Quantitative systems pharmacology model of erythropoiesis to simulate therapies targeting anemia due to chronic kidney disease.

Anemia induced by chronic kidney disease (CKD) has multiple underlying mechanistic causes and generally worsens as CKD progresses. Erythropoietin (EPO) is a key endogenous protein which increases the number of erythrocyte progenitors that mature into red blood cells that carry hemoglobin (Hb). Recombinant human erythropoietin (rHuEPO) in its native and re-engineered forms is used as a therapeutic to alleviate CKD-induced anemia by stimulating erythropoiesis. However, due to safety risks associated with erythropoiesis-stimulating agents (ESAs), a new class of drugs, prolyl hydroxylase inhibitors (PHIs), has been developed. Instead of administering exogenous EPO, PHIs facilitate the accumulation of HIF-α, which results in the increased production of endogenous EPO. Clinical trials for ESAs and PHIs generally involve balancing decisions related to safety and efficacy by carefully evaluating the criteria for patient selection and adaptive trial design. To enable such decisions, we developed a quantitative systems pharmacology (QSP) model of erythropoiesis which captures key aspects of physiology and its disruption in CKD. Furthermore, CKD virtual populations of varying severities were developed, calibrated, and validated against public data. Such a model can be used to simulate alternative trial protocols while designing phase 3 clinical trials, as well as an asset for reverse translation in understanding emerging clinical data.

Neutral gas pressure dependence of ion-ion mutual neutralization rate constants using Landau-Zener theory coupled with trajectory simulations.

In this computational study, we describe a self-consistent trajectory simulation approach to capture the effect of neutral gas pressure on ion-ion mutual neutralization (MN) reactions. The electron transfer probability estimated using Landau-Zener (LZ) transition state theory is incorporated into classical trajectory simulations to elicit predictions of MN cross sections in vacuum and rate constants at finite neutral gas pressures. Electronic structure calculations with multireference configuration interaction and large correlation consistent basis sets are used to derive inputs to the LZ theory. The key advance of our trajectory simulation approach is the inclusion of the effect of ion-neutral interactions on MN using a Langevin representation of the effect of background gas on ion transport. For H+ - H- and Li+ - H(D)-, our approach quantitatively agrees with measured speed-dependent cross sections for up to ∼105 m/s. For the ion pair Ne+ - Cl-, our predictions of the MN rate constant at ∼1 Torr are a factor of ∼2 to 3 higher than the experimentally measured value. Similarly, for Xe+ - F- in the pressure range of ∼20 000-80 000 Pa, our predictions of the MN rate constant are ∼20% lower but are in excellent qualitative agreement with experimental data. The paradigm of using trajectory simulations to self-consistently capture the effect of gas pressure on MN reactions advanced here provides avenues for the inclusion of additional nonclassical effects in future work.

Reactions of Thianthrene and 10-Phenylphenothiazine with the Lewis Acids─Titanium Tetrachloride, Titanium Tetrabromide, Tin(IV) Tetrachloride, or Antimony(V) Pentachloride: The Competition between Coordination and Oxidation.

The oxidation of thianthrene and 10-phenylphenothiazine into cation radicals has been examined using redox-active Lewis acids. The reaction of titanium(IV) tetrachloride with thianthrene in toluene produces a solution with an EPR spectrum indicative of oxidation of thianthrene to a cation radical, but the molecular compound (1) (µ-thianthrene)Ti2(µ-Cl2)Cl6 crystallized exclusively. Red crystalline (2) (µ-thianthrene)Ti2(µ-Br2)Br6 formed similarly from titanium(IV) tetrabromide. In contrast, the reaction of antimony(V) pentachloride with thianthrene in toluene yielded crystalline (3) (thianthrene·+)2(Sb2(µ-Cl)2Cl62-)·(SbCl3), while the same reaction in acetonitrile produced crystals of (4) (thianthrene·+)(SbCl6-). The two paramagnetic salts differ in that in (3), the folded (thianthrene·+) cation radicals self-associate, whereas in (4), the (thianthrene·+) cation radicals are isolated from one another and are planar. The reaction of 10-phenylphenothiazine with titanium(IV) tetrachloride in toluene solution resulted in the formation of crystalline paramagnetic (5) (10-phenylphenothiazine·+)(Ti(µ-Cl)3Cl6-) and the reaction of 10-phenylphenothiazine with tin(IV) tetrachloride produced paramagnetic (6) (10-phenylphenothiazine·+)(SnCl5-).

Tb2O@C2(13333)-C74: A Non-Isolated Pentagon Endohedral Fullerene Containing a Nearly Linear Tb-O-Tb Unit.

