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The dicopper(II) complex with the ligand N,N,N',N',N"-pentakis[(1-methyl-2-benzimidazolyl)methyl]dipropylenetriamine (LB5) has been synthesized and structurally characterized. The small size and the quality of the single crystal required that data be collected using synchrotron radiation at 276 K. [Cu(2)(LB5)(H(2)O)(2)][ClO(4)](4): platelet shaped, P&onemacr;, a = 11.028 Å, b = 17.915 Å, c = 20.745 Å, alpha = 107.44 degrees, beta = 101.56 degrees, gamma = 104.89 degrees, V = 3603.7 Å(3), Z = 2; number of unique data, I >/= 2sigma(I) = 3447; number of refined parameters = 428; R = 0.12. The ligand binds the two coppers nonsymmetrically; Cu1 is coordinated through five N donors and Cu2 through the remaining three N donors, while two water molecules complete the coordination sphere. Cu1 has distorted TBP geometry, while Cu2 has distorted SP geometry. Voltammetric experiments show quasireversible reductions at the two copper centers, with redox potential higher for the CuN(3) center (0.40 V) and lower for the CuN(5) center (0.17 V). The complex binds azide in the terminal mode at the CuN(3) center with affinity lower than that exhibited by related dinuclear polyaminobenzimidazole complexes where this ligand is bound in the bridging mode. The catechol oxidase activity of [Cu(2)(LB5)](4+) has been examined in comparison with that exhibited by [Cu(2)(L-55)](4+) (L-55 = alpha,alpha'-bis{bis[(1-methyl-2-benzimidazolyl)methyl]amino}-m-xylene) and [Cu(2)(L-66)](4+) (L-66 = alpha,alpha'-bis{bis[2-(1-methyl-2-benzimidazolyl)ethyl]amino}-m-xylene) by studying the catalytic oxidation of 3,5-di-tert-butylcatechol in methanol/aqueous buffer pH 5.1. Kinetic experiments show that [Cu(2)(L-55)](4+) is the most efficient catalyst (rate constant 140 M(-1) s(-1)), followed by [Cu(2)(LB5)](4+) (60 M(-1) s(-1)), in this oxidation, while [Cu(2)(L-66)](4+) undergoes an extremely fast stoichiometric phase followed by a slow and substrate-concentration-independent catalytic phase. The catalytic activity of [Cu(2)(L-66)](4+), however, is strongly promoted by hydrogen peroxide, because this oxidant allows a fast reoxidation of the dicopper(I) complex during turnover. The activity of [Cu(2)(LB5)](4+) is also promoted by hydrogen peroxide, while that of [Cu(2)(L-55)](4+) is little affected. The phenol monooxygenase activity of [Cu(2)(LB5)](2+) has been compared with that of [Cu(2)(L-55)](2+) and [Cu(2)(L-66)](2+) by studying the ortho hydroxylation of methyl 4-hydroxybenzoate to give methyl 3,4-dihydroxybenzoate. The LB5 complex is much more selective than the other complexes since its reaction produces only catechol, while the main product obtained with the other complexes is an addition product containing a phenol residue condensed at ring position 2 of the catechol.

To establish the competence of the active site of hemocyanin to acquire diverse coordination geometries, the binding of azide to three forms of a crab hemocyanin, the dinuclear cupric or met-hemocyanin, the mononuclear cupric or met-apo-hemocyanin, and the mononuclear Co(II)-substituted derivative has been studied by near-ultraviolet circular dichroism and EPR spectroscopies. The near-ultraviolet circular dichroism spectra of the various derivatives present qualitatively similar features, namely a negative peak around 335 nm in the case of the two copper-containing derivatives and a three-component pattern with the Co(II) derivative. Upon decreasing the pH from 7.0 to 5.5 a decrease of optical activity is observed with all protein samples. The characteristic CD features, attributable to N(imidazole)-to-metal and to OH -to-metal charge-transfer transitions, are strongly affected by azide binding. In particular, the intensity of the negative band exhibited by the two copper-containing protein forms decreases with the onset of a new negative feature with maximum around 400 nm diagnostic for azide-to-Cu(II) charge-transfer transitions. The visible region is affected as well, indicating that changes in the coordination sphere of copper take place. The affinity for azide of the different protein forms is higher at low pH. EPR measurements on the paramagnetic met-apo-hemocyanin derivative as a function of pH demonstrate heterogeneity in the coordination environment at low pH. In the presence of azide an increase of rhombic distortion of the EPR spectra is observed and on the basis of the identified sets of copper hyperfine features in the course of azide titration experiments two different azide bound forms of met-apo-hemocyanin can be detected. The CD and EPR data at the different pH values are consistent with a reaction scheme in which azide replaces a fourth ligand in the metal-coordination sphere, identified as a water or hydroxide molecule.

