Lysine-derived fluorophores formed by autoxidation of linoleic acid

To obtain an insight into fluorophores formed in proteins during lipid peroxidation, a lysine residue analogue (N(alpha)-hippuryllysine) was exposed to autoxidation of linoleic acid catalyzed by iron(III)-EDTA and L-ascorbic acid. The reaction predominantly produced two fluorescent products, N,N'-bis[5-(N-benzoylglycylamino)-5-carboxypentyl]-2-hydroxy-2-pentyl-3-imino-l,2-dihydropyrrole (II) and N,N'-bis[5-(N-benzoylglycylamino)-5-carboxypentyl]-2-hydroxy-2-(7-carboxyheptyl)-3-imino-1,2-dihydropyrolle (I).     

Maillard reaction-like lysine modification by a lipid peroxidation product: immunochemical detection of protein-bound 2-hydroxyheptanal in vivo

2-Hydroxyheptanal (2-HH) is one of the reactive aldehyde species generated during the peroxidation of n-6 polyunsaturated fatty acids, such as linoleic and arachidonic acids. Analogous to the Maillard reaction of reducing sugars, 2-HH readily reacts with lysine epsilon-amino groups. In the present study, to define the occurrence of the Maillard reaction-like lysine modification by 2-HH in vivo, we raised a monoclonal antibody directed to a trihydropyridinone (THPO) structure, 1-alkyl-4-butyl-5-pentyl-1,2,6-trihydropyridin-3-one, formed from 2-HH and lysine, and examined the presence of the antigenic structure in the human atherosclerotic aorta. Mice were immunized with the 2-HH-modified keyhole limpet hemocyanin (KLH) as the immunogen. Using a THPO-carrier protein conjugate, we screened the hybridomas and finally obtained a clone that produced the monoclonal antibody 3C8 (mAb3C8). The antibody strongly recognized bovine serum albumin (BSA) treated with 2-HH, but showed no cross-reactivity with BSAs modified with other related aldehydes. By using this antibody, it was revealed that the antigenic structure was indeed present in atherosclerotic lesions of the human aorta.     

Pyridinium-carbaldehyde: active Maillard reaction product from the reaction of hexoses with lysine residues

Besides the formation of the aminotriazine N6-[4-(3-amino-1,2,4-triazin-5-yl)-2,3-dihydroxybutyl]-L-lysine, the reaction of [1-13C]D-glucose with lysine and aminoguanidine leads to the generation of 6-[2-([[amino(imino)methyl]hydrazono]methyl)pyridinium-1-yl]-L-norleucine (14-13C1). The dideoxyosone N6-(2,3-dihydroxy-5,6-dioxohexyl)-L-lysine was shown to be a precursor in the formation of 14-13C1, which proceeds via the reactive carbonyl intermediate 6-(2-formylpyridinium-1-yl)-L-norleucine (13-13C1). In order to study the reactivity of 13-13C1, the model compound 1-butyl-2-formylpyridinium (18) was prepared in a two-step procedure starting from 2-pyridinemethanol. The reaction of the pyridinium-carbaldehyde 18 with L-lysine yielded the Strecker analogous degradation product 2-(aminomethyl)-1-butylpyridinium and another compound, which was shown to be as 1-butyl-2-[(2-oxopiperidin-3-ylidene)methyl]pyridinium. Reaction of 18 with the C-H acidic 4-hydroxy-5-methylfuran-3(2H)-one leads to the formation of the condensation product 1-butyl-2-[hydroxy-(4-hydroxy-5-methyl-3-oxofuran-2(3H)-ylidene)methyl]-pyridinium.     

