Band 32, Heft 9-10

The structure of β-ᴅ-1,3 xylan has been studied in detail. Atomic coordinates in the unit cell are determined. A method for calculating structure factors for the triple helical structure of β-ᴅ-1,3 xylan which is suitable for com puter and which avoids Bessel function is described. The structure is further refined by least square method. The R-value and Φ-value are minimized at 0.41 and 4.417.

Statistical Layer Shift, α-Chitin The intensities scattered by antiparallel/parallel layers were calculated. Difference synthesis maps allowing for statistical layer shifts were computed for a-chitin. The results support the view that there may be antiparallel sequence with each layer displaced at random by +e or -e from a halving position in the ϰ-direction. This is supported by greater breadth of certain reflection of the type lkl compared to 0kl on the X-ray diffraction photograph. This gives strong evidence for some imperfection in the ϰ-direction and the proposed indeterminacy + e is one possible way in which this might arise.

(-) Cyclophosphamide (1) crystallized from tetrachlorom ethane in the triclinic space group P1 with cell dimensions a = 10.500 (4) Å, b = 10.490 (4) Å, c = 10.761 (4) A, α = 110.0 (2) ° , β = 11 0.0(2)°, γ = 1 0 8.9(2)°. Three molecules are contained in the unit cell. The X-ray analysis was based on diffractometer measurement of 2635 independent reflections and the structure was solved by Patterson and direct methods. The final R and R w factors after full-matrix least-squares refinement are 0.0717 and 0.0677, respectively. The absolute configuration is S based on Hamilton’s R-factor ratio test. The oxazaphosphorinane ring exists in a chair form with the bis-β-chloroethyl-amino group in equatorial position and about perpendicular to and bisecting . The structure is similar to that found in racemic 1 except a different conformation about one ethyl-amino N-C bond.

Mezerein, Daphne mezereum, X-Ray Structure, Antileukemic Principle The X-ray structure of Mezerein from Daphne mezereum L. was determined by aid of direct methods. Comparison with Phorbol and Daphnetoxin led to the absolute configuration. A tentative mechanism for the antileukemic activity is proposed.

Myoglobin, Mössbauer Spectroscopy, Recombination Kinetic Myoglobin-CO (MbCO) has been photodissoziated with white and monochromatic light at low temperatures (5-40 °K). The photoproduct Mb* was identified with Mössbauer spectroscopy as ferrous high-spin complex, with isomer shift and quadrupole splitting, which are similar to the corresponding parameters of deoxymyoglobin. From the time-dependent change of the linewidth of the Mb*-Mössbauer-spectrum at 5 °K over a time-intervall of 7 hours we conclude, that there exist several slightly different Mb*-conformations with different recombination characteristics. In order to obtain a convenient time resolution of the recombination behavior, we investigate the time-dependence of one of the Mb*-absorptionlines with a Mössbauer drive of constant velocity. The resulting recombination data then are analzyed in various steps of approximation. It is shown that at least two independent exponentials are necessary for the interpretation of experimental data. The attempt to interprete the experimental data on the basis of distribution of energies is in qualitative agreement with corresponding results, which are derived from optical recombination data by Austin et al. Typical activation energies for the recombination process CO → Mb* are 2 kcal/mol. At low temperature (T < 46 °K) the recombination behavior is explained by quantum-mechanical tunneling.

The hydrochlorides from tetracycline and six tetracycline derivatives *-7-dimethylamino-6-des-methyl-6-desoxytetracycline [minocycline], 7-chlorotetracycline [chlorotetracycline], 7-chloro-anhy-drotetracycline [anhydrochlorotetracycline, 7-chloro-6-desmethyltetracycline [demethylchlorotetra- cycline], 5-hydroxytetracycline [oxytetracycline] and 6-desoxy-5-hydroxytetracycline [doxycycline] - were reacted with different amounts of sodium nitrite at 37 °C for two hours in aqueous buffer solutions at pH 2 and 4. Dimethylnitrosamine formation was confirmed by gas-liquid chromatography and by combined gas-liquid chromatography/mass-spectrometry from minocycline, doxycycline, oxytetracycline and an- hydrochlorotetracycline. Dimethylnitrosamine formation from minocycline and doxycycline was blocked by ascorbic acid. The catalytic effect of sodium thiocyanate for the dimethylnitrosamine formation from minocycline and nitrite was investigated. The different reactivity of the investigated tetracycline derivatives towards nitrite in acidic solutions is discussed by stereochemical considerations in connection with the formation of hydrogen bridge linkages. This hypothesis was confirmed by dimethylnitrosamine formation from anhydro-chlorotetracycline and sodium nitrite at pH 2.

