Volume 27, Issue 1

Expressions are reviewed which may be used to determine 10 Dq and B from the spin-allowed bands in the optical spectra of d 3 and d 7 electron systems within octahedral and tetrahedral sym metry. Application to low-temperature single crystal spectra demonstrates that (i) the semi-empirical ligand field theory reproduces transition energies with sufficient accuracy; (ii) differences in the values of 10 Dq and B observed with different fitting methods may be attributed to the inaccuracy of experimental data; (iii) there are generally valid values of B 35 and β 35 for each complex ion.

In this paper we described a method how to calculate from NMR the association - caused by Η-bonds - of two components. These components may be present in equal concentration and may be partially self-associated. The may act as Η-donors and acceptors. The method is demonstrated using some nucleoside derivatives as examples.

The co-assoziation of four nucleoside-derivatives was investigated using NMR spectroscopy. It turned out that the constant of co-association is at least ten times as great as the value for selfassoziation it a Watson-Crick pair was used. Thermodynamic data were calculated from the temperature dependence of the assoziation constant.

The Raman and infrared spectra of MoO 3 ·2 H 2 O and MoO 2 Cl 2 · H 2 O have been assigned based on the known crystal structures of these compounds. In the region of the Mo-O-stretching frequencies the spectra of ΜοO 3 ·2Η 2 O and MoO 2 Cl 2 or WO 2 Cl 2 are very similar. The same is valid for MoO 2 Cl 2 H 2 O compared with MoO 3 . The frequency νas (Mo-O - Mo) depends highly on the ratio of the bond lengths of the two bridge bonds.

S = salicylaldehyde and benzoylacetone and B = (CH 2 -) 2 , -CH 2 -CH -CH 3 and C 6 H 5 ) in different stoichiometric ratios have been synthesised. The products Al (OPr i ) (SB) are soluble in benzene. The tertiary butoxy products have been prepared by the alcohol interchange technique. Infrared spectra of the new derivatives are reported. Thermogravimetric analyses have also been carried out.

In the γ-radiolysis of N 2 O saturated aqueous solutions of meso-erythritol (10 -2 mol/1) the following products (G-values) are formed: erythrose (1) (1.3), erythrulose (2) (1.4), 2-deoxy-tetrose (3) (0.70), butanediol- (3,4)-on- (2) (4) (0.75), butanediol- (1,4) -on- (2) (5) (~0.1), glycerol aldehyde (6) (∼0.1), glycol aldehyde (?) (7) (<0.1) and dimers (8) (0.45). The formation of the products can be explained by the attack of the water radicals (OH and H) on the meso-erythritol to give primarily meso-erythritol radicals. These radicals may disproportionate (products: 1 and 2), eliminate water, or fragment. The dimers 8 and the products 3-5 contain deoxy-groups attached to a carbonyl function. Their precursors are meso-erythritol radicals which have split off water before dimerization or disproportionation. 6 and 7 seem to arise from β-fragmentation processes of the primary meso-erythritol radicals.

In the 185 nm photolysis of liquid O 2 -free isopropanol the following products (quantum yields) are formed: hydrogen (0.75), acetone (0.72), pinacol (0.03 6 ), methane (0.04 6 ), acetaldehyde (0.04), propane (0.02 β ), ane (0.002 3 ) and carbon monoxide (0.001 5 ). A detailed reaction scheme is proposed. The major primary processes are the formation of H-atoms by homolytic scission of the O —H-bond (61 — 69%), elimination of molecular hydrogen (21%) and molecular methane (5%). Φ(Η 2 ) is strongly decreased by adding water which does not absorb an appreciable portion of the 185 nm light in the mixtures down to 1 mole/l isopropanol (Φ(Η 2 ) =0.21). In contrast to the strong effect of water there is no effect on Φ(Η 2 ) by diluting isopropanol with n-hexane. From experiments with isopropanol-OD and 2-deutero-isopropanol it is tentatively concluded that H-atoms stemming from the O—H-group of the alcohol are to about 65% the precursors of the hydrogen in these mixtures.

The oxidation of cyclohexanol by ceric ion has been studied in the presence of nitric acid (~1-2.5 M). The rate dependence on alcohol suggests intermediate complex formation. The increase in hydrogen ion and nitrate ion concentrations retards the rate of oxidation. The results have been explained on the basis of Ce (OH) 3⊕ , as the reactive species. The value of K h for the equilibrium Ce 4⊕ +H 2 O ⇄ Ce (OH) 3⊕ +H ⊕ has been evaluated as 4.8 at 25°C in nitric acid medium. A mechanism based on decomposition of Ce (IV) -alcohol complex and rupture of α-carbon hydrogen bond in the rate determining step has been put forward.

