Light scattering,chlorophyll fluorescence and state of the adenylate system in illuminated spinach leaves

Scattering of green light and chlorophyll fluorescence by spinach leaves kept in a stream of air or nitrogen were compared with leaf adenylate levels during illumination with blue, red or far-red light. Energy charge and ATP-ADP ratios exhibited considerable variability in different leaves both in the dark and in the light. Variability is explained by different possible states of the reaction oxidizing triose phosphate or reducing 3-phosphoglycerate. Except when oxygen levels were low, there was an inverse relationship between light scattering and chlorophyll fluorescence during illumination with blue or red light. When CO₂ was added to a stream of CO₂-free air, chlorophyll fluorescence increased, sometimes after a transient decrease, and both light scattering and leaf $\text{ATP}\text{ADP}$ ratios decreased. Similar observations were made when air was replaced by nitrogen under blue or high-intensity red light. Under these conditions, over-reduction caused inhibition of electron transport and phosphorylation in chloroplasts. However, when air was replaced by nitrogen during illumination with low-intensity red light or far-red light, light scattering increased instead of decreasing. Under these light conditions, $\text{ATP}\text{ADP}$ ratios were maintained in the light. They decreased drastically only after darkening. Although $\text{ATP}\text{ADP}$ ratios responded faster than light scattering or the slow secondary decline of chlorophyll fluorescence due to illumination, it appeared that in the steady state, light scattering and chlorophyll fluorescence are useful indicators of the phosphorylation state of the leaf adenylate system at least under aerobic conditions, when chloroplast and extrachloroplast adenylate systems can effectively communicate.     

Photoreceptor pigment for blue light responses in Neurospora crassa

Irradiating the mycelium of $\text{Neurospora crassa}$ with blue light causes the photoreduction of a $\text{b}$-type cytochrome. The action spectrum for the photoreduction of the cytochrome $\text{b}$ is similar to action spectra for the photoactivation of carotene synthesis and photoinhibition of the circadian rhythm of conidiation in $\text{Neurospora}$.     

Activation of Phycomyces adenosine 3', 5'-monophosphate phosphodiesterase by blue light.

Cyclic AMP phosphodiesterase can be extracted from sporangiophores of $\text{Phycomyces}\text{blakesleeanus}$. Activity is enhanced by 1–10 μM FAD and FMN but not by riboflavin. Moderate intensity of blue light also activates the enzyme, especially in the presence of 1mM GTP. The enzyme must be extracted and stored in the absence of blue light for this result. Forty times the intensity of red light has no effect. This finding is consistent with the very sudden transient drop in cyclic AMP level upon light stimulation in the intact sporangiophore.     

Internalization and degradation of a low affinity insulin ([LeuB24]insulin) by rat adipocytes

In Halobacterium halobium tactic responses towards light and chemoeffectors are accompanied by changes in the methylation level of methyl-accepting chemotaxis proteins (MCP). Taxis towards green light absorbed by the bacteriorhodopsin proton pump appears to be governed by Δ$\text{μ}$_H⁺-sensing. The addition of CCCP, an uncoupler, prevented the increase of MCP methylation in response to green light illumination, but had no effect on CH₃-incorporation followed by the addition of the attractants glucose, leucine and histidine. Similarly, CCCP did not change MCP demethylation in response to blue light illumination, a repelling stimuli.The sensitivity to an uncoupler of methylation linked to Δ$\text{μ}$_H⁺-mediated green light taxis is to be expected, while the independence of demethylation caused by the blue light of CCCP is an indication that in the latter case a specific photoreceptor governs phototaxis. Informed processing from the blue light receptor to MCP does not involve a change in the membrane potential.     

Effect of light quality on the composition and function of thylakoid membranes in atriplex triangularis

Light quality was shown to exert well-coordinated regulatory effects on the composition and function of the thylakoid membranes as well as on the photosynthetic rates of intact leaves from Atriplex triangularis grown in continuous blue, white and red lights (50 μE · m^?2 · s^?1). The higher photosynthetic rates in plants grown in blue light, as compared to those in white and red lights, resulted from marked changes in both light-harvesting complexes and electron carriers. The concentrations of electron carriers such as atrazine binding sites, plastoquinone, cytochromes b and f and P-700 on a chlorophyll basis were markedly increased in Atriplex grown in blue light; and the apparent light-harvesting antenna unit sizes of Photosystems I and II were greatly reduced. Consequently, the electron transport capacities of Photosystems I and II were also increased as was the coupling factor CF₁ activity. Atriplex grown in red light had lower photosynthetic rates than those grown in blue or white light by incorporating changes in the composition and function of the thylakoids in a direction opposite to those caused by growth in blue light. When these regulatory effects of light quality were compared with those of light quantity [6,7], it is clear that $\text{Chl}\text{a}\text{Chl}\text{b}$ ratios, electron transport capacities of Photosystems I and II, concentrations of plastoquinone, atrazine binding sites, coupling factor CF₁ activity and the apparent antenna unit size of Photosystem II are more affected by light quantity, whereas light quality has a greater influence on the concentration of P-700, the apparent antenna unit size of Photosystem I and the overall photosynthetic rates of intact leaves.     