The content of polycyclic aromatic hydrocarbons (PAH) from sediment layers of Bodensee areas differently exposed to environmental burden were determined. 32 PAH and 10 nitrogen containing PAH were identified by comparison with authentic samples. A method of quantitativ enrichment and gasdiromatographic determination of PAH containing 4-7 rings is described. In a comparative profile analysis only 20 most abundant PAH have been regarded. Low burdened areas (entre of the lake, 250m deep; Güttingen) show only 10 - 20% of the PAH content of high-burdened areas (mouth of Argen and Schüssen). The qualitative and quantitative composition of the PAH fraction (PAH-profile) from different layers of a sediment drilling core are very similar whereas profiles from different regions can be distinguished. The concentration of PAH increases from the surface to a layer with maximum burden (1965 - 1970) and then decreases to a remaining concentration (1900). From the typical PAH profile and some characteristic compounds as e.g. benzo (b) -naphtho (2,1-d) thiophan, benz (a/c) acridines, benzo (a/b/c)-carbazoles, dibenzacridines, and dibenzcarbazoles some potential sources as motor- car traffic, petroleum, fuel oil, and used lubricating oil can be excluded. Coal combustion smoke gas is supposed to be the main source of emission.

In several series of 262 samples, Higher Fungi, especially from the Tremellales and Gastero-mycetes, were analyzed by atomic absorption spectroscopy on their content of the trace metals manganese and iron. Both elements were found to be present in higher concentrations in some species of the Tremellales and Phallales. In the case of wood-destroying fungi, the Fe-and Mn-contents of the substrates were compared to those of the corresponding fungi. Only the species with the highest level of these metals reached the same contents as their substrates or a poor enrichment. Among the remaining species of the Higher Fungi, only in the case of the epigean Phallales, a possible biochemical role of manganese has been discussed.

Tectona, Verbenaceae, Diterpene, Tectograndinol Tectograndinol (1), a new diterpene has been isolated from leaves of Tectona grandis. Its structure and configuration is elucidated by spectroscopic methods and some chemical reactions.

Several biologically active substances, such as aloenin (1), magnesium lactate, aloe-emodin (4), barbaloin (5), and succinic acid, were found to be contained in the leaf juice of Aloe arborescens Mill. var. natalensis Berger, which has widely been used in domestic medicines. Aloenin (1) and magnesium lactate were elucidated to exhibit an inhibitory action on the gastric juice secretion of rats. Various constituents other than the above bioactive substances were found in the leaves and the roots of the plant.

The chemical composition of the gland-pad sebum of gerbils of both sexes is analysed using gas-liquid chromatographical and mass spectroscopical techniques and compared with the lipids from distal skin areas. Cholesterol esters, with (ω-1)-methyl-substituted fatty acids as acidic constituents, were shown to occur in the gland-pad sebum of both sexes in high concentrations, whereas cholesta-3,5-diene could be detected in the males only.

Electrophoretic Pattern, Crop Contents, Identification of Prey Species First, experiments were tested for a new method concerning analyses of crop contents in liquo-somatophagous animals. Disc-electrophoretic separations of the crop contents of Helobdella stagnalis yielded protein patterns typical for the number of bands and for the relative mobilities in these Chironomid larvae, on which H. stagnalis were fed. Additionally, slowly migrating bands occurred in the separations of the crop contents, varying in their number; likewise, an esterase showed a high activity at a crop contents of pH 6.2.