Steps in the conversion of alpha-ketosuberate to 7-mercaptoheptanoic acid in methanogenic bacteria

The biosynthetic steps involved in the conversion of alpha-ketosuberate to 7-mercaptoheptanoic acid were studied in cell-free extracts of methanogenic bacteria. The pathway was established by measuring the incorporation of stable isotopically labeled precursors into the S-methyl ether methyl ester derivative of the enzymatically generated 7-mercaptoheptanoic acid by using gas chromatography-mass spectrometry (GC-MS). Quantitation of the 7-mercaptoheptanoic acid produced in the incubations with the substrates was accomplished by using an internal standard of 6-mercaptohexanoic acid. [4,4,6,6-2H4]-2-Oxosuberic acid, [7-2H]-7-oxoheptanoic acid, [2-2H]-2(RS)-(5-carboxypentyl)thiazolidine-4(R)-carboxylic acid, and S-(6-carboxyhexyl)cysteine were each shown to be converted to 7-mercaptoheptanoic acid. Incubation of cell extracts with a mixture of 2(RS)-(5-carboxypentyl)thiazolidine-4(R)-carboxylic acid and [2-2H]-2-(RS)-(5-carboxypentyl)-[34S]thiazolidine-4(R)-carboxylic acid showed that both 34S and 2H are incorporated into the 7-mercaptoheptanoic acid but only after separation of the cysteine from the [7-2H]-7-oxyheptanoic acid portion of the molecule. Furthermore, the sulfur from the cysteine was incorporated into the thiol only after its elimination from the cysteine and subsequent mixing with an unlabeled sulfur source which had a molecular weight of sufficient size that it was excluded from Sephadex G-25. Hydrogen sulfide was found to supply the sulfur for the production of the 7-mercaptoheptanoic acid in a reaction that was shown to obtain its reducing equivalents from hydrogen via an F420-dependent hydrogenase.     

Synthesis and evaluation of novel 2-butyl-4-chloro-1-methylimidazole embedded chalcones and pyrazoles as angiotensin converting enzyme (ACE) inhibitors

A series of novel 2-butyl-4-chloro-1-methylimidazole embedded aryl and heteroaryl derived chalcones and pyrazoles were synthesized and evaluated for their angiotensin converting enzyme (ACE) inhibitory activity. The condensation of 2-butyl-4-chloro-1-methylimidazole-5-carboxaldehyde with various aryl and heteroaryl methyl ketones in the presence of 10% aqueous NaOH in methanol proceeded efficiently to give the respective chalcones in very good yields. Further, the reaction of chalcones with hydrazine hydrate in acetic acid gave substituted pyrazole analogues. Screening all 36 new compounds using ACE inhibition assay, resulted chalcones with better ACE inhibitory activity compared to the respective pyrazole analogues. Among the chalcones 4a-r, three compounds, (E)-3-(2-butyl-4-chloro-1-methyl-1H-imidazol-5-yl)-1-(5-chlorothiophen-2-yl)prop-2-enone 4i, (E)-3-(2-butyl-4-chloro-1-methyl-1H-imidazol-5-yl)-1-(1H-pyrrol-2-yl)prop-2-enone 4l, (E)-3-(2-butyl-4-chloro-1-methyl-1H-imidazol-5-yl)-1-(dibenzo[b,d] thiophen-2-yl)prop-2-enone 4q were resulted as most active ACE inhibitors with IC(50) of 3.60 μM, 2.24 μM, and 2.68 μM, respectively.     

π-Arene complexes.: Part 12. Synthesis of chromiumtricarbonyl complexes of quinoline and N-methylindoles and selected metallation reactions

The lithiation of indole, using a slight excess of n-butyl lithium in THF, followed by methylation and reaction with [Cr(CO)₆] in refluxing dibutyl ether, resulted in the formation of [Cr(η⁶-N-methylindole)(CO)₃] (1a) and [Cr(η⁶-N-methyl-2-methylindole)(CO)₃] (1b). In contrast, lithiation of quinoline in THF, silylation and the subsequent reaction with [Cr(CO)₆] under similar reaction conditions, afforded [Cr(η⁶-N-trimethylsilyl-2-butyl-1,2-dihydroquinoline)(CO)₃] (2) and [Cr(η⁶-{2-butyl-1,2,3,4-tetrahydroquinoline})(CO)₃] (3). The formation of [Cr(η⁶-2,2′-bis{N-methylindolyl})(CO)₃] (4) implied lithiation at the 2-position of 1a. However, metallation at the 7-position was also indicated during the same reaction. In the presence of [Mn(CO)₅Br], product 4 and the transmetallation product [Cr(η⁶-{7-(N-methylindolyl)Mn(CO)₅})(CO)₃] (5) were isolated. Reaction with titanocene dichloride gave [Cr(η⁶-{2-(N-methylindolyl)TiCp₂Cl})(CO)₃] (6), which slowly converted into [TiCp₂{Cr(η⁶-2-(N-methylindolyl)(CO)₃}₂] (7).     

