Biomedical subjects

H L Ammon

Publications and source records attributed to H L Ammon.

At least 37 records · Page 2Linked to original sources

PubMed1991

Structure of (2'R,5S)-(+/-)-5-(tetrahydro-2'H-pyran-2'-yl)-2(5H)-furanone.

C9H12O3, Mr = 168.2, triclinic, P1, a = 5.5385 (6), b = 8.543 (1), c = 10.373 (1) A, alpha = 113.329 (9), beta = 100.78 (1), gamma = 99.82 (1) degree, V = 426.2 (2) A3, Dx = 1.31 g cm-3, Z = 2, Cu K alpha (lambda = 1.54178 A, graphite monochromator), mu = 8.2 cm-1, F(000) = 180, T = 293 K. Final R = 0.036, wR = 0.081 for 1559 reflections with I greater than 3 sigma(I). The relative configurations at the two chiral centers are (S,R). The dihedral angle between the five- and six-membered rings (O1--C4--C5--O3) is 69.9 (1) degree. The tetrahydropyran is in a chair conformation with the furanone ring equatorial.

Furans↗

PubMed1991

Structure of 1,3-dinitronaphthalene.

C10H6N2O4, Mr = 218.2, triclinic, P1, a = 7.5552 (8), b = 7.763 (1), c = 9.073 (1) A, alpha = 110.742 (9), beta = 99.570 (9), gamma = 100.309 (9) degrees, V = 474.1 (2) A3, D chi = 1.528 g cm-3, Z = 2, Cu K alpha (lambda = 1.54178 A, graphite monochromator) mu = 10.5 cm-1, F(000) = 224, T = 293 K, final R = 0.064, wR = 0.092 for 1213 reflections with I greater than 3 sigma (I). The naphthalene ring is planar with an average deviation of 0.004 A from the ten-atom least-squares plane. The C-C distances show the typical naphthalene alternation: C1-C2, C3-C4, C5-C6 and C7-C8 average 1.359 A; C2-C3 and C6-C7 average 1.391 A. The C1 nitro group is twisted out of the ring plane by approximately 37 degrees to relieve non-bonded interactions between an oxygen and the C8-H8 region.

Chemical Phenomena↗

PubMed1991

Structure of 1,5,9-trinitrobishomopentaprismane.

2,3,8-Trinitrohexacyclo[5.4.1.0(2,6).0(3,10).-0(4,8).0(9,12)]do dec ane (IV), C12H11N3O6, Mr = 293.2, orthorhombic, Pna2(1), a = 11.467 (1), b = 8.756 (1), c = 11.9339 (8) A, V = 1198.2 (4) A3, Dx = 1.625 g cm-3, Z = 4, Cu K alpha, lambda = 1.54178 A, mu = 11.6 cm-1, F(000) = 608, T = 293 K, final R = 0.061, wR = 0.091 for 1082 reflections with I greater than 3 sigma(I). There are no unusual intermolecular distances and the crystal packing is normal. The crystal density of (IV) is only 2.3% larger than that of 1,5-dinitrobishomopentaprismane (III) at 1.589 g cm-3 despite a 6.7% higher molecular density of (IV) over (III). An analysis of crystal packing and the calculated crystal packing coefficients indicates that the small crystal-density change is the result of more efficient molecular packing in (III) over (IV), which compensates for the lower molecular density of (III). The molecular shape and polarity of (III) lead to efficient crystal packing.

Chemical Phenomena↗

PubMed1991

Structure of 9-nitro-[4]peristylane-1,5-dione.

Decahydro-1,6:3,4-dimethano-3a-nitrocyclobuta [1,2:3,4]dicyclopentene-2,5-dione (II), C12-H11NO4, Mr = 233.2, monoclinic, P2(1)/n, a = 13.378 (7), b = 6.614 (1), c = 23.040 (15) A, beta = 92.53 (5) degrees, V = 2036.6 (4) A3, Z = 8, D chi = 1.521 g cm-3, Cu K alpha, lambda = 1.54178 A, mu = 9.3 cm-1, F(000) = 1312, T = 293 K, final R = 0.047, wR = 0.075 for 3075 reflections with I greater than 3 sigma(I). There are no unusually short intermolecular distances. A comparison of the molecular densities and packing coefficients of (I) [4]peristylane-1,5-dione with (II), indicates that the change in crystal density from (I) (1.415 g cm-3) to (II) (1.521 g cm-3) is the sole result of an increase in molecular density with NO2 substitution. The packing coefficients for (I) and (II) are identical.