Dermatosparactic calf-tail-tendon-collagen was investigated by mechanical measurements, electron microscopy and x-ray diffraction. We suppose, that the tensile strength decrease of the fibres is due to the irregular aggregation of subfibrils to fibrils. The x-ray diagram of the fibre is not influenced by state of disorder. Cyclic extension of dermatosparactic collagen leads to a higher increase in tensile strength than in the case of normal calf tendon. The effect might be due to the increase of fibril-and area-density resulting in an augmentation of crosslinks.

The structure and size of lecithin/sodium glycocholate mixed micelles was investigated by quasi­ elastic laser light scattering and spin label techniques. The investigations are in accordance with a bilayer model for these micelles. The order parameter and the phase transition enthalpy of the micellar bilayer were determined. The lateral and rotational diffusion constants of label molecules are compared with the cor­ responding diffusion constants in liposomes.

Cibacronblue The inhibition of the activity of various kinases and dehydrogenases by Cibacronblue 3 G-A and its structural analogues relies on the interaction of the anthrachinone moiety as well as of the neighbouring phenyl group of the dye with the proteins. Binding is intensified by hydrophobic substituents at the latter ring system.

Thirty derivates from substituted-phenyl-ethyl methylphosphonates have been synthesized and their inhibiting power of acetyl-cholinesterase have been examined in vitro and in vivo. The correlation between inhibition of the enzyme and electrophylic power of the substituent of the phenyl group was excellent, but when this group contains two substituents, steric factors appear to operate. The activity of these compounds has been demonstrated to be higher than their phosphate analogs.

The major flavonoids of Pisum are derivatives of kaempferol and quercetin, including both tri-glucosides and acylated triglucosides in which the acyl group is p-coumaric acid. Although hydroxy-cinnamic acid esters of flavonoids are common pigments in many plants, neither the enzymes nor the precursors involved in their biosynthesis have been demonstrated. We report here that crude enzyme preparations extracted from peas catalyze the transfer of the p-coumaroyl moiety of p-coumaroyl: Coenzyme A to kaempferol-3-triglucoside forming kaempferol-3-(p-coumaroyl triglucoside) as the acylated product. The reaction product has been vigorously shown to be identical to the naturally occurring kaempferol-3-(p-coumaroyl triglucoside) in both chromatographic and chemical properties. The enzymatic formation of the acylated derivative occurred only minimally when incubated with the cofactors required for carboxyl group activation (ligase) and maximally when incubated with p-coumaroyl : Coenzyme A as the acyl donor.

1. Aminoacylase is irreversibly inactivated by the chloromethylketone analogs of benzyloxy-carbonyl-L-alanine, L-alanine, L-leucine, L-aspartic acid (β), tosyl-L-phenylalanine and L-leucyl-L-alanine. The kinetics of the inactivation of the enzyme by the halo-methylketones were investigated. 2. Leucyl-and alanyl chloromethylketone inactivate the enzyme by blocking of 4 SH groups. Experiments with [U- 14 C] leucyl chloromethylketone confirm that maximal 4 residues are covalently bound to the protein. 3. Inactivation of the enzyme by benzyloxycarbonylalanyl and tosylphenylalanyl chloromethyl­ ketone is the result of the substitution of the £-amino group of one lysine residue per active site and not of SH groups. However, in the presence of competitive inhibitors these halomethylketones react only with the SH groups of the enzyme, too.

The mechanism of in vitro inactivation and ATP-dependent rapid reactivation of rat liver tyrosine aminotransferase by a membrane-bound system from rat liver and kidney cortex and the nucleotide specificity of this process was investigated using partially purified tyrosine amino­ transferase as a substrate. Adenosine 5′-triphosphate (ATP) could be replaced by guanosine 5′-tri-phosphate (GTP), whereas inosine 5′-triphosphate (ITP) was less effective. During reactivation [γ- 32 P]A T P was incorporated into the enzyme and not excorporated by incubation of the labeled enzyme with excess non-radioative ATP. Inactivation of labeled tyrosine aminotransferase by a particulate fraction led to a decrease protein-bound radioactivity concomitant with an increase of [32P] orthophosphate. This points to a phosphorylation and dephosphorylation mechanism in the regulation of tyrosine aminotransferase activity.

