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Heme, as the cofactor and active site of Hb, enables Hb to carry out the necessary function required for O2 management for life, that is, reversible O2 binding for transport. In this paper, the microscopic mechanism of heme-associated poisoning has been elucidated from the perspective of electronic interaction by performing first-principles calculations. The results show that the functional groups (-CHO, -COOH, -NO2, -NH2) and CN exhibit a stronger affinity for heme than O2 and are more likely to occupy the O2 binding site, which results in the loss of the ability of heme to carry O2. Moreover, the addition of functional groups, CO and CN to heme at the side site can cause a pronounced enhancement toward the O2 binding characteristics of heme, which prevents heme from releasing O2 to oxygen-consuming tissues as the blood circulates. The reversible O2 binding function of heme is disrupted by the presence of these toxic ligands in the heme binding pocket, which greatly affects O2 transport in the blood. The inability of tissues to obtain O2 leads to tissue hypoxia, which is the main cause of poisoning. Based on the energy, geometry and electronic properties, the hypoxia mechanism proposed by us coincides well with experiment, and the research has the potential to provide a theoretical reference for the relevant areas of bioscience.

In this paper we study the influence of substituting one CO ligand in [Fe2(CO)6{μ-(SCH2)2(Ph)P=O}] (1) by better σ-donor L ligands affording [Fe2(CO)5(L){μ-(SCH2)2(Ph)P=O}] {L = PPh3 (2) and P(OEt)3 (3)} in relation to the steric interactions and the voltammetric behavior. Cyclic voltammetric investigations under N2 and CO showed remarkable differences in the electrochemical behaviour of complexes 2 and 3: (i) Complex 2 tends to expel PPh3 upon reduction whereas complex 3 exhibits chemical reversibility and (ii) Under CO, complex 3 reacts with CO affording a new compound P, which shows a reversible wave at E1/2 ∼ -0.9 V (vs. ferrocenium/ferrocene couple). The presence of CO assists the formation of 1 after electrochemically induced loss of PPh3 during the voltammetric experiment of 2. Using DFT calculations we provide an explanation for the difference in stabilities between the Fe-PPh3 and Fe-P(OEt)3 bonds.

Simulating protein conformational changes induced or required by the internal diffusion of a ligand is important for the understanding of their interaction mechanisms. Such simulations are challenging for currently available computational methods. In this paper, the problem is formulated as a mechanical disassembly problem where the protein and the ligand are modeled like articulated mechanisms, and an efficient method for computing molecular disassembly paths is described. The method extends recent techniques developed in the framework of robot motion planning. Results illustrating the capacities of the approach are presented on two biologically interesting systems involving ligand-induced conformational changes: lactose permease (LacY), and the beta(2)-adrenergic receptor.

In this paper, the catalytic activities of RuHX(diamine)(PPh(3))(2) complexes with different X ligands (X = NCMe, CO, Cl, OMe, OPh, CCMe and H, corresponding catalytic processes are abbreviated in A, B, C, D, E, F and G systems, respectively) in the H(2)-hydrogenation of ketones were investigated using density functional theory (DFT) method. Calculated results indicate that the rate-determining step in the whole catalytic cycle is hydrogen transfer (HT) for A-E but dihydrogen activation (DA) for F and G. The free energy barriers of the HT step for A-G are 36.1, 32.3, 21.2, 14.9, 21.9, 9.4 and 6.9 kcal mol(-1), respectively. The DA step consists of hydrogen coordination (HC) and hydrogen splitting (HS) steps if dihydrogen coordinates with the Ru center. The transition states (TSs) of H(2) coordinating with the Ru atom for A-G except B are located. The free energy barriers of DA for A-G are 17.8 (17.8, 2.6), 21.5, 12.8 (12.8, 3.8), 12.2 (11.2, 6.2), 13.6 (13.6, 4.1), 17.1 (9.7, 7.5) and 22.0 (10.4, 11.0) kcal mol(-1), respectively (the data in parentheses correspond to the barriers of HC and HS). HT barriers correlate well with the charges of hydride (H) in complex . HC barriers are closely related to the Ru[double bond, length as m-dash]N(1) double bond in , and HS are in line with the proton-moved-distances (PMDs) from to . This study demonstrates that catalysts D, F and G show better catalytic activities than the others, which is in good agreement with experimental results.

This paper reports the synthesis, crystal structures, and magnetic properties of a series of mixed-valence polynuclear manganese complexes bridged by a dianionic 1,2,4-triazole-based ligand L(2-) (H(2)L = 3-(2-phenol)-5-(pyridin-2-yl)-1,2,4-triazole). Complexes 1 to 3 show a similar binuclear structure, with the central core of [Mn(II)Mn(III)(L)(2)] and some other small molecules also coordinated to the two Mn centers. The two [Mn(II)Mn(III)(L)(2)] subunits can be further connected by different dicarboxylic acids to construct non-charged tetranuclear complexes 4 to 7. In these complexes, each deprotonated dianionic ligand L(2-) acts as a mu(2)-bridged ligand to coordinate two Mn centers via the 1,2,4-triazole ring. Bond valence sum (BVS) calculations and Mn surrounding bond lengths indicate that the Mn center coordinated to the pyridine N atoms in the +2 oxidation state, while another Mn center coordinated to the phenolic O atoms is in the +3 oxidation state. The Mn(III) centre shows Jahn-Teller elongation along one of the axes. Magnetic studies show the presence of ferromagnetic Mn(III)-Mn(II) coupling in the binuclear (1-3) and tetranuclear (4-7) complexes with the magnetic coupling constant (J) ranging from 0.58 to 1.17 cm(-1), based on the Hamiltonian H = -2JS(1) x S(2) (S(1) = 5/2 and S(2) = 2). In all cases both z'J' (intermolecular interactions) and D parameter (Zero Field Splitting of the Mn (III) ion) has been introduced to improve the corresponding fit. The relationship of the coupling interaction between the Mn(II)/Mn(III) and their electronic structures is discussed.