Competitive inhibition by phenolic compounds of the ascorbic acid oxidation reaction catalyzed by ascorbate oxidase was investigated at pH 7.0 and 23.0 degrees C. Inhibition of p-nitrophenol is pH dependent over the range 5.0-8.0, with inhibitor binding favored at higher pH. Bulky substituents on the phenol nucleus reduce or prevent the inhibitory effect. The presence of phenol affects the binding characteristics of azide to the trinuclear cluster of the enzyme. In particular, binding of azide to type 2 copper is prevented, and the affinity of azide to type 3 copper is reduced. In addition, reduction of type 1 copper is observed upon prolonged incubation of ascorbate oxidase with excess phenol and azide, but not with phenol alone. It is proposed that binding of phenolic inhibitors occurs at or near the site where the substrate (ascorbate) binds. NMR relaxation measurements of the protons of phenols in the presence of ascorbate oxidase show paramagnetic effects due to the proximity of the bound inhibitor to a copper center, likely type 1 copper. Copper-proton distance estimates between this paramagnetic center and p-cresol or p-nitrophenol bound to ascorbate oxidase are between 4.4 and 5.9 A.

The lactoperoxidase (LPO)-catalyzed oxidation of p-phenols by hydrogen peroxide has been studied. The behavior of the enzyme differs from that of other peroxidases in this reaction. In particular LPO shows several catalytic intermediates during the catalytic cycle because of its capability to delocalize an oxidizing equivalent on a protein amino acid residue. In the phenol oxidation the enzyme Compound I species, containing an iron-oxo and a protein radical, uses the iron-oxo group at acidic pH and the protein radical in neutral or basic medium. Kinetic and spectroscopic studies indicate that the ionization state of an amino acid residue with pKa 5.8 +/- 0.2, probably the distal histidine, controls the enzyme intermediate forms at different pH. LPO undergoes inactivation during the oxidation of phenols. The inactivation is reversible and depends on the easy formation of Compound III even at low oxidant concentration. The inactivation is due to the substrate redox potential since the best substrate is that with lowest redox potential, while the worst substrate has the highest potential. This strongly indicates that Compound II, formed during catalytic turnover, has a low redox potential, making easier its oxidation by hydrogen peroxide to Compound III. The dependence of LPO activity on the phenols redox potential suggests that the protein radical where an oxidizing equivalent can be localized is a tyrosyl residue.