Photorespiration, Ribulose 1,5-diphosphate-Carboxylase/Oxygenase, Gene Composition The activity of ribulose 1,5-diphosphate (RuDP)-carboxylase and RuDP-oxygenase was measured in crude leaf extracts of the tobacco (N . tabacu m) phenotypes which differed with respect to their gene constitution and with respect to their photosynthetic and photorespiratory activity. The green wild type (JWB) which carried the discussed two nuclear factors su and aur in the condition su/su Aur/Aur and su/su Aur/aur exhibits normal photosynthetic activity and low photorespiratory activity. A yellow-green chlorophyll-deficient phenotype (Su/su) carrying Su/su Aur/Aur has high photosynthetic activity on a chlorophyll basis but also high photorespiratory activity. A new yellow phenotype (Su/su var. Aurea) carrying both nuclear factors in a heterozygous condition Su/su Aur/aur has high photosynthetic activity on the basis of chlorophyll and low photorespiratory activity. The comparison of the RuDP-carboxylase/oxygenase activity in these three phenotypes shows that in the yellow-green phenotype Su/su the affinity of the RuDP-oxygenase towards oxygen is higher than in the green phenotype JWB and in the yellow phenotype Su/su var. Aurea. The K m ((O 2 ) values for the RuDP-oxygenase activity are 890 /um for JWB, 630 μм for Su/su and 940 μм for Su/su var. Aurea and the corresponding K i (CO 2 ) values are 7.4 μм for JWB, 14.9 μм for Su/su and 5.8 μм for Su/su var. Aurea at pH 8.34. On the other hand, the affinity of the carboxylating activity of the enzyme towards CO 2 shows no difference between JWB and Su/su var. Aurea, but a lower affinity in Su/su. This is expressed by the K m (C 02) values which are 107 μм for JWB, 143 μм for Su/su and 96 μм for Su/su var. Aurea at pH 7.8. However, the affinity of the oxygenase function of the enzyme towards RuDP seems to be unchanged in all three tobaccos and is found to be around K m (RuDP) 27 μм. From this result it appears that the nuclear factor su decreases in the condition Su/su Aur/Aur the affinity of the RuDP-carboxylase towards CO 2 and increases the affinity of the RuDP-oxygenase towards oxygen. On the other hand, the factor aur seems to suppress this gene expression in the condition Su/su Aur/aur whereas both factors do not affect the binding of RuDP onto the enzyme.

1. P 1 , P 5 -Bis-(5′-adenosyl)pentaphosphate (Ap 5 A) inhibits “soluble” adenylate kinase even when this enzyme is an integral part of the complete mitochondrion. The K i is 10 -5 м , i. e. about two orders of magnitude higher than the inhibitor constants determined for the purified adenylate kinase of rabbit muscle and an enzyme preparation separated from the mitochondrial intermembrane space. The weaker inhibitory effect is due to a lower accessibility of the enzyme. 2. As to be expected Ap 5 A which is of the “multisubstrate analogue”-type does not affect mito­ chondrial nucleoside diphosphate kinase. 3. Though Ap 5 A owns the structural elements of both ATP and ADP it is not a substrate of the adenine nucleotide carrier, i.e. neither it is exchanged across the inner mitochondrial membrane nor specifically bound. 4. Ap 5 A is not metabolized by rat liver mitochondria.

The first three enzymatic steps of assimilatory sulfate reduction in chloroplasts of higher plants have been investigated with emphasis on the influence of adenosine-mono-and -diphosphate upon the formation of APS, PAPS and bound sulfite. The data show that the activation process is governed by the energy charge of the chloroplast. The regulatory step is localized at the ATP-sulfurylase reaction. It was found that this enzyme is inhibited by low concentrations of AMP and ADP, with apparent K iAMP = L8mм and K iADP =0.5 mм for the chloroplast preparations. The isolated purified ATP-sulfurylase is inhibited by the nucleotides accordingly, with K iAMP =0.2mм and K iADP =0.4mм. The results are interpreted as a regulatory mechanism for the complete process of assimilatory sulfate reduction in the chloro­ plast.