Hydroxynitrile Lyase Catalysis in Ionic Liquid-containing Systems

The cleavage of mandelonitrile catalysed by hydroxynitrile lyases (HNL) from Prunus amygdalus (PaHNL) and Manihot esculenta (MeHNL) proceeded more rapidly in monophasic aqueous media containing 1-propyl-3-methylimidazolium tetrafluoroborate [C₄MIm][BF₄] than in media containing acetonitrile or THF. Both HNLs were much more thermostable in [C₄MIm][BF₄] than in acetonitrile or THF. The addition of each of the four ionic liquids 1-butyl-, 1-pentyl- and 1-hexyl-3-methylimidazolium tetrafluoroborates at 2–6% (v/v in the aqueous phase) increased both the enzyme activity and the product e.e. in the PaHNL-catalysed transcyanation in an aqueous/DIPE biphasic system. However, MeHNL was inactivated by the ionic liquids, as indicated by the decreased reaction rate, substrate conversion and product e.e.     

Insertion of dNTPs opposite the 1,N2-propanodeoxyguanosine adduct by Sulfolobus solfataricus P2 DNA polymerase IV

1, N (2)-Propanodeoxyguanosine (PdG) is a stable structural analogue for the 3-(2'-deoxy-beta- d- erythro-pentofuranosyl)pyrimido[1,2-alpha]purin-10(3 H)-one (M 1dG) adduct derived from exposure of DNA to base propenals and to malondialdehyde. The structures of ternary polymerase-DNA-dNTP complexes for three template-primer DNA sequences were determined, with the Y-family Sulfolobus solfataricus DNA polymerase IV (Dpo4), at resolutions between 2.4 and 2.7 A. Three template 18-mer-primer 13-mer sequences, 5'-d(TCACXAAATCCTTCCCCC)-3'.5'-d(GGGGGAAGGATTT)-3' (template I), 5'-d(TCACXGAATCCTTCCCCC)-3'.5'-d(GGGGGAAGGATTC)-3' (template II), and 5'-d(TCATXGAATCCTTCCCCC)-3'.5'-d(GGGGGAAGGATTC)-3' (template III), where X is PdG, were analyzed. With templates I and II, diffracting ternary complexes including dGTP were obtained. The dGTP did not pair with PdG, but instead with the 5'-neighboring template dC, utilizing Watson-Crick geometry. Replication bypass experiments with the template-primer 5'-TCACXAAATCCTTACGAGCATCGCCCCC-3'.5'-GGGGGCGATGCTCGTAAGGATTT-3', where X is PdG, which includes PdG in the 5'-CXA-3' template sequence as in template I, showed that the Dpo4 polymerase inserted dGTP and dATP when challenged by the PdG adduct. For template III, in which the template sequence was 5'-TXG-3', a diffracting ternary complex including dATP was obtained. The dATP did not pair with PdG, but instead with the 5'-neighboring T, utilizing Watson-Crick geometry. Thus, all three ternary complexes were of the "type II" structure described for ternary complexes with native DNA [Ling, H., Boudsocq, F., Woodgate, R., and Yang, W. (2001) Cell 107, 91-102]. The PdG adduct remained in the anti conformation about the glycosyl bond in each of these threee ternary complexes. These results provide insight into how -1 frameshift mutations might be generated for the PdG adduct, a structural model for the exocylic M 1dG adduct formed by malondialdehyde.     