The copper(I) and copper(II) complexes with the nitrogen donor ligands bis[(1-methylbenzimidazol-2-yl)methyl]amine (1-BB), bis[2-(1-methylbenzimidazol-2-yl)ethyl]amine (2-BB), N-acetyl-2-BB (AcBB), and tris[2-(1-methylbenzimidazol-2-yl)ethyl]nitromethane (TB) have been studied as models for copper nitrite reductase. The copper(II) complexes form adducts with nitrite and azide that have been isolated and characterized. The Cu(II)-(1-BB) and Cu(II)-AcBB complexes are basically four-coordinated with weak axial interaction by solvent or counterion molecules, whereas the Cu(II)-(2-BB) and Cu(II)-TB complexes prefer to assume five-coordinate structures. A series of solid state structures of Cu(II)-(1-BB) and -(2-BB) complexes have been determined. [Cu(1-BB)(DMSO-O)(2)](ClO(4))(2): triclinic, P&onemacr; (No. 2), a = 9.400(1) Å, b = 10.494(2) Å, c = 16.760(2) Å, alpha = 96.67(1) degrees, beta = 97.10(1) degrees, gamma = 108.45(1) degrees, V = 1534.8(5) Å(3), Z = 2, number of unique data [I >/= 3sigma(I)] = 4438, number of refined parameters = 388, R = 0.058. [Cu(1-BB)(DMSO-O)(2)](BF(4))(2): triclinic, P&onemacr; (No. 2), a = 9.304(5) Å, b = 10.428(4) Å, c = 16.834(8) Å, alpha = 96.85(3) degrees, beta = 97.25(3) degrees, gamma = 108.21(2) degrees, V = 1517(1) Å(3), Z = 2, number of unique data [I >/= 2sigma(I)] = 3388, number of refined parameters = 397, R = 0.075. [Cu(1-BB)(DMSO-O)(NO(2))](ClO(4)): triclinic, P&onemacr; (No. 2), a = 7.533(2) Å, b = 8.936(1) Å, c = 19.168(2) Å, alpha = 97.66(1) degrees, beta = 98.62(1) degrees, gamma = 101.06(1) degrees, V = 1234.4(7) Å(3), Z = 2, number of unique data [I >/= 2sigma(I)] = 3426, number of refined parameters = 325, R = 0.081. [Cu(2-BB)(MeOH)(ClO(4))](ClO(4)): triclinic, P&onemacr; (No. 2), a = 8.493(3) Å, b = 10.846(7) Å, c = 14.484(5) Å, alpha = 93.71(4) degrees, beta = 103.13(3) degrees, gamma = 100.61(4) degrees, V = 1270(1) Å(3), Z = 2, number of unique data [I>/= 2sigma(I)] = 2612, number of refined parameters = 352, R = 0.073. [Cu(2-BB)(N(3))](ClO(4)): monoclinic, P2(1)/n (No. 14), a = 12.024(3) Å, b = 12.588(5) Å, c = 15.408(2) Å, beta = 101,90(2) degrees, V = 2282(1) Å(3), Z = 4, number of unique data [I >/= 2sigma(I)] = 2620, number of refined parameters = 311, R = 0.075. [Cu(2-BB)(NO(2))](ClO(4))(MeCN): triclinic, P&onemacr; (No. 2), a = 7.402(2) Å, b = 12.500(1) Å, c = 14.660(2) Å, alpha = 68.14(1) degrees, beta = 88.02(2) degrees, gamma = 78.61(1) degrees, V = 1233.0(4) Å(3), Z = 2, number of unique data [I>/= 2sigma(I)] = 2088, number of refined parameters = 319, R = 0.070. In all the complexes the 1-BB or 2-BB ligands coordinate the Cu(II) cations through their three donor atoms. The complexes with 2-BB appear to be more flexible than those with 1-BB. The nitrito ligand is bidentate in [Cu(2-BB)(NO(2))](ClO(4))(MeCN) and essentially monodentate in [Cu(1-BB)(DMSO-O)(NO(2))](ClO(4)). The copper(I) complexes exhibit nitrite reductase activity and react rapidly with NO(2)(-) in the presence of stoichiometric amounts of acid to give NO and the corresponding copper(II) complexes. Under the same conditions the reactions between the copper(I) complexes and NO(+) yield the same amount of NO, indicating that protonation and dehydration of bound nitrite are faster than its reduction. The NO evolved from the solution was detected and quantitated as the [Fe(EDTA)(NO)] complex. The order of reactivity of the Cu(I) complexes in the nitrite reduction process is [Cu(2-BB)](+) > [Cu(1-BB)](+) > [Cu(TB)](+) > [Cu(AcBB)](+).

The effect of strain in the axial coordination of imidazole to the heme has been studied in the chelate complexes deuterohemin-histidine (DH-His) and deuterohemin-alanylhistidine (DH-AlaHis). Molecular mechanics calculations indicate that three types of distortion of the axial ligand occur in DH-His, due to the relatively short length of the arm carrying the donor group: tilting off-axis, tipping, and inclination of the imidazole plane with respect to the axial Fe-N bond. The effects of tilting (Deltagamma approximately 10 degrees ) and inclination of the imidazole ring (Deltadelta approximately 17 degrees ) are dominant, while tipping is small and is probably of little importance here. By contrast, the axial imidazole coordination is normal in DH-AlaHis and other computed deuterohemin-dipeptide or -tripeptide complexes where histidine is the terminal residue, the only exception being DH-ProHis, where the rigidity of the proline ring reduces the flexibility of the chelating arm. The distortion in the axial iron-imidazole bond in DH-His has profound and negative influence on the binding and catalytic properties of this complex compared to DH-AlaHis. The former complex binds more weakly carbon monoxide, in its reduced form, and imidazole, in its oxidized form, than the latter. The catalytic efficiency in peroxidative oxidations is also reduced in DH-His with respect to DH-AlaHis. The activity of the latter complex is similar to that of microperoxidase-11, the peptide fragment incorporating the heme that results from hydrolytic cleavage of cytochrome c.

