Takao Kwan

Chemical Methylation of Inorganic Mercury with Methylcobalaiin, a Vitamin B12 Analog

Chemical methylation of mercuric chloride with methylcobalamin has been studied. Methylated mercury was detected by gas chromatography; and analysis of the products of the reaction by thin-layer chromatography revealed that the methylation proceeded at a remarkably high rate when methylcobalamin and inorganic mercury were mixed. Dimethylmercury was an initial product of the reaction.

Esr studies on the reactive character of the radical anions, so−2, so−3 and so−4 in aqueous solution

Abstract The reactive characteristics of the oxy anion radicals of sulphur, SO−2, SO−3 and SO−4 were investigated by use of the rapid-mixing flow technique coupled with electron spin resonance (ESR) which can detect the radicals having a lifetime of 5–100 msec. The SO−2 reduced the aromatic nitro compounds to the corresponding anion radicals, but did not abstract the hydrogen from the saturated compounds nor add to the unsaturated compounds. The SO−3 could add to the compounds having CC bond, but did not abstract the hydrogen from the saturated compounds nor reduce the aromatic nitro compounds. The SO−4 could abstract the hydrogen from the saturated compounds and also add to the unsaturated compounds having CC bond, but did not reduce the aromatic nitro compounds. These differences of the reactivity towards the organic substrates were discussed on the basis of the difference in the distribution of the unpaired electron density of each radical anion.

Electron spin resonance investigation of electrical conductivity parameters of zinc oxide during surface reactions

Abstract The effect of the electron transfer process between the bulk and surface of ZnO upon oxygen sorption was investigated by measuring the changes of the following ESR parameters: the spin densities of the g = 1.96 and g ~ 2.0 signals, the intensity of a Mn 2+ reference sample, and the crystal current of the microwave detector. The approach was also used to investigate the relative density of conduction electrons in mixtures of copper in ZnO. A theory was developed to show that these ESR parameters may be used to describe the density of electrons in the conduction band of ZnO, and the theory was applied to the results of oxygen sorption on ZnO. Evidence is presented which shows that the g = 1.96 signal of ZnO should probably be assigned to electrons in the conduction band and not to electrons in donor states. Application of this ESR approach in investigations of heterogeneous catalysis, particularly oxidation reactions, is discussed.

ESR studies on the reactions of sulphite radical anion, SO3.̄−, with nitroalkane compounds in aqueous solutions

Abstract The reactions of the sulphite radical anion, SO 3 . − (generated from the Ti 3+ -H 2 O 2 -Na 2 SO 3 system at pH 9), in aqueous solutions with some nitroalkane compounds were investigated by using a rapid-mixing flow technique coupled with electron spin resonance (ESR) which can detect the radicals having a lifetime of 5–100 ms. The SO 3 . − radical added to the double bond of CN in the nitroalkane aci -anions which are the main form of nitroalkanes in aqueous alkaline solutions. From the observed hyperfine splitting constants of the SO 3 . − adducts of nitroalkane aci -anions, the preferred conformation of the adducts was deduced.

Magnetic circular dichroism on the reversible oxygenation of dimethylmesoporphyrin-IX-atopyridinecobalt (II).

The magnetic circular dichroism spectra were measured for the dimethylmesoporphyrin-IX-atocobalt complexes. As expected dimethylmesoporphyrin-IX-atocobalt (III) and its pyridine complex exhibited the MCD for a typical D4h metalloporphyrins. Dimethylmesoporphyrin-IX-atocobalt (II) and its pyridine complex showed a paramagnetic effect on the MCD especially in the Soret region. A very atypical Soret MCD for the oxygenated dimethylmesoporphyrin-IX-atopyridinecobalt (II) was attributed to the existence of a CT band associated with oxygen from the similarity to the MCD for oxymyoglobin. Temperature-dependent MCD change for the cobalt (II) oxygen complex revealed the reversible oxygen binding to dimethylmesoporphyrin-IX-atopyridinecobalt (II) with KO2 of 3.2 X 10(-3) in (mmHg)-1 at 228 degrees K.

A convenient preparation of the e.s.r marker, nitrosodisulphonate radical anion (Fremy's salt)

The nitrosodisulphonate anion radical, ·ON(SO3–)2, has been prepared by air oxidation of an equimolar mixture of NaNO2 and NaHSO3 in alkaline aqueous solution; this radical anion, known as Fremys salt, is a good marker for e.s.r. spectroscopy.

E.s.r. evidence for the formation of new vinyl radicals in solution

The new vinyl radicals HC(SO3–)ĊCMe2OH, HC(SO3–)ĊCH2OH, and HC(SO3–)ĊCH(Me)OH were observed during the reactions of the SO3– radical with the corresponding alkynes 3-methylbut-1-yn-3-ol, prop-2-ynyl alcohol, and but-1-yn-3-ol, respectively, by use of an e.s.r. method coupled with a rapid-mixing flow technique which allows the detection of radicals having life-times of 5–100 ms.

E.s.r. studies for chemical modification of biologically active nucleic acids by the sulphite radical anion, SO3–

The addition of the sulphite radical anion, SO3–, [generated from the system Ti3+–ethylenediaminetetra-acetic acid–hydrogen peroxide–sodium sulphite in aqueous alkaline solution at pH 9] to uracil derivatives such as 2-thiouracil and 6-methyl-2-thiouracil was observed by use of an e.s.r. method coupled with a rapid-mixing flow technique, indicating that the SO3– radical is one of the active agents for the chemical modification of biologically active nucleic acids by the hydrogen sulphite ion.

Spin Label Measurement of Platelet Alignment in a Clot Induced by Isometric Tension

A spin label technique was applied to examine the alignment of platelet membranes in the platelet-fibrin clot. The ESR spectrum of the clot in the control experiment was typical of isotropically oriented membranes, while the ESR spectrum of the clot which was kept isometric was quite different from that of the control experiment. These spectra were simulated with a computer and explained to indicate that the shape of platelets in the clot was transformed to a cylindrical form under the isometric tension so that axes of all membrane cylinders were directed parallel to the generated force.

Orientation of platelets on the surfaces of glass and Teflon plates as studied by a spin label technique.

Platelets were found by a spin label technique to orient on flat surfaces of glass as well as of Teflon. This kind of platelet orientation was not caused by centrifugation or partial dehydration of the membrane preparation as employed usually to make oriented planar multilayers of biological membranes on the surface of a supporting plate (1-8), but was considered to be closely related to the adhesion or the aggregation properties of platelets. The amount of oriented platelets varied depending on the platelet treatment and was estimated from a computer simulation of the observed ESR spectra to be about one-half of that of the non-oriented ones in the case of thrombin-treated platelets. This technique may be useful as a new tool to explore the adhesion or aggregation properties of platelets.