Hydrogen sulphide as inhibitor and substrates for the cytochrome c-cytochrome c oxidase system /

It has previously been recognized that the major biochemical toxicity induced by sulphide is due to an inhibition of cytochrome ~ oxidase. Inhibition of this enzyme occurs at 30°C and pH 7.4 with a Ki of approximately 0.2 ~M, and a kon of 104 M-1 s-l, under catalytic conditions. However, the equimo1ar mixture of sulphide and the enzyme shows identical catalytic behaviour to that of the native enzyme. This cannot readily be attributed to rapid dissociation of sulphide, as both spectroscopic and plot analysis indicate the koff value is low. The addition of stoichiometric sulphide to the resting oxidized enzyme gives rise to the appearance of a low-spin ferric-type spectrum not identical with that seen on the addition of excess sulphide to the enzyme aerobically. Sulphide added to the enzyme anaerobically gives rise to another low-spin, probably largely ferric, form which upon admission of oxygen is then converted into a 607 nm species closely resembling Compound C. The 607 nm form is probably the precursor of oxyferricytochrome aa3. The addition of successive a1iquots of Na2S solution to the enzyme induces initial uptake of approximately 3 moles of oxygen per mole of the enzyme. Thus, it is concluded that: 1. the initial product of sulphide-cytochrome c oxidase interaction is not an inhibited form of the enzyme, but the low-spin (oxyferri) ~3+~+ species; 2. a subsequent step in which sulphide reduces cytochrome ~ occurs; 3. the final inhibitory step, in which a further molecule of sulphide binds to the cytochrome ~ iron centre in the cytochrome ~2+~+ species, gives the cytochrome a2+~+-H2S form which is a half-reduced fully inhibited species;4. a 607 run form of the enzyme is produced which may be converted into a catalytically active low-spin (oxyferri) state; and therefore 5. liganded sulphide may be able to reduce the cytochrome 33 -Cu centre without securing the prior reduction of the cytochrome a_ haem group or the Cud centre associated with it.

Kinetic studies of the effect of organic sulphides on the oxidation of other sulphides /

The rates of oxidation of three Organic sulphides viz. methyl phenyl sulphide, (P), p -me thoxyphenyl methyl sulphide (M) and methyl p-nitrophenyl sulphide (N). have been obtained in ethanol using MoO-(acac)- as catalyst and Bu OOH as the oxidizing agent. A Hammett plot gave a rho value of -2.1 and the activation energies for the oxidation of P, M and N were estimated to be 63.60, 40.12 and 197.46 Kj mol respectively. The effect of organic sulphide on the oxidation of another sulphide was also ascertained. Positive and negative deviations were observed from the expected slope.

Genesis and distribution of Mississippi Valley-type ore assemblages in Middle Silurian strata, Niagara Peninsula, Ontario /

Presently non-commercial occurrences of Mississippi Valley-type ore assemblages in the Middle Silurian strata of the Niagara Peninsula have been studied. Based on this detailed study, a new poly-stage genetic model is proposed which relates ore mineralization in carbonate environments to the evolution of the sedimentary basin. Sulphide ore mineralization occurred during two episodes: 1. During the late diagenesis stage, which is characterized by compaction-maturation of the sediments, the initial mineralization took place by upward and outward movement of connate waters. Metals were probably supplied from all the sediments regardless of their specific lithologies. However, clay minerals were possibly the main contributors. The possible source of sulphur was from petroleum-type hydrocarbons presently mixed with the sediments at the site of ore deposition. Evidence for this is the fact that the greatest abundance of ore minerals is in petroliferous carbonates. The hydrocarbons probably represent liquids remaining after upward migration to the overlying Guelph-Salina reservoirs. The majority of sphalerite and galena formed during this period, as well as accessory pyrite, marcasite, chalcopyrite, chalcocite, arsenopyrite, and pyrrhotite; and secondary dolomite, calcite, celestite, and gypsum. 2. During the presently ongoing surface erosion and weathering phase, which is marked by the downward movement of groundwater, preexisting sulphides were probably remobilized, and trace amounts of lead and zinc were leached from the host material, by groundwaters. Metal sulphides precipitated at, or below, the water table, or where atmospheric oxygen could raise the Eh of groundwaters to the point where soluble metal complexes are unstable and native sulphur co-precipitates with sphalerite and galena. This process, which can be observed today, also results in the transport and deposition of the host rock material. Breakdown of pre-existing sulphide and sulphate, as well as hydrocarbon present in the host rock, provided sulphur necessary for sulphide precipitation. The galena and sphalerite are accompanied by dolomite, calcite, gypsum, anglesite, native sulphur and possibly zincite.