Beta-oxidation of 2-ethyl-5-carboxypentyl phthalate in rodent liver

[7-14C]-2-Ethyl-5-carboxypentyl phthalate was isolated and purified from urine of rats given [7-14C]-di-(2-ethylhexyl) phthalate. This metabolite was shown to serve as a precursor for 2-ethyl-3-carboxypropyl phthalate in vivo. 2-Ethyl-5-carboxypentyl phthalate was oxidized to 2-ethyl-3-carboxypropyl phthalate in liver slices from control or, much more rapidly, from clofibrate-pretreated rats. Inhibition by KCN in liver slices from untreated rats, and strong inhibition by acrylate, suggested that formation of 2-ethyl-3-carboxypropyl phthalate involved mitochondrial beta-oxidation. The strong enhancement of the production of this compound by clofibrate (a very weak inducer for mitochondrial dehydrogenases), and strong inhibition by chlorpromazine suggested that peroxisomes may also be able to oxidize 2-ethyl-5-carboxypentyl phthalate. We were able to detect beta-oxidation of 2-ethyl-5-carboxypentyl phthalate to 2-ethyl-3-carboxypropyl phthalate using purified mitochondria, but strong phthalate monoester hydrolase activity observed during incubation of the former compound with purified peroxisomes made it impossible to determine whether 2-ethyl-3-carboxypropyl phthalate could be produced in the latter organelle or not. 2-Ethyl-5-carboxypentyl phthalate was such an inefficient substrate for beta-oxidation compared to palmitic acid that it is unlikely that it contributes significantly to the production of H2O2 in rats chronically exposed to di-(2-ethylhexyl) phthalate. Normal fatty acids are most likely to serve as the dominant substrates for peroxisomal beta-oxidase.     

Photovoltaic properties of three new cyanine dyes for dye-sensitized solar cells.

Three carboxylated cyanine dyes, 2-[(1-butyl-3,3-dimethyl-5-carboxylindoline-2-ylidene)propenyl]-[1-butyl-3,3-dimethyl-7-(1-ethyl-1H-1,2,3-triazole-4-yl]-1H-benz[e]indolium iodide (), 2-[(1-butyl-3,3-dimethyl-5-carboxyl-indoline-2-ylidene)propenyl]-{1-butyl-3,3-dimethyl-7-[(4-piperidine-N-ethyl-1,8-naphthalimide)-1H-1,2,3-triazole-4-yl]}-1H-benz[e]indolium iodide (Cy2) and 2-[(1-butyl-3,3-dimethyl-5-carboxyl-indoline-2-ylidene)propenyl)-[1-butyl-3,3-dimethyl-7-{(4-piperidine-N-butyl-1,8-naphthalimide)-1H-1,2,3-triazole-4-yl}]-1H-benz[e]indolium iodide (Cy3), have been synthesized and characterized with regard to their structures and electrochemical properties. Upon adsorption onto a TiO(2) electrode, the absorption spectra of the three cyanine dyes are all broadened to both red and blue sides compared with their respective spectra in an acetonitrile and ethanol mixture. Cy2 and Cy3, containing a naphthalimide group, have stronger absorption intensities and broader absorption spectra than , which consequently leads to better light-to-electricity conversion properties. Among the three cyanine dyes, generated the highest photoelectric conversion yield of 4.80% (J(sc) = 14.5 mA cm(-2), V(oc) = 500 mV, FF = 0.49) under illumination with 75 mW cm(-2) white light from a Xe lamp.     

Role of quinone-iron(III) interaction in NADPH-dependent enzymatic generation of hydroxyl radicals.

To study the effect of chelation of iron ions by quinones on the generation of OH radicals in biological redox systems, we have synthesized quinones that can form complexes with Fe(III) ions: 2-phenyl-4-(butylamino)naphtho[2,3-h]quinoline-7,12-dione (Qbc) and 2-phenyl-4-(octylamino)naphtho[2,3-h]quinoline-7,12-dione (Qoc). A quinone with a similar structure without chelating group was synthesized as a control sample: 2-phenyl-5-nitronaphtho[2,3-g]indole-6,11-dione (Qn). Using optical spectroscopy, we determined the stability constant of Qbc with Fe(III) [Ks = (7 +/- 1) x 10(18) M-3] and the stoichiometry of the complex Fe(Qbc)3 in chloroform solutions. One-electron reduction potentials of Qbc, Qn, and adriamycin in dimethyl sulfoxide were measured by cyclic voltammetry. In the presence of Fe(III) the one-electron reduction potentials shifted toward positive values by 0.16 and 0.1 V for Qbc and adriamycin, respectively. Using the spin trap 5,5'-dimethyl-1-pyroline N-oxide (DMPO) and EPR, it was found that Qbc in the Fe(III) complex stimulated the formation of OH radicals in the enzymatic system consisting of NADPH and NADPH-cytochrome P-450 reductase more efficiently than adriamycin and quinone Qn. This is indicated by the absence of a lag period in the spin adduct appearance for Qbc and by a significantly higher rate of the spin adduct production, as well as by a larger absolute concentration of the spin adduct obtained for Qbc in comparison with Qn in the presence of Fe(III).(ABSTRACT TRUNCATED AT 250 WORDS)     

