Solution NMR determination of the seating(s) of meso-nitro-etioheme-1 in myoglobin: implications for steric constraints to meso position access in heme degradation by coupled oxidation.

The highly stereoselective cleavage of hemin in myoglobin by coupled oxidation has been attributed to steric barriers that leave more space near the alpha- than the other meso-positions. The steric barriers near meso positions in myoglobin have been investigated by establishing the thermodynamics and dynamics of possible seatings in the pocket of horse myoglobin of a four-fold symmetric etioheme I modified with a bulky nitro group at a single meso position. The cyanomet complex of this reconstituted myoglobin exhibits three sets of (1)H NMR resonances that are linked dynamically and occur in approximate populations ratios of 0.

Alteration of the aurophilic interactions in trimeric gold(I) compounds through charge transfer. Behavior of solvoluminescent Au(3)(MeN=COMe)(3) in the presence of electron acceptors.

The ability of the triangular gold(I) complex, Au(3)(MeN=COMe)(3), which as a solid displays the novel property of solvoluminescence (see: Vickery, J. C.; Olmstead, M.

A mixed oxidation state, binuclear iron complex containing an unsymmetrically coordinating ligand. A ligand-induced switch in redox behavior.

Binuclear [FeIIFeIII(BMDP)(O2CPh)3](BF4) (1) was obtained by treating an acetonitrile solution of the fully reduced [FeIIFeII(BMDP)(O2CPh)(MeOH)1.5(H2O)0.5](BF4)2 with 5 equiv of benzoate and then exposing the mixture to oxygen.

Solution 1H NMR investigation of the seating and rotational "hopping" of centrosymmetric etioheme-I in myoglobin: effect of globin origin and its oxidation/spin state on heme dynamics.

Solution 1H NMR spectroscopy was used to investigate the heme active-site structure and dynamics of rotation about the Fe-His bond of centrosymmetric etioheme-I reconstituted into sperm whale and horse myoglobin (Mb). Comparison of the NOESY cross-peak pattern and paramagnetic relaxation properties of the cyanomet complexes confirm a heme pocket that is essentially the same as Mb with either native protoheme or etioheme-I. Dipolar contacts between etioheme and the conserved heme pocket residues establish a unique seating of etioheme that conserves the orientation of the N-Fe-N vector relative to the axial His plane, with ethyl groups occupying the vinyl positions of protoheme.

Electronic interactions in a new fullerene dimer: C(122)H(4), with two methylene bridges.

The isolation of a new fullerene dimer, C(122)H(4), and its structural characterization by (13)C NMR and (1)H NMR spectroscopy and by UV/vis and IR spectroscopy are reported. The structure of this dimer consists of two fullerene cages, which are directly connected through two C-C bonds and two methylene bridges. Consequently, adjacent hexagonal faces of the two fullerene cages are arranged in a face to face manner.

Tetrapyrroles as pi Donors: A Pd(2)(2+) Unit Sandwiched between Two Helical Bilindione-Palladium Moieties.

Metalation of octaethylbilindione (H(3)OEB) with palladium(II) acetate produces the novel tetranuclear complex [Pd(4)(OEB)(2)] in which a (Pd(I)(2))(2+) unit is sandwiched between two helical Pd(OEB) units (see picture). Treatment of [Pd(4)(OEB)(2)] with pyridine/ethanol gives the odd-electron helical complex [Pd(OEB)].

The duration of measuring partial AUCs for the assessment of bioequivalence.

Purpose: To determine favourable sampling conditions for assessing bioequivalence by the comparison of partial AUCs in the early phase of concentration-time profiles.

Methods: Two-period crossover trials were simulated. They assumed a wide range of the ratios of absorption rate constants of the test (T) and reference (R) formulations (kaT/kaR).

Nickel complexes of 21-oxaporphyrin and 21, 23-dioxaporphyrin.

The nickel(I) and nickel(II) complexes of 5,20-bis(p-tolyl)-10, 15-diphenyl-21-oxaporphyrin (ODTDPPH) and 5,10,15,20-tetraphenyl-21, 23-dioxaporphyrin (O2 TPP) have been investigated. These oxa analogues of 5,10,15,20-tetraarylporphyrin, where one or two pyrrole rings are replaced by a furan moiety, have been synthesized by condensation of the respective precursors, namely 2,5-bis(arylhydroxymethyl)furan, pyrrole, and arylaldehyde. Insertion of nickel(II) into ODTDPPH or O2 TPP yielded high-spin five- and six-coordinate ([(ODTDPP)Ni(II) Cl] and [(O2 TPP)NiIICl2 ]) complexes, which can be reduced with moderate reducing reagents.

Structural and Spectroscopic Characterization of Iron(III) Dioxoporphodimethene Complexes and Their Autoreduction to an Iron(II) Complex in Pyridine.