An investigation into the oxidation of organic sulphides, organic selenides and simple hydrocarbons by Mortierella isabellina NRRL 1757

The work presented in this thesis is divided into three separate sections 4!> Each' 'section is involved wi th a different problem, however all three are involved with a microbial oxidation of a substrate~ A series of 'aryl substituted phenyl a.nd be,nzyl methyl sulphides were oxidized to the corre~pondi~g sulphoxides by 'Mo:rtierellai's'a'b'e'llina NRR.L17'S7 @ For this enzymic Qxidation, based on 180 labeled experiments, the oxygen atom is derived fr'orn the atmosphere and not from water. By way of an u~.traviolet analysis, the rates of oxidation, in terms of sulphox~ de appearance, were obtained and correlated with the Hatnmett p s~grna constants for the phenyl methyl sulphide series. A value of -0.67 was obtained and, is interpreted in terms of a mechanism of oxidation that involves an electrophilic attack on the sulphide sulphur by an enzymic ironoxygen activated complex and the conversion of the resulti!lg sulphur cation to sulphoxide. A series of alkyl phenyl selen~des have been incubated with the fu~gi, Aspergillus niger ATCC9l42, Aspergillus fO'etidus NRRL 337, MIIJisabellina NF.RLl757 and'He'lminth'osparium sp'ecies NRRL 4671 @l These fu?gi have been reported to be capable of carrying out the efficient oxidation of sulphide to sulphoxide, but in no case was there any evidence to supp'ort the occurrence of a microbialox,idation. A more extensive inves·t~gation was carried out with'M,e 'i's'a'b'e'l'l'i'na, this fu~gus was capable of oxidizing the correspondi~g sulphides to sulphoxi.de·s·$ Usi:ng a 1abel.edsubstra.te, [Methyl-l4c]-methyl phenyl selenide, the fate of this compound was invest~gated followi!lg an i'ncubation wi th Me isabellina .. BeSUldes th. e l4C-ana1YS1Q S-,'. a quant"ltta"lve selen'lum ana1Y"S1S was carried out with phenyl methyl selenide. These techniques indicate that thesel'enium was capable of enteri!1g thefu!1gal cell ef'ficiently but that s'ome metabolic cleav~ge of the seleni'um-carbon bond' may take plac'e Ie The l3c NMR shifts were assigned to the synthesized alkyl phenyl sulphides and selenides@ The final section involved the incubation ofethylben~ zene and p-e:rtr.hyltoluene wi th'M ~ 'isab'e'llina NRRL 17574b Followi~ g this incubation an hydroxylated product was isolated from the medium. The lH NMR and mass spectral data identify the products as I-phenylethanol and p-methyl-l-phenylethanol. Employi!lg a ch'iral shift re~gent,tri~ (3-heptafluorobutyl-dcamphorato)'- europium III, the enantiomeric puri ty of these products was invest~gated. An optical rotation measurement of I-phenylethanol was in ~greement with the results obtained with the chiral shift re~gen,te 'M.isabe'l'lina is capable of carryi~g out an hydroxylation of ethylbenzene and p-ethyltoluene at the ~ position.