Suppression of natriferic activity of the vasopressin molecule by modifications in positions 1, 2 and 4

The capacity of five synthetic analogs of [8-arginine] vasopressin (AVP) to stimulate frog skin sodium transport (natriferic activity) was characterized electrophysiologically using the method of short-circuit current, and compared to that of synthetic AVP. The analogs used were [8-arginine] vasopressins modified in positions 1 and 2: [1-(1-mercapto-4-tert-butylcyclohexaneacetic acid)] AVP (I); [1-(1-mercapto-4-methylcyclohexaneacetic acid)] AVP (II); [1-(1-mercapto-4-methylcyclohexaneacetic acid)-2-O-methyltyrosine] AVP (III); and in position 4: [1-(1-mercaptocyclohexaneacetic acid)-4-arginine] AVP (IV); [1-(2-mercaptopropionic acid)-4-arginine] AVP (V). The addition of synthetic vasopressins I, II and V to the frog skin resulted in a weaker stimulation of the skin sodium transport, measured as the level of the short-circuit current (Isc), as compared to that induced by synthetic AVP. In relation to natriferic activity, analogs III and IV did not change the electrical parameters of the skin. It is concluded that introduction of cyclic structure at the beta-carbon in position 1 of the vasopressin molecule decreased its natriferic activity by about 70%. The same reduction of the activity was caused by the replacement of the glutamine residue in position 4 with arginine, and deamination in position 1. Cyclic structure bound in position 1 together with methylation of tyrosine in position 2 resulted in a full suppression of natriferic activity. Similarly, introduction of cyclic group in position 1 in combination with substitution of glutamine in position 4 with arginine totally abolished natriferic activity.     

A Mechanistic Study of the Dihydroflavin Reductive Cleavage of the Dihydroflavin-Tetrahydronaphthalene Epoxide Adducts

Dihydroflavins are facile reducing agents and potent nucleophiles. The dihydroflavin nucleophilic reactivity, as measured by the rate of covalent flavin adduct formation with tetrahydronaphthalene epoxides, is comparable to that of the thiolate anion (Y. T. Lee and J. F. Fisher (1993) J. Org. Chem. 58, 3712). In these reactions there appears subsequent to the nucleophilic cleavage of the epoxide by the dihydroflavin the product corresponding to formal hydride reduction product (at the benzylic carbon) of these epoxides. Thus the reaction of (+/-)-1a,2,3, 7b-tetrahydro-(1aalpha,2alpha,3beta,7balpha)-naphth[1,2-b]oxirene-2,3-diol (1), (+/-)-1a,2,3,7b-tetrahydro-(1aalpha,2beta,3alpha,7balpha)-naphth[1,2-b]oxirene-2,3-diol (2), and (+/-)-1a,2,3,7b-tetrahydro-(1aalpha,7balpha)-naphth[1,2-b]oxirene (3) in 9:1 (v/v) aqueous Tris buffer-dioxane, at both acidic and neutral pH, with FMNH(2) and 1,5-dihydrolumiflavin (LFH(2)) gave (following covalent flavin-epoxide adduct formation) the products having a methylene group at the benzylic position. The reduction product yield was proportional to the yield of the N(5) flavin-epoxide adduct intermediate, and the rate of the reaction was proportional to the dihydroflavin concentration. These observations are consistent with these reduction products resulting from bimolecular reaction between the dihydroflavin-epoxide adduct and a second molecule of dihydroflavin. Copyright 2000 Academic Press.     