The reaction that gives met-hemocyanin from Octopus vulgaris oxy-hemocyanin has been reinvestigated under several experimental conditions. Various anions including azide, fluoride and acetate have been found to promote this reaction. Kinetic data indicate that the reaction mechanism is different from that currently accepted involving a peroxide displacement of bound dioxygen through an associative chemistry on an open axial position of the copper ions [Hepp, A. F., Himmelwright, R. S., Eickman, N. C. & Solomon, E. I. (1979) Biochem. Biophys. Res. Commun. 89, 1050-1057; Solomon, E. I. in Copper proteins (Spiro, T. G., ed.) pp. 43-108, J. Wiley, New York]. Our study suggests that the protonated form of the anion is likely to be the species reacting with the oxygenated form of the protein. Furthermore, it is also proposed that protonation of bound dioxygen generates an intermediate hydroperoxo-dicopper(II) complex to which the exogenous anion is also bound. This intermediate in not accumulated and preceds the release of hydrogen peroxide by reaction with water. Upon dialysis it leads to the met-hemocyanin form. The structure of this dinuclear copper(II) derivative contains a di-mu-hydroxo bridge but there is evidence from optical and circular dichroism spectra for partial protonation of these bridges at low pH. As a consequence, while one azide molecule binds in the bridging mode to met-hemocyanin with low affinity (K = 30 M-1) at pH 7.0, it binds with much higher affinity at pH 5.5 (K = 1500 M-1), where a second azide ligand also binds in the terminal mode (K = 20 M-1). The coordination mode of the azide ligands is deduced from the optical and circular dichroism spectra of the protein complexes.

Ventricular premature complexes (VPCs) after acute myocardial infarction (AMI) remain important determinants of survival in the post-thrombolytic era. The role of thrombolysis, left ventricular function, and Holter ST-segment depression in modulating VPC frequency is unclear. In a placebo-controlled, randomized study of tissue-type plasminogen activator (t-PA) in 103 patients with AMI (Tissue Plasminogen Activator: Toronto study), VPC frequency and ST depression on Holter monitoring (day 7), ejection fraction by radionuclide scan (day 9), and infarct artery patency and cross-sectional area on day 1 (n = 42) were assessed. After administering t-PA, VPC frequency was 10 +/- 58/hour (mean +/- SD), similar to that after placebo (23.5 +/- 91.7, p = NS). However, patients with ST depression had greater VPC frequency (56 +/- 140/hour) than those without it (1.3 +/- 2.6/hour, p = 0.05). Ejection fraction was negatively correlated with VPC frequency (r = -0.33, p < 0.001). By multivariate analysis, ejection fraction (F = 7.0, p < 0.01) and ST depression (F = 5.8, p < 0.02) were the only independent predictors of VPC frequency. In this placebo-controlled study, VPC frequency after AMI was not related to thrombolytic administration but was associated with ST depression and ejection fraction. This suggests that the underlying extent of both infarcted and ischemic myocardium is important in modulating ventricular arrhythmias after AMI.

A patient presented with a very unusual multicystic cardiac mass that echocardiographically mimicked an echinococcal cyst. The management of this patient is highlighted, including the clinical diagnosis, investigation, surgical management, pathological studies and review of the relevant literature.

The reactivity of a series of para-substituted phenolic compounds in the peroxidation catalyzed by chloroperoxidase was investigated, and the results were interpreted on the basis of the binding characteristics of the substrates to the active site of the enzyme. Marked selectivity effects are observed. These operate through charge, preventing phenolic compounds carrying amino groups on the substituent chain to act as substrates for the enzyme, and through size, excluding potential substrates containing bulky substituents to the phenol nucleus. Also, chiral recognition is exhibited by chloroperoxidase in the oxidation of N-acetyltyrosine, where only the L isomer is oxidized. Kinetic measurements show that, in general, the efficiency of chloroperoxidase in the oxidation of phenols is lower than that of horseradish peroxidase. Paramagnetic NMR spectra and relaxation rate measurements of chloroperoxidase-phenol complexes are consistent with binding of the substrates close to the heme, in the distal pocket, with the phenol group pointing toward the iron atom. On the other hand, phenolic compounds which are not substrates for chloroperoxidase bind to the enzyme with a much different disposition, with the phenol group very distant from the iron and probably actually outside the active-site cavity.