Terbium has been added to the list of elements that form oxide clusters inside fullerene cages. Tb2O@C2(13333)-C74 has been isolated as a byproduct of the electric arc synthesis of the azafullerene Tb2@C79N. Cocrystallization of Tb2O@C2(13333)-C74 with Ni(OEP) (where OEP is the dianion of octaethylporphyrin) in toluene yielded black needles of Tb2O@C2(13333)-C74·NiII(OEP)·1.5C7H8 that have been examined by single-crystal X-ray diffraction. The resulting structure shows that a nearly linear Tb-O-Tb unit is contained in a C2(13333)-C74, which has two sites where pentagons share an edge to form pentalene units at opposite ends of the fullerene. Unlike the usual situations where metal atoms in fullerenes that do not obey the isolated pentagon rule are situated within the folds of the pentalene units, the Tb atoms in Tb2O@C2(13333)-C74 are positioned to the side of the pentalene units and near-neighboring hexagons. The magnetic properties of Tb2O@C2(13333)-C74 have been examined starting from the experimental geometry, using ab-initio multiconfigurational methods. The computations predict that Tb2O@C2(13333)-C74 will show strong axiality, which would make it a single-molecule magnet with a large magnetic anisotropy barrier.

Direct Crystallization of Diamine Radical Cations: Carbon-Nitrogen Bond Formation from the Reaction of Triphenylamine with TiCl4 , TiBr4 , or SnCl4 versus Carbon-Carbon Bond Formation with SbCl5.

Direct synthesis of diamine radical cations in crystalline form proceeding through oxidation of triphenylamine followed by the formation of a new C-N bond is reported. Although the oxidative coupling of triphenylamine is well studied, diamine products are rarely captured in their radical cation state. The neutral diamine most frequently obtained from this reaction pathway is N,N,N',N'-tetraphenylbenzidine. Herein, the capture of radical cations of diamines in crystalline form in one step starting with neutral triphenylamine was demonstrated, and the formation of two products (the radical cations of N,N,N',N'-tetraphenyl-1,4-benzenediamine or N,N,N',N'-tetraphenylbenzidine) depending on the oxidizing agent used was observed. The radical species are characterized by single-crystal X-Ray diffraction, electron paramagnetic resonance spectroscopy, and optical spectroscopy.

Introduction of a (Ph3P)2Pt group into the rim of an open-cage fullerene by breaking a carbon-carbon bond.

Treatment of an open-cage fullerene, designated as MMK-9, with (Ph3P)4Pt in toluene solution at room temperature allows a (PPh3)2Pt unit to be incorporated into the rim of the cage so that it becomes an integral part of the carbon cage skeleton. The structure of the adduct has been determined by single crystal X-ray diffraction and reveals that the platinum atom has planar PtC2P2 coordination, rather than the usual η2-bonding to an intact C-C double bond of the fullerene.

Isolation and Crystallographic Characterization of Two, Nonisolated Pentagon Endohedral Fullerenes: Ho3 N@C2 (22010)-C78 and Tb3 N@C2 (22010)-C78.

Purified samples of Ho3 N@C2 (22010)-C78 and Tb3 N@C2 (22010)-C78 have been isolated by two distinct processes from the rich array of fullerenes and endohedral fullerenes present in carbon soot from graphite rods doped with Ho2 O3 or Tb4 O7 . Crystallographic analysis of the endohedral fullerenes as cocrystals with Ni(OEP) (in which OEP is the dianion of octaethylporphyrin) shows that both molecules contain the chiral C2 (22010)-C78 cage. This cage does not obey the isolated pentagon rule (IPR) but has two sites where two pentagons share a common C-C bond. These pentalene units bind two of the metal ions, whereas the third metal resides near a hexagon of the cage. Inside the cages, the Ho3 N or Tb3 N unit is planar. Ho3 N@C2 (22010)-C78 and Tb3 N@C2 (22010)-C78 use the same cage previously found for Gd3 N@C2 (22010)-C78 rather than the IPR-obeying cage found in Sc3 N@D3h -C78 .

More crystal field theory in action: the metal-4-picoline (pic)-sulfate [M(pic)x]SO4 complexes (M = Fe, Co, Ni, Cu, Zn, and Cd).