The Hill-activity (reduction of DCPIP or methylviologen) and the concentration of P700 were studied in chloroplasts isolated from cotyledons of radish seedlings (R aphanus sativu s L. Saxa Treib), which had been grown with the addition of β-indoleacetic acid (IAA), kinetin, or gibberellic acid. 1) The photosynthetic activity of young chloroplasts from 3 day old Raphanus seedlings is very high (c. 180 μmol O 2 /mol chlorophyll × h) and decreases continuously thereafter with increasing age. The steady state Hill-activity is readied after 8 to 10 days (values of 55 to 50 μmol 02/mg chlorophyll × h). 2) Chloroplasts from plants treated with IAA or kinetin not only exhibit higher plastoquinone levels 1,2 , but also a higher P700-content and a higher Hill-activity. The promotion effect is more pronounced with kinetin (+ 36 to 40%) than with IAA (+ 12 to 17%). 3) Gibberellic acid has a different effect on composition and activity of chloroplasts. In younger seedlings the Hill-activity appears to be somewhat stimulated, without promotion effect on plasto­ quinone 2 or P700 concentration. After 10 days GA 3 -treated plants show signs of chlorosis combined with a strong decrease in photosynthetic activity. 4) The data clearly demonstrate that the composition and activity of the photosynthetic ap­ paratus are under phytohormone control. IAA and even better kinetin promote the light induced formation of pigment systems and electrontransport chains. GA 3 seems to block the rebuilding of the photosynthetic apparatus under steady state conditions.

Exchange of CF 1 -bound adenine nucleotides was shown to take place when isolated broken chloroplasts were subjected to an acid/base treatment. This process was measured in forward (in­ corporation of 14 C-labeled nucleotides) as well as back exchange reactions (release of bound labeled nucleotides). In the presence of unlabeled ADP and P i a high precentage of labeled ATP was found to be released into the medium. Exchange is highly specific for exogenous ADP and ATP. Acid/base-induced adenylate exchange and acid/base-induced phosphorylation were measured in dependence of several external factors. The substrate constant for ADP in exchange was 1.6 μм, whereas an apparent K m of 5 μм was determined for ADP in the phosphorylation process. Acid/base-induced exchange of adenine nucleotides and acid/base-induced phosphorylation depend in a similar way on the pH values of the acid and base stages. Acid/base-induced ATP formation was sensitive to prolonged treatment in the acid stage whereas exchange was not. Mg 2+ was strictly required in phosphorylation but less important in exchange. The phosphorylation ability decreased within seconds after acid/base transition; however, the ability of [ 14 C]ADP incorporation persisted for minutes. The formation of ATP depended on an acid/base transition, whereas some adenylate exchange was also induced by an acid treatment alone. The results suggest that appropriate pH values at the inner and outer side of the thylakoid membrane rather than energy from a pH gradient is sufficient for adenylate exchange to take place on membrane-bound CF 1 .

Chloroplasts H+/e Ratio, Buffering Capacities The number of H + released inside the chloroplast thylakoids per electron flowing to the terminal electron acceptor (the H + /e ratio) has been investigated using a pH indicator dye technique. The apparent H + /e ratio was measured by comparing the absorbance change due to H + -uptake outside the thylakoids in the absence of uncoupling agent, and the absorbance change due to the net H + -production associated with water-splitting after addition of uncoupling agent in the presence of ferricyanide. (1) The apparent H + /e ratio was found to be higher than 2, using methylamine as uncoupling agent (> 1 mм). It varied with the concentrations of added buffer. (2) The apparent H + /e ratio obtained with methylamine as uncoupling agent (with or without additional buffer) approached the value of 2 with decreasing concentrations of methylamine. (3) A consistent H + /e ratio of 2 was also obtained with gramicidin or the nigericin-type ionophore dianemycin over a relatively large concentration range, and did not vary with addition of extra buffer. (4) The buffering capacity of the chloroplast suspension was estimated and was found to be the same order of magnitude as that of methylamine at the concentrations used. We suggest that the high H + /e ratios reported 423, 510-523 [1976]) reflect a failure to take account of the change in buffering capacity of the chloroplast suspension on adding uncoupling concentrations of methyl­ amine. Other possible sources of error in the estimation of H+/e ratio by different techniques are also discussed.