Aerobic microbial metabolism of some alkylthiophenes found in petroleum

Six alkylthiophenes, 2-hexadecyl-5-methylthiophene (I), 2-methyl-5-tridecylthiophene (II) and 2-butyl-5-tridecylthiophene (III), 2-(3,7-dimethyloctyl)-5-methylthiophene (IV), 2-methyl-5-(3,7,11,15-tetramethyl-hexadecyl)thiophene (V) and 2-ethyl-5-(3,7,11,15-tetramethylhexadecyl)thiophene (VI) were synthesized and used as substrates in biodegradation studies. The products of their aerobic metabolism by pure bacterial cultures were identified. In most cases, the long alkyl chains of these thiophenes were preferentially attacked and in pure cultures of alkane-degrading bacteria, the major metabolites that accumulated in the medium were 5-methyl-2-thiopheneacetic acid from (I), 5-methyl-2-thiophenecarboxylic acid from (II) and occasionally from (V), 5-butyl-2-thiophenecarboxylic acid from (III) and 5-ethyl-2-thiopheneacetic acid from (VI). These transformations are consistent with the metabolism of the alkyl side chains via the beta-oxidation pathway. In contrast, 5-(3,7-dimethyloctyl)-2-thiophenecarboxylic acid was produced from (IV). Because it was available in greatest supply, (I) was studied most thoroughly. It supported growth of the six n-alkanedegrading bacteria tested and (I) was degraded more quickly than pristance but not as quickly as n-hexadecance in mixtures of these three compounds. In the presence of Prudhoe Bay crude oil and a mixed culture of petroleum-degrading bacteria, the acid metabolites from (I), (II) and (III) underwent further biotransformations to products that were not detected by the analytical methods used. The addition of n-hexadecane to the mixed culture of petroleum-degrading bacteria also enhanced the further biotransformations of the metabolites from (I).     

Synthesis, structural characterization and biological study of new organotin(IV), silver(I) and antimony(III) complexes with thioamides

An overview of our work on the synthesis and biological activity of a series of tin(IV), silver(I) and antimony(III) complexes with thioamides is reported. Organotin(IV) complexes of formulae (n-Bu)2Sn(MBZT)2 (1), Me2Sn(CMBZT)(2) (2), {(Ph3Sn)2(MNA) (Me2CO)} (3), Ph3Sn(MBZT) (4), Ph3Sn(MBZO) (5), Ph3Sn(CMBZT) (6), Ph2Sn(CMBZT)2 (7) and (n-Bu)2Sn(CMBZT)2 (8), Me2Sn(PMT)2 (9), (n-Bu)2Sn(PMT)2 (10), Ph2Sn(PMT)2 (11), Ph3Sn(PMT) (12) {where MBZT=2-mercapto-benzothiazole, CMBZT=5-chloro-2-mercapto-benzothiazole, H2MNA=2-mercapto-nicotinic acid, MBZO=2-mercapto-benzoxazole and PMTH=2-mercapto-pyrimidine} were characterized by spectroscopic (NMR, IR, Mossbauer, etc.) and X-ray diffraction techniques and their influence on the peroxidation of oleic acid was studied. They were found to inhibit strongly the peroxidation of linoleic acid by the enzyme lipoxygenase. In addition, organotin(IV) complexes were found to exhibit stronger cytotoxic activity in vitro, against leiomyosarcoma cells, than cisplatin. The antiproliferative activity of the organotin complexes studied, against leiomyosarcoma cells follow the same order of LOX activity inhibition. This is, 3>12>7>6 approximately 8 approximately 10>5 approximately 4>2>9. Thus, among organotin(IV)-CMBZT complexes, 7 exhibits higher activity than the others and this is explained by a free radical mechanism, as it is revealed by an EPR study. The results are compared with the corresponding ones found for the silver(I) complexes of formulae complexes {[Ag6(mu3-HMNA)4(mu3-MNA)2](2-).[(Et(3)NH)+]2.(DMSO)2.(H2O)} (13), {[Ag4Cl4(mu3-STHPMH2)4]n} (14), {[Ag6(mu2-Br)6(mu2-STHPMH2)4(mu3-STHPMH2)2]n} (15), {[Ag4(mu2STHPMH2)6](NO3)4}(n) (16), {[AgCl(TPTP)]4} (17), [AgX(TPTP)3] with X=Cl (18), Br (19), I (20) (where STHPMH2=2-mercapto-3,4,5,6-tetrahydro-pyrimidine, TPTP=tri(p-toly)phosphine) and those of antimony(III) complexes {[SbCl2(MBZIM)4](+).Cl(-).2H2O.(CH3OH)} (21), {[SbCl2(MBZIM)4]+.Cl(-).3H2O.(CH3CN)} (22), [SbCl3(MBZIM)2] (23), [SbCl3(EMBZIM)2] (24), [SbCl3(MTZD)2] (25), {[SbCl3(THPMT)2]} (26) and {[Sb(PMT)3].0.5(CH3OH)} (27) (where MBZIM is 2-mercapto-benzimidazole, EMBZIM=5-ethoxy-2-mercapto-benzimidazole and MTZD is 2-mercapto-thiazolidine), which they have characterized with similar techniques as in case of organotin(IV) complexes. Silver(I) and antimony(III) complexes were found to be cytotoxic against various cancer cell lines.     