Separation of a blue fluorescence protein from bacterial luciferase

Luciferase preparations from two species of marine bioluminescent bacteria, $\text{Photobacterium phosphoreum}$ and $\text{Photobacterium fischeri}$, are shown to contain a low molecular weight protein, containing a blue fluorescence chromophore having an emission maximum in the 470 nm region. A procedure for separating the luciferase and purifying this protein is described. On disc gel electrophoresis the bulk of the protein is observed to migrate along with the blue fluorescence.     

Structural studies of monoclonal human cryoprecipitable immunoglobulins

The light chain type, immunoglobulin class and when possible, heavy chain subclass of eleven monoclonal human cryoglobulins were correlated with the variable region subgroup of their light chains. The variable region subgroups were assigned by determining the primary amino acid sequence for the first 15 amino-terminal residues of these light chains. $\text{5}\text{5}$ IgM cryoglobulins which react with human IgG had light chains of the variable region-III kappa chain subgroup (vK-III). $\text{4}\text{4}$ IgG and $\text{2}\text{2}$ IgM cryoglobulins with undefined antibody specificity had both lambda and kappa light chains none of which were vK-III. The data support the concept that there is marked restriction of the IgM anti-IgG antibody response to the IgG auto-antigen.     

Cytochrome P-450 and drug metabolism in intestinal villous and crypt cells of rats: effect of dietary iron.

The amino acid sequence of the $\text{Spirulina maxima}$ ferredoxin has been determined. $\text{Spirulina maxima}$ is a blue green algae and is a procaryote. The ferredoxins of the plant-algal type sequenced to date have all been isolated from eucaryotes. The $\text{S. maxima}$ ferredoxin was composed of 98 amino acids arranged in a single polypeptide chain.The sequences of the various procaryote-eucaryote ferredoxins are compared and the differences discussed.     

Keypeck conditioning with reinforcements in two different locations in thrush,tit and sparrow species

Twenty-one individuals each of the species great tits $\text{(Parus major),}$ blue tits $\text{(Parus caeruleus),}$ marsh tits $\text{(Parus palustris),}$ blackbirds $\text{(Turdus merula),}$ songthrushes $\text{(Turdus philomelos),}$ tree sparrows $\text{(Passer montanus)}$ and house sparrows $\text{(Passer domesticus)}$ were conditioned to a keypeck response by means of food reinforcement. The site where the reward was given was then changed. The number of reinforcements were then counted until the keypeck response followed immediately (within 10 seconds) on three successive occasions, and a comparison was made between species. Of the species studied the blackbird needed significantly fewer instances of reinforcement in order to re-establish an immediate keypeck response. A significant difference was also seen between the performance of the great tit and marsh tit, as well as between the blue tit and the marsh tit. No significant difference was found between the performance of the house sparrow and the tree sparrow.     

Crystals of a functional 70,000 molecular weight subunit of hemocyanin from Limulus polyphemus

Crystals have been obtained of a subunit of Limulus polyphemus hemocyanin. The blue crystals have the symmetry of the space group R32 with hexagonal lattice parameters $\text{a = 115}\text{a}\text{?}$, $\text{c = 285}\text{A}\text{?}$. There is one 70,000 molecular weight subunit per asymmetric unit. Each subunit contains two non-heme copper atoms and can reversibly bind one oxygen molecule.     

The effects of environmental factors on growth and the chemical and biochemical composition of marine diatoms. I. Light and temperature effects