Three polypeptide fractions with the apparent molecular weight 66 000 were isolated from stroma-freed Antirrhinum chloroplasts which were solubilized with dodecyl sulfate. Antisera to these fractions affect electron transport in distinctly different ways. For the characterization of the three antisera photochemical reactions of chloroplast preparations with artificial electron donors and acceptors as well the analysis of fluorescence rise curves were used. Antiserum 66 000 PSI-96 inhibits electron transport apparently on the acceptor side of photosystem I, provided the antibodies are adsorbed onto the outer surface of the thylakoid membrane. Antiserum 66 000 PSI-88 probably acts directly on the reaction centre I or on its immediate vicinity, if the antibodies are adsorbed at the inner surface of the thylakoid membrane. Antiserum 66 000 PSII-42 inhibits electron trans­ port in the region of photosystem II. The antigen towards which the antiserum is directed appears to belong to the reaction centre II, as also in the condition of high inhibition degrees, the fluorescence intensity remains unchanged. The antigenic determinants are located at the outer surface of the thylakoid membrane.

Phosphorylation, Dephosphorylation, Inorganic Phosphate, Sarcoplasmic Membranes The calcium transport protein of the sarcoplasmic reticulum accepts inorganic phosphate rapidly when phosphorylation is initiated either by the addition of phosphate or m agnesium ions to the calcium free protein. Phosphorylation proceeds much more slowly when it is initiated by the addition of the calcium chelator ethyleneglycol-bis (β-aminoethyl ether) -N ,N′-tetraacetic acid (EGTA) to the phosphate and magnesium containing assay. The time course of phosphorylation following immediately calcium removal is monophasic at all temperatures between 20° and 37 0|C. In contrast, phosphorylation of the calcium free enzyme becomes biphasic at temperatures above 25 °C. The biphasic time course does not only apply to net formation of phosphoprotein but also to its exchange with medium phosphate. On addition of calcium, the phosphoprotein decays in a biphasic process the time constants of which are much longer than those observed for phosphoprotein formation. The temperature dependence of the rate as well as of the extent of phosphoprotein formation indicate a discontinuity in the reactivity of the protein.

Bacteria, Thymine Starvation, Recovery, Filamentformers For filament forming strains of Escherichia coli, it is shown that susceptibility to thymine starvation was dependent upon the nature of the plating media. In such bacteria, p art of the induced damages was found to be repairable if the cells after starvation were held in a non-nutrient medium. For non-filament forming bacteria, no such phenomena were observed.

Sodium saccharin in concentrations from 0.02 to 20.00 mg/ml inhibits the in vitro growth of glucose-grown cariogenic and other streptococci, and suppresses, esp. at the higher concentration range, the fermentative acid production of these microorganism s to acid levels much lower than the critical pH of 5.5. These observations indicate a possible caries antagonism by saccharin.

A mathematical model for the interaction kinetic in phage-bacterium culture is proposed. An appropriate analytical relationship between phage and bacterial concentrations has been derived. Characteristic kinetic constants have been obtained by com paring the experimental growth curves with computer-simulation analysis. The model allows also to evaluate the phage-yield as a function of the initial concentrations.