The microsomal UDP glucuronyl transferase exhibits activities against hydroxy derivatives of androstenedione (hydroxyl groups in the positions 2β, 6β or 16α) between 5% and 27% of the extent shown against testosterone. 2β-, 6β· and 16α-hydroxyl groups are much less efficient in accepting the glucuronic acid than the 17β-hydroxyl group. However, the acceptor function of the 17β-hydroxyl group is restricted by other hydroxy substituents in the testosterone molecule to an increasing extent represented by the following sequence: 2α, 6β, 6α, 16α, and 7α. A special case is represented by 2β-hydroxy-testosterone. The transferase displays a higher activity against this compound than against testosterone. Apparently the transferase approaches the steroid molecule from the α-side (with the β-side there is also contact at the C-6 atom) requires the 17β-hydroxyl group and the 3-oxo-4-ene system to display full activity. Thus the very high specificity of the transferase for testosterone explains the selective action of this enzyme on testosterone metabolism in the liver. This action is expressed by the fact, that in liver perfusates the percentage of testosterone in the glucuronide fraction is twice as large as the percentage of testosterone in the free steroid fraction.

When Euglena gracilis was grown under white (fluorescent) light in media containing high concentrations of ammonium chloride (more than 0.005%), the main lipids synthesized were monogalactosyl diglyceride, digalactosyl diglyceride, phosphatidyl glycerol, sulfolipid and the all cis △7,10-16:2, △7,10,13-16:3, △4,7,10,13-16:4, △9,12-18:2 and △9,12,15-18:3 fatty acids. At low levels of ammonium (less than 0.002%) these compounds were produced only in small amounts, while neutral lipids, phosphatidyl choline, phosphatidyl ethanolamine and the 14:0, 16:0 and 16:1 fatty acids predominated. When Euglena gracilis was grown in white light in the presence of dichlorophenyldimethylurea (DCMU) or in the dark, fatty acid and lipid biosyntheses followed the same pattern as in white light at low levels of ammonium. Similar results were obtained when nitrate served as the only nitrogen source in the light and in the dark. The results indicate that in Euglena gracilis there are a light independent and a light and ammonium dependent pathway of fatty acid biosynthesis. Both pathways seem to be in association with specific lipids.

The stationary intracellular potassium concentration in E. coli B 525 has been studied as a function of the extracellular potassium and sodium concentrations. The ratio of extracellular to intracellular potassium concentration is shown to be a linear function of the extracellular potassium concentration if the extracellular sodium concentration is low (20 mmoles/l). In the case of high sodium concentration (100 mmoles/l) the ratio is independent of the extracellular potassium concentration if the potassium concentration is below 1,2 mmoles/l. In order to describe the distribution of potassium uniformly over the whole range of the extracellular potassium and sodium concentrations a carrier system with two sites has to be supposed.

1. Crosses between wild type (dark ascospores) and the asco-mutant (light ascospores) were set up and the spores collected as unordered octads. The analysis of 1317 such octads revealed 69 with abnormal segregation of the asco-marker (5.2%). If crosses were irradiated with UV at a dose equivalent to 66% conidial killing, an increase of the number of aberrant octads was found. This increase was most pronounced if the crosses were exposed to the irradiation from one day before to 2 days after plasmogamy, when up to 8.7% aberrant octads were obtained. No effect was observed from 4 days after plasmogamy until the end of the sexual cycle. 2. The relative frequency of the 8 possible types of aberrant octads was analyzed separately for experiments without and for experiments with UV-irradiation. The distribution of these frequencies was the same for unirradiated and irradiated crosses, a finding which suggests that the conversion mechanism acting spontaneously and that acting upon UV-irradiation may be identical. In both cases, there was a strong bias in favour of octads of the 2 : 6 type (giving wild spores first) as compared to such of the 6: 2 type, also the frequency of the 0 : 8 type was higher than that of the 8 : 0 type. Hence, the conversion mechanism in this cross “prefers” to act from the wildtype to the mutant allele.

The specific effect of the extract from the fruit pulp of Citrullus lanatus was demonstrated on the seed germination and seedling growth of Citrullus lanatus, Citrullus colocynthis and Pennisetum typhoideum. The extract from C. lanatus inhibited the germination of its own seeds, but promoted that of the other two species. The promoting substance for the growth of root and shoot was found at R f 0.66.