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We have previously reported on an unusual stereospecificity of firefly luciferase for a D(-) isomer of firefly luciferin.' While both the D(-) and the L(+) form will react with ATP to liberate pyrophosphate in the reaction E + LH2 + ATP =-E. LH2AMP + PP,only D(-) LH2AMP will react further, in the presence of oxygen, to produce bioluminescence and an oxidized product. There is also a strong pH dependence of the color of the emitted light;2 in acidic buffer solutions, pH < 6.5, the intensity of the normal yellow-green emission, peaking at 562 ml,, decreases markedly and a low intensity red emission is observed, peaking at 616 miu. This is evidence that enzyme configuration is important in determining the resonance energy levels of the excited state responsible for light emission. Further Evidence for Configurational Changes.-Except for the partial denaturation of the enzyme in acidic buffer, the pH effect on the emission spectrum shift is completely reversible. We have been able to observe these same reversible red shifts in emission spectra by increasing the temperature of the reaction, by carrying out the reaction in 0.2 M urea and at normal pH values (7.6) in glycyl glycine buffer, by adding small concentrations of Zn++, Cd++, and Hg++ cations, as chlorides. The normalized emission spectra of the in vitro bioluminescence of purified Photinus pyralis luciferase for various Zn++ concentrations are shown in Figure 1. The 1.0 .9 .8 FG1.7Nraie msinspcr ftei ir P. pyralis bouiecnea aiu .5 .4 .3 .2 .1 4763 4925 5087 5250 5412 5574 5736 5898 6061 6223 6385 6547 6709 6871 7033 7195 WAVELENGTH (ANGSTROMS) FIG. 1.-Normalized emission spectra of the in vitro P. pyralis bioluminescence at various concentrationsofZn++. (a)Norm~a1,noaddedZn++. (b) 1.33 X 1O4MZn++. (c) 3.95 XIO-4 M Zn+ (d) 2.3 X 10O3 M Zn+ 75Downloaded by guest on July 16, 2020

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An annual, long range, subsurface transport of Prorocentrum mariae‐lebouriae, from the mouth of the Chesapeake Bay to its bloom area in the upper bay, a distance of 240 km, is described and completely documented. Prorocentrum in surface outflowing waters at the mouth of the bay is recruited in late winter into more dense inflowing coastal waters. Strong stratification produced by late winter–early spring surface runoff results in the development of a stable pycnocline. Prorocentrum, now in northward‐flowing bottom waters, is retained in these bottom waters. It accumulates in a subsurface concentration maximum below the pycnocline and is transported northward to reach its bloom area in the Patapsco River and north of the Bay Bridge by late spring. The rapidly decreasing depth of the upper bay causes the pycnocline to rise, mixing the previously light‐limited Prorocentrum and its nutrient‐rich bottom waters to the surface, where rapid growth ensues. Once the dinoflagellate is in surface waters, positive phototaxis, combined with both wind‐ and tide‐driven surface convergences, produce dense surface patches or red tides. Prorocentrum is effectively retained in the bay until late winter by sequential inoculation into the tributary estuaries on the western shore, which exchange relatively slowly with bay waters. By late winter the annual cycle is complete. Prorocentrum is again in surface waters at the mouth of the bay where it is reintroduced into northward‐flowing bottom waters. The mechanisms described provide a key to understanding the origins of subsurface chlorophyll maxima and the delivery of toxic dinoflagellates to coastal bloom areas.

Quantum yields for luminol (3-aminophthalic hydrazide) chemiluminescence reactions fall into two classes depending on oxidizing conditions. In aprotic solvents the quantum yield is high and the excitation yield which allows for the fluorescence quantum yield of the product, is 0.09 and is unaffected by changes in solution temperature or polarity, or the presence of quenchers. In aqueous solution under optimum pH conditions (1 1-13), hydrogen peroxide oxidation results in a high chemiluminescence quantum yield with an excitation yield of 0.04 again unaffected by temperature, viscosity or quenchers. Other oxidizing conditions produce lower quantum yields probably by the introduction of competing chemical pathways.The luminol chemiluminescence light standard has been used to calibrate a spectrofluorometer with results in good agreement with the quantum yields of the femoxalate actinometer and the fluorescence of quinine sulfate and diphenylanthracene.

Dark-active North American fireflies emit green bioluminescence and dusk-active species emit yellow, in general. Yellow light and yellow visual spectral sensitivity may be adaptations to increase the signal-to-noise (that is, foliage-reflected ambient light) ratio for sexual signaling during twilight. The peaks of the electroretinogram visual spectral sensitivities of four species tested, two dark- and two dusk-active, correspond with the peak of their bioluminescent emissions.