Polarographic Studies on Sarkomycin

By polarography, isoniazid (INH) gives three reduction waves and sarkomycin-isoniazid derivative (SK-INH) gives three or four waves. Polarography of the mixtures of two out of sarkomycin (SK), INH and SK-INH suggests that the first, the second and the fourth wave of SK-INH are derived from the first, the second and the third wave of INH, respectively, and the third wave from SK. Alternating current polarography of SK-INH shows three or four maxima, whose numbers are the same as wave numbers in direct current polarography.     

Polarographic Studies on Fat-soluble Vitamins in Nonaqueous Media

Each of reduction-polarograms of vitamin A-alcohol, -palmitate and β-carotene showed three steps in 60 vol% benzene-acetonitrile mixture containing 0.1 M-tetrabutylammonium iodide. The first half-wave potentials were determined at -1.41 V vs. Hg-pool for the alcohol, -1.23 V for the palmitate and -1.02 V for β-carotene. The second half-wave potentials were determined at -1.65 V identically for first two vitamins and -1.67 V for β-carotene. The third waves were raised at ca. -2.0 V but were quite ill-defined. All of the first and the second waves were controlled by diffusion and those wave-heights were proportional to concentrations of the vitamins and β-carotene in the range from 5×10^-5M (ca. 50 IUA?ml^-1) to 10^-3 M (ca. 1000 IUA?ml^-1).

Calculations with Ilkovic Eqn. and Perrin Eqn. gave n≈4 for the first and the second waves of β-carotene, and n≈2 for those of vitamin A and its palmitate.

A preliminary study on vitamin A-acetate was also made under the same experimental conditions. The first and the second half-wave potentials of vitamin A-acetate were -1.26 V and -1.66 V vs. Hg, respectively, and the proportionalities between wave-heights and concentration were held in the same concentration range as above.     

Polarographic Studies on Fat-soluble Vitamins in Nonaqueous Media

Polarographic reduction-wave of vitamin K₃ showed two inflexions in acetonitrile as solvent. The first step inflexion is caused by reduction of quinone to semiquinone stabilized as anion free-radical in acetonitrile, and the second by reduction of semiquinone to hydro-quinone dianion. With small addition of water, the dismutation of semiquinone is accelerated and the reduction-wave becomes only one step inflexion. The reduction-wave in acetonitrile is controlled by diffusion. The total wave-h eight is strictly proportional to the concentration of vitamin K₃. The measurement is not disturbed by coexistent fatty substances.     

Polarographic Studies on Fat-soluble Vitamins in Nonaqueous Media

Vitamin D₂ and vitamin D_s gave a single reduction-wave, respectively, in polarography in acetonitrile containing 0.05 M-tetrabutylammonium iodide. The eduction-wave of vitamin D_s was indistinguishable from that of vitamin D₂, whose half-wave potentials were evaluated identically at -2.1₀ V vs. Hg. Proportionalities between wave-height and concentration were held in the concentration range fronl 4× 10^-4 M (ca. 6000 IU·ml^-1) to 1.2×10 M (ca. 18000 IUD·ml^-1)

In both cases, the conjugated three double-bond system may be reduced to two double-bond system, which corresponds to the third reduction-step of vitamin A.

Ergosterol which has a conjugated two double-bond system and an isolated double-bond gave no reduction-wave under the present conditions.     

Polarographic investigation on tetrazolium reductase activity

Summary An attempt was made to elaborate a simple method of tetrazolium reductase activity assay in biological material. The method is based on recording of changes in the amperage of threshold current, occuring in course of the reduction of tetrazolium salts. — The method could be employed by histochemists working on the reduction of tetrazolium salts.     

Polarographic study of mitochondrial suspensions

• 1.1. Mitochondrial suspensions exhibit a characteristic polarographic wave which is independent of tissue source. This same wave was found in the mitochondria of two species of animals.
• 2.2. This polarographic wave is anodic in character, irreversible, and diffusion controlled.
• 3.3. The anodic process results in the formation of a mercury mercaptide. The source of mercaptan in fresh mitochondrial preparations is sulfhydryl groups within the mitochondrial membrane. These appear to be due to sulfhydryl groups contained in the protein structure of the mitochondrial membrane.
• 4.4. Aging of the mitochondrial preparation results in loss of the early wave and the appearance of a second wave. This latter wave originates from the contents of the mitochondria.
     

The Polarographic Determination of Phosphate

A method is described for estimating polarographically the amountof phosphate in small volumes of liquid, where the phosphoruscontent lies between 0.5 and 10.5 µg. P/ml. with an errorof ± 0.2 µg. P/ml. even when chloride, nitrate,and sulphate are present in excess. The method is based on precipitationof uranyl phosphate from uranyl acetate and estimation of theuranyl ion left in solution. A comparison is made with the colorimetric method of Berenblumand Chain.     

Polarographic reducibility of denatured DNA

The de polarographic behavior of native and denatured DNA at pH 7.0 was studied. Whereas native DNA was polarographically inactive under the given conditions, denatured DNA yielded a reduction polarographic step at the potential of about ?1.4 V. Native DNA produced a single desorption wave on ac polarograms, while denatured DNA yielded, in addition to this wave, another more negative wave approximately corresponding, as to its potential, to the dc polarographic step of denatured DNA. The behavior of apurinic acid was similar to that of denatured DNA. The course of DNA denaturation at elevated temperature was studied by means of the two above techniques and changes at temperatures below the melting temperature observed. This finding is in agreement with earlier results obtained by oscillopolarographic and the pulse-polarographic method.     

Polarographic determination of superoxide dismutase.

A polarographic procedure is described which allows determination of the catalytic constants for superoxide dismutase-catalyzed reactions. The method presents a single and rapid evaluation of the enzyme concentrations as well as determination of its activity under different conditions; e.g., pH between 9 and 13, presence of urea, guanidine, sodium dodecyl sulphate and inhibitors such as CN^? and N₃^?.The results fit very well with data previously obtained with other methods and show that this polarographic procedure can be used under conditions that render the other methods unsuitable for the measurement of the enzyme activity.     

Polarographic studies on the peroxidase activity of liganded deuterohemin]

The peroxidase activity of deuterohemin and deuterohemin complexes relative to the substrates pyrogallol and ascorbic acid was studied using d.c. polarography in aqueous solution. Imidazole and pyridine served as complex ligands. In the absence of the ligands, a continual rise in the substrate conversion rate with increasing H2O2 initial concentration is observed. Imidazole or pyridine were found to considerably increase the peroxidase activity of deuterohemin at low H2O2 concentrations. At high H2O2 concentrations, the dependence of the reaction rate on H2O2 concentration shows a bend, the reaction rate being in each case higher than that of free hemin under the same conditions. The reason of this fact is discussed to be a retarded formation of activated H2O2 hemin-ligand complexes at high H2O2 concentrations.