Cytotoxicity and morphological transformation has been studied in BALB/3T3 Cl A31-1-1 mouse embryo cells for ammonium vanadate [vanadium(V)] and vanadyl sulphate [vanadium(IV)] alone or in combination with diethylmaleate (DEM), a cellular glutathione (GSH)-depleting agent. Cells exposed for 24 h to 10(-5) M vanadium(V) alone or in combination with 3 x 10(-6) M DEM showed the characteristic hyperfine EPR signal of vanadium(IV), which was more obvious in the case of exposure to vanadium(V) alone. This suggests that the amount of vanadium(V) reduced to vanadium(IV) decreased in GSH-depleted cells. While vanadium(IV) at concentrations of 3 x 10(-6) M and 10(-5) M was not transforming in the cells, vanadium(V) showed neoplastic transforming activity (P < 0.025 and P < 0.001 for the two doses, respectively) in comparison to controls (vanadium unexposed cells). Cytotoxicity and morphological transformation in cells exposed to vanadium(V) in combination with 3 x 10(-6) M DEM were significantly more intensive (P < 0.005 and P < 0.01 for the two doses of vanadate tested) compared to the corresponding values observed in cells exposed to vanadium(V) alone. This suggests that the final transforming activity response is dependent on the intracellular GSH-mediated mechanism of reduction of vanadium(V) to vanadium(IV): (i) the extent to which vanadium(V) should be bioreduced to less toxic vanadium(IV) via intracellular GSH is a key point in determining the intensity of the observed neoplastic action; (ii) the carcinogenic potential of vanadium(V) should be strictly dependent on its intracellular persistence which could lead to changes in normal metabolic patterns of vanadium(V) in the oxidized form due to lack of GSH-mediated reduction.

Objectives: We performed Holter monitoring on days 4 and 7 after acute myocardial infarction in 109 patients to assess whether ST segment shift would identify those with more severe coronary artery disease, left ventricular dysfunction and unfavorable prognosis., Background: Silent myocardial ischemia is a frequent and prognostically significant event after acute myocardial infarction. However, the specific pathophysiologic mechanisms and the impact of thrombolytic therapy are uncertain., Methods: In addition to Holter monitoring, patients underwent exercise testing, radionuclide angiography on days 1 and 9 and quantitative coronary angiography on day 9., Results: Thirty-five patients (32%) had ST segment depression and had similar recombinant tissue-type plasminogen activator (rt-PA) treatment assignment and a reduced cross-sectional area of the infarct-related artery (0.59 +/- 0.57 vs. 1.04 +/- 1.26 mm2, p < 0.05). Global left ventricular function improved from day 1 to day 9 in patients without (4% +/- 11%, p < 0.001) but not in those with (0% +/- 7%) ST segment depression. In-hospital event rates were similar; however, follow-up 18 +/- 11 months after hospital discharge revealed a greater frequency of death and recurrent myocardial infarction in patients with compared with those without ST segment depression (27% vs. 6%, p = 0.03)., Conclusions: After acute myocardial infarction, approximately one third of patients have ST segment depression on Holter monitoring, independent of the use of thrombolytic therapy. The unfavorable prognosis observed in these patients may be related to greater lumen obstruction in the infarct-related artery and lack of improvement in left ventricular function.

The binding of a series of alkyl aryl sulfides to chloroperoxidase (CPO) and horseradish peroxidase (HRP) has been investigated by optical difference spectroscopy, circular dichroism, paramagnetic NMR spectroscopy, and NMR relaxation measurements. The data are consistent with binding of the sulfides in the distal side of the heme pocket with CPO and near the heme edge with HRP. A linear correlation between the binding constants of para-substituted sulfides to CPO and the Taft sigma I parameter suggests that these substrates act as donors in donor-acceptor complexes involving some residue of the protein chain. Spectral studies during turnover show that high enantioselectivity in the CPO-catalyzed oxidation of sulfides results from a reaction pathway that does not involve the accumulation of compound II enzyme intermediate.