Bridged-Ring Compounds↗

PubMed1991

Structure of thialysine hydrochloride.

2-Ammonio-3-[(2-ammonioethyl)thio]propionate chloride, C5H13N2O2S+.Cl-, Mr = 200.7, monoclinic, P2(1), a = 5.1275 (4), b = 7.897 (1), c = 11.208 (1) A, beta = 104.129 (8) degrees, V = 440.1 A3, Z = 2, Dx = 1.519 g cm-3, Mo K alpha, lambda = 0.71069 A, mu = 6.12 cm-1, F(000) = 212, T = 295 K, final R = 0.021, wR = 0.027 for 784 reflections with I greater than 3 sigma (I). The two ammonium cations form seven hydrogen bonds: alpha-NH3+ acts as a donor for three carboxylate O atoms and one Cl- ion whereas epsilon-NH3+ is linked to three Cl- ions.

Cysteine↗

PubMed1991

Structure of 3-methyl-1,2,3,4,5,6-hexahydro-1,6-methano-3-benzazocinium hydrogen oxalate.

C13H18N+.C2HO4-, Mr = 277.3, orthorhombic, P2(1)2(1)2(1), a = 5.752 (1), b = 15.502 (2), c = 15.910 (2) A, V = 1418.6 (6) A3, Z = 4, Dx = 1.298 g cm-3, Mo K alpha (lambda = 0.71069 A), mu = 1.01 cm-1, F(000) = 592, T = 295 K. Final R = 0.035, wR = 0.042 for 1003 reflections with I greater than 3 sigma(I). The compound is an ammonium hydrogen oxalate. Both O atoms of the ionized carboxyl group act as acceptors in the formation of two hydrogen bonds: (a) an N--H...O bond linking the cation and anion with N...O and H...O distances of 2.722 (4) and 1.78 (5) A and (b) a strong O--H...O bond linking a chain of oxalate ions along a with O...O and H...O distances of 2.578 (4) and 1.59 (6) A. The relative stereochemistry of the heterocyclic and aromatic rings in the cation is similar to that in morphine.

Analgesics, Opioid↗

PubMed1991

Structure of a photoresponsive crown ether, 21-(4'-methoxyphenylazo)-1,4,7,14,23-pentaoxa[7.2.2] orthometaorthobenzenophane.

3,10,13,16,23-Pentaoxatetracyclo-[23.3.1.0.(4,9)0(17,22)]nonaco sa-1(29), 4,6,8,17,19,21,25,27-nonaene-29-azo-(4'-methoxybenzene), C31H30N2O6, Mr = 526, monoclinic, P2(1)/n, a = 14.564 (3), b = 19.177 (2), c = 10.025 (2) A, beta = 100.42 (1) degrees, V = 2754 (1) A3, Z = 4, Dx = 1.269 g cm-3, Mo K alpha, lambda = 0.71069 A, mu = 0.95 cm-1, F(000) = 1112, T = 293 K, final R = 0.050 for 2577 reflections with I greater than 3 sigma(I). The molecule resembles a butterfly with benzene rings for the wings and head. The transazobenzene moiety, which overlays one face of the crown oxygen ring, is in an orientation that creates a partial steric block to cation...crown complex formation.

Ethers, Cyclic↗

PubMed1990

Structure of N',N'-dibenzylbenzohydrazide.

C21H20N2O, Mr = 316.4, monoclinic, P2(1)/c, a = 9.985 (2), b = 17.070 (3), c = 10.119 (2) A, beta = 95.99 (1) degree, V = 1715.3 A3, Z = 4, Dx = 1.225 g cm-3, Mo K alpha (lambda = 0.71069 A), mu = 0.82 cm-1, F(000) = 672, T = 295 K. Final R = 0.043, wR = 0.042 for 1139 reflections with I greater than 3 sigma(I). There is one hydrogen bond in the structure with N-H...O = 2.05 (4) and N...O = 2.923 (5) A.