The genetic information of Φx 174 genome (genes and intermediate segments) is analyzed in terms of its independent (D 1 index) and dependent information (D 2 and D 3 Markovian indexes), as well as of its ability to generate secondary structure. Genes B and E, enclosed in A and D respectively, have: 1) values of D 1 and D 3 indexes closer to the theoretical random distribution curves than those of (A -B) and (D -E) gene fractions, and 2) in the ability for secondary structure generation minor differences with genes A and D. F → G and mRNA start → A intermediate segments differ from randomness in their D 1 and D 2 indexes, but not so much in the D 3 values. All these data point out the use of code degeneracy for increasing the genetic information density of the virus.

Light responses (ReP) and pre-stimulus membrane potential (PM P) and conductance of photoreceptors of Astacus leptodactylus and Limulus polyphemus (lateral eye) were recorded and changes were observed when the photoreceptor was depolarized by the action of external ouabain or high potassium concentration application. 1 mм/1 ouabain application causes a transient increase of PMP and ReP in Limulus, followed by a decrease which is faster for the ReP (half time 34 min) than for the PMP (half time 80 min). Irreversible loss of excitability occurs when the PM P is still ca. 40% of the reference value. In both preparations high external potassium concentration leads to total depolarization (beyond zero line to +10 - +20mV) of the PMP and after a time lag of 10 min also to a loss of excitability (intracellular recording). In extracellular recordings (Astacus) the excitability remains at a low level of 15%. The effects are reversible and are similar whether no or 10% external sodium is present. In all experiments the light-induced changes of membrane conductance are about parallel to those of the light response. The fact that the ability of the photosensoric membrane to undergo light-induced conductance changes is membrane potential-dependent is discussed, leading to the explanation that dipolar membrane constituents such as channel forming molecules (probably not rhodopsin) have to be ordered by the m embrane potential to keep the membrane functional for the photosensoric action.

In this paper we seek to determine the shape of the barrier between the normal and tautomeric conformers for some excited singlet and triplet states in the molecules of guanine and cytosine. The molecules are considered isolated and a particular movement of the H atom is analysed. The semi-empirical CNDO/2-CI has been used. The calculated results are compared with the available experimental data.

The chirality of the hydrogen transfer from (3R) hy­ droxybutyrate to NAD catalyzed by (3R) hydroxybutyrate dehydrogenase (E.C. 1.1.1.30, ᴅ-3-hydroxybutyrate : NAD oxidoreductase) from Pseudomonas lemoignei was investi­ gated. [4- 3 H ]NAD was enzymatically reduced to (4R) [4- 3 H ]NADH with (3RS) hydroxybutyrate. This observation was confirmed since NAD could be reduced to (4S) [4- 3 H] NADH with (3RS) [3- 3 H] hydroxybutyrate and (3R) hy­ droxybutyrate dehydrogenase. From these experim ents it can be concluded that (3R) hydroxybutyrate dehydrogenase from P. lem oignei should be classified as an B or (S) type dehydrogenase.

Plastidic Cytochrome b-563 Cytochrome b-563 from spinach chloroplasts was isolated in a homogeneous and enzymatically active form. It has a low, but variable lipid content and a molecular weight of about 18,000 daltons.

Thioacylureas and thioacylam ides were found to inhibit photosynthetic O 2 -evolution (Hill-reactions) of “broken chloroplasts”, some derivatives approaching an I 50 of 10 -5 м. The inhibition site is near photosystem II. The inhibitory effects of the tested derivatives vary in their pH-dependency between pH 5 and 8.

The major glycoprotein (gp70) of simian sarcoma virus is present in “soluble” form in the medium of virus-producing suspension cultures. It could be isolated from the supernatant of such cultures in substantial amounts by an immuno-adsorbent technique. Some of its gel-electrophoretic and serological properties are described.

Intracellular recording and dye injection have directly demonstrated the absolute and spectral sensitivities of R7 and R8 in the eye of Calliphora. R8 has major peak of sensitivity at 547 nm with less than half the bandwidth of a theoretical rhodopsin, and a subsidiary peak at 358 nm. R7 is confirmed as being an ultraviolet receptor. Both have absolute sensitivities similar to those of R 1 -6. These results are inconsistent with the scotopic (R1-6), photopic (R7 and R8) theory of fly vision.