Temperature and light interact to modify the chemical and biochemical composition of a nitrogen-limited marine diatom, Thalassiosira allenii Takano, grown at a constant dilution rate in continuous culture and under a light:dark cycle.The percent of the total ¹⁴C incorporated into protein, polysaccharide and lipid, the N/C ratio and the C/cell varied with temperature in a markedly non-linear manner. The N/cell was negatively correlated to temperature. The Chl $\text{a}\text{C}$ ratio was positively correlated with temperature under saturating light and non-saturating light for temperatures > 25 °C, but was constant under non-saturating light conditions for temperatures < 25 °C.Productivity index (PI) was negatively correlated to temperature under saturating light conditions, but did not vary under low light. In each case, the variation in PI with temperature was governed by the variation in Chl $\text{a}\text{C}$.The dark carbon loss rate was exponentially related to temperature and independent of light. Variation in the percent of the total ¹⁴C incorporated into protein and polysaccharide, the $\text{N}\text{C}$ ratio and C/cell was primarily due to the effects of N-limitation < 20 °C and primarily due to the effects of temperature > 20 °C. Variation in N/cell was primarily due to the effects of temperature over the entire range of temperature studied. Variation in Chl $\text{a}\text{C}$ was caused by the interaction of temperature and light effects.In most cases, temperature and nutrient effects interacted to govern how a particular parameter varied with temperature while light affected the range of values over which the parameter varied.The percent of the total ¹⁴C incorporated into protein exhibited a significant linear relationship with $\text{N}\text{C}$.The dark carbon loss rate, $\text{N}\text{C}$ ratio and Chl $\text{a}\text{C}$ ratio data were used to test the applicability of a model for the physiological adaptation of unicellular algae. The model, with parameters derived from a non-linear least-squares fit of the dark carbon loss rate data, adequately described the $\text{N}\text{C}$ ratio between 15 and 25 °C at 290 and 137 μE · m^?2 · s^?1, but failed to describe the data at 28 °C and at 48 μE · m^?2 · s^?1. The Chl $\text{a}\text{C}$ ratio was adequately described by the model under all light and temperature conditions.     

Electrophoretically homogeneous myeloma light chain mRNA and its translation in vitro

mRNA coding for the light chain of a myeloma protein has been purified to give one band in acrylamide gel electrophoresis. This pure RNA (S～13.5) could be translated $\text{in}\text{vitro}$ into the light chain in a heterologous cell-free translation system. The light chain synthesized $\text{in vitro}$ is apparently slightly larger than the light chain secreted by the tumor.     

The effect of visible light on the regeneration of rhodopsin

Both $\text{in}\text{vitro}$ and $\text{in}\text{vivo}$, increased exposure to visible light decreases the regenerability of the visual pigment. Isolated opsin irradiated with increasing periods of white light decreased in pigment formation yields on combination with 9- or 11-$\text{cis}$ retinal. The yield of regeneration of the visual pigment extracted from albino rats depended on the amount of light to which the animal had been exposed. Animals exposed to normal room light demonstrated lower regeneration yields than dark-reared animals, but these yields increased on dark adaption. Opsin from animals exposed to sunlamps did not regenerate any pigment. On dark adaption, the pigment yields increased but the opsin level remained below that for the control group.     

Light scattering and quenching of 9-aminoacridine fluorescence as indicators of the phosphorylation state of the adenylate system in intact spinach chloroplasts

Upon illumination of suspensions of intact chloroplasts, fluorescence of 9-aminoacridine was quenched, light scattering was increased, chlorophyll fluorescence was decreased after an initial increase, and chloroplast $\text{ATP}\text{ADP}$ ratios were increased. The response of 9-aminoacridine fluorescence quenching and light scattering to light intensity, anaerobiosis and inhibition of electron transport by DCMU was similar to that shown by chloroplast $\text{ATP}\text{ADP}$ ratios. It is discussed under what conditions 9-aminoacridine fluorescence quenching or light scattering can be used to monitor changes in the phosphorylation state of the chloroplast adenylate system.     

NADPH dependent epoxidation of methyl farnesoate to juvenile hormone in the cockroach Blaberus giganteus L.

Corpora allata and corpora allata homogenates from the cockroach $\text{Blaberus giganteus}$ are able to convert tritium labeled $\text{trans, trans}$-methyl farnesoate into insect juvenile hormone III. The epoxidation appears to be enzymatic occurring largely in the 100,000 g precipitate or microsomal fraction of corpora allata homogenates. The epoxidation is NADPH dependent, requires molecular oxygen and is inhibited by carbon monoxide, methylene blue, SKF 525A, and piperonyl butoxide.     

Myosin light chain phosphorylation and phosphorylase A activity in rat extensor digitorum longus muscle.

Phosphorylation of the 18,500 dalton light chain of myosin and conversion of phosphorylase $\text{b}$ to $\text{a}$ were examined in relation to isometric tension development. Following a l sec tetanic contraction, light chain phosphate content increased from a pre-tetanic value of 0.10 to 0.75 mol phosphate/mol at 7 sec; phosphorylase $\text{a}$ activity (ratio of activity $\text{?5′AMP}\text{+5′AMP}$) increased from 0.03 to 0.42 at 4 sec and decreased to control values within 20 sec. Light chain phosphate content, however, declined much more slowly and correlated to post-tetanic potentiation of peak twitch tension. Our results suggest light chain phosphorylation is not obligatory for contraction but may play a role in post-tetanic potentiation.     

