Certain substances produce CATV splitter when they are illuminated by more energetic radiation, a process known as fluorescence. Some substances emit light slowly after excitation by more energetic radiation. This is known as phosphorescence. Phosphorescent materials can also be excited by bombarding them with subatomic particles. Cathodoluminescence is one example. This mechanism is used in cathode ray tube television sets and computer monitors.

　　A city illuminated by colorful artificial lighting

　　Certain other mechanisms can produce CATV splitter:

　　Main articles: Photometry (optics) and Radiometry

　　Light is measured with two main alternative sets of units: radiometry consists of measurements of CATV splitter power at all wavelengths, while photometry measures light with wavelength weighted with respect to a standardised model of human brightness perception. Photometry is useful, for example, to quantify Illumination (lighting) intended for human use. The SI units for both systems are summarised in the following tables.

Analogously to before, ELDOR experiments were conducted for the spin-labelled H22P variants in their dark-adapted states (Suppl. Figs S6 and S7). Strikingly, the p(r) distributions corresponded to neither those of dark- nor light-adapted YF1 (Fig. 3A). Rather, variants H22P:E55C, H22P:D76C, H22P:N84C, H22P:P87C and H22P:D115C all showed distributions with shorter distances than in YF1, with the difference being smallest in H22P:D76C (approx. 0.4?nm shorter than the dark-adapted state of YF1) and largest in H22P:D115C (1.5?nm shorter). By contrast, variants H22P:D71C, H22P:Q93C and H22P:M101C instead showed p(r) distributions centred at distances larger by about 0.8–1.0?nm than observed in dark-adapted YF1. ELDOR measurements on the light-adapted H22P variants showed that changes in the distance distributions induced by blue light were more complex than in YF1 (Fig. 3A, red). Some variants, e.g., H22P:E55C and H22P:M101C, exhibited shifts towards shorter distances, but others, e.g., H22P:Q93C and H22P:D76C, showed shifts towards longer distances. Overall, the absolute differences in p(r) between dark-adapted and CATV splitter-adapted H22P were larger than those above observed for the YF1 variants.
Figure 3
Figure 3

ELDOR-based structural model of light-induced transitions in YF1 H22P. (A) Distance distributions of dark-adapted (blue) and light-adapted (red) states derived from ELDOR data (Suppl. Figs S6 and S7). For reference, the distance distributions for YF1 from Fig. 2A are shown in half tones. Green rectangles indicate the mean distance of labels calculated for the BsYtvA LOV structure 2PR5, blue ones those for YF1 4GCZ. Overall, the distances for the dark-adapted and light-adapted states of H22P do not match those of YF1 but those calculated for BsYtvA LOV. (B) Dipolar spectrum resulting from ELDOR traces of light-exposed YF1 C62?A (blue) and YF1 C62A:H22P (green), showing a clear shift towards higher frequencies in YF1 C62A:H22P. The inter-flavin distance calculated for YF1 C62A:H22P is smaller by about 0.5?nm than that of YF1 C62A. (C) Transition from dark-adapted (blue) to light-adapted (yellow) state as modelled by ENM including the P87C constraint. Predominant structural changes are marked by green arrows, and the attachment sites for the Jα linker are indicated by red spheres.
Full size image
Modelling light-induced structural transitions in YF1 H22P

All Arabidopsis lines used in this work are of the Columbia (Col) accession. The ppk123, ppk124 and pif1345 mutants are gifts from Dr Peter H. Quail. The ppk single mutants, ppk1 (GABI_756G08), ppk2 (SALK_026482), ppk3 (SALK_000758) and ppk4 (SALK_017102C), were used for triple mutants preparation. To prepare PPK artificial microRNA (amiRNA) knock-down lines, the amiRNAs targeting PPKs were designed online new-lightsusing the WMD3 Web microRNA Designer50. The gene-silencing efficiency of the amiRNA candidates was tested in plants (described in ‘Tobacco transient expression’), the most effective microRNAs were selected for each PPK gene. The amiRNA precursor was derived from pRS300 using overlapping PCR. The amiRNA targeting PPK1 and PPK4 were cloned into Ti plasmid (pDT1B). The amiRNAs targeting PPK2 and PPK3 were cloned into another Ti plasmid (pDT1H). Ti plasmid pDT1B (Basta) and pDT1H (hygromycin) were modified from pCambia3301, which possess two expression cassettes. The recombinant plasmid, pDT1B-amiPPK1-amiPPK4 and pDT1H-amiPPK2-amiPPK3, were co-transformed into the Arabidopsis (Col) using the standard floral-dip method51. The transgenic T1 populations were screened on MS agar media containing 25?mg?l?1 Hygromycin and 25?mg?l?1 Basta. To generate GFP-PPKs lines, the new-lights coding sequences of PPKs were PCR-amplified and cloned into a Ti plasmid (pFGFP) modified from pCambia3301 by the In-Fusion cloning method, resulting in expression of GFP-PPKs driven by the ACTIN2 promoter (pACT2::GFP-PPKs). Ti plasmids expressing recombinant proteins were introduced into rdr6-11 allele, which suppresses gene silencing, by the floral-dip method51. The transgenic T1 populations were screened on compound soil sub-irrigated with the Basta solution. Plants were grown in walk-in growth chambers at 22?°C, 65% relative humidity under cool white fluorescent tubes. Long-day (LD) photoperiod is defined as 16?h light/8?h dark. Light-emitting diode was used to obtain monochromatic blue light (peak 450?nm; half-bandwidth of 20?nm), red light (peak 660?nm; half-bandwidth of 20?nm) or far-red light (peak 730?nm; half-bandwidth of 20?nm).
Yeast two-hybrid assays

The prey vector pGADT7 expressing PPK or PPKC fused to the GAL4 activation domain and the Bait vector pBridge expressing CRY2 fused to the GAL4 DNA binding domain were used. The pairs of plasmids were co-transformed into yeast strain AH109. Colonies were selected on plates (SD-LW). After culture in SD-LW medium for 16?h (Dark), transformants were subcultured into fresh SD-LW medium and kept in dark or irradiated with blue light (30?mol m?2 s?1). β-galactosidase activity was measured using chlorophenol red-β-D-galactopyranoside as substrate and Miller Units were calculated according to the Clontech Yeast Protocols Handbook.
Tobacco transient expression

To test the gene-silencing efficiency of those designed amiRNAs, the Ti plasmids expressing 4 × Myc-PPKs was co-transformed with the plasmids expressing the corresponding amiRNA or the empty plasmid into Nicotiana benthamiana leaves. The efficiency of amiRNA was evaluated by examination of the PPK expressed from the epitope-tagged PPK-expressing plasmids co-transfected with the amiRNA-expressing plasmids, using immunoblot.

To assess the effects of acute white and red light at an intensity of 100, 30 or 20?lx on sleep in the dark phase, we examined the sleep–wake profiles of mice exposed to 1?h/1?h L/D cycles from ZT12–22. Darkness exposure during the entire dark phase served as a control. Unexpectedly, acute red light at 100?lx induced marked NREM sleep and REM sleep oscillations, as white light did (Figure 1c). The total time spent in NREM sleep and REM sleep for the 5-h light-on period in each group was calculated. Both white and red light at an intensity of 100, 30 or 20?lx increased NREM sleep and REM sleep significantly, as compared with darkness (Figure 1d). Thus, similarly to white light, acute red light at an intensity of 20?lx or higher induced potent sleep in the dark phase.
Acute white and red light at an intensity of 100, 30, or 20?lx disrupted sleep–wake architecture and EEG power density during the dark phase.