Three iron complexes of the meso-dioxo derivative of octaethylporphryin (trans-H(2)OEPO(2)) were characterized by X-ray diffraction. Green ClFe(III)(trans-OEPO(2)).1.

Evaluation of reverse transcriptase and protease inhibitors in two-drug combinations against human immunodeficiency virus replication.

Current treatments for human immunodeficiency virus (HIV) include both reverse transcriptase and protease inhibitors. Results from in vitro and clinical studies suggest that combination therapy can be more effective than single drugs in reducing viral burden. To evaluate compounds for combination therapy, stavudine (d4T), didanosine (ddI), or BMS-186,318, an HIV protease inhibitor, were combined with other clinically relevant compounds and tested in a T-cell line (CEM-SS) that was infected with HIV-RF or in peripheral blood mononuclear cells infected with a clinical HIV isolate.

Optical and ODMR Studies of Luminescent Halo(dimethylphenylphosphine)gold(I) Crystals.

Crystals of {(Me(2)PhP)AuX}(n) (Me = methyl; Ph = phenyl; X = Cl, Br, I; n = 2, 3) show emission from two excited states. Both states are assigned a triplet multiplicity, on the basis of their lifetimes and zero-field splittings. The structured, higher energy emission originates at approximately 360 nm and has the greater relative intensity at low temperatures.

Solid State Structures and Gold-Gold Bonding in Luminescent Halo(dimethylphenylphosphine)gold(I) Complexes.

The structures of the series of two-coordinate gold(I) complexes {(Me(2)PhP)AuX}(n) where X is Cl, Br, or I have been examined by X-ray diffraction. The chloro complex crystallized in two separate polymorphic forms. Colorless hexagonal blocks of {(Me(2)PhP)AuCl}(3) crystallized in the monoclinic space group P2(1)/m with a = 12.

Developing Reagents To Orient Fullerene Derivatives. Formation and Structural Characterization of (eta(2)-C(60)O)Ir(CO)Cl(As(C(6)H(5))(3))(2).

In order to obtain crystals of fullerene oxides that are suitable for single-crystal X-ray diffraction, the reactions between C(60)O and Vaska type iridium complexes have been examined. While reaction with Ir(CO)Cl(P(C(6)H(5))(3))(2)(and with triphenylphosphine but not triphenylarsine) results in partial deoxygenation of the fullerene epoxide, reaction with Ir(CO)Cl(As(C(6)H(5))(3))(2)()()produces crystalline (eta(2)-C(60)O)Ir(CO)Cl(AsPh(3))(2).4.

A new approach to the limiting dilution assay.

Improved methods of human immunodeficiency virus isolation have sparked an increased interest in determination of the number and proportion of infected cells in plasma samples. The limiting dilution assay is a popular method of determining the proportion of infected cells. We propose a new estimator of the proportion of infected cells based on an underlying Markov chain model for the progression of infected cells to further flasks in the series.

Short forms of the "reference-" and "working-memory" Morris water maze for assessing age-related deficits.

Short forms of the reference- and working-memory versions of the Morris water maze, each limited to 10 trials, were examined for their reliability and sensitivity to age-related deficits in 16- and 24-month F-344 rats, relative to 2- to 2.5-month young controls. The reference-memory task used long intertrial intervals of 23 h, but required learning only one target location, while the working-memory task used shorter intertrial intervals of 60 min but required learning many different target locations.

Proton NMR study of the influence of heme vinyl groups on the formation of the isomeric forms of sulfmyoglobin.

The formation of sulfmyoglobin has been investigated for myoglobin reconstituted with hemins having vinyls replaced by hydrogens to determine the participation of the vinyl groups in the reaction processes. Green complexes are produced in all cases, proving that vinyls are not obligatory for the formation of sulfproteins. In the presence of the 4-vinyl group, the 1H NMR spectra of the met-cyano derivatives indicate the formation of three green species; however, the most stable of these products is not formed in the absence of this group, confirming reaction of the 4-vinyl in this species.

Multiple forms of sulfmyoglobin as detected by 1H nuclear magnetic resonance spectroscopy.

The proton nuclear magnetic resonance spectrum of sulfmyoglobin prepared in standard fashion reveals the presence of three forms, A, B, and C, with different chemical reactivity. Conditions for some interconversions of these forms are given. The 1H NMR spectra of the different forms show similar patterns.

X-ray absorption spectroscopic studies of high valent iron porphyrins. Horseradish peroxidase compounds I and II and synthetic models.

X-ray absorption edge and extended x-ray absorption fine structure studies have been undertaken on resting (ferric) horseradish peroxidase, HRP compound I (HRP-I), HRP compound II (HRP-II), and several highly oxidized synthetic iron porphyrins that may have relevance as models for the iron site in horseradish peroxidase. The energies of the absorption edges are consistent with an Fe(IV) formulation for the highly oxidized species. The shapes of the absorption edges further support the assignment of HRP-I and one of the model compounds as Fe(IV)-porphyrin pi-cations.