Formation of Glucose Isomerase by Streptomyces sp.

Sophoradin (I) [2′,4,4′-trihydroxy-3,3′,5-tris(3-methyl-2-butenyl)chalcone] which had been isolated from “Guang-Dou-Gen” (the root of Sophora subprostrata Chun et T. Chen) was synthesized through Claisen rearrangement. The reaction of p-hydroxybenzaldehyde and 3-chloro-3-methyl-1-butyne (III) gave 4-(1,1-dimethylpropargyloxy)benzaldehyde (VIII), which was catalytically hydrogenated over Lindlar catalyst to afford 4-(1,1-dimethylallyloxy)benzaldehyde (IX). IX was converted to 4-hydroxy-3-(3-methyl-2-butenyl)benzaldehyde (X) by Claisen rearrangement. The reaction of X and III gave 3-(3-methyl-2-butenyl)-4-(1,1-dimethylpropargyloxy)benzaldehyde (XI). Condensation of 2-hydroxy-4-(1,1-dimethylpropargyloxy)acetophenone (IV) and XI in alkaline solution gave a chalcone (XIII), which was catalytically hydrogenated over Lindlar catalyst to give 2′-hydroxy-4,4′-bis(1,-dimethylallyloxy)-3-(3-methyl-2-butenyl)chalcone (XIV). XIV was converted to I by Claisen rearrangement.     

Convenient synthesis of GOLD and MOLD and identification of their oxidation products in vitro and in vivo

Summary. Two Lys–Lys crosslinks, 1,3-bis-(5-amino-5-carboxypentyl)-1H-imidazolium (GOLD) and 1,3-bis(5-amino-5-carboxypentyl)-4-methyl-1H-imidazolium (MOLD) salts, have been synthesized by the reaction of imidazole or 4(5)-methyl imidazole with 5-(4-bromobutyl)-hydantoin followed by the hydrolysis of 1,3-substituted imidazolium derivatives by 6.0 N HCL at 110 °C. Treatment of GOLD and MOLD with hydrogen peroxide in acetic acid leads to MOLD oxidation only. The oxidation product of MOLD was detected in cataractous lens proteins.     

Spectroscopic and kinetic characterization of nonenzymic and aldose reductase mediated covalent NADP-glycolaldehyde adduct formation

