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Metal carbides, nitrides, or carbonitrides of early transition metals, better known as MXenes, possess notable structural, electrical, and magnetic properties. Analyzing electronic structures by calculating structural stability, band structure, density of states, Bader charge transfer, and work functions utilizing first principle calculations, we revealed that titanium nitride MXenes, namely TiN and TiN, have excess anionic electrons in their lattice voids, making them MXene electrides. Bulk TiN has competing antiferromagnetic (AFM) and ferromagnetic(FM) configurations with slightly more stable AFM configuration, while the TiN MXene is nonmagnetic. Although TiN favors AFM configuration with hexagonal crystal systems having point group symmetry, TiN does not support altermagnetism. The monolayer of the TiN MXene is a ferromagnetic electride. These unique properties of having non-nuclear interstitial anionic electrons in the electronic structure of titanium nitride MXene have not yet been reported in the literature. Density functional theory calculations show TiN is neither an electride, MXene, or magnetic. 

Human cytochrome P450 (P450) 27A1 catalyzes the hydroxylation of cholesterol and vitamin D derivatives. P450 27A1 is localized in the mitochondria and is reduced by its redox partner protein adrenodoxin twice for each catalytic cycle. The reliance on adrenodoxin is conserved across all human mitochondrial P450 enzymes. This study examines the adrenodoxin interaction with P450 27A1 and draws comparisons with studies of other P450 enzymes to determine if differences exist. The P450-adrenodoxin complex structure was examined by chemical crosslinking and analyzed by mass spectrometry. The effect of adrenodoxin concentration on P450 27A1 function was assessed by studying effects on steady state enzyme kinetics parameters and equilibrium substrate binding. The results suggest that adrenodoxin binds to P450 27A1 at a proximal site like other P450 enzymes but differs in the specific residues involved. Furthermore, the presence of adrenodoxin and/or substrate decreases the number of interprotein and intraprotein crosslinks observed, indicating that these components change the conformation of the P450 enzyme. Increased adrenodoxin concentration causes the P450 and vitamin D3 kcat value to increase, the kcat/Km value to decrease, and the substrate Kd to remain constant. These results suggest adrenodoxin alters enzyme efficiency beyond electron transfer without affecting substrate loading. The adrenodoxin effects on P450 27A1 kinetics and equilibrium constants differ from those of other human mitochondrial P450 enzymes. In total, these structural and functional studies suggest that while the general adrenodoxin binding site and function is conserved across P450 enzymes, the details and additional effects of this interaction vary.