Benzoates↗

PubMed1990

Structure of 1,4-cubanediyldiammonium bis(trinitromethanide).

C8H12N2+.2CN3O6-, Mr = 436.27, monoclinic, C2/m, a = 14.298 (2), b = 8.408 (1), c = 7.354 (2) A, beta = 103.42 (2) degrees, V = 859.9 (5) A3, Z = 2, Dx = 1.68 g cm-3, lambda(Mo K alpha) = 0.71069 A (graphite monochromator), mu = 1.66 cm-1, F(000) = 448, T = 293 K, final R = 0.039 for 672 reflections with I greater than or equal to 3 sigma(I). The cubanediyldiammonium cation and trinitromethanide anion have 2/m and m crystallographic symmetries, respectively. The cation is linked to six trinitromethanide anions, three at each end, by a total of 12 N--H...O hydrogen bonds through the six cation H atoms. The cubane cage has a local threefold axis of symmetry along the long axis (N1...N1) of the cation and undergoes a large librational motion, 17 degrees r.m.s. amplitude, about this axis.

Bridged-Ring Compounds↗

PubMed1990

Structure of 5-hydroxy-5-phenyl-7-azatricyclo[7.4.0.02,7]trideca-2,9(1), 10,12-tetraen-8-one by the consistent electron density approach.

C18H15NO2, Mr = 277.3, monoclinic, P21/n, a = 7.408 (2), b = 22.311 (7), c = 8.613 (2) A, beta = 103.53 (3) degrees, V = 1384 (1) A3, Z = 4, Dx = 1.33 g cm-3, lambda(Mo K alpha) = 0.71069 A, mu = 0.94 cm-1, F(000) = 594, T = 293 K, 2229 unique diffractometer data, 963 with I greater than 3 sigma(I), R = 0.050. Structure solution was by the consistent electron density approach which combines the concepts of the OMIT map and density modification procedures. The benzolactam portion of the molecule is highly planar; most bond lengths and angles have typical values.

Bridged-Ring Compounds↗

PubMed1990

Structure of N,N,N',N'-tetrakis(2-fluoro-2,2-dinitroethyl)oxamide by the consistent electron density approach.

C10H8F4N10O18, Mr = 632.22, monoclinic, Pc, a = 7.8885 (6), b = 6.7787 (4), c = 21.595 (2) A, beta = 108.21 (1) degree, V = 1096 (1) A3, Z = 2, Dx = 1.914 g cm-3, lambda(Cu K alpha) = 1.5418 A, mu = 18.7 cm-1, F(000) = 636, T = 293 K, 1791 unique data, 1733 with I greater than 3 sigma (I), R = 0.047. The structure was solved by the consistent electron density approach (CEDA), in which a small starting set of random phases was refined and expanded by the application of restraints to the electron density. A refinable preliminary structure was obtained by fitting a model to a 3 A map, calculated with 27 reflections (all data with d greater than 3 A, and magnitude of Fo greater than 170) whose phases had been determined by the CEDA. The molecule has an extended, open conformation; the two pairs of fluorodinitroethyl substituents located across the molecular center from each other show i and C2 pseudo-symmetry respectively.

Amino Acids↗

PubMed1989

Formation of the 1-(S-glutathionyl)-2,4,6-trinitrocyclohexadienate anion at the active site of glutathione S-transferase: evidence for enzymic stabilization of sigma-complex intermediates in nucleophilic aromatic substitution reactions.