Reaction of glycolaldehyde with the binary E-NADP complex of bovine kidney aldose reductase (ALR2) produces an enzyme-bound chromophore whose absorbance (lambd max 341 nm) and fluorescence (lambda ex max 341 nm; lambda emit max 421 nm) properties are distinct from those of NADPH or E.NADPH yet are consistent with the proposed covalent adduct structure [1,4-dihydro-4-(1-hydroxy-2-oxoethyl)nicotinamide adenine dinucleotide phosphate]. The kinetics of adduct formation, both in solution and at the enzyme active site, support a mechanism involving rate-determining enolization of glycolaldehyde at high [NADP+] or [E.NADP]. At low [NADP+] or [E.NADP] the reaction is second-order overall, but the ALR2-mediated reaction displays saturation by glycolaldehyde due to competition of the aldehyde (plus hydrate) and enol for E.NADP. Measurement of the pre-steady-state burst of E-adduct formation confirms that glycolaldehyde enol is the reactive species and gives a value of 1.3 x 10(-6) for Kenol = [enol]/[( aldehyde] + [hydrate]), similar to that determined by trapping the enol with I3-. At the ALR2 active site, the rate of adduct formation is enhanced 79,000-fold and the adduct is stabilized greater than or equal to 13,000-fold relative to the reaction with NADP+ in solution. A portion of this enhancement is ascribed to specific interaction of NADP+ with the enzyme since the 3-acetylpyridine analogue, (AP)ADP+, gives values that are 15-200-fold lower. Additional evidence for strong interaction of ALR2 with both NADP+ and NADPH is reported. Yet, because dissociation of adduct is slow, catalysis of the overall adduct formation reaction by ALR2 is less than or equal to 67-fold.     

The reaction of melphalan with deoxyguanosine and deoxyguanylic acid.

The reaction of melphalan (phenylalanine mustard, I) with 2'-deoxyguanosine, followed by removal of the sugar in acid, yielded two products. The major product was identified as 4-(N-(2-guanin-7-ylethyl)-N-(2-hydroxyethyl)amino)phenyl- alanine (II) by ultra-violet absorption, mass and NMR spectroscopy. The minor product has already been identified as the corresponding bis-guaninyl adduct III (Tilby et al., Chem.-Biol. Interact., 73 (1990) 183-194). The reaction of melphalan with 5'-deoxyguanylic acid yielded the deoxyribonucleotide of II and products resulting from reaction with the phosphate group. The initial products, which were formed with a half-life of approximately 40 min at 37 degrees, still had a reactive chloroethyl group; this was displaced more slowly, by reaction with water or with another molecule of dGMP. The products of reaction of melphalan with DNA were released by treatment with acid (0.1 M HCl, 70 degrees, 30 min) and separated from each other on a cation exchange column. They were identified as II, III and an adenine adduct, in a ratio of approximately 3:1:2.     

Reactions of sulfur-nitrosyl iron complexes of "g=2.03" family with hemoglobin (Hb): kinetics of Hb-NO formation in aqueous solutions.

NO-donating ability of nitrosyl [Fe-S] complexes, namely, mononuclear dinitrosyl complexes of anionic type [Fe(S2O3)2(NO)2]-(I) and neutral [Fe2(SL1)2(NO)2] with L1=1H-1,2,4-triazole-3-yl (II); tetranitrosyl binuclear neutral complexes [Fe2(SL2)2(NO)4] with L2=5-amino-1,2,4-triazole-3-yl (III); 1-methyl-1H-tetrazole-5-yl (IV); imidazole-2-yl (V) and 1-methyl-imidazole-2-yl (VI) has been studied. In addition, Roussin's "red salt" Na2[Fe2S2(NO)4] x 8H2O (VII) and Na2[Fe(CN)5NO] x H2O (VIII) have been investigated. The method for research has been based on the formation of Hb-NO adduct upon the interaction of hemoglobin with NO generated by complexes I-VIII in aqueous solutions. Kinetics of NO formation was studied by registration of absorption spectra of the reaction systems containing Hb and the complex under study. For determination of HbNO concentration, the experimental absorption spectra were processed during the reaction using standard program MATHCAD to determine the contribution of individual Hb and HbNO spectra in each spectrum. The reaction rate constants were obtained by analyzing kinetic dependence of Hb interaction with NO donors under study. All kinetic dependences for complexes I-VI were shown to be described well in the frame of formalism of pseudo first-order reactions. The effective first-order rate constants for the studied reactions have been determined. As follows from the values of rate constants, the rate of interaction of sulfur-nitrosyl iron complexes (I-VI) with Hb is limited by the stage of NO release in the solution.