Seven crystal structures of five first-row (Fe, Co, Ni, Cu, and Zn) and one second-row (Cd) transition metal-4-picoline (pic)-sulfate complexes of the form [M(pic)x]SO4 are reported. These complexes are catena-poly[[tetrakis(4-methylpyridine-κN)metal(II)]-µ-sulfato-κ2O:O'], [M(SO4)(C6H7N)4]n, where the metal/M is iron, cobalt, nickel, and cadmium, di-µ-sulfato-κ4O:O-bis[tris(4-methylpyridine-κN)copper(II)], [Cu2(SO4)2(C6H7N)6], catena-poly[[bis(4-methylpyridine-κN)zinc(II)]-µ-sulfato-κ2O:O'], [Zn(SO4)(C6H7N)2]n, and catena-poly[[tris(4-methylpyridine-κN)zinc(II)]-µ-sulfato-κ2O:O'], [Zn(SO4)(C6H7N)3]n. The Fe, Co, Ni, and Cd compounds are isomorphous, displaying polymeric crystal structures with infinite chains of MII ions adopting an octahedral N4O2 coordination environment that involves four picoline ligands and two bridging sulfate anions. The Cu compound features a dimeric crystal structure, with the CuII ions possessing square-pyramidal N3O2 coordination environments that contain three picoline ligands and two bridging sulfate anions. Zinc crystallizes in two forms, one exhibiting a polymeric crystal structure with infinite chains of ZnII ions adopting a tetrahedral N2O2 coordination containing two picoline ligands and two bridging sulfate anions, and the other exhibiting a polymeric crystal structure with infinite chains of ZnII ions adopting a trigonal bipyramidal N3O2 coordination containing three picoline ligands and two bridging sulfate anions. The structures are compared with the analogous pyridine complexes, and the observed coordination environments are examined in relation to crystal field theory.

The crystal structures of iron and cobalt pyridine (py)-sulfates, [Fe(SO4)(py)4] n and [Co3(SO4)3(py)11] n.

The solid-state structures of two metal-pyridine-sulfate compounds, namely catena-poly[[tetra-kis-(pyridine-κN)iron(II)]-µ-sulfato-κ2O:O'], [Fe(SO4)(C5H5N)4] n , (1), and catena-poly[[tetra-kis-(pyridine-κN)cobalt(II)]-µ-sulfato-κ2O:O'-[tetra-kis-(pyridine-κN)cobalt(II)]-µ-sulfato-κ3O,O':O''-[tris-(pyridine-κN)cobalt(II)]-µ-sulfato-κ2O:O'], [Co3(SO4)3(C5H5N)11] n , (2), are reported. The iron compound (1) displays a polymeric structure, with infinite chains of FeII atoms adopting octa-hedral N4O2 coordination environments that involve four pyridine ligands and two bridging sulfate ligands. The cobalt compound (2) displays a polymeric structure, with infinite chains of CoII atoms. Two of the three Co centers have an octa-hedral N4O2 coordination environment that involves four pyridine ligands and two bridging sulfate ligands. The third Co center has an octa-hedral N3O3 coordination environment that involves three pyridine ligands, and two bridging sulfate ligands with one sulfate chelating the cobalt atom.

First-row transition metal-pyridine (py)-sulfate [(py)xM](SO4) complexes (M = Ni, Cu and Zn): crystal field theory in action.

The crystal structures of three first-row transition metal-pyridine-sulfate complexes, namely catena-poly[[tetrakis(pyridine-κN)nickel(II)]-µ-sulfato-κ2O:O'], [Ni(SO4)(C5H5N)4]n, (1), di-µ-sulfato-κ4O:O-bis[tris(pyridine-κN)copper(II)], [Cu2(SO4)2(C5H5N)6], (2), and catena-poly[[tetrakis(pyridine-κN)zinc(II)]-µ-sulfato-κ2O:O'-[bis(pyridine-κN)zinc(II)]-µ-sulfato-κ2O:O'], [Zn2(SO4)2(C5H5N)6]n, (3), are reported. Ni compound (1) displays a polymeric crystal structure, with infinite chains of NiII atoms adopting an octahedral N4O2 coordination environment that involves four pyridine ligands and two bridging sulfate ligands. Cu compound (2) features a dimeric molecular structure, with the CuII atoms possessing square-pyramidal N3O2 coordination environments that contain three pyridine ligands and two bridging sulfate ligands. Zn compound (3) exhibits a polymeric crystal structure of infinite chains, with two alternating zinc coordination environments, i.e. octahedral N4O2 coordination involving four pyridine ligands and two bridging sulfate ligands, and tetrahedral N2O2 coordination containing two pyridine ligands and two bridging sulfate ligands. The observed coordination environments are consistent with those predicted by crystal field theory.

The first-row transition-metal series of tris(ethylenediamine) diacetate complexes [M(en)3](OAc)2 (M is Mn, Fe, Co, Ni, Cu, and Zn).

The crystal structures of the first-row transition-metal series of tris(ethylenediamine-κ2N,N')metal(II) diacetate, [M(C2H8N2)3](CH3CO2)2, with M = Mn, Fe, Co, Ni, Cu, and Zn, are reported. The complexes are all isostructural, crystallizing in a centrosymmetric triclinic cell and possessing an asymmetric unit composed of one [M(en)3]2+ cation and two symmetrically independent acetate anions. In the unit cell, the two complex cations are inversion-generated enantiomers, possessing the energetically favoured Δ(λλλ) and Λ(δδδ) configurations. The complex cations and acetate anions combine through a series of N-H...O hydrogen bonds to generate a three-dimensional network in the crystals. The other notable feature of the series is a significant Jahn-Teller distortion for the d9 Cu2+ complex.