Mixed anion lanthanide(III) crown ether complexes: crystal structures of [LaCl2(NO3)(12-crown-4)]2, [La(NO3)(OH2)4-(12-crown-4)]Cl2·CH3CN and [LaCl2(NO3)(18-crown-6)]

Reaction of LaCl₃·7H₂O containing small amounts of La(NO₃)₃·7H₂O as an impurity with 12-crown-4 or 18-crown-6 in 3:1 CH₃CN:CH₃OH resulted in the isolation of the mixed anion complexes [LaCl₂(NO₃)(12-crown-4)]₂, [La(NO₃)(OH₂)₄(12-crown-4)]Cl₂·CH₃CN and [LaCl₂(NO₃)(18-crown-6)]. The nine-coordinate dimer, [LaCl₂(NO₃)(12-crown-4)]₂, has all of the anions in the inner coordination sphere and La³⁺ has a capped square antiprismatic geometry. It crystallizes in the orthorhombic space group Pbca with (at −150 °C) a = 12.938(6), B = 15.704(3), C = 13.962(2) Å, and D_calc = 2.08 g cm⁻³ for Z = 4. The second complex isolated from the same reaction, [La(NO₃)(OH₂)₄(12-crown-4)]Cl₂·CH₃CN, has the bidentate nitrate anion in the inner coordination sphere but the two chloride anions are in a hydrogen bonded outer sphere. This complex is ten-coordinate 4A,6B-expanded dodecahedral and crystallizes in the monoclinic space group P2₁ with (at 20 °C) A = 7.651(2), B = 11.704(7), C = 11.608(4) Å, β = 95.11(2)°, and D_calc = 1.80 g cm⁻³ for Z = 2. The 18-crown-6 complex, [LaCl₂(NO₃)(18-crown-6)], has all inner sphere anions and has ten-coordinate 4A,6B-expanded dodecahedral La³⁺ centers. It crystallizes in the orthorhombic space group Pbca with (at 20 °C) a = 14.122(7), B = 13.563(5), C = 19.311(9) Å, and D_calc = 1.89 g cm⁻³ for Z = 8.     

Biotransformation of diphenyl ether by the yeastTrichosporon beigelii SBUG 752

Trichosporon beigelii SBUG 752 was able to transform diphenyl ether. By TLC, HPLC, GC, GC-MS, NMR- and UV-spectroscopy, several oxidation products were identified. The primary attack was initiated by a monooxygenation step, resulting in the formation of 4-hydroxydiphenyl ether, 2-hydroxydiphenyl ether and 3-hydroxydiphenyl ether (48:47:5). Further oxidation led to 3,4-dihydroxydiphenyl ether. As a characteristic product resulting from the cleavage of an aromatic ring, the lactone of 2-hydroxy-4-phenoxymuconic acid was identified. The possible mechanism of ring cleavage to yield this metabolite is discussed.     

Studies on well-coupled Photosystem-I-enriched subchloroplast vesicles. Electron transfer by b- and c-type cytochromes in relation to the origin of the ‘slow’ electric potential component

Cytochrome redox changes and electric potential generation are kinetically compared during cyclic electron transfer in Photosystem-I-enriched and Photosystem-II-depleted subchloroplast vesicles (i.e., stroma lamellae membrane vesicles) supplemented with ferredoxin using a suitable electron donating system. In response to a single-turnover flash, the sequence of events is: (1) fast reduction of cytochrome b-563 (t_0.5 ≈ 0.5 ms) (2) oxidation of cytochrome c-554 (t_0.5 ≈ 2 ms), (3) slower reduction of cytochrome b-563 (t_0.5 ≈ 4 ms), (4) generation of the ‘slow’ electric potential component (t_0.5 ≈ 15–20 ms), (5) re-reduction of cytochrome c-554 (t_0.5 ≈ 30 ms) and (6) reoxidation of cytochrome b-563t_0.5 ≈ 90 ms). Per flash two cytochrome b-563 species turn over for one cytochrome c-554. These b-563 cytochromes are reduced with different kinetics via different pathways. The fast reductive pathway proceeds probably via ferredoxin, is insensitive to DNP-INT, DBMIB and HQNO and is independent on the dark redox state of the electron transfer chain. In contrast, the slow reductive pathway is sensitive to DNP-INT and DBMIB, is strongly delayed at suboptimal redox poising (i.e., low $\text{NADPH}\text{NADP}{}^{\mathrm{+}}$ ratio) and is possibly coupled to the reduction of cytochrome c-554. Each reductive pathway seems obligatory for the generation of about 50% of the slow electric potential component. Also cytochrome c-559_LP (LP, low potential) is involved in Photosystem-I-associated cyclic electron flow, but its flash-induced turnover is only observed at low preestablished electron pressure on the electron-transfer chain. Data suggest that cyclic electron flow around Photosystem I only proceeds if cytochrome b-559_LP is in the reduced state before the flash, and a tentative model is presented for electron transfer through the cyclic system.     

