 patients with myeloid malignancies, including 46 patients with acute myeloid leukaemia (AML) and 23 patients with myelodysplastic syndrome (MDS), anti‐spike SARS‐CoV‐2 antibody titres were measured 3 months after the second mRNA‐based vaccination. Seroconversion rates for AML and MDS were 94.7% and 100% respectively, with no significant difference from healthy controls (HCs). Patients with MDS showed a significantly lower antibody titre than that in HCs or AML patients. In AML patients, the antibody titres were comparable to those in HCs when treatment was completed, but lower in patients under maintenance therapy. The response to COVID‐19 vaccine appears to be related to disease and treatment status. Patients with myeloid malignancies may be more responsive to vaccines than patients with lymphoid malignancies.

Solid-pseudopapillary neoplasms (SPN) are rare pancreatic tumors. The etiology of SPN involves mutations in the gene that encodes β-catenin (CTNNB1). We herein report the case of a 23-year-old woman with a large SPN with proliferating tumor cells that displayed both solid and pseudo-papillary patterns. The simultaneous nuclear accumulation and loss of membrane localization of β-catenin and E-cadherin was specifically observed in the tumor cells. Further, the tumor cells were shown to harbor a missense mutation in exon 3 of CTNNB1. We also present a review of the literature describing the clustering of CTNNB1 mutations in patients with SPN.