Apohemoglobin-haptoglobin complex attenuates the pathobiology of circulating acellular hemoglobin and heme

This study highlights the apoHb-Hp complex as a novel therapeutic strategy to attenuate the adverse systemic and microvascular responses to intravascular Hb and heme exposure. In vitro and in vivo Hb exchange and heme transfer experiments demonstrated proof-of-concept Hb/heme ligand transfer to apoHb-Hp. The apoHb-Hp complex reverses Hb- and heme-induced systemic hypertension and microvascular vasoconstriction, preserves microvascular blood flow, and functional capillary density. In summary, the unique properties of the apoHb-Hp complex prevent adverse systemic and microvascular responses to Hb and heme-albumin exposure and introduce a novel therapeutic approach to facilitate simultaneous removal of extracellular Hb and heme.

Simulations of NPC1(NTD):NPC2 Protein Complex Reveal Cholesterol Transfer Pathways

The Niemann Pick type C (NPC) proteins, NPC1 and NPC2, are involved in the lysosomal storage disease, NPC disease. The formation of a NPC1–NPC2 protein–protein complex is believed to be necessary for the transfer of cholesterol and lipids out of the late endosomal (LE)/lysosomal (Lys) compartments. Mutations in either NPC1 or NPC2 can lead to an accumulation of cholesterol and lipids in the LE/Lys, the primary phenotype of the NPC disease. We investigated the NPC1(NTD)–NPC2 protein–protein complex computationally using two putative binding interfaces. A combination of molecular modeling and molecular dynamics simulations reveals atomic details that are responsible for interface stability. Cholesterol binding energies associated with each of the binding pockets for the two models are calculated. Analyses of the cholesterol binding in the two models support bidirectional ligand transfer when a particular interface is established. Based on the results, we propose that, depending on the location of the cholesterol ligand, a dynamical interface between the NPC2 and NPC1(NTD) proteins exists. Structural features of a particular interface can lower the energy barrier and stabilize the passage of the cholesterol substrate from NPC2 to NPC1(NTD).

Synthesis, solid-state structures and reduction reactions of heteroleptic Ge(II) and Sn(II) β-ketoiminate complexes

A series of new heteroleptic divalent germaniun and tin complexes of the general type L1,4GeN(SiMe3)2 (1, 2) and L1−4SnN(SiMe3)2 (3–6) were synthesized by reaction of β-ketimines L1−4H with Ge[N(SiMe3)2]2 and Sn[N(SiMe3)2]2, respectively. The reaction of 3 with the strong Mg(I) reductant L5Mg yielded the heteroleptic complex L1MgL57 after ligand transfer from tin to magnesium, whereas analogous reactions of L4GeN(SiMe3)22 and L4SnN(SiMe3)26 with L5Mg occurred with formation of insoluble precipitates, transfer of the amido substituent from the group 14 metal to magnesium and subsequent formation of the heteroleptic magnesium complex L5MgN(SiMe3)2 (8). 1–8 were characterized by heteronuclear NMR (1H, 13C, 119Sn) and IR spectroscopy, elemental analysis and single-crystal X-ray diffraction (L4SnN(SiMe3)26, L1MgL57).

Ligand and membrane-binding behavior of the phosphatidylinositol transfer proteins PITPα and PITPβ

Phosphatidylinositol transfer proteins (PITPs) are believed to be lipid transfer proteins because of their ability to transfer either phosphatidylinositol (PI) or phosphatidylcholine (PC) between membrane compartments, in vitro. However, the detailed mechanism of this transfer process is not fully established. To further understand the transfer mechanism of PITPs we examined the interaction of PITPs with membranes using dual polarization interferometry (DPI), which measures protein binding affinity on a flat immobilized lipid surface. In addition, a fluorescence resonance energy transfer (FRET)-based assay was also employed to monitor how quickly PITPs transfer their ligands to lipid vesicles. DPI analysis revealed that PITPβ had a higher affinity to membranes compared with PITPα. Furthermore, the FRET-based transfer assay revealed that PITPβ has a higher ligand transfer rate compared with PITPα. However, both PITPα and PITPβ demonstrated a preference for highly curved membrane surfaces during ligand transfer. In other words, ligand transfer rate was higher when the accepting vesicles were highly curved.