Brain CCK receptors are structurally distinct from pancreas CCK receptors

Brain and pancreas cholecystokinin (CCK) receptors differ markedly in their selectivity for CCK analogs. To determine the size and subunit structure of the brain CCK receptor and compare it to that of the pancreas, 125I-CCK33 was covalently cross-linked with ultraviolet light to its receptor on mouse brain particles and purified pancreatic plasma membranes. When CCK was crosslinked to brain membranes, a single consistent major labeled protein band of Mr = 55,000 was observed in both the presence and the absence of DTT. These data with brain receptors contrast to results with pancreatic receptors where two bands of Mr = 120,000 and 80,000 are labeled in the absence and presence of DTT, respectively. These studies indicate, therefore, that the brain and pancreas CCK receptors are structurally and functionally distinct.     

Requirement of trypsin inhibitor for measurement of 3-hydroxy-3-methylglutaryl coenzyme A reductase in intestinal mucosa of rat

A method was developed for the determination of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in the microsomal fraction of crypt cells and villi of rat intestinal mucosa. Addition of trypsin inhibitor to homogenizing and incubation media at a proper concentration appeared inevitable for measurement of the activity of the villi fraction. The reductase in crypt cells was also slightly enhanced by the addition of the inhibitor. Using this technique, the enzyme activity in villi was found to be as active as the crypt cell fraction. Since other types of protease inhibitors were not necessarily effective, it was suggested that specific enzyme(s) inactivates the mucosal reductase in the course of measurement.     

Isopongaglabol and 6-methoxyisopongaglabol,two new hydroxyfuranoflavones from Pongamia glabra

Isopongaglabol and 6-methoxyisopongaglabol, two new hydroxyfuranoflavones, together with two furanoflavones 5-methoxyfurano(8,7-4″,5″)flavone and 5-methoxy-3′,4′-methylenedioxyfurano(8,7-4″,5″)flavone, two simple flavones, desmethoxykanugin and fisetin tetramethyl ether, a chromenoflavanone, ovalichromene B, two triterpenes, cycloart-23-ene-3β,25-diol and friedelin, and β-sitosterol-β-d-glucoside were isolated from the petrol and CHCl₃ extracts of the flowers of Pongamia glabra. The structures of isopongaglabol and 6-methoxyisopongaglabol have been established as 4′-hydroxyfurano(8,7-4″,5″)flavone and 4′-hydroxy-6-methoxyfurano(8,7-4″,5″)flavone, respectively, on the basis of the spectral evidence and they have been confirmed by synthesis.     

Diastereoisomers of cyclocymopol and cyclocymopol monomethyl ether from Cymopolia barbata

Optically active diastercoisomers of the brominated monoterpene quinols, cyclocymopol and cyclocymopol monomethyl ether, were isolated from the green marine alga Cymopolia barbata and charac- terized.     

Progestin metabolism in the rhesus monkey corpus luteum

For the purpose of describing the pathway by which estrogens are synthesized in the rhesus monkey ($\text{Macaca}$$\text{mulatta}$) corpus luteum (CL), CL were obtained during the midluteal phase of the menstrual cycle and fragments incubated with equimolar amounts of [7-³H]pregnenolone plus [4-¹⁴C]progesterone. Metabolites including ³H-progesterone, ³H, ¹⁴C-20α-dihydroprogesterone, ³H, ¹⁴C-17-hydroxyprogesterone, ³H-estrone and ³H-estradiol-17β appeared in the medium during the first 20 minutes of incubation, ³H, ¹⁴C-Androstenedione was not consistently noted until after 60 minutes. Despite the fact that the ¹⁴C/³H-17-hydroxyprogesterone ratio quickly approached a constant value in the medium, ¹⁴C-estrogens were not detected in the medium or tissue fragments suggesting that progesterone was not a principal precursor for estrogen synthesis. As evidenced by the observation that the ¹⁴C/³H-progesterone ratio was significantly higher in luteal fragments than the 17-hydroxyprogesterone ratio, 17-hydroxyprogesterone appeared to be synthesized from pregnenolone both by way of progesterone and by another route which did not include progesterone. C₂₁- and C₁₈-Steroids were more concentrated in tissue fragments after 120 minutes of incubation than in the medium indicating that these steroids were sequestered by luteal tissue.     

Radioimmunoassay of 2-hydroxyestrone

Under the protection of ascorbic acid a 2-hydroxyestrone bovine serum albumin conjugate was prepared containing intact 2-hydroxyestrone as determined by gas chromatographymass spectrometry. Using this antigen highly specific antibodies were raised in rabbits. Cross-reactivity for 2-hydroxyestradiol and 2-hydroxyestriol was 26 and 4.5%, respectively. An assay procedure of 2-hydroxyestrone in human plasma is described. Using special precautions the assay allows the determination of 2-hydroxyestrone in plasma samples of women (50–95 pg/ml), pregnant women (105–220 pg/ml), men (45–65 pg/ml) and children (20–40 pg/ml).