Transport as the basis of the kok effect. Levels of some photosynthetic intermediates and activation of light-regulated enzymes during photosynthesis of chloroplasts and green leaf protoplasts

Experiments were performed with intact chloroplasts and leaf cell protoplasts isolated from spinach. The light-dependent decrease in (H⁺) in the chloroplast stroma counteracts carbon reduction and is offset at low light intensities by a large decrease in NADP and a significant increase in $\text{[}\text{ATP}\text{]}\text{[}\text{ADP}\text{]}$ ratios. Excess accumulation of NADPH and/or ATP permits 3-phosphogly cerate reduction to occur. With increasing light intensity, NADP levels and $\text{[}\text{ATP}\text{]}\text{[}\text{ADP}\text{]}$ ratios increased. High rates of photosynthesis were observed at high and at low $\text{[}\text{ATP}\text{]}\text{[}\text{ADP}\text{]}$ ratios. Levels of dihydroxyacetone phosphate were dramatically increased in the light. In chloroplasts, this permitted conversion to ribulose bisphosphate which on carboxylation yields 3-phosphoglycerate. The light-dependent alkalization of the chloroplast stroma is known to be responsible for phosphogly cerate retention in the chloroplasts. A high chloroplast ratio of phosphogly cerate to dihydroxyacetone phosphate aids carbon reduction. Measured ratios of dihydroxyacetone phosphate to phosphogly cerate were averages between low chloroplast ratios and high cytosolic ratios. They were far higher, even under low-intensity illumination, than dark ratios. Since cytosolic NADH levels are known to increase much less in the light than cytosolic dihydroxyacetone phosphate levels, the large increase in the ratio of didydroxyacetone phosphate to phosphogly cerate must considerably increase cytosolic phosphorylation potentials even at very low light intensities. It is proposed that this increase is communicated to the mitochondrial adenylate system, and inhibits dark respiratory activity, giving rise to the Kok effect. The extent of stroma alkalization, the efficiency of metabolite shuttles across the chloroplast envelope, and rates of cytosolic ATP consumption are proposed to be factors determining whether and to what extent the Kok effect can be observed. Light activation of chloroplast enzymes was slow at low and fast at high light intensities. This contrasts to low NADP levels at low and usually higher levels at high light intensities. Maximum enzyme activation was observed far below light saturation of photosynthesis, and light activation of enzymes was often less pronounced at very high than at intermediate light intensities.     

A constitutive flavodoxin from a eukaryotic alga

We report the isolation and some properties of a flavodoxin from a eukaryotic organism, the naturally occurring red alga $\text{Chondrus crispus}$. Unlike the situation with most other organisms the flavodoxin, under normal growth conditions, is the predominantly formed low-potential electron carrier, an accompanying ferredoxin occurring in only very small amounts. The flavodoxin is of molecular weight 21000 and one mole of FMN is present per mole of protein. Reduction of the flavoprotein proceeds via a blue flavosemiquinone radical. The flavodoxin is active both in photosynthetic NADP reduction by broken chloroplasts, and in phosphoroclastic cleavage of pyruvate by cell-free extracts of $\text{Clostridium pasteurianum}$.     

A sensitive assay for proteins and biliproteins

An assay for proteins in dilute solution is described which is based on binding of Coomassie blue G-250 to proteins. The dye-protein complex formed is separated out from solution by centrifugation. The absorbance of the redissolved precipitate in 70:30 ($\text{v}\text{v}$) Tris:methanol is monitored at 605 nm. The assay is standardized for biliprotein determination.     

The early synthesis and possible function of a 0.5 X 10(6) Mr RNA after transfer of dark-grown Spirodela plants to light.

A 0.5 × 10⁶$\text{M}$_r RNA found in plastids of the aquatic angiosperm $\text{Spirodela}$, is synthesized at a much higher rate than any other rapidly labeling RNA species about $\text{3–3}\text{1}\text{2}$ h after dark-grown plants are transferred to light. The pulse labeling kinetics of the 0.5 × 10⁶$\text{M}$_r RNA after transfer to light, argue against its involvement in the biogenesis of plant rRNAs. Although poly(A) RNA is found in $\text{Spirodela}$, poly(A) sequences are not detected in the 0.5 × 10⁶$\text{M}$_r RNA; yet a sucrose gradient fraction which includes RNA of this $\text{M}$_r stimulates amino acid incorporation by an $\text{E. coli}$ cell free extract more than other RNA fractions. The possible involvement of the 0.5 × 10⁶$\text{M}$_r RNA as a chloroplast messenger is discussed.