The effect of vanadium (V) on the activity of horseradish peroxidase, catalase, glutathione peroxidase, and superoxide dismutase has been studied. A competitive inhibition pattern was evident for vanadate ions on the activity of horseradish peroxidase (Ki = 41.2 microM). No significant inhibitory effects were found when V(V) was tested with catalase and when either V(IV) or V(V) were assayed with glutathione peroxidase. For the latter, the effect of V on the different components of the reaction system was investigated. V(V) did not significantly affect SOD activity when assayed with the sulfite method, which is devoid of interferences with V(V); however, there was an apparent inhibitory dose-response pattern for either V(IV) or V(V) using the pyrogallol assay, owing to an interference of pyrogallol with the metal. Besides, no significant binding of V(IV) or V(V) to the enzyme could be demonstrated. The lack of a direct inhibitory effect of V on the activity of the main antioxidant enzymes suggests that many biological and toxicological effects of V may be mediated more by oxidative reactions of the metal or of its complexes with physiologically relevant biomolecules than by a direct modulation of enzymatic activities.

The binding of various ligand molecules to the binuclear Cu(I) site of deoxy-hemocyanin has been investigated through the changes produced in the aromatic region of the circular dichroism spectrum of the protein, where a cluster of tryptophan residues located in the vicinity of copper site undergo conformational reorientations in the presence of exogenous ligands coordinated to the metal. In agreement with expectations, the binuclear site of arthropod hemocyanin is severely hindered to the access of exogenous ligands except for very small molecules like CO, O2 or CN- while for mollusc proteins ligands such as thiourea and 2-mercaptoethanol bind easily to the Cu(I) sites. However, the access of the ligand becomes progressively hindered and eventually prevented as the size of substituents on the ligand increases.

The interaction of a series of derivatives of tyrosine with horseradish peroxidase (HRP) and lactoperoxidase (LPO) was studied by using optical difference spectroscopy, c.d. and proton n.m.r. spectroscopy in order to reveal differences in the mode of binding of L-tyrosine and D-tyrosine, which are substrates of but react at different rates with the two peroxidases, to HRP and LPO. All the donor molecules form 1:1 complexes with HRP and LPO, but they display a range of affinities for the enzymes. Whereas D-tyrosine binds to HRP more strongly than does L-tyrosine, the opposite holds for the binding to LPO. The distances of the protons of bound tyrosine molecules from the haem iron atoms of HRP and LPO indicate that the site of binding of these substrates is the same as that of simple phenols. This involves the interaction of the phenol nucleus with a protein tyrosine residue [Sakurada, Takahashi & Hosoya (1986) J. Biol. Chem. 261, 9657-9662; Modi, Behere & Mitra (1989) Biochim. Biophys. Acta 996, 214-225]. However, for the present substrates the additional interaction of the carboxylate group with a protein residue (probably an arginine residue) provides further stabilization for the adducts HRP-D-tyrosine and LPO-L-tyrosine with respect to the corresponding complexes with the opposite enantiomers. The differences in the mode of binding of L-tyrosine and D-tyrosine to HRP and LPO is thus determined by the fact that the spatial arrangement of the interacting protein residues can recognize the chirality of the C(alpha)-CO2- and C(beta)-C6H4OH attachment bonds of the substrates.

The chloroperoxidase-catalyzed and horseradish peroxidase catalyzed oxidations of sulfides by tert-butyl and other peroxides have been investigated. The former metal enzyme afforded the corresponding sulfoxides having R absolute configuration in up to 92% enantiomeric excess (ee), whereas the latter gave racemic products. The various factors that control the enantioselectivity of the oxygenation have been examined.

Characteristics of 107 Vietnam veterans with and without Posttraumatic Stress Disorder (PTSD), who had been exposed to varying levels of combat, were compared. Severity of psychopathology as assessed on the Eysenck Personality Questionnaire, locus of control orientation as measured by the Nowicki-Strickland Internal-External Control Scale, and ability to have provided structure and meaning to the Vietnam experience were examined. Compared to veterans with Posttraumatic Stress Disorder, those without the disorder had lower Neuroticism and Psychoticism scores, were more internal in their locus of control orientation, and were more likely to have shown ability to provide structure to the Vietnam experience. The additional finding that veterans with high combat experience but without PTSD evidenced less neuroticism than low combat veterans without PTSD provides evidence that those who did not develop the disorder despite high exposure to combat stress are individuals with exceptional emotional strength and resilience.