Formation of the Meisenheimer complex or sigma-complex [1-(S-glutathionyl)-2,4,6-trinitrocyclohexadienate] between glutathione (GSH) and 1,3,5-trinitrobenzene (TNB) can be observed at the active sites of isoenzymes 3-3 and 4-4 of rat liver GSH transferase. The spectroscopic properties (UV-visible and CD) of the enzyme-bound sigma-complex are consistent with a 1:1 complex in an asymmetric environment. Competitive inhibitors which occupy the GSH binding site (e.g., gamma-L-glutamyl-D,L-2-aminomalonylglycine) inhibit sigma-complex formation. The apparent formation constants of the sigma-complex (M) with enzyme-bound GSH (E.GS- + TNB in equilibrium E.M) at pH 7.5 are 5 x 10(4) M-1 and 7 x 10(2) M-1 for isoenzymes 3-3 and 4-4, respectively. Both values are much greater than that in aqueous solution (GS- + TNB in equilibrium M), where Kf = 28 M-1. Isoenzyme 3-3 is roughly an order of magnitude more efficient than 4-4 in catalyzing nucleophilic aromatic substitutions, a fact that appears to correlate with the ability of each enzyme to stabilize the sigma-complex. The pH dependence of Kf(app) for isoenzyme 3-3 is used to probe the ionization behavior of enzyme-bound GSH. The results are consistent with a double-ionization scheme (e.g., H+E.GSH in equilibrium H+E.GS- in equilibrium E.GS-) with pK's of 5.7 and 7.6, which are assigned to the thiol pK and the pK of a protonated base in the active site, respectively. Formation of the sigma-complex is also observed in single crystals of isoenzyme 3-3, providing a clear demonstration of the chemical competence of the crystallized enzyme. The results are discussed with respect to catalytic efficiency and the ability of the enzyme to stabilize sigma-complex intermediates in nucleophilic aromatic substitution reactions.

Animals↗

PubMed1989

Structure of (+-)-threo-9,10,16-trihydroxypalmitic acid.

9,10,16-Trihydroxyhexadecanoic acid, C16H32O5, Mr = 304.4, triclinic, P1, a = 4.871 (1), b = 8.801 (1), c = 21.121 (2) alpha = 89.54 (1), beta = 84.88 (2), gamma = 76.35 (2) degrees, V = 876.14 (4) A3, Z = 2, Dx = 1.154 g cm-3, Mo K alpha, lambda = 0.71069 A, mu = 0.26 cm-1, F(000) = 336, T = 295 K. Final R = 0.055 for 1556 reflections with I greater than or equal to 3 sigma(I). The 16 C atoms form an all-trans zigzag chain. Each molecule is linked to seven neighboring molecules via eight possible hydrogen bonds with O...O distances varying from 2.591 (6) to 2.673 (3) A. Each carboxyl group is potentially hydrogen-bonded to the carboxyl and C16-OH groups of other molecules with O...O distances of 2.591 (6) and 2.644 (4) A. The conformation around the C9-C10 bond is gauche with an O3-C9-C10-O4 torsion angle of 66.4 (5) degrees.

Chemical Phenomena↗

PubMed1988

Structures of amidohydrolases. Amino acid sequence of a glutaminase-asparaginase from Acinetobacter glutaminasificans and preliminary crystallographic data for an asparaginase from Erwinia chrysanthemi.

The complete amino acid sequence of a glutaminase-asparaginase from Acinetobacter glutaminasificans, for which a preliminary tertiary structure is available from crystallographic analysis, has been determined by automated Edman degradation of fragments produced by chemical and proteolytic cleavages. The protein consists of 331 amino acid residues and has a molecular weight of 35,500. The pattern of hydrophilic and hydrophobic regions is typical of a globular protein. A new crystal form of an Erwinia chrysanthemi 1125 asparaginase is reported. The space group is monoclinic C2, with unit cell parameters of: a = 107.8, b = 91.7, c = 129.2 A and beta = 91.7 degrees. A Vm of 2.25 A3/dalton was calculated for one tetramer of 35,100-dalton subunits per asymmetric unit. X-ray intensity data have been obtained to 2.2 A resolution. The point group symmetry of the Er. chrysanthemi tetramer is 222 from self-rotation function calculations. The relative orientations of an A. glutaminasificans glutaminase-asparaginase model and the Er. chrysanthemi asparaginase tetramer have been determined with the cross-rotation function, and translation function calculations have revealed a plausible location for the asparaginase tetramer in the crystal.