Synthesis and properties of some 4H-1, 3, 4 benzothiadiazines /|nby Darko J. Vukov. -- 260 St. Catharines, Ont. : [s. n.],

The work herein has been divided into five sections. In the first section, a new method of converting N-aroyl- hydrazines to hydrazidic halides is described. The second section deals with the products of reaction of hydrazidic halides with thioacetate ion in acetonitrile at room temperature. A number of new acetylthiohydrazides has been isolated together with corresponding hyclrazidic sulphides. Examination of x-ray data for bis-[~ -(2,6- dibromophenylhydrazono) - benZYl] sulphide revealpd the symmetrical structure as the most probable. In the third section, which consists of the three subsections, the synthesis of the 4H-l,3,4 benzothiadiazine ring system has been extended to 4H-l,3,4 benzothiadiazines with substituents in the 5 and 6-positions. Extension of synthesis also involves 4H-l,3,4 benzothiadiazines with mora than one substituent. Nuclear magnetic resonance spectra of 5 and 6 substituted 4H-l,3,4 benzothiadiazines have been ,. recorded. The section ends with a discussion of the mass spectra of some 4H-l.3,4 benzothiadiazines. In the fourth section, which is divided into two sub- -sections, preparation of 7-nitro substituted 4H-l,3,4 benzothiadiazine from N-thiobenzoyl hydrazine and2,4-dinitro -fluorobenzene is found to be satisfactory. Thiohydrazides react with acetic anhydride, in some cases, to give products identical with acetylthiohydrazides obtained from the hydrazidic halides with thioacetate ion at room temperature. In most of the cases thiohydrazides are found to give anomalous products on reaction with acetic anhydride and mechanisms for their formation are discussed. In the fifth section, which forms three subsections, the 4H-l,3,4 benzothiadiazine ring system with a halogen substituent in the 7-position undergoes electrophilic attack preferentially in 5-posi tion. \fuen the 5-posi tion is occupied by a halogen atom, electrophilic substitution occurs at the 7-position of 4H-l,3,4 benzothiadiazine ring system. Substitution at the 4-nitrogen atom in 4H w l,3,4 benzo- -thiadiazine is extremely slow, probably due to delocalisa- -tion of the nitrogen lone pair in the system. Oxidation of 4H-l,3,4 benzothiadiazines occurs at the sulphur atom under relatively mild conditions. t The Appendix deals with the reaction of N-benzoyl-N - -(2,5-dibromophenyl)hydrazine with p-nitrothiophenol~ The proposed p-nitrothiophenoxy - intermediate may undergo benzothiadiazine formation in a proton exchange system.

The suppression of the Haller-Bauer scission for synthetic purposes /|nby S. M. Vines. -- 260 St. Catharines, Ont. : [s. n.],

A number of 2-chlorobenzophenones, containing electron releasing groups (e.g. hydroxy, thiomethoxy and methoxy) in the 4' - position, were prepared by the Friess rearrangement, or the Friedel-Crafts reaction. These ketones, when treated with potassamide in liquid ammonia, underwent partial Haller-Bauer scission, unlike 2-chlorobenzophenone which is known to undergo complete scission. Under similar conditions 4-nitrobenzophenone also underwent partial scission, but the main reaction in this case was nucleophilic amination of the nitro containing ring. This amination reaction was shown not to be a useful general reaction for aromatic nitro compounds. 3-Methylxanthone was then prepared by treatment of 2- and 3- chloro-2'-hydroxy-5'-methylbenzophenone with . little, if any, attendant scission. The corresponding 2fluoro- compound also gave the xanthone, but as the 3-fluoro compound did not, it was concluded that the 2-fluoro compound reacted through a nucleophilic substitution mechanism, rather than the benzyne mechanism invoked for the chloro and bromo compounds. 3-Methylthioxanthone was synthesised by treatment of methyl 4-tolyl sulphide and 2-chlorobenzoyl chloride with aluminum chloride in carbon disu1phide, followed.by heating. This compound was also prepared by treatment of 3-chloro-2'thiomethoxy- 5'-methylbenzophenone with potassamide in liquid ammonia.