The coordination structures of various species in the copper(II)-L-histidine (1:2) system in aqueous solution have been deduced by investigating the pH dependence of the electronic and circular dichroism spectra. The contribution to the spectra of the glycine-like and histamine-like binding modes of L-histidine has been determined by recording the spectra of the ternary system copper(II)-histamine-L-histidine (1:1:1) and copper(II)-amino acid-L-histidine (1:1:1), respectively, in neutral aqueous solutions. Apical binding to copper(II) by the donor atom on the histidine side chain can contribute significantly to the stabilization of each of the two basic histidine binding modes. It has been concluded that Cu(HL)2+ (L-histidine = HL), the major species below pH approximately 3, contains a glycine-like bound histidine ligand with an unbound imidazolium cation. The species Cu(HL)L+, which is prominent in the pH region near 4.5, contains a glycine-like bound histidine molecule, with protonated imidazole ring, and a histamine-like bound histidine molecule. CuL2, the major species at neutral pH, exists in solution as an equilibrium mixture of a mixed-type chelation structure, with a glycine-like and a histamine-like bound histidine ligand, and a structure containing both histidine ligands bound histamine-like. The species containing deprotonated imidazole nuclei, such as Cu(H-1L2)-, which predominates above pH approximately 11, show an increased contribution by structures containing glycine-like bound histidine compared with CuL2.

Titration of native ascorbate oxidase from green zucchini squash (Cucurbita pepo) with azide in 0.1 M-phosphate buffer, pH 6.8, exhibits a biphasic spectral behaviour. Binding of the anion with 'high affinity' (K greater than 5000 M-1) produces a broad increase of absorption in the 400-500 nm region (delta epsilon approximately 1000 M-1.cm-1) and c.d. activity in the 300-450 nm region, whereas azide binding with 'low affinity' (K approximately 100 M-1) is characterized by an intense absorption band at 420 nm (delta epsilon = 6000 M-1.cm-1), corresponding to negative c.d. activity and a decrease of absorption at 330 nm (delta epsilon = -2000 M-1.cm-1). The high-affinity binding involves a minor fraction of the protein containing Type 3 copper in the reduced state, and the spectral features of this azide adduct can be eliminated by treatment of the native enzyme with small amounts of H2O2, followed by dialysis before azide addition. As shown by e.s.r. spectroscopy, Type 2 copper is involved in both types of binding, its signal being converted into that of a species with small hyperfine splitting constant [12 mT (approximately 120 G)] in the case of the low-affinity azide adduct. The spectral similarities of the two types of azide adducts with the corresponding adducts formed by native laccase, which also exhibits Type 3 copper heterogeneity, are discussed.

A new chemical procedure is described for preparing labelled GM1 molecular species, carrying as acyl moiety pyrene-decanoic acid, 5-doxyl-stearic acid and 16-doxyl-stearic acid. It makes use of a mixed anhydride formed by ethylchloroformate and the labelled acyl chain, as the reagent for N-acylation of a deacetylated, deacylated GM1 ganglioside, which is prepared by alkaline hydrolysis of natural GM1. The reaction performed with a unitary GM1 derivative/mixed anhydride molar ratio, occurs with a yield of above 40%. The labelled deacetylated GM1 molecular species are then N-acetylated by means of acetic anhydride with quantitative yield. The chemical process of insertion of labelled fatty acid and reconstitution of GM1 ganglioside has been confirmed by GLC-MS and NMR analyses. Fluorescence and electron spin resonance experiments indicate that the labelled gangliosides behave similarly to natural GM1, in both the aggregation properties and the capability to be transferred from micelles to vesicular dispersions of phospholipids.

An open, cross-over study was performed on a population of 24 geriatric patients hospitalized because of depressive syndrome. They were subdivided, according to Hamilton's Scale as modified for the aged, into low- and high-score subgroups. The study period covered 2 months. Half the patients received acetylcarnitine for 1 month and placebo thereafter (Group A); the other half received placebo and acetyl-carnitine thereafter (Group B). Statistical evaluation was twofold: parametrical analysis of variance was carried out on 4 subgroups (A1, A2, B1 and B2) and analysis of the score percentage modifications before and after treatment was performed on Groups A and B. The experimental results showed that acetylcarnitine treatment was highly effective and statistically significant in subgroups A1/B1, A2/B2, A1, B1 and B2. In particular, it should be noted that depressive tendencies were significantly modified in most groups, whereas general somatic symptoms as well as anxiety, asthenia and sleep disturbances proved to be little affected. Clinical evaluation, carried out by calculation of modifications in pre- and post-treatment score percentages, provided clear evidence that acetylcarnitine was particularly effective in patients showing more serious clinical symptoms. The drug caused no side-effects at the doses and regimens used.