Acinetobacter↗

PubMed1988

Preliminary crystal structure of Acinetobacter glutaminasificans glutaminase-asparaginase.

The preliminary structure of a glutaminase-asparaginase from Acinetobacter glutaminasificans is reported. The structure was determined at 3.0-A resolution with a combination of phase information from multiple isomorphous replacement at 4-5-A resolution and phase improvement and extension by two density modification techniques. The electron density map was fitted by a polypeptide chain that was initially polyalanine. This was subsequently replaced by a polypeptide with an amino acid sequence in agreement with the sizes and shapes of the side chain electron densities. The crystallographic R factor is 0.300 following restrained least squares refinement with data to 2.9-A resolution. The A. glutaminasificans glutaminase-asparaginase subunit folds into two domains: the aminoterminal domain contains a five-stranded beta sheet surrounded by five alpha helices, while the carboxyl-terminal domain contains three alpha helices and less regular structure. The connectivity is not fully determined at present, due in part to the lack of a complete amino acid sequence. The A. glutaminasificans glutaminase-asparaginase structure has been used successfully to determine the relative orientations of the molecules in crystals of Pseudomonas 7A glutaminase-asparaginase, in crystals of Vibrio succinogenes asparaginase, and in a new crystal form of Escherichia coli asparaginase (space group 1222, one subunit per asymmetric unit).

Acinetobacter↗

PubMed1987

Crystallization and a preliminary X-ray diffraction study of isozyme 3-3 of glutathione S-transferase from rat liver.

Crystals of the homodimeric isozyme 3-3 of glutathione S-transferase from rat liver have been obtained with the hanging drop method of vapor diffusion from ammonium sulfate solutions. The successful crystallization of the enzyme required the presence of both the enzyme inhibitor (9R, 10R)-9, 10-dihydro-9-(S-glutathionyl)-10-hydroxyphenanthrene and the detergent beta-octylglucopyranoside. The crystals belong to the monoclinic space group C2, with cell dimensions of a = 88.24(8) A, b = 69.44(4) A, c = 81.28(5) A, beta = 106.01(6) degrees, and contain four dimeric enzyme molecules per unit cell. The crystals diffract to at least 2.2 A and are suitable for X-ray crystallographic structure determination at high resolution.

Animals↗

PubMed1987

Role of the (acyloxy)methyl moiety in eliciting the adrenergic beta-blocking activity of 3-(acyloxy)propanolamines.

Some totally aliphatic 3-(acyloxy)propanolamines were synthesized with the aim of testing whether beta-blocking activity could be obtained from this class of drugs, even in the absence of an aromatic group. The significant and, in most cases, competitive beta-blocking activity shown by the compounds under examination, together with the results of a theoretical study in which their reactivity was compared with that of other adrenergic beta-blocking drugs, seems to confirm a hypothesis previously advanced on the basis of knowledge about the action mechanism of adrenergic beta-blocking drugs and of the results of structural studies. It was also possible to suggest some considerations about the role played by the (acyloxy)methyl portion of 3-(acyloxy)propanolamines in eliciting their adrenergic beta-blocking activity.

Adrenergic beta-Agonists↗

PubMed1985

Preliminary crystallographic study of an L-asparaginase from Vibrio succinogenes.

Crystals of an L-asparaginase from Vibrio succinogenes were obtained with the hanging drop method from ammonium sulphate-containing solutions. The crystals belong to the orthorhombic space group P22(1)2(1) with unit cell dimensions of a = 71.3 A, b = 85.8 A, c = 114.0 A, and contain two tetrameric enzyme molecules per unit cell. There are two subunits in the asymmetric unit; a molecular dyad is coincident with the crystallographic dyad. The crystal lattice is similar to that reported for an Escherichia coli asparaginase. Rotation function calculations have revealed that the V. succinogenes enzyme has 222 point group symmetry in the crystal. The second and third molecular dyads differ, however, from the corresponding E. coli asparaginase dyads by approximately 40 degrees. The crystals diffract to at least 2.2 A resolution and are suitable for X-ray crystallographic structure determination.

Asparaginase↗