Nitrate‐N concentration in tile water, loss from tile lines, and accumulation in soil profiles were determined following each of three annual applications of 20, 112, 224, and 448 kg N/ha to continuous corn (Zea mays L.) grown on a Webster clay loam (Typic Haplaquoll) in southern Minnesota. Plots were isolated to a depth of 1.8 m with plastic to allow an accurate assessment of the area drained. Water flow through the tile lines occurred annually for approximately 6 weeks in the period from mid‐April through early July and constituted an equivalent from 20 to 46% of the precipitation during the flow periods and from 7 to 22% of the annual precipitation during the 3 years studied.There was relatively little increased NO3‐N accumulation in the soil profile or loss from tile lines at the recommended application rate of 112 kg N/ha compared to that for the check treatment. Nitrate‐N losses through tile lines in 1975 (after 3 years treatment) were 19, 25, 59, and 120 kg/ha for the 20, 112, 224, and 448 kg N/ha applications, respectively, which had NO3‐N accumulations in the 0–3 m soil profiles of 54, 100, 426, and 770 kg NO3‐N/ha. Maximum NO3‐N accumulation in the soil profiles occurred at a depth of about 1 m with little evidence of movement below about 2.2 m.

In the Rhine-delta, accumulation of microcontaminants in floodplain foodwebs has received little attention in comparison with aquatic communities. To investigate organochlorine and metal concentrations in a terrestrial foodchain, samples of soil, earthworms (Lumbricus rubellus), and shrew (Crocidura russula, Sorex araneus) livers and kidneys were taken from two moderately to heavily polluted floodplains. Chlorobiphenyl residues in earthworm fat were 0.10 to 3.5 times the concentrations in soil organic matter, whereas ratios for other organochlorines varied between 0.87 and 8.8. These ratios are one order of magnitude lower than expected from laboratory experiments with earthworms, and laboratory and field studies on aquatic invertebrates. Bioconcentration ratios for heavy metals are in accordance with literature values for other locations, confirming the high potential for cadmium accumulation in Lumbricidae. Concentrations of organochlorines in shrew liver lipids were 1.0 to 13 times the residues in earthworm fat. These values are higher than lipid-corrected biomagnification ratios for laboratory rodents, but equal to those measured for benthivorous birds in the Rhine-delta. On a dry weight basis, kidney-earthworm ratios for cadmium were about one order of magnitude lower than previously reported values for insectivores. Soil concentrations of many compounds in both floodplains did not meet Dutch quality standards. Yet, hexachlorobenzene, chlorobiphenyl 153 (PCB153), gamma-hexachlorocyclohexane, sigma DDT, and dieldrin residues in earthworms and shrews did not exceed diet levels expected to be safe for endothermic species. An exception was noted for cadmium in worms and shrew kidneys. Heavy metal pollution in soil was close to levels that are critical to earthworms in laboratory studies. Cadmium concentrations in shrew kidneys were below levels suggested to be safe for Sorex araneus, but above those that were critical to the rat.

A blue fluorescence protein has been isolated and purified from extracts of the luminous bacterium Photobacterium phosphoreum. It is a single polypeptide of molecular weight 22,000 with absorption maxima at 274 and 418 nm. It is efficiently fluorescent (OF 0.45), with a fully corrected spectral maximum (476 nm) and distribution identical to the in vivo bioluminescence from this same type of bacterium. At low concentration this fluorescence shifts towards the red and becomes identical to the in vitro bioluminescence emission. This spectral shift apparently results from a change in the protein pulled by dissociation of the chromophore . If the blue fluorescence protein is included in the in vitro bioluminescence reaction with reduced FMN, oxygen, aldehyde, and luciferase (P. phosphoreum), the bioluminescence spectrum is shifted towards the blue from its maximum at 490 nm to one at 476 nm, where it is again identical in all respects to the in vivo bioluminescence spectrum. This is accompanied by an increase in the initial light intensity by an order of magitude at saturating levels of blue fluorescence protein, and the specific light yield of the luciferase is increased 4-fold. It is suggested that the blue fluorescence protein acts as a sensitizer of the bacterial bioluminescence reaction. (14) claimed that the emitter must be some sort of flavin-derived species (2), three proposals for its structure were put forward, supported almost solely by the similarity of the fluorescence of model compounds to the bioluminescence spectra. Eley et al. (12) (17) proposed an FMNH2 molecule substituted in the 4a-position.It had been tacitly assumed that the mechanism of reaction and identity of the emitter are the same in vivo as in vitro. The possibility of a difference has been raised by the recent discovery of a bacterial type emitting at 545 nm (18). In this paper we show that a protein-bound chromophore can be isolated from extracts of the bioluminescent bacteria P. phosphoreum that is closely associated with luciferase and that fulfills all the conditions to qualify it as the in vivo emitter. MATERIALS AND METHODSThe bacterium Beneckea harveyi, strain 392 in the classification scheme of Reichelt and Baumann (19), previously designated "MAV,"' was obtained from J. W. Hastings (Harvard University). The type "A-13" was isolated from the light organ of the "silver macrourid" fish by J. Paxton (Australian Museum) and has been identified as Photobacterium phosphoreum (J. Fitzgerald, private communication). The type Photobacterium fischeri, strain 399, was obtained from F. H. Johnson (Princeton University). The bacteria were grown and the luciferase and FMN were purified as described (20,21). The blue fluorescence protein was routinely assayed by its fluorescence intensity at 470 nm when excited at 420 nm, with an Aminco-Bowman Spectrofluorimeter. Luciferase activity was determined with a digital photometer, designed and constructed by G. J. Faini, which was calibrated for absolute photon sensitivity with the luminol ch...

Standard free energies of exchange, ΔG°, were determined for the exchange of Na with Li, K, Rb, and Cs on a 0.1–0.5 micron fraction of Chambers montmorillonite having an exchange capacity of 123 ± 2 meq/100 g. The ΔG° values ranged from +80 cal mole‐1 for Na→Li exchange to ‐1886 cal mole‐1 for Na→Cs exchange and were approximately twice as large as those found previously for similar exchange reactions on Wyoming bentonite having an exchange capacity of 92 ± 2 meq/100 g. The ΔG° values reflect cation selectivity differences of a factor of two to three between the two clays. In contrast, the standard heats of exchange, determined calorimetrically, were approximately the same for both clays and ranged from + 125 cal mole‐1 for Na→Li exchange to ‐2575 cal mole‐1 for Na→Cs exchange. These results indicate that the differences in free energies of exchange between the two clays are due to entropy effects.

SummaryA series of isoalloxazine and alloxazine derivatives have been investigated by 13C-NMR. The synthesis of selectively 13C-enriched derivatives made it possible to assign unambiguously the signals due to the quaternary carbon atoms at position 4, 4a and 10a of the isoalloxazine ring system. The assignment of the other resonances was ensured by the use of selectively deuteriated and chemically modified compounds as well as by decoupling techniques. The assignments differ in part from those published by Breitmaier & Voelter [2] on FMN and FAD. The solvent dependence of the resonances has been studied in dioxan/water mixtures. The experimental data are compared with published MO calculations and discussed.